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THE
PHYSIOLOGICAL ANATOMY
PHYSIOLOGY  OF MAN. 
 
THE
PHYSIOLOGICAL ANATOMY
PHYSIOLOGY  OF  MAN.
BY
     ROBERT BENTLEY TODD, M.D., F.R.S.,
   FELLOW OF THE COLLEGE OF PHYSICIANS, AND 1'b ISICIAN TO KINO'S COLLEGE HOSPITAL \

                  AND


        WILLIAM BOWMAN, F.R.S.,
   FELLOW OF THE COLLEGE OF SURGEONS, SURGEON TO KING'S COLLEGE HOSPITAL AND THE
            ROYAL LONDON OPHTHALMIC HOSPITAL ;

  LATE PROFESSORS OF PHYSIOLOGY AND GENERAL AND MORBID ANATOMY IN
             KING'S COLLEGE, LONDON.



        COMPLETE IN  ONE VOLUME.



WITH TV/O HUNDRED AND NINETY-EIG-HT ILLUSTRATIONS
x"
GEON GENERAL.';
'M,
^-■ffeC
1837
/irpl
       PHILADELPHIA:
BLANCHARD  AND  LEA.
            1857.
 
qr
T/p3£p
    PHILADELPHIA:

T. K. AND P. 0. COLLINS, PEINTEE8. 
TO
  SIR BENJAMIN  COLLINS BRODIE, BART.,
                 D.C.L, F.B.S., ETC. ETC.,
        CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE,
               SERGEANT SURGEON TO THE QUEEN,


                    WHOSE MIND,


EARLY TRAINED IN  PHYSIOLOGICAL RESEARCHES,


                  HAS BEEN DEVOTED


     THROUGH A LONG LIFE OF EMINENT USEFULNESS


          TO THE PRACTICE AND IMPROVEMENT


               OF THE HEALING ART,
is Math n  Sh&itattb
THE AUTHORS. 
I 
PEEEACE.
   The work, which is now brought to a conclusion, was commenced
in the year 1843, having been designed as a text-book for  the lec-
tures on  General Anatomy and Physiology, given in King's  College,
London.
   In its  title, we adopted the term Physiological Anatomy, in pre-
ference to the older one of G-eneral, or the later one of Histological,
as being  more comprehensive than either, and as denoting precisely
that kind of anatomy, a  knowledge of which is  especially required
for the investigation  of those subjects which  ought to come under
consideration in a Physiological course.
   We proposed to ourselves to give  such a view of the main facts
and  doctrines of  Anatomy and  Physiology,  particularly of  those
bearing on practical Medicine and  Surgery, as might suffice for the
wants of the student and practitioner.  Following that  great master,
Haller, we were desirous of giving  to Anatomy a greater degree of
prominence than had been usual in  Physiological works, under  the
conviction that a thorough training in its several branches,  descrip-
tive, physiological, and comparative, is necessary to the formation of
those habits of mind which best fit their possessor for the successful
investigation and the correct  appreciation of  physiological  science.
And we  aimed  at resting our anatomical descriptions, at  least  as
regards the more important points, upon our own investigations, and 
Viii                        PREFACE.
at repeating former experiments,  or  devising new ones, whenever
questions of sufficient interest presented themselves.
  While we must humbly confess how small have been the advances
attributable to our own labours,  the immense extension given to the
sciences of Anatomy and Physiology during the  last fifteen years,
may be admitted as some explanation of the delay that has occurred
in the publication of our work, a delay that has been  a constant
source of regret to us, since we began to discover how impossible it
would be for us to complete it within the term  originally contem-
plated.  That, in spite of repeated procrastination, it should have
been so favourably received, both at home and abroad, has been  the
greatest  encouragement  to us,  and  demands our  most thankful
acknowledgments.   If, indeed, our pursuits had  tended to no  other
end  than  the cultivation of science,  this book might  have been
finished long ago;  but the increasing interruptions  incident to a
professional life, and the large demand made on  us by studies of a
practical kind,  began at an early period to impede our progress.
These  hindrances  did not diminish as time wore on, nor were they
lessened by the fact of the authorship being  in  the hands of two
persons, however  cordially united by common views  and the ties of
friendship,  or by the necessity for frequent and  prolonged  confer-
ences which that double authorship entailed.
  Such is the apology we have to offer for the tardy completion of
our work.   It will, we  doubt not, be  fully appreciated by candid
men who know by experience  how multifarious are  the  calls  made
upon those  who not only are candidates for professional employment
in London, but  hold also the responsible position of public teachers
in a large School and  Hospital.
  Were it not, indeed, for the kind and valuable  co-operation of Dr.
Beale, who is now the sole occupant of the physiological chair  in
King's College, we should not  even yet have been released from  our 
                            PREFACE.                          IX
difficulties.  Dr. Beale, knowing  all our views, and having worked
with us on many points, has given us very important assistance in
drawing  up the concluding  chapters of  the work.   Our warmest
thanks are due to our friend and  colleague for the patient industry
and  admirable judgment,  with which,  stepping out of his  proper
path of independent investigation, he has carried out our intentions,
and  enabled us, although at the eleventh hour, to fulfil our  engage-
ment to our pupils and to the public.
   To our friend Dr. H. Hyde Salter we  are  indebted for  several
excellent drawings, as well as for other valuable assistance.
   We desire also to  express our  thanks to Mr. Vasey for the skill
and  ability with which he has executed his portion of  the task, that
of engraving the drawings on wood.

                                          W. B.---R. B. T.
London, December 1, 1856. 
 
CONTENTS.
INTRODUCTION.
Remarks on the method of study, 25.
Organized and unorganized bodies, 27.
Active and dormant life, 27-8.
Chemical  constitution of unorganized
  bodies, 28.
Ditto of organized bodies, 29.
Their essential and incidental elements,
  29._
Proximate principles, 29.
Secondary organic compounds, 30.
Complex structure of  organized bodies,
  32.
Primary organic cell, 32.
Form, duration, and mode of origin of
  organized bodies, 32.
Spontaneous generation, 33.
Reproduction, 33.
Assimilation, 34.
Excretion, 34.
Decomposition,  34.
Life, 35.
Vital stimuli, 36.
Fluid and Solid constituents of animal
  bodies, 51.
Table of proximate principles, and of
  secondary organic compounds, 52.
Proximate principles, 53.
Albumen, 53.
Fibrine, 54.
Caseine, 55.
Proteine, 56.
Vegetable albumen, fibrine, and case-
  ine, 56.
Gelatine, 57.
Chondrine, 58.
Fatty principles, 59.
Importance of a mixed diet, 59.
Secondary organic compounds,  60.
Classification and properties of the tis-
  sues, 61.
Vital properties, 36.
Death, 36.
Theories of life, of Aristotle, of Harvey,
  and of Hunter, 37.
Of Mliller, of Dr. Prout, 38.
Functions of Animals and Plants, 42.
Organic,  42.
Animal, 45.
Volition, 45.
Sensation, 45.
The Mind, 46.
Instinct,  46.
Importance of Physiology to Medicine,
  47.
Mode of conducting Physiological inqui-
  ries, 49.
Value of Anatomy, human and compa-
  rative, 49 ; of Experiment on living
  animals, 49 ; of Pathology, 50; of the
  Microscope, 50;  of organic Chemis-
  try, 51.
Development of the tissues from cells,
  63.
The ovum a nucleated cell, 63.
The  nucleus and  cell-wall, probably
  both share in development, 63.
Properties of the tissues, 65.
Physical, 65.
Elasticity, extensibility, porosity, 66.
Endosmose, 67.
Vital, 68.
Contractility, 68.
Nervous force, 68.
Common sensation, 69.
Special sensation, 69.
These properties dependent on nutri-
  tion, 69.
                           CHAPTER I.


OF THE CONSTITUENTS OF ANIMAL BODIES.--THE TISSUES  AND THEIR
                            PROPERTIES. 
Xll                            CONTENTS.


                            CHAPTER  II.

         OF THE MINUTE MOVEMENTS  OCCURRING IN THE BODY.

Molecular motion of Robert Brown, 71. Circumstances affecting their motion,
Organic molecular motion, 71.             74.
Molecular changes in nerve and mus- Surfaces on which they exist in man,
  cle, 72.                               75.
Ciliary motion, 73.                    Cause of ciliary motion, 77.
Structure of the cilia, 73.             Motions of Spermatozoa, 77.

                            CHAPTER  III.
!TS PASSIVE ORGANS.
                 OF LOCOMOTION.—I

Locomotion peculiar to animals, 78.
Movements included in the term, 78.
Passive and active organs, 78.
Of the Fibrous tissue, 78.
White fibrous tissue, 79 ; its forms and
  structure, 79; physical and vital pro-
  perties, 80;  chemical  constitution,
  80.
Ligaments and their varieties, 80.
Tendons, 81.
Fasciae, 81.
Reparation of white fibrous tissue, 82.
  Yellow fibrous tissue, its forms and
  structure, 82; chemical constitution,
  83.
Areolar tissue, 83.
White and yellow fibrous elements, 84;
Of Cartilage, temporary  and perma-
  nent, 95,
Physical characters, 96.
Simple cellular cartilage, 96.
Temporary, 96.
Articular,  97.
Costal, 97.
Membraniform, 98.
Perichondrium, 98.
Vessels of cartilage, 99.
              PASSIVE ORGANS OF LC

External and internal skeletons, 102.
Bone, 102.
Physical properties, 103.
Animal and earthy constituents, 103.
Researches of Dr. John  Davy and Dr.
  G. O. Rees  on their relative propor-
  tions in different bones, 104.
Rickets, mollities, 104-5.
  development, 85;  distribution in the
  body, 86;  modifications  of its  ele-
  ments, 87;  physical properties, 88.
Of the Adipose tissue, 88.
Fat-vesicles, 89; their bloodvessels, 90.
Otfat, 90.
Proximal constitution, 91.
Spontaneous  separation of  the marga-
  rine and elaine within the vesicles,
  91.
Ultimate analysis, 91.
Distribution of the  adipose tissue in
  the animal  kingdom, 91; in the hu-
  man body, 92.
Development, 93.
Source of fat, Liebig's views,  94.
Uses of fat, 94.
Articular cartilage not penetrated by
  vessels, 99.
Mr. Toynbee's observations, 99.
Fibro-cartilage, articular and non-ar-
  ticular, 100.
Its  properties, vessels, chemical com-
  position,  and varieties, 100.
Intervertebral discs, and menisci, 101.
Reparation, 102.
Bone resists decomposition, 105.
Analysis of the animal and earthy parts,

Compact and cancellated forms of osse-
  ous tissue, 106.
Periosteum, medullary membrane, me-
  dulla, medullary canal, 107.
Long bones, 107.
              CHAPTER  IV.

PASSIVE ORGANS OF LOCOMOTION, CONTINUED.
CHAPTER  V.
COMOTION, CONTINUED. 
CONTENTS.
xiii
Flat bones, 108.
Irregular bones, 109.
Eminences and depressions of bones,
  109.
Vessels, 109.
Haversian canals, 110.
Veins of bones, 110.
Mr.  Tomes'  observations on  the ulti-
  mate  structure of the osseous tissue,
  111.
Lacunce and canaliculi, or pores, of the
  osseous tissue, 112.
Their varieties, 113 ;  usual  shape and
  size, 114.
Laminated texture of bone, 114.
Synovial membranes of joints, 126.
Bursse, 127.
Synovial sheaths, 127.
Synovia, 128.
Serous membranes, 128.
Minute structure of synovial and serous
  membranes, 129.
Physical and vital properties, 130.
Of the Joints, 130.
Accessory structure, 131.
Influence of atmospheric pressure on the
  joints,  131.
Of the forms and classification of joints,
  131.
Synarthrosis, Suture, 132.
Of Muscle in general, 146.
Of the striped fibres, 146.
Size and shape, 147.
Internal structure, 147.
Sarcous elements, 148.
Sarcolemma, 150.
Attachment of tendon, 152.
Development, 152.
Growth,  153.
Of the unstriped fibres, 153.
Size, shape, and structure, 154.
Distribution of the striped and unstriped
  fibres in the body, 155.
Dartos,  155.
Distribution in the animal series, 15b.
Arrangement of fibres in voluntary mus-
  cles, 157.           .
Arrangement of tendon in muscles, 157.
Origin and insertion, 158.
Outer,  inner, and Haversian  surfaces
  of a long bone, 114.
Periosteal, medullary,  and Haversian
  layers, or systems of lamella?, 114.
Arrangement of the lacunae and pores
  with  regard to the vascular surface
  of bone, 116.
Lamellae, 116.
Development of bone,  118.
Centres of ossification, 118.
Process of ossification  traced  through
  its stages, 119.
Growth of bone, 122.
Experiments with madder, 123.
Reparation of bone, 125.
Schindylesis,  Gomphosis,  Amphiar-
  throsis, 133.
Diathrosis, 133.
Various motions of joints, 134.
Arthrodia, Enarthrosis, 134-5.
Ginglymus, Diarthrosis rotatorius, 135—
  136.
Mechanism of the Skeleton, 136.
Cranium, 136.
Spine, 137.
Pelvis, 139.
Thorax, 140.
Pelvis and thorax compared, 140.
Lower extremities, 141.
Upper extremities, 143.
The hand, 145.
Arrangement  of fibres in the hollow
  muscles, 158.
Areolar tissue of muscles, 159.
Bloodvessels, 159.
Nerves, 160.
Antagonism of muscles, 162.
Arrangement of muscles on the Skeleton,
  162.
Contractility,  elasticity, and tenacity
  of muscle, 163.
Passive contraction, 164.
Tonicity, 164.
Active contraction, muscular  fatigue,
  164.
Stimuli of muscle, nervous and physi-
  cal, 165.
Contraction caused by a physical stimu-
  lus applied  to the  isolated sarcous
  tissue, 166.
               CHAPTER VI.

PASSIVE ORGANS OF LOCOMOTION, CONTINUED.
      CHAPTER VII.

ACTIVE ORGANS OF LOCOMOTION. 
xiv
CONTENTS.
Contractility a property  of the sarcous
  tissue, 166.
A muscle not smaller during contrac-
  tion, but shorter and thicker,  167.
The same true of the sarcous tissue, 168.
Minute movements in passive and active
  contraction, 170; as exhibited in te-
  tanic muscle, 173.
Muscular sound, 173.
Heat developed during contraction, 174.
Varieties of contraction, 175.
Zigzags explained, 175.
Schwann's experiment, 176.
Character of  contractility varies  with
  nutrition, 177.
Examples of Nervous actions, 187.
Connection of nervous actions with the
  mind, 188.
Physical nervous actions, 190.
Nervous matter, 191.
Elements of the nervous system, 192.
Properties of nervous matter, 192.
Tubular fibre, 193 ; tubular membrane,
  white substance,  and axis-cylinder,
  194 ; varicosities, size, 196.
Gelatinous fibre, 196.
Vesicular nervous matter, 197.
Ganglion-globules, 197.
Caudate vesicles, 198.
Connection of the fibrous with the vesicu-
  lar matter,  199.
Nervous system in vertebrata, 225 ;  in
  invertebrata, 22G.
Meninges ; Dura mater, its processes,
  227 ;  arteries and sinuses, 229.
The  arachnoid, and sub-arachnoid ca-
  vity, 230.
Cerebro-spinal fluid, 231.
Analogy to fibrine of blood, 178.
Rigor mortis, 179.
Muscular sense, 179.
Action of the sphincters, 180.
Peristaltic contraction, 180.
Rhythmical contractions, 182.
Association of movements, 182.
The attitudes of man, 183.
Power of volition and emotion over tho
  muscles, 185.
Reflex movements, 186.
Instinctive movements, 186.
Mechanical or habitual movements, 186.
Nerves, 200.
Cerebro-spinal, 200.
Neurilemma, bloodvessels, 200.
Origin, branching, 200-1.
Anastomosis, 201.
Plexuses, 203.
Termination of nerves, 204.
Ganglionic  nerves, 205 ;  their  union
  with the spinal, 205.
Nervous centres, 207.
Coverings, 207.
Minute structure, 207.
Nerves and nervous centres  of inverte-
  brata, 209.
Development of nerve-fibres, 209.
Regeneration of nervous matter, 211.
Pia mater, 232.
Ligamentum dentatum, 232.
Pacchionian glands, 233.
Anatomy of the Spinal cord, 233.
Arrangement of gray and white matter.
  235.
Minute anatomy of the cord, 236.
CHAPTER  VIII.

  INNERVATION.
CHAPTER  IX.
INNERVATION, CONTINUED.
Polarity op nerves, 212.
Endowments of nerve-fibres, motor, sen-
  sitive, and excitor, 212-13.
Common and special sensation, 214.
Subjective phenomena, 214.
Stimuli of nerves, mental and physical,
  215.
Nerves not passive conductors, 216.
The nervous force, 217.
Nervous and electrical forces compared,
  218.
The nervous force not electricity, 223.
Animal electricity  and  luminousness,
  224.
      CHAPTER X.

INNERVATION, CONTINUED. 
CONTENTS.
XV
Four classes of fibres, 237.
Of the Encephalon, 237.
Subdivisions, 237.
Weight of the brain in animals and man,
  237-8.
Connection of the mind with the brain,
  238.
Medulla oblongata, 239.
Anterior pyramids, 240.
Arciform fibres, 241.
Decussation of the anterior pyramids,
  241.
Restiform bodies, 242.
Posterior pyramids,  242.
Olivary bodies, 242.
Stilling and Wallach's  researches on
  the med. oblong.,  244.
Cerebellum, 245.
Hemispheres, median lobe, and vermi-
  form processes, 245.
Crura cerebelli, 246.
Intimate structure, 247.
Fourth ventricle, 248.
Mesocephale, 248.
Pons Varolii,  249.
Quadrigeminal bodies, 249.
Processus cerebelli ad cerebrum, 250.
Cerebrum, 250.
Optic thalamus and corpus  striatum,
  250.
Pineal gland, 252.
Middle and posterior commissures, 252,
Cerebral hemispheres, 253.
Convolutions, 253.
Regular  convolutions, observations of
  Leuret, 254.
Varieties of the convolutions, 255 ; their
  structure, 256.
Commissures of  the cerebrum,  trans-
  verse and longitudinal, 257.
Septum lucidum and  fifth  ventricle,
  260.
Pituitary body, 261.
Third and lateral ventricles, 261.
Lining membrane of the ventricles, 262.
General view of the course of nervous
  power in the brain, 262.
Circidation in the brain, arteries, 263.
Consequence of obstruction, 265.
Conservative provisions, 266.
Capillaries,  266.
Veins, 266.
Brain subject to atmospheric pressure,
  267.
Brain compressible, 268.
Practical inferences, 269.
CHAPTER XI.
INNERVATION, CONTINUED
Of the Cerebro-spinal nerves in gene-
   ral, 269.
Spinal nerves, their double root, 270.
Mode of connection with the cord, 270.
Mr. Grainger's researches, 271.
Encephalic nerves, 271.
How to determine the function of a nerve,
   272-
Anatomy, experiment, 272-3.
Clinical observation, 274.
Functions of the  roots of spinal nerves,
   274.
Discovery of Sir C. Bell, 274.
Functions of the Spinal cord, 275.
Mental and physical nervous actions of
  the cord, 275.
Spread of irritation in the cord, 280.
Tetanus, epilepsy, 280.
Effects of strychnine, &c, 281.
Polarity of  cord  attending peripheral
   excitement, 281.
Effects of cold, 282.
Functions of the columns of the cord,
  282.
Mechanism of the action of the cord, 287.
(a) Dr. Hall's hypothesis of excito-mo-
  tory nerves, and a true spinal cord,
  288.
Emotional fibres of Dr. Carpenter, 289.
Mr. Newport's researches on the nerv-
  ous system of myriapoda, 290.
(&)  The cord considered as a continua-
  tion of the spinal nerves to the brain,
  292.
(c)  Hypothesis  advocated  by the au-
  thors, 293-302.
Antagonism of voluntary and reflex ac-
  tions, 296.
Many actions  need a double stimulus,
  297.
Peripheral disposition of nerves for re-
  flex actions, 298.
limitation propagated in the centres by the
  gray matter, 299.
Action of the sphincter ani, 299.
Physical nervous actions  of the cord in
  locomotion and the attitudes, 301; in
  regard to the generative organs, 302 ;
  in regard to nutrition,  302.
In what  sense  the cord  aids in main-
  taining muscular tone.   Dr. John
  Reid's  observation, 302-3.
The cord not the source of muscular irri-
  tability, 303.
Functions of the Medulla oblongata,
  303; shares in voluntary motion, 305; 
XVI
CONTENTS.
  in sensation, 305 ; in respiration and
  deglutition, 306; in emotion, 307 ; is
  affected in  hysteria, chorea,  hydro-
  phobia, 307.
Functions of the Corpora striata,_308 ;
  their action on motor nerves indirect,
  309.
Functions of the  Optic thalami, 309.
They are the  principal foci of sensi-
  bility,  310.
The  corpora striata and thalami not
  connected respectively with the low-
  er and upper extremities, 311.
Functions of the Quadrigeminal bodies,
  312.
Ganglia of the special senses, 313.
Centre connected with emotion, 314.
Emotion occasions certain diseases, 316;
  affects  nutrition, 317.
Examples of Sympathetic phenomena,
  339.
Sympathetic sensations, 340.
Sympathetic movements, 340.
General remarks on sensation, 351.
Common or general sensibility, 352.
Special sensations, 352.
Sensation  is attended by the idea  of
  locality,  352.
Of Touch, 352.
Nerves of  touch, 353.
Anatomy of the skin.  Elements of the
  mucous system, 353.
Surfaces of the skin, 353-4.
Intimate structure of the Cutis, 354.
Contractility of the skin, 355.
Tactile papillae, their arrangement and
  varieties, 356;  internal  structure,
  359 ; their nerves, 359.
Of the Cuticle, 360.
Changes in its  particles as they ad-
  vance to the surface, 361.
Functions of the Cerebellum, 317.
Experiments of Flourens and others,
  317;  their conclusions  confirmed,
  318.
Gall's hypothesis controverted, 320.
Functions of  the Cerebral  convolu-
  tions, 321.
Results of  anatomy, 321 ; of  experi-
  ment, 322 ;  of disease, 323.
Phrenology,  324.
Attention and memory, 324-5.
Power of  speech, 325.
Cerebral sensations, 325.
Vertigo, 326.
Sleep, 327. #
Somnambulism,  328.
Mesmerism, 328.
Functions  of the  Commissures, 329.
Some general inferences, 330.
Three classes of sympathies, 342.
Rationale  of sympathetic phenomena,
                           CHAPTER XIII.

                       INNERVATION, CONTINUED.

Of the Pacinian corpuscles of the nerves, 345 ; their structure, 347 ; their func-
  tion, 350.

                           CHAPTER XIV.

                       INNERVATION, CONTINUED.
The rete Malpighii not a distinct struc-
  ture, 362.
Cuticle of coloured races, 362.
The nails, 363.
Hairs, 364.
Follicle, cortex, and fibrous part, 364.
Chemical and hygrometric  characters,
  367; varieties, 367.
Lymphatics of the skin, 367.
Sweat-glands, 368;  arrangement and
  structure, 368.
The ducts have a proper tunic in tra-
  versing the cuticle, 369.
Sebaceous glands,  370.
Entozoa of these glands, 371.
Ceruminous glands, 371.
Functions of the skin, 371.
Absorption and secretion, 372.
0^r"AppENDix to the IIth Chapter contains an account of Professor Mat-
      teucci's Electro-physiological researches, 330-39.

                           CHAPTER XII.

                       INNERVATION, CONTINUED. 
CONTENTS.
xvii
The  skin  as the organ  of touch, 373;
  aided by the muscular sense, 373.
Examples of the local concentration  of
  the sense among the lower animals,
  373.
Experiments of Weber on its  relative
  acuteness in different parts, 374.
Power of estimating weight, 376.
Heat and cold, 376.
Duration of impressions of touch, 377.
Subjective sensations of touch, 377.
CHAPTER  XV.
INNERVATION, CONTINUED.
Of Taste, 378.
Structure of the mucous membrane of the
  tongue, 378.
Chorion, papillae, and epithelium of the
  tongue, 379.
Simple and compound papillaz, 380.
Circumvallate papillae, 381.
Fungiform papillae, 382.
Conical or filiform papillae, 382.
Nerves of the papillae, 383.
Functions of  the papillce, 384.
Gradations of papillary structures, 385.
Precise seat of taste, 385.
Nerves of taste, 386.
Conditions of taste, 388.
Do taste  and touch coexist in any  of
  the papillae? 389.
Are  the varieties of taste referable  to
  the varieties of the papillae ? 389.
After-tastes, 390.
Subjective phenomena of taste, 390.
CHAPTER  XVI.
INNERVATION, CONTINUED.
Of Smell.—Cavities of the nose, 391.
Structure of  the nasal mucous mem-
  brane, 392.
The olfactory region, 394.
Nerves of the nose, 396.
Conditions of smell, 399.
Subjective phenomena, 401.
CHAPTER XVII.
INNERVATION, CONTINUED.
Of Vision, 401.
Anatomy of the eyeball, 402.
Sclerotic coat, 403.
Cornea, 404.
Its five layers, 404.
Choroid, 407.
Choroidal epithelium, 409.
Ciliary processes of the choroid, 410.
Iris, 410.
Ciliary ligament and muscle, 412.
Retina, 413.
Its layers, 413.
Yellow spot, 415.
Vitreous body, 416.
Crystalline lens, 417.
Aqueous humour, 420.
Optic and other nerves, 421.
Muscles of the eye, 423.
Eyelids, 424.
Lachrymal apparatus, 426.
Phenomena of vision, 427.
        2
Formation of an image on the retina, 428.
Visual angle, 428.
Distinct and perfect vision, 429.
Adaptation to distance, 429.
Short and long sight, 430.
Spherical and chromatic aberration cor-
  rected, 431.
Reflection from the bottom of the eye,
  432.
Excitability of the retina, 433.
Duration of impressions, ocular spectra,
  434.
Blind spot, 435.
Action of the retina in vision, 437.
Correct vision with an inverted image ;
  visual  idea of  direction, 437;  of
  shape and size, 438; of motion in ob-
  jects, 439.
Doubleness of the organ, 439 d
Single vision, 440.
Mr. Wheatstone's researches, 441. 
xviii
CONTENTS.
   CHAPTER XVIII.

INNERVATION, CONTINUED.
Of Hearing, 442.
The organ in man and animals, 442.
External ear, 444.
Middle ear, 446.
Internal ear, 449.
Osseous labyrinth, 449.
Spiral lamina and its zones, 453.
Cochlearis muscle, 455.
Of the Encephalic Nerves exclusively
  motor in function, 473.
Third pair, 473.
Fourth pair, 476.
Of the Compound Encephalic Nerves,
  481.
Fifth pair, 481.
Eighth pair, glossopharyngeal, 485.
Of the Sympathetic Nerve, 498.
Cephalic portion, 500.
Cervical portion, 501.
Subordinate  processes of  Digestion,
  512.
Modifications in animals, 513.
Classification of food, 514.
Preparatory Processes, 522.
Prehension, 523.
Mastication,  524.
The tongue, 525.
The teeth, 525.
Internal structure of the teeth, 527.
Development of the teeth, 532.
Cochlear nerves, 457.
Membranous labyrinth, 458.
Vestibular nerves, 459.
The auditory and accessory nerves, 461.
Function of the external ear, Savart's
  experiments, 463-4.
Of the tympanum, 465.
Of the labyrinth, 469.
Sixth pair, 476.
Facial nerves, 477.
Ninth pair, 480.
Thoracic portion, 503.
Lumbar and sacral portions, 504.
Function of the sympathetic nerve, 506.
Diet, 517.
Quantity of food necessary for health,
  518.
Hunger and thirst, 521.
First and second dentitions, 536.
Of the jaw bones at different ages, 538.
Movements of mastication, 538.
Insalivation, 539.
The saliva, 540.
Deglutition ; the pharynx, 541.
Oesophagus, 544.
    CHAPTER XIX.

innervation: continued.
    CHAPTER XX.

innervation, continued.
    CHAPTER XXI.

innervation, continued.
CHAPTER XXII.

    DIGESTION.
 CHAPTER XXIII.

DIGESTION, CONTINUED.
Pneumogastric, 488.
Branches of the vagus, 488-9.
Spinal accessory, 495. 
CONTENTS.
xix
CHAPTER XXIV.
DIGESTION, CONTINUED.
The Stomach, 545.
Its mucous coat, 546.
Stomach cells, 547.
Stomach tubes, 548.
Pyloric tubes, 549.
Movements of the stomach, 550.
Changes in the mucous membrane dur-
  ing digestion, 551.
Of the solution  of the stomach after
  death, 553.
The gastric juice, 554.
The acid of the gastric juice, 557.
Nature of the digesting power  of the
  gastric juice, 559.
The chyme, 561.
Rate of stomach  digestion, 561.
Eructation and vomiting, 563.
CHAPTER XXV.
DIGESTION, CONTINUED.
Anatomy  of  the Intestinal  Canal,
  567.
The intestinal canal in vertebrata, 568.
The tunics of the intestinal canal, 572.
Of the valvulae  conniventes, folds and
  villi, 574.
Of the glands of the intestine, 579.
Brunner's glands, 579.
Peyer's glands, 581.
Movements of the intestines, 583.
Changes in the mucous membrane dur-
  ing intestinal digestion, 585.
Of the chyle, 587.
Changes of the food in the  small  in-
  testine, 587.
Function of the Pancreas in digestion,
  592.
The function of the Liver, 596.
Quantity, and the physical and chemi-
  cal properties of the bile, 597-8.
Use of the bile, 600.
Digestion in  the large intestine, 608.
Defecation, 608.
CHAPTER XXVI.
ABSORPTION.
Nature of Absorption, 611.
The absorbent vessels, 612.
Contractility of the absorbent vessels,
  615.
Origin of the lymphatics, 616.
Do the lacteal and lymphatic vessels
  absorb ? 618.
Contents of  the absorbents, 619.
Lymph, 620.
Chyle, 620.
Quantity of chyle and lymph, 622.
Absorption as influenced by the quali-
  ties of the fluids, 623.
Absorption as influenced by pressure,
  625.
Absorption as influenced by the motion
  of the fluid within the vessels, 626.
Function of the absorbents, 627.
CHAPTER XXVII.
THE BLOOD.
General characters of the Blood, 628.
The constitution of the blood, 629.
The quantity of blood in the body, 630.
The phenomenon of the coagulation,630.
Buffing and cupping, 632.
Physical analysis of the blood, 633.
The fibrine, 634.
The red corpuscles, 634.
The colourless corpuscles, 637.
Function of the red corpuscles, 640.
Office of the colourless corpuscles, 641.
Of the development and decay  of the
  blood corpuscles, 642.
The Chemical analysis of the blood, 643.
Composition of the red particles and of
  the haematine, 644.
Influence of venesection and disease upon
  the blood, 645. 
XX
CONTENTS.
CHAPTER  XXVIII.
THE CIRCULATION OF THE BLOOD.
Of the Bloodvessels, 649.
The middle or fibrous coat of the artery,
  650.
Muscular fibres, 652.
Epithelial layer, 653.
Anastomoses of arteries, 656.
The structure of veins, 658.
Of the capillaries, 659.
Of the heart, 662.
Cavities and valves of the heart, 664.
Pericardium  and endocardium, 666.
Of the structure of the valves of  the
  heart, 667.
Mechanism of the valves, 669.
Of the muscular tissue of the heart,
  669.
Nutrition of  the heart, 671.
Nerves of the heart, 671.
Of the action of the heart, 672.
Rhythm of the heart, 674.
The course of the circulation, 676.
Of the portal circulation, 676.
Of the fcetal circulation, 677.
Of the forces which circulate the blood,
  678.
Of the circulation in arteries, 679.
The pulse, 681.
Contractility of arteries, 682.
The force of the heart, 684.
Influence of respiration upon the cir-
  culation, 689.
Of the velocity of the blood in arteries,
  690.
Of the circulation in  the capillaries,
  693.
Of the forces which maintain the capil-
  lary circulation, 694.
Circulation in the veins, 700.
Suction-power of the auricle, 702.
Rapid effect of poisons, 705.
CHAPTER XXIX.
RESPIRATION.
of Respiratory
the
General  description
  Organs, 706.
Comparative anatomy, 706.
Organs  of  respiration  in
  trachea, 707.
Coats of the bronchi, 709.
Infundibula, 712.
Pulmonary artery, 712.
Minute anatomy of the lungs, 713.
Movements of respiration, 716.
Action of the respiratory muscles, 718.
Power of the respiratory muscles, 720.
Use of the trachealis muscle, 721.
Excitation  of respiratory movements,
  721.
Ratio of respirations to the pulse, 722.
Amount of air breathed, 722.
Changes in the respired air, 723.
Influence, of exercise,  temperature of
  the surrounding medium,  age, sex,
  etc., upon the exhalation of carbonic
  acid, 725-6.
Amount of Oxygen inhaled, 727.
Exhalation of nitrogen, 728.
Changes  in  the  blood resulting from
  respiration, 728.
Quantity of carbon removed from the
  body, 730.
Theory of respiration, 731.
CHAPTER  XXX.
ANIMAL HEAT.
Of the Development of  Heat  in the
  body, 733.
Development of heat in plants and ani-
  mals, 733-4.
Temperature of the human body, 735.
Influence of age, sleep, exercise, climate,
  and seasons, etc., upon the temperature
  of the body, 735-6.
Loss of heat by evaporation, 737.
Influence of food, 738.
Influence of disease, 739.
Hibernation, 739.
Theory of animal heat, 740.
Influence of the nervous system, 742. 
CONTENTS.
XX.
CHAPTER XXXI.

       VOICE.
The Larynx, the Organ of the Voice,
  744.
The cartilages of the larynx, 745.
Vocal choirs, 747.
Action of laryngeal muscles, 749.
Nerves, 750.
Of Secretions and Excretions, 757-8.
Secretions, not excrementitious, which
  serve ulterior offices, 759.
Vicarious secretion, 760.
Ingesta and egesta, 761.
Of the Pancreas, 766.
Of the Liver, 767.
Chemical composition, 768.
Lobules of the liver, 771.
Portal canals, 772.
Portal vein, 773.
Hepatic artery,  774.
Duct, 775.
Parietal sacculi, 775.
Of the Kidney, 785.
Surface of the kidney, 787.
Matrix of the kidney, 788.
Uriniferous tubes, 789.
Malpighian bodies, 789.
Convoluted portion of  the uriniferous
  tube, 791.
Straight portion of the tube, 792.
Vessels of the kidney, 793.
Of the Spleen, 806.
Trabecular tissue of the spleen, 807.
Spleen pulp, 808.
Splenic artery, 810.
Malpighian corpuscles, 811.
Action of larynx and theory of vocaliza-
  tion, 750.
Production of vocal sounds, 752.
Chest voice, and  falsetto, 753-4.
Singing, 754.
Influence of nerves on voice, 755.
Speech, 756.
Anatomy of secreting organs generally,
  761.
Of the gland cell, 764.
Of the ducts of glands, 764.
Gall-bladder, 777.
Hepatic vein, 778.
Of the liver cells, 779.
Of the smallest branches of the hepatic
  duct, 781.
Of the passage  of  the  bile into the
  ducts, 784.
Quantity and uses of the bile, 784.
Malpighian tufts, 794.
Of the secretion of urine, 796.
Of the Urine, 797.
Composition of healthy urine, 799.
Uric acid, 800.
Extractive matters, 801.
Pelvis of the kidney, 803.
Bladder, 804.
Epithelium of bladder, 805.
Uses of the spleen, 813.
Of the Thyroid, 815.
Of the Thymus, 816.
Mr. Simon's researches, 818.
CHAPTER XXXII.

     SECRETION.
CHAPTER  XXXIII.

 SECRETING  GLANDS.
     CHAPTER XXXIV.

SECRETING GLANDS, CONTINUED.
CHAPTER XXXV.

 DUCTLESS GLANDS. 
xxu
CONTENTS.
CHAPTER XXXVI.

    GENERATION.
Fissiparous Generation, 819.
Multiplication by Gemmation, 820.
Metamorphosis and metagenesis, 821-2.
Male Organs of Generation, 829.
Testicle, 829.
Vesicular seminales, 831.
Prostate gland, 831.
Penis, 832.
Female Organs of Generation, 839.
Ovaries, 839.
Graafian follicles, 840.
Ovum, 841.
Fallopian tube, 842.
Of Puberty, 846.
Menstruation, 847.
Maturation and discharge of ova, 848.
Of the Impregnation of the  Ovum,
  853.
Micropyle, 853.
Changes in the ovum immediately suc-
  ceeding impregnation, 854.
Rotation of the yolk, 855.
Cleavage of the yolk, 855.
Of the Development  of the Embryo,
  863.
Investing  membrane  and  membrana
  intermedia of Reichert, 864.
First trace of the embryo, 865.
Primitive streak,  866.
Sexual organs in invertebrata, 825.
Sexual organs in vertebrata, 827.
 Urethra, 833.
 Seminal tubules, 835.
 Spermatozoa, 836.
 Development of spermatozoa, 836.
I Movements of the spermatozoon, 837.
Uterus, 842.
Nerves of the uterus, 844.
Vagina  and accessory female organs,
  845.
Urethra, 846.
Formation of blastodermic  vesicle  or
  germinal membrane, 857.
Formation of decidua, 859.
Structure  and  nature  of  membrana
  decidua, 860.
Decidua reflexa, 861.
Formation of dorsal and ventral lamina;,
  867.
Formation of amnion, 869.
Branchial fissures and arches, 870.
Development of the human embryo, 871.
 CHAPTER XXXVII.

GENERATION, CONTINUED.
 CHAPTER  XXXVIII.

GENERATION, CONTINUED.
  CHAPTER  XXXIX.

GENERATION, CONTINUED.
    CHAPTER XL.

GENERATION, CONTINUED.
CHAPTER XLI.

 DEVELOPMENT.
Heat and Rut in animals, 849.
Formation of corpora lutea, 850.
True and false corpora lutea, 852. 
CONTENTS.
xxiii
CHAPTER XLII.
                      DEVELOPMENT, CONTINUED.

Of the Development of the Different I Of the anterior venous trunks,
  Organs, 875.
Spinal column, 875.
Of the face and visceral arches, 877.
Of the nervous system, 878.
Of the organs of vision and hearing,
  879.
Of the heart, 880.
Of the aortic arches, 882.
Of the lungs,
Thyroid glands, 883.
Of the alimentary canal, 883.
Of the Liver and Pancreas, 884.
Of the Spleen, 885.
Wolffian bodies, 886.
Supra-renal capsules, 887.
Organs of generation, 887.
CHAPTER XLIII.
DEVELOPMENT, CONTINUED.
Of the Membranes of the Foetus,
Formation of the placenta, 888.
Amnion, 892.
Liquor amnii, 892.
Umbilical vesicle, 893.
Development of the allantois, 894.
Allantoic fluid, 896.
Umbilical cord, 897.
Birth, 897.
CHAPTER XLIV.

    LACTATION.
Of the Lacteal Glands, 898.
Follicles of the lacteal glands, 899.
Bloodvessels and absorbents, 900.
Milk, 901. 
 
LIST  OF  ILLUSTRATIONS.
               82
               84
After Schwann  84
   Authors     85
fig.                                                               PAGE
 1.  Primary organic cell .....     Authors      32
 2.  Examples of cilia    .......      73
      a.  Portion of a bar of the gill of the sea-mussel—from Dr. Shar-
          pey's art. Cilia, in Cycl. Anat. and Phys.
      g.  Leucophrys patula—after Ehrenberg.
      The rest from the art. Mucous Membrane in Cycl. Anat.
 3.  Cilia of the uriniferous tube  .       .      .        Phil. Trans. 1842  76
 4.  White fibrous tissue  .....     Authors      79
 5.  Yellow fibrous tissue  ....
 6.  The two elements of the areolar tissue
 7.  Development of the areolar tissue
 8.  Meshes of the areolar  tissue when dried
 9.  Polyhedral form of fat vesicles      ...         "         89
10.  Bloodvessels of fat          .     .       .      .         "         90
11.  Margarine and elaine of human fat, separated within 1        t{         q,
      the vesicle  .....       j
12.  Development of the adipose tissue  .       .      .  After Schwann  93
13.  Cartilage-cells from the chorda dorsalis of the Lamprey    Authors     96
14.  Section of articular cartilage from the head of the humerus   "         97
15.  Section of the cartilage of the ribs  ...         "         98
16.  Section of the thyroid  cartilage     ...         "         98
17.  Elementary structures from an intervertebral disc .         "        101
18.  Vertical section of the upper end of the femur      After Bourgery  106
19.  Longitudinal section of bone       .       .      .    Authors      110
20.  Venous canals in the diploe of the cranium .      .                 Ill
21.  Ultimate granules of bone  .       From a preparation of Mr. Tomes 112
22.  Lacunae and pores of osseous tissue .      .      .                 112
23.  Transverse  section  of bone surrounding an Haver-1        tt        -,-,0
      sian canal .      .     .      .      .      . j
24.  Forms of the lacunae and pores of osseous tissue  . From Mr. Tomes 113
25.  Systems of lamellae in the compact tissue of a long bone    Authors   115
26.  Radiation from the Haversian canals      .      . From Mr. Tomes 116
27.  Haversian systems of  lamellae      ...                 116
28.  Vertical section of the knee-joint of an infant     .    Authors      118
29.  Scapula of a foetus, exhibiting the progress of ossification    "        119
30.  Vertical section of cartilage near the ossifying surface      "        119
31.  Horizontal section near the ossifying surface      . From Mr. Tomes 120
32.  Vertical section of newly formed bone, showing the 1     \„t\,nr.a     ioi
      second stage  of ossification       .      .      .J
33.  Another section     .....        "        121
34.  Epithelium of serous membrane    ...        "        129
35.  Yellow fibrous element of the areolar tissue of serous )       te        ■, oq
      membrane .      .     .      .      .      . j
36.  Transverse sections of injected striped muscles   j Cycl. Anat., art.)  -^^r
      from the  Frog and from the Dog .      .     {    Muscle     \
37.  Fragments of elementary  fibres, showing  a   f Altered from Cycl. \  -j^q
      cleavage into discs and fibrillae   .      .   j Anat., art. Muscle J 
XXVI
LIST OF ILLUSTRATIONS.
FIG.                                                                 PAGK
38. Transverse section of striped muscle, showing the f From the Phil. |  -j^g
      sarcous elements                             {  Trans. 1840  j
39. Lateral union of the sarcous elements     .      .       .     "      150
40. Sarcolemma stretching between two fragments of a striped fibre "      151
41. Hernial protrusion of the sarcous tissue through the  )          ,t      251
      sarcolemma       .      .      .      .      .  j
42. Attachment of tendon to muscle     .     From the  Phil. Trans. 1840  151
43.      "           "         "                "    •    "             152
44. Stages of the development of striped muscle, partly from Schwann
      (a. Schwann ;  b.f. Authors ; the rest from Phil.  Trans. 1840)      152
45. Development of striped fibre in the Insect  .        Phil. Trans. 1840  153
46. Fibres of unstriped muscle and their cytoblasts Cycl. Anat., art. Muscle  154
47. Capillaries of muscle .....      Authors      160
48. Termination of the nerves in muscle       .      .   After Burdach   161
49. Contraction of striped muscle       .     From the Phil. Trans. 1840  170
50.      "      "        "                        "          "         171
51.      "      "        "                        "          "         172
52. Tubular and gelatinous fibres of nerves    .       .      Authors      194
53. Nerve-tubes of the Eel, in water and ether  .       .         "         195
54. Nerve-vesicles from the Gasserian  ganglion        .         "         197
55. Caudate nerve-vesicles from the cerebellum and cord       "         197
56. Caudate nerve-vesicle, and axis-cylinder of a tubular  "I       «<         10q
      fibre,  from the cord                            j
57. Two views of the vesicular and fibrous matter of the cerebellum          199
58. Vesicular and fibrous matter in the Gasserian ganglion      "         199
59. Decussation of fibres within a nerve .      .      .   After Valentin  202
60. Terminal loops of nerve in the pulp of a tooth     .         "         204
61. Origin of a spinal nerve and union with the sympathetic   Authors    205
62. Ganglion of the Greenfinch  ....   After Valentin  207
63. Otic ganglion of the Sheep   ....         "         208
64. Nervous fibres of Insects    ....        Authors    209
65. Stages of the development of nerve  .      .      .   After Schwann  210
66. Six  transverse sections of the spinal cord   .      .        Authors    235
67. Transverse section of the cord      .     After Stilling and Wallach  236
68. Front view of the Medulla oblongata       .       .        Authors    240
69. Posterior view of the Medulla oblongata   .       .           "      242
70. Transverse section of the Medulla oblongata After Stilling and Wallach  244
71. Diagram of the encephalon   ....      After  Mayo  246
72. Capillaries of the gray substance of the convolutions       Authors    266
73. Portions of the cord in Spirostreptus       .      .   After Newport  291
74. a. b. c. d. Pacinian corpuscles      .      .       .       Authors )
 "  e.  _        "        "       rare form After Henle and Kblliker j   d4b
75. Pacinian corpuscle—general structure     .      .        Authors    347
76. Pacinian corpuscles—arrangement of nerve-tube  .
77. Elastic element of the cutis of the axilla
78. Tactile ridges of the skin of the palm, with  the )
      orifices of the sweat-ducts                      j
79. Deep surface of the cuticle of the palm, with the cuti-  I
      cular lining of the sweat-ducts                  J
80. Under-surface of the cuticle of the leg, contrasted  .
81. Papillae of the palm, cuticle detached
82. Bloodvessels of the papilke of the  heel
83. General section of the integument of the sole
84. Skin of the heel, treated with weak  and strong solution of potass
85. Cuticle of the scrotum of a negro
86. Section of the nail and its matrix
87. Hair and hair-follicle seen in section
88. Surface,  longitudinal and transverse sections, of hair
89. Layer of sweat-glands of the axilla .
90. Sweat-gland and its bloodvessels
91. Cuticular portion of a sweat-duct of the heel
349
355
357

357
358
359
359
360
361
362
363
364
365
368
368
369 
LIST OF ILLUSTRATIONS.
XXVll
PIG.
 92.
 93.
 94.
 95.
 96.
 97.
 98.
 99.
100

101.
102.
103.
104.
105.
106.
107.
108.
109.
110.
 111.
112.
 113.
 114.
 115.
 116.
 117.
 118.
 119.
 120.
 121.
 122.
 123.
 124.
 125.
 126.
 127.
 128.
 129.
 130.
 131.
 132.
 133.
 134.
 135.
 136.
 137.
 138.
 139.
 140.
 141.
 142,
 143,
 144,
 145,
 146,
 147,
 148,
 149,
 150
 151
                                                               PAGE
Three views of sebaceous glands and hair-follicles.       Authors   370
Entozoa of the sebaceous follicles  .       .      •                 371
Dorsal surface of the tongue.             .       After Soemmering 379
Simple papillae near the base of the tongue
Vertical section of a circumvallate papilla .
Compound and simple papillae of  the foramen caecum
Fungiform papilla, with its simple papillae and vessels
Forms of  the conical or filiform papillae
a. Section of filiform and fungiform papillae \
b. Structure of filiform papillae            J
Nerves of the papillae of the tongue
Cartilages of the nose
Ciliated epithelium of the nose
Olfactory region of the  nose, vertical section
Capillaries of the olfactory region .
 Nerves of the outer wall of the nose
Olfactory filaments of the dog
Nerves of the septum of the nose  .
Vertical section of  sclerotica and cornea  .
 Tubes of the cornea proper
 Vertical section of the cornea
 Choroid and iris    ....
 Vessels of the choroid and iris
 Choroidal epithelium, and pigment of  the choroid
 Border of posterior elastic lamina of cornea
 Diagram  of ciliary muscle  .
 Vertical section of the retina
 Membrane of Jacob
, Yellow spot of retina
, Position  of lens in vitreous humour
 Lens at different ages
 Cells and fibres of the lens .
 Lens, to show its lamellae
 Arrangement of fibres in the lens
 Plan of the optic tracts and nerves
 Course of fibres in the chiasma
 Tubules  of the optic nerve .
 Conjunctival surface of eyelids
 Meibomian gland of a foetus  From
 Lachrymal apparatus
 General section of the ear  .
 Diagram of the inner wall of the ty
 Ossicles of the ear
 Osseous labyrinth of the left side
 Interior of the osseous labyrinth
 Cochlea of a new-born Infant
 Section of the cochlear canal
 Denticulate lamina of the cochlea
 Lamina spiralis of the cat  .
 Cochlearis muscle  of the sheep
 Plexiform arrangement of cochlear
 Membranous labyrinth of left side
 Nerves of membranous labyrinth
 Termination of nerve in ampulla
       Authors   380
                 381
                 381
       Authors   382
                 382

                 383
                 384
After Soemmering 392
       Authors   393
                  394
                  395
After Soemmering  396
       Authors   397
    After Arnold
       Authors
mpanum
nerves
  After Zinn
After Arnold
     Authors
                              399
                              405
                              405
                              406
                              408
                              408
                              409
                              411
                              412
                              414
                After Jacob   415
            After Soemmering  416
               After Arnold   417
            After Soemmering 417
                    Authors   418
               After Arnold   419
                    Authors   419
                              421
                       «      422
                       "      423
             After Soemmering 425
a preparation of Dr. Goodfellow 426
             After Soemmering 426
               After Scarpa   444
                    Authors   447
               After Arnold   448
             After Soemmering 450
                              451
               After Arnold   453
                    Authors   454
                              455
                              455
                       "      456
                              457
                              458
  Diagrams illustrative of Savart's researches on
    hearing        ....

Vertical section of human incisor  .
Sections of enamel and dentine
Sections of tubules of dentine
  After Breschet
After Steifensand 460
  After Wagner  460
               r 465
After Savart
Authors
  466
  466
I  467
  528
  529
  530 
xxviii
LIST OF ILLUSTRATIONS.
FIG.
152.
153.
154.
155.
156.
157.

158.
159.
160.

161.

162.

163.

164.

165.

166.

167.

168.

169.


170.

171.

172.

173.
174.
175.
176.
177.
178.
179.
180.

181.

182.
183.
184.

185.

186.

187.
188.
189.
190.
Views of the enamel fibres  .
Enamel pulp and matrix    .
Stomach cells and epithelium
Horizontal section of stomach cell and tubes
Vertical sections of  mucous membrane of stomach
Section of mucous membrane of the small intestine j
 in the dog  .      .       .      •      *.,"■'
Transverse section of Lieberkiihn's tubes or follicles
Villi of duodenum of dog   .      •      •
     "          "       the columnar epithelium
 stripped off       .
Capillary  plexus of the villi of the human small
 intestine   .      .       .      •             •
Vertical section of the coats of the small intestine
 of a dog   ......
Epithelium from the cavity of the duodenum of a
 dog 2\ hours after food   .
Vertical section of  the  mucous membrane of the
 duodenum in the horse, showing Brunner's glands
A  solitary gland  from  the small intestine of the
 human  subject    .....
A patch of Peyer's glands of the adult human sub-
 ject ...••••
Vertical section through a patch of Peyer's  glands
 in the dog  ...•••
Diagram to illustrate the formation of a backward
 axial current
Longitudinal wavy fibres from the thoracic  duct of 1
 the horse,  with  nucleated particles  lining  the  >
 vessels     .      .       .      •.*.■'
One of the inguinal  lymphatic glands injected with |
 mercury; and superficial lymphatic trunks     .{
Ramification of a lymphatic of the under part of j
 the tail of a tadpole       .      .      .      .J
Fluid from the mesenteric gland of a rabbit, when \
 white chyle was present in the lacteals  .      .  I
Red  corpuscles from human blood  .
Red  corpuscles of the ox
Red  corpuscles of pigeon's blood
Blood corpuscles of  the common frog
Red  corpuscles of fishes    .      .      .    After
Blood corpuscles of  the crab
Phases of the human blood corpuscle
Corpuscles from the vena cava hepatica of the em-)
 bryo chick, on the twentieth day of incubation    )
Granules, granule-cells  and red  blood corpuscles  j
  from the embryo chick    .       .      .      .J
Granules, granule-cells, and red corpuscles .
Nucleated cells, red corpuscles, and granules
Finely fibrous layer  of the longitudinal fibrous tunic  )
  of  the aorta of the horse  .       .      .      .  j
Coarsely fibrous layer  of the  longitudinal  fibrous  1
  tunic of the aorta  of the horse    .      .      .  j
A portion of the circular fibrous tunic of the aorta {
  of the horse       .      .       .      .      . j
Section of the aorta of the  ox
Section of the whole thickness of the artery
Circular fibrous coat, showing penniform fibres
A single bar or penniform fibre from the circular)
  fibrous tunic of the aorta of the ox      .      .  j
              TAGE
After Retzius   531
    Authors   533
               547
               548
               548

    Authors   573

   Dr. Salter   574
               576

               577

               577

    Authors   578

   Dr. Salter   579

               579

 After Boehm  580

               580

    Authors   581

   Dr. Brinton 585


   Dr. Salter   614
After Mascagni	614
After Kolliker	617
Dr. Salter	620
<< << a Wharton Jones a It	635 635 636 636 636 636 638
Dr. Salter.	638
(i	639
<<	639 639
<<	651
<<	651
(<	651
n it	652 652 653
a	fi*?.
 
LIST OF ILLUSTRATIONS.
xxix
FIG.
191.

192.
193.

194.
195.

196.
197.
198.
199.
200.

201.

202.
203.
204.

205.
206.
207.

208.
209.

210.


211.
212.
213.
214.
215.
216.

217.
218.

219.

220.
221.

222.
223.

224.

225.
226.

227.
228.

229.
230]
Authors	653
Dr. Salter	654
it	654
Unstriped muscular fibres from the aorta of the)
 horse       .      .      .       .       .      . J
Epithelial particles from the aorta of an ox
Particles of epithelium and nuclei from the aorta}
 of a horse  .      .      .       .       .      . j
Arrangement of the capillaries on  the  mucous
 membrane  of the large intestine of the human
 subject     ......
A  capillary vessel from the vesicular matter of the 1
 human brain       .      .       .       .      . j
Epithelium from the left auricle of the horse     .        "
Epithelium from the left ventricle of the horse   .        "
A  portion of the aortic semilunar valve in the dog        "
Diagram of the semilunar valves of the aorta    . After Morgagni
Fibrous tissue  of  a  semilunar valve, beneath the)    -non
    a    a-  ™                                   r    Dr. Salter
 endocardium      .      .       .       .      . j
Poiseuille's haemadynamometer,  modified by Volk- { a ft.  Volk     fiR7
 mann      .       .      .       .       .      . |
660
661
667
667
667
668
668
'':}
Haemadromometer of Volkmann
Small bronchial tube from a man, age 50  .
Small bronchial tube laid open, showing the ar-
 rangement of the cartilaginous  flakes
Thin slice from the pleural surface of a cat's lung
Bronchial termination in the lung of the dog
Thin section of a cat's lung, injected with gelatine)
 through the pulmonary artery    .      .      . j
Section of the lung of a fowl.
Diagrams to show the movements in ordinary and
 forced respiration  .       .       .      .      . |  Hutchinson
Cartilages of the  larynx and epiglottis, and upper ( From a PrePa" ]  ,.
 .:„„.'ni,.....u„                        **  i  ration made }■  t
                                              ' I  by Mr. Cane J
                  691
                  709
     Dr. Salter    710
   From Rossignol 712
                  712
      Authors    714
  From Mr. Rainey 715
1 f   From Dr.  j
. | Hutchinson J
717
  rings of the trachea
Thyroid, cricoid, and arytenoid cartilages
View of the larynx from above
Internal parts of larynx of the right side
Diagram to show parts in vocalization
Caecal biliary tube of the cray fish  .
Transverse section of a small  portal canal and its)
  vessels      .      .      .       .      .      . j
Human liver, showing arrangement of vessels
Portion of the fibrous capsule  of a lobule of pig's )
  liver.      .      .      .       .      .      . j
Lobules of a cat's liver injected through the portal 1
  vein, and also through the hepatic vein  .      . j
Longitudinal section of a small portal vein and canal
A lobule of pig's liver, showing branches of portal)
  vein .      .       .      .       .             .J
Part of arterial ring from a lobule of pig's liver
A small lobule of the pig's liver,  showing the mode )
  of branching of the duct  .       .      .      . j
Portion of a large duct of the pig's liver, showing \
  parietal sacculi    .      .       .      .      . j
Longitudinal section of a hepatic vein
Section of horse's liver, showing radiating lines of]
  cells.       .      .      .       .      .      . j
Portions of tubular network of the lobule  .
Terminal portion of interlobular  duct to  illustrate )
  Dr. Handfield Jones' view .       .      .      . j
Small branch of interlobular duct, pig
Narrowest portion of the duct and its junction with
  the cell-containing network
45
:}
 After Willis

     it
 After Leidy

After Kiernan

   Dr. Beale
     u

 Mr. Bowman

After Kiernan

   Dr. Beale
After Kiernan
  Dr. Beale
Dr. Beale
746
748
749
753
763
769
770
771

771
772
773
774
775

776
778
779
780
782
783
7S3 
XXX
LIST OF ILLUSTRATIONS.
FIG.
231.  Malpighian arteries, bodies, and uriniferous tubes .
232.  Malpighian tuft from the proteus anguineus
233.  Small portion of loop of capillary vessels of the tuft
      of kidney of the large water newt  .
234.  Entire uriniferous tube from the large black newt .
235.  Transverse section of a pyramid of  the human kid-
      ney, about a quarter of an inch from the papilla .
236.  Malpighian tuft of the horse .       .      •
237.  Malpighian tuft injected, showing efferent vein
238.  Malpighian tuft from the parrot
239.  Plan of the arrangement of the elements of a lobe
      of the kidney of the boa constrictor
240.  Part of Fig. 239, shaded and more highly magnified
241.  Plan of renal circulation in man and mammalia
242.  Various forms  of lithic  acid crystals, lithate  of
      soda, oxalate of lime, etc.  ....
243.  Casts of uriniferous tubes   .       .      .Partly
244.  Crystals of triple phosphate and cystine
245.  Cells from the  trabecular  tissue of the spleen of
      human foetus      .....
246.  Muscular  fibre-cells from the spleen of the sheep
247.  Pulp of the spleen  .....
248.  Transverse section of the human spleen, showing
      the mode of the  distribution of the arteries
249.  Splenic  corpuscle,  and its connection with the
      neighbouring vessels      .       .      .      .
250.  Development of the thymus .
251.  Binary and  quaternary divisions of the simple fol-
      licles of the thymus       ....
252.  Multiplication of vorticella microstoma
253.  Multiplication of na'is proboscidea  .
254.  Gemmation of hydra and vorticella  .
255.  Conjugation of conferva bipunctata  .
256.  Origin and branching of the seminal tubes .
257.  Transverse section of the vas deferens
258.  Vesicula seminalis  .      .       .      .      .
259.  A small artery of the corpora cavernosa
260.  Portion of seminal tubules of man  .
261.  Spermatozoa of the river cray-fish  .
262.  Development of the spermatic filaments of the rab-
      bit  .
263.  Ovary of the human subject ....
264.  Mammalian  ova     .
265.  Ova  in various stages  of  development from the
      toad's ovary.      .
266.  Muscular  fibre-cells,  from a gravid uterus, in va-
      rious stages of development
267.  Muscular  fibre-cells from  the uterus  three weeks
      after parturition   .....

268.  Corpora lutea of the human  female   at different
      periods     ......

269.  Cleavage of the yolk in  ascaris nigrovenosa, and
      acuminata  ......
270.  Multiplication of cells in the yolk of ascaris dentata
      and cucullanus elegans    .

271.  Ova of the guinea-pig in various  stages of develo^"
      ment       ......

272.  Section of  human  uterus at commencing pregnancy
	PAGE
Mr. Bowman Dr. Beale	789 790
n	791
	792
n	793
Mr. Bowman n n	793 794 794
Mr. Bowman	795
n	796 796
Dr. Beale	798
after Dr. Johnson 798
    Dr. Beale    799
                 807
Mr. Gray
809
810
                 811

 After Mr. Simon 817
I         "      818
 After Ehrenberg 819
     Mailer     820
                 821
  After Meyen   821
    Dr. Beale     830
                 830
After E.H.Weber 831
  After Kolliker  833
    Dr. Beale    835
                 836
| After Kolliker 837
   After Coste    840
                 841
J    Dr. Beale   841

l After Kolliker 843

i After Kblliker 844
 f Altered  from^)
 ! Montgomery, I
  Kolliker, and [  bbl
     Dalton
(AfterKolliker)  _„
\  andBagge  }  856
I After Kolliker 857

I              (  857
[• AfterBischoflN  858
j              (  859
  After Weber   860 
LIST OF ILLUSTRATIONS.
XXXI
PIG.
273.  Uterine glands of the bitch  .
274.  Thin section of human decidua soon after impreg-
      nation     ......
275.  Portion of germinal membrane about the sixteenth
      hour of incubation .      .      .      .       .
276.  Portion of the germinal membrane  of the bitch's
      ovum      ......
277.  Plan, showing the development of the dorsal and
      ventral  laminae    .      .      .      .       .
278.  Germinal membrane with rudiments of the embryo
      of the dog  ......
279.   f Plan  showing the  manner of formation of the
280.   j   amnion, allantois, and umbilical vesicle
281.  Visceral, or branchial arches of an embryo dog
282.  A human ovum about fifteen days after conception

283.  Human foetus between the twenty-fifth and twenty-
      eighth days......
284. Heart of chick at forty-fifth, sixty-fifth, and eighty-
      fifth hours of incubation
285. Development of respiratory  organs .
286. Embryo dog, showing junction of umbilical vesicle
      with intestinal canal
287. Extremity of a villus of the placenta
288. Relation between foetal and maternal vessels in pla
      centa       .....
289. Uterine sinuses and foetal tufts
290. Villi of the foetal portion of a placenta
291. Folds of  vitellary membrane and vasa lutea
292. Diagrams to show the arrangement of the allantois
      and placenta in different classes of animals
293. Diagram of uterus  with  a fully-formed  but very
      young ovum       ....
294. Preparation with six milk-tubes injected
295. One of the smallest lobules of a lacteal gland
296. Terminal follicles of lacteal gland  .
297. Lacteal gland of a newly-born child
298. Colostrum corpuscles and milk globules
               TAGE
After Dr. Sharpey 861

I       "       861

|                865

l  After Bischoff  867


{ P m!^?" }  M«
I  After Bischoff  868
   Dr. Beale

After Bischoff
After Dr. A.
 Thomson
f After Dr. A. j
\  Thomson   j
[  After Coste
869
870
872

873
Dr. A. Thomson 881
    Rathke     883
 After Bischoff 884
 E. II. Weber   889
   Dr. J. Reid
 E. II. Weber
Mr. Dalrymple
    Dr. Beale
890
890
891
893
895
}
I  After Wagner  896
Sir Astley Cooper 899
  After Langer   900
    Dr. Beale     901
     Langer      901
    Dr. Beale     902 
 
THE
PHYSIOLOGICAL    ANATOMY
AND
PHYSIOLOGY   OF   MAN.
                      INTRODUCTION.

   The aim of all natural knowledge is to ascertain the laws, which
 control  and regulate the phenomena of the universe.   So nume-
 rous, and so diversified are these phenomena, that a division of
 labour has been found, not merely convenient, but absolutely neces-
 sary, for the study of them.  The position  and movements of the
 planetary system, the crust of the earth, and its various component
 strata, the treasures hidden in  its womb, the abundant  vegetation
 that grows upon its surface, or beneath its waters,  and the number-
 less hosts of animals that dwell upon the land, or in the rivers, lakes
 and seas, form separate branches of scientific investigation, between
 which a sufficiently distinct line of demarkation is established by the
 nature of the objects of inquiry peculiar to each.   But, in all depart-
 ments of science, the same general rules, for conducting the investi-
 gation, prevail, and it is only by a close adherence  to  these, that we
 can arrive at safe and satisfactory conclusions.
   In any scientific inquiry, the first step must be, to form  a general
 notion of the characters and properties of the objects of investigation.
 In the next place, it is necessary to observe carefully the phenomena
 which they naturally present; and, if  they be within our reach, to
 produce such variation in them by artificial means (by experiments),
 as may serve to throw light  upon them.   If the phenomena, under
 observation, be complex, we must analyze  them,  with a view to
 ascertain the simpler ones, of which  they are composed.  By this
 analysis, and by the  elimination of such  as are merely collateral, we
 arrive at a  phenomenon, uncomplicated, incapable of further  sub-
 division, and fundamental; and this we are contented to receive as
 an ultimate fact, the result of a law in constant and universal opera-
 tion.  The accumulation of observations and experiments affords us
 Experience ; points out the  ordinary succession of phenomena, and
teaches us the ways of Nature.  If these  phenomena are found to
present a certain uniformity, we are  authorized to refer them to the
      3 
26         ULTIMATE FACTS—THEORIES—HYPOTHESES.

operation of one common Cause, and we are thus led to the  expres-
sion of the Law which regulates their  occurrence.  Proceeding in
this way, we  are  enabled to  explain the whole  train of phenomena
which have  been investigated,—that  is, to  devise a Theory which
develops the rationale of their occurrence.
  But sometimes our experiments and observations throw an imper-
fect light upon the phenomena which  are the  subjects of investiga-
tion ; or the latter are so remote, or  so little  under our control, as to
render both observation and  experiment extremely difficult, and, in
some cases, impossible.  The " instances" which we are enabled to
collect, are consequently dubious and obscure, and point darkly, or
not at all, to  ultimate facts; they present little or no general resem-
blance,  and cannot  be properly  associated together.  Here  is  no
foundation on which  to build  a theory:  but great advantage may be
gained, if, with the little light we derive from these particular obser-
vations, aided by previous knowledge of general laws, we can frame
an hypothesis,  offering some  explanation of the phenomena.  The
adoption of such  an  hypothesis, even  for a  temporary purpose, will
" afford us motives for searching  into analogies," may suggest new
modes of observation and experiment, and " may serve as a scaffold
for the  erection of general laws."
  Previously  to the time of Lavoisier, chemists were perfectly fami-
liar with the occurrence of combustion under various circumstances;
but the opinions (hypotheses)  which  prevailed as to the real nature of
this  process,  afforded a very  unsatisfactory explanation of it.  Sub-
sequently, however, by the  labours  of Lavoisier, Davy, and  others,
this complex phenomenon has been  observed in all its phases ; it has
been carefully analyzed, and  has been proved to occur in all cases,
where substances possessed of strong chemical attractions, or different
electrical relations, are brought within mutual influence.   The  ulti-
mate fact, thus arrived at, is, that intense chemical combination  al-
ways gives rise to the  evolution of  heat, and,  in many instances, to
that of light also.
  Again, a great number of observations  have  shown  that bodies
combine together only in certain quantities, or  in multiples of them;
that each body  has its proper combining quantity, and that it never
enters into  combination except in that quantity, or some  multiple of
it.   This is  an ultimate fact, ascertained by numerous experiments,
and  indicates  the law,  which is  so important in  chemistry,  that
bodies unite  with each  other in  their  combining proportions only,
or in multiples of them, and in no intermediate proportions.  And
this, again, has led to the beautiful  generalization of Dalton, that the
ultimate atoms  of bodies are their  respective  combining quantities,
and bear to each other the  same proportion as their combining equi-
valents do.
   Or, to take an example from  the  science which is to form the
subject of the following pages. The function  of respiration  in  ani-
mals is a very complex process, respecting the nature of which many
unsatisfactory hypotheses had been  formed, owing to the obscurity in
which many of the phenomena, immediately or remotely connected 
ORGANIZED AND UNORGANIZED BODIES.
27
with it, were involved.   Until the law of the diffusion of gases, and
of the permeability of membranes by them,  had been  developed,
and until it had been  shown that carbonic acid is held in solution in
venous blood, no theory of respiration could be framed adequate to
explain all the phenomena.   It is now proved that, in this process, a
true interchange of gases takes place through the coats of the pulmo-
nary blood-vessels, the  oxygen of the air abstracting and occupying
the place of the carbonic acid of the blood.  An admirable example
is thus afforded of a most important vital process  taking place in
obedience to a purely physical law.
   Living objects are those which properly belong to the science of
Physiology.  These are strongly contrasted  with the inanimate bodies
(which have never lived),  to which other branches of natural science
refer.   At the same time, there  are many points  of  resemblance be-
tween them; and as both owe their origin to the same Creative man-
date, and are  reducible (as will  be  seen  by-and-by)  to  the  same
elementary constituents, so they are subject in a  great degree to the
same physical laws, and are to be investigated according to the same
principles of philosophical inquiry.
   We propose, in the  first  place, to  compare living, or  organized
bodies, with inanimate, mineral, or unorganized bodies, and to explain
what is meant by the term  Life.  Secondly, to review briefly, and
with reference to  their leading distinctions, the phenomena  of the
vegetable and animal kingdoms.   Thirdly, to point  out  the value of
a knowledge of Physiology, especially that of  Man, in relation  to
medicine, and to explain the best  mode of pursuing it.
   I. Every living Being is organized,—that is, composed of different
parts or organs, each  of which has its definite structure,  by which it
differs from other parts, and  is  capable of fulfilling a  certain  end.
The complex matter, which enters into the composition of an organ-
ized being, or organism, is termed  organic matter, and is obtained
by its proximate analysis.  The ultimate analysis of this matter re-
solves it into elementary principles, such as constitute  other objects
of the universe.
   The various bodies that  compose the mineral  kingdom, do not ex-
hibit the same distinctness, and variety of structure in their component
parts, nor is there any adaptation of their parts to separate  functions;
they are therefore called unorganized or inorganic, and  chemical ana-
lysis  resolves them into those simple elements which admit of no fur-
ther subdivision.
   Organized bodies are found in two states or conditions.   The one,
that of life, is a state  of action, or of capacity for action.   The  other,
that of death, is one in which all vital action has ceased, and to which
the disintegration  of the organized body succeeds as a natural conse-
quence.
   An organized body in a  state of active  life exhibits  certain pro-
cesses, by which its growth and nutrition are provided for, and which
enable it to resist the destructive  influence of surrounding agents—
processes, the  object  of which is to promote the development, and to 
28
ORGANIZED AND UNORGANIZED BODIES.
preserve  the  integrity of the body itself.  The simplest  animal, or
vegetable, is an illustration of this remark.
  But there are organized bodies  in which life may be said to be
dormant.  In these, no actions or processes can be observed, nor any
change taking  place : yet, if placed under certain favourable condi-
tions, vital activity will  soon become manifest.   Of this, we  have
familiar examples 'in a seed, and in an egg.   It is well known, that
seeds will retain their form, size, and other properties  for a very
considerable period ; and afterwards, if suitably circumstanced, will
exhibit the process of germination  as completely as  if they had been
only recently separated from the parent plant.  Eggs, also, may be
preserved for a long time without injury to the power of development,
or to the nutrition, of the embryo contained within them.
  It is worthy of observation, that those processes, which denote
vital activity, may be sometimes temporarily suspended, even in fully
formed animals and vegetables; and, in such  instances, life  may be
said to become dormant.   The privation of moisture is  the ordinary
cause of  this interruption to the phenomena of life.   In dry weather,
mosses often become completely desiccated and appear quite dead,
but will speedily revive  on the application of moisture.  And the
common  wheel animalcule,  although apparently killed by the drying
up of the fluid in which it had  been immersed, will speedily resume
its active movements on being supplied anew with  water.
  Inorganic bodies may be  resolved  by ultimate analysis into Oxy-
gen, Hydrogen, Nitrogen, Carbon, and about  fifty other substances,
which Chemists regard as simple, because they appear to consist  of
one kind of matter only ; that  is  to say,  they have  hitherto resisted
further decomposition.  These elements unite in certain definite pro-
portions  to form the compound  inorganic  substances.   And this
union may consist either of two  simple   elements—as oxygen and
hydrogen, to  form water; oxygen and  the  metal sodium, to form
soda ;  chlorine and sodium, to form common salt;  or, of  one binary
compound with another similar one, as of sulphuric acid (sulphur  -f
oxygen)  with  soda (sodium -f oxygen), to form sulphate of soda ;
or, again, of two such salts as  the last with  one another, as alum,
which  consists of sulphate of alumina united with sulphate of potassa.
   As regards the mode of combination in the  first of the examples
enumerated in the preceding paragraph, where single  equivalents of
the elementary bodies unite, there can be but  one  opinion.   In the
formation of water, one  equivalent of hydrogen  combines  directly
with one equivalent  of oxygen.   But when  one  equivalent of one
element  is united with two  or more of the other, to form the com-
pound substance, the mode of combination is not so evident.   Per-
oxide  of hydrogen, for example, may either result from the  direct
combination of one equivalent of hydrogen with two of oxygen  or it
may be a compound of one equivalent of water with one of oxygen.
   In the second example, in which two  binary compounds unite to
form a salt, two modes of constitution  have  been suggested.  The
first supposes a direct union of a basic oxide with  an acid oxide  as
of  soda (sodium -f oxygen) with  sulphuric acid (sulphur + oxygen) 
         CHEMICAL CONSTITUTION OF ORGANIZED BODIES.      29

in sulphate of soda ; and that  each constituent preserves its  proper
nature in the compound.   According to the second view, one of  the
constituents of the salt is supposed to undergo decomposition, yielding
up to the other an element, which, joined to it, forms a compound
radicle, to which the remaining element  is united ;  as hydrogen
would be to a simple, or compound radicle (chlorine or  cyanogen),
to form a hydro-acid.   Thus, in the  salt commonly called sulphate
of soda, this view supposes that the  soda yields  its oxygen  to  the
sulphuric acid, and that a  compound is  formed  of sulphuric acid,
plus an additional equivalent of oxygen, which  may be represented
by S04, and has been called by Professor Daniell oxysulphion.  The
compound  radicle thus formed unites with the metal sodium, and
the  resultant  salt should  be called  oxysulphion of sodium.  This
view, then, it is evident, would lead us to regard Glauber's salts as a
binary compound, instead of a ternary one under the first theory; just
as chloride of sodium is a binary compound, the  compound radicle,
oxysulphion, and the simple one, chlorine, standing  in the same rela-
tion to the  metal sodium.
   This latter theory, of the binary constitution of  salts hitherto re-
garded as oxygen salts, is of great interest in reference to the com-
position of organic substances, as will appear in a future  paragraph.
It has been  supported  by Professor  Graham, and  subsequently by
Professor Daniell, whose opinion has been grounded on the phenomena
of electrical decompositions.
   Organized bodies are capable of being resolved, by chemical ana-
lysis, into the inorganic simple elements ; but the list of simple sub-
stances which may be obtained from this  source comprises only about
seventeen.
   Of the four widely-spread elements, oxygen, hydrogen, nitrogen,
and  carbon, two, at least,  will  be found in every organic compound;
hence, as Dr.  Prout has suggested, these four may  be  conveniently
distinguished  as the essential elements of organic matter.   The
other simple substances are found in  smaller quantities, and are less
extensively diffused ; these  may be termed its  incidental elements.
They are sulphur, phosphorus, chlorine, sodium, potassium, calcium,
magnesium, silicon, aluminum, iron, manganese, iodine  and bromine;
the last two are obtained almost exclusively from marine plants and
animals.
   Between these elementary substances, and the organized  animal
or vegetable  texture, there intervenes a  class of  compounds, called
proximate principles, or organic compounds, or organizable substances.
These may be obtained in the  first stage of  the chemical analysis
of various  animal or vegetable  tissues.  From the  organized  struc-
ture, called muscle, for example, we  obtain by analysis, first, fibrin,
a  proximate principle, which  is its chief constituent; and, subse-
quently, by  the  analysis of  fibrin,  we  get  the  simple elements,
oxygen, hydrogen, carbon, nitrogen and  sulphur, in certain propor-
tions.   On the other hand,  by  synthesis, the  combination of  certain
inorganic elements (which  hitherto  has been  effected only  in  the
living body)  will produce the organic compound, fibrin  ; from  which, 
30       CHEMICAL CONSTITUTION OF ORGANIZED BODIES.
again, the organized structure muscle, is formed.  And so in other
cases.
   In  the organized body the constituent  particles are, as it were, art-
fully arranged, so as to form peculiar textures, destined to serve spe-
cial purposes in the living mechanism of the animal or plant to which
they belong.   The  organic compounds which  may be obtained from
these are devoid of this mechanical arrangement of particles, and it
is a beautiful feature of the organized body,  that every part  has its
special office, that there is nothing superfluous, nothing wanting. As
each organized body has  a certain end  to  serve in the  economy of
the living world, so each  organ has its proper use in the animal or
plant.  In this adaptation of parts to  the performance  of  certain
functions, we see  the  strongest evidence  of  Design ;  and,  amidst
much apparent difference  of form and obvious diversity of purpose,
the anatomist recognizes a  remarkable  unity  of plan—affording in-
contestable proof that the whole was devised by One Mind,  infinite
in wisdom, unlimited in resource.
   The true proximate principles are those substances which are the
first  obtained by the analysis  of the organized  textures; such are
gluten,  starch, lignine, from  the  vegetable   textures,  or albumen,
fibrin, casein, from the  animal ones.  From these again a great vari-
ety of compounds has been obtained  by  various processes, owing
to the tendency which their  elements have to form new combinations.
By boiling starch in dilute acids, it becomes converted into a  kind of
gum, and starch-sugar.   By placing yeast in contact with sugar, the
latter is converted into alcohol and carbonic acid, without the  yeast
affording it any of its chemical constituents; and, in the germination
of barley, or of the potatoe, a  peculiar substance is  formed, the con-
tact of which with the starch of the  barley or potatoe converts it into
sugar.  Innumerable examples might be quoted  from various vege-
table compounds, showing that the affinity, which holds together the
elements of organic substances, is so feeble, that it affords but slight
resistance to  their  entrance into new combinations.  In  this way a
large class of organic matters is formed, which  it seems proper to
distinguish from the true proximate principles, under the name of
secondary organic compounds.
   In analyzing the  true proximate principles of  organic  substances,
it is  found that they consist for the most part  of three or four of the
essential simple elements, and that, as many of them contain  a large
number of atoms,  their combining proportion  is represented  by  a
very  high number.   Respecting the mode of combination  of these
 elements much uncertainty prevails.  Some  chemists consider them
 united  equally with each other, and regard  the organic principles
 themselves as ternary or quaternary compounds of them.  But others
 have suggested  a mode  of combination  more analogous to that of
 inorganic substances (see pages 28, 29); namely, that two or  three of
 the elements form a compound radicle, with which the remaining one
 unites to form a binary compound.   In  a body, for example,  consist-
 ing of  three elements, two  would  form  the compound radicle,  or  in
 one composed of four elements, three would constitute it.  This mode' 
         CHEMICAL CONSTITUTION OF ORGANIZED BODIES.       31

af composition has been rendered more probable in the secondary
organic products, than in the true proximate principles ; and it may
be illustrated by an example taken from the former class.  Ether is
composed of four atoms of carbon, five atoms of hydrogen, and one
atom of oxygen; the carbon and  hydrogen constitute a hypothetical
compound  radicle, called ethyl, which  is united with one atom of
oxygen :  so that ether is an oxide of ethyl, and its  formula may be
expressed C4 H5 + 0.
  Among the secondary organic  products of the vegetable class we
meet a few instances of binary compounds of simple elements;  but
the great majority of proximate organic elements, whether primary or
secondary, are composed of three or four essential elements.
  In contrasting, then, the chemical composition of organic with that
of inorganic substances, we perceive that, applying the binary theory
to both classes of  substances, their  mode of combination is strictly
analogous; there being, however, this distinction, that, among organic
substances  combination with a compound radicle is the prevailing
mode,  and that the union of two simple substances is rare.   If, on
the other hand, we adopt the  theory of oxy-acid salts  for  inorganic
compounds, and view the organic principles as ternary or quaternary
compounds of simple elements, each to  each, then it is evident that
the most marked difference must exist between the two classes of
compounds, the  latter being formed on  principles  entirely dissimilar
from those  which regulate the composition of the former.
  It is probable, however, that the progress of Chemistry will show
that the binary theory is applicable to both classes of substances, and
that the same mode of chemical  composition  prevails through both
kingdoms of Nature.
  If so much uncertainty exists in reference to the manner of combi-
nation of the simpler elements to form organic compounds, it  is  no
wonder that the  attempts of chemists to  produce them  by artificial
processes should have met with so little success.  No one  has  suc-
ceeded in the synthesis of any of the true proximate principles ; and,
indeed, it is  very questionable whether  any of those products  of a
vital chemistry will ever be produced elsewhere than in the living
organism.  The  formation of urea, a secondary organic  compound,
has been effected by Wohler from the  cyanate  of ammonia, by de-
priving it of  a little ammonia through the action of heat. And it
must be admitted, as no unimportant step in the  synthesis of organic
compounds, that nitrogen gas has been found to  unite with charcoal,
under  the influence of  carbonate of potassa  at a red  heat.   The
cyanide of  potassium, which is thus formed, yields  ammonia, when
decomposed  by  water ;  so  that  cyanogen, and, through  cyanogen,
ammonia, can be primarily derived  from their  respective  elements
contained in the  inorganic world. [Graham's Chemistry, p. 709, [Am.
Ed. p. 671].)  Allantoin, an analogous compound to urea, and formic
acid, have likewise been artificially produced.
  We  proceed from this review of the  chemical constitution of or-
ganic and inorganic substances, to compare them together in other
respects. 
32
ORGANIZED BODIES.
Primary organic cell,
  In examining an  organic  substance which is  organized, i. e., so
constructed as to form part of a living organism, we  find it to pos-
sess very distinctive characters.  It generally contains water in con-
siderable proportion ; its form is more or less rounded and free from
angularity, and it is never crystallized.  When considerable  hardness
or density is required, the quantity of water is small, and an inorganic
material is combined with  the organic matter ; as, in bones, phosphate
of lime with the gelatine of the bone, or, in  plants, silex with their
epidermic tissues.
  An organized body is composed of parts, distinct from each other
in structure and function,  and it may be  subdivided into a  series of
textures, each differing from  the others in physical  and vital proper-
                   ties.  The existence of a great variety of textures,
      Fig. 1.        in  an  animal, is  an indication of a  high degree
                   of organization.  Among the  lowest organized
                   creatures  there is much uniformity of structure,
                   although variety of  parts or organs.   Still these
                   creatures by their actions show that  materials of
                   different  properties  must exist throughout their
                   bodies.
                     The simplest  and  most  elementary organic
                   form,  with which we are acquainted, is that of
showingr^hers ceii-mem-  a cell, containing  another  within it {nucleus),
u1rean^cleoiurcleus' and  which again contains a granular body {nucleolus).

   This appears, from  the interesting researches of Schleiden  and
Schwann, to  be the primary form which organic matter  takes when
it passes from the  condition of a proximate  principle to that of an
organized structure.
   The bodies  of  some animals and of some  plants, are composed
almost entirely of cells of this kind ; and in the early  development of
the embryo, all the tissues, however dissimilar from each other, con-
sist at first of  nucleated cells, which are afterwards  metamorphosed
into the proper elements of the adult texture.
•   An organized body possesses a definite form  and  disposition, not
only as regards its component parts, but likewise when  viewed  as a
whole.   Each organized body has its appropriate and specific shape;
and to each a certain size  is  assigned.  To observe  and classify the
wonderful diversity of form exhibited  by plants  and  animals, has
given employment to Naturalists  in  all ages ;  and  the sciences of
Zoology and systematic Botany have been founded upon the results
of their labours.
   Every organized body  is limited in its duration ; it has " its  time
to be born and its time to die," and at death it  passes by decompo-
sition  into simpler and  more stable  combinations of the  inorganic
elements.
   In their origin, organized  bodies are  generally, if not  always, de-
 rived from similar ones.   Some have supposed that out of decaying
vegetable or animal matter minute  animals or  plants of other kinds
may be formed : but it seems most probable that in those  cases in 
REPRODUCTION.                      33
which they had been supposed  to be formed, the seeds or eggs, or
even the parents themselves, had been concealed in the decaying
matter, or floated in the  surrounding  atmosphere.   Recent experi-
ments throw considerable doubt upon this doctrine of the spontaneous
generation of  organized bodies, by showing that neither vegetation
nor the development of animalculae will go  on in fluids which have
been  subjected  to  such processes as must  inevitably kill whatever
germs may have been diffused around or throughout them.  In  the
present state  of our knowledge it may be  said, that the Harveian
maxim, " Omne vivum ex ovo," is the rule ; and that if there be any
other mode in which the development  of living beings takes place,
it is the exception.   The progress of Anatomical knowledge is every
day revealing  to us the organs, and  the mode of generation in  the
minutest and the  least conspicuous  forms  of  vegetable and animal
life; and thus the doctrine, which supposes that living objects may
arise by a sort of conjunction of the elements of decomposing organic
matter, becomes more and more improbable.
  How  beautiful is the  provision which  this power, possessed by
organized bodies, of generating others, affords, for preserving a per--
petual succession of living beings over the globe!   The command,
" Increase and multiply," has never ceased to be fulfilled from  the
moment it was uttered.   Every hour, nay, every minute, brings  into
being countless myriads of plants  and animals, to supply in lavish
profusion  the  havoc which  death is continually making; and it is
impossible to  suppose  that the earth can  cease to  be in this way
replenished, until the same Almighty Power, that gave the command,
shall see fit to  oppose some obstacle to its fulfillment.
  In addition  to this power of  propagation, organized  bodies enjoy
one of conservation and reproduction.   Solutions of continuity,  the
loss of  particular textures,  whether resulting from  injury or from
disease, can be repaired.   Parts, that  have been removed, may be
restored by a process of growth in the plant or animal,  and in some
animals the reproductive power is so energetic, that if an individual
be divided, each segment  will become a perfect being.   This power
of reproduction is greater, the more simple the structure  of the organ-
ized body; the more similar to  each  other are  the constituent parts,
the  more  easy will  reproduction be.   Numerous examples of this
power may be adduced,—the healing of wounds, the adhesion of
divided parts are  familiar to every one.  New  individuals are deve-
loped from the cutting of plants: the division of the hydra into two,
gives rise to the production of  two new individuals.   If a Planaria
be cut into eight or ten  parts, according to Duges, each part  will
assume an independent existence.
  The power of reproducing single parts only, is possessed by animals
higher in the  scale.  In snails,  part of the  head, with  the antenna?,
may be  reproduced, provided the section have been  made so as  not
to injure the  cerebral ganglion.  Crabs and lobsters can regenerate
their claws, when the separation has taken  place at an articulation;
and  spiders enjoy the  same power.   In lizards, the tail, or a limb, 
 34       ASSIMILATION.—EXCRETION.—DECOMPOSITION.

 can be restored, and in salamanders the same  phenomenon has been
 frequently witnessed.
   Organized bodies can appropriate and assimilate to their own tex-
 tures other substances, whether  inorganic or organic.  This process
 is that which is most characteristic of living creatures: in virtue of it,
 animals  and plants are  continually adding to their textures new
 matter, by which they are nourished.   Plants appropriate their nutri-
 ment from the inorganic kingdom, as well  as from decaying organic
 matter;   animals, chiefly from  organic matters, whether animal or
 vegetable.   Both possess the wonderful power of re-arranging the
 constituents of these substances into forms identical with those of the
 elements of their various tissues—and  of thus  making them part and
 parcel of themselves.
   Together with a  process of  supply, there  is one  of waste con-
 tinually  in  operation.  Animals  and  plants are ever throwing  off
 effete  particles from their organisms.   These, under the name of
excretions, appear in various forms—either as inorganic compounds,
or as secondary organic products.  Thus, carbonic acid is given  off
in large quantities from animals;  water, likewise, forms a considerable
portion of their excreted  matter, and serves to hold in solution  salts,
and secondary organic compounds, which result from  the waste of the
tissues.   In this way, also, urea, lithic acid, and biliary matters are
excreted.  In plants, water is  excreted from the leaves, a  pheno-
menon which has been compared to the perspiration of animals; and
various other excretions, which are sometimes made to serve an  addi-
tional purpose in the economy of the vegetable, besides that of get-
ting rid of superfluous matter, are doubtless formed by the secondary
combinations of the effete particles of their textures.
   These  two processes, excretion, or the expulsion  of effete particles,
and assimilation of substances from without, are necessarily mutually
dependent.  As long as new matter is being appropriated, old par-
ticles  must be thrown  off, otherwise growth would  be unlimited—
and were excretion alone to go  on, the destruction of the organism
must speedily ensue, by the gradual waste of the tissues, to  which
no new supply was  afforded.   In both  processes new combinations
are taking place, as it were, in opposite directions; in the one from
the simple to the complex to form organized parts,  in the other, from
the complex constituents of the textures to the simple organic, or
inorganic compounds.
   As each texture of the organism has this tendency to change during
life, so, the whole organism tends to decomposition, when  death puts
a stop to  all further  absorption of nutritive matters.   Dead organized
matter is  speedily dissipated under certain conditions.  These  are the
presence  of  air, moisture,  and a  certain temperature, or contact with
an organic substance which is itself undergoing decomposition  The
affinity which held together the elements of the organic substances is
destroyed by the  cause which occasioned their death, and they are
set free to obey new affinities and form new compounds.
   When  we consider the large  number of  equivalents which  enter
into the formation of each  molecule  of organic compounds,  it need 
DECOMPOSITION.—LIFE.                   35
not excite surprise  that a great variety of products results from the
decomposition of animal and vegetable matter.  This decomposition
is of two kinds, which are distinguished by the names, fermentation
and putrefaction.   Liebig  proposes to limit the former term  to the
decomposition of substances devoid of nitrogen, and the latter  to that
of azotized matters.  The  products of vegetable matter in fermenta-
tion, by the action of yeast, are carbonic acid and  alcohol; those  of
azotized matters, whether  animal  or  vegetable, are  carbonic acid,
hydrogen, phosphuretted and  carburetted hydrogen,  hydrosulphuric
acid, cyanogen, hydrocyanic acid, ammonia, and lactic acid.
   Let  us compare the characters of organized bodies, as described  in
the preceding paragraphs, with those of inorganic substances.
   In form, in size, in duration, the contrast is most  striking.  The
inorganic matters are  aeriform, liquid, or  solid:  they are prone  to
assume the crystaline form, and to exhibit surfaces bounded by right
lines, and uniting to form angles.   No distinction of parts, or organs,
is to be found in the mineral  substance; its minutest fragment is  in
every respect of the same nature with the  largest mass.   A portion
of chalk, not weighing  a drachm, contains  particles of  the same
form and size as those  of the largest cliff on the sea-coast.   Inorganic
substances, as compared with organic, are unlimited in size and dura-
tion :  they will  continue for ages  without  augmentation  or  waste,
provided no mechanical  violence  nor  chemical agent be brought  to
act upon them.
   None of those internal actions or processes, which we described in
the organized body, occur in the unorganized one; there is no  power
of reproducing lost or injured  parts, no growth,  no excretion, no
generation.   From  age to age the mineral remains unchanged, with-
out motion, obedient to the common laws of  matter, and  unable  to
resist them by any inherent power.
   Within the living organisms of the organic kingdom, on the con-
trary, are ceaseless  motion and change.  The absorption of the new
material, and the ejection of the old, comprise a continual succession
of actions,  in  which the organized  being  is  ever organizing and
disorganizing.   This constant round of  actions,  which is the more
diversified as the organism is more  complex, we call Life.   There
is an apparent spontaneousness in these actions, which distinguishes
the mechanism  of  an  animal or plant  from  the machines  of  human
construction.  Yet the living organism is not the less dependent for
the continuance, nay, for the very existence of those actions upon the
ordinary agencies of nature.   Light, heat, the  atmosphere, chemical
affinity, each has its share in promoting  the functions in the play of
which  Life consists ; all are more or less  necessary to  the integrity  of
these  actions ; and it is contrary to  experience to suppose that Life
can be manifested without their  co-operation.  Yet  we cannot say
that Life is produced  by, or is the result of, these agencies.   It  is
equally contrary to  experience to  find the  manifestation  of Life  in
other than organized bodies.   Nevertheless, it cannot be affirmed that
organization is the cause of Life, for without the other agents no vital
action  occurs, and it has already been shown that the  organization of 
36
LIFE.—VITAL STIMULI.—DEATH.
 new matter is effected only by living bodies. The mutual co-operation
 of organized  matter with the forces at work in the inorganic world,
 is necessary to the development of vital phenomena.
   The term Life, then, may be regarded as denoting an ultimate fact
 in science,  which may be thus expressed;  that certain compounds of
 matter—which, as being artfully arranged in a  particular  form for  a
 special  end, and  associated together by  a certain mechanism, are
 called organized—do, by their co-operation with physical  and chemi-
 cal forces, manifest a train of phenomena,  which are of the same, or
 of an analogous kind, for all organized beings; that is to  say, they
 manifest the phenomena of Life.   All organized substances, capable
 of thus co-operating with the other natural agencies, are  called living;
 and, although they may not be positively in action, they  are yet alive,
 as being  ready to act when the  complementary conditions to vital
 action shall be supplied to them.  Thus the seed is alive, although
 not in action; but,  immediately it is brought into contact with mois-
 ture and  heat,  life  is  manifested.  Hence these agents, moisture,
 heat, light,  &c, are said to act as vital stimuli.  The organic matter,
 in becoming  part of a living machine, acquires  certain properties,
 very  different from what it possessed  before;  these are called vital
properties:  they continue  as  long  as  the  organization remains un-
 changed.   For example, a certain proximate element is organized to
 form muscle;  it then acquires the property of contractility, which it
 retains during life.
   According  to our  experience, organic  matter  derives vital pro-
 perties in  by far the majority of instances, and  probably  in all, from
 a previously existing organism.  The egg, while within  the body of
 the mother, acquires vital properties ; and it manifests an independent
 life when  it is laid, if the requisite conditions  (vital stimuli) are then
 supplied.    Thus is life transmitted from one living being  to another;
 and the life of a  present  generation of animals and  plants  has its
 source in  that of a previous generation.  If we trace a race upwards,
 through generations innumerable, to that which first flourished on the
 earth, we find the true source of vital action to be in Him, " in whom
 we live, and move, and have our being."
   Thus, then, out of the same elements of which the inorganic king-
 dom consists, God  has created  a series of material substances, which
 by their action and reaction with other  physical agencies, exhibit,
 apparently  in a spontaneous manner, the phenomena of Life, and
 manifest a series of peculiar forces capable of opposing and controlling
 the other  forces of nature.  While these substances retain a perfect
 organization, and are supplied with their proper stimuli, vital actions
 go on without  interruption, and no changes take place in the matter
 of the  organism, excepting  such as result from its proper affinities.
 But no  sooner is the integrity of  its structure  destroyed, or the influ-
 ence of the vital stimuli withdrawn, than action ceases,'the organism
 dies, and  the organic matter yields up its elements to form new com-
 pounds, a large proportion of which are inorganic.
   Many are not content with this simple expression of facts, and seek
 a theory to  explain the phenomena of organized bodies, and to account 
THEORIES OF LIFE.                     37
for the mysterious actions of Life.  The ingenuity of philosophers has
been not a little taxed for this purpose;  and the  history of the  rise
and  fall of many an  hypothesis, which has  been framed upon this
subject, affords a salutary warning to those who may be tempted to
wander into the regions of speculation and fancy, deserting the safe
and beaten path of inductive reasoning.
  It does  not fall within the scope of this work to examine the various
theories of Life.   One or two, however, we deem it right to notice,
with the hope of at once exposing their inadequacy, and elucidating
more fully the statement above given  respecting Life.
  From a very early period  in the history of natural science, there
has been  a tendency to ascribe these effects to a certain principle, or
Entity, possessing powers  and properties which (however men may
try to impress themselves with the contrary notion) entitle it to rank
as an intelligent agent.   It is true, that, according to  most of the ad-
vocates of this doctrine, this power is supposed to be superintended
and  controlled by the Deity himself, and, by this supposition, they
have screened themselves against the accusation of attributing to a
creature the powers of the Creator.
   A little examination of this doctrine will show, that is has no pre-
tensions to the title of a theory.
   Aristotle attributed the organization  of  animals and  vegetables,
and  the  vital  actions exhibited  by  them, to a  series of animating
principles, (4i>*<«,) differing  according to the  nature of the organized
bodies  constructed by them, and acting  under the direction of the
Supreme  animating principle {fvan).   He  supposes that each par-
ticular kind of organized body had its proper  animating principle,
or tyvm, and that the variety of the former really depended upon
certain original differences in the nature of  the latter, so that  every
distinct species of animating principle would necessarily have its ap-
propriate  species of body.
   Harvey, likewise, assumes the existence of an animating principle,
by which every organism is moulded into shape, out of materials fur-
nished  by the parent, and which, pervading  the substance, regulates
the various functions of its corporeal residence.  But, at a subsequent
stage of his inquiries, in assigning the blood as the special seat of this
principle, he advances  another supposition  totally at variance with
his previous hypothesis ; namely, that as, during the  development of
the  chick in  ovo, the  blood is formed  and is  moved, before any
vessel, or any organ of motion  exists, so in it and from it originate,
not only motion and pulsation but animal temperature, the vital spirit,
and  even  the principle of life itself.   So  completely biased  were the
views of  this illustrious  man, by his  exaggerated notions respecting
the nature and properties of the blood!
   The celebrated John  Hunter, who does not appear  to have been
acquainted with  the views expressed by Harvey, revived a somewhat
similar hypothesis;  and it is curious  that the same fact should have
so attracted the attention of both as to have given the  first impulse to
their speculations. This fact was, that a prolific egg will remain sweet
in a warm atmosphere, while an unfecundated one will putrefy.  The 
38
THEORIES OF LIFE.
views of Hunter have  been received with very general  favour  by
English physiologists.
   Hunter ascribes the  phenomena of  life to a materia vita, diffused
throughout the solids and the fluids of the body.   This  materia vita
he considers  to be " similar to the materials of the brain:" he distin-
guishes it from the brain by the title  " materia vita diffusa," while
he calls  that organ " materia vita  coacervata," and supposes that it
communicates with the former through the nerves, the  chorda inter-
nuncia.  And  Mr. Abernethy,  in  commenting upon these  views,
explains Mr. Hunter's  materia vita to be a subtile  substance, of a
quickly and powerfully mobile nature, which is superadded to organi-
zation and pervades organized bodies;  and  this  he regards as, at
least, of a nature similar to electricity.
   Muller advocates the presence of an " organic force," resident in
the whole  organism, on which the  existence of each part depends,
and  which has the property of generating from organic  matters the
individual organs necessary to the whole.  " This rational creative
force is exerted in every animal strictly in accordance with what the
nature of each requires; it exists already in the germ, and creates in
it the essential parts of the future animal."
   An hypothesis, not dissimilar to that last mentioned, is maintained
by Dr. Prout, and, as  appears to us, it has been  pushed by him to
the utmost limits which the most fanciful speculation would admit of.
He supposes that a certain organic  agent (or agents) exists, the inti-
mate nature  of  which is unknown, but to which  very extraordinary
powers are ascribed.   It is superior to those agents whose operations
we witness in the inorganic world: it possesses the power of con-
trolling and directing the operations of those inferior agents.   " If,"
says Dr. Prout, " the existence of one such organic agent be admitted,
the admission of the existence of others can  scarcely be withheld;
for the existence of one only is quite inadequate to explain the infinite
diversity among plants  and animals."  " In all cases it must be con-
sidered an ultimate principle, endowed by the Creator with a faculty
little short of intelligence, by means of  which it is enabled to con-
struct such a mechanism from natural elements, and by the  aid of
natural agencies, as to render it capable of taking  further advantage
of their properties, and of making them subservient to its use."
   The hypotheses of Aristotle, Muller, and Prout, and  the earlier of
those proposed  by Harvey, seem all alike ; they assume  that organi-
zation and life  are  directed and  controlled by an  Entity, or Power,
"endowed with a faculty little short of intelligence," the ^vzn of
Aristotle, the animating principle  of  Harvey, the organic force of
Muller, and the organic agent of  Prout.  What the mechanism may
be by which this entity acts, they  do  not determine ; but it is evi-
dently such as bears no analogy to any known natural  agency.   Its
existence is independent of the organism, for it has directed both  the
organizing process and the living actions of the being.   Whence then
is it derived  ?   According to Muller, from the  parent, for it exists in
the germ,—it derives its powers from the same source,  and its pedi-
gree may, therefore, be traced to the first created individual of each 
THEORIES OF LIFE.
39
species of animal or plant.  Are we to conclude, then, that organic
agents generate organic  agents, and  transmit their powers to their
offspring ?  Or must we assume, that, for each newly generated ani-
mal  or  plant, a special  organic agent is deputed " to  control and
direct"  its organization, development, and growth?
  The  modern  advocates of this doctrine have  been driven to  its
adoption, from the difficulty (or, as they conceive, the impossibility)
of explaining the  phenomena of organization and life on principles
analogous to  those  on  which  the changes  of inorganic matter may
be accounted for:  this difficulty consisting in  the supposed  existence
of certain differences in the mode of combination of the elementary
constituents of organic and  inorganic compounds, seconded by the
fact, of the synthesis of organic compounds having hitherto baffled the
chemist's  art.  It has  puzzled them to think that out  of  the same
elementary and proximate  principles, so infinite a variety of animals
and  plants could be  formed; and Dr. Prout has been especially
staggered by the  fact, that carbon and  water, which contribute  so
largely to the formation of various  organisms, have never, although
aided by heat, light, and electricity, when out of an organized body,
and  left entirely to themselves, been  able to unite, either  in  virtue of
their own properties or from accident, so as to form any plant or ani-
mal, however insignificant.
  In the first place, let it be observed, that many of the  phenomena
of life  may be accounted  for on  physical or chemical principles.
The changes  effected  in the air and in the blood  by respiration, the
phenomena of absorption, and, in some degree, those of secretion, are
the results of purely physical processes.  It is in the highest degree
probable that many of  the actions of the nervous system  are due to
physical changes in the two kinds  of nervous matter, substances of
complex constitution   and  high  equivalent number,  and  therefore
prone to change.   Stomach-digestion is now known to be a chemical
solution; the  generation of heat is due to the same chemical phe-
nomenon as will give rise to it in the inorganic world; and electricity
is also similarly deAreloped within the body.  How entirely dependent
on physical changes are  the senses  of vision  and hearing,  and how
completely are their organs adapted to the laws of light and sound !
And, doubtless, a further insight into the nature of the various organic
processes will reveal to us a closer analogy between the laws by which
the two great kingdoms of nature are governed.
  Nor is there  so  great  a  chasm between matters  organic and in-
organic, as to chemical composition, as some  would have us believe.
It has already been shown that  modern chemical research tends to
prove a similarity as regards  the mode of combination  of the ele-
ments in both ; and the labours of chemists have been crowned with
success in forming some  organic  products   by artificial  means.—
(See p.  31.)
  And let it not be forgotten that the living laboratory of the animal
and  plant is one well  stored with means for analysis and synthesis:
the continual introduction of new material gives full scope to the play
of chemical  affinity, and at  every  point the constant  attendants of 
40
THEORIES OF LIFE.
chemical  action, heat and  electricity,  are  developed.  May it  not
reasonably be inferred that these agencies, which the chemist can so
readily turn to account in his artificial processes, are not idle in  the
work of combination and decomposition in the living body ?  A great
difference as to sensible qualities, in the various organic products, by
no means implies  great difference  of chemical  constitution, for it is
well known that the addition or removal of a single atom of one of
the ingredients of any compound is sufficient to produce a substance
with totally new properties ; and such is the complex nature of organic
molecules, that the attraction between their component elements yields
readily to disturbing causes.
  But how shall we explain the  strange process of organization, in
the production of that  infinite diversity  of forms, that " insatiable
variety of Nature,"  which is so conspicuous  in the vegetable and
animal kingdoms?  Must we imagine the creation, in corresponding
number and variety, of  a duplicate order of beings,  whose  duty it
shall be to  preside  over  the  development of each species,  and to
impress each with its  peculiar characters ?  Or does it not seem
more consistent with that  grand  simplicity, which the  phenomena of
nature everywhere  present, to suppose that the organization of ani-
mals and  plants, in  such  great variety, is the result of the primary
endowment of organic matter, at the creation of the first parents of
each species, by the Almighty ?   The animal or vegetable matter of
each  species was  created to propagate  after a  certain fashion, and
after that only; the organic cells, of which these organisms consist in
the early  stages of development, have the power of evolving  the
adult  tissues of animals and  plants of their own  species only:  the
simple volvox develops, from its interior, organic  cells which become
volvoces; and the cell, which forms the ovum of the elephant or  the
mouse, is  able, by an inherent power of multiplication, to evolve  the
skeletons and organs of each of those animals respectively.
  The peculiar endowments of  the organic matter, composing  the
various tribes of animals and  plants, are transmitted from parent  to
offspring.   But they admit of certain modifications  under the influ-
ence of circumstances affecting the  parents, as is proved both in  the
animal and  vegetable  kingdoms  in  the  production of  hybrids.
" Two distinct species of the same genus of plants," says Dr. Lindley,
" will often  together produce  an offspring intermediate in character
between themselves, and capable of performing all its vital functions
as perfectly as either parent, with the  exception of its being unequal
to perpetuating itself permanently by seed; should  it not  be abso-
lutely sterile, it  will  become  so  after a few  generations.    It may,
however, be rendered fertile by the  application of the pollen  of either
of its parents;  in which case its offspring  assumes the character  of
the parent by which  the  pollen  was  supplied."   The  same thing
precisely occurs among animals, and  the  mixed  offspring, or mule,
produced  by the union of different  species  is incapable of breeding
with another mule;  but not so with  an animal  of the same species as
either  of  its parents.   How  entirely inadequate is the theory  of
organic agents to explain these occurrences;  it cannot, surely, be 
THEORIES OF LIFE.
41
 maintained that a mixed organic agent is  produced from  the con-
 junction of the organic agents of the dissimilar species to direct the
 formation of this mixed organism!
   The remarkable fact, that the various tribes of the  human race,
 dissimilar as they are, were derived  from the first  created pair, may
 be adduced as  a  striking  illustration  of the influence of physical
 agency in modifying organic  development.   The most potent cause
 of these changes has been climate ; but particular customs and usages,
 connected  with the uncivilized state, have  not  been without their
 influence.  Climate also produces  considerable modifications in the
 size and  other characters of  the lower animals.  Sturm affirms that
 cattle transported from the temperate zones  of Europe (Holland  or
 England) to the East Indies, become  considerably smaller in their
 succeeding generations.
   The theory of organic agents affords  no more satisfactory explana-
 tion of disease, or of death.   In both cases the organic agent must
 be at fault; for as it is the sole guide  and controller of the organizing
 process, so it  is not to  be supposed that  anything  can go  astray,
 except under its guidance.  And yet it seems impossible to imagine
 that the ordinary causes of disease could affect such an entity.  On
 the other hand, any physical or mental cause,  general or local, affect-
 ing the substance of which the  body is composed, may so  alter and
 modify the affinities  of  its particles  as to  occasion  a  material dis-
 turbance in their actions; and it is not difficult to conceive that this
 disturbance may be  of such a kind as to put a stop  to vital action
 immediately or remotely.
   So much for the dependence  of Life and Organization on a con-
 trolling and directing Entity.   The sagacity of John Hunter led him
 to reject this doctrine entirely; but, as he completely passed over the
 influence  of the natural agencies of inorganic nature upon organized
 beings, he was forced to assume the presence of a peculiar material
 substance, pervading and giving vital properties to solids and fluids:
 yet such  a constituent of the body  ought  to be  demonstrable by
 chemical  or other means.   It is clear that  this materia vita cannot
 be, as Mr. Abernethy suggested, electricity, or anything  akin  to it.
 Electricity requires for its development  the  reciprocal action of dif-
 ferent  kinds of  matter,  and  it  is abundantly  evolved  in  various
 animal processes, as  a necessary result of chemical laws.   If, there-
 fore, organization  and vital actions depended upon electricity, this
 agent would, at once, be formed by, and direct the formation of each
 organism.
  Mere composition of matter does not give life, says Hunter;  if he
 had added, that organized bodies acted on by,  and  co-operating with,
 certain vital stimuli,  developed vital actions, there would have been
 no need for the assumption of a materia vitse.  The resistance which
 living animals  introduced into the stomach  are capable of affording
 to its  solvent powers, and the digestion of the walls of the stomach
 by its own  fluid  after sudden  and violent death, seemed to denote
that the dead animal, or dead  stomdch, had lost a something which
previously protected them against the influence of the gastric fluid.
       4 
42
FUNCTIONS OF ANIMALS AND PLANTS.
But this is no more than a case familiar to chemists, viz., the influ-
ence  of a stronger affinity controlling a weaker.   When  iodide  of
potassium is  mixed with a solution of starch, no change ensues; but,
if a minute quantity of  chlorine be added,  a blue iodide of starch is
instantly formed ;  the superior affinity  of  the  iodine for the potas-
sium hindered the  union of the former with the starch ; but, as soon
as the iodine was set  free  by the stronger attraction  between the
potassium and the  chlorine,  it speedily  united with the starch.  So,
in the living  animal, the affinity of its component particles for each
other  is greater than their  affinity for  the  gastric fluid ; but in the
dead  animal  the  former affinity is destroyed, the latter comes into
play.   Whether is it more philosophical to  assume the removal of a
particular agent, for which removal no cause can be assigned; or,  to
state the simple fact of the physical  difference between  dead and
living organic matter ?
   II.  It is very difficult to  define a precise boundary  between the
vegetable and animal kingdoms.  The lowest animals exhibit so much
of the plant-nature, that naturalists  are as yet undecided as to the
true location  of some species.  The common sponge, for instance, is
claimed for each kingdom.
   The various processes by  which are effected the ceaseless motion
and change, so characteristic of living beings,  are called, in physio-
logical language, Functions.
   The functions, which are common  to all organized beings, have a
twofold object; the preservation of  the individual, and the  propa-
gation of the  species.   Those destined for the former purpose are the
JVutritive Functions: those for the latter are comprehended  under the
general title Generation.
   The first step in the nutritive functions of both plants and animals,
is to form a fluid, which contains  all the  elements necessary to nour-
ish the various textures, and to supply materials for  the secretions.
This fluid is, in plants, the sap; in animals, the blood.
   In both classes of beings  a process of absorption precedes the full
development of the nutritive fluid:  it is by this means that material
is obtained for its formation.  Within the plant or animal it becomes
more  completely elaborated.
   In plants, the absorption takes place by the spongioles of the roots.
A fluid,  already prepared  in the soil,—water, holding in  solution
carbonic acid and  various mineral substances,—passes through them
into the  vegetable organism, without  undergoing any  reduction  or
preparation during its transit.   In  animals, however, the food expe-
riences much change, and a more or less elaborate process of digestion
takes  place,  before a fluid  is  formed,  capable, when  absorbed  of
furnishing the materials of the blood.
   Plants, fixed by their roots in the soil, imbibe from it their nutri-
ment.  Animals, obtaining food from  various  sources,  introduce it
into a digestive cavity,  where it is prepared for absorption
   The presence of a digestive  organ, or stomach, is characteristic of
animals.  I he only instances in which a similar organ  may be sup-
posed to exist in  the vegetable kingdom  are  to be  found in those 
FOOD OF ANIMALS AND PLANTS.
43
remarkable modifications of leaves, called pitchers {ascidia) in  Ne-
penthes,  Sarracenia, and Dischidia.   In  the  last two  plants, these
organs certainly serve to retain and dissolve the bodies of insects in
the fluid which partially fills them :  in Sarracenia, according to Mr.
Burnett, the fluid contained in the pitchers is very attractive to in-
sects, which, having reached its  surface, are prevented from return-
ing by the  direction  of the long  bristles that  line the cavity.   The
dissolved food is then absorbed into the plant.
   On the other hand, the animal kingdom affords some exceptions to
the presence of a stomach.   In such  animals, the absorption of nu-
trient fluid  takes  place  by a general surface.   The  Volvox globator
has  no inlet to its interior but through  the  pores in its walls. A
parasite of  the human body, the Acephalocyst, also derives  its nutri-
ment by imbibition  through  its  walls.   A familiar example is the
Acephalocystis endogena, or pill-box hydatid of Hunter.  It consists
of a  globular bag, closed at  all  points,  containing a  limpid fluid,
capable of growth,  and  of reproduction by the development of
gemmules from the inner surface  of the sac.   The  Echinococcus is
also nourished by direct absorption into the walls of the globular sac
 of which it consists.
   Some difference may be noticed  as regards  the nature of the  food
 in animals and plants.   The  former derive their nutriment entirely
 from the organized world, unless, indeed, we  suppose that the nitro-
 gen absorbed in respiration  contributes to their sustenance.   Plants
 appropriate inorganic elementary  matters  for food,  as carbon,  car-
bonic acid, ammonia, &c.  " Inorganic matter," says Liebig,  " affords
food to plants;  and they, on the other hand, yield the means of  sub-
sistence to  animals.   The conditions  necessary for animal and vege-
table nutrition are essentially  different.   An animal  requires for its
development, and for the sustenance of  its vital functions, a certain
class of substances which can only be generated  by  organic beings
possessed  of life.  Although  many animals are entirely carnivorous,
yet  their primary nutriment must  be derived from  plants; for the
 animals upon wThich they subsist receive their  nourishment  from
 vegetable   matter.   But plants find new nutritive material only in
inorganic  substances.   Hence  one  great end of vegetable life  is to
 generate matter adapted for the nutrition  of animals out of inorganic
 substances which are not fitted for this purpose."
   The  nutrient fluid, however formed, is distributed  throughout the
 textures of the plant, or animal, by vital  or physical forces,  or by the
junction of both ; and the function, by which this is effected, is called
 Circulation.  In plants, this function is very simple, and is performed
 without the agency of a propelling organ ; but, in the greatest number
 of animals, such an organ, a heart, is the main instrument in the dis-
 tribution of the blood.  In animals, then, there is a true circulation ;
 the fluid setting out from, and returning to, the same  place.  But, in
 plants, the fluid is  found to circulate, or rotate, within the interior
 of cells, as in Chara and Vallisneria, the  fluid of one cell  not  com-
 municating with  that  of the  adjacent ones, or to pass up from the 
44          RESPIRATION.—SECRETION.—GENERATION.
spongioles in an ascending current, and  to descend in another set of
vessels.
   But in many simple animals, some entozoa, for example, and poly-
gastrica, there is no good evidence of the existence of any circulation
at all; their textures imbibing the fluid in which they live.
   The presence of atmospheric air is necessary to the existence of all
organized beings.   The  air both passes  by endosmose  into their
nutrient fluids, and receives from  them certain deleterious gases de-
veloped in their interior.  The function,  by which the fluids are thus
aerated, is called Respiration.   In plants, the introduction of  atmo-
spheric air conveys  nutriment  to  the  organism; carbonic acid and
ammonia are thus introduced; the former is decomposed, its carbon
is assimilated, and  its oxygen is exchanged for a fresh supply of
atmospheric air.  As the agent in the decomposition of the carbonic
acid is light, it is evident that  the generation  and the evolution of
oxygen can  take place  only in the day-time.   Consequently, during
the night, the carbonic acid,  with which the  fluids  of the  plant
abound,  ceases to  be decomposed, and is  exhaled  by  its  leaves.
Hence, plants  exhale oxygen in the day-time, and carbonic acid at
night.
   In animals, carbonic acid accumulates in the blood during its cir-
culation ;  and, when the atmosphere  is brought to  bear upon  the
capillary vessels containing  the  blood  charged with this gas, a mix-
ture takes place through the delicate walls of the vessels, the  atmo-
spheric air passing in, and carbonic acid, with nitrogen and oxygen,
in certain proportions, escaping.   Thus the  evolution  of carbonic
acid,  and  the  absorption of oxygen and nitrogen, are the character-
istic features of respiration in animals.
   It is highly interesting to notice, how plants are thus subservient to
the well-being of animals, in the  respiratory function, as well as in
preparing nutriment for  them.   By their respiration they serve to
purify the air for animals ;  for, in  absorbing  the carbonic acid from
the atmosphere,  they are  continually depriving  it of  an element
which, if  suffered   to  accumulate  beyond  certain bounds,  would
prove destructive to  animal life.
   From the fluids of animals and plants, certain materials are sepa-
rated  by a singular  process, nearly allied in  its mechanism to  nutri-
tion, and called the function of Secretion.  The secreted  matters are
various, and have very different ends: in some cases being destined
for some  ulterior purpose  in the  economy; in  others, forming an
excrement, the continuance of which in  the organism would be pre-
judicial to it.
   The function, which has for its  object the propagation  of the spe-
cies,  Generation, presents many points  of resemblance in plants and
animals.   In the former it is cryptogamic, or phanerogamic •  in the
latter, non-sexual, or sexual.  In  the phanerogamic and  sexual  the
junction of two kinds of matter furnished by the parents is necessary
to the development of fertile  ova.  In the cryptogamic and non-
sexual generation, the new individual is developed by a separation of
particles from the body of the parent, by which the new formation is 
VOLITION.—SENSATION.
45
nourished until it has been so far  matured as to be capable of an
independent existence.
  The functions, hitherto  enumerated,  may  be called  organic, as
being common to all  organized beings ;  but there are others which,
as being  peculiar to, and  characteristic of, animals, may be appro-
priately designated  animal  functions.
  The prominent characteristic of animals is the enjoyment of  Voli-
tion or Will, which implies necessarily the possession of Consciousness.
Our knowledge of the share which consciousness and the will have
in the production of certain  phenomena of animal life,  is derived
from the  experience which each person has of his own movements,
and a comparison of them  with the actions of inferior animals.   We
are conscious  that, by a certain  effort  of the mind, we  can  excite
our muscles  to action ;  and when we see precisely similar  acts per-
formed by the lower creatures, with all the  marks of a purpose, it is
fair to infer that the same process takes place in  them as in ourselves.
Moreover, we learn  by experience, that  injury or  disease of  the
nerves, which  are distributed to  our muscles, destroys the power of
accomplishing a  certain act, but does not affect the desire or  the
wish  to perform it: and  experiments tell us that the division  of the
nerves of a limb in  a lower animal destroys  its power over that
member ;  while its ineffectual struggles to move the limb  obviously
indicate that the will itself  is not affected by the  bodily injury, though
its powers are  limited by it.
  Again,  certain  external agents are capable of affecting the mind,
through certain organs, thus giving rise to Sensations.  Light, sound,
odour, the sapid qualities  of bodies, their  various mechanical  pro-
perties, hardness, softness,  &c, are respectively  capable of producing
corresponding  affections  of the mind, which experience  leads  us to
associate with their exciting causes, and which may be agreeable, and
produce pleasure, or the reverse, and give rise to pain.
  In a similar  wTay to that  by which we learn  that the will stimulates
our muscles through the  nerves^ we can ascertain that the nerves are
the channels through which our sensations also are excited.  " Certain
states  of  our bodily  organs are  directly followed by certain  states
or affections  of our mind ;  certain states or affections of our mind are
directly followed by certain states of our bodily organs.   The  nerve
of sight, for  example, is affected  in a certain manner; vision, which
is an  affection, or  state  of the mind, is its consequence.   I will to
move my hand ; the hand  obeys my will so rapidly,  that the motion,
though truly  subsequent,  seems  almost to accompany my volition,
rather than to follow it."   (Dr.  Brown.   Philosophy of the Human
Mind, p.  106.)
  And in all the  inferior animals, possessed of like organs, there can
be no doubt that sensations may be produced similar to those which
arise in the human mind. In many of them, indeed, the sense of sight,
hearing, or smell seems  much more acute  than in man,  and affords
examples of a beautiful and  providential provision  for the peculiar
sphere which the creatures  are destined  to occupy.  The unerring
precision  of the beast or bird of prey in pouncing upon its victim—
• 
46
MIND.—SOUL.—INSTINCT.
the accuracy with which  the hound tracks by its scent the object
of its pursuit—or, the  quickness  with  which most  of our  domestic
animals detect sounds  and judge  of their direction, are  familiar
illustrations of the superiority of these senses in animals whose gene-
ral organization is inferior to that of man.
  There are few  animals, however  small and insignificant,  in which
we  cannot recognize  evidence of a controlling  and  directing will.
But even  in those few, in which  voluntary movements are not dis-
tinctly to be discerned, the presence of a special system of organs,
with which in the higher  animals volition  and sensation  are  associ-
ated, namely, a nervous system, serves  as a characteristic distinction
from plants.
  A power of perception, and a power of volition, together constitute
our simplest idea  of Mind ; the one excited  through certain corporeal
organs,  the other  acting on the body.   Throughout the greatest part
of the  animal  creation  mental power  exists, ranging from this its
lowest degree—a  state  of  the blindest instinct, prompting the animal
to search for food—to the docility, sagacity, and memory of the brute ;
and to its  highest  state, the reasoning powers of  man.
  The phenomena of Mind,  even in their simplest degree  of deve-
lopment, are so  distinct  from anything which observation  teaches
us to  be produced by material agency, that we  are  bound  to refer
them to a  cause different from that to which we refer the phenomena
of living bodies.  Although associated with  the  body by some un-
known  connecting link, the  mind works quite independently of it;
and, on the  other hand, a large  proportion  of  the  bodily acts  are
independent of the mind.  The immortal Soul of man, divina parti-
cula aura, is the  seat of  those thoughts and reasonings, hopes and
fears, joys and sorrows, which, whether as  springs of action, or mo-
tions excited by passing events, must ever accompany him  through
the checkered scene  in which he is destined to play his part during
his  earthly career.
  Although the animals,  inferior to man, exhibit many mental acts
in common with him, they are devoid  of all  power of abstract rea-
soning.   "Why  is it," says Dr. Alison, "that  the monkeys, who
have been observed to assemble about the fires which savages have
made  in the  forests, and been gratified by the warmth, have  never
been seen to gather sticks and rekindle them when expiring?  Not,
certainly,  because they are incapable  of  understanding that the  fire
prehended, in order that the action of  renewing the fire may be sug-
gested by what is properly called an effort of reason."
  Yet animals are  guided by Instinct  to the performance of certain
acts  which have reference to  a  determinate  end :  they construct
various  mechanical contrivances,  and adopt  measures of  prudent
foresight to provide for  a  season  of want and difficulty.   None of
these acts could be effected  by man without antecedent reasoning
experience, or instruction.   But animals do them without  previous 
       MOTIONS OF PLANTS.—IMPORTANCE OF PHYSIOLOGY.     47

assistance; and the young and inexperienced are as  expert as those
which have frequently repeated  them.   " An  animal separated im-
mediately after its birth from all  communication with its kind, will
yet perform every act peculiar to its species, in  the same manner, and
with the same precision, as if it  had regularly  copied their example,
and  been  instructed by their  society.   The  animal  is  guided and
governed by this principle alone ;  by this all its powers are limited,
and to this all its actions are to be ultimately  referred.  An animal
can  discover  nothing  new; it can lose nothing old.   The beaver
constructs  its habitation,  the  sparrow its  nest, the  bee its  comb,
neither better nor worse than they did five thousand years ago."
   In plants there is no nervous system; there are no mental pheno-
mena.  The motions of plants correspond in some  degree with those
movements of animals in which  neither consciousness nor nervous
influence  participates.   Such  movements are  strictly organic, and
result from physical changes produced directly in the part  moved.
Amongst the most interesting examples of these movements are those
of the Mimosa pudica, the Dionaa rnuscipula, and the Berberis.
   III. It is the province of Physiology to investigate the ways  in
which the  functions of living beings are effected ; and this investiga-
tion naturally involves the examination of their mechanism, of the
chemical constitution, and of the properties of their  component tex-
tures.   The study of Anatomy must always accompany that of Phy-
siology, on the principle that we must understand the construction of
a  machine before  we can comprehend the way in which it works.
The history of physiology shows that it made  no advance until the
progress of anatomical knowledge had unfolded  the structure of the
body.   There is so much of obvious mechanical design in the inti-
mate structure of the various textures and organs,  that the discovery
of that structure opens the most direct road to the determination  of
their uses.  That kind of anatomy which investigates structure with
a special view to  function may be properly designated Physiological
Anatomy.
   A correct physiology must ever be the foundation of rational medi-
cine.  He who is ignorant  of the proper  construction  of a watch,
and of the nature  of the  materials of which  it is made, could not
find  out in what part its actions were faulty, and would therefore  be
very unfit to  be entrusted with repairing it.   In medicine, the first
step towards the cure of disease is to find out what the disease is and
where it is situate  {diagnosis).   Without a knowledge of the  offices
which various parts fulfil  in  the animal  economy,  our  search  to
determine what organ  or function is  deranged must be most vague
and  indefinite.  Pathology is  the physiology  of disease ; and  it is
obvious, that no  pathological doctrines can command confidence,
which are  not founded upon accurate views of the natural functions.
It is also certain that improvements in pathology must follow in the
wake of an advancing physiology.
   The  practice  of medicine and surgery abounds with examples,
illustrating the immense  benefits which  physiology has conferred
upon the healing  art.   The great advance which has been  made 
48     MOTIONS OF PLANTS.—IMPORTANCE OF PHYSIOLOGY.

of late years in the pathology  of nervous  diseases, is mainly owing
to the discoveries of  Bell, and many others, in the functions of vari-
ous nerves, and the general doctrines of nervous actions.   We may
instance the case of the facial nerve—the portio dura of the seventh pair.
It was supposed formerly that this nerve was the seat of that painful
disease, called tic douloureux,  and section  of  it has been performed
for the relief of the patient.   It is now known that this nerve could
not be the seat of a very painful disease, for  it is itself, in  a very
great degree, devoid  of sensibility.  It need  hardly be added, that
the operation is discarded.
  The dangerous  disease, to which many children have  fallen vic-
tims, laryngismus stridulus or  crowing  inspiration, although admira-
bly described by practical physicians, was never properly understood
until the functions of the laryngeal nerves were clearly ascertained,
and  until it  had been shown that spasmodic actions may be  excited
by irritation  of a remote part, or  through a stimulus reflected from
the nervous centre.   It is now known, that this  disease has not its
seat in the  larynx, where those spasms  occur  which excite so much
alarm for the fate of  the little patient;  but that it is an irritation of a
distant part, which derives its nerves from  the same region  of the
cerebro-spinal centres with  the larynx,—that  the afferent nerves of
that part convey the  irritation to the centre,  whence it is reflected by
certain efferent nerves to the muscles of the larynx.
  The accurate diagnosis oi diseases of the heart rests entirely upon
a correct knowledge of the physiology of that organ.  This improve-
ment in medicine  may be said to date  from the time of  Harvey, for
he was the first who clearly expounded the mechanism of the central
organ of the circulation.  But the application  of auscultation  to the
exploration  of the sounds developed in its action, and  the correct
interpretation of  those  sounds  in health by  the experiments  and
observations of the last few years, have  almost completely removed
whatever  difficulties  stood in the way of  the detection  of cardiac
maladies.
   We are  not less indebted to the illustrious Englishman, who dis-
covered the  circulation of the blood, for having paved the way to a
rational treatment  of aneurismal and wounded  arteries by the  modern
operation of placing a ligature between the  heart and the  seat of the
disease or injury.   "The active  mind  of John Hunter," says Mr.
Hodgson, " guided by a deep  insight  into the powers of the animal
economy, substituted for a dangerous and  unscientific operation, an
improvement founded upon a knowledge of those laws which  influ-
ence the  circulating fluids  and absorbent  system ;  and  few of his
brilliant discoveries have contributed more essentially to the benefit
of mankind."
   In investigating the functions of the human body, the physiologist
cannot do better than follow the instructions laid down by Haller in
the preface to his invaluable work, "Elementa Physiologise Corporis
Humani."
   The first and most important step towards the attainment of physi-
ological knowledge,  is  the  study of the fabric of the human body. 
IMPORTANCE OF COMPARATIVE ANATOMY.          49
" Et primum," says Haller,  " cognoscenda est fabrica corporis  hu-
mani, cujus pene infinitae partes sunt.   Qui physiologiam ab anatome
avellere  studuerunt, ii certe mihi videntur, cum  mathematicis  posse
comparari qui machinse alicujus vires et functiones calculo exprimere
suscipiunt, cujus neque rotas cognitas habent, neque tympana,  neque
mensuras, neque materium."
   A knowledge of human anatomy alone is, however, not sufficient
to enable us to form accurate views of the functions  of the various
organs.  Before an exact judgment can be formed of the functions of
most parts of living bodies, Haller says, that the construction of the
same part must be examined and compared in  man, in various quad-
rupeds, in birds, in fishes, and  even in insects.  And, in proof of
the value which attaches to this knowledge of comparative anatomy,
he shows how, from that science, it may be determined that the liver
is the organ  which secretes bile; and  that the bile found  in  the
gall-bladder  is not secreted by, but conveyed to, that organ : for
no animal has a  gall-bladder without a liver, although many have
a liver without a gall-bladder; and, in every case where a gall-blad-
der is present, it has  such  a communication with the  liver, that the
bile secreted by the  latter may be easily transferred  to the former.
" Vides  adeo," he adds, " bilem hepate egere, in quo paretur, vesi-
cula non egere, non ergo in vesicula nasci, ex hepate vero in vesicu-
lum transire."
   And Cuvier has happily compared the examination of the compara-
tive anatomy of an organ, in its  gradation from its most complex to
its simplest state, to an experiment which  consists in  removing suc-
cessive  portions  of the  organ,  with a view to  determine its  most
essential  and important  part.   In the animal  series we see  this
experiment  performed by  the hand of nature, without  those  dis-
turbances which mechanical violence must inevitably  produce.   We
thus learn, from comparative anatomy, that the vestibule is the funda-
mental part of the organ  of hearing; and that the other portions, the
semicircular canals, the cochlea, the tympanum and its contents, are
so many additions made successively to it, according  as the increas-
ing perceptive powers of the animals render a more delicate acoustic
organ  necessary.  In  a similar  manner  we learn,  that one portion
of the nervous system, in  those  animals  in which  it  has a definite
arrangement, is pre-eminently associated with  the mental principle,
and  is connected  with, and presides  over, the other parts.   This
organ, the brain, is  always situate at the anterior or cephalic  ex-
tremity  of the animal, and  with it are immediately  connected  the
organs of the senses, the inlets  to perception.  We  soon find that
the brain exhibits a subdivision into  distinct parts ; and of the rela-
tive importance of these parts, and their connection with the organs
of sense, and with  the  intellectual functions, we derive the most
important information from the study of comparative anatomy.
   Haller further assigns the examination  of the living animal as  a
valuable aid  in physiological research.   Doubtless,  many obscure
points have  been elucidated by experiments on  living animals, and
discoveries have been made which have greatly contributed  to  the 
50
THE MICROSCOPE.
progress of physiology; but the  best physiologists are ever reluctant
to interrogate  nature  in  this way, knowing that replies  elicited  by
torture are rarely to be depended upon.  Very useful knowledge may
be derived from  observing the  play of certain  functions  in  living
animals, or in Man himself,—contrasting them in various individuals,
and noting the effects of age, sex, and temperament, and ascertaining
the influence which other conditions, natural or artificial, may exert
upon them.                                                  .    .
  The investigation of disease, both  during life and after death, is oi
great  value to enable us  to  appreciate the action  of an organ  in
health.   If, for example, as Haller remarks, a particular function be
ascribed  to a  certain part, how can there be a more favourable  oppor-
tunity of testing the accuracy of such a doctrine than by the exami-
nation of a body in which  that  part was affected with a disease, of
which the previous history was  known ?  If  the function in question
had been vitiated, or destroyed, it may be  fairly presumed to have
had its seat in the  diseased organ.   Nothing has contributed more
largely to determine  the functions  of particular nerves, than exact
histories of the symptoms during life, in  cases in  which they had
been found, after death,  in a diseased condition.
   For exploring the minute structure of various textures, the ana-
tomical elements of the body, Haller advises the use of the  Micro-
scope.   The  great  improvements which  modern opticians have  ac-
complished,  not only in  the dioptric  but  also in the mechanical
adjustments of this  instrument,  render it an invaluable  adjuvant in
physiological research.  We  shall have frequent occasion  in the  fol-
lowing pages to refer to anatomical analyses, effected by the  micro-
scope, of the utmost value to the knowledge of function.  It may,
however, be remarked, that, as  the  sources of  fallacy are numerous
even with the  best  instruments, more depends upon the observer
himself, in this kind of investigation, than in almost any other.
   The great impediment to deriving correct inferences  from  micro-
scopical observations has arisen from the discordance, too apparent,
in the narrations of different observers.  This discordance has been
the  result of a twofold cause; namely, imperfection of the  instru-
ments, and  the  very unequal  qualifications  of different  observers.
 The former cause is now almost completely removed; the latter must
remain,  while men imperfectly appreciate their own abilities for par-
 ticular pursuits.
   To make microscopical  observation really beneficial to physiologi-
 cal science, it should be done by those who possess two  requisites:
 an eye, which practice has rendered familiar with genuine appearances
 as contrasted with those produced by the various aberrations to which
 the rays of light are  liable in their passage through highly refracting
 media, and which can quickly distinguish the fallacious  from  the real
 form ; and a mind, capable of detecting  sources of fallacy, and of
 understanding the changes which manipulation, chemical reagents, and
 other disturbing causes may produce in the arrangement of the  ele-
 mentary parts of various textures.
   To these we  will add  another requisite, not more important for 
ANATOMICAL AND CHEMICAL ANALYSIS.
51
microscopical than for other inquiries; namely, a freedom from  pre-
conceived views or notions  of particular  forms of structure, and an
absence of bias in favour of  certain theories, or strained analogies.
The history of science affords  but too many instances of the  baneful
influence of  the  idola specus upon  the ablest minds; and  it seems
reasonable to expect that such creatures of the fancy would be espe-
cially prone  to pervert both the bodily and  the mental vision, in  a
kind of observation which is subject to so many causes of error, as
that conducted by the aid of the microscope.
   Finally, the  sagacious Haller  perceived how necessary  to the
furtherance of physiology is a knowledge of Organic Chemistry; and
we could adduce  many instances to prove, that the  attention, which
has of late years been paid to this  subject, has not been without its
fruit, in giving us an insight into the nature of many functions, which,
without it, we could  not have  obtained.
   In the living body the most delicate  chemical processes are un-
ceasingly  going  on,  for  the formation of new compounds and the
destruction or alteration  of old ones.   It is evident  that no progress
can  be made  in the investigation of these invisible processes, unless
we can arrive at  an exact  knowledge of the chemical  composition
of the various substances which are employed in them.
   Henceforward, in physiological research, anatomical and chemical
analysis must go hand  in hand: the former  to ascertain the minute
mechanism  of the various  processes; the  latter, to  determine the
nature of  the affinities by which the syntheses and analyses of the
living laboratory are  effected.

  In  the composition of  the  preceding chapter we have to acknowledge valuable
aid derived from the following works:—Haller, Elementa Physiologies Corporis
Humani; Barclay on Life and Organization; Roberton on Life and Mind; Prichard
on the Doctrine of a Viial Principle; Dr. Carpenter's article Life, and Dr. Alison's
article Instinct, in the Cyclopaedia  of Anatomy and  Physiology; Remarks on Skep-
ticism, by the Rev. Thomas Rennell;  Daniell's Chemistry; Graham's Chemistry.
                          CHAPTER I.

SOLID AND FLUID CONSTITUENTS OF ANIMAL BODIES.--PROXIMATE PRIN-
 / C1PLES.--SECONDARY ORGANIC COMPOUNDS.--CLASSIFICATION OF THE
  TISSUES.--DEVELOPMENT OF THE TISSUES FROM CELLS.--PROPERTIES
  OF THE TISSUES.

  Animal bodies  are composed of  solids and  fluids.   The  former
constitute the  various  textures and  viscera;  the  latter, the  blood,
lymph, chyle, and the liquid secretions of glands, contained either in
their excretory ducts or in special reservoirs.
  The solid  textures contain only about  one-fourth of solid matter,
the rest is water.   The great shrinking which they experience, when
dried, shows how much of their bulk they owe to this combination; 
52     SOLID AND FLUID CONSTITUENTS OF ANIMAL BODIES.

and parts  thus  shrunken swell  out again, and  assume their natural
condition on the addition of water.  The mummy of a large man is
of a very trifling weight.  Blumenbach possessed the entire perfectly
dry mummy of a Guanche or aboriginal inhabitant of Teneriffe, pre-
sented to  him by Sir Joseph Banks, which, with  all its muscles and
viscera, weighed only seven pounds and a half.
  Water is one of the most important  constituents of animal bodies.
It forms four-fifths of their nutrient fluid, the blood ; and it gives more
or less of  flexibility and softness to the various solid textures.   The
loss of it in great quantity speedily puts a stop to  vital action, as may
be easily shown in the lower animals; and some animalcules, in which
all appearance of life may have ceased on being  deprived of it, will
revive on  its being supplied to  them again.   It is a solvent of many
organic matters; some also are suspended in  it: it is, therefore, a
valuable medium for  conveying these  substances to the  several tex-
tures and  organs.   It plays a most  important  part in  the various
chemical operations of the  body; and  its addition to, or subtraction
from a particular compound is capable of converting it into a substance
of very different properties.
   By anatomico-physiological analysis  we separate the solids and fluids
of the body into their various  kinds, and classify and arrange them
according to their characters and properties.
   By chemical  means we  obtain  from them a  class  of substances,
called 'proximate principles, substances  but one step removed from the
organized tissue, some of which are  held in solution in the blood.
These, in combination with sulphur,  phosphorus, and other simple
substances (incidental elements), and  salts, form the material out of
which the organized tissues are framed.
   The  general  chemical constitution  of these proximate principles
has already been discussed in the Introduction ;  and they have been
distinguished from another class of organic  substances, the secondary
organic compounds, among which wTe  must  particularize those which
are formed by chemical action  in the living organism, from materials
furnished by it.  These are found in various secreted fluids, and are
easily obtained  from them, either  by  spontaneous separation, or by
simple chemical means ; and they must not be confounded with a vast
variety of compounds, which the chemist can create at will both from
them and from the proximate principles,  through the affinities of vari-
ous chemical substances for them.
   The following  table contains a list of substances which,  in  the
present state of our knowledge, may be  properly assigned to the two
classes of organic compounds, to which allusion has been made:
   PROXIMATE PRINCIPLES.
Albumen,"^
Fibrine,  C Compounds of Proteine.
Caseine,  j
Gelatine.
Chondrine.
Elaine.
Stearine.
Margarine.
Haematosine.
Globuline.
SECONDARY ORGANIC COMPOUNDS.
Urea;            ~i .   ,  ...
UricorLithicacid;5inthelrine'
Cholesterine; in the Bile.
Biliary matters.
Pepsine; in the Gastric Juice.
Sugar of milk.
Lactic acid. 
PROXIMATE PRINCIPLES.—ALBUMEN.
53
   Of the Proximate Principles.—1. Albumen.—This substance is so
called from the white colour it possesses in the solid state. It is very
readily obtained from  the white of egg, ovalbumen.  In the human
body it exists in two states:  fluid, being dissolved  in  the serum of
the blood, and in some of the secretions:  and  solid, forming certain
of the tissues, which  are thence called albuminous tissues.  These
are, the brain,  spinal  cord and nerves, and the mucous membranes;
it also enters into the composition of the muscles, and of the  aqueous
and vitreous humours of the eye.  It is also contained in the effusions
of serum or pus, which are the products of disease.
   Albumen may be readily made to pass  from the  fluid to the solid
state, or to coagulate, by the influence of certain reagents; but it has
no spontaneous tendency to assume the solid form, except by the loss
of the water which is combined with it.  By evaporating white of
eggs, at a temperature not  exceeding 120°, its water  is driven off,
and solid albumen, in the  form of a yellowish transparent brittle
mass, is obtained with all its properties  unimpaired.   If a  solution
of albumen, as  serum  of the blood, be exposed to a  heat  between
140° and 150°,  it coagulates, and then it becomes insoluble in water.
   The mineral  acids have the property of coagulating albumen.   Of
these, that which is most used in medical practice is  the nitric, a drop
or two of which will  readily detect a  small quantity of albumen dis-
solved in a clear fluid, by rendering it more or  less opaque.   Alcohol
also has this property ; and hence any albuminous textures submitted
to its influence become  hardened  and condensed.   Bichloride of
mercury exercises a similar  influence, and is a delicate test for albu-
men.  It was Orfila who first employed this proximate principle as an
antidote to the  poisonous effects of the bichloride,  which combines
with the albumen and is by it partially converted  into calomel.   Ac-
cording to Peschier, the white of one egg is sufficient to render four
grains of the poison innocuous.
   Another delicate  test for albumen is the ferro-cyanide of potassium,
which will precipitate  it from solution, provided  a  little acetic acid
have been previously added, in order  to neutralize the  soda in com-
bination with  it.   Albumen is also  precipitated from solution  by
tannin.
  Albumen coagulates at the negative pole of the  galvanic battery,
or at both poles, when a strong battery is employed.
  Many other reagents will coagulate this principle, but enough have
been mentioned for  all practical purposes.
  It often happens that albumen is carried off from the system in large
quantities by the urine.  By any of the means above-mentioned, its
presence in that fluid may be detected.  When heat is used,  it will
always be advisable to ascertain previously whether the urine be acid
or alkaline; for the presence of alkali  prevents the  coagulation of
albumen by heat.   Hence  it is a good  rule, in testing for this sub-
stance, to employ both heat and nitric acid.
  Albumen is soluble in  caustic alkalies.
  The existence of sulphur as a  constituent  of albumen, is shown
by the blackening of silver  that has remained  long it contact with it. 
54                '          FIBRINE.
  According to Mulder, this principle yields the following elements
in one hundred parts :
                Nitrogen.....1583
                Carbon......54-84
                Hydrogen.....7-09
                Oxygen......21-23
                Phosphorus.....033
                Sulphur......0-68
                                             100-00'
  2.  Fibrine.—This proximate principle forms the basis of the mus-
cles ; and is, therefore,  the chief constituent of the flesh of animals,
in which it is found in the solid form.  It exists in a state of solution,
in the serum of the blood, forming, with that fluid, the liquor san-
guinis of Dr Babington, in the lymph, and in the chyle.  It is a con-
stituent of  the exudation (coagulable lymph) which forms  on certain
surfaces, as the result of the inflammatory process, and it  sometimes
occurs in dropsical fluids.
  Fibrine is distinguished from the other proximate principles, by its
remarkable property of spontaneous coagulation. When blood is drawn
from  a vein, and allowed to rest, it speedily separates into a solid por-
tion,  the crassamentum  or clot, and a fluid portion, the serum.  The
former consists of fibrine, with the red particles entangled in it during
its  coagulation.   It  sometimes happens, that, owing  to an  unusual
aggregation of  the red  particles  together, and to  their more speedy
precipitation, a portion  of fibrine on  the  surface  coagulates without
enclosing the colouring matter.   A yellowish-white layer forms the
upper stratum of the  crassamentum, and  this is  called the buffy coat
or inflammatory crust.  It is an example of nearly colourless fibrine,
but contains also peculiar globules.
  We may obtain fibrine in a state of considerable purity,  by cutting
the crassamentum  into slices, and washing them in clean water so as to
dissolve out the colouring matter; or by briskly stirring, with a bundle
of twigs, blood as it flows from a vein: the fibrine coagulates upon the
twigs in small portions, which, being washed, afford good  specimens
of colourless fibrine ; by digesting afterwards in alcohol and ether, the
adhering impurities are got rid of.   Another  mode of  obtaining this
substance is that suggested  by Muller, namely, to  filter frogs' blood,
the red particles of which being  too large  to permeate the pores  of
the filter, the liquor sanguinis passes through in a colourless state, and
its  fibrine coagulates free from colouring matter. Sometimes we obtain
masses of  fibrine, great part of which is colourless, from the cavities
of the heart, and from the large arteries, after  death.   It is also  accu-
mulated, and disposed  in a peculiar lamellar form, in  the sacs of old
aneurisms.
   Pure fibrine is  white, tasteless, and inodorous;  it tears into thin
laminse, which are transparent, and it is remarkably elastic ;  by dry-
ing, it becomes yellow, hard, and brittle, and loses three-fourths  of
its weight, but imbibes water  again when moistened:  it is insoluble
in both hot and cold water,  in alcohol, and in ether.  By lono-.COn-
tinued boiling in water, its  composition is  changed, and it  becomes 
CASEINE.
55
soluble.   Strong acetic acid converts it into a jelly-like mass, which
is sparingly soluble in water.  All the alkalies dissolve fibrine.  Any
of these solvents of fibrine will prevent  the  coagulation  of blood,
which has been allowed to drop into it as it flows from the  blood-
vessels.
  Fibrine is dissolved by cold concentrated muriatic acid,  and, if
kept at a cool temperature for  twenty-four hours, the solution acquires
an indigo-blue colour.   Albumen, similarly treated, assumes  a violet
colour.
  Caustic potash, common  salt, carbonate  of potash,  and many neu-
tral salts, when mixed in certain quantities with the blood, have  the
property of preventing the coagulation of its fibrine.*
  We subjoin the ultimate analysis of fibrine, as given  by Mulder.  In
one hundred parts, he found
                Nitrogen.....15-72
                Carbon......54-56
                Hydrogen.....6-90
                Oxygen......2213
                Phosphorus •                    0-33
                Sulphur......0-36

                                             100-00
   3.  Caseine.—This principle has many properties in common with
albumen and fibrine.   It is found abundantly in milk; its occurrence
in other fluids  has not been positively determined.  The curd, which
is formed by heating milk in which a free  acid existed, consists of  a
combination of caseine wTith the acid.  Heat alone will not effect the
precipitation of the curd ; but the addition of a little acid of any kind
will occasion it.
   When dilute sulphuric acid is added  to skimmed milk, a  precipi-
tate occurs, which is sulphate of caseine.  By digesting the clot, thus
formed, with water and carbonate of lime, the acid combines with the
lime, and the caseine, set free,  dissolves  in  the wrater, and may be
obtained by evaporation.
   Caseine is coagulated very perfectly by the  action  of rennet (the
fourth or  true  digesting  stomach of the  calf) aided  by heat.  This
power of coagulating caseine  is not to be attributed to the acid of the
calf's  stomach, but to  the organic principles (pepsine) resident in it;
for the power  remains after all  evidence   of acid reaction has been
removed.   This is one of the most powerful  agents in causing the
coagulation of  caseine, and it has been employed in domestic economy
for the manufacture of cheese, which consists of the curd mixed  with
butter, compressed and dried.   So perfect is the coagulating power
of rennet, that  not a particle of caseine in milk submitted to its action
will remain uncoagulated.
   Caseine comports itself with reagents in a manner very similar to
albumen.  In the  coagulated state it is insoluble in water, but soluble
in  liquor potassse.   It is not precipitated by heat alone, in which
respects it differs  from  albumen. Acetic acid, which will not precipi-
  * See further observations on the results of the examination of  fibrin by the micro-
scope, in the chapter on the Blood. 
56
PROTEINE.
tate albumen, causes the coagulation of caseine, and an excess of acid
again dissolves it.
  Caseine contains sulphur, but no  phosphorus.
  Mulder's ultimate analysis is as follows:
                Nitrogen.....15-95
                Carbon......55-10
                Hydrogen.....6>97
                Oxygen   ...... 2162
                Sulphur.....0-36
                                             100-00

  If albumen, or fibrine, or caseine be dissolved in a moderately strong
solution of caustic potash, and exposed for some time to a high tem-
perature, it becomes decomposed; and if acetic acid be now added,
a precipitate  takes place of a gelatinous translucent matter.   This
substance was discovered by Mulder, and  named by him Proteine
(from the  Greek verb Tteatswo, I am first), as being the radicle of these
proximate principles; or, in the language of Liebig, the commence-
ment and  starting-point of all the tissues;  so that it appears that each
of these principles  is composed  of  this  substance, with the addition
of certain proportions of phosphorus, sulphur, or of both.   In the
process by which it  is obtained,  the object is to remove the sulphur
and phosphorus and any salts which may  be mixed with it, and to set
the proteine free.
  Proteine, when dried,  forms a hard, brownish-yellow substance,
without taste, and insoluble in water and alcohol.  It attracts moisture
from the air, and swells out again into a gelatinous mass when moist-
ened.  It is soluble in  all acids, when diluted; and forms combina-
tions with them, which are with  difficulty,  or not at all,  soluble in
excess of acid.  It is also dissolved in dilute alkalies, or in solutions
of alkaline earths.
  The ultimate analyses of proteine, according to Mulder, from one
hundred parts gives as  follows:
                Nitrogen   .   .    .   .     •   16-01
                Carbon......55-29
                Hydrogen.....7-00
                Oxygen......21-70

                                              100-00
  The following table exhibits the  relations which albumen, fibrine,
and  caseine bear respectively to proteine:
    Albumen of serum = 10 eqts. Proteine -f- 1 eqt. Phosph. + 2 eqts. Sulph.
    Albumen of Egg  = 10 eqts. Proteine + 1 eqt. Phosph. + 1 eqt.  Sulph.
    Fibrine         = 10 eqts. Proteine + 1 eqt. Phosph. + 1 eqt.  Sulph.
    Caseine         = 10 eqts. Proteine + 1 eqt. Sulph.

  Besides the essential elements of these proximate principles  which
are obtained by their ultimate analysis, we  find certain salts  mixed
with them.   In albumen, phosphates and sulphates of earths and
alkalies and chloride of sodium ;  in fibrine,  phospate of lime ; and in
caseine, the  same salt, in the proportion of 6*24  per cent. ' As the
phosphate of  lime  is the  same as bone-earth, the  existence of it in 
GELATINE.
57
 union with the proximate principle, which forms the chief constituent
 of milk, seems to have reference to the process of ossification during
 the growth of the infant.
   Proteine, in every respect the same as that which forms the basis of
 the proximate principles just described, maybe obtained from similar
 elements in the vegetable kingdom. Gluten, which exists abundantly
 in the seeds  of the Cerealia, yields a principle which is called  vege-
 table fibrine ;  the same substance coagulates spontaneously in the newly
 expressed juice  of vegetables.  From the clarified  juices of cauli-
 flower, asparagus, mangel-wurzel, or  turnips, when  made to boil, a
 coagulum is  formed, which  cannot be distinguished  from the coagu-
 lated albumen of serum or the egg. This is vegetable albumen.  And
 in peas, beans, lentils, and  similar leguminous seeds, we find a sub-
 stance similar to caseine.  It is vegetable  caseine, which, like the ani-
 mal principle of the same name, does not coagulate by heat alone, but
 yields a coagulum  on the  addition of an  acid, as in milk.  "The
 chemical analysis of these three substances," says Liebig, " has led
 to the very interesting result, that they contain the same organic ele-
 ments, united in the  same proportions by wreight; and, what is still
 more remarkable, that they are identical in composition with the  chief
 constituents of blood, animal fibrine,  and albumen.  They all three
 dissolve  in concentrated muriatic acid with  the same  deep purple
 colour ; and, even in their physical characters, animal fibrine and albu-
 men are in no respect different from vegetable fibrine and albumen.
 It is especially to be noticed, that by the  phrase identity of composi-
 tion,  we do not here imply mere similarity ; but that, even in regard
 to the presence and  relative amount of sulphur, phosphorus and phos-
 phate of lime, no difference  can be observed."
   4.  Gelatine.—This substance exists  in a peculiar combination  with
 the tissues of which it forms a constituent, and can only be obtained
 by artificial means.   If the  cutis  or true skin, tendon,  or bone, be
 subjected to continued boiling, this substance is  obtained in  solution
 in the hot water,  and upon cooling assumes the form of a solid jelly,
 which is the more solid as the quantity  of water contained in it is less.
 The textures which  yield  gelatine are, the white fibrous  tissue, areo-
 lar tissue, skin, serous membranes, bone.  Glue prepared from hides,
 &c; size from parchment, skin, &c;  and isinglass from  the swim-
 ming bladder  of the  sturgeon, are various forms of gelatine  used in
 commerce.
   Gelatine, obtained by boiling, is in combination with a considerable
 quantity of  water: by a slow and  gentle heat  this may be driven off,
 and the gelatine obtained in a dry state.   Dry gelatine is hard, trans-
parent, colourless, without smell or taste,  of neutral reaction ; in  cold
water it softens and  swells up, and dissolves  in warm water.   It is
insoluble  in alcohol  and ether, but very soluble  in the  dilute  acids
and alkalies.  When  tannin, or the tincture  or infusion of  galls, is
added to its solution in water, a brownish  precipitate is thrown down
—the tanno-gelatine, which  may be precipitated  from a  solution of
gelatine in 5000 times its weight of water.
   The process of tanning leather results from the affinity of  gelatine
    5 
58
CHONDRINE.
for tannin.  The skins of the  animals having been  first freed from
cuticle and hairs by soaking in lime-water, are tanned by submitting
them to the  action of infusion of oak-bark, the strength of which is
gradually increased until a complete  combination has taken  place.
An insoluble compound is thus formed, capable  of  resisting  putre-
faction.
   According to Mulder, gelatine contains in one hundred parts,
                Nitrogen.....18350
                Carbon.....50-048
                Hydrogen.....6-477
                Oxygen.....25-125

                                            100000
to which  may be added some inorganic  material, chiefly phosphate
of lime.
   Dr. Prout  remarks, the gelatine in  animals may be said  to be  the
counterpart  of  the saccharine principles of plants ;  it being distin-
guished from all other animal substances  by its ready convertibility
into a sort of sugar,  by a process similar to that by which starch may
be so converted.  If a solution  of gelatine in concentrated sulphuric
acid be diluted with water and boiled for some time, gelatine-sugar may
be obtained  from it, on saturating  with chalk.  Again,  by boiling
gelatine in a concentrated solution of caustic alkali, it  is separated into
leucine and gelatine sugar, or glycicoll. The latter product crystalizes
in pretty large rhomboidal prisms; is colourless, inodorous, and very
sweet.   {Graham's  Chemistry,  p.  1039.  [Am. Ed., p. 700.])   It
differs from  sugar, however, in  the important particular, that it con-
tains nitrogen;  and Mulder assigns to it the following formula, C8 H.
N3 09 + 2 HO.
   Proteine cannot be obtained from gelatine ; but it seems reasonable
to infer, that it or its compounds must have contributed to the forma-
tion of the latter substance, for, in the egg, the gelatine of  the chick
cannot be derived from any other material than a compound of pro-
teine.   Scherer has shown that gelatine contains the  elements of two
equivalents  of  proteine, with three of ammonia, and  seven of water.
   5.  Chondrine is a substance in many respects similar to gelatine.  It
is obtained in a state of solution, by boiling water, from the perma-
nent cartilages and from the cornea ; also  from the  temporary carti-
lage prior to ossification; it  gelatinizes on cooling, and when  dry
assumes the appearance of glue.   It differs  from gelatine, in not being
precipitated by tannin, and in yielding precipitatesto acetic acid, alum,
acetate of lead, and the protosulphate of iron, which  do not disturb a
solution of gelatine.  It resembles the proteine compounds in containing
a minute quantity of  sulphur.
   Mulder's analysis of one hundred parts  is,
                Nitrogen.....14-44
                Carbon......49.96
                Hydrogen.....6.63
                Oxygen......28-59
                Sulphur   .    .   .    ...    0.38
10000 
IMPORTANCE OF A MIXED DIET.
59
   Respecting the remaining substances included in the list of true
proximate principles, very few words are necessary, as they will  be
more fully treated of in subsequent chapters.
   Elaine, Stearine, and Margarine are proximate principles of fat, and
are found also in the brain and nerves.  Stearine exists but sparingly,
or not at  all, in  human fat.
   Hamatosine and Globuline are the constituents of the particles, or
corpuscles, to which the blood owes its  colour.   They are  both
nearly allied to albumen,  and the latter is regarded as a compound of
proteine.
   The proximate principles which have  been described in the pre-
ceding paragraphs are constituents  of the  animal food, upon which
the human race, and the inferior creatures, to a great extent, subsist;
and the discovery that similar  principles exist in the vegetable king-
dom, also adapted for food, is of the  highest interest, as proving that
both kingdoms of organized nature are capable of affording the mate-
rials which are suited to supply the waste in the animal tissues which
is the  necessary result of their  vital actions.  The blood is the imme-
diate pabulum of the tissues ; its  composition is nearly or entirely
identical  with thern ; it is, indeed,  as Bordeu long ago expressed  it,
liquid flesh ; it contains the elements of the solids in a state  of solution
—le sang est de la chair coulante.   The proteine compounds more
immediately contribute to the formation of the blood, and, as we have
seen, may be obtained directly from that  fluid; and the  process of
nutrition  consists  in the attraction of certain of these principles from
the blood, and the appropriation of them by the textures and organs,
in a form  assimilated to that of their elementary parts.
   It is necessary to  the  support  of nutrition, that  these  proximate
principles should  be supplied in proper quantity to the blood, from
time to time, together with a due  proportion  of water; and as the
human body is composed of a variety of textures, differing in their
chemical  composition, so  a variety of food  is required  for its perfect
nourishment.  This statement, which appears most  reasonable prior
to experience, is fully borne out by the results of the various experi-
ments  on  the nutritive power of different substances,  from the time of
Papin  to  the  present  day.   No  one proximate  principle  is of itself
adequate  to  support life:  if  any  such substance  be  administered
alone to animals, they will perish sooner or later, writh signs of waste
and destruction in various textures.   This had been long  ago ascer-
tained  respecting gelatine  ; but  a commission appointed by the French
Academy  have  lately reported that  it applies equally to albumen,
caseine, or fibrine, if employed alone ; and that  neither animals nor
man should be restricted to any course of diet, which  does not contain
all the proximate elements of their frame.
  These facts should be made known to, and impressed upon all,
whose  position in society leads them to superintend the administration
of food to a  number of human beings congregated in prisons, work-
houses, or other public institutions.  A  complex machine, made up
of many different  kinds of substances, requires for its repair a corre-
sponding  variety of materials.  The  fabric  of man's body is a piece 
60
SECONDARY ORGANIC COMPOUNDS.
of mechanism compounded of divers  parts, derived  from albumen,
fibrine, gelatine, &c; and the material, which is to supply the wear and
tear that continually go on in it, ought to contain these substances.  It
is even more important for sufficient nourishment that attention should
be paid to the quality than to the quantity of the food  administered.
  By the function of  digestion, a fluid {the chyle) is prepared, which
contains  those constituents of the food that are adapted to nourish  the
body, and the  first step of the nutrient process consists in the addition
of this new supply of nutritious material to the blood.  A further stage
of this process is that whereby the several proximate principles  are
separated in order to  be applied to the  support of their appropriate
textures; as albumen, to the albuminous tissues ; fibrine, to the fibrin-
ous.   These two principles have already  appeared  in  the chyle, and
pass  with it into the blood-vessels, in which  all the changes  neces-
sary to nutrition take place.   It is  probable that gelatine is formed in
the blood, but is attracted  from it by  its  proper tissues immediately
upon  its formation, so  that it does not accumulate in it;  and this
accounts for our  not  being able to find  it in the blood.  The fatty
elements also separate in the blood, and  are destined  to  nourish  the
adipose tissue, and the nerves.  It may be fairly conjectured that  the
development and  separation  of these  principles  take place  in  the
capillary blood-vessels, because  those vessels penetrate  and play
freely among the elementary parts  of  the tissues;  and also because
the blood does not manifest a decided change in its characters until
it has passed through  that part of the sanguiferous system.
  The blood is likewise the seat of other changes, not less important
to the well-being  of the  animal economy.  As certain  particles of the
various tissues become effete and useless, they are removed either by a
direct absorbing power of the blood-vessels, or by that of certain vessels,
called lymphatics, and thus they again find their way into the current
of the circulation.  Here the elements  of the tissues, by some un-
known chemical  agency, undergo  certain transformations, and  the
secondary compounds  are formed, to be excreted from the system by
means of particular organs.   Urea and uric  acid, thus formed in  the
blood, are excreted by the kidneys ; lactic acid, by the kidneys and
the skin ; the elements of the bile,  by the  liver, &c, &c.  But whilst
it is highly probable that the effete  particles furnish materials for these
compounds, there  seems good reason to believe, that, at least with
respect to some of them, the  food  likewise  contributes immediately
to their formation.  That  this is the case with respect to the bile, is
rendered very likely by  several circumstances which cannot  be dwelt
upon  at present.
  In the present state of our knowledge it is impossible to assign  the
particular tissues  whose metamorphoses give rise to the formation of
certain secondary compounds.   Dr. Prout has expressed the opinion
that  urea is derived  from the gelatinous, and uric  acid  from  the
albuminous tissues.   And it may be conjectured that the fatty tissues
afford material for the formation of some of the constituents of  the
bile.
  As each of these secondary  organic compounds forms a component 
THE TISSUES.
61
part of some special secretion, it would be  premature to do more  at
present than  allude to them ;  we,  therefore, postpone the further
investigation of them to those parts of the work where the respective
secretions will be treated  of.
   Classification  and properties of the tissues.—From  the proximate
principles, the various textures are  produced by  the  development of
particular organic forms.  It has already been stated, that the simplest
form which animal matter  assumes  in its organization is  that of a
nucleated cell.   Such  cells exist in vast  numbers, free  and isolated,
floating in the blood, but  having occasionally a remarkable tendency
to cohere.  These are  the red particles  of the blood, which perform
some very important office in reference to that fluid and the different
tissues, as appears from the serious  results  consequent upon a  great
deficiency of  them.  They may be considered to be among the sim-
plest products of organization.
   In the  embryonic state  all the tissues are composed of cells,  analo-
gous in structure to the corpuscles of the blood.   These are  united
together by a more  or less abundant intercellular substance, which is
either homogeneous {hyaline), minutely granular, or indistinctly fibrous.
Some tissues  retain, as their permanent character, this cellular struc-
ture ;  whilst  in  others the cells undergo certain  metamorphoses by
which they are converted into other forms, which constitute the ana-
tomical elements of the adult textures.
   It  seems impossible to devise a  satisfactory  arrangement  of  the
tissues, which shall be based on one  principle of classification.  The
following table  has been  constructed chiefly with  the object of pre-
senting to the reader a general view of the various tissues, the  anato-
mical characters of  which will be discussed in subsequent pages.
             TABULAK VIEW OF THE TISSUES OF THE HUMAN BOUT.
1.  Simple membrane, homogeneous, or nearly   Examples.—Posterior layer of the
    so, employed alone, or in the formation of     Cornea.—Capsule of the lens.—
    compound membranes.                    Sarcolemma of  muscle, &c.
2.  Filamentous tissues, the elements of which   White and yellow fibrous tissues.
    are real or apparent filaments.              —Areolar tissue.
3.  Compound membranes,composed'of simple   Mucous membrane.—Skin.—True
    membrane, and a layer  of cells, of various     orsecretinsglands.—Serous and
    forms  (epithelium  or  epidermis),  or of     synovial membranes.
    areolar tissue and epithelium.
4.  Tissues which retain the primitive cellular   Adipose tissue.—Cartilage.—Gray
    structure as their permanent character.       nervous matter.
5.  Sclerous or hard tissue.                   Bone.—Teeth.
6.  Compound tissues.
    a. Composed of tubes of  homogeneous   Muscle.—Nerve.
      membrane, containing a peculiar sub-
      stance.
    b. Composed of white fibrous tissues and   Fibro-cartilage.
      cartilage.

   The first texture  enumerated  in this table is  an example  of  the
simplest  form  of membrane.   Its principal  character  is extension;
but as to  the arrangement of its  ultimate  particles nothing is known,
for under the  highest  powers  in the microscope it appears homoge-
neous, that is, without  visible limits to its particles, or, at most, irregu-
larly  and  very indistinctly granular.  The  capsule of the lens,  the 
62
THE TISSUES.
posterior layer of the cornea,  and the walls  of the primary organic
cells, are composed of it; and  it is employed in  forming muscle,
nerve, and the adipose and tegumentary tissues.
  The filamentous tissues are extensively used for connecting different
parts, or for associating the elements of other tissues.  The ligaments
of joints, for instance, are composed of the white or yellow fibrous
tissues; and areolar tissue surrounds and connects the elementary
parts of nerves and  muscles, accompanies and supports the blood-
vessels, and unites the tegumentary tissues to  their subjacent parts or
organs.
  Under the title compound membranes we include those expansions,
which  form  the external integument of the body,  and are  continued
into the various  internal  passages, which, by their involutions, con-
tribute to  form  the  various secreting organs  or glands.  These are
composed of the simple  homogeneous  membrane  covered by epi-
dermis or epithelium, and resting upon a layer of vessels, nerves, and
areolar tissue in great variety ; and they constitute the skin and mucous
membranes, with the various glandular organs which open upon their
surface.  Hairs and nails, being hardened cuticle, are justly regarded
as appendages to the former.
  To these we may add those remarkable membranes,  composed of
areolar tissue and a  thin indusium of epithelium, which are employed
as mechanical aids to motion.  These  are the serous membranes which
line the great cavities of the body, and the synovial membranes, which
are interposed between the articular extremities of the  bones in cer-
tain joints, or are connected with and facilitate  the  motions of tendons.
  The tissues which compose the fourth class have no common cha-
racter, except their  adherence, in the adult  state, to  the  primitive
cellular structure, and  their analogy in that particular with the vege-
table tissue.   Although a  certain agreement, in morphological charac-
ters, allows these textures to be grouped together, none  can be  more
dissimilar as regards their vital endowments.   They differ materially
as to the degree of cohesion between their cells:  in cartilage there is
generally  a firm and  resisting intercellular  substance; in adipose
tissue, the  interval  between the cells is  occupied  by areolar tissue
and  blood-vessels, which are foreign to the true adipose cells ;  and,
in the gray nervous matter, vessels  and  nerve tubes exist between
the  cells.
  The sclerous tissue (0x^05, hard), contains a large proportion of
inorganic material,  to  which it  owes  its hardness;  it differs  very
materially from  all the other tissues, excepting cartilage and  fibro-car-
tilap;e, which, as regards  hardness, might be classed with it.
  The compound tissues are those, the elementary parts of which are
made up of two distinct tissues.    Thus both muscle and nerve are
composed of parallel  fibres or threads, each  fibre being compound ;
in muscle, it is composed of homogeneous membrane, disposed like
a tube, containing a fleshy {sarcous) substance, arranged in a particu-
lar manner,  which is the seat of the vital  properties of the  tissue •
and, in nerve, the fibres  are  composed  of similar tubes of homoge-
neous membrane  containing an oleo-albuminous  substance, neurine. 
           DEVELOPMENT OF THE TISSUES FROM CELLS.        63

Fibro-cartilage is also properly a compound texture, being made up
of white fibrous tissue and  cartilage;  it is employed almost exclu-
sively in the mechanism of the joints of the skeleton, in which it is
associated with bone, cartilage, and ligaments.
   Of the development of the  tissues from cells.—At the earliest period
of embryonic  life, the process of organization has advanced to so
slight an extent, that the variety of textures above described has not
yet appeared.
   The prevailing mode, in which  the  development of animals takes
place, is by the formation, within the  parent, of a body containing the
rudiments of the future being, as well as a store of nutrient material
sufficient to nourish the embryo for a  longer or shorter period.   This
body is called the ovum or egg.  It is of that form which, in a former
page (p. 32, fig. 1), has been described and delineated as the simplest
which  organization  produces.   It  consists  of  a vesicular body filled
by a fluid,  and enclosing another, within which is  a third, consisting
of one or more minute, but clear and distinct granules.  The  first, or
the vitelline membrane of the ovum,  is the wall of a cell; it is com-
posed of homogeneous membrane : the  second, or the germinal vesicle
of the  egg, is the nucleus of the first:  and  the third, which is called
by embryologists the germinal spot, is  a nucleolus to the second.  It
appears, from  the researches of  Wagner and Barry, that the nucleus
or germinal vesicle precedes the formation of the vitelline membrane,
but the precise relation as to the period of its formation of the nucle-
olus or  germinal spot to the nucleus has  not  yet been satisfactorily-
made out.  The germinal vesicle and  spot become the seat of a series
of changes, which give rise  to the development of new cells, for the
formation of the embryo.
   At this period  the  embryo  consists  of an aggregate of cells, and
its further growth takes place by the development of new ones.  This
may be accomplished in two ways: first, by the development  of new
cells within the old, through the subdivision of the nucleus into  two
or more  segments, and the  formation  of a  cell  around each, which
then becomes  the nucleus of a new cell, and may in its turn  be the
parent  of other nuclei ; and, secondly, by the formation of a granular
deposit between the cells, in which the development of the new cells
takes place.   The granules  cohere to  each other in separate  groups
here and there, to form  nuclei, and around  each  of these a delicate
membrane is formed, which  is the  cell-membrane.   The nuclei have
been named cytoblasts, because they appear to form the cells {xvto^
cell; faaatta,  to produce); and the granular deposit  in which these
changes take place is called  the cytoblastema.
   In every part of the embryo the formation  of  nuclei and of cells
goes on in  one or both of the ways above-mentioned ; and, by and by,
ulterior changes take place, for the production of the elementary parts
of the tissues.   The precise share which the cells take in this process
cannot be made intelligible in the present stage of our inquiry, even
if observers were agreed  in their accounts of the phenomena. It must
suffice for us now to explain,  as far as we are able, the general changes 
64         DEVELOPMENT OF THE TISSUES FROM CELLS.
that occur, and the probable office which  each part of the cell per-
forms in them.
  The changes which the cells undergo in the formation of the tissues,
may  be described under two  heads ; first, those  affecting  the  cell-
membrane; and, secondly, those in which the nucleus is concerned.
In those tissues, whose ultimate elements are fibrous, that is, consist-
ing of real or apparent fibres, as areolar and fibrous tissues, the cell-
membranes become elongated,  and so folded or divided as to give the
appearance of a subdivision into minute threads  or  fibres.   In the
tissues, which  are composed  of tubes  of homogeneous membrane
containing a peculiar substance within them, as muscle and nerve, the
cells are joined end to end, and, the partitions at each extremity being
removed, their cavities  communicate, so that they together form  a
tube,  or sheath, in which the deposit of the proper muscular or ner-
vous substance takes place.  The smallest or capillary blood-vessels
also are formed by the  coalescence  of the walls  of the  cells, not at
one or two, but at several points, owing  to their elongation,  here and
there, into pointed processes, which unite  and form the ramifications
of the vessels.
  In these examples, the nucleus  of the cell  appears to  take no part
in the formation of the tissue.   What becomes of it?  does it become
absorbed,  or does it waste away, its office having  ceased?   There is
abundant evidence to show that the  nuclei are still persistent in the
fully-formed tissues, for they have been  seen in all those enumerated
in the last paragraph.  They  are generally  altered  in  form, being
flattened and  elongated.  Henle believes that, while they retain their
peculiar characters, they are prolonged  at  either  pole  into peculiar
fibres, distinct, in anatomical and chemical characters, from  the pro-
per fibres  of  the tissue ;  he  designates  the latter Zellenfasern, cell-
fibres ; and the former Kernfasern,  nucleus fibres.   For instance, the
two elements  of areolar tissue, which will be described at a future
page, are derived, according to him, the white fibrous element, from the
cell;  the yellow, from the nucleus.   The formation of the homoge-
neous simple  membrane which  forms the basement of the skin and
mucous membrane, maybe ascribed to the flattening and fusion of the
cell-walls into one another.  The  free surface of these membranes,
wherever they may be found, whether as integuments  to the body, or
folded into glands, is the seat of a continual development of new cells,
which may have primarily sprung from  the nuclei of the formative
cells of the basement membrane.
  In other tissues the walls of the cells become thickened by a depo-
sition around  and between them, with which they  become united and
incorporated,  and  thus  an  intercellular  substance is formed.   This
substance becomes the  seat of  a further deposition, or new arrange-
ment  of particles, which, as far as we know at present, is not preceded
by the development of cells.  In cartilage, which in its simplest state
is only an aggregate  of  cells, this substance assumes a fibrous form.
In most textures, it is not improbable that  the nuclei are persistent;
in cartilage, they remain in the  cell-cavities, and  possibly contribute
to the growth and  nutrition of the  cartilage;  in bone, they  form the 
PROPERTIES OF THE TISSUES.
65
 lacunas from which  minute canals are prolonged into neighbouring
 ones, or into the vascular  channels;  and, in teeth, they are probably
 converted into the dental tubuli.
   From the preceding brief and necessarily imperfect sketch, it seems
 evident that, in the  various metamorphoses of the foetal into the per-
 fect tissues, both the elements of the cells take a part.  In no instance
 does there appear to be an  actual conversion of either cell-wall or
 nucleus into the ultimate elements of the tissues.  The cell-walls may
 be changed into a part, accessory to the complete texture, as the sar-
 colemma or sheath of the  muscular fibre; but the further  organizing
 process takes place on its outer or  inner surface.  And  the nuclei,
 likewise, may be changed  into parts,  which contribute  to the nutrition
 of the tissue ;  but not into its essential elements.  These, it must be
 remarked, are always the  product of an ulterior organizing process,
 connected chiefly with the cell-wall.
   There  seems reason to believe, that  during the organizing process
 which occurs simultaneously with the changes of the cell, a chemical
 alteration takes place; for the  cells  of cartilage  sometimes contain
 fat, and the cartilage of bone prior to ossification contains  chondrine,
 but, after the ossific  process, gelatine is found : and it is also stated,
 that the  element which may  be obtained  from the  young cells of
 areolar tissue is pyine ; whereas gelatine is yielded by the fully-formed
 tissue.
   The formation of cells does not  cease  with the  infancy of the
 organism. These minute organic elements are most important agents
 in various functions of the body at every  period of its  existence. By
 them the secretions  are separated ; and it is not improbable that they
 contribute largely to those changes  in which nutrition immediately
 consists.   They are found  floating in immense numbers in the blood,
 as well as in the chyle and lymph; and, even in diseased  secretions,
 as pus, they exist in  great quantity. In the inflammatory process, they
 are formed in great abundance ; and  in the malignant growths, which
 infest the body, so as  to manifest themselves at different parts  of it,
 such as the various forms of cancer, the same organic forms are  to be
 found.
   In short, Schleiden and  Schwann  have proved that the nucleated
 cell is the agent  of most  of the organic processes, whether in the
 plant or animal, from the  separation  of the embryo from  its parent,
 to the development,  growth,  and nutrition of  the adult individual.
   Properties  of the  Tissues.—The fully-grown tissues manifest dif-
 ferences among  themselves, not merely by their anatomical characters,
 but by their properties.  These may be conveniently subdivided into
physical and vital.   Strictly speaking, this is a distinction without a
 difference, for doubtless all the properties of animal tissues may be
 ascribed to the peculiar arrangement of their particles, and  are, there-
 fore, physical.   Our reasons for adopting the division  will appear in
 explaining the nature of these properties.
   The physical properties of the tissues are those which are dependent
 simply on the peculiar arrangement or mode of cohesion of their con-
 stituent particles, as  well as upon their chemical constitution, and will 
66          ELASTICITY.—EXTENSIBILITY.—POROSITY.

manifest themselves in the  dead, as distinctly as in the living, texture.
The elasticity of yellow ligament, for instance, is  as evident in a spe-
cimen which has been preserved in spirits for years, as in one taken
fresh from the body.   The vital properties are those which exist only
during  life, and which cease  immediately when molecular life has
ceased.   A muscle will contract only so long as it is  alive ;  when
dead, it refuses to  respond  to  those stimuli, which so easily excited
it while living.
  The most striking physical property which certain tissues manifest,
is that of elasticity, in virtue of which the tissue reacts, after a stretch-
ing or a compressing force has been withdrawn. The yellow ligament,
which constitutes the  ligamenta subflava of the  vertebral laminae, is
as elastic as India-rubber;  the middle coat of arteries manifests quite
as much elasticity.   Cartilage is flexible and  elastic; and  is exten-
sively employed, in  consequence  of  this  property, to encrust the
articular extremities of the bones, for their protection in the move-
ments of the joints.
  The existence of elasticity implies that of extensibility.   All elastic
tissues must admit  of being stretched before they can manifest their
elastic reaction.  But some textures  are  extensible without  being
elastic.  Such tissues yield only to along-continued extending force;
and, in  the healthy  state, they are capable of resisting such a force of
tension  for a considerable period.  The resistance which a fibsous
membrane offers to  the enlargement of an organ  or tumour,  which  it
covers,  illustrates this statement:  the pain felt  in hernia humoralis
or inflammatory enlargement of the testicle, is doubtless due to the
resistance of its fibrous coat  to the swelling of the  soft substance  of
the gland.
  The various animal tissues exhibit a property of porosity, or evince
a power of attraction  for aqueous fluids.   If a  piece  of areolar tissue
from the axilla be soaked in water, it will imbibe it  as freely as a sponge.
Serous membranes,  being chiefly composed of areolar tissue, have the
same property, but  to a less  degree ; and the coats of blood-vessels,
and  hollow membranous viscera, are also  porous.   The occurrence
of transudations, through living and dead tissues, is explained by this
property.   When the blood  is loaded  with water,  or its passage
through the blood-vessels is impeded, or when the  vital changes  in
the blood-vessels go  on feebly and imperfectly, their walls exert a
morbid  attraction upon the  water of the contained blood,  which trans-
udes into the surrounding areolar tissue, and gives rise  to that drop-
sical effusion, which  is commonly  called Anasarca.   In the minute
capillary vessels, this property is always  present  in a state of health,
and the nutrition of the surrounding tissues is effected by the exercise
of it.  After death, the influence of porosity is favoured by the total
absence of motion in the fluids, and of vital change in the walls  of
the vessels ; and, therefore, in the dead body we find the areolar tissue
more or less loaded with water in all those places  in which gravita-
tion favoured its accumulation.   The progress of decomposition,  by
disintegrating the tissues, also favours the occurrence of transudation.
  It is probable that certain vital processes consist solely in transuda- 
ENDOSMOSE.—EXOSMOSE.
67
tion.  In this way the watery part of the secretions doubtless escapes
from the blood-vessels, into the canals of the secreting organs ;  and
this  is especially  likely  as regards  the mechanism of the kidney,
where the blood-vessels of the Malpighian bodies, reduced  to their
minutest size, naked, and unassociated with any other tissue, are most
favourably placed for the  occurrence of this phenomenon ;  and  the
absorption of fluids brought in  contact with certain surfaces is expli-
cable on the same principle.
   The process, which was first  described by Dutrochet, under the
name Endosmose  and Exosmose, is  intimately  connected with the
porosity of animal tissues.  It  is  a process,  "in which  the mutual
attraction  of two liquids  is called  into action, one of which  is more
capable than the other of freely wetting a porous solid which forms
part of the combination."   {DanielPs  Chemistry.)
   If  an animal bladder, the caecum  of a  fowl, partially filled with
syrup, and tied tightly at its open end with a  string, be suspended in
a vessel of water, it will soon be found distended almost  to bursting,
in consequence of a considerable quantity of the water having passed
through the wTalls into the cavity of the bladder {Endosmose).  If the
exterior fluid be examined, a  portion of the syrup will be found to
have passed out of the bladder {Exosmose).  Or the phenomenon  may
be illustrated by the following  experiment:—Take a funnel, and tie
over  its broad end (of three or  four inches diameter) a piece of blad-
der, invert it, and  fill it with spirits of wine, and fit to its  small end a
glass tube, three or four feet in length, and then place it in a vessel
of water.   In a short time the  water will be observed to rise in the
tube, and  it will ultimately reach the top and flow over.  " The first
moving power here," says Professor Daniell, "is the force of adhe-
sion between the water and the bladder; the former penetrates the
pores of the latter, and comes in contact, upon its upper surface, with
the spirit,  by the attraction of which, it is removed  from  the bladder
and  mixes with its mass.  The height of the column  is in some
degree the measure of the force thus called into action."  The purely
physical nature  of this process is shown by the fact that  it  will equally
take place through porous inorganic substances, as  through  organic
membranes.  It would be  impossible to do  more  here than give a
brief  explanation of this  remarkable phenomenon.   It is important
to add, that the  observations  of Dutrochet  clearly  show  that the
nature of the septum exerts an important influence upon the direction
of the predominant current.  If the  attraction of the septum for the
exterior fluid be the greater, the endosmotic current will prevail, and
vice versa.
  Endosmose  is a more  important agent in the vital  phenomena of
plants than in those of animals.   It is  supposed, by some physio-
logists,  to be brought into play in  the processes of secretion  and
absorption.
  The animal  membranes exercise the property of porosity in refer-
ence to gases, as well as to liquids ;  and the tendency of dissimilar
o-ases to become diffused  among each other manifests  itself even
through compound textures.   As  in the case of liquids, there  is a 
68
VITAL PROPERTIES.
double current, when two dissimilar gases are separated by a porous
septum, and the predominant current is that which has the strongest
attraction for the septum.   The following experiments illustrate this
phenomenon :—Confine some common air in  a jar, by tying tightly
over it a piece  of  sheet-caoutchouc, and then place the jar under a
large bell-glass filled with hydrogen gas; the hydrogen will gradually
penetrate the  partition, distend the caoutchouc, and ultimately burst it.
Or, suspend a membranous  bag, the stomach  of a rabbit, filled with
common air,  in an  atmosphere of carbonic acid ;  the latter will pene-
trate to the former  and burst the bag.  In both instances there is an
exosmose greatly inferior in the quantity of gas to the endosmose.  In
respiration, this phenomenon  occurs at every inspiration through the
walls of the  pulmonary air-cells and the  plexus of  capillary vessels
distributed  upon them.  {DanieWs  Chemistry.)
  Although in the  manifestation of these phenomena there is no direct
exercise of vital force, the tissues are not the less dependent on healthy
vital action for the preservation of  their peculiar properties in a state
of integrity.  Whoever will compare the compact figure of a vigorous
healthy man,  accustomed to field-sports and active exercises, with the
relaxed, feeble, half-dislocated  limbs of an  ill-nourished, hysterical
woman, will readily perceive how great an influence  healthy nutrition
must exert in preserving and improving the physical  properties of the
tissues.
  The vital properties manifest themselves by a change which occurs
in the molecules of certain tissues,  as the result of a stimulus applied.
The change,  thus produced, may be evident from a visible alteration
in the tissue  stimulated ; or it may show itself through a secondary
influence exerted upon some other  texture or  organ, with which the
stimulated tissue may be in connection.
  These properties exist  in  two tissues, namely, in muscle and in
nerve.   A  muscle, when  stimulated, shortens itself; and, therefore,
it is said to possess the property of contractility.   This power of con-
tracting, in obedience to a stimulus, is characteristic of muscle, and
probably occurs in no other  kind  of animal  texture.  The stimulus
may be  direct irritation by mechanical means,  or by galvanism,  or by
some chemical substance; but the natural one, during life, is propa-
gated by the  nerves.
  In nerve, the vital changes are unaccompanied by any alteration in
the tissue itself, which is appreciable by our senses,   the excitation
or irritation of the  nerve  may be  manifested  in three ways: first, by
its inducing the contraction of the muscle which it supplies; secondly,
by its exciting contraction, in muscles which it does not supply, through
a change wrought  in  the  nervous  centre ; thirdly, by its  exciting a
sensation.  The same stimuli, which we have mentioned as capable
of exciting muscular contraction, will produce these effects in nerves ;
and the will, and  other emotions  of the  mind, are capable of stimu-
lating nerves which are connected with the brain, and exciting action
in the muscles to which they are distributed.
  That a nerve, when irritated, may excite  a sensation, it  is neces-
sary that it shall be in connection with the brain.  The bodily feelings 
         NERVES OF COMMON AND OF PROPER SENSATION.       69

of pain or pleasure are thus  produced, through the medium of what
are called sensitive nerves, or nerves of common sensation;  and we
say that the sensibility of any tissue is great or small, according as it
is supplied with such  nerves in  more or less quantity.  Tendon, in
which probably few nerves exist, is a tissue of low sensibility ; whilst
the skin, which is largely supplied with nerves, is highly sensitive.
   Light, sound, and the sapid and odoriferous qualities of bodies, are
capable of stimulating  certain nerves, and  exciting appropriate sen-
sations in the mind.  The nerves which respond to such stimuli, are
called nerves of proper or special sensation; and  this name seems
appropriate,  because these nerves, when otherwise stimulated, excite
only their peculiar sensations.  If the  optic nerve be  mechanically
irritated, a flash  of light is  produced ;  as  sometimes occurs if the
retina be touched by the needle in the operation for cataract.   If the
auditory nerves be  stimulated by a galvanic  shock, a sound is pro-
duced. Volta, who tried the experiment on his own person, perceived
a hissing and pulsatory sound, which he compared to that of a viscid
substance boiling:  and  Ritter relates, that, upon closing the  circle
when  both his ears were included in it, he was sensible of the sound
of G treble; if but one ear was in the circuit, and the positive pole
applied to it, the sound was lower than G;  if the negative pole was
applied to the ear, the sound was  higher.  (Miiller's Physiology,
translated  by Baly.)    These peculiarities  of the nerves of proper
sensation are due to the fact,  that at their periphery they are so organ-
ized as to be admirably adapted for receiving the impressions of their
special stimuli, and at their  centres  they are connected  with those
parts of the  brain  which take cognizance  of these  special  agents.
Thus the optic  nerve is admirably disposed in the eye for the recep-
tion of luminous  impressions, and  the  auditory nerve is  beautifully
adapted  to receive  the pulsations of sound, whilst each is connected
with  a different part  of the  brain ; and what  are called subjective
phenomena  of  vision or hearing are often the result of local conges-
tions of blood  affecting the  respective nerves of these senses, and
producing mechanical irritation of them.
   In the manifestation of the  vital properties, under the influence of
appropriate stimuli, it cannot be doubted that an organic molecular
change is produced in nerve as well  as in muscle.  This  may be
considered as a polar state, in which the ultimate particles of the tissue
assume a polarized  condition, which  may be  fairly  compared  to that
which friction or other  means can produce in various substances, by
which they  may be rendered mutually attractive or repulsive.  In
muscle, it becomes  at once evident by the powerful  attraction which
is  exerted between  its particles, by which the  shortening is effected.
In nerve, it is shown by the  rapidity with which  the  change excited
by the stimulus at one part  of the nerve is conveyed throughout its
course to the muscle, or to the brain or other nervous centre, with
which it may be connected, producing in them the same or an analo-
gous state.
   As these phenomena occur in tissues, whose chemical composition
is more complex than that of  any others in  the body, and which are 
70
FUNCTIONS.—ANIMAL MOTIONS.
the seat of continual changes, they are subject to many disturbing
causes, and are  easily affected by slight modifications in  the general
state of the system.  Many substances quickly exert an influence upon
them, as opium, strychnine, and various sedatives, narcotics, or stimu-
lants.  Those properties are therefore entirely dependent on the nutri-
tion of their respective tissues;  they quickly vary with  the  state of
that function, and when it ceases, in death, they vanish with it.

  For  information  upon the subjects treated of in this chapter we refer to the fol-
lowing  sources:—Henle, Algemeine Anatomie; Berzelius, Chimie  Organique, Fr.
edit., 1833; Prout on Stomach and Urinary Diseases; Liebig's Animal Chemistry, by
Gregory;  Graham's Chemistry; Daniell's Chemistry; Schwann, Mikroskopische
Untersuchungen iiber die Uebereinstimmung in der Struktur und dem Wachsthum
der Thiere und Pflanzen ; Dutrochet, article Endosmose, in the Cyclopaedia of Ana-
tomy and Physiology.
                         CHAPTER  II.

FUNCTIONS.—ANIMAL MOTIONS.--MOLECULAR MOTION.--ORGANIC MOLE-
  CULAR MOTION.--MUSCULAR MOTION.--CILIARY MOTION.--MOTIONS OF
  SPERMATOZOA.

  The subdivision of the functions of the  human organism into the
animal and the organic, as already stated, maybe adopted as the least
objectionable basis for their arrangement.  Under the former title we
include those  functions, which  are  peculiar to and  characteristic of
the animal part of the living creation, and to  which there  is nothing
similar or analogous in the  vegetable  kingdom.  These are  locomo-
tion and innervation.  The organic functions are present in both king-
doms, with certain modifications.   They are  digestion, absorption,
circulation, respiration, secretion, and generation.
  In examining  these  various  processes, wTe  propose  to  follow the
order in which they have been enumerated. We find it convenient to
take the locomotive function first, because so large a proportion of the
mechanical arrangements, or of the anatomy of the body, is connected
with it.   The transition from locomotion to innervation is easy and
obvious; for the nervous  system has a special connection with the
locomotive organs,  in  order that  the  influence of the will  may be
conveyed to them.  It may be here stated, that in the animal functions
the interference of volition is more frequent than in the organic ones;
and that, in all, the nervous system exerts a certain control, and may
influence to a great degree the performance of  the functions, although
some of them are essentially independent of it.
   Of the minute movements occurring in the interior of the body.—Of
these we may distinguish three kinds : 1.  Those in which particles are
moved  passively by forces  independent  of  themselves.  2. Those
accompanying the  incessant changes of  the organic elements of the
tissues.   3.  Those which occur in certain entire tissues on the appli- 
MOLECULAR MOTION.
71
cation  of an appropriate  stimulus.   All these  movements may  be
called molecular on account  of the minuteness of the  particles con-
cerned in them.
   1. The term molecular motion was used many years  ago by Mr.
Robert Brown, to  denote a phenomenon which he had witnessed in
the particles of various organic and inorganic substances in a state of
extremely minute subdivision.  When these particles were suspended
in water, they exhibited, under the microscope, motions, which con-
sisted in more or less rapid oscillations and rotations of the particles
themselves.  He found them in the pollen of plants, in  many mineral
and metallic substances, in various animal matters, reduced to a subtle
powder,  consisting of particles that ranged  in diameter between the
nuoo a°d 300W °f an inch.  The  movements are clearly not peculiar
to living or organic parts, for they occur in inanimate ones: they
never occur excepting when the particles are suspended in water, or
some liquid ; and  they are attributable  to currents  produced  in the
fluid by evaporation at its surface or edges, for they may be arrested
by covering the fluid  with oil, or using  other means to prevent such
evaporation.   They are not, therefore, inherent in the particles them-
selves, which  only obey the  impulse  communicated to them by the
currents  created in the fluid which holds them in suspension.
   Certain particles, naturally very minute, which are met with in the
body, exhibit  motions when examined under the microscope floating
in fluid.   These motions are entirely due to the same cause as would
excite  them in inorganic particles, namely, to currents in the fluid
created by its evaporation.   The minute granules, or particles of the
chyle, have  been found to exhibit molecular motion ; and it has been
ingeniously supposed, that "these  motions indicate the first obvious
impress  of vitality which  the  new  material has received  from  its
association with living matter."  But, before this supposition can be
admitted, we require evidence to show that these motions are inherent,
and do not result from currents.  The minute rod-like  bodies, which
form the  outer coat of the retina, or Jacob's membrane, also  some-
times exhibit a molecular motion,  when separated and examined in
water, and there  seems no reason to doubt  that this  is  due to the
evaporation  of the fluid in which they float.
   2. Organic  molecular motion.—Some of the motions, which take
place within the living body,  maybe compared to those described  by
Mr. Brown, inasmuch as they are generally, if not always, due to an
extraneous force acting upon  the particles moved; but they differ in
this respect, viz., that the producing  force is developed by the pro-
cesses inseparable from life. Such motions are not in general visible, yet
some have been seen,  which clearly indicate that forces are developed,
during life, capable of producing them.   The movements of particles
within  cells afford  an example: such motions are either of a uniform
rhythmical kind,  or  they  are apparently irregular and oscillating.
Those of the former kind are familiarly known in the vegetable king-
dom by the  Cyclosis which takes place in the oblong cells of Chara;
the granules, which may be seen in motion, are quite passive and are
carried along by currents within the cell.  Motions of the latter kind 
72
MOLECULAR MOTION.
have been seen by Schwann among the granules contained in the cells
of the germinal  membrane of the hen's  egg, as if occasioned by an
endosmotic current through the wall of the cell.  This membrane  is
the seat of active change, the development and growth of new cells,
destined for the evolution of the textures  of the embryo; and they
derive their nutriment from the yelk, on the surface of which they
lie.  Here the contained particles are passive, and the motion in them
is only the index of the currents which give rise to it.  A molecular
motion of the same kind may be seen in the  very minute granules,
which occupy the cells of the membrane  of  black  pigment on the
choroid  coat of the  eye.  Whether  this go on during life, it  is  of
course impossible to  say, but the conditions  for its production are
undoubtedly present.   In the blood may  be seen another example  of
the kind  of motion  under consideration.   The  circulation of this
fluid may be  readily followed in  transparent parts ;  and certain par-
ticles, the blood-discs, which float in it in great numbers, exhibit
movements which can  scarcely be attributed solely to the current  of
the circulating fluid.   It is probable  that secondary  currents may be
established in the blood, or that  attractions and repulsions may exist
between the particles  themselves, or between them and the walls  of
the blood-vessels giving rise to  these motions.   According  to some
observers, the blood-discs  undergo actual changes of shape, becom-
ing now  swollen, and now flattened ;  and this  might be attributed  to
the alternate predominance of endosmose  or exosmose.  But the state-
ment, that they possess an inherent power of contraction of their own,
stands greatly in need of  confirmation.
   Organic molecular motion occurs in nearly all the internal processes.
The introduction of new matter from without into the blood ; the re-
moval of effete particles by a process of absorption ; the  transfer  of
nutrient  matter from the blood  to  supply  the place of the particles
thus removed; the separation of organic  compounds in glands, can-
not take  place without a movement of molecules in the textures con-
cerned in these processes.   We  are  as much at liberty to infer, that
these motions are produced by certain affinities of the particles of the
tissues, as that chemical action is the result of  affinities between cer-
tain forms of matter.   These motions of the organic and inorganic
elements are  incessant during the ceaseless round of oro-anizino- and
disorganizing actions of which  every tissue is  the seat,°as long°as  it
continues living.  The  currents alluded to in the preceding paragraph
are  visible indications of the presence of  these organic movements.
  3. The molecular  movements of nerve and muscle under stimula-
tion have been already mentioned in  the  preceding chapter.  The
capacity  of exhibiting these movements  exists only while the  nutri-
tive process continues  to be carried on in  the respective  tissues__it
ceases with life.   It would appear that the precise chemical constitu-
tion, which is essential to its existence, is of so unstable a nature  as
to be constantly prone to  change, and to  require incessant renewal;
or, it may be, that this capacity is one which is only developed during
the active operation of certain chemical forces, as if it depended ne- 
CILIARY MOTION.
73
cessarily on certain peculiarities  of  the organic  elements when in a
nascent or changing state.
   In muscular movement there is a visible approximation of the ulti-
mate particles of the tissue in a determinate direction, as will be fur-
ther explained in the  proper place; and in  this consists the  whole
value of muscular tissue as a part of the mechanism  of the body.  All
those motions in the living body  which are visible to the naked eye,
and many of those which cannot be  seen without the  aid of lenses,
are  effected by muscular action.   By it canals or tubes adapt  them-
selves to their contents;  the heart propels the vital fluid; the digest-
ive  canal transmits the ingesta from one part to another ; the excretory
reservoirs, or ducts, expel their contents; and lastly, by it the attitudes
are  maintained, and the locomotive  function is performed.
   Ciliary motion.—In the same category with the molecular motions
of the living body we would place that singular phenomenon now
well ascertained by multiplied observations,  which is  called Ciliary
motion.
   Certain surfaces,  which  are,  in  their natural and  healthy  state,
lubricated by fluid, are covered  with  a multitude of  hair-like pro-
cesses, of extreme  delicacy  of  structure  and  minuteness  of size.
These are called cilia, from cilium, an  eyelash.   They are generally
conical  in  shape, being attached by  their  bases to the epithelium
that covers the  surface on which they play, and tapering gradually
to a point; or, as Purkinje and Valentin  state, they are more or less
flattened processes, of which the free  extremities are rounded; and
this  latter form prevails in  the human  subject.   They vary in length
from the ToVo to the T2T00 of an inch.  They are disposed in  rows,
and  are adapted in their arrangement to the  shape and extent of the
surface to which they belong ;
tion  of  the  surface, of the
particles  of the epithelium,
preferring the columnar va-
riety of them.
   During life, and for a cer-
tain  period after death, these
filaments  exhibit a  remark-
able movement, of a fanning
or a lashing  kind, so that
each cilium bends rapidly in
one   direction,  and   returns
again to the quiescent state.
The  motion, when viewed
under  a  high  magnifying
power,  is  singularly beauti-
ful, presenting an appearance
somewhat resembling that of
a field of corn agitated by a
steady breeze.  Any minute
objects  coming  in   contact
with the free extremities of  the cilia are hurried rapidly along in the
     6
they adhere to the edges, or to a por-
 Examplesof Cilia:—1. Portion of a bar of the gill of
the Sea-mussel, Mytilus edulis, showing cilia at rest
and in motion.  2. Ciliated epithelium particles from
the frog's mouth.  3. Ciliated epilhelium particle from
inner surface of human membrana tympani. 4. Ditto,
ditto: from the human bronchial mucous membrana.
5. Leucophrys patula, a polygastric infusory animal-
cule : to show its surface  covered with cilia, and the
mouth surrounded by them. 
74
CILIARY MOTION.
direction of the predominant movement;  one or  more  blood-discs,
accidentally present, will sometimes pass rapidly across the field, pro-
pelled in this way, and very minute particles of powdered  charcoal
may be conveniently used to exhibit this  phenomenon,  and to  indi-
cate the direction of the movement.  The  action of the cilia produces
a current in the surrounding fluid, the direction of which is shown
by the course which the propelled particles take.
  An easy way to observe this phenomenon is to detach by scraping
with a knife a few scales of  epithelium from  the back of  the  throat
of a living frog.  These, moistened with  water, or  serum, will con-
tinue to exhibit the movement of their adherent cilia for a very con-
siderable time,  provided  the piece be kept duly moistened.  On one
occasion we observed a  piece  prepared in  this way exhibit motion
for seventeen hours;  and it would probably have  continued  doing
so for a longer time, had not  the moisture around it evaporated.
However, Purkinje  and Valentin have observed it to last for a much
longer time than this in connection with the body of the animal.   In
the turtle, after death by decapitation, they found  it lasted, in the
mouth, nine days; in the trachea and the  lungs, thirteen days;  and,
in the  oesophagus, nineteen  days.  In frogs, from which  the brain
had been removed, it lasted from four to five days.   The longest time
they observed it to  continue in man and  mammalia was two  days;
but in general it did  not last  nearly so long.   What appears  to  be
immediately necessary to the  continuation of the  movement, is the
integrity of the epithelial cells to which the cilia adhere; for as soon
as these shrink up for want of moisture, or become physically altered
by chemical reagents or by the progress of putrefaction, the cilia im-
mediately  cease to play.
  From these facts we learn two important points in connection with
this phenomenon.   The first is, the truly molecular character of the
movement.  Whatever be the immediate  cause of the action of the
cilia, it is  evidently intimately connected with the minute epithelial
particles to which they are attached; for cilia never exist in man and
the higher animals  without  epithelial particles, and  these particles
have no organic  connection with the subjacent textures, excepting
such as may arise from simple adhesion.    And,  secondly, we per-
ceive, that this  movement is independent  of both the vascular and
the nervous systems, for  it will  continue to manifest itself for many
hours in a single particle isolated from the rest of the  system.  After
death it remains longer  than the  contractility of muscle ;  a circum-
stance which, together with  the facts just mentioned, indicates that
the cilia cannot be moved by little muscles inserted into their bases,
as some have supposed.   And experiment also shows  this  independ-
ence. ^ If the  abdominal aorta be  tied, the muscles of  the  lower
extremities will be paralyzed in consequence of their being deprived
of their blood; and on removing the ligature, and  allowing the blood
to flow, the muscles will  recover themselves.  But a ciliated surface
is not affected at all in its movements, though the supply of blood to
the subjacent tissues be completely cut off.   Again, hydrocyanic acid,
opium, strychnine, belladonna, substances which exert a powerful effect 
CILIARY MOTION.
75
on the nervous system, produce no influence upon ciliary motion.  In
the bodies of animals killed by these poisons, the phenomenon is still
conspicuous;  and even the local application of them does  not hinder
it, provided the solutions do not injure the epithelial texture.  Shocks
of electricity passed  through the ciliated parts, do not  affect the
movement.  Lastly,  the removal of the  brain and  spinal cord in
frogs, by  which all muscular movements are destroyed, does not stop
the action of the cilia.  This striking  fact may likewise be adduced
to disprove the  supposition, that these movements result from the
action of  minute muscles;  for, although muscles  may be  excited to
contract without  nerves, we have no instances in the higher animals
in which  they habitually act without the interference of the nervous
system ; nor is it likely that a movement existing over so extended a
surface, as that by the cilia, would, if effected by muscles,  be  inde-
pendent of nervous influence.
   Alterations  of  temperature affect the ciliary motion, owing, doubt-
less, to the physical  change they induce  in the epithelial particles.
In warm-blooded animals it ceases on a reduction of the temperature
below 43° F.   In cold-blooded  animals, however,  it continues even
at 32°.   In all, a very high temperature effectually  puts a stop  to it.
It is interesting to notice, that all observers agree in stating, that blood
is the best preservative of  the ciliary motion, but the blood  of verte-
brata destroys it in the invertebrata.   Bile  puts a stop  to it, very
probably  by reason of its thick and viscid nature, and not from any
chemical  influence.
   This phenomenon exists  most extensively in the  animal kingdom.
It has been found in  all the vertebrate  classes; and in  the inverte-
brata likewise, with the exception of the  Crustacea, arachnida, and
insects.   It is the  agent by which  the  remarkable  rotation of the
embryo in the ova of mollusca is effected ; and it occurs on the sur-
face of the ova  of polypes and sponges.  The  bodies of some of
the infusoria are covered with cilia, which are apparently employed
by  them  as organs of locomotion, and for the prehension of food
(5, fig. 2.)
  In man, the  ciliary motion has been ascertained to exist  on several
surfaces:—1.  On the surface of the ventricles of the brain and on
the choroid plexuses.   So delicate  are  the cells of epithelium  here,
that the slightest  mechanical injury destroys them ; it is, therefore,
very difficult to see the movement.   Valentin  states that its duration
is considerable in these parts, so that it may be seen in subjects used
for dissection.  2.  On the  mucous membrane of the  nasal  cavities,
extending along the roof of the  pharynx  to  its posterior  wall, on a
level with the  atlas, on the upper and posterior part of the soft palate,
and, in  the immediate neighbourhood of the Eustachian tube, extend-
ing through the tube  itself  to the cavity of the tympanum.  3. On
the membrane  lining  the sinuses of the frontal bone, the  sphenoid,
and the superior maxillary.  4. On the  inner surface of the lachrymal
sac and lachrymal canal. 5. On the membrane of the larynx, trachea,
and  bronchial  tubes.   6.  On the lining membrane of the female
organs of  generation.   It does not exist in the vagina; but it may be 
76
MOTIONS OF SPERMATOZOA.
traced from the lips of the os uteri, through  its cavity,  and through
the Fallopian tubes to their fimbriated margins.
   In nearly all these instances there appears to be a mechanical use
for the  ciliary  movement, namely, to promote  the  expulsion of the
                                    fluid secreted by the surfaces on
Fig. 3.
 Uriniferous tube of Frog's kidney, arising from
capsule of Malpighian body:—a. Cavity of the
tube.  b. Epithelium,  c. Basement membrane.
b'. Ciliated epithelium at the neck of the tube, b" .
Detached ciliated particle. e\ Malpighian cap-
sule,  m. Malpighian tuft.
 which the cilia exist. Wherever
 the direction of the motion has
 been ascertained, it is that which
 would be favourable  to such a
 purpose.  In the bronchial tubes
 and trachea, the direction of the
 motion is  towards  the larynx,
 so that the cilia may be regard-
 ed  as agents of expectoration.
 In the  nose  of the rabbit, Dr.
 Sharpey observed the impulse
 to be directed forwards, and in
 the  maxillary sinus it appeared
 to pass  towards the  back part
 of the cavity, where its opening
 is  situated.   In the  Fallopian
 tube, the direction is stated  by
 Purkinje and Valentin  to  he
 from  the  fimbriated  extremity
 towards the vagina.   It seems
 very probable  that ciliary mo-
 tion exists in the kidney, at the
 narrow neck of each uriniferous
 tube,  as it passes  off from the
 capsule of the Malpighian body.
 This  has not been actually ob-
  served  in the human  subject.
  It was discovered, and has been
 frequently  seen  in  the  frog,
  {Bowman, Phil. Trans., 1842,)
  and is  shown in  the annexed
  drawing, (fig. 3.)   The move-
  ment  is here directed towards
  the  uriniferous  tube,  and  it
 doubtless  is destined to favour
the secretion  from the capsule to
the flow of the aqueous portion of
the tube.
   In the inferior animals the  cilia seem to answer a similar end to
that in man.   They exist extensively on respiratory surfaces, and in
connection with the generative  organs ; and also, but to  a less de-
gree, with the organs of digestion.   But in  some situations, both in
man and in the inferior creatures, it is difficult to  determine what
functions  the ciliary motion can perform.  Such are, in  man, the
ventricles of the brain; and, in the  frog,  the  closed cavities of the 
MOTIONS OF SPERMATOZOA.
77
pericardium and peritoneum.  Here there are no excretory orifices,
toward which the current might set.
  What is the  cause of ciliary motion ?  We have  shown it to  be
independent of  the blood and of the nerves,  and to  resist those de-
pressing causes which usually put a stop to the action of contractile
tissue.   It requires for  its  continuance  three conditions:  a perfect
epithelium cell; moisture, not of too great density; and a temperature
within certain limits.  From Schwann's observations it appears that
cells exhibit a power  of endosmose ; that a chemical change occurs
in the fluids in contact with them;  and that a movement of  their  in-
ternal granules  may be seen under certain circumstances.  If ciliated
epithelium cells exert an attraction  of endosmose upon the surround-
ing fluid, may not this physical phenomenon afford a clue to determine
the cause of the movement ?
  A  very remarkable movement  is manifested  by certain particles
found in the secretion of the testicle, which prevails most extensively
throughout the  animal series, and is even found among plants.  From
the regularity of these movements and their resemblance to  those of
minute animals, a place had been assigned by naturalists to the par-
ticles  in question, in their  zoological classifications, under the name
uCercarise  seminis,"  Spermatozoa,  or  Spermatic  animalcules, and
Ehrenberg  refers them to the Haustellate Entozoa.   These particles
consist chiefly of  a long filament or tail, which is sometimes swollen
at one extremity,  to form the body of the supposed animalcule.  The
motions consist in a  sculling action of the  tail, or  a  slight lateral
vibration of it.  In many of its conditions it closely resembles ciliary
motion ; and its duration after  death,  or after the separation of the
fluid, is pretty much the same as that of the ciliary movements.  The
particles  are extremely minute,  even measured in  their length ; but
especially so in  thickness.   They are, therefore, well adapted to obey
those impulses which  we have shown to be capable  of giving rise to
molecular motions.  We shall return to this curious subject again in
discussing the function of generation.

  On the subjects treated of in this chapter reference is made to the following sources
of information:—Rob. Brown, A brief Account of Microscopical Observations on the
particles contained  in the pollen of plants, and on the  general  existence of active
molecules in organic and inorganic substances; Purkinje and Valentin, Commentatio
Physiologica de phenomeno moius vibratorii continui; article Cilia, by Dr. Sharpey,
in the Cyclopaedia of Anatomy and Physiology; Valentin's article Flimraer-bewegung
in Wagner's Handworterbuch der Physiologic 
78
ORGANS OF LOCOMOTION.
                        CHAPTER III.

LOCOMOTION.--PASSIVE AND ACTIVE ORGANS OF LOCOMOTION.--FIBROUS
  TISSUE, WHITE  AND YELLOW.--AREOLAR  TISSUE.--ADIPOSE TISSUE
  AND FAT.

  Locomotion is that function by which an animal  is able to trans-
port itself from place to place.  It is enjoyed exclusively by animals;
there  being nothing analogous to it in the vegetable kingdom.
  But even, among animals, there are exceptions to the existence of
this function.   Many of them are fixed in their places throughout
their lives ; others enjoy the power of locomotion for a short period,
but subsequently become fixed ; others, again, begin  life fixed to one
place, and are at length set free.
  The power of maintaining the body in  certain positions,  must be
included in the faculty of locomotion, for the organs that are  used for
one, are  also  employed for  the  other;  and the more  difficult it be to
accomplish the former, the more  complicated will be the mechanism
of the locomotive acts.  In a large quadruped,—the horse, for exam-
ple,—standing is effected with a trifling expenditure of muscular force,
because the animal's body is maintained on four pillars  of  support,
which resist the attraction  of  gravity acting  upon it.   Man has to
maintain the erect attitude, and to counteract by muscular action the
tendency of his body to  gravitate  forwards.   The  mechanical adjust-
ments of his frame are less favourable  to preserve the standing pos-
ture than in the four-footed animals.  Hence, in man, the mechanism
of locomotion is  more complicated, both  as regards the power of
preserving certain  attitudes, and  that of moving  from one place to
another.
  The organs  employed in  locomotion  are of two kinds, the passive,
and the active.  The former consist of  all those textures which form
the  skeleton, and  by which its segments are united.   The latter are
the  muscles, to which the nerves convey the  mandates  of the will.
It will be necessary to examine in detail the following textures among
the  passive  organs of locomotion:—1. Fibrous  tissue,  as  binding
together  the various segments  of the  skeleton, and connecting the
muscles to the bones ; 2. Areolar tissue, which is so  extensively dif-
fused  throughout the body, at once separating and uniting neighbour-
ing parts ; 3. Cartilage,  fibro-cartilage, and bone,  which enter^imme-
diately into the construction of the  skeleton; and,  lastly,  synovial
and serous membranes,  being  peculiar arrangements of tissue admi-
rably  suited to facilitate  motion.


                        FIBROUS TISSUE.

  Under this head anatomists range two kinds of texture, resembling
each other only in the fact that they present  to the  naked eye  a fibrous 
FIBROUS TISSUE.
79
aspect, as if they were compounded of a series of bundles of threads
or fibres.   They differ, however, very materially in colour, in physical
properties, in  ultimate  structure : the general purposes which they
serve in the animal economy are pretty much the same ; for both are
used in connection with the  skeleton, and are concerned in the me-
chanism of animal motion and locomotion.   They are distinguished
as, 1. White Fibrous Tissue ; 2. Yellow Fibrous Tissue.
   1. White Fibrous Tissue.—When a  texture of great strength  and
flexibility, and of an unyielding  nature, is  required, either to bind
parts of the skeleton together, to cover and protect organs of delicate
texture, to unite muscles to bone, or other parts, to compress the mus-
cles of a  limb, or strengthen the walls of  a cavity, we  find white
fibrous tissue  called into requisition for these purposes.  Hence we
observe it to assume a great variety of forms, according to the various
uses to which it is  applied.   It occurs,  1,  as ligaments, connected
with joints; 2, as tendons, connecting muscles  to bones; 3, in a
membranous form, covering and protecting certain  organs, as the
dura mater of the head  and spine, the tunica albuginea of the testicle,
the sclerotic coat of the eye, the fibrous pericardium, the covering  of
the corpora  cavernosa penis,  the  fibrous  sheaths  of tendons, the
periosteum of bone, the perichondrium of cartilage, the aponeuroses
of the limbs,  as the fascia lata,  &c.
   When  we examine a portion of fibrous tissue taken from any  of
these sources, we find connected with it a greater or less quantity  of
areolar tissue, which  adheres to its outer surface like a sheath.  This
is the case in all fibrous  structures, except
those which have a  serous membrane con-
nected with them, or those adherent to bone
or cartilage.   The areolar tissue sinks into
the fibrous material,  and  mingles with its
fibres; and, doubtless, it not only serves the
purpose of a nidus for conducting vessels  to
its surface, but  it accompanies  them  spar-
ingly into its substance.
   When  the  areolar tissue has been dis-
sected  off, the surface of  the fibrous tissue
exhibits  a  beautiful  silvery-white  aspect,
and seems composed of bundles of fibres,
which in some are arranged parallel to each
other;  in   others are  disposed on  different
planes, and interlace, or  cross  in  different
directions.  On placing a very thin  piece
of the fibrous tissue under a high power  of
the microscope, we observe what  may be
considered the characteristic feature of this
texture.
   The piece under examination seems to be
composed of a leash of exceedingly delicate
fibrillar, running parallel  to  one  another,
and, if not stretched, disposed to take a wavy course, like a skein  of
Fig. 4.
  White fibrous tissue :—2.
Straight appearance of the tis-
sue when stretched. 1. 3. 4. 5.
Various  wavy  appearances
whieh the tissue exhibits when
not stretched.—Magnified 320
diameters. 
80
ORGANS OF LOCOMOTION.
silk.  But, on  more  accurate  inspection, it is  found impossible to
distinguish threads of a  determinate size ;  they seem, indeed, to be
of various sizes, according to the degree  of splitting to which  the
whole has been submitted, and many are to be seen  so very minute
as at first almost to elude the eye.  In other parts the mass splits up
into membranous rather than filiform fragments ; so that it would  ap-
pear incorrect to describe this tissue as a bundle of threads.  It is rather
a mass, with longitudinal parallel streaks, (many of which are creas-
ings,) and which has  a tendency to slit up  almost ad infinitum in  the
longitudinal direction.  The correctness  of this view is further shown
by the action of acid,  which obliterates, for the most part, all appear-
ance of fibrillse, and swells it up as an entire mass.
  Physical and vital properties.—White fibrous tissue \sinelastic, and,
under  ordinary circumstances, inextensible;  though it does admit of
being somewhat stretched  by the influence of a long-continued and
slowly acting force, as is seen occasionally when an effusion of fluid
has taken place into an articular cavity, or when a tumour has slowly
grown under a fascia.  Its force of cohesion is the most valuable and
characteristic quality of the white fibrous tissue, and to this its vari-
ous important uses are chiefly due.   Mascagni  calculates the force
requisite to rupture the tendo-Achillis as equal to 1,000 pounds' weight.
Instances are constantly seen where  muscles are torn, or bones frac-
tured,  while the  tendons or  ligaments, through which  the  force
has acted, have escaped.  Thus, the malleoli are often dragged off by
twists of the foot acting on those processes of bone through the late-
ral ligaments of the joint.   It is  entirely  devoid of contractility or
irritability;  and its sensibility is very low, so much so that tendons
hanging out of a wound have been cut without the patient being aware
of it.
  Vessels and Nerves.—White fibrous tissue contains few vessels ;
they are small, and follow for the most part the course of the bundles
of the tissue; they appear more numerous  in the dura mater,  and in
periosteum, than in other parts.   The presence of nerves, and their
mode of subdivision, have  not as yet been satisfactorily demonstrated
anatomically ; we  infer their  existence from the tissue  manifesting
sensibility in some  forms of disease.
  Chemical composition.—The flexibility of fibrous tissue is  owing to
its containing a  small proportion of water.  A tendon, ligament  or
fibrous membrane, will dry readily; it then becomes hard and rigid;
it resists the putrefactive  process when not kept moist, and  even Then
putrefies less readily than the  softer  textures.  Acetic acid causes it
to swell up, instantly  removes its peculiar appearance of wavy fibres,
and displays  some  broken  elongated corpuscles, which are  proba-
bly the  remains of the nuclei  of the  development-cells.   Gelatine
may be extracted in considerable quantity  from  white fibrous tissue
by boiling, and it would appear to constitute its chief proximate prin-
ciple.
  Of the different forms of white fibrous  tissue.—A. Ligaments.—
Ligaments  are  connected  with joints.   They pass in determinate
directions from one bone  to another, and  serve to limit certain  move- 
FIBROUS TISSUE.
81
ments of the joint, while they permit others.  They, therefore, con-
stitute an extremely important part of the articular mechanism in pre-
serving the integrity of the  joint in  its various movements.  There
are  three  principal kinds  of  articular ligaments:—1. Funicular,
rounded cords of white fibrous  tissue, of  which we  may give  as
examples the external  lateral ligament of the knee-joint, the perpen-
dicular ligament of the ankle-joint, &c: 2. Fascicular, flattened bands,
more or less expanded; ex. internal lateral ligament of the knee-joint,
lateral ligaments of the elbow-joint, anterior and posterior ligaments
of the wrist-joint,  and, indeed,  the great majority of ligaments in the
body:  3.  Capsular; these are barrel-shaped expansions, attached  by
their extremities around the margin of the articular surfaces compos-
ing the joint, and forming a complete  but a loose investment to it,
so that  its movements are not particularly restricted in one  direction
more than another.  They constitute one of the anatomical characters
of an enarthrodial  or ball-and-socket joint, and are found in the only
two perfect examples of that form of articulation, namely, the shoulder
and hip joints.
   B. Tendons.—Tendons serve to attach  muscle to bone, or some
other part of the sclerous system.   We may enumerate three varieties
of  tendon, as regards  form  : 1. Funicular, e. g., long tendon of the
biceps cubiti; 2. Fascicular, short tendon  of the  same  muscle, and
most of the tendons of the  body; 3. Aponeurotic, tendinous expan-
sions, sometimes of considerable extent, and very useful in protecting
the walls of cavities.  The  tendons of the abdominal muscles afford
good examples of this variety.
  The tendons are for the  most part implanted by separate fascicles
into distinct depressions in  the  bones, and  are also closely incorpo-
rated with the periosteum ; so that in maceration, when  the latter is
separated, it becomes easy to remove the  tendons.   In some birds,
whose tendons are black, the periosteum is black also ; and in the
human  subject we may often see  the tendinous fibres continued  on
the surface of the periosteum,  as  a  shining  silvery  layer, following
the primitive direction  of the tendinous fibres, from which they were
derived ; a marked example of this may be  seen on the sternum, in
front of which the tendinous fibres of the opposite pectoral muscles
meet and decussate, and thus form the superficial layer of the perios-
teum covering that bone.   The length  of the tendons is beautifully
adapted to the quantity of contractile fibre  required to perform a cer-
tain  movement; thus,  in the biceps cubiti, were the whole length
between the scapula and radius occupied by muscular fibre, there would
be a great waste of that contractile tissue, as there would be much
more than is wanted to  produce  the required motion; tendon  is, there-
fore, made to take the  place  of the superfluous muscle : in this way
we  may explain the differences  in length of the tendons even in  the
same limb.
  C. Membranous.—In the  form  of an expanded membrane white
fibrous  tissue  is used  to cover, protect, and support various parts.
Under such circumstances we often find that it not only forms an ex-
ternal covering to them, but  that it sends in processes or septa, which 
82
ORGANS OF LOCOMOTION.
Fig. 5.
separate certain subdivisions or smaller parts.   Thus, the fascia lata
of the thigh not only invests the muscles of the thigh, but sends in
processes which pass down to the periosteum, and separate the several
muscles from each other ; and the dura mater of the cranium sends in
processes by which certain portions of the encephalon are separated
from one another.
  Reparation and Reproduction.—When a solution of continuity takes
place in white  fibrous tissue, it readily heals by the interposition of
a new substance, every way similar to the original tissue,  excepting
that it wants  its peculiar glistening  aspect, and is more bulky and
transparent.*
  2.  Yellow Fibrous Tissue.—In colour, and  in the possession of elas-
ticity to a remarkable  extent, this tissue  differs manifestly from that
last described.
  It is yellow:  disposed in bundles of fibres, and  covered by a thin
sheath of areolar  tissue,  which  likewise sinks in among its fibres.
In man it exists in the fascicular, funicular, and membranous forms.
                   Under the microscope we observe it to consist of
                fibres, round in some, flattened in other specimens.
                These fibres are very variable in diameter, usually
                from  5^ to To-(j(jff °f an  inch in diameter.   They
                bifurcate, or even divide into three ;  and the sum
                of the diameters of the branches considerably ex-
                ceeds the diameter of the trunk.  They anastomose
                freely with  each other.   They are  prone  to  break
                under manipulation, and  the broken extremities
                are abrupt and disposed  to  curl up :  when many of
                these broken ends exist together in the same piece,
                they give it a very peculiar  and characteristic  ap-
                pearance.
                   In the human subject  we find this tissue employ-
                ed  in the spine, as the ligamenta subflava,  extended
                between the lamina? of the  vertebra? ; in the larynx,
                forming  the thyro-hyoid and  crico-thyroid  mem-
                branes, and the chordae vocales ; and in the trachea,
                forming  the  longitudinal or  elastic bands of that
                tube, and of its branches.   The internal lateral liga-
                ment of the lower  jaw, the  stylo-hyoid ligament,
                and the transversalis fascia  of the  abdomen,  are
                also,  in  a  great measure, composed of it.  Among
                the lower animals  it is very extensively used for
                mechanical  purposes, of which there  is  a familiar
                instance in  the ligamentum  nuchas of  quadrupeds.
Its great elasticity fits it for restoring parts after they have been moved
by muscular  action.   Hence  it is generally employed to  supply an
antagonist force to the muscular.
   A peculiar modification of the yellow fibrous tissue  composes the
proper coat of  the  arteries, and it will be described with the blood-
vessels.
 Yellow fibrous tis-
sue, showing the curly
and branched dispo-
sition of its fibrillne,
their definite outline,
and abrupt mode of
fracture.  At 1, the
structure is not dis-
turbed, as  in the rest
of  the  specimen. —
Magnified 320 diame-
ters.
* We have ascertained this in the case of a divided tendo-Achillis. 
AREOLAR TISSUE.
83
  In chemical constitution,  this tissue  differs  remarkably from  the
white fibrous tissue.  It is unaffected by the weaker acids, or by-
boiling, and will resist putrefaction, and preserve its elasticity  dur-
ing a very long period.  Very long  boiling appears to extract from
it  a minute  quantity of a  substance allied to gelatine ;  but this is
perhaps derived from  the areolar tissue  and vessels, which always
penetrate sparingly among its fibres, and cannot be separated by dis-
section.
   There appear to be no vestiges of the nuclei of cells in this tissue;
at least we have failed to detect them.

   We have hitherto spoken of the two  forms of fibrous tissue as they
occur in isolated masses ;  but their distribution through the body is
far more extensive than this description would imply.  In a diffused
form, blended with one another in very varying proportions, and each
one of them  presenting a variety of  modifications, they compose  the
areolar  tissue, which may now be conveniently considered  under  a
separate head.
                    OF THE AREOLAR TISSUE.

                 {Cellular or Filamentous Tissue.)

   This is very widely dispersed  among the other tissues  of the
body, and of itself constitutes a principal portion of some organs.
It serves the most  important purposes  in  the  construction  of the
body, by  binding together, and yet allowing movement between, its
elementary parts: and  it contributes  largely to the formation  of
membranes conferring  protection by their toughness, resistance, and
elasticity.
   Microscopic characters.— When a fragment  of the areolar tissue
from a favourable  situation is examined, it  presents  an  inextricable
interlacement of tortuous and wavy threads  intersecting  one another
in every possible direction.   They are  of two kinds.  The first are
chiefly in  the form of bands of  very unequal thickness, and  inelastic.
Numerous streaks  are  visible  in them, not  usually parallel  with the
border,  though taking a general longitudinal  direction. These streaks,
like the bands themselves, have a wavy character, but they are ren-
dered straight by being stretched.  The streaks seem  more the marks
of a longitudinal creasing, than a true separation into threads: for it
is  impossible by any art to tear up the band  into filaments of a deter-
minate size, although it manifests a decided tendency to tear length-
wise.  The larger of these bands are often as wide as -5^ of an inch ;
they branch, or unite with others, here and there.  The smaller  ones
are often  too  minute to be visible, except with  a good instrument.
These are the white fibrous element.
   The others are long,  single, elastic, branched filaments, with a dark,
decided border, and disposed to curl when not  put  on  the stretch.
These interlace with the  others, but appear to have no continuity of 
84
ORGANS OF LOCOMOTION.
substance with them.   They are for  the most part  about the sAir  of
an inch in thickness; but we often see, in the same specimen, others
Fig. 6.
Fig. 7.
"mm    IJiVt

 The t'-vo elements of Areolar tissue, in their natural rela-
tions to one another:—1. The white fibrous element, with
cell-nuclei, 9, sparingly visible in it.  2. The yellow fibrous
element, showing the branching or anastomosing character
of its fibrillee.  3. Fibrillar of the yellow element, far finer
than the rest, but having a similar curly character.  8. Nu-
cleolated cell-nuclei, often seen apparently loose.—From
the areolar tissue under the pectoral muscle, magnified 320
diameters.
 Development of the Areolar tissue
(white fibrous element):—4.  Nucle-
ated cells, of a rounded form.  5. 6. 7.
The same, elongated in different de-
grees, and  branching.  At  7. the
elongated extremities have joined
others, and  are already assuming a
distinctly fibrous character.—After
Schwann.
of much  greater density.  These form the  yellow fibrous  element,
(fig. 6.)
  These two tissues maybe most easily discriminated by the addition
of a drop of dilute acetic acid, which at once swells up  the former,
and renders it transparent, while it produces no change in  the  latter.
The wavy bands of the white  fibrous part, on being touched by the
acid, may be seen to expand en masse, and not as  though they con-
sisted of a mere bundle of smaller filaments ;  yet there often remains
in them an appearance of more  or less wavy transverse lines at pretty
equal distances, remotely resembling those on the fibre of striped mus-
cle.  These we are  unable to explain.   The  acid also brings into
view corpuscles of an oval shape, often  broken  into fragments, and
stretching for some distance along the  interior  of the band.   These
seem to be the nuclei of  the  cells from which the  bands have been
originally produced.
  In the  earliest period at which the  areolar tissue can be examined,
Schwann has described it as consisting of nucleated particles, sending 
AREOLAR TISSUE.
85
 offsets on the opposite sides,  and connecting themselves with others
 in the vicinity.   The threads thus formed are at first homogeneous;
 the longitudinal streaks and the wavy character appear subsequently
 (fig. 7).  His description is drawn from the white fibrous element;
 but it may be extended to the yellow also.
   We have  observed frequently among the threads of  areolar tissue
 taken from adult subjects  a number  of corpuscles  (8,  fig. 6), either
 isolated, or having very delicate prolongations among the neighbouring
 threads.   These seem with great probability to  be  either advancing
 or receding  stages of the tissue.
   It is not known whether the  ultimate  elements of  the  areolar tis-
 sue have any immediate attachment or union with  the other tissues,
 among which they lie, or whether they merely enclose them by the
 complexity of their web.
   By the endless crossing and  twining of these  microscopic fila-
 ments, and of fasciculi of them, among one another, a web of amaz-
 ing  intricacy results, of which  the  interstices are  most irregular in
 size and shape, and all necessarily communicate with one another.
   This is well seen by forcibly filling the tissue with  air or water in
 any region.   In the living body this  is very obvious in anasarca, and
 in traumatic  emphysema, as in  the  remarkable  case related by Dr.
 W. Hunter in his celebrated paper.{Med. Obs. and Inquir., vol. ii. p.
 17), where the whole body was blown up so tensely as  to resemble a
 drum.
   The interstices are not cavities possessed of definite limits, because
 they are open on all sides, and  ulti-
 mately constituted out of a mass of
 tangled threads.   The  application of
 the term, cell, to  them, is therefore
 inappropriate ; and it cannot be won-
 dered at, that it  should have led  to
 much  confusion.   In  certain situa-
 tions, however, where  this tissue  is
 in great abundance, and where it first
 attracted attention at the time when
 elementary tissues began to be sepa-
 rately studied, the meshes thus form-
 ed are  disposed so  as  to constitute
 secondary  cavities, having a some-
 what  determinate shape and size, and
 which are visible  to the naked eye.
 These generally contain fat, and may
 be admirably studied in most parts of
 the subcutaneous tissue.  They are
 better deserving the name of  cells
 than  the interstices formed  by the
 first interlacement of the elementary
 filaments.  But they communicate freely, as the smaller interstices do,
 their walls being everywhere cribriform, and capable  of giving passage
to air or fluids.
Fig. 8.
 Portion of Areolar tissue, inflated and
dried, showing the general character of its
larger meshes.  Each lamina and filament
here represented contains numerous small-
er ones matted together by the mode of pre-
paration.—Magnified twenty diameters. 
86
ORGANS OF LOCOMOTION.
  The areolar tissue is one of the most extensively diffused of all the
elements of organization, and its chief purpose seems to be that of
connecting together other tissues in such a way as to permit a greater
or less freedom of motion between them.  To do this, it is placed in
their  interstices, and is more or less lax, more  or  less abundant,
according to the particular exigency of the part.   It  is by means of
this tissue, as well as by the  complexity of its own web, that almost
every part of the vascular system is fixed in its position, and allowed
to undergo the movements impressed upon it by the circulative powers.
Even the capillaries supplying this system itself are for the most part
brought to it, and enveloped, by this tissue.
  So true and comprehensive is this  description of  the  association
of the areolar tissue with the vascular, that  it would be  difficult  to
point out a  single instance in which  one office of  the former is not
to envelop  and protect  the  latter.   But the statements that have
been made of its universal presence have no good  evidence in their
favour.  In the compacter parts of bone, in  teeth, and  in cartilage,
it is  certainly not present; and, indeed, it  could   serve no purpose
in those  structures.  In the substance of the brain, also, it does not
exist, excepting around the vessels two or  three  removes from the
capillaries.
  In the muscles it connects the  elementary fibres to  one  another,
and preserves them from undue separation  during contraction ; but
even here it is bound within the  same limits as  the  capillaries, not
penetrating  the sarcolemma to touch the contractile element within.
It enters the muscles abundantly along with their vessels and  nerves.
It is remarkable, however, that the central organ  of the circulation,
like the central organ of  the  nervous system, contains this tissue  in
very small proportion ; one reason of which seems to be, that its fibres
differ from the  parallel fibres  of other muscles, by twining among one
another, and thus are enabled to dispense with an extraneous bond
of connection.
  Besides penetrating between the  fibres of  the muscles, whose mi-
nute parts are in continual  movement upon one another  during con-
traction, it generally invests their exterior, in a profusion proportioned
to the  extent to which these  organs  move as a whole upon neigh-
bouring parts, of which the best examples may be  seen  between the
great muscles of the extremities ; between these and their enveloping
fasciae (not their fasciae of origin);  under the occipito-frontalis muscle
and its tendon ; and in the upper eyelids.
  The areolar tissue is also present in immense  quantities under the
skin of most parts of the body, and especially where great mobility of
the integument is  required, either as  a  protection  to  deeper organs
against  external violence, or to facilitate the various movements of
the frame.   Such are the regions of the abdomen,  and of several of
the articulations, and  the eyelids.
  Around internal organs which  change their form, size, or  position
in the routine  of their functions, and which are wholly or partially
without a free surface, as the pharynx, oesophagus, lumbar colon, blad-
der, &c, this tissue is abundant,  and its filaments so long, tortuous, 
AREOLAR TISSUE.
87
and laxly interwoven, as  to admit of a ready and extensive motion
on the neighbouring viscera.
  This tissue likewise  forms a layer lying under the mucous and
the serous  membranes in  almost every  situation, though presenting
great variations of quantity and denseness:  it  renders  the  move-
ments of such parts easy.   It  also closely invests the  exterior  of
every  gland and  parenchymatous  organ,  and enters more or less
abundantly into its inner recesses, along with its vessels, nerves, and
absorbents: but there is no  doubt that it has been supposed to have
a much greater share in the formation of this numerous class of or-
gans than an ultimate  anatomical analysis  of them, conducted with
careful precision, will at all  warrant.   In all these cases it is a more
or less copious attendant  on the vessels; but wherever, either from
the  intricacy of the interlacement  of  the  capillaries with the other
essential elements of the particular  organ, or the  greater  strength  of
these elements themselves, the firm contexture of the whole is pro-
vided for,  while little or no motion is required between its parts, this
interstitial  filamentary tissue will be found to be confined to the larger
blood-vessels, and to the  surface of the natural  subdivisions of the
organ.
   For the  present, it may be sufficient  to  illustrate  this remark by
contrasting two important  glands, in  reference to this point.   The
liver is well screened from  injury by its position ;  it is liable  to no
change of bulk; it consists throughout of a continuous and close net-
work of capillaries, the  interstices of which  are filled by the nucleated
secretion-particles.   The  lobules resulting  from the distribution  of
the vessels and ducts  blend together  at numerous points, and have
no motion on one another.  Here the  areolar  tissue is in very small
quantity, and is limited to the ramifications  of the vessels and ducts.
The mamma, on the other hand,  is, by its situation, peculiarly ob-
noxious  to external injury.   It is broken  up into numerous subdi-
visions, which move with the utmost freedom on one another, and it is
moreover liable to temporary augmentations of bulk.  In this import-
ant gland not only is there a common investment of peculiar density,
but an extraordinary abundance of areolar tissue disseminated through-
out its interior.
  Thus, this tissue, so widely spread  throughout the body, whether
it serve the purpose of an investment  to large segments  or  masses,
under the form of  a  membrane, strengthening and protecting them,
and escorting their vessels and other components into and from their
substance (atmospheric), or as a web  of union between the simplest
elements of their organization (parenchymal), is to be  regarded as
rather taking a subordinate or ministering share in the  constitution of
the frame, than as being of primary  importance in itself.
  It is a cement that allows of separation between what it binds to-
gether ;  and it accomplishes this double purpose in a manner suited
to the necessities of diverse  parts, by a variety so simple in the num-
ber, intricacy, and  closeness  of its threads, as  to  be worthy of the
highest admiration, while it is wholly inimitable by art.
  Where great elasticity is  required,  the yellow element preponde- 
88
ADIPOSE TISSUE.
rates;  while the white fibrous  element abounds in parts  demanding
tenacity and power of resistance.   In all cases  the openness of the
network is proportioned to the extent of mobility required.  Where
the meshes are  small,  the  threads  composing  them  branch and
anastomose  with  one  another  with much greater frequency.   The
texture of the cutis affords the most characteristic example of this
condition.
  Physical properties.—These  have  only been  studied  hitherto in
those situations where the tissue exists in great abundance, as in the
subcutaneous fascia, the sheaths of muscles, &c.  It has here a whit-
ish  hue, especially when  steeped  in  water.   It  is  extensible in all
directions, and is  very elastic,  returning to its  original  disposition
after stretching.   It possesses no contractility beyond that attribu-
table to the vessels which are  everywhere found in connection  with
it,  and in  such  situations  in great profusion.   Its sensibility is
usually stated  to be low ;  but it may be doubted  whether the nerves
can in  any case be said to be  distributed  to  this  tissue, which has
been already shown to be an  appendage and  protector to  these and
other organs.  Its asserted powers of absorption and secretion apper-
tain to the capillary blood-vessels, rather  than to  the  threads of the
areolar tissue.
  This tissue, like all other  soft solids, contains a large  quantity of
water.   This keeps the filaments moist, without  being so  abundant
as to be free in their interstices.  A morbid increase of this fluid in
the subcutaneous areolar  tissue occasions the condition  called ana-
sarca, and which may be known by the skin pitting under the pressure
of the  finger.
  When  dried, out of the body, areolar  tissue  becomes  hard and
transparent, but resumes its former state if moistened.  It undergoes
the putrefactive process slowly.  It  is one  of  that class of tissues
which  yields gelatine  by boiling, the gelatine being derived from the
white fibrous element only.
  The great  value of areolar  tissue,  in  facilitating  the motion of
parts between which it is situate, is shown by the  effects  of inflam-
mation, or other diseases which injure its physical properties.   It is
well known, that,  when the subcutaneous tissue is the seat of phleg-
monous inflammation,  the  movements of  the part affected are stiff
and painful, or altogether  impeded, because  the subjacent muscles
cannot move freely, by reason of the  loss of elasticity in  the areolar
tissue.  When this tissue becomes indurated by an  effusion of coagu-
lable  material, the movements of the diseased limb  are similarly
impaired.
              OP THE ADIPOSE TISSUE, AND OF FAT.

  This tissue has no alliance either of structure or function with the
areolar tissue ;  it is, however, usually deposited  in connection with
that  tissue, and therefore we  find  it convenient  to  notice  it here.
Malpighi, W. Hunter, Monro, and, more recently, other distinguished 
ADIPOSE TISSUE.
89
anatomists, pointed out the distinctness of these two tissues; but such
has been the influence of the term cellular, applied to both, that they
are still usually classed together.  Now, however, that  microscopes,
on which reliance can be placed, declare their totally distinct nature,
it is full time that they be treated of  as altogether distinct and inde-
pendent tissues.
   A common use of the  adipose  tissue  being to occupy spaces of
various dimensions left  in the  interstices between organs, and thus
to facilitate motion and  contribute to symmetry, it is very commonly
closely associated with the areolar tissue ; but the connection is  not
an essential one.  In the cancelli of bones there is a large deposit of
fat, but none of this filamentary tissue; and in  numerous situations,
as the eyelids,  beneath the epicranial aponeurosis, between the rec-
tum and bladder, under  the mucous membranes, and  in  the whole
of the cutis,  the areolar tissue exists without being ever accompanied
by fat.   Nevertheless, their apparent admixture  in  many situations
has given rise  to the term " adipose  cellular tissue" applied to  the
two combined, as distinguished from that areolar tissue which contains
no fat.   This term should be  discarded as leading to much miscon-
ception.
   A distinction is to be  drawn between fat and  the  adipose  tissue.
The tissue is a membrane of extreme tenuity, in  the  form of closed
cells or vesicles ; the fat is the material contained within them.
   The membrane of the adipose  vesicle does not  exceed the zrrjoo of
an inch in thickness, and is quite transparent.   It is moistened by
watery fluid, for  which,  as Mr. Paget has  suggested, it has a greater
attraction than for the fat  it contains.  It is perfectly homogeneous,
having no appearance of compound  structure,  and consequently  be-
longs to the class of simple or elementary membranes.   Each vesicle
is  a perfect organ in itself; is from the ^ to the giro of an inch in
diameter, when  fully developed ;  and is
supplied  on its   exterior  with  capillary
blood-vessels,  having  a  special disposi-
tion.
   The  fat vesicles  are  usually  deposited
in great numbers together, and  they then
become flattened on  their  contiguous as-
pects, and assume a polyhedral figure more
or less  regular (fig.  9).   But, if isolated,
their form  is rounded, as may be  seen in
eminent beauty in the double series of them
which frequently accompanies the  minute
vessels traversing membranous expansions
of the  areolar  tissue, and other lamellar
structures, as the mesentery of small ani-
mals.   The  vessels are thus attended by
fat vesicles,  for  the  manifest purpose of
protection from the pressure to which they
would be exposed in their  open course, and they throw around each
vesicle  a capillary loop.
    7
 Fat vesicles, assuming the poly-
hedral form from pressure against
one another. The capillary vessels
are not  represenifd.—From  the
omentum: magnified  about  300
diameters. 
90
ORGANS OF LOCOMOTION.
  Where the  fat is  in  considerable quantity, it is  commonly sub-
divided into a  number of small fragments or lobules, fitted accurately
to one  another and invested  with areolar tissue, for the  purpose,
chiefly, of permitting motion between the parts of the mass, but, also,
for the convenience of the distribution of its blood-vessels.

                               Fig. 10.
 Blood-vessels of Fat:—1. Minute flattened fat-lobule, in which the vessels only are represented. 3.
The terminal artery.  4. The primitive vein. 5.'The fat vesicles of one border of the lobule, sepa-
rately represented.  Magnified 1U0 diameters.—2. Plan of the arrangement'of the capillaries on the
exterior of the vesicles : more highly magnified.

  The blood-vessels enter  the chinks between the lobules  (fig. 10,
1, 2), and soon distribute themselves through their interior, under the
form of a solid capillary network,  whose vessels occupy the angles
formed  by the  contiguous sides of the vesicles, and anastomose with
one another at the points where these  angles meet.  This  is one of
those situations where the capillary  vessels can be most unequivocally
proved  to possess distinct membranous parietes.
  Fat.—Fat is a white or  yellow unctuous  substance, unorganized,
and  secreted  into  the interior of  the adipose  vesicles.   Chemists
have  distinguished in it two  solid proximate principles, stearine  and
margarine, combined with  a  fluid one, or  oil, elaine;  on the relative
proportions of which the principal of the  numerous modifications of
its external qualities would seem  to depend.  These  principles  may
be obtained by different means.  Boiling alcohol dissolves both, but
on cooling deposits the stearine in  snow-white flakes ; and the elaine
may be set free by the addition of water, for which the  alcohol has
a superior affinity.   Or, the  elaine may be separated  by pressure.
Stearine preserves  its solidity at  a temperature of 167° Fahr., and
elaine remains fluid at 63° or 65°  F.   Margarine   exists along with
stearine in most fats, and may be  separated from  it by  ether, which
dissolves  margarine, but not  stearine; it  is said  to  exist alone  in
human  fat, which is therefore destitute of stearine.   These proximate 
ADIPOSE TISSUE AND FAT.
91
elements  of fat are  regarded by modern chemists as natural  com-
pounds of certain organic acids with  an organic base, to which the
name of glycerine has been given, from its  sweet  taste.   The  acids
are, the stearic, margaric, and elaic; and  the  proximate principles
are, respectively, a stearate, a margarate, and an elaate of glycerine.
By boiling oil or fat with a solution  of caustic alkali, the acids  unite
with the potash, forming soap, and  the  glycerine  remains dissolved
in the liquid.  By evaporating this  liquid (in  which any excess  of
alkali had been previously neutralized  by tartaric  acid) to a  thick
syrup, the glycerine  may be  obtained from it in solution  by strong
alcohol.
   We may often detect a spontaneous separation of these two proxi-
mate  principles within the fat vesicle of the human subject.   The
solid  portion collects in a -spot on the inner surface of the cell-mem-
brane, and looks like a  small star  (fig. 11,
2, 2,  2).   The elaine occupies the remainder          Fig. n.
of the vesicle, except when  the  quantity of
fat in the  cell is smaller than usual ;  in which        /rfF^k\
case we may often discern a  little  aqueous        (fLJly^St^.....2
fluid  between the  elaine  and the  cell-mem-        A~KiiliIrliir.....3
brane on  the side  farthest from the  star (fig.       wT^ffi^^
11, 1, 1,): a condition, by the way, which    2   mJlp^^
is very favourable for the observation of this        ^g£/- i
membrane itself.
   m,      n   , • ,    r r .       i           i    Fat vesicles from an emaciat-
   1 he softer kinds ot fat were denominated  ed  subject:—1. 1.  The ceil-
by the older anatomistspinguedo, lard ; and  ^^SJ-J-J&X&l
the more  SOlid, Sebum Or SeVUm, SUet, tal-  mass, with theela.ne mconnec-
               '..'.?      Hon with  it, but not filling  the
low.   Hunter distinguishes four varieties as  ceil.
to fluidity ; oil, lard,  tallow,  and spermaceti.
The elaine of human fat retains its fluidity at 40° F.  Lard melts  at
86° F.; tallow at 104° F.   Spermaceti is fluid in a heat above  115°
F., and solid at 112°.  Oil is elaine with little  or no stearine, as the
neat's foot oil, obtained from the bones of the ox.  In lard the stearine
is in abundance, but  the elaine slightly predominates.   In tallow and
spermaceti there is a  predominance of stearine.
   Ultimate analysis of Fat.—Human fat, according to Chevreul, con-
sists of
                          Hydrogen  11-416
                          Carbon    79-000
                          Oxygen    9-584
100-000
  Distribution.—The adipose tissue is found very extensively in the
animal  kingdom.   It  is  found in larvae as  well  as in the perfect
insect:  also  in  the  mollusca.   It prevails in  all the tribes  of the
vertebrata.   In  fish it occurs throughout the  body ; but in some,
as the  cod,  whiting,  haddock, and  all of the  ray kind,  according
to Hunter, it is only  met with  in the liver.   In reptiles it exists
chiefly in the abdomen.  In the  frog, toad,  &c,  it  is  found in the
form of long appendages, like  the appendices epiploicee, situated on 
92
ORGANS OF LOCOMOTION.
each side of  the spine.  In birds it exists  chiefly between the peri-
toneum and  abdominal muscles;  but there  is  also a  considerable
deposit in the bones of the legs, feet, last  bones of the wings, and
of the tail, especially of the swimming tribes, the oily principle being
more abundant than in mammals.  In  mammalia it is very generally
diffused.   This class, as a  whole, has the  greatest quantity under
the skin, and about certain of the abdominal viscera ;  but the hare
forms a remarkable exception, it being sometimes difficult to find a
particle in its whole body.  It usually  abounds most in the beginning
of winter; and this is especially the case with the hog, and with hy-
bernating animals, which, during their dormant  state, absorb  it into
the system.
   It is ordinarily accumulated in large masses about the kidneys, more
particularly in ruminants, where it furnishes the best  example of that
variety of it termed suet.
   Among mankind many remarkable varieties exist in regard to this
tissue.   Thus, in  general, women are  fatter than men.   The healthy
human foetus, after the middle of the period of gestation, accumulates
fat in considerable quantities :  towards middle age, there is a similar
disposition, which has not escaped ordinary observation, " Fat, fair,
and forty:" in old age and decrepitude, the  adipose deposit  greatly
diminishes.
   Differences are also  constantly seen  in individuals, which can  be
referred only to an original constitutional bent.  Thus young children
are occasionally so overloaded with this tissue as to be unable  to fol-
low their  sports;  and it is not  uncommon  for a similar tendency to
manifest  itself  towards the adult  period,  particularly in girls.  In
elderly persons, fat is  especially prone to be  accumulated  over the
abdomen, and between the layers of  the  epiploon  and mesentery.
Instances where it attains the thickness of three or four inches under
the skin of the belly are not unfrequent in  corpulent  persons.  A
similar abundance occasions the " double chin."
   It is perhaps possible for the body to grow  so  egregiously fat as to
become lighter than water; but whether implicit faith is to  be placed
in the  story of  the  Italian priest Paolo Moccia, who weighed thirty
pounds less than his bulk of water, and therefore could not sink in
that fluid, we do not pretend to  decide.   The excessive deposit of
this substance constitutes a disease, which has been not very correctly
called polysarcia.   John Bull is celebrated for his proneness to accu-
mulate fat: M. Blainville remarks, with naivete, " We have seen many
individuals of the English nation whom embonpoint had rendered al-
most monstrous ; and I remember, among others, a man exhibited at
the Palais Royal who weighed five hundred  pounds. He was literally
as broad  as he was long."
   Among the Hottentot women,  the fat is  apt to gather in the but-
tocks, and is considered a prominent mark of beauty ; but this does
not usually occur till after the first  pregnancy.  A somewhat analo-
gous formation exists in a  variety of sheep, {Ovis  steatopyga, fat-
buttocked sheep.   Pallas,) reared  by  the pastoral tribes of Asia in
which a large mass of fat covers the buttocks and takes the place of 
ADIPOSE TISSUE AND FAT.
93
the tail, appearing  when  viewed  from behind  as  a  double hemi-
sphere, in  the notch of which the coccyx is buried, but is just percep-
tible to the touch.   These protuberances, when very large, fluctuate
from side to side, and sometimes attain  the weight of  thirty or forty
pounds.
   The  quantity of fat in a moderately fat man is estimated by Beclard
at about the twentieth of the weight of the body.
   Fat is found in the following situations in the human body : in  the
orbits,  in the cheeks, the palms of the hands  and soles of the feet,
at the flexures of the joints, and between the folds of the synovial
membranes of joints, around the kidneys, in the mesentery and omen-
tum,  in the appendices epiploicse, on the heart, in the  subcutaneous
layer of areolar tissue, but especially that of the abdomen, and of the
mammary  region, and in the cancelli and canals of the bones, form-
ing the medulla.   It never occurs in the areolar tissue of the scrotum
and penis, or of  the nymphae,  nor  in  that between  the rectum and
bladder, nor along the median line beneath the  skin,  nor in sundry
other situations.
   Fat is found in the liver, and  in the brain and nerves, and occa-
sionally in other  organs.   In these organs it is not enclosed in vesi-
cles of adipose membrane, but  in the elementary parts of  the  tissues
themselves, as in the epithelium cells of the liver, and in the tubes
and globules of the  nervous substance.
   Development of adipose tissue.—The vesicles of
the adipose tissue  are  originally furnished  with
nuclei,  with a  central granule  or nucleolus.   The
nucleus is  situated on the inner surface of the  cell-
membrane, or,  if this be thick,  in  its substance.
The nucleus is speedily absorbed, and never after-
wards appears.   Thus it is probable that the origi-
nal development-cell assumes a permanent form in
the adipose vesicle.
   Formation of  fat.—Many facts  prove that  the   a fat-ceii, to show
 t         e r "f     ^     1 r     ,1   i 1   1    a 11  ,lle  nucleus;   Iroin
elements of fat are derived from  the  blood.   All  s.hwaim ;—c.  Tim
the most recent analyses of  that fluid assign to it a  a^Tht nuc?e'us1.brane'
certain  proportion of both the crystalizable and the
oily portion of  the fat;  according to Lecanu, about four parts in a
thousand.  In  some  instances, the  fatty matter  accumulates  in  the
blood ;  cases of  which  have been recorded by Morgagni, Hewson,
Marcet, Traill,  and Babington.   In  such  cases the serum is opaque
and nearly as white  as milk, and, on  standing  a short time, a film
forms on the surface like cream.  On the addition of ether, the creamy
pellicle is dissolved, and the serum  loses its opacity.   M. Blainville
relates that, in  dissecting  the last elephant which died  at  the Jardin
des Plantes, he happened to wound the jugular vein, and the next
morning he found that the  stream of blood, which  flowed from  the
vein, had deposited on each side a considerable quantity of a fine fatty
matter,  which  on analysis he found  to have exactly the composition
of ordinary fat.
  From what source  is this fatty material  furnished to  the blood ?
 
94
ORGANS OF LOCOMOTION.
From fatty matters  introduced into the system in the food whether
in animal or vegetable substances ;  probably, also, from  those parts
of the food, which, in composition, resemble fat most nearly, such as
the non-nitrogenized articles of diet, starch, gum, sugar, alcohol, beer,
&c.   Liebig states, that, by the separation  of a  small proportion of
oxygen, any of these substances will present a composition similar to
that of fat, and that an equivalent of starch may be changed into one
of fat, by  giving up one equivalent of carbonic acid,  and seven equi-
valents of oxygen.
   If, then, the system be  imperfectly supplied  with oxygen, while
organic compounds containing  carbon are furnished to it  in con-
siderable quantity, the  most favourable conditions will exist for  the
development of fat.  The  oxygen required will be  abstracted from
the carbonized food, which,  by that diminution  of  oxygen, will be
changed into a fat.   On the other hand, exercise  and labour, which
increase the supply of  oxygen, diminish or prevent the formation of
fat.  " The production of fat," says Liebig, " is always a consequence
of a deficient supply of  oxygen, for  oxygen is  absolutely indispen-
sable for the dissipation of the excess of carbon  in the food.  This
excess of  carbon, deposited in  the form of fat,  is never seen in  the
Bedouin or in the Arab of the Desert, who exhibits with pride to  the
traveler his lean, muscular, sinewy limbs  altogether free  from fat;
but in prisons and gaols it appears as a puffiness in the inmates, fed,
as they are, on a  poor and  scanty diet; it appears in  the  sedentary
females of oriental countries;  and, finally, it is  produced under  the
well-known conditions of  the fattening of domestic animals."  (Lie-
big's Organic Chemistry of Physiology.)
   A good  illustration of those views is afforded by the  carnivorous
animals.   In  the wild  state, living  entirely on  azotized food,  and
enjoying abundance of air and exercise, they are lean ; but, when
domesticated,  living on a  mixed diet, devouring a  highly carbona-
ceous food, taking little exercise, and being imperfectly supplied with
oxygen, they grow fat.
   In animals  that hybernate, fat is deposited in  enormous quantity
just prior  to the hybernating period, and during that time it gradually
disappears, supplying nutriment to the  system, and carbon for the re-
spiratory process. These facts were clearly ascertained, in hedgehogs,
by the  celebrated Dr. Jenner.
   Liebig supposes that the formation of fat  is attended with the  de-
velopment of  heat,  for the oxygen disengaged in  this process unites
with carbon derived from  the same or a  different  source, and an
amount of heat is generated proportionate to the quantity of carbonic
acid thus  formed.  But  it may  be  fairly questioned,  whether  the
temperature of the body is thereby elevated, since the separation of
the oxygen would be doubtless attended by a  degree of cooling suf-
ficient to neutralize the heat developed in  the formation of carbonic
acid.
   Lastly,  fat,  being a bad conductor of heat, is useful for retaining it
in the  bodies  of  animals.   Hence those animals that have little hair
on their skins, have the greatest quantity of subcutaneous fat.  This 
CARTILAGE.
95
is remarkably the case in the seal  tribe, which has a large quantity
of fat  between the skin  and its  muscle, and is  almost devoid  of
cutaneous covering ; and,  in man,  the subcutaneous fat, which  is  so
generally met with, even in  apparently lean subjects, is doubtless  a
protection against cold.

  The following works may be consulted on the subjects discussed  in this chapter:
—The treatises on General Anatomy by Bichat, Beclard, Craigie, and Henle; Hilde-
brandt's Anatomie, by Weber; Blainville, Lecons de Physiologie; Liebig's Organic
Chemistry; Hunter's remarks on Fat,in the Catalogue of the Hunterian Museum,vol.
iii. p. 2.
                          CHAPTER IV.

   PASSIVE ORGANS OF LOCOMOTION, CONTINUED.--OF CARTILAGE AND
                         FIBRO-CARTILAGE.

   Cartilage is extensively used in the animal frame, and is one  of
 the simplest of the textures.  Like the adipose tissue, it approaches
 very closely in its  intimate  structure to the cellular tissue of vege-
 tables.
   In the development of the embryo,  it is one of  the first tissues  to
 appear as a distinct structure, and it constitutes the internal skeleton
 in its earliest condition in the animal scale.  The rudimentary skele-
 ton of the cephalopoda consists of it; and in one class of fishes (hence
 termed cartilaginous,  as the shark, ray, lamprey) the skeleton is en-
 tirely composed of it.
   In man, and the higher animals, cartilage is  employed temporarily,
 as a nidus for bone, in the  early stages of life, and is then  called
 temporary cartilage.   This, at a  certain  period, begins to  ossify, and
 finally disappears by being  converted  into bone.   At  one time, the
 greatest part, if not the whole,  of the skeleton is  cartilaginous ; and
 for a considerable period after birth the extremities of the  long bones
 are  chiefly composed of cartilage, and  the larger processes are  con-
 nected to  the shaft of the bone  by this  substance.
   For other purposes,  however, a cartilage is  employed which is not
 prone to  ossify, viz., permanent  cartilage, and this is used either in
 joints {articular cartilage), or  in the  walls of cavities {membrani-
form cartilage). The  articular variety is  either disposed as a  thin
 layer between two  articular surfaces,  and equally adherent to  both,
 as in the synarthrodia! joints (the cranial  sutures,  the  sacro-iliac
 symphyses, &c.) ;  or  it forms an encrustation upon the  articular
 ends of the  bones entering into the  composition of diarthrodial
 joints;  thus,  the extremities of the femur, tibia, the arm-bones,  &c,
 are  all coated with a layer of cartilage, moulded to the shape of the
 articular surfaces.   The membraniform  cartilages  are not  employed
 in connection with the locomotive mechanism, but serve to guard 
96
ORGANS OF LOCOMOTION.
the orifices of canals or passages, or to form  tubes, that require to
be  kept permanently open;  the elasticity  of the material  affecting
this without the expenditure- of  any vital force.   Thus we  find  this
variety  of cartilage in the external  ear, in the Eustachian  tube, in
the nostrils  and eyelids,  and in  the larynx, trachea, and  bronchial
ramifications.
  Physical  characters.—Cartilage, in  colour, varies from an azure,
or pearly white, to a whitish yellow.   The temporary and  articular
varieties present the former colour;  the membraniform,  for the most
part, the latter.
  Elasticity, flexibility, and considerable cohesive power  are the chief
physical properties of this texture;  and in these  qualities, and espe-
cially in the first, consists its great value, both in  contributing to the
perfection of the locomotive  apparatus, and in its  adaptation to other
purposes.  Cartilage is not brittle  :  a thin piece may  be broken
across by being  suddenly bent at a very acute angle ; but, in general,
cartilage will  bend easily without the  occurrence of fracture,  and
will speedily resume its former direction on  the bending  force being
removed.
  Structure.—The simplest kind of  cartilage  consists merely of  nu-
cleated  cells, and exceedingly resembles the cellular tissue of plants.
The cells are very large,  roundish or  ovoidal, and more  or  less flat-
tened by their mutual contact.   Each has  a diminutive  transparent
nucleus attached to the inner surface of the cell-membrane,  and con-
taining  within it a minute granule, or  nucleolus.   We have also  met
with other transparent globules, of variable size and extreme  delicacy,
within the cells.  Some white fibrous tissue usually encloses the mass
of cells, and penetrates to a  certain  distance among the  more super-
ficial of them, which are smaller and more densely packed  than  the
rest.
  This  kind of cartilage is found in  the chorda dorsalis,  or rudimen-
                      tary spinal column of the early embryo : it  also
       Fi§-13-         exists in the permanent chorda dorsalis of the
                      cartilaginous  fishes, and may be well seen in
                      a thin piece of that structure from the lamprey
                      (fig. 13).
                        But, in  other kinds  of  cartilage,  the  cells
                      are imbedded in an intercellular substance, or
                      matrix, more  or less abundant in the differ-
                  2    ent kinds, and  presenting  certain varieties of
                      appearance.  In all, it is possible  to  see  that
                      the cells have  a proper   membrane   of  their
                      own,  and  are not mere excavations in the in-
  Four nucleated cells from  tercellular substance ; this  mav often be deter-
the  Chorda Dorsalis  of the    •   i  ,   11     i     , J       u«- vi«-«»
Lamprey :-i. Nucleus, wnh  mined at  a broken  edge,  the cell-membrane
nucleolus.  2. Another, seen  nmioftln™ .   U.,4-  \t-  :
in profile.                projecting:   but  it  is  not  easy to  extract
                      a  cell entire, apparently  on account of the
delicacy of its texture, and  the density of the surrounding mass.
   In temporary cartilage  the cells are  very numerous, and situated at
nearly equal distances  apart in the  intercellular  substance  which is
 
CARTILAGE.
97
Fig. 14.
not abundant.  The cells vary in shape and size, but most are round
or oval.   Their nuclei are for the  most part minutely granular ;  the
granules being, in some  specimens, at a  distance from  one  another.
When ossification  begins,  the cells, which hitherto were scattered
without  definite  arrangement, become disposed in clusters or rows,
the ends of which are  directed towards  the ossifying  part.   These
and other changes  will be described in the chapter on bone.
   In articular cartilage the cells are oval or roundish, often disposed
in small sets  of 2, 3, or 4  irregularly disseminated through a nearly
homogeneous matrix, which is more abundant than in the last-named
variety ; fig. 14, 1.  The cells measure  from T/ff5 to §1$ of an inch.
The nuclei are for the most part  small.   In the interior part of the
cartilages of  encrustation we usually find the
cells assuming more or less of a linear direc-
tion, and pointing towards the surface; fig. 14,
3.   This arrangement is probably connected
with a corresponding peculiarity of texture of
the intercellular substance, but which  it is
more difficult to  distinguish ; for these speci-
mens have a disposition to fracture  in a regular
manner along planes vertical to the surface,
and the broken surface is striated in the same
direction.
   Near its deep or attached surface, articular
cartilage blends gradually with the bone it in-
vests.   The  ceils  in the neighbourhood,  as
well as their  nuclei, are  surrounded with a
sprinkling of fine opaque granules, which seem
to  be a rudimentary deposit  of bone.   The
true bone  dips unevenly into the substance of
the cartilage.
   A pavement of  nucleated  epithelial parti-
cles has been described by Henle  to exist  on
the free surface of articular cartilage.  In the
foetus this  may be readily seen  ;  but in  the
adult we have often failed to detect it, even
in  perfectly fresh  specimens, and  notwithstanding great care.   An
irregularity of surface, like that represented in fig.  14, 2, often exists,
and seems to show that this covering ceases when the part becomes
subject to  friction  and pressure.    Cells, too, are often  seen  close to
this surface, and even partly projecting from it; appearances indica-
tive of attrition.
   In the cartilages of the ribs, which occupy an  intermediate place
between the articular and membraniform  varieties,  the cells are larger
than in  any other  cartilage in the  body, being from  eio to 4^0 °f an
inch in diameter.  Many of them  contain two or more  nuclei, which
are clear and transparent; and some seem to contain a few oil-glob-
ules, a  condition  occasionally  met with  in other  varieties.   The
cells often affect a linear arrangement.   The rows  of them are turned
in  all directions, and have the appearance of having been formed by
 Articular cartilage, from the
head of the Humerus:—Vertical
sections: 1. Section close tothe
surface, 2. 3. Section far in the
interior. —Magnified 320 diame-
ters. 
98
ORGANS OF LOCOMOTION.
Fig. 15.
the division  of one cell, and  the  separation  of its parts  from each
other.   It  is probable that the splitting of the nucleus may be  the
                               first step in this  process,  as, tor  ex-
                               ample, in fig. 15, a.
                                  The intercellular substance is very
                               abundant  in  these  cartilages;  and
                               though it usually presents, on  a sec-
                               tion,  a very finely  mottled aspect,
                               such  as is very correctly portrayed
                               in the figure, yet we may often  dis-
                               cern  in it  a most distinctly fibrous
                               structure,  in which  the  fibres  are
                               parallel, and which  is  most evident
                               in the aged.  Perhaps it would be
                                most  correct to say that these fibres
                                are only formed by an artificial  dis-
                                integration, for  they are  aggregated
                                into a solid mass in the unmutilated
                                structure.   They  have  very  little
                                resemblance  to  the  white  fibrous
                                tissue.  It  is  not  known  whether
                                they take any constant direction.
   In the true membraniform  cartilages, the  cells  are very numerous
 in proportion to the surrounding substance, which is consequently in
                           small quantity.   This  intercellular  matrix
                           is very  distinctly fibrous towards the  ex-
                           terior   of these cartilages,  and  often  in
                           their interior, but with  considerable  va-
                           riety.   The thyroid and cricoid cartilages,
                           and the rings of the trachea, seem  chiefly
                           composed  of clearly defined and  roundish
                           nucleated  cells,  huddled together, as it
                           were,  in a promiscuous manner, fig. 16.
                           In specimens from persons of adult  age,
                           the cells have frequently a fine granular
 opaque matter  sprinkled on  their exterior;  and  these, in older  sub-
 jects, are seen to have become  minute centres of a  spurious ossifi-
 cation.
    In the cartilage of the ear the cells are  small, and very close to
 each other; in shape  they  are very  uniform, and vary in size  from
 __!_7 to a^ °f  an incn-   A piece  of this cartilage, when examined
 by a  high  power, has very much the appearance of a sieve;  the
 holes of which are  occupied by nuclei and their nucleoli.   The in-
 tercellular substance is not exactly white fibrous tissue ; but so nearly
 resembles it, especially towards  the  surface, as to make this  form of
  cartilage approach fibro-cartilage more nearly than does  any other.
    The membraniform  cartilages  are invested  by a layer of  white
  fibrous tissue containing blood-vessels, and  called the perichondrium.
  Its fibres are densely  interwoven in  all  directions, and  adhere inti-
  mately to the intercellular substance of the cartilage.   This invest-
 Cartilage of the Ribs. . Section showing
the cells, their nuclei and nucleoli. The
transparent spaces result from the reVnoval
of the cells by the knife, their cavities re-
maining.—Magnified 320 diameters.
Fig. 16.
 Thyroid cartilage :—Thin section.
—Magnified 320 diameters. 
CARTILAGE.
99
ment corresponds with the periosteum of bone, and in the temporary
cartilages is  indeed the very same structure.   It is a nidus for  the
nutrient vessels  of cartilage, and often  serves to  give attachment to
muscles.  It is  best examined on  the cartilages  Of the  ribs.  Its
great  toughness is sometimes  well  displayed  in fractures  of these
cartilages, where  the perichondrium  remains untorn between  the
fragments.
   The articular cartilages, which have no perichondrium, are sup-
ported  and  supplied with blood by  the  bone  to  which  they  are
adapted, and by the synovial membrane, which always passes for at
least some little  distance over their free surface.
   Vessels of cartilage.—Speaking in general terms, cartilage may be
styled  a non-vascular substance,  for considerable  masses  of all its
varieties  exist,  unpenetrated  by  a single vessel.    The term  non-
vascular, however, it is important to observe, is  to be understood in
a  relative sense.   All tissues deriving their nutriment  from  blood-
vessels,  are, in  fact, if traced up  to their microscopic elements, on
the outside of the channels through which the blood flows.  If the
quantity of  vessels be large in proportion to the tissue, or if the  two
are mingled  in an intimate manner, we term the part very  vascular.
If, on the other  hand, there be a considerable  mass of tissue, among
the elementary parts of which no vessels penetrate, it is styled non-
vascular.  This word is  not used in  an absolute  sense;  for, if so
used, it  would  apply equally to all tissues, except the lining  mem-
brane of the vascular system  itself, which is probably nourished by
the blood immediately in  contact with  it.
   Returning from  this  digression, we  remark, that  temporary car-
tilage, when in  small mass, is not permeated  by vessels;  but that,
when more than about an eighth of an  inch thick, it contains canals
in its interior,  for  the  transmission of vessels.   These canals are
somewhat tortuous, and  contain  a  delicate extension of  the peri-
chondrium.   They may be regarded as so many involutions of the
outer surface of the cartilage.
   The  same description  will  apply to the various  membraniform
cartilages, with this difference,  that  their blood-vessels  are  less
numerous.  In those which are thin,  no vascular  canals  are  to be
found; but where  there  is much  substance, as  in the  costal carti-
lages, they are easily detected.
   Nothing is more  certain than that articular cartilage, in man, is
not penetrated by  blood-vessels.   Coloured fluids  injected into  the
vessels  cannot be  made  to enter  it, but  are seen  to turn  back, on
reaching it,  into the tissue which conveyed  them  to it.  But we
possess  a more  certain test than this, in the examination of thin
slices of the tissue under  a high power.  This  brings no vessels into
view:  on the contrary, it  proves their non-existence, beyond dispute.
In some diseased states,  however,  the presence of  a  few vessels
seems to have been established.
   Mr. Toynbee  {Phil. Trans., 1841) has pointed out, that the vessels
of bone, at the part on which  cartilage  rests, are  separated  from  the
cartilage  by a  bony lamella,  in  which  no apertures  exist.   The 
100
ORGANS OF LOCOMOTION.
minute  vessels,  on  approaching this  lamella,  seem  to  dilate, and
then, formino- arches, they run back into  the  cancelli of the bone.
Such an arrangement must, of course,  be attended with a retardation
of the  blood  near the "articular lamella."   The vessels of the syno-
vial  membrane advance with it a little way upon the articular surface
of the  cartilage, but only over those parts which are not subject to
pressure during the natural movements of the joint.   These likewise
terminate  in  loops.   In diseased states they often advance far  upon
the cartilage, as they do  naturally, according  to Mr. Toynbee's ob-
servations, during the middle period of foetal life.
                      OF FIBRO-CARTILAGE.

  This  texture is  a  compound of white fibrous  tissue and cartilage
in varying proportions.
  It is principally employed in the construction of joints, and con-
tributes to their perfection at once by its strength  and its elasticity;
but as it is also, to a limited extent,  used for other purposes, it may
be conveniently described as, 1, Articular;  2, Non-articular.
  Fibro-cartilage,  examined  by the  naked  eye,  has much of the
colour and general appearance  of the thyroid cartilage, or of other
examples of the membraniform variety, which Bichat, indeed, classed
among fibro-cartilages.   Its  colour is  white, with a  slight  tinge of
yellow;  it is interspersed by the shining fibres of white fibrous tissue,
and  its  appearance  differs with the  quantity of  that  texture that is
mingled  with it.   Its consistence also varies, for  the same  reason;
in some instances being extremely dense, in others soft, yielding,
and almost pulpy.
  When examined microscopically, fibro-cartilage is found to consist
of bundles of wavy fibres, with the  cells  or corpuscles of cartilage
occupying the spaces formed by  the  interlacement  of the  fibrous
tissue.   This interlacement is often very intricate, and  calculated to
increase  the strength of the structure  in those directions  in which the
greatest toughness is required.
  Physical  and vital properties.—To  the  strength  and  density of
fibrous tissue,  fibro-cartilage  adds the  elasticity of cartilage; it is
more variously flexible than the latter tissue, so that it will not crack
when bent too  much.  Its sensibility  is low, and it is  devoid  of vital
contractility.
   Vessels and nerves.—Its vessels are few, and are derived from the
textures  (synovial  membrane  or periosteum) with which it is in im-
mediate  connection.  Nothing is known  respecting its nerves, if
indeed it possesses them.
   Chemical composition.—Fibro-cartilage contains water; when de-
prived of it by drying, it shrivels up, and becomes hard and yellow.
It yields gelatine in  abundance on boiling.
   Forms of fibro-cartilage. —The  articular  fibro-cartilage  is  that
which is found most extensively, and it exists in three forms,  a. As
discs, interposed between osseous surfaces, and equally adherent to 
FIBRO-CARTILAGE.
101
both, of which the intervertebral discs and the inter-pubic fibro-carti-
lage are instances,  b. As laminae, free on  both surfaces, placed in
the cavity  of diarthrodial joints between the articular surfaces of the
bones.   These are the menisci of authors; they exist in the temporo-
maxillary,  the sterno-clavicular, and the knee-joints,  and between
the  scaphoid and  lunar, and lunar and cuneiform bones,   c. As tri-
angular edges to  the  glenoid and cotyloid  cavities of the shoulder
and hip joints.   These are styled circumferential.
   In examining  these different forms  of fibro-cartilage, some varie-
ties are met with deserving of a brief notice.
   The intervertebral discs consist of concentric layers of white fibrous
tissue, placed vertically between the
surfaces of  the  vertebras:   although
the  layers are vertical, the fibres of
which  each  layer is composed, are
directed obliquely from above down-
wards, and the direction of the fibres
of one layer is such as to decussate
with those of the layer immediately
behind it.   Each pair  of layers of
fibrous tissue is separated by  a la-
mina of cartilage. This arrangement
belongs to   rather  more  than  the
outer third  of the disc; the  central
portion is occupied  by a soft, yield-
ing, pulpy  matter,  which, when  a
disc is cut  horizontally,  rises up
considerably above the surrounding
level.  This soft mass consists of  a
few bundles  of white  fibrous  tissue,
(wavy fibres,) with numerous nucle-
ated cells,  very variable  in  shape
and  size,  loosely interspersed.  It
is  girt by the surrounding  vertical
fibrous layers and their  interposed
cartilaginous lamellae,  and  also  com-
pressed by  the  vertebrae  between
which it is placed; the pulpy matter
being separated from immediate contact with the surfaces of the ver-
tebras by the interposition of thin layers of cartilage.
   In the menisci  the white  fibrous tissue predominates considerably
at their circumferences, while  the  cartilage chiefly abounds in the
centre.  Those of the  knee-joint and temporo-maxillary joint are the
densest: that of the sterno-clavicular is softer and more cartilaginous.
   The circumferential fibro-cartilages  contain a considerable predo-
minance of  fibrous tissue.
   The non-articular form of fibro-cartilage is found deposited on the
surfaces of the grooves in bones, which lodge  tendons;  as, for ex-
ample, the  groove  for the  lodgment of the  tibialis  posticus.  In
intimate structure it  resembles the  articular forms.
 Elementary structures from an interver-
tebral disc;—1, Two cartilage-cells lying
amongst the white fibrous tissue. The re-
maining objects are from the central pulpy
substance, and exhibit various forms of
cell. In several of these there is an ap-
pearance of multiplication by subdivision
of the nucleus, and some seem attached by
a fibrous tissue.  The full meaning of this
does not yet appear. 
102
ORGANS OF LOCOMOTION.
  Reparation and reproduction.—Fibro-cartilage heals by a new sub-
stance of similar texture.   Sometimes the union of bone is effected
by a material of this kind, in cases where osseous  union cannot be
obtained.

  In addition to the works on  General Anatomy mentioned at the end of the last
chapter, we refer to Mailer's Physiology, by Baly, p. 390; the articles Cartilage and
Fibro-Cartilage, in the Cyclopaedia of Anatomy;  and Mr. Toynbee's paper on Non-
vascular Tissues, in Phil. Trans. 1841.
                         CHAPTER V.

      PASSIVE ORGANS OF LOCOMOTION, CONTINUED.--OF BONE.

  The distinction of animal textures into hard and soft prevails very
extensively throughout  the animal series.  The former are charac-
terized by containing a proportion  of inorganic material, in combi-
nation with animal  matter, sufficient  to give  them that degree of
hardness which is their principal physical property.
  Among the invertebrated  classes there are  hard  parts, although
very differently constituted from  those of the  higher animals.  They
serve an analogous purpose,—being a basis  of support for the  soft
parts, and in many instances a protection  to them, and affording a  sur-
face of attachment for the muscles  of the animal; thus playing an
important part in its locomotion, or in its ordinary movements.   To
this category we may refer the earthy support  to the soft fleshy mass,
whether as an internal stem or axis, or as an external covering, which
is to be found among the polypifera, performing a function similar to
the skeleton of  the  higher animals, and composed of carbonate of
lime, with a little phosphate, in  combination with a small quantity of
animal matter.
  The calcareous plates of the star-fish and sea-urchin, {asterias and
echinus,) the hard coriaceous  covering of insects, the  hard  external
integuments of Crustacea, and the infinitely various shells of the  gas-
teropoda and conchifera, must  all be  regarded in the light of hard
parts performing the offices above referred to.
  The skeleton of the higher animals is internal; it  is clothed by
the muscles and other soft parts.  The first example  of this arrange-
ment is  met with in the cephalopodous mollusks, in  which certain
cartilaginous plates are  enclosed in the  body  of the animal, protect-
ing certain parts of the nervous system.   The skeleton of the lowest
organized fishes, although much more extensive, and of a  more com-
plicated  arrangement, is yet  placed but  little above  that  of those
animals.  It is composed of a kind  of cartilage, which in its greater
density,  and in  its having a  certain quantity of calcareous deposit
around it, approaches the nature of the skeleton of the higher classes.
   Bone  is the  substance employed to form the internal skeleton of
the osseous fishes, of reptiles, birds, and mammalia.  It forms organs 
BONE.
103
 of support, or levers for motion, or it encloses cavities affording pro-
 tection to soft and vital organs.
   To a superficial  examination bone presents  the following proper-
 ties: hardness, density, a whitish  colour, opacity.   An  examination
 of its physical constitution will explain these characters.
   Bone contains less water than  any other organ in the body; and
 exposure to air, even for a short time, removes the fluid by evapora-
 tion:  to this, in part, may be attributed its hardness.  Bone consists
 of an  inorganic  and an organic  material,  which  may  be obtained
 separately by very simple processes.  Steep a bone in dilute mineral
 acid, muriatic or nitric; the earthy matter is  dissolved out by the
 acid, and the organic substance remains, retaining the original  shape
 and size  of the bone.  In fact, we obtain, by this process, the carti-
 laginous  nidus of  the bone,  upon  which its  form  depends.   The
 vessels of the bone ramify throughout this mass; for if they have
 been injected, previously to the action of the  acid, they will be dis-
 tinctly seen ramifying through the  semi-transparent animal substance.
 A preparation of this kind dried, and afterwards  preserved in spirits
 of turpentine, serves beautifully to exhibit the disposition of the ves-
 sels in bone.
   By subjecting  a  bone to a  strong heat in a crucible, the animal
 part will be burnt  out, and the earthy part will  remain.  Still  the
 bone  retains its  form, but  the cohesion between  the  earthy particles
 is extremely slight, so that the least touch will destroy its continuity;
 a fact which obviously points to  the animal matter  as  affording to
 bone its strength  of cohesion.
   Bone may be  deprived  of its  animal matter by  long-continued
 boiling, under strong pressure, in  a Papin's digester.   The animal
 matter  is extracted, in combination with water, in the form of gela-
 tine; and the  weight of the quantity which may thus be  obtained
 will,  owing to this  union with water, exceed by three or four  times
 that of the bone itself.
   A  certain proportion  between these two constituents  of bone is
 necessary to the due maintenance of its physical properties.  To  the
 earthy part  it owes  its hardness, its  density, its little  flexibility: but
 it is  equally necessary for these properties  that  the  animal portion
 shall be healthy, and in proper quantity; for the cohesion  of the par-
 ticles of the  former is secured entirely by it.  A  due proportion  of
 the animal part  gives bone a certain  degree of elasticity; and, were
 it not for  the earthy matter, bones  would be exceedingly flexible,  as
 may be shown in a bone deprived of its calcareous matter by acid.
 Hence  old bones, in which  the animal matter is less abundant,  as
 well as perhaps defective  in  quality, are  more  brittle  than young
 ones, and old persons are more liable to fractures.   But in the young,
in whom the organic processes are active, and whose animal matter
is fully  adequate  in  quantity and quality to the wants of the system,
the bones possess their due degree of flexibility,  and  hence in  them
fractures  are less frequent;  the  cohesive force of the  bones being
sometimes so  considerable, that they will bend  to a great degree
before yielding. 
104
ORGANS OF LOCOMOTION.
  The following table from Schreger illustrates the relative propor-
tions of the two constituents, at three periods of life,  in 100 parts of
bone:
                             Child.     Adult.      Old.
             Animal matter     47-20     20-18      12-2
             Earthy matter     48-48     74-84      84-1
Or  it may be stated  in general  terms, that in  the child  the  earthy
matter forms  nearly one-half the weight of the bone,  in the adult it
is equal to four-fifths, and in the old subject to seven-eighths;  a con-
clusion agreeing in the main with that drawn from the  analyses  of
Davy, Bostock, Hatchett, and others.
  It had long been known that  certain bones of the body contained
these constituents  in  other  proportions than those named; for ex-
ample, the petrous portion of the temporal bone had  been shown by
Davy to owe  its stony hardness to a large proportion of earthy matter.
But Dr. G. 0. Rees has lately pointed out some  interesting particulars
as to the relative proportions of these elements  in  the composition of
different bones.
  The long bones of  the extremities have, according to  Dr.  Rees's
analysis, more  earthy matter than  the bones of the trunk.   The
bones  of the upper extremity have a larger proportion of the same
material  than those  of the  corresponding  bones  in the  lower; the
humerus has more than the  radius and ulna;  the femur more than
the tibia and fibula;  while the  bones of the  fore-arm,  as well  as
those of the  leg, are  respectively alike in  constitution.   The verte-
brae,  ribs,  and clavicles  are similarly constituted.  The ilium has
more earthy  matter than  the  scapula or sternum  ; the bones  of the
head have more of this material than those of the  trunk.
  In the foetus the same law prevails as regards the relative quantity
of  the earthy matter, excepting that  the long bones, and  the  cranial
bones, do not contain the excess of earthy matter which characterizes
them in the adult.
   The diseased state, called Rickets, so common  in the children of
scrofulous parents, and in the ill-nourished ones of the lower  orders,
consists  in a deficient deposit of earthy matter;  the  animal  matter
being  probably  of an  unhealthy quality.   In this  disease the bones
are so flexible, that  they bend under the  weight that they may  be
called on  to support, or under the action of the  muscles.  The
lower extremities  exhibit deformity first, and to the greatest degree,
and the direction in which they become bent is evidently influenced
by the superimposed weight; the bend almost  always appears as an
aggravation  or the natural curves of the bones.   The ricketv femur
has always its convexity directed forwards:  the tibia is  convex for-
wards and outwards, and  the fibula follows the same direction.  When
the nutritive powers of the system are  fully restored, the deposition
of  earth  goes on in its healthy proportion, the animal  matter becomes
healthy, and  the bones acquire their  due degree of strength and hard-
ness.  In  the tibia of a rickety child, Dr. Davy found, in 100 parts,
74 parts animal matter, and 26 earthy; and Dr. Bostock found in the
vertebra of a similar subject 79-75 animal, and 20-25 earthy. 
BONE.                          105
   The brittleness of the bones in old age is due to an opposite cause,
 namely, the  defective deposit of animal matter, so as to give to the
 earthy matter the  undue preponderance already specified.   But this
 state cannot  be looked upon as morbid ; it is the natural result of the
 feeble condition of  the powers of nutrition, which ensues in the ad-
 vance of years;  and it will vary, in different individuals, according
 to the original strength of constitution of each, and according to the
 freedom from exposure to debilitating influences.
   That  state of bone which accompanies malignant disease (cancer,
 or fungoid disease) in adults or old  persons, and which some patho-
 logists have designated mollities ossium, results from the dissemination
 of cancerous matter through the system.   In this disease the whole
 nutritive process of bones seems tainted ; the animal part is  not so
 much deficient in quantity, as bad in quality; the physical, as well as
 the  vital properties of the bone are completely deranged ; the osseous
 texture has lost its  cohesive power.   Hence  these bones often break
 on the  application  of the slightest force, or on the feeblest exercise
 of the muscles.   They are soft, too, in the recent state; the  knife will
 sometimes penetrate them ; and they  are often pervaded by  a  con-
 siderable quantity of oil.
   Bones possess  a  remarkable power of  resisting decomposition.
 Even the animal part seems to acquire  this power through its combi-
 nation with the earthy.  This is manifest from analyzing bones which
 have been long kept, or fossil bones.   Cuvier states that  the latter
 bones exhibit a considerable cartilaginous portion ; and Bichat found
 that clavicles, which had  been exposed for ten years to the wind and
 rain at the cemetery of Clamart, presented, under the action of acid,
 an abundant  cartilaginous parenchyma.  In  an  old Roman  frontal
 bone, dug up from Pompeii, Dr. Davy  found  35-5 animal parts, and
 645 earthy;  and in a tooth of the mammoth, 30-5 animal, and 69-5
 earthy.
   The animal part of bone consists of cartilage, with vessels, medul-
 lary membrane, and  fat.   The  cartilage, is readily convertible into
 gelatine, according to Berzelius, after three hours' boiling ; and, when
 this has been removed, there  remain  only  four grains  out of 100,
 which may be considered  to have been  composed of blood-vessels.
   The earthy part  of bone  consists  of phosphate and carbonate of
 lime, with a  small quantity of phosphate and carbonate of magnesia.
 The phosphate  of  lime  forms  the principal  portion of the  earthy-
 part; in 100 parts of bone Berzelius  found  51-04 of this  salt.   It
 was discovered by Gahn, and  the discovery announced by Scheele,
 that bone-earth consisted  of "phosphoric acid and lime."   Accord-
 ing  to Berzelius, the phosphate  consists of eight atoms of lime and
 three atoms of phosphoric acid ;  but Mitscherlich regards it as com-
 posed of three atoms of lime with one of phosphoric acid (a tribasic
 salt).  It may be formed artificially by  dropping chloride of calcium
into  a solution of phosphate  of soda.   It appears as  a  gelatinous
precipitate, which does not crystalize, and is readily soluble in acids.
  The existence of fluoride of calcium in bone was announced many
years ago by Berzelius;  but the observations of our friend, Dr. G.
     8 
106
ORGANS OF LOCOMOTION.
 0. Rees, throw  considerable  doubt  upon  this assertion. Dr.  Rees
 attributes the action of  the supposed fluoric acid upon glass to phos-
 phoric acid in combination with water, which, if  heated on glass of
 inferior quality until it volatilizes, will act  upon it with  considerable
 energy.   The proportion  of carbonate of lime to the phosphate is
 small.  According to Berzelius, there are 11-30 parts in  100 of bone.
   We subjoin the following process, by which the qualitative analysis
 of bone may be readily  effected :
   In order to insulate  the animal matter,  digest the bone for some
 days in muriatic acid diluted  with  about  thrice its bulk of water ;
 the  earthy  constituents  will thus be gradually removed, leaving a
 semi-transparent cartilaginous tissue  behind.
   The  earthy matters are  best examined  by  treating  a portion of
 burnt bone  with nitric  acid, diluted with from four to  six  times its
 bulk of water;  brisk effervescence ensues, proving the  presence of
 carbonic acid.  Filter the acid  liquid after diluting it with water,  and
 add  solution of caustic  ammonia  as  long  as the precipitate  at  first
 formed  continues to be  redissolved  by agitation ;  then add  solution
 of acetate  of lead till it no longer  occasions  any precipitate.  The
 dense white precipitate  thus produced consists of phosphate of lead,
which melts before the blow-pipe,  and on cooling assumes its charac-
teristic crystaline structure.
  Through  the  solution, filtered from the  phosphate of  lead, pass a
 stream of sulphuretted hydrogen to remove the excess of lead; warm
the liquid, to drive off the superfluous gas,  and filter: then neutralize
                                      by ammonia, and add oxalate
                                      of ammonia as long as  any
                                      precipitate occurs; abundance
                                      of oxalate of lime will fall as
                                      a white powder.
                                        Evaporate the filtered liquid
                                      to dryness; ignite the residue,
                                      and wash with hot water ; the
                                      magnesia will be left  behind
                                      in a pure form.
                                        In examining a section of
                                      almost any bone, we  observe
                                      two varieties of osseous sub-
                                      stance : the one  dense, firm,
                                      compact, always situated on
                                      the   exterior  of  the  bone,
                                      either as a  thin layer, or as a
                                      dense   thick  structure  pos-
                                      sessed  of great strength; the
                                      other loose, reticular, spongy,
                                      enclosing  spaces  or  cells,
                                      which   communicate   freely
                                      with each  other, and  which,
                                      being called cancelli, give to
this  kind of osseous tissue the name cancellated.   These  cells  are
Fig. 18.
 Vertical section of the upper end of the Femur, show-
ing the cancellated and compact tissues. 
BONE.
107
 formed  by an interlacement of numerous bony fibres and lamina?,
 which although  to a superficial observation exhibiting an  indefinite
 arrangement, have nevertheless, in those bones which have to support
 weight, a  more  or less perpendicular direction.   The  cancellated
 structure of bone is always situated in its  interior,  enclosed and pro-
 tected by the compact tissue.
    The  relative  situation of these  varieties  may be well seen in a
 vertical section of one of the long bones (fig. 18).   At the extremities,
 the cancellated texture is accumulated, invested by a thin lamella of
 compact tissue, giving expansion and lightness to  those parts  of  the
 bone.   In  the intermediate portion, or shaft, the  compact tissue is
 highly developed, affording great strength  in the situation where that
 quality is the most needed.
    The compact external surface of bone (except on its articular  as-
 pects) is covered by a firm tough membrane, termed the  periosteum,
 which, like the perichondrium  investing cartilage, consists of white
 fibrous tissue, densely interwoven in all directions.   The cancelli  are
 filled with  fat, or medulla, the marrow of bone.   They are lined by a
 delicate membrane, called  the  medullary membrane, which  serves
 to  support the  fat.   In the shaft  of  the  long bones the  medulla
 is contained not in ordinary cells, but in  one great canal,  which
 occupies the centre of the  shaft,  the medullary  canal.   Here the
 medullary membrane lines the compact tissue  that forms the wall of
 the cavity.
   Both  the periosteum  and the medullary membrane adhere inti-
 mately to   the bone.   Both  are  abundantly supplied with  blood-
 vessels, which, after ramifying  upon them, send numerous  branches
 into  the bone.   These  membranes  are of great importance to  the
 nutrition of the bone, inasmuch as they support its nutrient vessels;
 and, if either of them be destroyed to  any great extent, the part in
 contact  with them  necessarily  perishes :  and they  not  only  cover
 the outer and inner surfaces of the bone, but also  send processes,
 along with the vessels, into  minute canals  traversing the compact
 tissue, and  are, through  the  medium  of these, rendered  continuous
 with one another.
   The great variety of uses to  which the  bones are applied in  the
 construction of the skeleton, occasions much difference of  shape  as
 well as of size.   The following arrangement comprehends  all  these
 varieties, and is  that commonly adopted.   We  classify them  as, 1,
 Long bones ; 2, Short; 3, Flat; 4, Irregular.
   The  long bones  form the principal levers  of  the body ;  their
 length greatly exceeds their  breadth and thickness.   In descriptive
 anatomy, a  long  bone is divided into a shaft, or  central part, and
 two  extremities.   The shaft is never perfectly straight, it  is more  or
 less curved, as in the femur ; and has  always an appearance  as  if,
 while  yet in  a soft and flexible condition, it had  received a  twist,
 and its extremities had been  turned  in opposite directions.   This is
 very manifest in the femur and humerus ;  more especially in the lat-
ter where  the groove, in which the radial nerve runs, is  just what 
108                 ORGANS OF LOCOMOTION.
one mi^ht fancifully suppose to have resulted from such  a cause as
that above named.
  The shaft is  never perfectly cylindrical ; although in some bones
it approaches that form, in others it is prismatic.  It is  hollow, as
already mentioned, and contains medulla.   This arrangement has the
advantage of making the bone very much lighter than it would have
been if solid ; while it is attended with  no sacrifice of strength, since
the central  osseous substance is  that which contributes least to  its
power of resistance.
  The strength of the  shaft is amply provided  for by its being com-
posed of compact tissue, of thickness proportionate to the length of
the bone, and the bore of the medullary canal.   In the curved  bones,
additional strength is obtained in  the position where the bone would
be most likely to yield, by  increased thickness  and density along  its
concavity.   Of this provision a good  example will be found in the
spine of the femur,—a ridge  of extremely dense bone, placed along
its posterior concave surface.   In the bent bones of  rickety subjects
which have become fully ossified, the compact tissue on the concavity
of the bend acquires an enormous development.
  At the extremities of the long bones the  medullary canal  ceases;
the osseous tissue expands ; and the cancellated texture  takes the
place of the compact  substance  of the shaft,  and forms the whole
thickness of these portions  of the bone, the  medulla  penetrating into
its cells.   Here great  strength is  not required, but surface is  needed
for the articulation of the bones together, and for affording attachment
to ligaments and tendons. The cancellated tissue is admirably adapted
to attain this object; for, while by the looseness of its texture it readily
affords an extent of surface, its lightness is such, that even  a consider-
able  bulk of it  does not materially affect the  weight of the bone.
The  surface of  this texture  is covered with a thin cortex of compact
tissue, which is perforated by innumerable orifices for the transmission
of vessels.
  The long bones are the great levers of the  extremities; as the bones
of the thigh and leg, arm  and fore-arm.  Among the bones of the
hand and foot are certain ones which have all the anatomical charac-
ters of the long bones, except that of length ; they, may, therefore, be
grouped together in  a class under the  name of short bones.   These
are,  the metacarpal and metatarsal  bones, and  the phalanges of the
fingers and toes.
  The flat bones are remarkable for their slight thickness ; they are
composed of two  thin layers of compact tissue, enclosing a layer of
cancellated  texture of variable thickness.  Examples of this class
of bone, may be found in most of those enclosing the  great  cavities
of the body ; as the bones  of the cranium, the  ribs,  the scapula, the
os innominatum, all of which will be found to possess the same essen-
tial characters.
   The cranial bones present one  or two peculiarities which  demand
a special notice.   The layers of compact  tissue in them are fami-
liarly known as the tables of the skull:  the outer one  is stouter and
tougher; the inner one denser and much thinner, and therefore more 
BONE.
109
brittle.   The intervening structure is called the diploe; in some places
it is absent, leaving a vacant space  produced by the separation of the
tables, and which communicates with the external air, as in the frontal
sinuses: the diploe is generally a very fine cancellated texture ;  but,
in the mastoid process  of the temporal bone, it is of a  much looser
kind ; its cancelli are larger, and instead of being occupied by medulla,
as  elsewhere, they communicate with the cavity of the tympanum,
and are  therefore always filled with air.   The diploe of the cranial
bones  in birds is everywhere devoid of medulla, and occupied by air,
which gains access to it from the tympanum.
   A fourth group of bones consists  of  those, which seem to combine
many of the offices  and forms of the three preceding ones with cer-
tain characters proper to themselves.   They exhibit much irregularity
of shape and size;  and, on this account, are called  irregular bones.
The vertebras, the tarsal and carpal bones, certain bones of  the head
and face, belong to this group.  Lightness,  with  extent of surface, is
their principal character.  They are composed mainly of cancellated
texture, covered by a layer of compact, and here and there a portion
of compact tissue, for the purpose of affording a firm  bond of connec-
tion of some process to the main part of the boue;  as  the pedicles,
uniting the lamina? to the bodies of the vertebrae.
   In examining the  surfaces of these  different groups of bones, we
are struck with the variety of projections or eminences, and of de-
pressions,  which are found  upon them.  These are of two kinds ;
articular, and  non-articular.   The former are destined for. the forma-
tion of joints: as the head of the thigh-bone, an  articular eminence ;
and the acetabulum, an articular depression.
   The non-articular eminences chiefly  serve as points of insertion for
ligaments and tendons, and exhibit a great diversity of shapes, so that
anatomists  designate them  as tuberosities, tubercles, spines,  crista?,
&c.   The  non-articular depressions serve a similar purpose, and are
equally various in  form, being  described as  fossa?, cells,  furrows,
grooves, fissures, pulleys, &c.
   With  reference to these  eminences and  depressions, it may be
observed that they are well  marked in proportion to  the muscularity
of the  subject.  In the female, for instance, they are  less distinct
than in the male ; in  the powerfully  muscular man they are at the
maximum  of development.   As Sir  Charles Bell  has remarked, a
person of feeble  texture and indolent  habits has the  bone smooth,
thin, and light;  while with the powerful  muscular frame  is combined
a dense and perfect texture of bone, where every spine and tubercle
are well developed.  And thus the inert and mechanical provisions
of the  bone always bear relation to  the muscular power of  the limb;
and exercise is  as necessary to  the perfect  constitution of a bone,
as it is to the  perfection of  muscle.  It is an  interesting fact, that if
a limb  be disused, from paralysis, the bones  waste  as well as the
muscles.
   Of the  Vessels of Bone.—We now proceed  to inquire  into the
manner in which the nutrition of bone  is provided  for.  A texture
containing so much animal matter,  and needing a constant supply  of 
110
ORGANS OF LOCOMOTION.
 inorganic material likewise, must necessarily be largely supplied with
 blood, the common source of the  materials of all the tissues.
   The  blood-vessels of bone are very numerous, as  may be  satis-
 factorily seen on examining a well-injected specimen.   The  arteries
 are in great part continued from those of the periosteum: those which
 penetrate the cancellated texture of the extremities of the long bones
 are very large, and ramify freely among the cancelli.
   The  membrane of the  medulla which is contained  in the  shaft,
 receives its blood from a special artery that pierces the compact tissue
 through  a distinct canal, known  as that  for the nutritious artery.
 This vessel divides into two  immediately on entering the medullary
 canal; of these, one ascends, the  other descends, and both break up
 into a capillary network, anastomosing with  the  plexuses in  the ex-
 tremities of the bone, derived from the arteries  that penetrate there.
 From the copious vascular network thus formed  within the bone, the
 innermost  part of the  compact substance  of the shaft receives its
 blood-vessels.
   In the compact tissue the arteries pass  into very narrow capillary
 canals, most  of which are  invisible to  the  naked eye.  In carefully
 raising the periosteum from a  bone that has been subjected to a little
maceration, the vessels  may be seen in great numbers passing from
that membrane into the  osseous  texture, and many of the larger ones
seem  to  be surrounded by a  sheath derived from the periosteum.
Similar sheaths may be seen  surrounding the vessels  of the  cancel-
lated texture.
   The vascular canals of the compact tissue are styled Haversian, after
                       their discoverer, Clopton Havers.   They are
                       disseminated pretty uniformly through the tis-
                       sue, and inosculate everywhere with one ano-
                       ther.  In the long and short bones they follow
                       the same general direction as the axis of the
                       bone, and  are  joined at intervals by  cross
                       branches.   The meshes thus formed are more
                       or less  oblong (fig. 19).  The deeper ones
                       open  into  the contiguous cancelli, with the
                       cavities of which they are continuous.
                          The  arteries and veins  of  bone  usually
                       occupy  distinct Haversian canals.   Of  these
                       the venous are the larger, and commonly pre-
                       sent,  at irregular intervals, and  especially
                       where two or more branches  meet,  pouch-
                       like dilatations, calculated to serve as reser-
                       voirs  for the blood, and to  delay its  escape
                       from the tissue.  In many of the large bones,
                       particularly in the fat  and irregular ones, the
                       veins  are exceedingly capacious, and occupy
                       a series of tortuous canals of remarkable size
                       and very characteristic  appearance.  These
                       are well described by Breschet in his elabo-
                       rate work  on the venous  system ; from which
Ficr. 19.
 Haversian canals, seen on a
longitudinal section of the com-
pact tissue of the shaft of one of
ihelongbones:—1. Arterial canal.
2. Venous canal.  3. Dilatation of
another venous canal. 
VESSELS OF BONE.
Ill
 Venous canals in the diploe of the cranium.—After
Breschet.
the accompanying figure (fig. 20) is taken.   These canals run, for the
most part, in the cancellated structure of the bones, and are lined by
a more or less  complete layer
of compact tissue, which itself                 FlS- 20-
often  contains  minute Haver-
sian canals.  The veins they
contain discharge themselves
separately on the surface.
   The Haversian  canals vary
in diameter from 25V0  to the
^fo °f and inch, or more, the
average   being  about t£q.
Their ordinary distance from
one another is about T£o °f an
inch.  They may be regarded
as  involutions  of the  surface
of the bone for the purpose  of
allowing vessels to come into
contact  with  it  in  greater
abundance.  It is evident that
the cancelli, and even the great medullary canal itself, are  likewise
involutions of  the osseous surface, though for  a partly different end.
These larger and more irregular cavities in bone  may be considered
as a dilated form of Haversian canals.   They contain vessels not only
for the nutrition of the  thin osseous material forming their walls, but
also for the supply of the fat enclosed within them.
   Thus the true osseous substance may be described as lying in the
interstices  of a vascular membrane, or of a network of blood-vessels.
The most interesting points  in  the minute anatomy of bone relate to
the mode in which nutrition is provided for in those parts not in im-
mediate contact with the blood-vessels.   We  have already seen that
considerable masses of cartilage derive  their nutriment  from vessels
placed on their exterior only, apparently by a kind of imbibition, per-
haps  aided by the presence  of  the  nucleated cells, and  by a  more or
less fibrous texture : but bone, which is of  a far harder and denser
nature, is  unable to imbibe its nourishment so easily.  Hence its
surface is  greatly augmented by tlfe arrangements already detailed;
and, in addition to this, the osseous tissue itself is provided with a
special system  of microscopic  cavities  and canaliculi, or pores, by
which its recesses may  be irrigated, to a degree of minuteness greatly
exceeding  what  could  have been effected by blood-vessels alone,
consistently with the  compactness and density required in the tissue.
The study  of this delicate  apparatus will now demand  attention, but
a few words must be premised  on the ultimate structure of the osseous
tissue.
   It appears from the researches of Mr. Tomes, about to be published
in  the Cyclopa?dia of  Anatomy,  that the ultimate  structure of the
osseous tissue is granular. , The granules of bone are often very dis-
tinctly visible,  without any  artificial preparation, in the  substance of
the delicate spicula? of  the cancelli, viewed with a high power, and 
112
ORGANS  OF LOCOMOTION.
Fig. 21.
in various sections of all forms  of bone.   They may be  generally
obtained in calcined bone, either by bruising a fragment of it, or by
                steeping  it in dilute muriatic acid ; they may also be
                made very evident  by prolonged boiling in a Papin's
                digester.  Those  represented in fig. 21 were obtained
                in the latter mode.   The granules  vary in size from
                __i__. to -tlho of an inch.   In shape they are oval or
                oblong, and often angular.   They cohere firmly toge-
                ther, possibly by the medium  of some  second sub-
                stance.   In some few instances,  Mr. Tomes has met
                with a very  minute network, which seems adapted
                to receive them in its interstices ; but this he considers
                to  require  confirmation.  A frequent appearance of
                the granular  texture is  well represented in fig. 22.
                                                W7here   bone  exists
11' ,'<
 Ultimate granules of
bone, isolated  and in
small masses, from the
FemuT—(From a pre-
paration otiMr. Tomes.)
Magnified  320 diame-
ters.
Fig. 22.
 Two laeunoe of osseous tissue, seen on their surfaces, showing
the disposition of their pores. The granular aspect of the tissue
both on their walls and around them is well represented.—Mag-
nified 1200 diameters. Drawn from a preparation of the cancelli
of the Femur made by Mr. Tomes.
Fig. 23.
 Transverse section of a part of the
bone surrounding an Haversian canal,
showing the pores commencing at the
surface, a, anastomosing and passing
from cavity to cavity — Magnified
about 300 diameters. From a prepa-
ration made by Mr. Tomes.
                 naturally in an exceed-
                 ingly  attenuated  form,
                 it may consist of a mere
                 aggregation   of  these
                 granules,  unpenetrated
                 by   any    perceptible
                 pores.  This constitutes
                 the simplest form  under
                 which  the ' tissue  can
                 present itself.
                    But  all  the  osseous
                 tissue with which  the
                 human anatomist is con-
                 cerned is  of such bulk
                 as to contain  the  series
                 of pores  and  cavities
                 already  alluded  to for
the conveyance of fluid from and  to  its
vascular  surface.   These  pores always
advance into the bone from open orifices
on its surface.  They soon arrange  them-
selves in sets, each of which, after  anas-
tomosing  with neighbouring   ones, dis-
charges itself into a small cavity or lacuna,
in which  its  individual  pores  coalesce.
From the sides of  this lacuna other pores
pass off to similar cavities in the vicinity,
and others proceed from its  opposite sur-
face to  penetrate   still deeper  into the
tissue.   These pour themselves into ano-
ther lacuna, or divide themselves between
two or three, which are connected in like
manner by lateral channels.   From  these
again pass others, which pursue an onward
course from the surface; and so on, until 
LACUN.E OF BONE.
113
the whole substance of the bone is perforated  by them.   The  pores
from the further side of the extreme lacuna? either open on the surface
of  the bone which they may now have  reached, or else take  a re-
curved direction back into the tissue.
   When this beautiful system of microscopic pores and cavities was
first seen, it was not recognized as such.   The lacuna? were imagined
to be solid corpuscles (a name still commonly applied to them), and
the lines radiating from them to be branching threads  of the earthy
constituent of bone.   They may be proved  in  many ways, however,
to be real excavations in the tissue.   With a sufficiently high power
their opposite wralls can be distinctly seen,  as  well as their hollow
interior; but the  most conclusive evidence  lies in our being able to
fill them with fluid.   If a dry section of bone, in  which they  are very
apparent, be moistened with oil of turpentine while in the field  of the
microscope, the course of this penetrating material can  be witnessed,
as it advances  into the tissue.   It is seen  to  run quickly along the
pores from the  Haversian canals, and from the surface of the  speci-
men, where they  have been cut across.  Having entered a lacuna, it
suddenly  extends along the  pores radiating  from it, and, through
these, reaches other lacuna?;  rendering the  tissue transparent by fill-
ing up  its vacuities.   In  parts  where air  has  previously occupied
the vacant spaces, and the turpentine cannot displace it,  the charac-
teristic appearance of  minute  bubbles is often present.
   The lacuna of  osseous tissue, if examined  extensively in  the ver-
tebrate class, are  found  of very  various  shapes : sometimes  scarcely
to be distinguished  from the pores, of which they are simple  fusiform
dilatations ;  at  other times large and bulky, and  forming the point of
junction of a great  multitude  of  pores.  Mr. Tomes has  allowed us

                               Fig. 24,
 Form of various Lacunre, and their pores:—a. Simple irregular cavities, without pores; from an
ossification of the pleura; ft, from healthy bone of the human subject. V. One of the outer lacuna; of
an Haversian system, with the pores all bending down towards the H. canal,  c. Other forms from
human bone, showing the lateral connecting pores.
 d. From the lioa.  Kxternal  lacunre of an H. system, with unusually large pores clipping towards
the vascular surface, d'. Cavity intermediate between a lacuna and a pore.  e. Another variety from
the same reptile—From Mr. Tomes. 
114
ORGANS OF LOCOMOTION.
to represent  the  principal varieties which he has  met with in the
human subject; and some remarkable ones from the lower animals
are shown  (fig. 24) from the same source.  In the true dental sub-
stance, which is a kind  of bone, the lacuna? are  almost entirely defi-
cient, and the pores attain a very singular development, which will
be described  in a subsequent chapter.
  But  though varieties  are occasionally met  with, yet, in  the  true
bone of man  and the mammalia, the lacuna? possess a  very constant
form ; being  somewhat  oval, and more or less flattened on  their
opposite  surfaces.   The two surfaces look  respectively to and from
the nearest surface of the tissue, and meet in a thin edge.   As pores
pass off equally from  all parts  of  the lacuna?, it follows that by far
the greater number pass  to  or from  the surface  of the  bone ;  an
arrangement  admirably  adapted for the transmission of the nutritious
fluids.   The  pores passing from the edge principally serve to connect
together those lacuna? that lie at nearly the same distance from the
surface.  In fig.  22, the lacuna? are seen on their surface ;  in fig. 23,
on their upper edge.
  The lacuna? have an  average length of TgVo °f  an incn> an(l tnev
are usually about half as wide, and one-third as thick.  The diameter
of the pores is from jorjoo to rfrjoo °f an inch.
  The osseous tissue, thus studded by thousands of flattened lacuna?,
which lie  for the  most  part in planes parallel to the surface, has  a
decided disposition to split up into lamina, following the same direc-
tion.  This is more evident in the bones of old persons, and may be
generally promoted by maceration in dilute acid.   It is most apparent
where  the mass of material between two vascular surfaces is  great,
and the series of lacuna?  numerous.   It is probable that this lamellated
structure depends in part on the mode of development and growth of
this tissue, and it perhaps contributes to the perfection of the nutritive
process within it.
  It will now be easy to  comprehend the apparently complex arrange-
ment of the osseous tissue in the interior of  bones.   Let us take, for
example, one of the long bones.   The entire vascular  surface con-
sists of, 1, the outer surface, covered by the periosteum ; 2, the  inner
surface, lined by the membrane of the medullary cavity, and of the
cancelli;  3, the  Haversian  surface, or that forming the canals of the
compact  tissue, and having in contact with it the vascular  network
that occupies them, and which  has been already described.  These
involutions of the surface are so arranged that no part of the osseous
tissue is in general at a  greater distance than T|^ of an inch  from the
vessels that ramify upon them.
  There is a  layer of tissue on the exterior of the bone deriving its
nourishment from the periosteum, and which may be called the peri-
osteal layer.  The lacuna? of this layer all face that  surface, and the
pores of the  superficial  ones open  upon it.  There is another layer,
forming the immediate wall  of the medullary cavity, and termed the
medullary layer.  Its lacuna?, in like manner, face this  cavity ; and
the pores  of the  inner  ones open  upon  it.   This  layer  becomes
variously folded to form the plates and fibres of the cancelli; and all 
LACUNA OF BONE.
115
Fig. 25.
the lacuna? of these face these irregular cavities, and their pores open
into them.   The Haversian surface, too, being an  involution of the
outer and inner surfaces, and serving to connect  them, is, in  fact,
formed by an involution of the periosteal and medullary layers, and
unites these  with one another.   Where  a vessel enters the compact
tissue from the exterior, it carries with it a  sheath  of bone from  the
periosteal layer.   The lacuna? of this osseous sheath, instead of being
turned  outwards, like those of the periosteal layer, preserve their
relation to the vascular surface to which they pertain, and face inwards
towards the vessel.   Wherever the vessel penetrates, whatever direc-
tion it takes, and however it branches, it is everywhere accompanied
by this sheath from  the periosteal  layer, or by offsets from it;  and,
when it enters the medullary canal, its sheath expands into the medul-
lary layer.
   The  vessels of the  compact  tissue are so  close together that the
osseous sheaths respectively surrounding them come into contact and
unite ; and thus all the space between the outer and the inner surface
of the compact tissue  is filled up:  thus, in a word, the compact tissue
is constructed.
   As the vessels of the compact tissue take a longitudinal  direction,
a transverse  section  of the  bone  (fig. 25) will
appear pierced by numerous holes  which are the
Haversian canals cut across.  Each hole appears
as the  centre of a roundish area, which  is the
section  of  an  involuted  periosteal layer now
become a vertical rod, containing a vessel in its
axis.  The Haversian canals vary considerably
in size, and do not maintain a very close relation
to the thickness of their  respective osseous walls.
They are  frequently eccentric, owing to their wall
bulging more in  one direction than another, to fit
in between others in the vicinity: for though the
rods of bone,  containing the vessels, affect the
cylindrical form, they often  present an oval,  or
even a  very irregular, figure, on a section ; their
close package having  modified their form.  The
periosteal  and medullary  layers  are also well
seen on the  same section, the latter curving in-
wards  to constitute  the walls  of the cancelli.
These  two  layers are  of  very  irregular  thick-
ness, as the Haversian rods encroach  on them
unequally (fig.  25).
   On a further examination of such a section, with a sufficient mag-
nifying  power, we observe the lacuna? of the periosteal and medul-
lary layers facing those surfaces, and their pores opening upon them ;
while the lacuna? of each  Haversian layer all face the corresponding
canal, and their pores radiate from it (fig. 26, and the previous fig. 23,
more highly  magnified).  The lacuna?  facing  the Haversian surface
are generally curved concentrically with it.  They are more numerous,
and their pores more abundant, on the side where there  is most osse-
 Transverse section of the
compact tissue of a long
bone ; showing, 1. The pen-
osteal layer. 2. The medul-
lary layer, and the interme-
diate Haversian systems of
lamellae, each perforated by
an  H. canal. — Magnified
about 15 diameters. 
116
ORGANS  OF LOCOMOTION.
Fig. 26.
a
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ous substance, and where it consequently extends furthest  from the
source of nutriment, the Haversian vessel.  The reason of the want  of
                                proportion between the width of the
                                canals, and the thickness of their re-
                                spective osseous walls, appears  to be
                                this, that the larger canals transmit
                                vessels to other parts, besides  con-
                                taining those which nourish their own
                                layer;  while some of them are, no
                                doubt,  in a  great  measure  channels
                                for veins.
                                   The  outer lacuna? belonging  to an
                                Haversian canal sometimes send out
                                pores  to  anastomose  with  those j)f
                                the  neighbouring  rods;   but   this
                                seems  to happen  chiefly where the
                                contiguous  rods  have just  sprung
                                from a common stock.  Occasionally,
                                also,  lacuna?  of irregular shape (as
                                at s, fig. 26) lie in the interval of two
                                or more rods, and communicate with
                                lacuna? of all of them; but, in general,
                                the outermost pores of the extreme
                                lacunae droop  back on all sides (fig.
                                24, b',  d), and  re-enter  the penulti-
                                mate  series of their own rod.
  Owing to this arrangement, there  always appears  a transparent
interval between contiguous rods; the pores and lacuna? not existing
there to  intercept the passage of the light  (fig. 26).   This is  a re-
markable circumstance, and  will be  illustrated when  we  come  to
speak of  the development of bone.
  The lamellated character  of bone can be  frequently distinguished
                                        in the  periosteal, medullary,
                Fig. 27.                   and Haversian  layers ;  and,
                                        in general, wherever several
                                        successive   series of lacuna?
                                        exist.   The Haversian  rods,
                                        however,    are   remarkably
                                        prone to exhibit this appear-
                                        ance, especially under thecon-
                                        ditions previously mentioned
                                        (p. 114). Their lamella?, how-
                                        ever,  are not  concentric,  as
                                        commonly  described.   The
                                        fissures  which  disclose  them
                                        are  indeed  concentric, but
                                        they  are always incomplete,
                                        never  extending  completely
                                        round the canal; so that the
lamella?  run into one  another at  various points.   This  results from
 Part of the preparation represented in the
last figure, more highly magnified : showing
the package of the Haversian systems, and
also the light spaces between neighbouring
ones.  The system, a, appears to fill up an
interval between the others.  The lacuna; are
seen facing the Haversian canals, and their
pores taking a general radiating direction. At
s. an irregular lacuna communicates with the
pores of three contiguous systems.
 Transverse section of the compact tissue of a tibia
from an aged subject, treated with acid; showing the
appearance of lamellae surrounding the Haversian ca-
nals.  Portions of several systems of lamellae are seen.
The appearance of the lacunae, when their pores are
filled with fluid, is also seen, as well as the radiation
from the canals which then remains.—From Mr. Tomes. 
LAMELLAE OF BONE.
117
the fact, that the lacuna? are not arranged in sets equidistant from the
centre,  but are scattered, as it were, independently of one another, at
every possible  variety of distance from the  canal (figs.  23 and 27).
The larger concentric cracks, which generally run through the lacuna?,
seem  to occur where two or three of these happen to lie nearly in the
same  curve.   Bone is very apt  to crack in  the  interval  between the
rods ; and each of these rods is really so distinct  from those near it,
that it may be designated  conveniently, for the purposes of  descrip-
tion, as an Haversian system of lamella.
   In a  longitudinal section  of the  compact  tissue of a long bone
(fig. 19, p. 110) the appearance of lamellation is  generally less evi-
dent, except where a longitudinal canal  happens to lie exactly in the
plane of section.  When the Haversian canal is a little below the cut
surface, it is of course  covered by some of its lamella?, the lacuna?
of  which directly  over it are seen in face, while the lamella? dipping
in on either  side, in their course round the canal, present the thin
edges of their lacuna? to  the observer.   In the former part those pores
alone are seen that proceed from the edge of the lacuna?; while in the
latter those from both surfaces are seen, and of course  appear much
more numerous.
   The  description now given of the intimate texture of the compact
tissue of  long and short  bones  will apply, in  all essential respects, to
every other example of the compact tissue; the chief difference con-
sisting  in the  direction taken  by the Haversian canals, which is
irregular where  the  tissue follows an  irregular  course.  In general,
however, the  canals, with the Haversian rods forming their sheaths,
run in the direction in which the  tissue needs the greatest strength.
Thus, in the long  bones  it is vertical; and in those flat bones, which
have to  support  weight, it is also more or less vertical; while in those
designed  to sustain the action of forces  of other kinds it is liable to
corresponding variety.
   So  beautifully mechanical is this disposition of  the Haversian sys-
tems in  the compact tissue, that we need not smile at the descriptions
of Gagliardi, who, with  imperfect means of observation, appears to
have been at least faithful in his attempts to delineate nature.   The
periosteal and medullary layers are true plates of bone, and  the Ha-
versian  systems  are true fibres or pins, all connected with one another
by direct  continuity of tissue, and most artfully arranged for the me-
chanical ends in view ;  and we cannot sufficiently admire the skill
which has caused  the means, employed for  these  ends, to conspire
with those which were  indispensable for the due nutrition of the
tissue.
  In the  ordinary cancellated  texture, each  cancellus  must be re-
garded  as a  little  medullary cavity, containing, as it does,  medulla
and highly vascular medullary membrane.  The plates of bone which
form its walls  consist of lamella?, among which  lacuna?, with  their
pores, are scattered ; and they sometimes, when thick, contain Haver-
sian canals.   Usually,  however,  the  pores  of these lamina?  com-
municate  directly  with the cavity of the cancellus to  which  they
belong. 
1X8                 ORGANS OF LOCOMOTION.
   Nerves of  Bone.—The skill of anatomists has  hitherto failed to
demonstrate the presence of nerves in the interior  of bones.   Some
nerves pass through bones,  but no supply  strictly to the osseous mat-
ter has yet been proved.  Yet there  is little doubt  that the vascular
surface of bones  is furnished with nerves :  the  painfulness of many
affections of the periosteum, and  of the medullary  membrane seems
to place this beyond dispute.
   Development.—In the earliest period at which the skeleton  can be
detected among the other tissues of the embryo, it is found to  consist
only of a congeries of cells, constituting the simplest form  of car-
tilage.  These increase in number and in density,  and become sur-
rounded and  held  together by an intercellular substance  in small
quantity; thus forming the temporary cartilage, which  subsequently
becomes converted into  bone.  The temporary cartilages have the
same general  shape before as  after  their ossification ;  and  as this
process is slow, and not finally completed until adult age, they share
during a considerable period in the functions of the bony  skeleton.
   Until the completion of the process of  ossification, the temporary
cartilages increase  in bulk by an interstitial development of  new
cells.  A few vessels, also,  shoot  into  them at  an  early period,
occupying  small  tortuous  canals, which subsequently become  obli-
terated.
   Ossification commences in  the interior of the cartilage at deter-
minate points, hence called points or centres  of ossification.   From
                              these  the process advances  into the
           Fig. 28.             surrounding  substance.   The  period
                              at which these points  appear varies
                              much  in  the different  bones, and in
                              different parts  of them.   The first is
                              the clavicle, in which  the primitive
                              point appears during the fourth week;
                              next is the lower  jaw ; the ribs, too,
                              appear very early, and are completed
                              early  ; next the femur, humerus, tibia,
                              and  upper jaw.   The  vertebra? and
                              pelvic bones are late, as well as those
                              of the tarsus and metatarsus.   Some
                              bones do not begin  to ossify till after
                              birth,  as the patella.
                                 In  most bones ossification  begins
                              at more than  one  point.  Thus, in
                              the long  bones  (fig. 28) there is a
                              middle point, to form the future shaft;
                              and  one at  each extremity, to  form
                              the articular surface and  eminences.
                              That  in the shaft is  the first to appear,
                              and the others  succeed it at a variable
                              interval.   The central part is  termed
                              the diaphysis,  and for a  long period
                              after  birth there  remains a layer of
 Vertical section of the knee-joint of an in-
fant; showing the points of ossification in the
shaft and epiphysis of the femur and tibia,
and in the patella.  A few vascular canals
are also seen in the cartilage. Natural size.
—From the Museum of King's College. 
DEVELOPMENT OF BONE.
119
Fie. 29.
Fig. 30.
unossified cartilage between this and the epiphyses, as the extremities
are then styled.  Processes  of  bone have  usually their own  centres of
ossification, and  are  termed epiphyses
until they are finally joined  to the main
part, after which  they receive the name
of apophyses.
   Ossification generally extends in the
direction  that  the future lamina?  and
Haversian rods  are  to assume,  and
which corresponds in a great  measure
to that in which  it is designed  that the
chief strength of the structure  may lie.
Thus,  in  the  bones  composing  the
Vault Of the Cranium, there is always   Scapula of a foetus at the seventh month;
        ...  j    ,.   .    .,      .     J   showing the progress of ossification. Natu-
a Very decided radiation from the mOSt  ralsize.  The light pans are epiphyses as
prominent part  of  the  convexity of  l&g&£Z»toZ!m *°  *Lu"ma *
each.  In the scapula  this  direction is
indicated by the lines of sha-
ding represented  in figure
29.   The outline marks the
limits of the temporary car-
tilage,  in  which  no  other
points  of bone have yet ap-
peared.
   Th? minute history of the
process  by which temporary
cartilage  is converted  into
bone, is of extreme interest.
Very good descriptions of it
have been given by Sharpey,
Miescher, and  others ; from
which, however,  it will be
seen by  the  following  ac-
count that we differ in some
important particulars.
   The   nucleated  cells  of
temporary cartilage are small,
and   pretty  uniformly  scat-
tered through  a sparing,  ho-
mogeneous intercellular sub-

 Fig. 30.  Vertical section of cartilage
near the surface of ossification :— 1. Ordi-
nary appearance of the  temporary carti-
lage.  1'. 1'ortion of the same more highly
magnified.  2. The cells  beginning to as-
sume  the linear direction.  2'.  Portion
more magnified. Opposite 3, the ossifica-
tion is extending in the intercellular
spaces, and the rows of cells are seen
resting in the cavities  so formed;  the
nuclei being more separated than above,
3'. Portion of the same more highly mag-
nified.—From a pew-born rabbit which had
been preserved in spirit.
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120
ORGANS OF LOCOMOTION.
Fig. 31.
stance.   The nuclei are granular, and large compared with the cells,
which are  distinguished from the surrounding  substance principally
by their transparency around each nucleus (fig. 30, 1.  1')-
  In the vicinity of the point of ossification,  (for example, in one of
the long bones,) a singular change is observed.   The cells are seen
to be gradually arranging themselves in linear series, wThich run down,
as it were, towards the  ossifying surface.  The appearance they pre-
sent on  a  vertical section is represented in  fig. 30.   At  first their
ao-oregation is irregular, and the series small  (2. 2');  but, nearer to
the surface of ossification, they form rows of twenty or thirty.   These
rows are slightly undulated, and are  separated from  one  another by
the intercellular substance.   The  cells composing them are closely
applied to  one  another, and compressed,  so  that  even their nuclei
seem  in many instances to  touch  :  the  nuclei  themselves are also
flattened, and expanded laterally.
  The lowest rows dip  into, and rest in deep narrow  cups of  bone,
                    formed by the  osseous transformation of the in-
                    tercellular substance between  the  rows.   These
                    cups are seen by a vertical section  in fig. 30, 3.
                    3', and  by  a transverse section  on the  level of
                    the ossifying surface  in fig. 31.   As  ossification
                    advances between the rows, these cups are of
                    course converted into closed areola? of bone, the
                    walls  of which are lamelliform,  and  at first  ex-
                    tremely  thin.
                      Immediately upon  the ossifying surface,  the
                    nuclei, which  were  before  closely compressed,
                    separate  considerably from  one  another by  the
                    increase of material within the cells.   The nuclei
                    likewise  often  enlarge and become more trans-
                    parent;  a condition first pointed out to  us by
                    Mr. Tomes, but not present in  fig.  31, which
                    was taken from a preparation  that had been  im-
                    mersed in spirit.   The changes now enumerated
                    may be  conveniently considered to constitute the
                   first stage of the process, which extends only to
the ossification of the intercellular substance.   In this stage there are
no  blood-vessels directly concerned.
   The areola? or minute cancelli, when first formed, contain  only the
rows of cells which they have enclosed.   It is remarkable, that, when
the cartilage is torn from  the bone, it usually carries with it one or
two layers of these cancelli, or a little more  than is represented in
fig. 30.   If the specimen be examined deeper in the  bone, even  at a
depth of yVor \ of an  inch, other  appearances  are met with.   The
lamella?  of bone enclosing the cancelli are no longer simply homoge-
neous  or finely granular in texture,  but have acquired  more'the aspect
of  perfect bone.   They are also  thicker, and include  in  their sub-
stance elongated oval  spaces,  which, excepting that they are  of a
roughly  granular nature, exactly resemble the lacuna of bone already
described.   They are evidently the nuclei of the cells of the tempo-
 Horizontal section at the
ossifying surface of a fcetal
bone ; showing the cups of
bone cut across, with  the
granular nuclei of the in-
cluded cells, a New bone.
6. Nucleus.—From the rab-
bit. Taken from a drawing
of Mr. Tomes. 
OSSIFICATION.
121
Fig. 32.
 Vertical section from the same specimen as fig. 30, but
deeper in the bone ; showing the cancelli with blastema and a
few cartilage-cells, and also -the osseous  laminae containing
lacunae, similar to the nuclei of the cells:—rf. Seen by a low
power, rf'. Portion of d more highly magnified, f. Blastema
around the cartilage-cells,  e. Cartilage-cell  apposed to the
wall, and  its nucleus ready to become similar to the other
lacunas, as g.
Fie. 33.
 rary cartilage,  they are  scattered at pretty uniform  distances  apart,
 and they all follow the direction of the lamella? to which they belong
 (fig. 32,d.g).  The cur-
 vilinear outline  of  their
 now  ossified  cells   can
 often   be   partially   dis-
 cerned (fig. 32, e).
   Within   the cancelli,
 only a few cells  can  be
 detected,   these  cavities
 being chiefly occupied by
 a quantity of new  sub-
 stance, consisting of gra-
 nules, and resembling a
 formative   blastema  or
 basis, like  that  out  of
 which all the tissues are
 evolved  (fig. 32, f and
 fig.  33,  i).   The  cells
 that are met with are in  apposition with the wall; and sometimes (as
 in fig. 32, e) one  of them seems half ossified, and its nucleus about to
 become a  lacuna.   The  nuclei of these cells
 have  now  always the same  direction  as the
 neighbouring lacuna?.
   In fig. 33, taken from  a little deeper in the
 bone, we have portions of three cancelli, i. i. i.,
 together  with  the osseous material, now of
 considerable  thickness,  that  intervenes  be-
 tween them.  In  the centre of this last is seen
 a lamella, /, of a  peculiar kind, containing no
 lacuna?, and quite  distinct from the  layers, h.
 h., between which it lies.  These  consist of
 nucleated   cells, corresponding in  size  with
 those  of the temporary cartilage, and having
 their nuclei disposed  vertically,  and  of the
 same  shape and dimensions as the lacuna? of
 bone.   They are  still granular, however, and
 no pores can  be   seen  emerging from  them.
 The cells are united  together, and the lines of
 their  junction have for the most part  disap-
 peared.   The curvilinear border of  each  can
be still seen,.however, at its  union with the
 central lamina, I.   In the cancelli, i.  i. %., the
 granular blastema  exists in great abundance.
   It hence appears, that, after the ossification
 of the  intercellular substance,  the rows  of car-
tilage  cells arrange  themselves on the inner
 surface  of  the  newly  formed cancelli,  and
become ossified,  with the exception of their
nuclei, wdiich remain granular,  and  subse-
      9
  Another  portion  from  the
same specimen:—i Li. Portion
of three cancelli, containing
blastema, and having between
them the wall of bone.  Tin
interior of this wall, I, is finely
granular, and contains no lacu-
nre, being the lamina first form-
ed between the rows of cells in
the cartilage.  Coating this on
both sides is a layer ot bone in
which the form of the cartilage-
cells is still visible, as well as
their nuclei formingthe lacuna.-.
On the wall of the cancellus on
the right are seen two nuclei,
which appear to be  forming
there. This last is an  appear-
ance often seen. 
122
ORGANS OF LOCOMOTION.
quently form the lacuna? of bone ;  and that a  new  substance, or
blastema, appears within the  cancelli, from which, probably, vessels
are developed, and the future steps in the  growth of the bone pro-
ceed.
   The cancelli when  first formed are  closed cavities.   At a subse-
quent period they appear  to communicate,  and thus  to  form the
cancelli and Haversian  canals  of perfect bone; a  complete net-
work of blood-vessels becoming developed within them at the same
time.
   The subsequent progress of ossification seems to consist essentially
of a slow repetition, on the entire vascular surface  of  the  bone, of
that process which has been now briefly described.  It is probable
that new cartilage-cells are developed on  that surface, and become
ossified in successive layers, their nuclei remaining to form the lacuna?,
the uniform dispersion of which through bone is thus explained. The
cause of the lamination of bone parallel to its vascular surface, is also
thus illustrated.
   The first appearance of pores is in the form of  irregularities in the
margin of the lacunae.  These increase with the consolidation of the
tissue, and  are converted into branching tubules which communicate
with those  adjacent.  These pores must consequently be formed in
the ossified substance  of the cartilage-cells.   In  our account of the
lacuna?  of perfect bone  it was  mentioned, that, for the most part,
those of contiguous Haversian  systems do not communicate  across
the narrow interval that  separates the Haversian  rods ;  this interval
having in  fact no pores.   It results from what has just been said of
the mode of deposition of new layers, that the primary osseous net-
work, formed in  the  intercellular  substance of the  temporary carti-
lage, must come to constitute the substance intervening between the
Haversian rods, the non-porosity of  which is thus  satisfactorily ac-
counted for, as  well as the facility with  which the rods themselves
may be made to separate from one another.  As for the  lacunae, their
originally granular interior seems  to be gradually  removed, so that
they become vacuities adapted for the conveyance  of the  nutritious
fluids through the compact material of  the perfect bone.
   Growth of Bone.—But it must not be imagined,  that, when bone
is once deposited in a  certain  form,  it thenceforward permanently
maintains its size and shape.  Though a lamella  be  completely ossi-
fied, its particles are in constant course of change, during which the
most important and  extensive alterations of size and figure take place
in a slow and gradual manner.  Thus the layers first  deposited on
the inner surface of the early cancelli are pushed out by the succeed-
ing ones, and also acquire a concomitant augmentation of mass ; and
as, in general terms, the number of  lacuna? in bone is  proportioned
to its amount, the early layers most  likely  increase by a growth and
ossification  of cells in their own substance, even for long after they
have been pushed away from the vascular surface, and supplanted by
the more recent ones.  Thus, though bone  grows  chiefly by layers
formed in succession  on its vascular surface, yet  it also grows in an
interstitial manner after being originally deposited.   It is in this way 
GROWTH OF BONE.
123
only that we can explain the great expansion which the primary inter-
cellular osseous network must undergo, to form that which intervenes
between the Haversian systems.
  Bone, when  first formed, then, is disposed as an  expanded surface,
variously and complexly involuted, and which soon becomes covered
with vessels.   This is the foundation for its subsequent  vascularity.
and is the source also  of that active power of internal growth, which
has been long  a theme of admiration with physiologists.
  But the expansion of bone  once deposited is  limited.   We before
observed that no part of the osseous tissue was at more than a certain
minute distance from  the vascular  surface ; and that, if it were  so,
its  nutrition  could  not be suitably carried on.   Now, if more than a
certain number of lamina? of new bone were laid down, the earlier
ones would be pushed too far from  the supply of  blood ;  and hence
the limitation we have spoken of.  But it is necessary for bone to
grow much more between the commencement of ossification  and  the
adult age than  this limitation appears to allow of;  and here we  come
upon an admirable provision to  meet this apparent difficulty.
  In the first  place, a most important process of growth is  continu-
ally going  on in the cartilage, especially near the  ossifying surface,
by  the multiplication of the cells; and, in the latter  situation, by  the
increase in their  dimensions, occasioning that separation  of their
nuclei, already described (p. 119, and fig.  30, 3).  In the long bones
this takes place chiefly in the longitudinal direction,  which is that in
which growth  is most  active; and it continues till adult age.  This
fact has  been  long ascertained, though its real purpose  appears to
have been  overlooked.  Hales and Hunter both inserted metallic sub-
stances  along the  shaft of a growing  bone, in a young  animal, at a
certain distance apart; and found after an interval of time, that  the
distance between  them  remained the same, or nearly so, while  the
extremities  of  the bone were  much further apart: thus proving that
the principal growth had taken place near  the extremities.
  Secondly, bones  increase in  dimensions by an  accession  of new
osseous substance on their exterior;  this new substance consisting  not
merely of new laminae, but of new systems  of laminae,  and of new-
involutions  of  the vascular surface to form  new Haversian canals, so
that the earlier systems  of lamina? are  covered  over by the  more
recent ones.   This has been best  proved by the experiments with
madder.
  It was ascertained  accidentally by Belchier  that  the  rubia tinc-
torum, or  madder, mixed with  the food of  pigs, imparted  its  red
colour to their bones; and this  circumstance has been  ingeniously
taken  advantage  of by several physiologists in the prosecution of
researches on  the  growth of bone.*   Duhamel, Hunter, and  many
  *  The colouring of bone  by madder results from an affinity of the colouring prin-
ciple for the phosphate of lime. This opinion was distinctly  broached  by Haller
(El. Phys. t. viii. p. 329), and it was subsequently proved by Rutherford, who showed
it experimentally. To an infusion of madder in distilled water add muriate of lime :
no  change takes  place. Then add phosphate of soda in solution.  By double elec-
tive affinity, phosphate of lime and muriate of soda are formed. The phosphate is
insoluble, and subsides in union with the colouring matter as a crimson lake.  When 
124
ORGANS OF LOCOMOTION.
others, have performed multiplied experiments of this kind.   In the
Museum of King's College are some good preparations of bones so
acted upon.
  It is  found that, in  very young animals, a  single  day suffices to
colour the entire skeleton, apparently in an uniform manner;  in these
there is no osseous material far from the vascular surface.   But, if we
make a  transverse  section of one of the  long bones so  treated, we
observe the deepest, or even the only colour, to be really on the  vascular
surface ; the Haversian canals are each encircled  by a crimson  ring.
This beautiful illustration is due, as far as we know, to Mr. Tomes,
who has long possessed some very elegant specimens prepared in this
way.
  In full-grown  animals the bones  are  very  slowly tinged,  because
the great mass of the bone is not  in contact with blood-vessels; each
Haversian system, for example, has only its small innermost lamella
in contact with them ; and, besides, the  osseous matter is altogether
more consolidated and less permeable by fluids  than at a very early
period of life.   In the bones of half-grown animals a part of the bone
is nearly in the  perfect condition, while  a part is new and easily
coloured.  Hence, it  is easy in them to distinguish the new from the
old by means  of madder.
  Now,  madder given to half-grown animals colours the long bones
most deeply in the interval between the shaft and extremities, and
on the surface of the  shaft.   When madder is given at intervals, the
tints in   the bone are  interrupted ; the layers  in course of formation
during its administration are coloured, while those formed during the
intervening periods are  colourless.   The long period during which
bones retain the  madder  tinge,  shows that the  colouring matter is not
readily resumed by the blood, from its combination with the phosphate
of lime  ; and  it  seems also to indicate a sluggishness of the nutrient
process  in bone.
  Perhaps few questions have  more divided the  minds of physiolo-
gists than that regarding the share  taken by  the  periosteum in the
growth  and regeneration of bone ; for these  last are essentially the
same process.   We now see that bone does not grow on its exterior
because the periosteum is there; and that the only part this membrane
takes in the deposit of new  bone is by the vascular  network  mingled
with its fibrous tissue, and which does not differ from that on other
portions of the osseous surface.
  The limited expansibility  of the bone already formed is the remote
cause to which the growth  by new  deposit on the  exterior  is to be
referred ; and, in this respect, the superficial growth is strictly analo-
gous to  the exogenous mode of growth in vegetable structures.
  A third mode in which increase  of size is provided for, appears
to be by the dilatation of the primary cancelli and  Haversian Canals
in the central  parts of the bone.   In  early life the cancelli are small,

madder is given as food, its colouring principle is absorbed, and circulates with the
blood; and it colours first that part of the  bone which is in  course of formation
from that fluid, or which  has been last formed, i. e. which is nearest the vascular
surface. 
REPARATION OF BONE.
125
and there  is  no medullary cavity.  Gradually the cancelli enlarge,
and those within the shaft blend more  and more with one another, by
the removal to a greater or less  extent of the intervening osseous
walls, until at length a medullary canal is formed, around which the
cancelli are very open, large and  irregular.  This augmentation of
the vascular cavities of bone is attended  with a development of adi-
pose vesicles and their capillaries in the new space, while the proper
vessels of the osseous tissue remain pretty much as before.  The fat
contained in the medullary canal gradually accumulates so much, that
a  special  artery becomes enlarged to supply it,  assuming the  very
inappropriate  title of "the nutrient artery of the bone."   Duhamel
placed a ring of  silver round a bone of a young pigeon, without in-
juring the periosteum.  After some time, during which the  bone had
increased in diameter,he found the ring in the medullary canal, which
had acquired a capacity equal to the previous diameter of the whole
shaft.
   This enlargement of the diameter of a long bone by the  dilatation
of its interior, is attended by two consequences, equally important.
The shell  of compact tissue is thus adapted to offer greater resistance
to injurious mechanical  forces, while the  disadvantage of a corre-
sponding increase of weight is obviated.
   Reparation of Bone.—The great importance of this subject to the
surgeon has led to many very interesting researches from the  time of
Duhamel to the present  day, and by these the several steps of the
process by which  new bone is deposited have  been ably elucidated in
all that  relates to their more obvious characters. When  a fracture
occurs, blood  is, of course, effused into the wound, both  from the
ruptured vessels of the bone itself, and from those of the surrounding
structures participating in the injury.   At  a short period subsequently,
a  semi-transparent lymph is found mingled with the   coagulum, and
covering  the  surfaces of the hard  and  soft parts  exposed.   This
lymph in  all probability  is the same  as  that by which the adhesive
process  in other wounds  is effected.   In  the second and third weeks
a gradual  condensation of this takes place, accompanied with an in-
terstitial change, converting it into a substance resembling temporary
cartilage.
   Ossification takes place throughout this  in a  nearly uniform manner,
until towards the  fourth or sixth week, the whole is transformed into
a spongy, but firm osseous mass, investing the exterior of the broken
extremities, and extending between them in  the  form of a case, by
which they are firmly held together.  If the medullary canal has been
broken  across, and the broken  ends evenly adjusted, there will be
likewise an interior stem  of new bone  connecting the  medullary canal
of the fragments in  the axis of the bone ; the  opposed surfaces of the
compact tissue being as yet ununited.   The callus, or new bone, thus
formed, was termed by Dupuytren provisional, as  it is gradually ab-
sorbed during the succeeding months, while the permanent callus is
being slowly deposited between the contiguous surfaces of  the com-
pact tissue.   It wrould  appear that new bone is formed more exube-
rantly in the situations of  the provisional callus because of their greater 
126                  ORGANS OF LOCOMOTION.
vascularity; just as we may suppose the function of ordinary nutrition
to be more active in  those parts, than  in the compact tissue of  the
bone.   The permanent callus has all the characters of true bone.
   When the reparative process  in bone is interfered with, either by
mal-apposition of the fragments, or by  constitutional fault, a spurious
union may occur by the medium of a ligamentous substance,  or even
a diarthrodial joint may be formed at the seat of fracture.   The ends
of the bones become altered in fown, and adapted to one another; a
kind of false  capsular ligament is  developed, and  sometimes even
an imperfect cartilage, and a  lining membrane furnishing a lubricating
fluid.

  The following works may be  consulted on Bone:—The systems of General Ana-
tomy already quoted (p. 95); Meckel, Anat. Generale Descript. et Patholog., torn. i.;
Dr. Bostock's Physiology, where will be found an excellent and learned summary of
the observations of preceding physiologists on the structure and growth of bone; Mr.
Paget's paper on the influence of Madder on the Bones of growing Animals, Lond.
Med. Gazette, vol. xxv; Deutsch, de penitiori Ossium structura observationes; 1834:
Miescher.de inflammatione Ossium eorumque anatomegenerali; 1836: Miiller's Phy-
siology by Baly, vol. i.  M. Flourens has lately published a handsome volume on the
growth of bone, illustrated with figures.
                         CHAPTER VI.

SYNOVIAL MEMBRANES.—SEROUS MEMBRANES.--VARIETIES OF JOINTS.—
                   MECHANISM OF THE SKELETON.

  The different forms  of bones, when united according  to  various
mechanical  contrivances, constitute  the skeleton.   The  framework
of the body, being thus formed of  several pieces jointed together, is
admirably arranged for extended, or for minute and nicely adjusted
motions, and for distributing concussions over a large surface.  The
interposition of discs, or laminae, of elastic cartilage, or  fibro-carti-
lage,  between  some bones, contributes  to the latter object, by inter-
rupting  the  medium through  which the shock  would be conducted,
as well  as by  the elasticity of the intervening substances;  and, at
the same time, these discs,  by their intimate adhesion to the opposed
osseous  surfaces, serve as  powerful bonds of union between them.
Joints of this  kind  {synarthrodia!) enjoy a  very  limited  degree of
motion, which is entirely due to the  yielding  and  elastic nature of
the interposed  material.   When a  greater  range  of motion is  re-
quired than can be obtained in this way, the  surfaces of the  osseous
segments are  constructed  so  as  to glide the  one  upon  the  other in
certain directions, which are determined by the form of the articular
surfaces, and by the positions at which the connecting ligaments  are
placed.   Here the bond  of union consists of the ligaments  and  the
surrounding muscles;  the osseous segments are not, as in  the former
instance, continuous with each other through the interposed texture, 
SYNOVIAL MEMBRANES.—BURSiE.
127
but are separated by a space which is called the cavity of the joint.
Each osseous surface is encrusted by a layer of articular cartilage
adapted to its form, and  the cavity of the joint is lined  by a delicate
membrane which, secretes  a  peculiar viscid matter, synovia, admi-
rably suited to lubricate the  surface.  This  membrane is  termed
synovial, and is constantly present in the diarthrodial joints.
   The  articular  synovial membrane forms a  closed  bag, placed be-
tween the articular surfaces of  the bones.  Its free surface is smooth
and moist;  its attached surface adheres by very fine  areolar tissue  to
the  ligaments of  the  joint, and to the cartilages encrusting the ex-
tremities of the bones. From the ligaments it may be readily detached,
and traced to the edge of the  cartilage; to this it is very intimately
adherent for some little distance, beyond which it cannot be followed
where the cartilage has been exposed to pressure during the motions
of the joint.  In the foetus it is continued over the whole cartilage
(p. 97).
   In some of the more complex joints the synovial  membrane forms
folds, which project more or less into the articular cavities, and contain
fat, which Clopton Havers and  other anatomists erroneously imagined
to perform a glandular office, and to secrete  the synovia.   The knee
affords some remarkable  examples of  these folds, in what are known
as the alar ligaments.
   A great  number  of blood-vessels  are distributed in the areolar
tissue upon the attached surface of the synovial membrane.   In  in-
flammation, the membrane  acquires  a red  hue by  the repletion  of
these  vessels, and in  a  minute injection also it becomes coloured.
Excepting in very rare  cases,  the  vessels cannot be traced  beyond
the  edge of the  cartilage, where they form a series  of loops.  (See
p. 99—100).
   Bursa.—A very simple  form of synovial  membrane is employed
to  facilitate the gliding  of a tendon,  or  of the  integument, over  an
osseous projection.   It consists of  a  bag, generally  closed at every
point, connected  by areolar tissue  with  the  neighbouring parts, and
secreting into its interior a fluid, which lubricates its  free surface.
Sometimes, when one of these bursa? exists  in the neighbourhood of
a  large joint, it communicates freely with  the cavity of its synovial
membrane,  as in  the bursa behind the rectus femoris above the knee-
joint, and that near the hip-joint behind the tendon of the psoas and
iliacus muscles.   These synovial  sacs are found  in great  numbers
throughout  the body  : some are superficial,  or  subcutaneous, such  as
that between the  skin and the patella, or that over the great trochan-
ter of the femur,  or  that over the olecranon  : the deep-seated bursa?,
however, constitute the largest proportion of them ; these are almost
always connected with tendons, and interposed between  them and the
bones over which they play.   On  opening a bursa,  we often find  its
cavity traversed by bands which are either congenital  and approaching
to the cellular or  areolar disposition, or, as seems not unlikely, of the
nature of adhesions, and consequently a morbid production tending
to the obliteration of its  cavity.
   Synovial  sheaths.—These  are  synovial  bags prolonged  into the 
128
ORGANS OF LOCOMOTION.
form of sheaths, and surrounding long tendons, such as those of  the
flexor or extensor muscles of the fingers and toes, as they lie in their
osseo-fibrous sheaths in the hand or foot.   One layer of the synovial
sheath adheres to the wall of the osseo-fibrous canal; the other, to the
contained tendon ; and, the free surface being lubricated by synovia,
the tendon  plays freely within  the  canal.  In  deep-seated whitlow,
when the inflammation extends to one of these synovial sheaths, and
gives rise to the formation of adhesions within its cavity, the motion
of the tendon within is completely destroyed, and a stiff finger is the
result.  Similar sheaths on a larger  scale envelop the tendons which
pass beneath the annular ligaments of the wrist and ankle.
   Synovia.—The synovial membranes, in  health, contain  only suffi-
cient fluid to keep their free  surfaces moist.  It is, therefore, diffi-
cult to collect  the synovia in  sufficient quantity for  examination.
It is a transparent, yellowish-white fluid, viscid like  the white of an
egg, whence its name {aw, cum ; <*ov, ovum).  Lassaigne and Boissel,
who have published an analysis of human synovia, state that it does
not coagulate spontaneously ;  that it is an alkaline fluid, containing
albumen and salts, such as are found in the serum of the blood : and
M. L'Heritier has lately analyzed two specimens of this fluid, and
completely confirmed the statement of those chemists.*
   It is plain, from the description  above given, that synovial mem-
branes contribute to the locomotive function by lubricating the articu-
lar surfaces, so  that they may glide smoothly on one another with  the
least possible friction, and also by facilitating the play of some tendons
over prominent surfaces, and of others within sheaths.
   Serous  membranes.—The  movements  of the viscera  within  the
great cavities of the trunk are provided for by an arrangement similar
to that described in the joints.   Between  the wall of the cavity and
the surface  of  the contained viscus (the  thorax  and the  lungs, for
example,) a closed sac is placed, one layer of which is parietal, and
the other visceral.   These are respectively attached to the wall of the
cavity and to the surface of the viscus by fine areolar tissue ; and their
continuity is shown at  certain reflections, where the  one passes  into
the other.   The free  surface, as in the synovial membranes, is con-
tinually moistened by the proper secretion, which, containing a larger
proportion  of water  than synovia  does,  resembles serum of blood.
The serous membranes are, the  arachnoid, in the head and spine;  the
pleura and pericardium, in the thorax; the pericardium, in the abdo-
men ; and the tunica vaginalis testis, in the scrotum.  These are all
closed at every  point;  so  that their secretion, if morbidly increased,
is retained within the cavity, and can only be removed by absorption,
or by an opening through the  membrane.  In the healthy state,  the
surfaces are only moistened;  and, when more fluid exists, it  is  the
product of disease, or of post-mortem change.   If  the surfaces be
dry, or a viscid adherent matter be effused upon them, the move-
ments of the contained organ become impeded, and are accompanied
by a peculiar sound of friction, and a vibration sensible to the hand;
* Berzelius, Chemie Organ, t. vii. 
SEROUS MEMBRANES.
129
both of  which  are  well known to physicians in the pericardium,
pleura, and peritoneum, and may frequently be noticed by the patients
themselves.
  The peritoneum of the  female  affords a remarkable  exception to
the closed character  of serous sacs.   At two points this membrane is
open, where it communicates wTith the canal of each Fallopian tube
at its dilated extremity.
   The  blood-vessels  of serous membranes are distributed in con-
siderable numbers in the areolar tissue which is connected with their
attached surface.  We  infer that  nerves exist freely in the  same
tissue, from the intense pain which accompanies inflammation of these
membranes.   There is good reason to believe that lymphatics also are
freely distributed in  their areolar tissue.
   The serous membranes connect the viscera contained in the cavities
to which they respectively belong, by the folds they form as they pass
from each viscus to the wall of the cavity.  As the viscera  in the
abdomen are so many, and the folds proportionately numerous, the
peritoneum is  more  complicated in its disposition  than  any other
serous membrane; and it is part of  the  study of the descriptive ana-
tomist to show, that the  remarkable  complication of folds which this
membrane exhibits is not inconsistent with its adherence to the chief
morphological character of serous membranes.
   Microscopic  characters of synovial and serous membranes.—These
membranes appear to be essentially alike in their minute structure.
On their free surface is  a single layer of
epithelium, the particles of which are poly-
gonal in shape, and of transparent texture.
A small fragment  of this pavement, from
the peritoneum of the rabbit, is represented
in fig. 34.  This was discovered by Henle.
We have  found this epithelium  to rest
immediately  on a continuous  transparent
basement membrane  of excessive  tenuity,
apparently identical  with that which sup-
ports the epithelium of mucous membranes.
Beneath this is a lamina, of areolar tissue,
which constitutes the chief thickness  of the
membrane, and  confers on it  its strength
and  elasticity.   This areolar tissue is tra-
versed by a network  of  capillary  vessels,
the  meshes  of  which  are large  and  of
rather  unequal  size, and  by  lymphatics
and  nervous  filaments in varying number.
It is of close texture, and continuous with
that laxer variety by which the membrane is attached to the parts  it
lines.
   The  most favourable  position for examining the areolar tissue of
serous membrane, is the transparent part of the mesentery, or of any
of the duplicatures of the  peritoneum in small animals.
  Here we observe the yellow fibrous element assuming a  very beau-
Fig. 34.
 Epithelium of serous membrane:—
At o, an accidental fold is represented,
the two dark edges of which exhibit
the thickness of the particles, and of
their nuclei, b. One of the oval nuclei.
c Line of junction between two pani-
cles.—Magnified 300 diameters. 
130
ORGANS OF LOCOMOTION.
tiful arrangement (fig. 35).  Its filaments  interlace and  inosculate
chiefly in a plane beneath the basement membrane, in such a manner
as to confer equal elasticity in every direction.  The intermediate
                                   space is occupied by the wdiite
              Fig. 35.               fibrous  element,  disposed  in
                                   wavy bands, variously intersect-
                                   ing, and which become straight
                                   only when the elastic threads are
                                   stretched.
                                     Physical and vital  properties.
                                   —These are precisely those of
                                   areolar  tissue : the elasticity of
                                   the  serous membranes is very
                                   considerable, owing to the ad-
                                   mixture  of the  yellow  fibrous
                                   element in the layer which forms
                                   the chief substance of the mem-
                                   brane.   These  tissues are en-
                                   tirely devoid of vital contract-
                                   ility and their sensibility is low,
  Yellow fibrous element of the areolar tissue of se- except  in  a State  of aCUte in-
rous membrane.  From the mesentery of the Rabbit, fl„mmat;ftn
treated with acetic acid—Magnified 300 diameters.   UdllHUdllOIl.
                                     These membranes  exhibit, in
their inflamed state, a remarkable tendency to  throw out lymph on
their interior, so as  to  cause  adhesion  of  their opposed surfaces.
Hence a frequent result of inflammation  of a serous membrane is the
obliteration,  to a greater or less extent, of its cavity.    Synovial mem-
branes  are not  so prone  to the adhesive inflammation as the  serous
are, which  seems  more to be  accounted for by the  nature of their
secretion, than by any difference of their structure.   The proneness of
these membranes to the effusion of coagulable lymph seems to be due
to the extreme tenuity of the layer of epithelium wThich separates the
nutrient blood-vessels from the cavity of the serous  membrane.  The
lymph  effused becomes  gradually converted  into areolar tissue and
vessels usually constituting what are termed adhesions, but some-
times forming merely a thickened condition of the membrane.
   Of the joints.—A joint, or  articulation, may be defined to be the
union of any two segments of  an animal body, through the interven-
tion of a structure or structures different from both.
   The  most perfect and elaborate forms  of the articulations are those
which  are  seen in animals that possess a  fully developed  internal
skeleton, and in none may they be studied with more  advantage than
in man.  In the human subject, and in the vertebrated animals gene-
rally, we have indeed, particular occasion to ddmire the articulations
as"mirabiles commissuras, et ad stabilitatem aptas et ad artus fini-
 endos accommodatas, et ad motum, et ad oranem corporis actionem."
   The textures which form the joints, are bone, cartilage, fibro-carti-
 lage, ligaments, synovial membrane.   Bone constitutes  the funda-
 mental part  of all joints; ligament  variously modified is employed in
 
THE JOINTS.
131
all as a bond of union ;  but the three remaining textures are present
chiefly in those joints which enjoy a free gliding motion.
  In  addition  to  the  structures  already named  as  entering intrin-
sically into the formation of joints, we find that the tendons and mus-
cles, which lie in the immediate vicinity of or which surround the
joints, contribute  much to their  strength and security.   In joints  of
the hinge kind we generally see the anterior and posterior  parts pro-
tected more or less by the tendons of muscles, and even by muscles
themselves passing from one segment of a limb to another; and here
it frequently happens that  the  tendon is bound  down on the bones
which  form the  member, by a fibrous expansion of great strength,
lined by a synovial membrane of  the same characters as the articular,
but adapted in its form to the osseo-fibrous canal in which the tendon
is placed, e. g.,  the tendons  of the  fingers.   The  protection and
strength afforded  by muscles is  particularly evinced in the case of the
shoulder-joint, where the capsular ligament is  closely embraced by
four muscles, whose tendons become identified with the fibrous cap-
sule as they go to be inserted into the bone.  A muscular  capsule is
thus provided for  the joint, by  which the bones are maintained  much
more firmly and powerfully in  apposition than they would be if kept
together by an uncontractile ligamentous  capsule alone ; hence the
elongation of the  arm that occurs as a consequence of paralysis, and
hence also the greater liability to luxation  which exists  in a debili-
tated state of the  system.  Articular or capsular muscles, thus placed,
have also the effect, as it is said, of preventing the pinching of the
capsule or synovial membrane between the  articular extremities  of
the bones in the different motions of the joint.
  Atmospheric pressure, exerting as it does a force of nearly fifteen
pounds on  the square  inch, is a powerful  agent in  maintaining the
contact of  articular surfaces.   This is well  illustrated by the diffi-
culty of separating  the  surfaces composing the hip and shoulder
joints, when  the surrounding ligaments are air-tight;  while, on the
other hand, these  surfaces may be separated by  the  mere weight  of
either bone, if one of these joints be  suspended in the exhausted
receiver of an air-pump.  In  exhibiting this experiment, we find
the shoulder joint shows the   effects of atmospheric pressure more
strikingly than  the hip, for its  capsule being loose,  and the  osseous
cavity for the reception of the  head of the humerus small, the pres-
sure of the  atmosphere pushes  in the  capsule so that it fits closely
to the head of  the bone.   When this pressure has been  removed by
exhausting the receiver, the head of the humerus falls rapidly from
the socket, and the ligament becomes stretched by the weight of the
bone.
  The  joints are  supplied copiously with  blood, and  are remark-
able for the arterial anastomoses which take place about  them.   The
best examples  of these inosculations are met with  around the large
joints of the extremities.  The  parts supplied  with blood  are the
synovial membranes, the  ligaments, the  fat, and the  extremities  of
the  bones; but the cartilages certainly do not contain blood-vessels.
  Of the forms and  classification of the joints.—It is  not difficult, 
132
ORGANS OF LOCOMOTION.
by passing in  review the various motions which take place between
any two segments  of a limb,  to  form an  idea, a priori, as to the
kinds and shapes of the articulations by which the segments will
be united ; it  is only necessary not to lose  sight of the fact, that in
the construction of a joint  regard is had not to its  mobility alone,
but to its security,  its durability, and the safety of  the  neighbouring
parts.   We may expect to find joints varying in the degree of motion,
from  the  slightest perceptible,  to  the  freest that is compatible with
the maintenance  of the  segments in their proper relation with  each
other; and also in  extent of motion, from that which is so  slight as
to admit of almost no appreciable change in the position of the parts,
to that which  allows of the most ample variety of movement between
the segments,  consistent with the integrity of the articulation.
   It  will appear, then, that the most simple kind  of  articulation is
that by which two  parts are so united as  that only the slightest ap-
preciable degree of motion shall exist between them.   This  consti-
tutes  the first great division of joints—the Synarthrosis, where the
parts  are continuous, i. e., not separated  from each  other by an inter-
vening synovial cavity.  Some anatomists  consider all synarthrodia!
joints to be immovable ; which, although  not far from the truth, cannot
be  said to be  strictly accurate.  Had immobility been  the  object to
be attained, that might have  been more  effectually  accomplished
by the fusion of the extremities of the segments together, as in anchy-
losis.
   In  the second class of joints, motion  is  enjoyed freely and fully:
this class is designated by the term Diarthrosis:  the  segments are
interrupted completely in their continuity  : the extremities of the bones
can only be said to  be contiguous.
   Synarthrosis.—The general characters of the articulations belong-
ing to  this class are, 1, that they are very limited in  their motion,
insomuch as to be  considered by some as  immovable;  2, that their
surfaces are continuous, i.  e., without the  intervention of a synovial
cavity,  but writh that of some  structure different  from bone.  The
following varieties  may be  noticed among synarthrodial  articulations.
   a.  Suture.—When the margins of two  bones exhibit a series of
processes and indentations (dovetailing)   which  are received  and
receive reciprocally, with a very thin cartilaginous lamina interposed,
this is the ordinary  kind of  suture, sutura vera, of  which three kinds
are distinguished :  sutura dentata, where the processes are long and
dentiform, as  in  the  interparietal suture  of  the human  skull; sutura
serrata, when the indentations  and processes  are small and fine like
the teeth of a saw, as in the suture between the two portions of the
frontal bone ;  sutura limbosa, when  there is along  with the dentated
margins a degree of beveling of one, so that one  bone rests on the
other, as in the occipito-parietal suture.
   When the  two  bones are  in juxtaposition  by plane but rough
surfaces, the articulation is  likewise said to be by  suture, and this is
the false suture, sutura notha, of which  there are two kinds;  sutura
squamosa, where the beveled  edge  of one  bone  overlaps and rests
upon the other, as in  the temporo-parietal suture,  and harmonia 
THE JOINTS.
133
(a£u,  adapto), where there is simple apposition:  this  last kind  of
articulation  is  met with, as  Bichat observes, wherever the mecha-
nism  of the parts is alone sufficient to maintain them in  their proper
situation,  as may be seen in  the  union of most  of the bones of the
face.
  The sutures have a considerable tendency to become obliterated by
age, the  intervening cartilage becoming ossified;  it  rarely happens
that the sutures are all manifest  in a human skull past  fifty years  of
age, and  sometimes the  obliteration takes place at  a much earlier
period.   The frontal suture is by no means permanent; it is not often
found at puberty.   In birds and fishes this tendency to  the obliteration
of the sutures is particularly manifest.
  b. Schindylesis {ax^vxtjaii,  fiissio; c^w, diffndo).—This  form  of
articulation is where a, thin plate  of bone is received into a space  or
cleft formed by  the  separation of two lamina?  of another, as is seen
in the insertion  of the azygos process of the  sphenoid bone into the
fissure on the superior margin of  the vomer;  and in  the articulation
of the lachrymal bone  with the  ascending process of  the  superior
maxillary.
  c.  Gomphosis (yo^oj,  (clavus.   Clavatio, conclavatio).   When  a
bone is inserted into a  cavity in  another, as a nail is driven into a
board, or as a tree  is inserted into the earth by its roots, the articula-
tion is by gomphosis.  The only  example we have of it in the human
subject or in quadrupeds is  in  the  insertion of the  teeth  into the
alveoli.
  d. Amphiarthrosis.—This is a form of articulation where two plane,
or  mutually adapted surfaces  are held together by a cartilaginous  or
fibro-cartilaginous  lamina of considerable thickness, as well as by
external ligaments.   In virtue of the elasticity of the  interposed car-
tilaginous or fibro-cartilaginous lamina, the amphiarthrosis possesses
a manifest, although certainly a  very limited degree  of motion, and
hence most systematic  writers class  it with the diarthrodial articu-
lations.   But  it appears much more consistent to place  it among the
synarthrodia! joints, for, 1, its anatomical  characters  agree precisely
with those of synarthrosis ; 2, the surfaces in amphiarthrosis being
continuous, it would make an exception  in  diarthrosis were we  to
place it  there ;  and, 3, its degree of motion is  greater  than that  of
suture, only because of the greater development of the interosseous
substance.
  The examples of this form of joint  in the human  body are the
articulation between the bodies of the vertebra?, that between the two
ossa pubis at what is called the symphysis, and that between the  ilium
and sacrum.   Like the sutures, the amphiarthroses are liable to be-
come obliterated in old age,  by  the ossification  of the  interosseous
lamina.   This is not uncommon  in the interpubic, and occurs  now
and then  in the  intervertebral and sacro-iliac joints.
  Diarthrosis.—Mobility is the  distinguishing characteristic of this
class  of joints;  the  articular surfaces are contiguous, each covered  by
a lamina  of  cartilage {diarthrodial cartilage),  having  a  synovial sac
interposed, and  in  some  cases two, separated by a meniscus.   The 
134
ORGANS OF LOCOMOTION.
integrity of the articulation is maintained by ligaments which pass
from one bone to the other.   Their mechanism is much more com-
plicated than that of synarthrodial joints, being intended not only for
security, but also to give a certain direction to the motions of which
they are the centre.
  Before proceeding to the enumeration of the varieties of joints that
come under this head, it will not  be amiss to describe briefly the
various motions which may take place between  any two segments of
a limb, and which it is the object of these joints to admit of.  It is
obvious that the  most simple kind of motion which can exist between
two plane or contiguous surfaces, is that of gliding: one surface glides
over the other, limited by the ligaments which extend between  the
bones.  This motion, however, is not confined to plane surfaces; it
may exist evidently between contiguous surfaces, whatever their form.
When two segments of a limb, placed in a direct line, or nearly so,
can be brought to form an angle  with each other, the motion is that
of flexion, the restoration to the direct line is extension.  These two
motions belong to what Bichat calls limited opposition; the flexion and
extension of  the fore-arm on the arm  illustrate it.   Sometimes a
motion of this kind takes place in  four directions, indicated by two
lines which cut at right angles.   This is best understood by a refer-
ence to the motions which take place  at the hip-joint: there it will be
seen that the thigh-bone may be brought forward so  as to form an
angle with the trunk, flexion—or it may be restored, extension; it may
be separated from the middle line of the body so as to form an angle
with the lateral surface of the  trunk, abduction—or it may be  restored
and made to approximate the middle line,  adduction.  It is evident
that  a joint, which is susceptible  of these  four  motions, may also
move in  the intermediate directions.   When these motions  are per-
formed rapidly, one after the other, one continuous  motion  appears
in which the distal  extremity of the  bone  describes a circle indi-
cating the  base of a cone whose  apex  is  the articular  extremity
moving in the joint;  this motion is  called circumduction.
  Rotation is simply the revolving of a bone around its axis.   It is
important to bear this definition in  mind: through losing sight of it
many anatomists have attributed rotation to a joint which really does
not possess it.
  The varieties of the diarthrodial  joint are  as follows:
  a. Arthrodia.—In  this  species the  surfaces  are plane,  or one is
slightly concave, and the other slightly convex : the motion is that
of gliding, limited in extent  and direction only by the ligaments of
the joint, or by some  process or processes connected with the bones.
The examples in  men  are, the articular processes  of the vertebra?,
the  radio-carpal,  carpal,  carpo-raetacarpal, inferior radio-ulnar, supe-
rior tibio-fibular, tarsal and tarso-metatarsal, temporo-maxillary, acro-
mioclavicular, and sterno-clavicular joints.  This last articulation and
the  wrist-joint possess a  greater latitude of  motion than the others;
the  former, in consequence of the shape of its articular surfaces; each
surface is convex in one diameter and concave in the other, so that the
gliding that takes place in this joint is in the direction of the long and 
THE JOINTS.
135
short  diameters, which intersect each  other  at right angles.   It is
capable, therefore, of vague opposition  in  those lines, but certainly
not in the intermediate directions, the  nature of the surfaces being
calculated to prevent this.  The wrist owes its mobility to the laxity
of its ligaments, which permit it to move as well in its transverse as
in its antero-posterior diameters, as  also in the intermediate direc-
tions; it consequently admits of vague opposition and circumduction.
The articulation of the metacarpal bone  of the thumb with the trape-
zium is also an arthrodia very similar to the sterno-clavicular, but with
a greater degree of motion.   Arthrodial joints are generally provided
with ligaments, placed at the extremities of the lines in the direction
of which the gliding motion takes place.
   b. Enarthrosis.—This is a highly developed arthrodia. The convex
surface  assumes a globular shape, and the concavity is so much deep-
ened  as to be  cup-like ; hence  the appellation ball and socket.  The
ball is kept in apposition  with the socket by means of a capsular liga-
ment, wrhich is sometimes strengthened by accessory fibres at  certain
parts that are likely to be much  pressed  upon.   The best example of
enarthrosis is the hip-joint, and  next to it the shoulder: in  the latter
the cavity is but imperfectly developed.   All the  quadrupeds have
their shoulder and  hip joints on this construction, and the same com-
mon plan is observed  in  the vertebrata  generally whose  extremities
are developed.  In birds and reptiles the bodies of the vertebrae are
articulated by enarthrosis.
   This species of joint is capable of motion of all kinds, opposition and
circumduction being the most perfect, but  rotation limited.  Indeed,
what  is  called rotation at the hip-joint, is effected by a gliding of the
head  of the femur from  before  backwards, and vice  versa,  in the
acetabulum ; it is not a rotation of the head  and neck, but of the shaft,
of the femur.
   c. Ginglymus (ytyyviyioj,  cardo).—The  articular  surfaces  in  the
hinge-joint are marked with elevations and depressions which exactly
fit into  each other, so as  to restrict motion in all but one direction.
They are always provided with strong lateral ligaments,  which  are the
chief bonds of union of the articular surfaces.
   The elbow and ankle joints in man are perfect ginglymi; the knee
also belongs to this class, but  is by no means a perfect specimen,
for, in a certain position of  the  bones of this joint, the  ligaments are
so relaxed as to allow a slight rotation to take place.  The phalangeal
articulations, both of  the  fingers and toes, are ginglymi.  This form
of joint is  most extensively employed among the lower animals.   In
quadrupeds, most of the joints  of  the  extremities come under this
head. In amphibia and reptiles, too, there are many examples of the
hinge-joint.  The bivalve shells of conchiferous mollusca are united
by a very perfect hinge, and a great number of the joints of Crustacea
and insects are of this form.
   The true ginglymus  is only susceptible of limited opposition : hence
the knee-joint  cannot be  regarded as a perfect  example ;  in fact, in
the perfect ginglymus there is every possible provision against lateral
motion. 
136
ORGANS OF LOCOMOTION.
  d. Diarthrosis rotatorius.—A pivot and a ring constitute the me-
chanism of this  form of joint.   The ring is generally formed partly
of bone and partly of ligament, and sometimes moves on  the pivot,
sometimes  the pivot moves in it.  The motion is evidently confined
to rotation, the axis of which is the axis of the pivot.
  In the human  subject the best example of this articulation is that
between the atlas and odontoid process of the axis  or vertebra den-
tata.  The ring  is formed by a portion of the anterior  arch  of  the
atlas, completed behind by a  transverse ligament.   Here the atlas
rotates round  the  odontoid process, which  is the axis of motion.
Another example is  the superior radio-ulnar articulation :  here one-
fourth of the ring is formed by bone, namely, the lesser sigmoid cavity
of the ulna, and the remaining three-fourths by the  round ligament
called the coronary ligament of the radius.  In this case there is rota-
tion as perfect as in that just mentioned; but the head of the radius
rolls in the ring, and the axis of motion is the axis of the head and
neck of the bone.   Some anatomists  consider this joint a species of
ginglymus, which they designate lateral.
  The terms  Symphysis,  Synchondrosis,  Synneurosis,  Syssarcosis,
Meningosis, have been employed by anatomists to  designate certain
kinds of articulation, chiefly in reference to the nature  of the con-
necting media.   Symphysis, although originally employed with great
extent of meaning,  seems to have  been in later days  applied  exclu-
sively to denote  the articulations of the pelvis, which we have classed
under Amphiarthrosis.  We pass over the other terras because they
ought to be discarded from use, as only tending to encumber a voca-
bulary already  too  much crowded  with difficult  and  unnecessary
terms.
  Mechanism of the skeleton.—We shall conclude  this chapter with
some remarks  upon  the mechanical disposition of  the various parts
of the skeleton,  and their adaptation to the purposes  they were des-
tined to fulfil.
  The skeleton  consists of the head, trunk, and extremities.
  The head is  composed  of  a cavity, surrounded by osseous walls
{cranium), destined to contain and protect  the  brain ;  and of an  ex-
panded portion  {the face),  with which some of the organs of the
senses are connected, and upon which the features are formed.   The
size of the cranium affords a good clue to determine the absolute size
of the brain ; and the proportion of the face to it, offers a not inexact
index of the relation which  the intellectual faculties  and the  animal
propensities bear to each other.*
  The spheroidal form  of the  cranium admirably adapts  it for pro-
tecting the organ which it contains  against external  violence.  The
arched form is  that which  possesses  most strength,  and  offers  the
greatest resistance.  When, says Dr. Arnott, we reflect on the strength
displayed by the arched film of an egg-shell, we need not wonder at
the severity of the blows which the cranium can withstand.  And he
adds, in  reference to the former, " what hard blows of the spoon or
  * See a good account of the comparative mensuration of the skull in Mr. Ward's
Outlines of Human Osteology. 
THE CRANIUM.—THE SPINE.
137
 knife are often required to penetrate this wonderful defence of a dor-
 mant life!"  And this form, which  gives so much strength  to the
 skull, favors the transmission of vibrations along its walls, and thus
 saves the  delicate viscus enclosed by them.  Thus blows  inflicted
 upon the cranium become diffused; and sometimes  the violence ap-
 plied directly to the vertex is spent  upon the base of the skull, and
 causes a fracture there.
   The compound structure of the cranial  bones is an important ele-
 ment in the architecture of the skull as a protecting case to the brain.
 Most  of these  bones  are  formed  of two tables: the  outer  one  is
 tough, strong, and fibrous; the internal table is dense and brittle, and
 hence called tabula vitrea; and there is interposed between them a
 spongy texture, the diploe, in which blood-vessels are freely distributed
 (fig. 20, p. 111).  The varying density of  these three layers evidently
 diminishes their power of conducting vibrations to the  parts within,
 whilst it does  not  oppose the propagation of those vibrations  in the
 direction of the  layers themselves.
   The manner  in which the bones of the skull are  united  together
 has an evident reference to the  physical properties of their inner and
 outer tables.   The sutures  are formed by the dovetailing of the outer
 table; the inner  being cut straight, and simply placed in apposition (a
 layer  of cartilage  intervening), forming a  sort of harmonia.  The
 inner table, which is the brittle one, is not  dovetailed, because its
 teeth would break readily; but the  toughness and  elasticity  of the
 outer table fit it  well for such a mechanism.   On the same principle,
 Sir C. Bell remarks, a carpenter joins wood, which is tough  and
 elastic, by tenon and mortise or by dovetailing; but, if pieces of glass
 or marble are to  be joined,  cement is employed for that purpose.
   The principal  part  of the vault of the  cranium is formed by the
 parietal bones, which rest upon  the wings  of the sphenoid, and upon
 the temporal bones: these  overlap the lower borders of the parietal
 bones in such  a way as to prevent  them  from starting outwards.
 They act on the  principle of the tiebeam in the roofs of houses.
   At certain exposed situations  the bones  experience a thickening  of
 their structure, causing tuberosities, which are familiar to descriptive
 anatomists.  These contribute to the strength of the roof of the  skull:
 in front, in  the frontal bone on each side of the middle line; laterally,
 in the parietal bones, and, behind, in the centre of the occipital bone.
 At this last  situation two ribs, analogous to groinings in  architecture,
 intersect each other: one extends from the centre of the frontal bone to
 the most projecting part of the occipital foramen ; the other passes hori-
 zontally across the occipital  bone, and terminates  immediately behind
 the wedge-like processes which  are formed by the petrous portions of
 the temporal bones.   The occipital protuberance, which is the  point
 of intersection of these groinings, is the "thickest and strongest part
 of the skull;  and it is the  most exposed, since it is the part of the
head which would  strike upon the ground when a  man falls  back-
wards."   (Sir C. Bell.)
   Of the Spine.—The  spinal column, in man, is a vertical, elastic
    10 
138
ORGANS OF LOCOMOTION.
pillar,  expanded  inferiorly where  it rests  upon the  sacrum.  It is
composed of a series of light and  spongy bones, between each pair
of which (except the first) a  compressible  and elastic disc  of fibro-
cartilage is placed.   It has a three-fold office in the human subject:
first  it is the great  bond of connection between all the  parts of the
skeleton; secondly, it forms a canal for the  lodgment and protection
of the spinal cord ; and thirdly, it is a column of support for the head.
For these purposes the spinal column requires considerable  strength,
as the central pillar of the trunk: it needs mobility, to adapt itself to
the various attitudes and movements of the body, and elasticity, to
guard the tender organ contained within it, as well as the brain, from
concussion.
   The strength of the  spinal  column  is abundantly  provided for in
the powerful ligament which binds the bodies of the  vertebra? toge-
ther in front {anterior common ligament), and in the strong and elastic
intervertebral discs,  which  at once connect and separate them.   The
degree of motion which may take place between  any two  vertebra?
is regulated  partly by the  thickness of the intervertebral disc, and
partly  by the disposition of  the  joints of the articular processes.
When the latter are vertical in  their direction, the vertebra? are  so
locked in, that their movements are very much impeded ;  but when
they approach the horizontal  direction, as in the neck, the  range of
motion is greater.   The mobility of the spine  may be compared to
that of a chain ; between any two links of which  there  is  but little
motion, while the whole chain is abundantly pliant.   This restriction
of motion between each pair of vertebra? enhances the strength of the
column, and affords complete protection  to  the  spinal  cord, which
would speedily suffer, did  any vertebra pass  beyond its prescribed
limits.
   In the flexuous form of the  spinal column, and in the connection of
the vertebral lamina? by broad bands of yellow elastic ligament, we
see further provision for its elasticity, in addition to that afforded  by
the discs of fibro-cartilage which lie between the bodies  of the ver-
tebrae.  The concavity in the region of the back is doubtless intended
to give full scope to the play of  the important organs within the tho-
rax ; and the cervical and lumbar curves necessarily  result from this,
in order that the relation of the  whole column to the  line of gravita-
tion of the body may be duly preserved.  The triple  curvature of the
spine  enables  it to  yield with less jerk than if it  were  a straight
spring, or one that  could bend only in a single direction.  " It yields
in the direction of its curves,  and  recoils, and so forms the most per-
fect spring, admirably calculated to carry  the head without jar or in-
jury of any kind."
   The pliancy of the spinal column favours its flexion in  various
directions, in obedience to the action of the numerous muscles which
are inserted  into the vertebral processes.   Nothing is more common
than to see a misshapen and crooked spine produced  by the predomi-
nance of action given to certain sets of muscles, through the habitual
assumption of awkward attitudes:  most of  the curved spines  which 
THE PELVIS.
139
occur in weakly females may be traced to uncorrected bad habits  as
their orip-in.*
  The spine, gradually expanding at its lower part, rests upon the
base of the sacrum ; and the last lumbar vertebra is separated from
that bone by a fibro-cartilaginous disc.  The sacrum forms a wedge
separating the pelvic bones, and is admirably adapted to transmit the
weight of the spine to them.
   Of  the pelvis.—"The spinal column," to  use the words  of Mr.
Mayo, " rests on an elastic hoop, in  the extreme circumference  of
which on either side the deep cups are wrought which receive the
heads  of either  thigh-bone.   But this  elastic hoop  is  not  disposed
vertically, but slants  in such a manner, that, when  we alight upon
our feet, the force of the arrested motion tells in great measure  on
the extensor muscles of the hip."
   In the articulation of the sacrum with the ossa innominata we see
remarkable  provision against its displacement backwards, by a force
acting from above downward, the direction in  which the superin-
cumbent weight bears, or even  by one acting from  before back-
wards.  This security is obtained not  only by the strong ilio-sacral
ligaments,  which  tie  the  bones together behind, and the cartilage,
which intervenes between the ilium and sacrum, and adheres firmly
to both, but also by the double wedge-like shape of the sacrum itself:
for this bone is wider above than below, so  that it can thereby resist
the downward pressure; and it has a  greater width before  than be-
hind, which enables  it to  oppose the  pressure  in front.  And Mr.
Ward  has shown  that the sacrum is also well  secured  against dis-
placement forwards, not only by the  general compactness which the
sacro-iliac joints derive from their ligaments and cartilages, but also
by the cuneiform character which the bone assumes about the middle
of the  articular surface, where the base  of the wedge is turned in the
opposite  direction to that wThich it occupies either at the upper or the
lower  part of the articular surface.f
   These provisions for the strength and security of the sacrum are of
great importance to the general mechanism of the pelvis, whether we
regard it as a  bony girdle constructed for  the transmission  of the
weight of the trunk to  the thigh-bones, or as an osseous cavity de-
stined to contain and protect certain  important viscera.
   Viewing the pelvis in the former light, we must notice the thick-
ening of the iliac  bones along either side of its upper outlet.  The
groinings, thus formed, terminate opposite the  acetabula, and trans-
mit  the superincumbent weight, which they share with  the  sacrum,
to each of  those cavities,  whence  it is again transferred to the heads
of the thigh-bones; they  are  formed of dense  compact substance,
which contrasts strikingly with the  thin lamellated structure of the
surrounding osseous tissue.
   The obliquity of the pelvis has a  twofold object; first, with refer-
ence to the  weight from above ; and, secondly, with  respect  to con-

  * Dr. Anion's remarks bearing upon this subject deserve a careful  perusal.—See
his Elements of Physics.
  -j- We refer for further details on this subject to Mr. Ward's excellent work, p. 256. 
140
ORGANS OF LOCOMOTION.
cussions transmitted upwards by the lower limbs, in  leaps, or other
rapid movements.   In both instances, the shock is distributed  over
a greater extent of surface, and is participated in by a greater number
of joints, than if the pelvis were placed directly beneath the spine ;
for it is obvious, that, were the  axis of the pelvis vertical,  and the
femora placed perpendicularly under it, the weight from above would
bear its chief force upon the sacrum, and the concussion from below
would be felt in the hip-joints alone.
   In  progression, the  whole pelvis receives the  concussions, when
they proceed from above or from below.  Hence the  ossa pubis are
united by an intervening elastic fibro-cartilage;  and any disturbance
of this joint during pregnancy, or in the act of parturition, occasions
great difficulty to the patient in walking, or even in maintaining the
erect posture.
   Of the Thorax.—The thorax is a conoidal cavity, slightly flattened
on its anterior aspect.  It is  constructed with obvious  reference to
lightness, elasticity, and  mobility;  all these qualities being requisite
for its adaptation  to  the  ever-varying movements of the organs it
contains.
   The walls of the chest are formed behind by the dorsal vertebra?, to
which twelve ribs are articulated  on  each side: seven of these, the true
ribs, are connected to either margin of the sternum by pieces of cartilage,
which are of the same shape and breadth as the ribs themselves.  The
ribs are articulated by their heads and tubercles with the bodies, as well
as with the transverse  processes of the vertebra?, and  enjoy  at these
points a limited gliding motion in the upward or downward direction.
The direction of the  true  ribs is forwards, sloping downwards; the
obliquity being greatest in the lowest ribs, least in the first rib.  The
mobility which each rib  enjoys  at  its  vertebral articulation, permits
this direction to be altered by muscular action ; and the ribs,  under
the influence of their elevator muscles, pass from the sloping to the
horizontal position.  By  this change the dimensions of the chest are
enlarged in  the transverse as well as in  the antero-posterior direction,
for the middle curved  portions of the ribs are carried  outwards, and
therefore brought further apart from each other; and their sternal ex-
tremities are moved forwards, accompanied by the sternum,  the dis-
tance of which from the  dorsal vertebra? is  thereby increased.  The
forces, which depress the ribs, restore their planes of position to their
previous oblique direction, and the  two diameters of the chest to their
former dimensions.  It is scarcely needful  to add that the elevation
of the ribs accompanies inspiration, and their depression expiration.
   The following happy comparison between the thorax and the pelvis
is from the  pen of Mr. Mayo.
   " When we compare together the several regions of the trunk, we
observe that it is laid out in corresponding organs, or pairs of organs,
on either side of a centre, which is formed by the five lumbar verte-
brae.  Above the lumbar vertebra?  are the dorsal; above these, the
cervical: below the  lumbar vertebra?  are  the sacral bones; below
these, the  coccygeal.  To the  dorsal vertebra? and  to the  sacrum,
bones are articulated, which have the double office of forming a vis- 
THE EXTREMITIES.
141
ceral cavity, and of throwing to a convenient  distance from the me-
sial plane the bones of the  extremities.   The  ribs and  sternum, the
clavicles and scapula?, form, with the dorsal vertebra?, an organ strictly-
analogous  to  that formed by the ossa innominata  and the sacrum.
But the chest for the function of respiration requires to be continually
altering its dimensions, and the upper extremity is  characterized by
the extent and  velocity of  its  movements, rather than by strength:
to suit both these objects, the chest and shoulder are formed of many
bones, that are  movable in  various senses; the ribs are capable  both
of rotating upon their sternal and vertebral joints, and of being raised
or depressed upon their vertebral joints,  carrying with them the  ster-
num : the clavicle again rolls upon the sternum, and the scapula rolls
upon the convexity of the  ribs.  On the other hand, the  pelvis, as
regards the viscera,  is  intended merely for  their  support; and if,
during labor, a  temporary enlargement of its lower  aperture is re-
quisite, the flexibility of the joints of the os coccygis in the female
skeleton, with the temporary yielding of the ligaments, affords a suf-
ficient provision for this object: the inferior extremities again require
to be articulated to a solid, unyielding platform,  upon which  they
may poise  the incumbent weight of the trunk and head.   The bones
of the pelvis  are for  these  reasons few,  weighty, massive, and  knit
together immovably.    Thus  accurately do  the  points, in  which a
resemblance is wanting between the chest and pelvis,  preserve the
analogy between these parts."
   Of the Extremities.—In no part of the skeleton is the adaptation of
anatomical disposition and  structure to function more strikingly ob-
vious than in the bones of the extremities.
  The lower extremities form powerful  pillars of support for the trunk
in the  erect posture.   The  great strength  of the  femur  and tibia,
which form the principal portion of  each pillar, fit them  admirably
for this office; and it is interesting to notice that dense osseous tissue
in each of these bones is most abundant in those situations where the
greatest strain of the pressure from above is felt.  This may be   seen
in a transverse section of either, when  a  dense spine of bone is found
corresponding to the concave surface of each; this is most distinct
in the femur, where the  dense  bone alluded to constitutes the  linea
aspera.
  The femur is curved forward, and this incurvation gives elasticity
to the  bone,  and aids in distributing the force of concussions.   Its
shaft is inclined downwards and inwards, so that the opposite femora
approach each other interiorly at the  knee-joints, while they are sepa-
rated  by a  considerable interval above.  And this interval is increased
by the head and neck of each femur being united to  the shaft at an
obtuse angle; this angle  is one  of about  135 degrees  in the male; it
is somewhat smaller in the female.
  It is evident that the femur  must suffer  in point of strength  from
this mode of junction of its neck and shaft, for a  bone without any
bend in its axis must  necessarily be more capable of resisting down-
ward  compression, than one consisting of two pieces  united at an
angle.   But we observe here, as in other parts of the mechanism of 
142
ORGANS OF LOCOMOTION.
the human body, that the disadvantage in one respect is more  than
counterbalanced by certain advantages which this peculiar arrange-
ment offers, and which could be attained in no  other way ; for the
junction of the neck with the shaft throws the thigh-bone outwards to
a certain distance, and leaves abundant room for  the play of  the  ad-
ductor  muscles :  this could  only  be attained  otherwise by greatly
enlarging the pelvis in the transverse direction.   And again, in  the
movements of  the femur, much  is gained ; for  rotation  can  be  per-
formed with little muscular effort by reason of the  favourable leverage
afforded by the neck of the  bone and the trochanter major.   The
increased power  thus given  to  the  rotator muscles has considerable
effect in walking, which is on that account performed more lightly,
and without any circumduction of the limb.
  It is owing to this disposition  of the neck of the thigh-bone, that,
when its lower extremity advances in the  vertical plane, its head and
neck turn on  a horizontal axis; in other words,  that the  angular
motion  of its shaft is converted  into a rotatory  movement at the hip-
joint.  And from such an arrangement this great advantage  results,
that in the various motions or states  of the joints, as extreme or par-
tial flexion, extension, &c, the same, or very nearly the same, extent
of the articulating surfaces is  exposed to pressure: for, as Mr. Ward
expresses it, the rotation of a  hemispherical head within  a socket  of
the same form involves no diminution of the extent of the contiguous
articulating surfaces;  but the  angular motion  of a joint  of this kind
throws part of the ball out of the socket, and leaves part of the socket
without bearings to  rest upon,  so that the weight, instead of being
distributed equally over the whole surface Of the head, is concentrated
upon that portion which remains within the cavity.  (Ward, loc.  cit.)
  Moreover, the joint gains as regards the extent of flexion by this
conversion of  angular into rotatory motion, for  an angular motion  in
the acetabulum would be readily checked by the edge of the cavity
coming in contact with the  neck  of the  bone;  " whereas rotation
meets no such check in the conformation  of the joint itself, but may
be continued indefinitely,  until opposed by the  tension of ligaments,
or some other  adventitious obstacle."
  In the structure of  the extremities of the femur, we find evidence
of much beautiful mechanical contrivance, in the disposition of the
compact tissue, and of the rods or  fibres  of the cancellous texture,
having an obvious reference to the direction of the weight to  be  sus-
tained as well  as to the dispersion of concussions.  The  neck of the
thigh-bone,  having to bear  considerable  superincumbent weight, is
strengthened on its inferior surface  by an arch  of compact  tissue,
gradually increasing  in thickness as it proceeds  from above  down-
wards, and well suited by its  rigidity to oppose bending;  but on its
upper surface the compact tissue is  thin, and  the  reticular  texture
consists of somewhat  arched fibres  freely interwoven, running parallel
to that surface, and disposed so as  to present a surface to resist  the
direct influence of pressure (fig. 18, p.  106).   The  direction of the
fibres of  the  reticular texture  of the  inferior part of the  neck is
chiefly downwards to  the trochanter minor, and it seems  to establish 
THE UPPER EXTREMITY.
143
a communication between the osseous tissue of the head of the bone,
and the dense structure which forms the lower part of the neck.
   The lower extremity of the femur is almost entirely composed of
cancellated texture, and affords  a broad surface, for articulation with
the head of the tibia to form the knee-joint.  As  the tibia is placed
vertically under it, it not only transfers the weight from above to that
bone, but  it is  particularly exposed to suffer from concussions con-
veyed upwards by the  tibia.  Its  structure seems disposed  so as to
facilitate the dispersion of such concussions, the sides of the condyles
projecting considerably beyond the surface  of the  shaft of the bone,
and there  being but little  continuity  of tissue between  it  and the
lower end of the bone.
   Of the bones of the leg, the  tibia,  from  its strength  and  size, is
evidently that which is destined to support the thigh; the fibula must
be regarded as entirely accessory in its office, affording attachment to
the interosseous ligament, and forming a greater extent of surface for
the  origin  of muscles.   By its lower extremity it supports the ankle-
joint on the outside.
   The tibia rests  upon the astragalus, and through that bone trans-
mits the weight to the foot.  The  length of this  organ,  its breadth,
and its arched form, adapt it as a basis of support for the body in
the  erect posture, and as an instrument of locomotion.   It  obtains
elasticity, and a certain amount  of mobility, from its being composed
of several small and light bones articulated together.  These bones,
although almost entirely composed of  reticular texture, possess con-
siderable power of resistance to direct pressure in those directions in
which the strain would chiefly bear in  the  movements of the organ,
and this is to  be attributed to the direction of the fibres  of their
cancellous tissue.   The principal elasticity of the foot is longitudinal,
by reason of its arch being in that  direction, resting upon the heel
behind, and on the toes in front; but it also yields somewhat in the
transverse direction, or that of the arch formed by the cuneiform bones.
The extension of the os calcis backwards not only adds to the length
of the longitudinal arch, but it also affords  a considerable leverage to
the muscles of  the calf of the leg.
   Upper Extremity.—The disposition  and  structure of the bones  of
the upper extremity afford a marked contrast to those  of the lower.
The latter are organs of support, and therefore  are solid, firm, strong,
and, withal, elastic.   The former are destined to  perform extended
motions, as well as minute and nicely adjusted ones ; and, therefore,
while they possess all the  requisite  strength, they  are light, present
little expanse of surface, and are articulated by numerous  very mov-
able articulations.
   The scapula  and clavicle are the media  through which  the bones
of the arm are  united to the trunk.   The former bone is remarkably
thin and light, and seems little more than a  surface of attachment for
various  muscles, on  whose actions  the  extensive movements of the
arm  depend. By the clavicle it is  connected to the sternum,  through
the sterno-clavicular articulation, the movements of which, although
occurring only in two planes, intersecting each other at right angles, 
144
ORGANS OF LOCOMOTION.
 are such  as to favour a wide  range of  motion in the shoulder.  So
 necessary is this joint to the general movements  of the shoulder, that
 any injury or disease of  it, or of the bone itself,  shows itself speedily
 in the impediment offered to those movements.  And the law of the
 development of this bone in the lower  animals  is clearly connected
 with a necessity for a wide range of motion in the anterior extremity.
 In those animals that employ the anterior extremity only as an instru-
 ment of progressive motion, there is no clavicle ; hence this bone is
 absent from the  skeletons of Pachydermata, Ruminantia,  Solipeda,
 and the motions of the shoulder are only such as may be  required for
 the flexion and extension of the limb.  In the Carnivora,  where there
 is a slight increase in the range of motion of the anterior  extremities,
 a rudimentary clavicle exists; and in this class w7e  observe that  the
 size of the bone bears a direct relation to the extent of motion enjoyed
 by the limb.   Thus  it is smallest in the dogs, and largest in the cats:
 in these animals it  has no attachment to  either the sternum or  the
 scapula, but is enclosed  in the flesh, and does not occupy much more
 than half the space between the two bones last named.   " But how-
 ever imperfect,"  says Sir C. Bell,  " it marks a correspondence in the
 bones of the shoulder to those of the arm  and  paw, and the  extent
 of the motion enjoyed.   When the bear stands  up, we perceive, by
 his ungainly attitude, and the  motion of his paws, that there must be
 a wide difference in  the  bones of his upper extremity from those of
 the ruminant or soliped; he can take the keeper's hat from his head,
 and  hold it; he can hug  an animal to death.  The ant-bear, especially,
 as he is deficient in  teeth, possesses extraordinary power of hugging
 with his great paws; and, although  harmless in disposition,  he can
 squeeze  his enemy, the jaguar, to  death.  These actions, and the
 powers of climbing,  result from the structure of the shoulder, or from
 possessing a collar bone, however imperfect."  (Bridgewater Treatise,
 p. 48.)
  In those Mammalia that  dig and  burrow in the ground, or  whose
 anterior extremities are so modified  as to aid them in flight, or which
 are skillful in seizing upon and holding objects with their paws, the
 clavicle is fully developed, and extends the whole way from the sca-
 pula to the sternum.   Thus in the Rodentia this bone is very perfect,
 as, for example, the squirrel, the beaver, the rabbit, the rat, &c. The
 bat affords an example of a very strong and long clavicle, as also do
 the mole and the hedgehog among the Insectivora.
  Among the Edentata  those  tribes possess a clavicle whose  habits
 are fossorial, as the ant-eater,  the  armadillo, and even the gigantic
 extinct megatherium.  In the Quadrumana the clavicles  are  strong,
 and curved, as in the human subject.
  The clavicle possesses considerable elasticity by reason of its curves;
 a property obviously of the greatest importance to it, because, as the
 bond of connection of the shoulder to the trunk, it is liable to partici-
 pate in the many concussions to which the upper extremity is exposed.
 This point has been put to the test of direct experiment by Mr. Ward.
 He  employed the clavicle of a well-developed  male  subject,  of the
middle age: this was placed upon  a smooth surface, with its shaft 
THE UPPER EXTREMITY.
145
perpendicular to the plane of a wall, against which its inner extremity-
rested ; a smart blow was then struck with  a hammer  on the outer
extremity of the bone in the direction of its  long axis; the  hammer
rebounded from the end of the bone, which sprang to  a distance of
nearly two feet from the wall.
   The humerus is the principal lever of the upper extremity: in man
it is light, and its articular extremities are constructed to contribute
to the formation of very movable joints.  The bones of the fore-arm
are also remarkable for their lightness and elasticity; and they move
freely, not only on the humerus, but on  each  other.  The movements
of pronation and supination, which  are necessary to the free  and full
use of the hand, are performed by the rotation of the radius round an
axis passing through its head and neck ; the slight curve in the shaft
of the radius causes its carpal extremity to pass through a considera-
ble space during the rotation of the forearm.
   The contrast between the solidity and elastic  firmness of the foot,
and the lightness, flexibility and mobility of the hand, is most striking.
The analogy between the anatomical elements of both organs is com-
plete : but they are modified to  suit the office for which each is de-
stined ; the foot as a basis of support, the hand as a prehensile organ.
The  hand is modified remarkably from the form of the foot by the
divergence of the  outer  metacarpal bone, to form  the  thumb :  this
bone at its articulation with the carpus  enjoys a considerable degree
of mobility,  in  virtue of which exists the opposable  faculty of the
thumb ; a power wrhich, in a  state of perfection, is peculiar to the
human hand.
   While  the hand is  so remarkably  mobile, it is well protected
against the effects of compression, or  concussion, by the  number of
its joints, and the interposed cartilages  and fibro-cartilages,  and the
soft covering of fat which lies beneath the skin of the palm ;  and its
strength  is abundantly provided for in  the strong ligaments which
connect the  bones to each other, and the fibrous expansions which
cover them.
   One of the most wonderful circumstances in the construction of the
hand, is its adaptability to an infinite number  of offices.   A powerful
organ of prehension, it is yet capable of adjusting the finest pieces of
mechanism, or of exposing to view the minutest wonders of  nature :
an admirable and most delicate instrument of touch,  it may neverthe-
less be employed as a fearful and deadly weapon of offence :  at  one
time it may be used to lift  great weights, to  pull at the cable, or to
turn  the windlass;  and, again, it will  execute the most varied  and
rapid  movements, in  the performance  of works or artifices which
human talent has invented.
   The hand is  the obedient minister of man's  volition and of his
genius, and,  too often, the blind slave of his emotions and his  pas-
sions.

  The following references are subjoined:—The various treatises on General Ana-
tomy;  the article Articulation, in the Cyclopsediaof Anatomy and Physiology; Mayo's
Physiology, chap. xi.; Bell's Animal Mechanics;  Arnott's Elements of Physics, vol.
i. p. 218; Anatomie Descriptive, par Bichat, t. i.; Outlines of Human Osteology, by 
146
ORGANS OF LOCOMOTION.
F. 0. Ward, a work to be strongly recommended, as well for its exact and clear de-
scriptions, as for the excellent and original views on the mechanism of the skeleton,
with which it abounds.  We shall be glad to see it published in a form more suitable
to its great merit.
                        CHAPTER VII.

ACTIVE ORGANS OF LOCOMOTION.--OF MUSCLE.—MUSCLE WITH  STRIPED
  FIBRES—MUSCLE  WITH  UNSTRIPED  FIBRES.--MUSCULAR ACTION.—
  ATTITUDES AND MOVEMENTS OF  THE FRAME.

  The  principal movements of the  body, and  all those by which
locomotion is effected, are performed by means of a tissue termed
muscle,  endowed with the  power of contracting, and  consisting,
chemically,  of fibrine.  This substance is arranged in the form of
unbranched  fibres of definite size and  structure, and which,  when
examined under a  high magnifying power, are found  to be of two
kinds, distinguishable from one  another  by the presence  or  absence
of very close and minute transverse bars or stripes.   The fibres of the
voluntary muscles, (or those  whose movements can be either excited
or controlled by volition,) as  well as the fibres of the heart, and some
of those of  the oesophagus, are  striped;  while all other muscles, in-
cluding those of the alimentary  canal, the  uterus, and bladder, all of
which are involuntary, are unstriped.
  The elementary fibres of the  voluntary  muscles  are connected to
one  another  by areolar tissue, and arranged in sets  parallel to one
another.   They are  supplied with vessels  and nerves, which lie  in
the  intervals between  them; and  are attached, by their extremities,
through the  medium of tendon, aponeurosis,  or some form of the
fibrous tissue, to the parts which they are  destined to move.  They
form organs, for the most  part  solid and  elongated, but which are
sometimes expanded into a membranous shape.
  The sets of fibres of the involuntary muscles,  on the other hand,
usually cross each other at various angles, and interlace, and  they are
always arranged as  membranous  organs enclosing a cavity, which
their contraction serves to constrict.   The  heart, besides being inde-
pendent of the will, agrees in both these anatomical  characters with
the  involuntary muscles, and is only allied to the voluntary by the
presence in its fibres of the transverse stripes.
  We shall  commence with a description of the two forms of fibre.
  Of the striped fibres.—The length of these is usually about that of
the  muscle to which they belong, but occasionally they are  interrupted
by tendinous  intersections, as in the  rectus abdominis and semiten-
dinosus; and it is very common  for them to fall short of the  length of
the  whole organ, in consequence of an oblique disposition, as seen in
penniform muscles.   In the sartorius they often  exceed two feet in
length, while in the  stapedius they are not two lines.   They vary in 
STRIPED MUSCLE.
147
diameter from  eV to  iTVt of an inch, being
largest in Crustacea, fish  and reptiles, where
their irritability is enduring; and smallest in
birds, where it is most evanescent.   The in-
dividual fibres, however, vary considerably
in thickness in the  members of the several
tribes, and  even in  the same animal and
muscle.   Their  average  width in  man  is
about  7^q- of an inch.   They are not cylin-
drical, but flattened  more or less, by being
closely packed together.  This may be ascer-
tained in the recent state, or still better by
a transverse section of a dried muscle. Small
interspaces are left, however, for the passage
of the capillary blood-vessels along the angles
of junction, and sometimes between the  con-
tiguous sides.   (Fig. 36.)
   Internal structure.—The beautiful cross-
markings on the voluntary fibre  have been
known from the early days of microscopical
research, and  have  given  occasion to  a
variety of  hypothetical  and generally  me-
chanical solutions of the problem of contraction ;  which, by warping
the minds of observers,  have  had  the  effect of greatly complicating
an already difficult subject, that of  the internal anatomy of the fibre,
which can only be determined by pure observation.  Fontana alone
among the older anatomists abstained from vague speculation ; and he
arrived nearest to the truth.  He found that the fibre was apt to split
up into fine fibrilla?, each of which was a series of particles; and he
imagined that the transverse lines were  caused by the regular apposi-
tion side  by side of the particles of the contiguous fibrilla?.   It was
customary both before and since his time, as  at the present day, to
regard the fibre as a bundle of  smaller ones, whence the term  primi-
tive fasciculus, first  given to it  by him  and  adopted by Muller:  but
this view of the subject is imperfect.   The fibre always presents, upon
and within  it,  longitudinal dark  lines,  along which it  will generally
split up  into fibrilla?; but it is  by a fracture alone  that such fibrilla?
are obtained.  They do  not exist as such in the fibre.   And, further,
it occasionally  happens that no disposition whatever is shown to  this
longitudinal  cleavage ; but  that, on the contrary, violence causes a
separation along the transverse  dark lines, which always intersect the
fibre in a plane perpendicular to its axis.  By such a cleavage, discs,
and not  fibrilla?, are  obtained ; and this cleavage is just as natural,
though  less frequent than the former.  Hence  it is as proper  to say
that the fibre is a pile of discs, as that it is a bundle of fibrilla? : but,
in fact, it is neither the one nor the other, but a mass in whose  struc-
ture there is an intimation of the  existence of both, and a tendency
to cleave in the two directions.   If there were a general disintegration
along all  the lines in both  directions,  there would result a series of
particles, which may be  termed primitive particles or sarcous elements,^
Fig. 36.
 Transverse sections of striped
muscle that had  been  injected
and dried, magnified 70 diame-
ters :—a. From the Frog. b. From
the Dog. b. b. Section of elemen-
tary fibres, showing their angular
form and various size. a. a. Sec-
tions of the injected capillaries,
showing the position they occupy
among the fibres, a1 .Transverse
branch between two longitudinal
capillaries. These figures show
the greater vascularity of the
muscle, with the narrower ele-
mentary fibres. 
148
ORGANS OF  LOCOMOTION.
the union of which constitutes the mass of the fibre.   These element-
ary particles are  arranged and  united  together in the two  directions.

                                 Fig. 37.
  Fragments of striped elementary fibres, showing a cleavage in opposite directions; magmfi'l
300 diameters:—1. Longitudinal cleavage.  The longitudinal and transverse lines are both seen.
Some longitudinal lines are darker and wider than the rest, and are not continuous from end to end:
this results from partial separation of the fibrilla;. 6. Fibrilla?, separated from one another by violence
at the broken end of the fibre, and marked by transverse lines equal in width to those on the fibre.
7. 8, represent two appearances commonly presented by the separated single fibrillar.  (More highly
magnified.)  At 7, the borders and transverse lines are all perfectly rectilinear, and the included
spaces perfectly rectangular.  At 8, the borders are scalloped, the spaces bead-like.  When most
distinct and definite, the fibrilla presents the former of these appearances.—2. Transverse cleavage.
The longitudinal lines are scarcely visible. 3. Incomplete fracture following the opposite surface of
a disc, which stretches across the interval and retains the two fragments in connection. The edges
and surface of this disc are seen to be minutely granular, the granules corresponding in size to the
thickness of the disc, and to the distance between the faint longitudinal lines. 4. Another disc nearly
detached. 5. Detached disc more highly magnified, showing the sarcous elements

All the resulting discs as well as fibrilla? are equal to one another in size,
and contain an equal number of particles.  The same particles compose
both. To detach an entire fibrilla is to abstract a  particle of every disc,
and vice versa.  The width of the  fibre is therefore  uniform, and is
equal to the  diameter of any one of the discs.   Its length is  the length
of any one of its fibrilla?,  and is liable to the greatest variety.
   Muller,  Schwann,  Lauth, and  others, consider, with us, that the
cross stripes  of the fibre are formed by the apposition side  by side of
the dark points seen on the separated  fibrilla?; but some believe  these
stripes to be  present only on the surface of the fibre, and to  be formed
by the spiral windings of a filament.  Considerable diversity of opin-
ion also exists as  to  the nature of the alternate  light and dark points
seen  on the individual  fibrilla?; some conceiving them to  indicate a
single spiral, others a  double spiral arrangement;  some imagining
them to be minute zigzag bendings, others  indentations, and others
still  that they depend on  the  alteration  of two kinds  of substance.
On this account  we  shall explain in  a few words  our  reason  for
adopting the  view above summarily given.   A soft mass made  up of
an immense congeries of highly refracting particles cannot but exhibit
many deceptive appearances when  viewed by transmitted  light, and
through glasses of bad defining power.   The slightest disturbance  of
its interior  structure will affect the refractions, which will thus be rea-
dily  made to  disguise and  modify the true form and arrangement of its
integrant parts ; on which account great care and circumspection, and 
STRIPED MUSCLE.
149
Fie. 38.
 Transverse section of three elementary
fibres of the dried pectoral muscle of ithe
Teal (Querqztedula crecca), treated with
weak citric acid ; showing the round re-
fracting particles separated from one an-
other. The cut edge of the tubular sheefch
of each fibre isalso seen, as well as the
capillary vessel s, a, in the intervals.
a total freedom from bias, are requisite for  an observer who would
not be misled to mistake appearances for realities.
  That the  stripes are not  caused by a structure distinct from the
fibrillae, and present only on the surface of the fibre, is evident from
the following facts:
   1.  That a transverse section of a fibre
shows it to be solid, and not hollow;
and that the ends of fibrillae, as seen
on the section, exist throughout its inte-
rior just as on its surface  (fig. 38).
   2.  That fibrilla? taken from any part
of  a  fibre are marked  with light  and
dark  points, corresponding in distance
and force with the transverse stripes  of
the fibre.
   3.  That  with  a  high magnifying
power, applied  to  a  thick fibre, we
may bring all parts  of its interior  into
focus  in   succession,   and  perceive
throughout the same kind of stripes.
   The  occasional appearance,  therefore,  of  these  stripes being con-
fined to the surface is deceptive.  They are sometimes more strongly
marked  there, partly because there is a greater condensation of the
tissue there, and partly from  the circumstance of the fibre being usu-
ally immersed, when examined, in a fluid of less  density than itself.
This  appearance is always greatly  diminished by placing the fibre in
syrup.  But the point of greatest interest is as  to  the nature of the
markings on the individual fibrilla? or discs.   It is unsafe to come to
a conclusion on this  question from any appearances seen on the entire
fibre; for it is clear that the  relative  position of the particles may be
very  easily deranged,  and their regularity  broken, by the  slightest
injury to the mass.
   Two appearances  commonly present themselves  in  examining the
striped fibres : in some parts  the cross stripes are perfectly rectilinear,
or, if curvilinear, parallel in their course ; in other parts,  these stripes
do not extend across  the fibre, but are more or less  interrupted,
forming zigzags and enclosing spaces of a great  variety of shape and
size,  in concert with the  longitudinal stripes.  In such specimens we
see the semblance of spirals in  almost infinite  number  and variety.
The former of these appearances is  most seen in large fibres, and
where great care  has  been  used not to  drag the tissue; the latter
under the reverse circumstances.   The former seems on aprimd facie
view an unmutilated, the latter a deranged condition; and they may
be proved to be so by a further examination.
   For this  purpose we should make  choice of a fresh fibre which is
prone to separate into its individual fibrilla?, and which exhibits their
outline in the greatest distinctness and beauty.*   If fibrilla? entirely
  * The fibres of fishes will generally prove better than those of mammalia, because
they usually cleave into fibrillae having very  sharp and clear outlines; and those of
the salmon, for example, will seldom fail to do so. 
150
ORGANS OF LOCOMOTION.
isolated be now  inspected, they will be  found to present alternate
light and dark points, when the  part is a little  out of focus.  The
light points are the centres of highly refracting  particles, acting as
lenses; the dark  points, the intervals between them (fig. 37, 8).  If
now the focus be carefully adjusted, and the achromatic condenser
be employed for the purpose of defining the outline with the utmost
precision, each dark interspace between the  refracting points will be
found to be reduced to two very slender straight lines, crossing the
fibrilla in a perfectly transverse direction, and giving the light spaces,
as now seen, a rectangular figure (fig. 37, 7).  Now, it is absolutely
certain that no spiral arrangement could produce, or even co-exist
with, these unequivocal appearances; but it is not difficult to compre-
               hend how a derangement of the lateral parallelism of
   Fig. 39.      these refracting particles should produce an  appear-
               ance of spirals in the fibre, or how two fibrilla? running
               together, but with their particles slightly deranged,
               should wear the same very deceptive aspect.
                 In fig. 39 is represented the border of  some fibres,
               from which several of the sarcous elements have been
               removed accidentally by  maceration in  weak spirit.
               The remaining ones project in lateral series, evincing
               their adhesion to one another in  that direction, and
               the non-existence of any spiral arrangement.
                 The size of the particles  composing the fibre may
               be measured in one direction by the transverse stripes
               formed by their union.
                 The following average, deduced  from numerous
               observations, shows great uniformity in this respect.

                                   Eng. In.       No. of Observations.
         In the Human subject.......^^.........   27
         " Mammalia generally......tovus.........   15
         "Birds...............T^.........    7
         "Reptiles.............TT^ff.........    7
         "^sh...............TTJ^.........20
          " Insects..............v5ta.........    8

   In the opposite  direction, or that marked by the distance between
 the longitudinal  dark lines of the fibre,  their  diameter is  less, often by
 one half.  It  is important to remark, that these measurements are
 taken  from  uncontracted  specimens,  since during contraction the
 relative diameters  of the particles are changed.
   Of the  sarcolemma.—The striped fibre is enclosed  in a  tubular
 sheath or sarcolemma,  adapted to  its surface,  and  adhering to  it.
 This  consists  of a transparent, very delicate, but tough and elastic
 membrane, which isolates the fibre from all other tissues.   In gene-
 ral, it has no appearance of any kind of structure; but in the case of
 bulky fibres, where it is strong  in  proportion, faint indications may
 be detected of a complex interweaving of filaments far  too  minute to
 be  individually recognized.  It occasionally has small corpuscles,
 the remains of cell-nuclei, in contact with it.
 
THE SARCOLEMMA.                      151
   This  membrane  may be  sometimes  seen forming a  transparent
border to the fibre beyond the  limit of the cross stripes; or it may
be seen  stretching between the  separated fragments of a  fibre which
has been broken within  it, for  its toughness will often resist a force
Fie. 40.
Fie. 41.
 Fragments of an elementary fibre of the
Skate, held together by the untorn but twist-
ed sarcolemma.
 Part of an elementary fibre from the Skate,
treated with liq. potassse; showing a protrusion
through the sarcolemma:—Corpuscles are seen
scattered throughout the mass, and some de-
tached ones are represented; their average di-
ameter is one-thousandth of an English inch.
before which its brittle  contents give way.   If the fibre be immersed
in acid, it swells, often so  suddenly as to burst the sheath at nume-
rous  places, and protrude in the form of small  hernia?.   These her-
nia? are very peculiar and illustrate the account already given of the
internal composition of the  fibre; for the particles of the protruded
mass  are necessarily deranged, and their lateral parallelism destroyed.
Now, the  result of this is the production  of the most  beautiful  and
varied curves, intersecting one another, very similar to those already
spoken of on the  injured  fibre, and wearing a very plausible aspect
of spirals (fig. 41).   Again, the  sarcolemma  may be seen  raised in
the form of vesicles from the surface of the fibre, in certain states of
contraction in water, which  will  be reverted to.  By one or more of
these modes of demonstration,  we  know  that  this isolator of the
sarcous tissue invests the striped  elementary fibre of voluntary muscle
in all animals.   Its existence is as yet doubtful  in the heart.
  Every fibre  is attached by its extremities  to  fibrous tissue, or to
some tissue  analogous  to it; but an  accurate examination of  this
difficult  subject lends  no  countenance  to the ordinarily received
opinion, that this tissue is prolonged over the whole fibre from end to

                                Fie- 42.
               a

         5O0.0.Qo4


dooooooooodoooo
  Elementary fibre from \.he leg of Ihe large Meat-fly (Musca vomitoria): a. a. Line of termination
of the fibre, along which the tendon,«, is attached to it. m. Central series of corpuscles.—Along the
margin, the sarcolemma is elevated by water, (which has been absorbed,) and is thereby shown to
be adherent to the margin of the discs. 
152
ORGANS OF LOCOMOTION.
Fig. 43.
end, as  its cellular  sheath; nor is  this  view reconcilable  with the
physical requirements  of the  case.  It  is extremely difficult to iso-
late  a muscular fibre,  with the tendinous fibrilla?  pertaining to it,
either in mammalia  or birds  ;  but this  may be occasionally accom-
plished in fishes, and in  certain muscles of insects.   In these exam-
                                   ples, the minute detachment of the
                                   fibrous tissue may be seen to pass,
                                   and  to  become  attached  to  the
                                   truncated   extremity of  the  fibre.
                                   The fibre  ends by a perfect  disc,
                                   and  with   the  whole  surface of
                                   this disc the  tendon is  connected
                                   and continuous.   The sarcolemma
                                   ceases abruptly at  the circumfer-
                                   ence of the terminal  disc, and here
                                   some  small part of  the tendinous
                                   material appears to be joined to it.
                                   In other  cases, where  the muscle
                                   is fixed obliquely to a membranous
                                   surface,  each fibre  is  obliquely
                                   truncated at  its extremity, at  an
angle  determined by the inclination of  its axis; instances of which
may be  seen  among the Crustacea, and elsewhere.
   The researches of Valentin and  Schwann have shown that a muscle
consists, in the earliest stage,  of a mass of nucleated cells, which first
arrange themselves in a linear series, with more or less regularity, and
then unite to constitute the elementary fibres.   As this process of the
                               Fig. 44.
  Attachment of tendon to an elementary fibre
from the  Skate :—On bringing deeper and
deeper portions of the specimen into focus,
along the line of union, a. a., fresh tendinous
wavy filaments and striated muscular parts
came into view together,  t.  Tendon, in.
Muscle.
 Stages of the development of striped muscular fibre.
 1. Arrangement of the primitive cells in a linear series.—After Schwann.
 2. The cells united. The nuclei separated, and some broken up; longitudinal lines becoming ap-
parent—From a foetal calf three inches long.
 3. 4. Transverse stripes apparent.  In 3. the nuclei are  internal, and bulge the fibre.  In 4, they
are prominent on the surface.—From a fetal calf of two months old.
 5. Transverse stripes, fully formed and dark ; nuclei disappearing from view.—From the human
infant at birth.
 6. Elementary fibre from the adult, treated with acid; showing the nuclei — Ma°-nified about
300 diam.                                                       °

union of  the cells is  going forward,  a deposit of contractile material
gradually takes place within them, commencing on the inner surface,
and advancing towards the  centre, till the whole is solidified.   The 
UNSTRIPED MUSCLE.
153
Fij
 45

ill
 deposition  occurs  in  granules, which,  as  they come into view, are
 seen to be  disposed in the utmost order, according to the two direc-
 tions already specified.   These  granules, or sarcous elements, being
 of the same size  as in the perfect muscle, the transverse stripes
 resulting from their opposition are of the same  width as in the adult;
 but, as they are very few in number, the fibres which they compose
 are of corresponding  tenuity.  From the very first moment of  their
 formation, these granules are parts of a  mass, and not independent of
 one another; for, as soon as solid matter is deposited in the cells, faint
 indications of a regular arrangement in granules are usually to be met
 with.  It is common for the longitudinal lines to become well-defined
 before the transverse ones.   When both are become strongly marked,
 as is always the case at birth, the nuclei of the  cells, which  were be-
 fore visible, disappear from view, being shrouded by the dark shadows
 caused by the multitudinous refractions of the light transmitted through
 the mass of granules: but they can still  be shown to exist in the per-
 fect fibre, in all animals, and at all periods of life, by immersion in a
 weak acid:  which, while it swells the fibrous material of the  granules,
 and obliterates their intervening lines, has no action on the nuclei.
    These nuclei in  insects  are arranged, in the  early con-
 dition of the fibre, as a  single or double series  along the
 axis (fig. 45);  and, in  the  adult state, they  retain  the
 same position (fig.  42).   In vertebrate animals  they are
 scattered more irregularly,  but  at pretty equal  distances
 throughout the  mass in both fcetal and  adult  conditions.
 In the fully formed fibre, if it be large, they lie at various
 depths within it; but, if small, they are at or near the sur-
 face.  They are oval  and flat, and of so little  substance,
 that though many times  larger than the  sarcous elements,
 and lying amongst  them, they do not interfere  with their
 mutual apposition and union.  These corpuscles are  fre-
 quently the cause of irregular longitudinal  dark streaks,
 seen in the  fibre by transmitted light.   They usually con-
 tain some central  granules or  nucleoli.  It is doubtful
 whether the identical corpuscles, originally present, remain
 through  life,  or  whether successive  crops  advance and
 decay during the progress of growth  and nutrition: but it
 is certain, that as development proceeds, fresh corpuscles
 are deposited, since their absolute number is far greater in
 the adult  than in the foetus, v/hile their number relatively to the bulk
 of the fibre, at these two epochs, remains nearly the same.
   Muscles grow by an increase, not of  the  number, but of  the bulk
 of their elementary fibres: there  is reason to believe that the number
 of fibres  remains through life as it was in the foetus, and  that  the
 spare or muscular build  of the individual is determined by the mould
in which  his body was originally cast.
   Of the unstriped fibres.—This  variety possesses less interest  than
the other, in consequence of the apparent simplicity of its structure.
The fibres consist  of flattened  bands,  generally of a pale colour,
bulged at frequent intervals by elongated corpuscles, similar to those
     11
 Elementary
fibre from the
larva of the
Libellula,  in
an early stage
of   develop-
ment ; show-
ing the cen-
tral  row  of
corpuscles.—
Magnified 300
diam. 
154
ORGANS OF LOCOMOTION.
 Fibres of unstriped muscle:—e.  In
their natural state,  a. Treated with
acetic acid, showing the corpuscles. 6.
Corpuscles, or nuclei, detached, show-
ing their various appearances.
          Fig. 46.            of striped muscle and capable of being
                            displayed by the  same process.*  The
                            texture of these fibres  seems to be ho-
                            mogeneous.  By transmitted light, they
                            have usually a soft, very finely mottled
                            aspect,  and  without a  darkly-shaded
                            border.   Sometimes the mottling is so
                            decided as to appear granular, and oc-
                            casionally these  granules  are arranged
                            in a linear  series for some  distance.
                            This condition is probably an approach
                            towards the structure of the striped fibre,
                            for these granules are about the size of
                            the sarcous elements already described.
                            It is generally to  be seen  more or less
                            distinctly in the gizzards of birds;  and
                            may be now and then met with in the
                            fresh muscle of the  stomach, intestinal
                            canal,  urinary bladder,  and  Uterus of
                            mammalia.   The  ordinary diameter of
                            the unstriped fibre is from ^s to  2m
                            of an inch.
                               It might be expected, from  this ac-
count of the appearance of these fibres, that their discrimination from
other tissues would be often difficult.  The peculiar texture, however,
the size, the soft  margin, and, above all, the  presence of numerous
elongated oval corpuscles with two or three granules near their centre,
are characters which, when  united,  will  seldom be mistaken.  As  a
number of fibres commonly take a parallel course together, the bulg-
ings occasioned by the  corpuscles  give rise  to partial  longitudinal
shadows, extending for some way beyond  the corpuscles in the inter-
vals of the fibres.  As  these  irregular longitudinal shadows occur
pretty uniformly throughout a bundle of fibres, and  as  some of them
are necessarily out  of focus, while  others are in  focus, the whole
mass commonly presents a confused  reticulated  appearance, which
has given rise  to an almost universal notion that  the fibres interlace
one with another.    This  idea, however, is, in most cases erroneous.
It is doubtful whether these fibres are invested by a sarcolemma: none
has hitherto been  detected in an unequivocal manner.   It is also still
a  matter of speculation  how they terminate,  or whether they in all
instances have a termination.   In the  case of the transverse fibres of
the intestine, for  example,  it  is  uncertain whether each fibre sur-
rounds  the  canal  once,  returning into  itself as a ring, or more than
once, as a spiral; or  whether it passes only partially round it, the
circle  being completed  by others.   Whether the areolar tissue (the
representative  of the fibrous),  that is found in  connection with these
fibres, serves to give them an  attachment, by  union with their extre-
mities, or by involving them in its meshes, is also altogether unknown.
   * In some specimens, however, of both varieties of fibre, they may be discerned
without the addition of an acid. 
DISTRIBUTION OF MUSCLE.
155
In the gizzard of the bird, the ends of the fibres are united to white
fibrous tissue, thus  making an approximation to the striped fibre, as
they do in colour.  But we have not been able, after diligent search,
to detect the true transverse stripes, which Ficinus describes to exist
in this organ.
   Of the distribution of the  two varieties of fibre in the body.—The
striped fibre is met with in all muscles of the body whose action can
be directly  influenced by the  will, and also in those of the pharynx,
the oesophagus, and the heart.  In the  oesophagus it seems to be min-
gled with the other variety to a somewhat uncertain extent.  In some
specimens from the human subject we have failed in detecting any
in the lower half of that  tube, either  in the circular or longitudinal
layer; but in another example we have found them to within an inch
of the stomach.*   It is still unknown in what manner the two kinds
of fibre are  arranged at their point of junction: some supposing them
to be intermingled  ; others, that they pass into one another by imper-
ceptible gradations  of structure.  The former of these views is the more
accordant with our  own observations;  and Mr. Mayo mentions  a fact,
which seems to corroborate it:  " When the nervi vagi are pinched, one
sudden action of the fibres of the  oesophagus ensues, and, presently
after, a second, of a slower character, may be observed to take place."
{Physiology, 3d  ed.  p. 41.)   The characters of  these  movements
would appear to indicate the existence of both varieties of fibre.
   The  cross stripes  on the fibres  of the heart are not usually so
regular, or distinct, as in those of the  voluntary muscles.  They are
often interrupted, or  even not visible  at  all.   In some of the lower
animals their sarcous elements never form transverse stripes.   These
fibres are usually smaller than the  average diameter of those  of the
voluntary muscles  of the  same subject by two-thirds, as stated by
Mr.  Skey;  and in  most parts of the parietes of  this viscus they are
not  aggregated in  parallel sets, but twine and change their relative
position.  This may be seen  in a  well-boiled heart.  Striped fibres
have been found  in the iris, in the small muscles of  the ear, and in
those muscular fasciculi that  surround the  urethra immediately in
front of the prostate.   They are also  found  in the sphincters  of the
anus and  vagina.
  The unstriped  fibre is met  with  in the alimentary canal, and con-
stitutes the double  layer investing that tube.  It also forms the mus-
cular coat of the  bladder,  and that of the uterus.  The dartos owes
its contractility to  the presence of fibres of this variety; which, in
consequence of their admixture  with  a  great abundance of areolar
tissue, have  been often overlooked.  But they may be  detected by
the addition of acetic acid, which, by bringing into view the peculiar
corpuscles they contain, distinguishes  them from both the white  and
yellow fibrous', elements of the areolar tissue.  A very distinct peri-
staltic contraction  may be often  discerned  in the  dartos, extending
across the raphe of the scrotum, and too similar to the contraction of
unstriped  muscle  to be mistaken.
  * Among the lower animals, Mr. Gulliver has pointed out similar varieties.  (Pro-
ceed,  of Zool. Soc, No.  81.)  (See also Lancet,  Aug. 1842.) 
156
ORGANS OF LOCOMOTION.
   The fibres which have been described  as peculiar to the dartos
seem  to be  nothing  more  than a certain modification of the areolar
tissue in that  region.   The  erection  of the penis may be,  in part,
owing to  the  compression exerted  on the  superficial  veins of the
organ by a continuation of a structure analogous to the dartos, which
is continued over the base of the penis under the skin.   The  erection
of the nipple also occurs, on any mechanical irritation, with a motion
so  very  like muscular contraction, that a  layer of these might per-
haps be  found  under the skin of that region.   And it may be matter
of  question how far the  general contractility of the skin may be de-
pendent on a diffusion of this tissue, in small quantities, throughout its
areolar structure.   The excretory ducts of  all the  larger glands seem
to possess a covering of fibres pertaining to this variety: such is the
case with the ductus choledochus in birds, and probably in mammalia,
and with the ureters and vasa deferentia.   The bronchial tubes may
be  here alluded  to in  their capacity of an  excretory apparatus, as
furnishing  the best  marked  example  of  this arrangement.   The
trachealis  muscle consists  evidently of the unstriped fibres,  and  the
same may be traced down the  bronchial  ramifications  as far as the
air-cells themselves, though  not into them.   The  distinctive charac-
ters of this form of muscle may here be unequivocally discerned ; and,
if anatomists had been better acquainted with them,  there would not
have been room for those disputes regarding the  muscularity of the
bronchial tubes which have so long attracted the interest of practical
physicians.  Recently, indeed,  there has been added to the  satisfac-
tory evidence  of anatomy the fact,  that these fibres may be excited to
contraction by the galvanic stimulus.   {Dr.  C. J. Williams, on Dis-
eases of the Chest.   Last edit. Appendix.)   In  the  case of other
glands,  it is still unknown  how far  the  muscular  coat invests  the
ramifications of the duct: it is most  likely that it  gradually ceases a
short way within the organ, and at least  it seems clear that no portion
of the secreting membrane  itself is ever invested by it.


             Distribution of the two kinds of fibre in the animal scale.

  The  striped fibres have been found in all vertebraled animals, and in insects,
Crustacea, cirropods, and arachnida; and future researches will probably show
them to be even  more extensively diffused.  But in the lower animals we find
that the distinctive characters of the two varieties begin to merge together and be
lost; especially where the fibres are of diminutive size.   The transverse stripes
grow irregular, not parallel, interrupted: a fibre will, perhaps, possess them  only
near its centre,  where its development is most  advanced,  and its contractile
energy greatest.  Even the peculiarities of the unstriped fibre are sometimes no
longer to be met  with in parts which are undoubtedly muscular, as the alimentary
canal of small insects.  It is evident that fibres of the usual bulk would be greatly
too  large  for the requirements of the case; and they consequently seem to be
reduced within limits which deprive them of those anatomical characters by
which alone we can elsewhere positively aver their existence.  It is possible that
a tissue identical  in nature and properties with that of striped muscle, may be the
effective agent to  which are due those wonderfully vivacious movements witnessed
in the bodies of many of the minutest infusoria, where the best microscope can
hardly discern even the organs put in motion. 
TENDONS.
157
   Each one of the elementary fibres now described may be properly
regarded as a  distinct and perfect organ.  In some of the smaller
forms of animal life, we have examples of a striped muscle consisting
of a single fibre;  and not only so, but this fibre reduced to a single
series of sarcous elements, or a fibrilla.  But in all the larger animals,
and in the human body, with which we are specially concerned, soli-
tary fibres never occur: they are always aggregated in parallel series
of  greater or smaller size, and associated with other tissues,  which
minister to their nutrition, or to their mechanical connection either to
one another or to  neighbouring parts.  Thus the compound organs
termed muscles are formed.
   In these, the angular figure of the fibres results from their contact.
The sets in which they are packed usually contain ten, twenty, thirty,
or more; these again being united into larger sets, and so on, so as to
form the variously sized fasciculi and lacerti of Prochaska and others,
until the whole muscle is formed, consisting, it may be, of very many
thousands.  Though the fibres of a small set are always  parallel, and
the primary sets  usually  so, it often happens  that the larger sets are
placed obliquely to one another, and therefore do not act in the same
direction ; and, even when all are parallel to one another, they are often
oblique to  the  cord or tendon their force acts upon.  Such muscles
are styled  doubly or singly penniform, from their  resemblance to the
plume on a writing-quill.  All such  arrangements, infinitely  varied,
are mechanical contrivances by which symmetry of form, or extent of
motion, is obtained at  the expense of power.
   White fibrous tissue reaching from the end of a  muscular fibre to
some structure which is to serve as a fixed attachment for it, or  which
it is intended  to  move, is called a tendon.  The fibrous tissue thus
running from many contiguous fibres (as those of  a whole muscle) is
usually united into a single tendon.  This may be lamellated, cordi-
form, &c, according to the arrangement of the muscular fibres them-
selves (see p.  81).
   Tendinous fibres are much less bulky than the muscular fibres of
which  they are the prolongation; and from  this result  many conse-
quences.  Tendons are employed for symmetry, and  where muscular
structure would be useless, from the mechanical impossibility of more
than a certain amount of motion in a part.  Moreover, where a muscle
consisting of a large number of fibres has to be  attached to a large sur-
face, the tendinous fibres are diffused; but, if the same muscular sub-
stance has  to be fixed to a small point of bone, the  tendon must be
collected  into a  cord.  Now, it would  be  impossible for all these
muscular fibres to  be attached to  the  tendinous  ones on  the same
level, on account of the  great difference in  bulk between the two
structures.   Hence, in such cases, we find the  muscular  fibres to end
in tendon  in regular progression one after the other, and the  tendon
at its muscular extremity to be expanded, some of its  fibres  being
long, others short.  And  yet the  inconvenience which would ensue
from the muscular fibres  being of unequal length in the  same organ,
is counteracted by the tendon at their other extremity having its fibres
precisely reversed; as in the rectus of the thigh, and numerous other 
158
ORGANS OF LOCOMOTION.
 instances.   Where muscular fibres are really of different lengths in a
 muscle, it is because, from the direction in which they act, they have
 to shorten to different degrees.   Thus, in the square pronator of the
 fore-arm, the  deeper and shorter fibres are attached to a part of the
 radius, which in pronation passes through a much smaller space  than
 that to which the superficial and longer fibres are fixed ; and under the
 innumerable modifications of muscular form in man and animals, how-
 ever force is sacrificed to mechanical exigencies, or other causes, it
 is invariably accomplished with the utmost economy of power  con-
 sistently  with the end in view ; there is never any  waste, never any
 force provided which is not wanted.
   Where a  great mass of fibrous  tissue runs into a muscle, the num-
 ber and  obliquity of the muscular fibres are very  much increased,
 while the length of each  is diminished ; and, as a general result, the
 power of such a muscle is great,  the extent of its contractions com-
 paratively limited.
   A given  mass of contractile material may be arranged  as a few long
 fibres (as in the sartorius), or as many short ones (as  in the masseter):
 its  contractions would, in the former  case, be characterized by their
 extent; in the latter,  by their power: for, cateris  paribus, the extent
 is as the  length, the power as the thickness.
   The terms origin and insertion are employed with great convenience
 in ordinary language to denote the more fixed and the more movable
 attachments of muscles.   In human anatomy general consent has
 sanctioned  their use, and  even with few exceptions their particular
 application  to each  muscle in the  body; although this assignment is
 in many cases  arbitrary, in consequence of its being impossible to de-
 termine which attachment is the more frequently the  fixed one.
   The arrangement of the fibres in the heart is very peculiar.   With-
 out attempting a particular account of their course, we may state  that
 they do not preserve the same parallelism, nor extend straight be-
 tween two points, as in  the voluntary muscles, but twine  round  one
 another, and around the  organ, in a very intricate and  more or less
 spiral figure.  Most of them come from the tendinous cord encircling
 the orifices  of  the ventricles, and, after winding through their walls,
 return either to some part of the same circle of tendon, or end as one
 sort of columna? carnea? in the ventricles  by union  with the  chorda?
tendinea?.
  In the muscular coat of  the alimentary canal, of the bladder and
 uterus, the   unstriped fibres are disposed, as in  the heart, so as to
enclose a cavity, but without having, as in that organ, any point at
which they can be said to commence or terminate.   In the alimentary
tube they are arranged in two lamina?, the respective fibres of which
take a  course at right angles to each  other.  In the bladder the ar-
rangement is reticulate.   The elementary fibres form sets of variable
thickness, which at numerous  points send off" detachments  to  join
neighbouring bundles, whence has sprung the notion that the fibres
 are branched.   It  is manifestly, however, the sets of them only that
 are branched ; the unstriped, like the striped fibres, being invariably
simple from  end to end.  In the uterus the disposition of the fibres is 
       AREOLAR TISSUE AND BLOOD-VESSELS OF MUSCLES.     159

essentially similar, calculated to allow of great variety in the capacity
of the cavity they encircle.
   Of the areolar tissue of muscles.—This tissue is much more abun-
dant in  the  voluntary than in  the  involuntary muscles.  To the
former it gives  an  external investment, which  sends septa into the
intervals between  the  larger and smaller packets of fibres, and thus
enables them to  move  in some  degree independently of one another.
The density of these general and partial sheaths is proportioned  to
the amount of pressure to which the organ may be subject, as is ex-
emplified in the superficial muscles of the back, and in those super-
ficial muscles generally where  a fibrous  aponeurosis does  not  exist.
The areolar tissue does not usually clothe every individual fibre from
end to  end, giving it  a cellular sheath, except in cases where the
elementary fibres are of large dimensions. The areolar tissue, besides
affording protection to  the muscular fibres, admits of motions between
them ; and,  by  forming a connecting  bond  between neighbouring
bundles, it  must also  serve the important  office of limiting undue
motions of one part of  a muscle on another part.  But a principal use
of  it appears to  be that of furnishing a  resisting nidus  in  which the
delicate  vessels and nerves can traverse the interstices of  the fibres,
and by which they can be protected from hurtful dragging during the
unequal and oscillating movements of the fibres of a voluntary muscle
in its state of activity.  This idea is supported by the fact that scarcely
any areolar  tissue exists in the  heart,  or in  the  unstriped muscles
generally.   In the heart, though the contraction is  powerful, it  is
instantaneous, or nearly so, and therefore probably more uniformly dif-
fused, so that neighbouring fibres must be less moved on one  another
than in the more sustained contraction of a voluntary muscle.   More-
over, the mutual intertwining of even  the  elementary fibres in this
organ is  in many parts of it so intricate, as to contribute much to their
mutual support; and, in the other involuntary muscles, the contrac-
tions are slowly and evenly progressive  along the fibres of the same
set.
   Of the blood-vessels of muscles.—The arteries and veins of muscles
commonly run together; and most of the arterial branches, to within
two removes from the capillaries,  are  accompanied by  two vena
comites.   They invariably pass  more  or less  across the direction of
the fibres, divide and  subdivide, first in the  intervals  between the
larger sets, then between the smaller  sets, till the ultimate twigs in-
sinuate themselves between the fibres composing the smallest bundles,
and break up into their capillary terminations.  In this  course the
vessels supply the areolar tissue, their own  coats, and the attendant
nerves.  The capillary plexus  of the  areolar membrane  consists  of
irregular but pretty equal-sized  meshes, and contrasts strongly with
that of the muscular tissue itself.
   The proper capillaries of muscle are  quite  characteristic  in their
arrangement, so that a  person,  who has  once seen them,  can never
afterwards mistake them.  They consist of longitudinal and  transverse
vessels:  the longitudinal always following the  course of the element-
ary fibres, and lying in the intervals between them ; the  transverse 
160
ORGANS OF LOCOMOTION.
Fig. 47.
being short communications placed at nearly equal distances between
the longitudinal ones, and crossing nearly, or quite, transversely over
or under the fibres.   The manner in which the  longitudinal  vessels
are placed  in  relation to the fibres, is seen in fig. 36, represented
as they are  seen  on  a transverse section.   They usually occupy the
interstice between three or more fibres, but  sometimes also the space
between the contiguous surfaces of two fibres. The length of the longi-
tudinal vessels does not usually exceed the  twentieth of an inch ; in
other words, the  terminal twigs of the  artery and vein pertaining to
the same capillary are seldom further than that apart.   The length of
the transverse anastomosing capillaries necessarily varies  with the
thickness of the fibres over which they pass (fig.  36, b, a).
  The diameter of the capillaries of muscle varies, like that of others,
with the size of  the blood-particles of the animal.  It is, however,
only just sufficient to allow of the particles to pass.   If a fragment of
                       a frog's muscle, perfectly fresh, be examined,
                       series of blood-particles will be  seen in the
                       longitudinal capillaries.  These particles are
                       compressed and elongated, sometimes to  a
                       great extent, evidently by the  narrowness of
                       the canal which contains them.  It may seem
                       at first  sight not doubtful that in the living
                       creature these elastic blood-discs are similarly
                       elongated in their passage through the  vessels
                       of muscle, but  the  admirable researches  of
                       Poiseuille will  perhaps serve to  explain this
                       appearance without our being driven  to sup-
                       pose the presence of so formidablean  obsta-
                       cle to the capillary circulation  through these
                       organs.   It is  more  probable that  the  con-
                       traction of the  vessels, and the compression
                       of the  blood-discs,  occur on the escape  of
                       some of their  contents being  permitted by
                       the cutting off of the fragment for microsco-
                       pic examination.  The coats of the capillaries
                       of muscle  consist of a  simple  diaphanous
                       membrane, in which a few irregular-shaped
                       cytoblasts occur at infrequent intervals.
                         It  results from this description of the capil-
                       laries of muscle, that their number must cor-
                       respond nearly to that of the elementary fibres;
                       consequently, that the  same amount of mus-
                       cular tissue, arranged as a large  number of
                       small fibres, would be supplied with a larger
                       absolute  number of  capillaries  than  if ar-
                       ranged as  a  small  number of large  fibres.
                       This difference  of vascular supply is exceed-
                       ingly remarkable, and  will be  reverted to in
                       considering the contractility of muscle.
  Of the nerves of muscle.—Nerves being  the appropriate channel
0/ V
 Capillaries of a small fascicu-
lus of muscular fibres from the
neck of the Dog:—a. Terminal
twig of the artery, v. Terminal
twig of the vein.  p. Plexus of
capillaries e. Elementary fibre,
to show the relative size and
direction of those to which the
capillaries, here  represented,
are distributed. 
NERVES OF MUSCLES.
161
through which muscles  are  excited to contraction, we  have now to
inquire into  the  manner in which  the  two tissues  communicate
together.   As far  as is at present known, all  muscles  in  the larger
animals have nerves distributed to them; and, if we extend the in-
quiry to those extremely simple and minute muscles which  have been
already alluded to  as existing in the smallest of living  creatures,
though we can no longer trace nerves, yet our  inability to  do  so pro-
bably depends more on a corresponding simplicity of the nervous sub-
stance itself, so that it ceases to  be  anatomically recognizable, than
on its entire absence.  So general is the connection of the two tissues,
and so apparently indispensable for the  subjection of the  muscles to
the purposes of the organism of which they constitute a part, that we
may regard it as constant and necessary.
   The distribution  of the  nerves through  muscular structures has
always been a subject of great interest to those who looked to  this
line of inquiry for some  clue to'the explanation, either of that won-
derful active connection  subsisting between them, or  of the nature of
the contractile act itself.   But though the anatomical  results accruing
from this inquiry are of a highly satisfactory kind, considered in them-
selves alone, yet they cannot be  said to have hitherto contributed in
any great degree to  the elucidation  of these  mysterious  questions.
The best mode of inspecting the arrangement of the ultimate nervous
twigs is, to select a very thin muscle, as one of the abdominal mus-
cles of any small animal, or one of the muscles of the eye of a small
bird, to steep it in weak acetic acid,
and then  to thin it  out  under the
compressorium.   The primitive tu-
bules  of the  nerve may then  be
readily distinguished with a mode-
rately high power.   They separate
from  one  another at first in sets,
afterwards  in twos, threes, or fours;
and, if these be followed, they will
be found ultimately separating from
one another,  forming arches, and
returning either to the same bundle
from which they set out, or to some
neighbouring one (fig. 48).
   In this loop-like course they ac-
company to some extent the minute
blood-vessels, but do not accurately
follow them in their last  windings,
since'their distribution is in a differ-
ent figure.   They  pass among the
fibres of the muscle, and touch the
sarcolemma as they pass; but, as far
as present researches have informed
us, they are entirely precluded by
this structure from all contact with the contractile material, and from
all  immediate intercourse with it.  How then  shall we  explain  the
Fig. 48.
*rx
 Loop-like termination of the nerves in vo-
luntary muscle.—After Burdach. 
162
ORGANS OF LOCOMOTION.
transmission of the nervous influence to a material thus enclosed ?  If
it were wise or safe  to go a single step in advance of pure observa-
tion  on so abstruse a question,  we  might suggest,  resting on the
seemingly sure ground of exact anatomy, that this  influence must be
of a nature capable of emanating beyond the limits of the organ which
furnishes it.  But further than this, as to how, or to what extent this
influence may so emanate, or as to what may be its nature, it would,
perhaps, in the  present state  of  knowledge, be hardly  warrantable
even to speculate.
   The number of fibres in a muscle is always exactly proportioned to
the power  demanded, and  their length to  the amount of shortening
required of them;  but, these circumstances being secured, muscular
parts  are  subject  to great  variety of form,  being short, thick, or
rounded, long, slender, or flat, according to their position relatively
to particular bones, joints, other muscles, or the like.  Thus, all are
compactly knit and adapted  to work in concert, without any mechani-
cal interference with  one another ;  and perfect symmetry, both of shape
and action, is provided for.
   We notice that the muscles are arranged on the skeleton in a great
measure in sets, having opposite actions; as,  for example, the flexors
and extensors, pronators and supinators of the fore-arm. It is evident
that the action of every muscle depends solely on  its mechanical at-
tachments, and that  a tendon running round to a different side of a
limb might quite reverse a given action.   But we find that in general
the muscles of the same set  are designed to act together, not only by
their attachment on the same side of a joint, but by a supply of nerves
from the same source (congeneres).  Yet even this can confer no
special action of extension or flexion, but only an  association of ac-
tion which may be both at once ; for example, the  flexors of the toes
extend  the  ankle, and the  extensors of the  toes bend it.   Even  a
single muscle, the rectus femoris, flexes  the thigh, and  by the same
action extends the leg.  Muscles opposed in action  are termed an-
tagonists.   This antagonism is in most cases  required by the neces-
sity there  is for an active  moving power in opposite directions; but
it serves the important accessory purpose of elongating muscles when
they cease to be contracted, as we see illustrated by the  presence  of
elastic or  some other force for the same  purpose,  when  there  is no
antagonist muscle.   When  antagonists act together, the part is fixed.
   The locomotive framework may be regarded as a series of levers,
of which  the fulcrum is for  the most part in a joint, i. e. at one ex-
tremity, the   resistance at  the further end,  and the power (or the
muscle) in  the intermediate portion.   In most cases the muscles are
attached  very near the  fulcrum, as  in the familiar instance of the
biceps, inserted into the tubercle of the radius.  By this disposition,
a contraction of a single  inch in the muscle  moves the  hand in the
same time through  the extent of a foot, but then the  hand moves
through every inch with only the  twelfth part of the power exerted  in
the muscle; i. e. a resistance at the  hand equal to one-twelfth of the
force of the muscle would stop its motion.   Thus, force  is converted
into extent and velocity of movement, at the  same time that the great 
FUNCTIONS OF MUSCLES.
163
inconvenience is avoided of having the muscles extended like  bow-
strings between  the distant ends of jointed continuous levers.   By
the junction of two or  more levers in one direction, as in the dif-
ferent segments of  the  extremities, the extent and velocity of their
united actions are given to the extreme one.   A blow of the fist may
be made to include the force of all the muscles engaged in extending
the shoulder, elbow, and wrist.
   In  the  conspicuous example of  the tendo-Achillis,  inserted into
the os calcis, the resistance (or the  weight of  the body) rests on the
astragalus, intermediate  between the power and  the  fulcrum, which
is here the ground, pressed by  the ball of the  foot.   The  extent and
velocity  of motion  are here converted  into  power.  If the tendo
Achillis  draws on  the heel when the foot is off" the ground, the front
part of the foot is  extended on the lower end of the tibia as a ful-
crum, and exhibits an instance of the other of the  three varieties of
lever.
   Of the function of muscles.—The great property of muscular tissue
is that of shortening in  a particular  direction, and this  property is
called contractility.  It is not that  mechanical power which elastic
substances possess  of shortening themselves on the  removal of some
force which has stretched them, but it is an  endowment, responsive
to appropriate stimuli, and diminishingor disappearing with the healthy
state  of the tissue (p. 69-70).
   The distinction  between the contractility, the elasticity, and  the
physical  tenacity of a muscle  may be illustrated by the following imag-
inary experiment:   Suppose the leg of an animal so  severed from
the trunk as to  hang by a single muscle, which, after retaining its
contractility for some time, were  gradually to lose it.  The limb
would at  first  be  borne up by the contractile power:  but, as that
ceased, the muscle would elongate  under the weight, and  the limb
would remain suspended simply by the tenacity of the part.  If, now,
the muscle were stretched between  the  hands, we should find it to
possess some slight elasticity.  The elasticity and much of the tena-
city of muscles  are attributable  to  the sarcolemma, and to the  ca-
pillary and areolar  tissues.  It does  not appear that elasticity is in
any degree a property of the  sarcous elements, and their tenacity must
be comparatively slight:  but it is the sarcous tissue alone that pos-
sesses contractility.
   Although it is universally allowed that the   muscular tissue is the
contractile substance, yet the strange question  has been raised, and is
still warmly debated, whether it possesses this power in itself, and in-
dependently of all other tissues: some contending that nerve  is neces-
sary to confer contractility on muscle,—to charge it, as it  were, with
this property; others, that nerve is only necessary to call it into action;
and others, that the property is the  essential  attribute of the tissue,
and totally independent of all  nerves.  The  time  is past when  the
intricacies of this keen contest can be threaded with any benefit to
the student, and we therefore refrain from attempting to follow them.
We shall prefer offering him a  view of the facts of  the subject, as at
present known, drawing our conclusions as they arise. 
164
ORGANS OF LOCOMOTION.
  The contractility of muscle is exhibited in two varieties of contrac-
tion, passive and active.
  Passive contraction is that which every muscle is continually prone
to undergo, by the  mere quality of its tissue, as long as it remains in
its natural situation in the body.   The muscles are ever  kept on the
stretch by the nature of their position and attachments, and cannot
have  their  ends so  approximated,  by attitude  or  otherwise,  that
their tendency to shorten themselves  shall cease.  If, for  example,
the  rectus muscle of the thigh  have  its extremities brought  as  near
together as can be  effected  artificially by posture, they would yet be
found to approach still nearer on being freed from their attachment to
the  bones.   The stimulus  to this contraction  may be therefore con-
sidered to be that of extension.   In fractures and dislocations attended
with shortening of the limb, the  muscles adapt themselves permanently
to their shortened state by virtue of this property.  This  tendency to
contract has been distinguished by the term retractility, from its being
manifested by the retraction that occurs when the  belly of a  muscle is
cut  across.   But, in this instance, the retraction would appear to be
in part caused by an active contraction excited by the stimulus of the
injury.  It has been also styled tonicity.   It is well exemplified in all
those  contracted states  of muscles which follow paralysis of their
antagonists, as when the features are  drawn towards the  healthy  side
in hemiplegia.   The passive contraction of muscles is continually op-
posed to their elongation  by the  active or passive contraction of antago-
nists,  and restores them  when  that subsides.   By it they are accom-
modated to an attitude  artificially given,  when no muscular effort is
required to maintain it.   When no active contraction is  present  in a
limb,  the passive contraction remains; and being brought to a state
of equilibrium in  all the muscles, by their mutual antagonism, the
limb is said to be at rest.  This is the general condition during sleep,
in which the posture assumed by the  limbs is  determined by the re-
lative power of  antagonist muscles: the flexors overcome the exten-
sors, and hence the limbs are bent.
  Active contraction is attended with  those striking manifestations of
power that specially characterize muscle.  It is always excited by a local
or partial stimulus, and is always exerted in opposition to another force
within the body, which it is able more or less  completely to  master.
The opposing force is generally the passive contraction of antagonist
muscles, as well as the weight or resistance of some part  upon which
the  muscle acts directly; but it may  be the elasticity of  parts, or, in
the  case of  hollow muscles, the  resistance of  their own  contents.
Active contractions are also frequently opposed to one another in the
maintenance of a fixed posture.   Active contraction is partial  and in-
terrupted, both in extent and duration.  It requires intervals of rest,
being attended with exhaustion  of the power which produces it; which
exhaustion, in the voluntary muscles, is attended with  the  sensation
called muscular fatigue.
  The contractility of muscles, therefore,  is being ever exerted, in
obedience to the equable stimulus of tension, without fatigue, in the
production of what we have termed passive contraction;  when it is 
STIMULI TO MUSCULAR CONTRACTION.
165
affected by a powerful, partially-applied stimulus, active contraction
results, inducing the necessity for subsequent rest.  But there seems
no good  ground for supposing the contractile force to differ in its
nature, when exhibited under these different modes of action.
  Stimuli to muscular contraction.—Whatever is capable of inducing
contraction in the  muscles, when either naturally or unnaturally ap-
plied to them, is termed  a stimulus.   In the living body, the muscu-
lar fibres  are in most instances made to contract by the immediate
influence of  the nervous tubules distributed among them; and this
influence,  however called into  play, should be styled the nervous
stimulus, or the vis nervosa.  This nervous stimulus, then, is simply the
effect of such a condition  of the motor nerves as enables them to induce
contraction in muscular  fibres which are  in the due relation to their
terminal loops.  Of the nature of this condition, and of the mode of its
production, we are as completely ignorant as we are of the nature of all
those other conditions of the nervous system on which the  manifestation
of its various phenomena depends ; but we know some little of the
agents by which the nerves are thrown into this state.   The chief of
them are volition, emotion and  impressions carried by the  afferent
nerves to the nervous centres, and there affecting the efferent, or motor
nerves, independently of volition or consciousness; but to these are to
be added various  impressions from diseases and injuries of the motor
nerves, either at their origin or in their course, together with pressure,
heat, chemical substances, electricity, &c, applied to  their texture.
The former are the  natural excitants of the nervous stimulus in the living
body; the latter may be proved to possess this property by observation,
and  by experiments on nerves distributed to muscles, either in the body,
or soon after their removal from it. The power of inducing contraction
in the muscles is an endowment of those  nerves only which have a
certain  organic connection with the muscles;  and these nerves are,
therefore, distinguished as motor.
  There are other  stimuli of muscle besides the vis nervosa, which
occasion contraction in the living body ; but, in general, these affect
only the hollow muscles.  Experiment has, indeed, shown these mus-
cles  to be under the influence of motor nerves derived from the spinal
marrow ;  but it seems probable  that some of them, at least, are nor-
mally excited to contract by the stimulus of  stretching or distension,
to which they are  peculiarly liable from  their arrangement as invest-
ments to hollow viscera.  Muscles have not the capacity  of elongating
themselves that has sometimes been ascribed  to them : when  once
contracted, they remain  shortened,  notwithstanding the contractile
force have subsided, unless  their ends be drawn apart  by some ex-
traneous force.  This force  is that which has been already specified
as being always exerted  in opposition to active contraction in the
living body.   In the case of the voluntary muscles, this  force always
continues to act after  the  active contraction has  ceased  ; but in the
case of the hollow  muscles, where it consists of the resistance of their
contents, it sometimes happens that these,  when  removed, are not at
once replaced ; and hence an enduring contraction, though the active
contractile force is no longer  exerted.  Thus  an empty intestine is 
166
ORGANS OF LOCOMOTION.
reduced to the size of a tobacco-pipe, and the sphincters of the anus
and bladder are kept contracted,  without any tetanic spasm, or per-
manent expenditure of contractile force,  as has been sometimes sup-
posed.
  Now, the stimulus of distension is, in the  first  instance, nothing
more  than the elongating  force which calls into play the contractility
of a muscle under its passive form:  and there is this peculiar to  it,
that it affects equally every point of the substance of each fibre, which
no  other  stimulus can do:  and hence would result the  uniformity
which will presently be shown to characterize  passive contraction,
for contraction is an answer to a stimulus.   This consideration tends
strongly to confirm the view which we have taken of the  identity of
the forces displayed in passive and active contraction, of tonicity and
contractility.
  Other stimuli  may be  mentioned as capable of causing muscular
contraction by their direct agency on the tissue ; but it is important
to observe that these take no  share in the  production of  natural
contraction in the healthy body.   It was  long supposed impossible to
observe the  effect of stimuli on  the muscular tissue when isolated
from the nervous; and the fact, that the artificial stimuli  which in-
duced contraction when  applied  to  a  muscle itself, were the  same
with those which induced it when applied to the  motor nerves, was
considered sufficient proof that in the former case the effect was pro-
duced through the medium of nervous tissue still mingled with the
muscular.
  But this question has been brought to  an issue by the positive ob-
servation  that fragments  of the fibre of voluntary  muscle, entirely
isolated from  every extraneous  tissue, whether nerve or vessel, may
be made to contract in obedience  to a  stimulus topically applied to
them.   When such fragments are examined, they are found to con-
tract first  of  all  where they have sustained mechanical injury, viz.
at their broken extremities ; and, if water be  brought into  contact
with them, it  is absorbed, and thereby excites them to contractions,
which commence at their surface.*  The  same thing is frequently
to be observed under a different form.   A particle of foreign matter,
as a hair or a piece of dust, may be included by design or accident
in the field of the microscope, so as to touch the side of a fibre at a
single point.   When this happens, the fibre will  often exhibit a con-
traction, so plainly limited to the  point touched, as to give unequivo-
cal proof of its being the  result of the irritation of the pressure.  Che-
mical  substances may be seen  to  act  similarly, if they  be not so
powerful as to destroy the texture of the  part: and it is probable that
electricity has a like agency.   These interesting phenomena may be
  * Water has long been known as a rapid exhauster of the contractility of mus-
cles.  " Rigidity is produced almost instantaneously if warm water be injected into
the arteries of a muscle. The flesh, under these circumstances, becomes pale, in-
creased in bulk, and suddenly hardens. The operation of crimping fish consists
in dividing the  muscular fibre before it has become rigid, and immersing it in
spring water.  A small part  treated  in this manner contracts and hardens within
five minutes."—Mayo, Physiol., p. 38. It exhausts contractility  by inducing vio-
lent contraction, by which the fibre is often disorganized. 
STIMULI TO MUSCULAR CONTRACTION.
167
observed more or less satisfactorily in all animals whose fibres retain
their contractility for a sufficient length of time after removal from the
body; and the crab and lobster will be found very favourably adapted
for  the  purpose.   In many reptiles, and  fish also,  the  steps occur
slowly enough to be adequately scrutinized.
  The facts in question can  admit only of one explanation, if it be
conceded that the muscular tissue has been here separated from the
nervous: and certainly that  separation has been effected, unless the
nervous  tubules  send off from their terminal  loops  a set  of fibrils
which penetrate the sarcolemma,  and diffuse themselves through the
contractile  material within;  a supposition for which  there exists,  at
present, no foundation in the  observations of the most diligent investi-
gators of this subject.   They will, therefore, probably, be regarded
as conclusive proof that contractility is a property inherent in the  very
structure of muscle, and capable of being excited to action independ-
ently  of the instrumentality of nerves.
  An interesting phenomenon has been  pointed out  by Dr.  Stokes,
which, when illustrated by the foregoing observations, we may safely
consider as an example of contraction in the living body in  answer  to
a physical stimulus.   In various cases  of phthisis, and, indeed,  in
all  cases attended  with  emaciation, a sharp  tap with the fingers on
any muscular part is instantly followed by a  contraction, and by
the rise  of a defined firm swelling, at  the  point  struck, enduring
several seconds before it gradually subsides.  This is often so pro-
minent as to throw a shadow along the skin, and for the moment it
might  almost be  mistaken for a solid tumour.   That it is limited  to
the point struck  is full proof of its being a direct effect of the irrita-
tion, and not produced through the medium of nerves; for a contrac-
tion excited in the  latter mode would be  diffused over  the parts  to
which the nervous twigs irritated  were supplied, and would therefore
frequently occur in parts at some  distance.
  Having premised these words respecting the  stimuli of muscle, we
proceed to  consider what is known of the phenomena which attend
the act of  contraction.   It is evident that the  subject we are  now
approaching is one of primary importance, because  on the positive
information  regarding it must chiefly depend our means of judging  of
the conflicting hypotheses of the nature and laws of action of the  con-
tractile force.
  A muscle, when  contracted, is  firmer than before ; but this rigidity
is proportioned rather to the intensity of the contractile force exerted,
than to the amount of shortening occasioned by it.  The circumstance,
however, has led to the belief, that the act is  accompanied with a
compression of the substance of the muscle into a smaller compass ;
but it is, on the  contrary, well ascertained that it gains in  thickness
what it has lost in length.   The experiments  by which this fact  is
attested have  been often repeated, and their general  results accord
well together.  If a muscular mass be made to contract by means  of
galvanism  in a vessel of water furnished with a very delicate tube,
the  slightest diminution of bulk  would be at once  indicated by the
fall  of the water  within the tube ;  but the water, under these circum- 
168
ORGANS OF LOCOMOTION.
 stances, is found to retain its  level.  Mr.  Mayo varied  this experi-
 ment by selecting the heart of a dog, {Anat.  and Phys. Comment, vol.
 i. p. 12,) which, continuing to beat during some time,  was in this
 way distinctly seen to undergo no change of size.
   The  familiar  practice of accelerating the flow from the vein at the
 elbow by desiring the patient to contract the muscles of the fore-arm,
 does not, as is  sometimes imagined, show any diminution of their
 bulk, but only a forcible increase of their lateral dimensions, by which
 the  deep veins are compressed within the  inelastic  sheath  of fascia,
 and the blood diverted into the superficial channels.   In  those  mus-
 cles which have a bulging centre or  belly, as the biceps of the arm,
 the fibres are arranged in a curved form, and during contraction must
 tend towards a straight line in  the direction of the axis of the muscle.
 In such instances the blood-vessels that traverse their interstices must
 be in some degree  compressed.
  If we examine under the microscope the contracted state  of a mor-
 sel of the sarcous tissue, we find it  to present essentially  the same
 characters as that of the entire organ, a shortening in length, with  a
 corresponding increase in thickness ;  and this is true, however minute
 the fragment may happen to be.  This is all that can  be said in gene-
 ral  of the  visible features of this  remarkable  phenomenon.   Late
 investigations, instead of explaining the manner in which contraction
 is effected, by showing its dependence on  forces previously under-
 stood, have only served to display the inadequacy of the coarse and
 mechanical hypothesis, that physiologists have been so prone  to con-
 fide  in,  and to make  it more than  probable that  they must ever be
 content to repose upon the fact above stated, as the simplest which
 the most refined microscopical  analysis will ever disclose.
  All muscle  retains its contractility for  a  longer or shorter period
 after its separation from the body, or after  death.   During this period
 contractions may be  excited by the  nervous, and all other stimuli,
 which we can apply to it; and it is  certain that these contractions are
the  same in their nature with those occurring in the living body under
natural  influences.  Being also easy of inspection, they are admirably
suited to the display of the minute changes occurring in muscle during
its active state.
  The muscle with  striped fibres is  peculiarly adapted for the display
of these changes ; for, its texture not being homogeneous, but marked
throughout with  perfect regularity into spaces or  particles so  minute
as to require  to be very highly magnified before they can  be even
seen at  all, the  anatomist is provided with the means of  detecting
movements, which, without  this  circumstance, must  have  remained
concealed.
  When a piece, retaining its  contractility, is torn  up into its ele-
mentary fibres, the fragments  of these, when placed in water, are seen
to undergo a slow movement at certain points,  especially  where they
have suffered violence, as at  their broken  extremities.  This  move-
ment consists  of a  shortening  and  thickening  of the  material com-
posing the fibre, as  is shown by the general outline  of the  part, but
especially by the appearances visible in its interior.   The transverse 
MUSCULAR ACTION.
169
stripes, both  light  and dark, become longer and thinner: in other
words, the discs expand in  circumference, flatten, and  approximate
to one  another ; or, to  use  another form  of expression, the  fibrilla?
become shorter and thicker, both in the particles composing them and
the material connecting those particles (fig. 49).
   These changes are always local, or partial; and it is most evident,
from the characters they constantly present, that they are not  limited
to any determinate  regions, points, or segments, but occur indifferently
wherever the exciting cause may chance to be exerted. Neither discs
nor fibrilla? appear  to have the smallest share, as aggregations of par-
ticles bearing those particular forms, in producing the phenomena of
contraction.   A contraction  is never bounded to a particular number
of discs or fibrilla?, and is  never accurately limited  by the  interval
between two  discs.  It constantly happens, that at the edge of the
contracted part, several  discs  are  only  partially engaged in  it.  A
contraction generally, when  commencing at the broken end of a fibre,
occupies its whole width there; but, when it commences at the border
of the  fibre, it may be confined to a portion of  many discs:  and, fur-
ther, the  contractile  force is never exerted along  the whole length
of a fibre or fibrilla at once.   A contraction excited in an elementary
fibre by the contact of a hair  extends  into  the mass equally in all
directions, as  we might suppose it would do, if the mass were homo-
geneous.
   An attentive study of  these interesting phenomena  will lead to the
conviction, that, in the bare  fact of contraction, the build of the  fibre
is an item of no importance  whatever: the exquisite symmetry dis-
played in the apposition  of its component particles is, as  it were, dis-
regarded  and  overlooked ; while the whole process is to be referred
to the material itself, the ultimate tissue, whose property is contract-
ility.   This property appears to reside both in the particles and the
substance connecting them.
   The ultimate movements, therefore, on which contraction depends,
whatever they may  consist in, are molecular, and far beyond the reach
of sense.
   It will be perceived that  this view of the subject is  the only one
which  can  harmonize the fact of contraction in voluntary muscle  with
the same phenomenon in structures which have no complicated internal
arrangement of particles, as, for example, in the unstriped fibre; and
the contractility  manifested by fibrine, immediately after  coagulation,
is a property too nearly allied to the contractility of muscle (a form of
fibrine) not to  give  it additional credibility.
   In regarding  contractility, therefore, as  a property of the living
muscular fibre in general, it is meant that it resides in  it as a property
without which it would not be muscle ; and in such a manner, that no
particle, however microscopic, can be detached from muscle  which
does not of itself, and independently of the  rest, possess this property
as long as it possesses vitality.
    12 
170
ORGANS OF LOCOMOTION.
Of the differences between the minute movements of Muscle in passive
                      and active contraction.
  In passive contraction.—It is perhaps impossible in the higher ani-
mals to observe the nature of the microscopic movements occurring
in muscle in  its  ordinary state or during its passive shortening; but,
in the lower  and smaller forms of life, this may sometimes be accom-
plished.   It may always appear doubtful, however, whether any con-
traction that may be here witnessed be entirely of the  passive kind,
and consequently the movements here noticed are not worthy of im-
plicit reliance.   But it is more easy, and quite as satisfactory, to bring
a muscle under inspection, which is still in situ and in equilibrium with
its antagonists: in such, contractile force is being still exerted, though
its full effects are prevented from  taking place.   This may be done in
various small animals : perhaps the tail of small fish, or of the tadpole
of the common frog, is the best adapted for the purpose.  In the latter,
deprived of its integument, we have obtained such a view, and  have
found the contraction to  be quite uniform throughout, the transverse
stripes being stationary and equidistant.   This is nothing more than
might have been expected  on a  priori grounds.   The contraction,
being the effect  of the passive exercise of the property shared equally
by all parts of the  tissue, would  be equal in equal masses; and, as
the elementary fibres are of precisely equal width and substance from
end to end, no part of them could  predominate in action as long as
only the equable stimulus coincident with their natural state of tension
were applied.   It may be concluded,  therefore, that passive contrac-
tion  is  attended by a movement absolutely uniform  throughout the
whole mass of an elementary fibre,  or of a muscle.
  In active contraction, the case is far otherwise, as may now be con-
sidered proved  by  a considerable body of evidence.
   It might be argued, prior to direct proof, that  active  contraction
must be partial,  at  least  at its commencement ; because  the  stimuli
which  occasion it cannot, in their very nature, he applied to every
particle of the fibre at one and the same instant of time.
  Certain features  of the phenomena witnessed under the microscope
in fragments removed from the body,  and contracting in water, have
                                   a   close  bearing on  the present
Fig. 49.
 Fragment of an elementary fibre (from the Eel)
partially contracted in water. Magnified300 dia-
meters.—a. Uncontracted  part. 6. Contracted
part, along the border of which the sarcolemma
is raised from the surface by the water that has
been absorbed, that has thereby caused the con-
traction, and by it has been expelled from the con-
tractile mass.
question.   It has been  already
said,  that such contractions are
uniformly partial; but  they pre-
sent two further varieties, either
remaining in the part where they
first occur, or leaving  it as they
advance to others in the neigh-
bourhood.   The accidental  cir-
cumstances under which the frag-
ments are  placed, explain these
varieties.   In  the  former case,
the ends of the fragments happen 
MUSCULAR ACTION.
171
to be freely movable, and are drawn towards each other, according to
the amount of contraction occurring in particular spots; and, as the
contractile force leaves these spots and engages others, the ends con-
tinue to approximate, the parts once contracted remaining so, because
there is no force to extend them.   Hence the contraction appears per-
manent.
   In  the latter case, certain  parts of the fibre (as its broken extre-
mities) are fixed more or less firmly, so  as to offer a resistance to the
contraction that takes  place ; this resistance enabling the contractile
force advancing to new parts to obliterate the traces of contraction in
the parts in which it is  subsiding, by stretching  them.   The  ends
usually become fixed  in consequence of their being the first to thicken
from  contraction, and  from their  thus receiving the pressure of the
lamina of mica or glass with which it is requisite to cover the object;
and they are the first  to contract, because irritated by being broken,
and by the  water, which is absorbed soonest where the sheath is de-
ficient.   This fixing of the ends  brings the fibres in question nearly
into the condition under which they exist in the  living body, where
it has already been explained that there is  always a resistance to be
overcome in active contraction.   This particular variety of the phe-
nomenon, therefore, deserves special  study.  Those animals whose
muscles  are most tenacious of their contractility are the best suited
for examination ; and, among these, the young crab or lobster may
be most  easily obtained.
   In  an  elementary fibre from the claw, laid out on glass, and then
covered  with  a wet lamina  of mica, the following phenomena  are
always to be observed.  The ends become first  contracted  and fixed.
Then contractions commence at isolated spots along the margin of the
fibre, which they cause to bulge.  At first they only engage a very
limited amount of the mass, spreading into its  interior equally in all
directions, and being marked by a close approximation of  the trans-
verse stripes.   These contractions pull upon the  remainder of the fibre
only in the direction of its length, so that along its edge the transverse
stripes in the intervals are  very much widened and distorted.  These
contractions are never stationary, but oscillate from end to end, relin-
quishing on. the one hand what they gain on the other.  When they
are numerous along the same margin, they interfere most irregularly
with  one another, dragging  one another as though striving for the
mastery,  the  larger  ones con-
tinually overcoming the smaller;
then subsiding as though spent,
stretched again by new spots of
contraction; and again, after  a
short period of repose, engaged
in their turn by some advancing
wave : this is the  first stage of
the phenomenon (fig. 50).  At
a subsequent stage, the  ends of
.1   /••           i         .   r     Border of an elementary fibre of a young Crab,
the fibre  Commonly Cease  tO be  showing a spot of contraction, and the sarcolemma
CmA  :^  „^„or>„..an«Q nf An in   elevated in the form of bulla; by the expressed
faxed, in  Consequence Ot the in-   water.-Magnified 300 diameters.
 
172
ORGANS OF LOCOMOTION.
termediate portions, by their  contraction receiving some of the pres-
sure of the cdass.   The contractions, therefore, increasing  in number
and extent, gradually engage the whole substance of the fibre, which
then is reduced to at least one-third of its original length.
  The muscular tissue in these animals is comparatively tough; but
where it is more  fragile, as  in the frog, it may give  way in the inter-
                          vals between spots of contraction, and be-
                          come ruptured and disorganized in various
                          degrees.  {Phil.  Trans.,  1840,  p. 490, pi.
                          xix. fig. 75.)  In fishes  we have  seen a
                          succession of phenomena similar to what
                          has been described in the crab  ; waves of
                          contraction advancing and  receding, but
                          gradually  augmenting  in  bulk, till the
                          whole fibre was finally contracted (fig. 51).
                             In all these examples, as long  as the
                          ends of the fragment are fixed, and will
                          not yield to the convellent force, that force
                          is seen to be exerted in a momentary man-
                          ner in  successive  portions of the mass.
                          In proportion as they yield to it, the  re-
                          sistance which enabled the contraction of
                          new parts to stretch  those from which it
                          was receding is removed, and the appear-
                          ances of contraction remain.   A distinc-
                          tion is required between  the  contractile
                          force and the contraction resulting from
                          its exercise.   The  latter will  be perma-
                          nent, if no force from without  be  exerted
to obliterate it by  stretching; for a contracted muscle has no power
of extending itself; there is  no repellent force between its molecules.
From these phenomena, therefore, it  is possible  to  eliminate  the
appearances resulting from a subsided force and to judge of the mode
and duration of action of the force itself.   Thus sifted,  they prove
that, even when directly stimulated by water after  removal from  the
body, a  muscle contracts in  successive portions, never in its  totality
at once ;  and that no particle of it is capable  of exhibiting an active
contraction for more than an instant of time.
   The appearances presented by muscle that has been ruptured by
its own inordinate  contraction in fatal tetanus, in the human subject,
will supply the link wanting to connect the foregoing phenomena with
those occurring in  healthy contraction during life:  for tetanic spasm
differs from  sustained voluntary contraction, only in its amount and
protracted duration, and in its being independent of the will;  none of
which circumstances are of essential importance in regard to the nature
of the act of contraction itself.
   The muscles are so  arranged in the  body, that no  amount of con-
traction  which  the mechanism of  the  bony and ligamentous frame-
work will permit one of them to undergo, can by possibility occasion
the rupture of an antagonist, provided it remain relaxed: to  be nip-
 Stages of contraction seen on one
occasion in an elementary fibre of
the Skate. The uppermost state is
that previous to the commencement
of active contraction.
 a. a. a.  Successive "waves" of
contraction seen moving along one
margin of the fibre, marked by a bulg-
ingof the margin, by an approxima-
tion of the transverse stripes, and by
a consequent darkening of the spots.
 b. b. b. Similar "waves" still mov-
ing along the fibre, but engaging its
whole thickness. 
MUSCULAR SOUND.
173
tured, the  antagonist must be itself contracted.  But a muscle, if
contracted  beyond its natural amount, maybe so resisted by mechani-
cal powers, in or  out of the body, as to rupture itself.  Hence, the
contraction of a muscle is  a  necessary condition, and generally the
essential cause of  its own rupture: the other condition being a force
greater  than  the  tenacity of  the  ruptured part, holding  its ends
asunder; which latter may be  either the active or passive contraction
of antagonists, or mere  mechanical resistance: but it is evident, that,
for a muscle to be ruptured by its own contraction, that contraction
must be partial, as is shown in the case of the frog's muscle, already
mentioned.
   An examination of muscle ruptured  in tetanus is found to bear out
these observations in the fullest manner.  {Phil.  Trans., 1841, p.  69.)
The elementary fibres  present numerous bulges of a fusiform shape,
in which tfce transverse stripes are very close together.   These swell-
ings, or contracted parts,  are separated from one another by intervals
of  various lengths, in which the fibre  has either entirely given way,
or is  more or  less stretched and disorganized.   These appearances
are met with after all contractility has departed ; they are the vestiges
of  the  spasm  during life.   Yet in  other  muscles, which  have been
likewise convulsed, but  not  ruptured, they  are  not  found.  Their
presence is, therefore, the result of the rupture.   They admit only of
the following explanation : the contractile force has operated at the
points found contracted, and,  by its excess, the  intermediate portions
have  been stretched  to laceration.   Having  once given way, the con-
tracted  parts  have become isolated, and can no  longer have been
extended after the subsidence of contractile force ; they consequently
retain the form and  appearances they possessed, when surprised, as
it were, by the rupture they have themselves produced of the inter-
vening  parts.
   Supposing,  for a moment, that active contraction  were an univer-
sal and equable act,  and that, by the superior power of an antagonist,
a weak muscle had been  ruptured, the appearances  resulting would
manifestly be  entirely different from those now detailed.  The fibres
beyond the ruptured point would have their transverse stripes uniformly
approximated.
   It may be concluded from  the preceding facts,—1st.  That active
contraction never  occurs in the entire  mass of a muscle at once,  nor
in the whole of any one elementary fibre, but is  always partial at any
one instant of time:—2d. That no  active  contraction of a muscle,
however  apparently prolonged, is  more than instantaneous in  any-
one of its parts or particles:—and therefore, 3d.   That the sustained
active  contraction of a muscle is an act compounded  of an infinite
number of partial  and  momentary contractions,  incessantly changing
their place, and engaging new  parts in succession ; for every portion
of the tissue must take its due share in the act.
   Two phenomena yet  remain to be mentioned, wThich, by admitting
of a satisfactory explanation on this view of the subject, give strong
testimony to its correctness.
   The first is the muscular sound, heard  on applying the ear  to a 
174
ORGANS OF LOCOMOTION.
muscle in action.   It resembles, according to  the apt simile of Dr.
Wollaston, {Phil.  Trans.,  1811,) the  distant rumbling of  carriage-
wheels ; or rather, perhaps, an exceedingly rapid and faint tremulous
vibration, which, when well  marked, has a metallic  tone.   It is the
sound of friction, and appears to be occasioned  by those movements
of the neighbouring fibres upon one another, with which the partial
contractions must be attended in their incessant  oscillations.
  The other phenomenon is one whose  existence has been recently
ascertained  by MM.  Becquerel and  Breschet, {Recherches  sur  la
Chaleur Animate.   Archiv.  du Museum, torn. i. p. 402,) viz., that a
muscle, during contraction, augments in temperature.  They have found
this increase to be usually more  than 1° Fahr.;  but sometimes, when
the exertion has been continued for five minutes, (as the biceps of
the arm, in sawing a piece of wood,) it has been double that amount.
This development of heat may be in a great measure attributable to,
and even  a necessary consequence of, the friction just alluded to.
  Thus it would appear, that in active contraction there is a disturb-
ance of the state of equilibrium,  or rest, by the application of a special
stimulus to  certain portions only of each fibre ;  by which first these
portions, then others in succession, are made to contract strongly, and
to pull on the extremities of the fibre through the medium of the parts
not so contracted.   The contractions  undulate  along the fibre from
the point  stimulated, and there  is always a  considerable part of each
fibre uncontracted.  This will account for  the remarkable fact, that
detached fragments of the voluntary fibre will contract by two-thirds
of their  length ; though an entire muscle, in  its natural situation, can-
not shorten by more than one-third.  This great capacity of contrac-
tion in  the  tissue  would be without a  purpose,  if it were not that it
only admits of momentary exertion, and therefore requires that in the
organ successive parts  should  take  up the act, and by so  doing,
render it,  as a whole, continuous.   In an active fibre the contracting
parts are continually dragging on those in which the  contractile force
has just subsided, and which intervene between them and the extre-
mities of the fibre.   These are thereby instantly stretched, and come
to serve the temporary purpose of a tendon ; but one which resists
extension more by its passive contractility than  by its mere tenacity.
It is these parts  which in tetanic spasm suffer laceration ; which hap-
pens in consequence of the contraction  excited  by  the  vis nervosa
being then too powerful to be resisted by the passive  contractility.
  The preceding  account  of the  minute changes occurring  during
contraction  rests on data furnished by the  striped form of  muscular
fibre ; but there is  nothing  contained  in it which seems at variance
with the little that is positively known regarding the contractions of
the other form.  The differences between the contractions of the two
varieties are almost certainly confined to the manner of exercise, and
do  not  extend to  the essential  nature of the act.   Though the un-
striped fibre has not been studied by the microscope, during its active
state, with the same success as the other, yet  the  similarity of the
gross changes observed in it by the naked eye, to those seen in volun- 
VARIETIES OF CONTRACTION.
175
tary muscle, forbids us to doubt the identity of the phenomenon in all
that is essential to it as an act of contraction.
  From the knowledge we possess, we are perhaps entitled to hazard
some  further conjectures  respecting the differences in the mode  of
exercise  of the contractile power in  different  cases.  In whatever
that mysterious power may consist, it  would  appear that  the structu-
ral modifications  of the two  kinds of  fibres are  intimately connected
with the manner  in which it  is capable of being exerted.   Wherever
the striated  structure  occurs,  we witness  an  aptitude  for quick,
energetic,  and rapidly repeated  movements ; while, where it is defi-
cient,  they are sluggish, progressive, and more sustained.
   The varieties in the character of contractions  performed by striated
muscles  are  very striking, especially that of the heart, as compared
with the prolonged action of the voluntary muscles.   In  both, there
is an  alternate  momentary  action and repose of every contractile
particle : but  in the  heart the contraction is  universal at  one instant,
and the repose equally universal at the next; while, in the prolonged
action of the  voluntary muscles, contractions of certain parts of each
fibre always co-exist  with repose of other parts.*
   The contractions of voluntary muscles differ greatly from one another
induration, energy, and extent.  Dr. Wollaston {Philos. Trans., 1811),
was of opinion, that the phenomenon of the muscular sound affords a
proof that the duration of a muscle's contraction  depends on the appli-
cation to it of a succession of distinct impulses; and this idea, accord-
ing very nearly, as it does,  with the  later evidence of observation,
appears, on the whole, the most satisfactory that  has been advanced
on this abstruse subject.   He also thought that the intensity of a con-
traction corresponds with the rapidity  with which these impulses are
transmitted to it; and this likewise may be,  in part, true.  But there
is, in addition to this, in  all  probability, a difference in the intensity
of the stimulus itself in different cases, producing a difference in the
size of each wave, a difference in the amount of contractile energy
exerted in  each, and a difference in the rapidity with which the waves
oscillate along the fibre.   The extent of the contraction (the  duration
and intensity  being the same) will manifestly depend  on the amount
of the length of  the  fibre which is  contracted  at once ;  but we are
ignorant whether this variation  in amount is effected  by  a variety  in
the number of waves, or in  the extent of  the fibre engaged  by each
of them.
   In  describing  the  white fibrous tissue, we remarked  the facility
with which its fibres  are  thrown into  a wavy or zigzag course when
their  ends  are brought near together.   The same thing occurs in the
nerves, and may  be observed in almost any flexible non-elastic cord.
The muscular fibre easily assumes this zigzag course, when its ends
are approximated by any other force  than its own contractility.   It
may thus be  at  any  time thrown into zigzag, long after it  is  quite
dead, and  has lost all its  contractility: and,  in general, such zigzags

  * By the expression "universal at  one instant," we do not mean absolutely so;
for observation, and the presence of the  muscular sound, both declare that the contrac-
tion, even of the heart, though so apparently momentary, is progressive. 
176
ORGANS OF LOCOMOTION.
occur at pretty regular intervals, determined by the force employed
and the flexibility of the tissue; and, when several fibres are lying in
contact, their zigzags usually correspond.
   Now, such zigzags have been frequently observed in the living
fibre, of course accompanied with  an  approximation of its extremi-
ties; and some physiologists, mistaking the effect for the cause, have
concluded the zigzags to have occasioned the shortening.   Dr. Hales,
and, long after him, Prevost and Dumas, examined this  appearance
in  the flat  abdominal muscle of a frog, laid  on glass, and made to
contract by a galvanic  shock;  and, noticing that the angles of the
zigzags corresponded in many places with the transit of nerves across
the fibres, they concluded that an electrical current, passing from  one
to the other,  occasioned the flexion of  the  fibres at the  points of
contact.
   This hypothesis, when first proposed, attracted great regard, from
its  appearance of simplicity, and from its falling  in  with  the then
favorite notion of the  identity of the  nervous influence  with some
form of electricity ; and without sufficient caution it was very generally
adopted.  The facts  previously stated,  however,  completely over-
throw it, and render an  explanation of the causes of the error scarcely
more than historically interesting.   It would appear that the galvanic
shock, when passed through a mass of fibres,  affects them unequally,
some only being  contracted by it: but these, by their cellular  and
vascular union with others, draw towards each other the ends of the
uncontracted ones, and, of course, throw them into zigzag; and it is
most natural that  the passage of nerves or vessels across thern should
determine the flexures to take  place at this or that particular point.
When  some fibres are straight and others zigzag, and yet the ends of
all equidistant, it  is clear that the straight ones are the short or con-
tracted ; the zigzag, the long or relaxed.  So, also,  when a living
muscle is laid bare in situ, the air excites tremors and a zigzag appear-
ance on its surface, by the different  fibres taking on non-simultaneous
contractions.
   Schwann {Mailer's  Physiology,  by  Baly,  p.  905), contrived an
apparatus by which he could estimate the varying force of contraction
which a muscle could evince under the  same stimulus,  (an electric
shock of a given  power applied to the  nerve,) when  its  length was
varied, by its passive contractility being balanced by different weights.
He sought to discover whether  the  contractile force was increased as
the contracting parts approached each other more nearly.   If  he  had
found it so augmented,  there would have been some reason for con-
necting contractility with the other forces of attraction with which we
are acquainted, the power of which  increases with the nearness of the
points attracted, in the ratio of the  square of the distance.  But  the
results of several ingenious experiments were quite opposed  to  this
notion;  proving that, within certain limits, the power of a muscle to
contract under a  stimulus is greater in proportion as it is  less con-
tracted, and that it diminishes as the  amount of  contraction in-
creases.
   Considering, as we are perhaps entitled to do, that an equal mass 
CONTRACTILITY OF MUSCLE.
177
of each fibre, say one-third, wras in contraction at anyone instant by
each application of the stimulus, we  may reduce the result of these
experiments to an  estimate of the passive  contractile  power  under
different amounts of stretching; for then the  varying amount of aggre-
gate shortening under the same stimulus would  indicate the varying
amount of resistance to elongation afforded  by the intermediate  two-
thirds to the  same amount of active contractile force in the one-third.
   It is clear, from that which precedes, that  contractility is a property
residing in the sarcous tissue by virtue of its chemical  constitution,
and that it is capable of being called into action by other stimuli be-
sides the nervous.   That it departs  with life, is a proof that those
actions of waste and nutrition, concomitant with the flux of life, are
essential for its integrity.   We know that contractility is exhausted
both by disuse of a muscle, and  by  over-use consequent  on  over-
stimulation ;  and in no other  way can these opposite causes act than
by their both interfering with  healthy nutrition.   That  they do thus
act, is rendered probable by other proofs.   It has  long been known
that cutting off the  supply of  blood  from a muscle destroys its con-
tractility ; that unnatural  temperature has  the  same effect; and, in
general, that all  causes affecting nutrition affect also contractility in
the same degree.
   The contractility of a  muscle has also invariably a certain  com-
plexion or character connected, we might almost say, with the vigor,
but at least with  the character, of the nutrient process in the particu-
lar muscle.  This fact has been ably illustrated by Dr. Marshall Hall,
(see article " Irritability," Cyclop, of Anat. and Phys.,) who never-
theless is opposed to the  great conclusion which we consider to flow
from it, that contractility is proportioned to the activity and perfection
of the  nutrient function.
   If we suddenly check the  supply of nutrient  material to  the  mus-
cles of  various animals, in the same state as regards previous stimu-
lation, and in such  a manner  as not  to stimulate  the muscles  in so
doing,  we shall  find  that their contractility,  as  evidenced by  their
contracting under a  given  stimulus, endures through very unequal
periods of time.   Thus,  in the  bird  it  is  very  evanescent; in the
insect, also, it  is very evanescent; in the  mammal  less so; in the
reptile it lingers longer; while in the  fish and crustacean it is in gene-
ral very enduring.
   The degree in  which oxygen is admitted to  the tissues in these ani-
mals, corresponds in the main with the scale thus designated by the
relative endurance of the contractility of their muscles.   Nothing is
more probable than  that the amount  of oxygen  admitted to the tis-
sues may be  taken as a fair estimate of the activity in  them of the
processes of waste and assimilation.   Now, we know  that the vitality
of the tissues does not cease immediately on their supply of nutriment
being cut off"; that death of the whole animal, as an individual, is not
necessarily attended with  simultaneous death of every part; that so-
matic death generally follows systemic death from the  functions being
no  longer  concatenated in  mutual dependence ;  and it is entirely
consonant with facts to suppose that the endurance  of the vital func-
tions in the tissues after systemic death is proportionate  to the slow- 
178
ORGANS OF LOCOMOTION.
ness with which they are ordinarily performed.   The close corre-
spondence, therefore, between the  duration of contractility and  the
slowness of the nutrient function in  various animals, is a strong evi-
dence of the dependence  of  the one on the other.
  And it is extremely interesting to  observe, that not only does a less
arterial character of the blood co-exist with a more enduring contrac-
tility, but also that there is less of it supplied to the muscles, for  the
above scale corresponds also with that  in which  animals are ranged
in regard to the size  of the  elementary fibres; and we have already
seen that the vascularity of a muscle is inversely  as the thickness of
its fibres.
  Thus we have animals ranged in the same series, whether we esti-
mate it by the duration of contractility, the degree of the  oxygena-
tion of the blood and tissues, or the quantity of blood sent to  the
muscles, viz., birds, insects,  mammalia, reptiles,  fish, and  Crustacea.
The meaning of this correspondence maybe further illustrated by the
phenomena  of hybernation, in which all  the  functions are  held  en-
chained, and we are certain that nutrition  proceeds with extreme lan-
guor.   In the  hybernating animal,  contractility is very enduring, as
compared with that property  in the very same organs when in a state
of greater vital activity.
  Nor must the evident relation  subsisting between fibrine and  the
sarcous tissue, in respect of their vital properties, be passed over in
silence.  In chemical constitution they may be said to be identical;
and there seems no doubt that muscle is formed by the direct deposi-
tion in a solid form of the  fluid fibrine of the blood, under the elective
attraction of the previously existing tissue. Now,  in birds, the blood,
i. e., its fibrine, coagulates, or assumes the solid  form, very quickly
when it is withdrawn from the vessels, in mammalia less so, and in
reptiles and fishes very tardily, if in these several cases it be placed
in similar circumstances.  A  fatal stroke of lightning, which  instanta-
neously destroys contractility in the  muscles, prevents also the coagu-
lation of the blood.   In  the  same person, under health and disease,
the  blood  may vary much in the speed   with which  it coagulates,
according to its  chemical constitution, the amount of oxygen accu-
mulated in it, and the activity of the vital  processes: and, after death,
the  coagulability of the blood, and  the contractility of the  muscles,
have a general correspondence, which has been even made the basis
of an hypothesis, ascribing the rigor mortis, or the dying act of contrac-
tion, to coagulation of the blood.*   It will be subsequently explained
(see chapter on the Blood), that the fibrine of the blood, on becoming
solid, acquires  for a brief period  the  property of contractility; and
this in  very different degrees,  according to varieties in  the same
causes which affect the speed of its coagulation.  No one  will pre-
tend that this is not as much  a  property of living  fibrine when solid,
as that of coagulating is of the same substance when fluid; and  the
correspondence between the coagulated living fibrine of the blood and
the living sarcous tissues in  chemical constitution, in the  possession
  »  Orfila, Beclard, and Treviranus hold this view, which Muller seems to regard as
cot untenable. 
VARIETIES OF MUSCULAR MOVEMENT.
179
of contractility, and in the modes in which that vital property in both
is affected by similar causes, adds strong confirmation to the opinion
we have expressed, that contractility is a property of the living mus-
cular substance as such.
  But contractility does not vary in its durability alone; it also pre-
sents great differences in regard to its  aptness to excitation by stimuli:
and  it would appear that these characters are always, cateris paribus,
in an inverse  relation to one another.  In birds  and insects, which
have for the most part  to sustain themselves by very energetic and
rapid muscular  movements  in the air, the excitability is extreme ;
and  certainly the motions performed by these creatures far exceed in
precision, regularity, and frequency those of any other animals.
  The rigor mortis, or  stiffening  of the body after death,  is due to a
contraction  of the muscles.   If the contractility of a muscle be endur-
ing, the rigor comes on late" and lasts long; but if it be evanescent
and  its character excitable, the  rigor  begins very soon and quickly
terminates.  This is true in different individuals and classes of animals,
and  corresponds entirely with what we have already said of the varie-
ties  of this property.  Its cause is obscure, and maybe complex; but
its resemblance to the contraction of  fibrine  after recent coagulation
is too obvious to be overlooked. Its nature is shown by the preceding
observations (p. 170).
   We have the  power, at will, under certain limitations,  of produc-
ing, checking, and regulating the amount of contraction in the volun-
tary muscles; and, as a necessary part of  this power, we  are able to
appreciate,  by certain sensations originating in the muscles, what pre-
cise degree of contraction is present in each.  This latter is only that
modification of common sensibility which belongs to muscle.  It has
been termed the muscular sense.  In it we possess a most important
aid  to the sense of touch, being able accurately to vary the posi-
tion  and amount of pressure  on external objects in voluntary accord-
ance with the impressions these communicate to the sensorium through
the tactile nerves; and by it we  are able to  estimate with  nicety the
amount of muscular power required to balance various resistances,  as
weight, &c.   In general, these resistances  must be brought into rela-
tion  with the  muscular sense through the organ of touch, which  is
adapted to this purpose by its superficial position  on the body.  But
the powers of the  muscular  sense,  isolated from  tact, are   exhibited,
in its enabling one to estimate the weight  of a tumour developed  in
the interior  of the limb, and  in general the  resistance  afforded by the
weight of one part of the body, or the action of one muscle or set of
muscles to that of another.   Hence a  principal source of the marvel-
lous power which  all  animals possess  of associating the various parts
of their bodies in numberless combinations of harmonious movement.
   Of some varieties of muscular movement.—Having described the
differences  between the movements of active  and passive contrac-
tion, we shall now be more  able to refer to their  proper causes those
varieties of movement by which  certain muscles or classes of mus-
cles  are distinguished.  In briefly adverting to these, we  shall have
to glance at some collateral considerations regarding the mode of their 
180
ORGANS OF LOCOMOTION.
connection with the nervous system, which  cannot be fully  under-
stood without reference to what will be afterwards said  under that
head.
  The action of the sphincters of the anus and bladder seems, at first,
peculiar.  They are constantly contracted, except during the passage
of the contents ; and yet no fatigue attends this persistent action.  The
explanation is very simple.  They remain contracted unless the con-
tained matters are forced within them by a superior power.   Now,
their mass, and therefore their contractility, is superior to that of the
wall of the cavity above ; consequently their  passive contraction en-
dures while that of the  parts above  is being gradually mastered by
the accumulation of the feces or urine.   But, when these excretions
at length excite active contraction in the walls of the cavity contain-
ing them, this overcomes the  passive contraction of the  sphincters,
and the evacuation occurs.  The  sphincters  have striped fibres and
voluntary nerves, by means of which we can  for a time add  active to
passive contraction, and thus retard the expulsion ;  but, as the accu-
mulation proceeds, this  power is diminished  or lost, and the sphinc-
ters yield.   The levator and sphincter ani frequently aid the accumu-
lation of the feces by temporary  active  contractions,  by which the
feces tending to dilate the sphincter are pushed backwards for a while.
The rectum is thus preserved empty until the  period immediately pre-
ceding defecation.
  In paralysis of the lower part of  the body from disease  or injury
of the spine, the voluntary power of the sphincters is  lost, and the
feces and urine pass involuntarily.  But this  is no  proof, as is com-
monly imagined,  that the ordinary  contraction of the sphincter is
an active one, performed in obedience to a continuous nervous stimu-
lus.   The difference is, that it can  now induce no active contrac-
tion through the nerves, to counteract temporarily, and  in obedience
to the will, the active contractions of the parts above, which are not
under the influence of volition, and are not paralyzed.  Hence, when-
ever the feces are driven against it, it gives way, against the patient's
will, and (if the  sensitive  nerves are  also  paralyzed), without his
knowledge.
  Contractions are called  peristaltic  or vermicular, which  advance
through a muscle in a slow and progressive manner. When  analyzed
closely, we shall find that they are only a variety of the active con-
traction already described.  If a number of striped fibres are  arranged
in a long series, and are contracted in succession (as in caterpillars),
the resulting movement is vermicular;  but in the  higher animals it
is only in the hollow unstriped muscles that this variety of contraction
occurs ; and the best example  of it is in the  alimentary canal.   On
laying bare the intestines of an animal  just killed, we  observe suc-
cessive waves of contraction advancing down the  tube, and  urging
its contents along.   They appear to be rendered more active  by the
contact of the cold air ; but may be re-excited, when they have almost
subsided, by irritation of  the  sympathetic ganglia, from which the
muscles are supplied with nerves.   If a single point of the intestine
be touched, a contraction  presently occurs there, which moves on- 
VARIETIES OF MUSCULAR MOVEMENT.
181
wards to a considerable distance, and is often  succeeded by others
spontaneously arising.
   It is impossible not to remark the  close similitude between these
contractions and those visible by the microscope in the striped ele-
mentary fibre.  We have here on a  large scale the wave-like charac-
ter there exhibited.  A contracting voluntary muscle exposed to view
exhibits a tremulous  motion, and it may be a question how far this
may depend  on numerous  contractions  strictly vermicular, affecting
successive sets of fibres, but prevented, by their irregularity and
want of coincidence through the  whole muscle,  from appearing so to
the eye.  When the pectoral muscle is struck, a knot-like contraction
often moves off in a slow manner in the  direction of the fibres. Peri-
staltic  contraction is  coincident  in a large number  of contiguous
fibres; and its progressive character is more easily perceived in con-
sequence of the arrangement of the fibres around a compressible cav-
ity.   The contraction appears  more sluggish than  other forms; but,
as we are ignorant of  the length of  each unstriped fibre, we  cannot
say whether this slowness is in advance along  each one, or  merely
from one to another.
   The contraction exhibited by the  muscles in  question is always of
the peristaltic character, by  whatever stimulus excited; and its type
is therefore probably derived from some peculiarity in the fibres them-
selves, as in their arrangement.  But it is remarkable that the  stimuli
which usually excite it, are  applied  in succession to  different parts,
and are thus entirely suited  to  the production of the peristaltic con-
traction.  We  have  a striking example of this  in the oesophagus,
which is simply a  tube of transmission, and not intended to delay the
food.   The pellet, when thrust into it by the muscles of the pharynx,
distends its fibres, which, then  contracting  upon  it, propel it into  a
fresh portion ready to receive it.  This in its turn contracts, and urges
it  along;  and so on, until it  is conducted to the stomach.
   In this instance, it is evident that  the propelled substance is itself
the stimulus to the successive  contractions.   This it  may be, either
by distending the fibres, and so acting locally upon them;  or else by
impressing the  nerves of the membrane touched, in such a way as to
excite a nervous stimulus to the muscular coat at each particular part,
at the  proper moment.   As the  food  is not propelled if the  nerves
are divided, there  can be little  doubt that the latter is the  true expla-
nation.
   The contraction of the  bladder occurs after a gradual distension,
and, though very temporary, is probably of the  true peristaltic kind.
The more protracted action of the uterus is undeniably so.   In preg-
nant animals this may be as  distinctly perceived as in the intestines,
and it  probably occurs during the gradual development of the muscu-
lar structure as pregnancy advances  ; but at length a very powerful
impulse occasions  the expulsion of the young, and the uterus  subse-
quently remains contracted,  because  no force distends its fibres.  The
after-pains mark the final efforts of active contraction.   Atrophy of
the tissue then occurs, as its  development had done, in accordance
with other laws. 
182
ORGANS OF LOCOMOTION.
  Rhythmical contractions are those which succeed one another after
regular intervals of repose.   The muscles of respiration and the heart
exhibit them through life, which would cease if they were intermitted
even for  a brief period ; for the  oxygenation of the blood, and the
dispersion of that fluid through the substance of the various organs,
must incessantly proceed.   Hence neither is an act of the will re-
quired for their production, nor could it under any circumstances pre-
vent them.   The heart beats independently of our consciousness or
control;  but the respiratory  actions may be hastened, or retarded, at
will, though not  stopped.   This voluntary power  is given because
these muscles are required in various movements of the  body,  either
alone, or in aid of others; they minister to  other  functions besides
that of respiration.  The voluntary, or irregular action, however, is
entirely subordinate to the involuntary and rhythmical.
  The rhythmical character of the respiratory act is to be explained by
reference to the stimulus by  which it is ordinarily excited. This is an
impression made  on the  internal surface of the  lungs by the deterio-
rated air, and  recurs  periodically from the change induced in the
inspired  air by its contact with the blood in the  air-cells.
  Though the heart  is in no respect under voluntary influence, yet
emotional and instinctive impulses easily affect it: its action is throb-
bing, tumultuous, or feeble.  These impulses act through the cardiac
nerves, which, if stimulated mechanically, will excite contractions in
a heart removed from the body, and which has almost ceased to beat:
but, under  all  circumstances, the action  of the heart is rhythmical.
The cause of the rhythm it is ^exceedingly difficult  to resolve.   This
variety of  contraction  is coincident with   periodic  distension of the
cavities, and impressions on their lining membrane.  But it continues
long after the heart is  empty, and its nerves cut.  Hence,  whatever
share these circumstances may have in giving the rhythmical character
in the natural condition of the parts, they  are certainly  not essential
to each individual pulse.  It is singular that a mechanical  stimulus
applied once to the heart will often excite a series of contractions
after they had ceased, or modify the rhythm of those previously exist-
ing; its  effects being thus prolonged  through many beats.
   In reviewing the actions  of the voluntary muscles we may remark
the following interesting circumstances :
   1. As to  association of movements.—By the  mechanical  arrange-
ments of the muscles  on the bony framework, and  by the peculiarity
of  their  several nervous connections, they are  rendered capable of
conspiring in those combined actions which produce the various atti-
tudes and  general movements of the body.  There are few muscular
actions,  indeed, of an entirely solitary kind.   In the animation of the
features under  the passions, in articulation, in deglutition, in respira-
tion, and in numberless other cases, we have examples of this asso-
 ciation of many actions to  the production of one effect.   Even the
 consent  of the fibres of a single  muscle  in contraction  is an instance
 of this fact.  Among innumerable other proofs of harmonious design
 in  the construction of the  animal body, this might be singled out as
 a most convincing one, that  not only are the hard levers, and their 
ASSOCIATION OF MOVEMENTS.
183
joints and motive engines, so built up as to be entirely proportioned
and adapted to  one another  in  shape, strength, and position, and a
system of nervous  communications  established, by which  the motor
power can be at once excited, prolonged, or controlled in any particu-
lar muscle ; but that the mere will, an emotion, an excitement of sense,
or even  one unconsciously received, is able, by the correspondence
existing between  the different  parts of the  nervous system, to pro-
duce associated actions in precisely those parts mechanically adapted
to move in  concert, and this with exquisite exactitude as well as va-
riety.
   Such is the nature of the nervous communications between certain
muscles, that,  in numerous  instances, one cannot  be stimulated  to
contraction  without others contracting of necessity  at the same time.
This depends very generally on the mechanical disposition of mus-
cles, obliging certain of them to fix a point from which others  may
act.  Thus the scapula is continually being  fixed by the muscles
connecting  it with the trunk, in order that the arm may be wielded
upon it.  Thus, also, the brow cannot  be elevated by the frontalis
without the occipitalis fixing the intermediate tendon.   But, in other
instances, this  necessary consent is dependent on  the  symmetrical
arrangement of similar  parts on  the  two sides of the body.  Some
persons cannot close one eye, keeping the other open ; or dilate one
nostril without the  other: we cannot look up  with one eye,  and down
with the other; nor compress the abdominal cavity  by the muscles of
one side without those of the other. There is, indeed, a general tend-
ency to  symmetrical movement,  which it is the  part  of  education
and habit to overcome within certain limits.   The movements of the
hands—those wonderfully versatile instruments of man's intellect—
are, in his state of infancy, generally symmetrical.   The unsymme-
trical actions of walking are a slow acquisition.  Most motions that
are symmetrical are also harmonious ;  but  there is  one example  in
which symmetry gives way to  harmony of movement, viz., in the
lateral motions of the eyes, where  symmetry would produce a squint,
and derange the consent of the images  on the two retina?.  Here,
therefore, by the distribution of  the nerves, non-symmetrical muscles
are made to produce a harmonious movement.
   The various attitudes of man may  here be briefly  explained. Mus-
cular actions associated to  produce an attitude are styled co-ordinate.
They conspire in obedience to the particular organization of the nerv-
ous and muscular  systems ;  and the  resulting postures are natural,
and perfectly accordant  with the  wants  and  habits of the species.
Most attitudes, if perfectly natural, are graceful, just as  external fig-
ure is graceful ; unnatural  attitudes are more  or less constrained,  or
awkward.   The co-ordinate, like other movements  of the  voluntary-
muscles, are liable  to be influenced by passions and affections of the
mind.   Hence the internal commotions of the soul betray themselves
in the attitudes of the body as surely as in the lineaments of the coun-
tenance.
  In considering the different attitudes, it  is to be remembered  that
the human body is not withdrawn, either by its organization or  vital 
184
ORGANS OF LOCOMOTION.
endowments, from the operation of  the general laws of matter ; and,
accordingly, that the muscular actions occurring within it are all adapt-
ed  to act upon its several parts, as upon  masses of certain  shapes,
sizes and weights.  In  all attitudes the centre of gravity must be
maintained within the base of support.
  In standing, the base of support is the space included between the
extreme  points of  the feet.   The  feet are separated, and the  toes
turned outwards to  increase it.  If the body be pushed aside, the foot
is instantly carried under it, or it falls ; and if motion be unexpectedly
given to  the feet, while the body remains at rest by its  inertia, (as
when a boat in which we are standing is suddenly shoved off from the
shore,) the body falls.   In standing  upright, both  legs are kept ex-
tended, and the spine and head erect:  if the muscles that effect this
be suddenly paralyzed, as when a man is shot dead, the head  droops
on  the chest, the curves of the spine  are increased by the pressure
of the  superincumbent weight, and  the whole  trunk approaches the
ground by bending the joints that were before extended.
  The muscular action required to maintain the erect posture  of the
body is very great.  This is shown by the fatigue that ensues on an
attempt to remain perfectly still in the erect posture, even for a very
short time.  In fact, though we can stand long at  a time, it  is only
by frequently relieving one set of muscles, and bringing another  into
play, as every one may convince himself by attention to his own case.
We throw the weight of the body first on  one leg, then on the other;
we change the position of the feet, and of the ankle, knee, and hip
joints, as well as of the rest of the body.
  Under all these movements, the centre  of gravity has  to be kept
within the basis  of support;  and, to effect  this object, the different
muscular actions on which the erect  posture  depends must be ex-
quisitely  balanced against one another, and, when one is altered, the
rest must be re-adjusted in harmony wTith it.   In the practised tum-
bler, balancing himself on a  point, or the opera-dancer,  poised on a
single toe, we have the most  beautiful examples of the precision of
this adjusting power.  Where the basis of support is ampler, it is less
apparent, but not less real.
  The various  parts of the  body are weights, and, in the muscular
adjustments,  are  treated as such.   By their  symmetrical develop-
ment on  the two sides, they are  naturally balanced, and thereby car-
ried with less muscular  effort.  When two equal  artificial weights
are fixed on opposite sides of the body, equidistant from the centre of
gravity, (as when buckets are  suspended from  a bar passing across
the shoulders,) the  mere weight is all that the muscles have  to sup-
port: but, if one be removed, a corresponding inclination of the body
must instantly be made towards that side to counterpoise the  other;
and for this a sustained muscular effort must be made in addition to
that required for the support of the  remaining weight.  Now, a  part
of the body on one  side (say, an arm), by being carried from the cen-
tre  of gravity, may disturb the equilibrium of weight, just as moving
the weight on a scale-beam disturbs it: that side of the body becomes
relatively heavier, and an inclination towards the opposite is rendered 
MOVEMENTS OF PROGRESSION.
185
necessary.   In all  the changes of attitudes,  similar adjustments  are
being constantly made; and, in general, the more accurately they are
effected, and the more economically in regard to the outlay of mus-
cular power, the more graceful and pleasing are the movements and
postures themselves.
   In the associated movements of progression, or locomotion, the same
circumstances are observed:  walking, running, and leaping  are  but
different modes  in which the body is repeatedly inclined by muscular
effort beyond the basis of support; and this  basis brought again and
again, by muscular effort, under the centre of gravity.
   The  movements of ordinary walking  may  be  readily analyzed.
Suppose we commence by advancing the  left leg.   We first slightly
raise the left heel, and bend the left knee, to disengage the limb from
the ground ; throwing the weight of the body on the right limb, and,
therefore, inclining the body towards the right side.   The body is
now  raised by an extension of  the right  ankle-joint, effected  chiefly
by the calf; the ball  of the foot resting on the ground, which serves
as a fulcrum.   At the same  time the  body is thrown  in  advance of
this  fulcrum, and would fall, were it not that  the left  leg is now
brought under it, and receives  its weight, by which the body is in
turn  inclined to the left.   The  right  leg, which had been extended,
is then  bent, raised  from the ground, and swung forwards,  ready
again to  sustain and project the body, when the left  leg has gone
through a similar movement.   In running, the  muscular actions  are
performed in a similar succession, but more  rapidly and more vigor-
ously.  The body is more bent forwards, and its weight made more
effectually to aid progression.   In leaping, the body is projected by a
sudden  extension of both the lower limbs, and raised, for a brief
time, entirely from the ground, the feet being advanced again in time
to receive its weight as it descends.
   2. As to the manner in which movements  of the voluntary muscles are
excited.—These muscles are subject, through the motor nerves, to
the influence of several remote stimuli, already enumerated, and  the
chief of which, volition, gives its name to the class.  These stimuli,
in the healthy body, impress  the motor  nerve in the nervous centre,
and the effect is a contraction of the muscle.   By an exertion of the
will we can contract more or fewer  muscles  at once, and to  any de-
gree, within certain limits: we can contract  antagonist  muscles toge-
ther, or alternately, and through a longer or  shorter period.
   But  every voluntary muscle is subject to other influences more
certain and more powerful in their  operation than the will, and to
which the will has often  to yield.  The wonderful and characteristic
movements of the  body, and  especially  of the features  under the
impulses of passions  and emotions, are all involuntary, of which the
best proof is to  be found  in the very partial power the  will has of
restraining them.  To imitate the movements of passion is a task of
extreme difficulty ; and those actors succeed the best who lose them-
selves the most  in their characters, that is, who the most completely
assume for the  time  the passion they design to portray.   Without
this  quality the most elaborate imitation is cold, and fails to touch our
     13 
186                 ORGANS OF LOCOMOTION.
sympathies. The genius of the histrionic artist consists chiefly in this
power.
  Many movements ensue involuntarily when certain impressions are
made on the surface of the body, or in any part of its interior, either
by external or internal causes.  Such impressions are usually attended
with consciousness, but sometimes not; so that there  is no reason to
believe that perception of the impression is in any way essential to
the production of the  movement.  All  such movements are  termed
reflex.   The contraction of the esophagus in swallowing is an exam-
ple of them without consciousness.  The sudden inspiration that fol-
lows a dash of cold water on  the skin, and the  writhings  produced
by tickling, are instances attended with  consciousness.  All muscular
actions consequent on pain, and which are not the  immediate act of
the will, are similar in kind, though the stimulus producing them is
unnatural.
  Reflected movements are sometimes called instinctive; but this term
is better limited to actions resulting from a propensity in the mind, of
the meaning of which we are  ignorant,  but which we follow  blindly
without reference to consequences.  Such propensities are developed in
animals much more than in man ;  and in man more during his  infancy
than in his mature state, when reason  asserts her  domination over in-
stinct. Instinct exhibits foresight; but it is the foresight of the Creator,
and not of the creature.  It is the reason of God working with the mate-
rial instruments of the creature's reason, independently of the crea-
ture's will.  Hence the  movements consequent on its impulses have
all the concatenation and character of movements impelled  by reason
through the will; while they are altogether independent of the will.
Instinctive movements approach  the most nearly to voluntary ones.
  Thus  passion, emotion, reflected stimulation,  and instinctive  im-
pulses will all excite  involuntary movements  of the voluntary mus-
cles ; but,  in the natural state  of the body, all these causes are found
acting in harmony with one another, often conspiring to produce the
same movement.   The power  of the will to control them is but slight,
and in some cases null.   It differs with  the original strength  of  that
faculty,  with the temperament of the  individual, and especially with
the degree in which it has been affected by habit. The power of this
law is in  nothing  more conspicuous  than in its influence over the
human will.  A frequent  and energetic repetition of voluntary  acts
of control  over the involuntary movements of passion, emotion, and
instinct, is invariably  followed by an increased power  of control, and
vice versa.   This also extends (but in a less degree) to those move-
ments of voluntary muscles, consequent on reflex stimulation, which
are not essential to life.
  When movements,  which have been at first voluntary, come to be
performed  more or less unconsciously, they are styled mechanical. A
thousand instances of  them might be given ; all voluntary ones  becom-
ing more or less  so by habit.   The  nervous paths through which the
mandates of the will pass  to the muscles  grow more  accessible and
open by  use ;  and less and less effort  of volition becomes  necessary
to  thread them, every  time that effort is made.   In the  early  periods 
INNERVATION.
187
of life the will is exercised in tutoring  its corporeal  instruments to
give prompt and  ready obedience to its commands; every day new
lessons are acquired, and old ones confirmed ;  and, having at length
a practised body at its beck, it is able to execute numerous and com-
plicated movements with as much precision as those of the most deli-
cate and subtile  kind, and all, or any of them, without  being  itself
distracted with the business of their  immediate supervision.  Like
the general of a disciplined army, the will issues mandates of action
or control;  but is not cognizant, without a special effort of attention,
of anything beyond the general result of the various movements that
its orders produce.   And the body, that executes them, is constantly
performing other movements, of a routine  nature, connected  with its
safety, comforts, or ordinary functions ; which, though at first they had
demanded the general's attention,  and might again attract it, yet hav-
ing been learnt by drilling, are now executed without his anxiety or
even co-operation.  They are the working of a practised organiza-
tion.   Thus many particular movements are included in general ones,
without the will having the smallest immediate share in their  produc-
tion.  The countenance takes its expression from the prevailing action
of its muscles, often in spite of our efforts to the contrary;  and, in
general, the attitude and bearing wear a corresponding character. And
thus several general movements, which naturally (or by an act of the
untutored  will) are impossible  because incompatible, are rendered
capable of being simultaneously performed.

  The following  works may be consulted in  reference to Muscle and Muscular Ac-
tion:—Prochaska, de carne musculari; 1778: Fontana,  sur le venin de la vipere;
1781:  John Hunter's Croonian Lectures, works by Palmer, vol. iv.; Blane, on Mus-
cular Motion, in his select dissertations; the various works on General  Anatomy
quoted in former chapters; Barclay on  Muscular Motion; Mayo's Physiology;  Miil-
ler's Physiology, by Baly; the Articles Muscle and Muscular Action, in the Cyclop.
Anat. and Phys.  For greater details on the  Motions and Attitudes of the body than
would be consistent with the plan of this work, we refer to the Article Motion in the
Cyclop. Anat. and Phys.; and to Weber's Mechanik der Menschlichen. Gehewerk-
zeuge.
                         CHAPTER VIII.

INNERVATION.—EXAMPLES OF NERVOUS ACTIONS.—NERVOUS MATTER, ITS
   CHEMICAL AND ANATOMICAL ANALYSIS.--THE FIBROUS AND VHSICULAR
   NERVOUS MATTER.--THE NERVOUS SYSTEM.--THE NERVES, CEREBRO-
   SPINAL AND  SYMPATHETIC.--THE NERVOUS CENTRES.--NERVES AND
   NERVOUS CENTRES  IN INVERTEBRATA.—DEVELOPMENT AND  REPRO-
   DUCTION OF NERVES.

   The function of innervation is effected through the medium of the
nervous system, which, ramified throughout the  body, and connected
with and passing between its various organs, serves them as a  bond
of union  with each other, as well as with the sentient principle of the 
188
INNERVATION.
animal.  The mind of man  influences his  corporeal organs through
the instrumentality of this system, as when volition or emotion excites
them to action; and, on the other hand, certain changes in the organs
or textures of the body may affect the mind through the same channel,
as when impressions made upon them excite mental perceptions.  In
this way the nervous system becomes the main agent of what has been
called the life of relation;  for without some channel for the  trans-
mission of the mandates  of the will to the organs of motion, or some
provision  for the reception of those impressions  which external ob-
jects are capable of exciting, the mind, thus completely isolated, could
hold no communion with the external world.
   The  nervous  system,  however, can  act  independently of mental
influence.  A material or physical change in the  nervous substance,
unconnected  with any affection of the mind, is capable of exciting the
action  of  nerves, and  consequently of those organs which are sub-
ject to their influence.   Some kind of molecular change  in the nerv-
ous  matter is all that is  at any time required for the development of
its peculiar power;  and it is  as easy to  conceive that this alteration
may result from some organic cause, as from mental influence.  Of
this  kind, no doubt,  are all those  nervous actions with which are
associated the functions of the life of the individuals, or, in the lan-
guage  of  Bichat, of organic life ; an essential character of which is,
that they are completely  removed from the influence of the will.
   In every ordinary voluntary action, the first step is a mental change,
in which consists the  act of volition.  The mind is perfectly able to
induce this change in itself,  without any reference  to the body: but
if it direct its influence upon certain muscles, the contraction of those
muscles immediately ensues, in  a  combined and regular manner, so
as to produce the predetermined voluntary action.  But the influence
of the mind cannot be brought to bear upon the muscles, save through
the intervention of the nerves, as is amply proved by the destruction
of certain  voluntary movements, which  is consequent  upon the de-
struction of certain nerves.
   Again,  in  all cases of common or of special sensation, that state
of the mind,  in which the sensation consists, is induced by an impres-
sion made upon certain bodily organs, and conveyed to the  mind
through the  instrumentality of the nerves.   For there  is abundant
evidence  to prove, that, while the  mind is of itself capable of enter-
ing that state, it cannot do so in obedience  to bodily change, if cer-
tain nerves be destroyed or impaired ;  that, in short, the nerves are
the only corporeal channel through which sensations can be excited.
If the skin be forcibly irritated or compressed, instantly pain is felt;
but, were the nerves of the skin destroyed,  no degree of irritation or
pressure would  make the  mind  cognizant  of  the  injury.  Light  is
admitted to the  eye, and forthwith a corresponding affection of the
mind ensues; but, for the production of this, the integrity of the optic
nerve is a necessary condition.
   In these examples of nervous action, it will be observed that,  in
the former instance, mental  change produces bodily action ; and,  in
the latter, an impression upon some  part of the body precedes and 
        CONNECTION OF NERVOUS ACTIONS WITH THE MIND.   189

gives rise to an affection of the mind.   In both cases nervous power
is called forth: in the one,  it acts in the direction from mind to body;
in the other, from body to  mind.  In  both  cases, destruction of the
nervous  matter wrould prevent the development of the force.   The
muscles may be sound, and the will  may be vigorous; but  without
perfect nerves the latter cannot impart its mandates to the former. Or
the eye may be perfect in  all its optical adjustments, and the  mental
sensibilities keen and quick ; and yet, if the  optic nerve be diseased,
the light which falls upon the retina produces no impression upon the
mind.
   " Of the nature of the connection of this  great sensorial  organ,"
(the nervous system,) says  Dr. Brown, " with the sentient mind, we
never shall be able to  understand more than is involved in the  sim-
ple fact, that a certain affection of the nervous  system precedes im-
mediately a certain affection of the mind.  But though we  are ac-
customed to regard this species of succession of bodily and mental
changes as peculiarly inexplicable, from the very different nature of
the  substances which  are  reciprocally affected, it is truly not  more
so than any other case of succession of events, where the phenomena
occur in substances that are not different in their properties, but ana-
logous, or even absolutely  similar; since, in no one instance of this
kind, can we perceive more than the uniform order  of the  succession
itself; and of changes, the successions of which  are  all  absolutely
inexplicable, none can be said to be more or  less  so  than another.
That a peculiar state of the mere  particles of the brain should be fol-
lowed by a change of state of the sentient mind, is  truly wonderful;
but, if  we consider it  strictly, we shall  find it to  be by no means
more wonderful than that the arrival of the moon at  a certain point of
the heavens should render the state of a  body on the surface of our
earth different from what it otherwise would  naturally be ; or that the
 state of every particle of our globe, in its relative tendencies of gra-
 vitation, should be instantly changed, as it unquestionably would be,
 by the destruction of the  most distant  satellite of  the  most distant
 planet  of our system, or, probably too, by the destruction even of one
 of those remotest of stars which are illuminating their own systems of
 planets,  so far in the depth of infinity that their light—to borrow a
 well-known illustration of sidereal  distance—may never yet  have
 reached our earth since the moment at which they darted  forth  their
 first  beams on the  creation  of the universe.   We  believe,  indeed,
 with as much confidence,  that one event will  uniformly have for its
 consequent  another event, which we  have  observed to follow  it, as
 we  believe the  simple fact, that  it has  preceded it in the particular
 case observed.   But  the  knowledge of the present  sequence, as a
 mere fact to be  remembered, and  the expectation  of future similar
 sequences, as the result of an original law of our belief, are precisely
 of the same kind, whether the sequence of changes  be  in mind  or  in
 matter, singly, or reciprocally in both."  {Philosophy of the  Human
 Mind.   Lect. xix.)
   It is not merely through voluntary effort that the  mind  can excite
 the action of nerves.   The involuntary, and often uncontrollable, in- 
190
INNERVATION.
fluence of emotion is likewise able to give rise to certain movements,
and even to produce certain sensations, through the  nerves.  How
quickly the expression of the countenance changes under the varying
phases of mental emotion ;  and how faithfully does it naturally por-
tray the working of the mind within !  And fear, joy, disgust, horror,
are each accompanied with sensations so peculiar, as to  leave an in-
delible impression on the minds of those who have once experienced
them.
  There are many actions of the livmg frame, however,  in which the
play of the nervous system is unconnected with mental change, which
are therefore wholly physical, in origin, as  well  as in nature.  The
movement of the oesophagus in propelling food onwards to  the sto-
mach  is dependent mainly, if not solely, upon the physical stimulus of
the food acting upon the nerves of the organ, which in  their turn
provoke its muscular fibres to contract.  The slightest touch, even of
a feather,  to the mucous  membrane of the fauces causes the muscles
of deglutition to contract forcibly, as in the  act of swallowing ;  nor
can the will control or  prevent their action.   When the edge of the
eyelid is touched, the orbicular muscle contracts forcibly, and in im-
mediate response to the stimulus  applied.   When light is suddenly
admitted to the eye, the pupil may be observed to contract to a  de-
gree proportionate to the intensity of the stimulus.  Of this action of
the iris the individual is quite unconscious, although  perfectly sensi-
ble of the admission of light to the eye ; nor  can  he, by any direct
influence of volition, modify or oppose it.
  We remark, in reference  to these actions, that the mind  has no
share  in their production.   In some of them, indeed, it  is conscious
of the application  of the  stimulus, as well  as of the  muscular act
which follows.  But no effort of  the will, however great, could in-
terrupt the uniform and natural sequence of the phenomena.  And it
is well known to  medical men that actions of this kind  may take
place  in coma, when all mental manifestations are completely in abey-
ance.
  These facts afford abundant evidence of a class of nervous actions,
which, in  respect of their exciting  cause, as well as in their intrinsic
nature, are independent of mental influence, and which  ought on this
account to be distinguished from those of volition, sensation and
emotion.  Their mechanism is more complex than that of the mental
nervous actions; for, while in the latter the change in the nerves is
propagated in only one direction, in the former it passes first to some
central part of the nervous system, and thence it travels in  an oppo-
site course to the motor organs.  Hence two nerves are  necessary for
such actions; the one as an excitor, the other as a motor nerve; and,
on this account, Dr. Marshall Hall has distinguished these actions by
the name of excito-motory.
  That a physical change may excite nervous action quite independ-
ently  of mental influence, is further proved  by instances of convuls-
ive movements, more or less violent, which are produced by a morbid
irritation of the brain or spinal cord.
  The peculiar animal matter, through the agency of which all these 
NERVOUS MATTER.
191
phenomena take place, the nervous matter, is found in two forms, the
vesicular and the fibrous.   The vesicular nervous matter is gray orcine-
ritious in colour, and granular in texture ; it contains nucleated nerve-
vesicles, and is largely supplied with blood ; it is  more immediately
associated with the mind, and is the seat in which originates the force
manifested in nervous actions.  The fibrous nervous matter, on the
other hand, is in most situations white, and composed of tubular fibres,
though in some parts it is gray, and consists of solid  fibres:  it is less
vascular than the  other, and is simply the propagator of impressions
made upon it.
   When these two  kinds of nervous matter are united together in a
mass of variable shape or  size, the body so formed is called a nervous
centre, and the threads of fibrous matter which pass to or from  it are
called nerves.  The latter are internuncial in their office ; they estab-
lish a communication between the nervous  centres and the  various
parts of the body, and vice versa ; they conduct the impulses of the
centres to the periphery, and communicate the impressions made upon
the peripheral nervous ramifications to the centres.  The centres are the
great sources of nervous power, the laboratories in which the nervous
force is generated: the mind is more immediately connected with one
of them, the  brain, which, on that account, possesses greater physical
development  and acquires pre-eminence over the others.  The smaller
nervous centres are called ganglions ; the larger ones are  the  brain
and spinal cord.    All of these are found in the human  subject, and in
the vertebrate animals.   In the invertebrate classes, the centres are
ganglia variously disposed, according to the shape and actions of the
animals.
   The brain and spinal cord, and the system  of nerves connected with
them, constitute  the cerebro-spinal  portion  of the  nervous system,
which Bichat distinguished as the  nervous  system of animal life.
The nerves of the senses, and those of volition and common sensation,
are connected with it, as well as those which are concerned in  many
of those purely physical nervous actions with which  the mind has no
connection.   There are very numerous ganglions connected with this
system which are  conveniently comprehended under the same title.
These are, the ganglions on the posterior roots of  the  spinal nerves,
the ganglion of the fifth pair, those of the glosso-pharyngeal and  of the
vagus.
   The remainder of the nervous system is made  up  entirely of gan-
glions, with  their  connecting cords  and  nerves, which ramify in a
plexiform manner among various internal viscera, and  upon the coats
of blood-vessels.   In the  higher vertebrate animals,  it is disposed as
a chain of ganglia on each side of the vertebral column, and  at the
base of the skull near the foramina through which the  spinal and en-
cephalic nerves pass out;  and at all these situations it forms a very
intimate connection  with the brain and spinal cord.  This portion of
the nervous  system  possesses many peculiarities,  both in its compo-
sition, in its arrangement, and in its connection with the organs among
which its nerves  ramify, which, at  least, entitle it to  be considered
apart from  the cerebro-spinal system.  How far it can be regarded 
192
INNERVATION.
as independent of that system, is  a question which must be reserved
for future examination.   This is the sympathetic or ganglionic system,
formerly known and described as the great intercostal nerve, and  by
Bichat as the nervous system of organic life: it has also been called
the visceral nerve.   All these titles  are liable to  objection, inasmuch
as each involves to a greater or  less extent some theory of the  uses
or actions of these nerves ; but the two first-mentioned are preferable,
as those which are best known, and most confirmed  by use.
   The nervous system, then, in man and the vertebrate series,  con-
sists of the  brain, spinal cord, and the nerves associated  therewith,
the cerebro-spinal system; and that double chain of ganglia, with  their
nerves, situate along the  spinal column, the sympathetic or ganglionic
system.  Among  the invertebrata,  although  the arrangement of the
nervous system differs very materially from that in the vertebrata, an
analogous subdivision of it may be made in a  large proportion of those
classes, the  anatomy of which has been satisfactorily made  out.
   Physical and Chemical properties of the Nervous Matter.—The nerv-
ous  matter  of both kinds is a soft, unctuous substance,  easily dis-
turbed by slight mechanical force.  Were it not  associated  with other
tissues, and supported,  to a certain  extent,  by the  blood-vessels
which ramify among its elements, its physical tenacity would be  very
feeble.
   Its great softness is due, in part, to the admixture of a large quan-
tity of water with it, which constitutes three-fourths, or  four-fifths,
and, in many instances, seven-eighths, of its weight.   According to
Vauquelin, whose analysis was made in 1812, the brain is an emul-
sive mixture of albumen, fatty matter,  and water ; the last  holding in
solution certain  saline and other  ingredients common to  the brain
with other parts of the body.  By solution in boiling  alcohol, Vau-
quelin was enabled to resolve the fatty matter into elaine  and stear-
ine (margarine ?) The following table gives the result of his analysis:
               Albumen.....7-00
               Cerebral fa<  .  \ f™  J» j    5.23
               Phosphorus.....1-50
               Osmazome   .   ' .    .    .    .   1-12
               Acids, Salts, Sulphur   .    .    .   5-15
               Water......80-00
                                             100-00
Vauquelin remarked that the medulla oblongata, and medulla spinalis,
have the same  composition  as the brain, but  contain  a  much larger
proportion of cerebral fat, with less albumen, osmazome, and  water.
  These results are confirmed, in the main, by the analysis of Fremy,
which was published in the Annates de Chimie for 1841.  M. Fremy
states, that the three  principal constituents previously detected  by
Vauquelin, exist in the following proportions  in  one hundred parts:
seven parts of albumen, five parts of fatty matter, and eight parts of
water.
  From  the  fatty matter of  the brain  M. Fremy extracts various
secondary organic compounds; namely, 1. Cerebric  acid; a white 
NERVOUS MATTER.
193
substance in the form of crystaline grains, abounding in carbon, and
containing a minute proportion of phosphorus.   2.  Cholesterine, the
same as that which is  obtained from  bile.   In preparations  of the
brain preserved in spirits, a substance of  crystaline character  resem-
bling cholesterine is apt to form round the piece. 3. Oleophosphoric
acid ; a peculiar fatty acid, containing from 1-9 to 2 per cent, of phos-
phorus in  the  condition of phosphoric acid.  Fremy regards it  as
analogous to the compound  of sulphuric acid  and  elaine, or  sulph-
oleic acid.  4.  Traces of elaine, margarine, and fatty acids.   These
principles do not always exist in an  isolated state ; for the cerebric
acid is often combined with soda, or phosphate of lime, and the oleo-
phosphoric acid is commonly found in union with soda.
   The  quantity of  phosphorus which may be  found in  the nervous
matter varies  considerably at different periods of life, and   is  very
small in  idiotcy.  According to L'Heritie's analyses,  the minimum
of this element is found in infancy, in old age, and  in  idiotcy ; and
the maximum of water exists in the infant.  The following is  a table
of his comparative analyses:
	Infants.	Youth.	Adults.	Old Men.	Idiots.
Albumen	7-00	. 10-20	9-40	8.65	8-40
Cerebral fat	3-45	. 5-30	6-10	4-32	500
Phosphorus	0-80	. 1-65	1-80	100	0-85
Osmazome and Salts	5-96	. 8-59	. 10-19	12-18	14-82
Water .	82-79	. 74-26	. 72-51 100-00	73-85	70-93
	100-00	10000		100-00	100-00
  A careful comparative analysis of the vesicular and fibrous matter
is as yet a desideratum.  We are ignorant of the nature of the color-
ing material of the former.  John  states that the vesicular substance
is deficient in  white fatty matter, and that  its albumen is less tena-
cious than that of the fibrous substance.
   Of the fibrous nervous matter.—Of the two kinds of nervous mat-
ter, the fibrous is that which is most extensively diffused throughout
the body.  It  not only forms a large portion of the  nervous centres,
either alone or mixed  with vesicular matter, but it is the principal
constituent of the  infinite multitude of nerves which  connect  them
with the  various tissues and organs.
   The structure of  the fibrous matter should be examined in a piece
of nerve, and  in a  thin section from  the  white part of a nervous
centre, as the brain or spinal cord.   These  should be  torn with nee-
dles, so as to separate and isolate as much as possible the elementary
parts, and to remove, as far as may be practicable, extraneous tissues.
   The fibrous nervous  matter, wherever it is found, consists of fibres
which have a  definite  arrangement.  Two kinds of primitive fibre
are present in the nervous system, and these we  shall  distinguish
as the tubular fibre, or the nerve-tube, and the gelatinous fibre.   The
former are  infinitely the more  numerous; the  latter  being found
chiefly in the sympathetic system.
   1.  Of the tubular fibre.—When  a nerve-tube  is perfectly recent,
and unaffected  by reagents,  it  presents, if viewed by  reflected light,
a beautiful  pearly lustre,  and appears to be quite homogeneous.   But 
194
INNERVATION.
if viewed  by transmitted  light,  and  with a  sufficient magnifying
power, a more complicated structure becomes visible in all the largest
and  best marked specimens (fig 52, a, b, and fig.  53,  a).   Most  ex-
ternally  is the tubular membrane (a, d d), an homogeneous and proba-
bly elastic tissue of extreme  delicacy, analogous to the sarcolemma
of striped  muscle  (p.  150),  and  according to  our observation, not
presenting any such distinct, longitudinal, or oblique fibres in its com-
position as have been described by some writers.   WTithin  the edge
                                     of  the tubular  membrane,  on
                                     each side, are seen two thicker
                                     and darker lines (a,  c, c,  b),
                                     which appear to mark the outer
                                     and inner  limits  of  an  inner
                                     layer  of different composition
                                     and refracting power, and which
                                     is  generally known as  the white
                                     substance  of Schwann.   This
                                     forms  a tube within the tubular
                                     membrane.   Within  the white
                                     substance of Schwann is a trans-
                                     parent material,  occupying  the
                                     axis of  the nerve-tube  (a,  a).
                                     This has been called by Remak
                                     the flattened  band; but  a better
                                     name for it is that of axis cylin-
                                     der, employed by Rosenthal and
                                     Purkinje.
                                        It is evident,  that the whole
                                     of the matter contained  in  the
                                     tubular membrane  is extremely
                                     soft, for it is found to yield un-
                                     der very slight pressure, and may
                                     be  readily made  to  pass from
                                     one part of the tube to another.
                                     When pressed out (b.  h  to I), it
                                     is  apt to assume more or less the
                                     appearance and form of globules,
                                     which retain the same characters
                                     of outline which  they possessed
                                     in  the  nerve-tube;  that  is, they
                                     have   a   transparent   interior,
                                     bounded by a layer of the white
                                     substance  of Schwann,  marked
                                     by its double  contour.  It would
                                     appear that the  latter structure
is particularly apt to form a coating or film over  the central material,
and  thus to isolate  it from surrounding tissues.  This tendency may
be understood by a reference to  fig. 52, h to I.
  When the nerve-tube is placed in ether, the white substance is in
part  immediately dissolved, and  a  number of oil-like globules appear
 a. Diagram of tubular fibre  of  a spinal
nerve :—a.  Axis cylinder,  b. Inner  border of
white substance,  c c. Outer border of white sub-
stance,   d, d. Tubular membrane, b. Tubular
fibres : e. in a natural state, showing the parts as
in a. /. The white substance and axis cylinder
interrupted by pressure, while the tubular mem-
brane remains, g. The same, with varicosities.
h. Various  appearances  of the white  substance
and axis cylinder forced  out of the tubular mem-
brane by pressure, i. Broken end of a tubular
fibre, with the white substance closed over it.  k.
Lateral bulging of white substance and axis cy-
linder from pressure. 1. The same more complete.
g1.  Varicose fibres of various sizes, from the cere-
bellum,  c. Gelatinous fibres from the solar plex-
us, treated with acetic acid to exhibit their cell-
nuclei,  b and c magnified 320 diameters. 
TUBULAR FIBRE.
195
both within and without  the  tubular membrane (fig. 53, b).   Proba-
bly its margarine is dissolved, and the  elaine set free in the form  of
oil-globules.   The interior  of  the  tube is
also rendered decidedly granular.  In water
the white substance  of  Schwann  remains
undissolved, while  the interior  of the fibre
is frequently, though  not always, rendered
granular.
   The tubular membrane presents the  same
general characters wherever  it is met with.
But the white substance of Schwann exhibits
much variety as regards its thickness in dif-
ferent parts  of the  nervous system.   In the
nerves it is more developed than in the cen-
tres ; but even in  the former it differs a good
deal as to thickness.  We  find  it most  de-
veloped in  the ordinary spinal nerves ; in
those of pure sense it exists  in small quan-
tity.  Both  these elements  of  the  tubular
fibre  evidently afford  mechanical protection
to the substance which forms its axis;  but
doubtless one or both of them  may have  a
further physiological  office,  insulating  the
axis, and keeping  it  distinct from  any in-
terference with constituents  of  neighboring
fibres.    The chemical  composition  of the
white substance,  being  obviously  different
from  that of the  axis, sufficiently denotes  a
difference of function in  these two  portions of the nerve-tube.  The
axis cylinder of the nerve-tube,  though in general soft and pulpy, is
in some instances of firm texture, and when broken projects  beyond
the white substance (fig.  56, c).  It then occasionally exhibits a well-
marked fibrous character, and may even split into filaments.
   When the tubes are quite fresh, and have been but little disturbed
by manipulation, their form is that of a perfect cylinder.  Pressure,
or  separation, is apt to alter their shape by disturbing the position  of
the contained pulp, pushing more than is natural into some  parts  of
the tube, and consequently diminishing the bulk of the contents in the
adjacent parts; so that the latter collapse,  whilst the former become
distended, enlarged, and even varicose (fig. 52, b).   Nerve-tubes,
that have been thus affected,  sometimes present merely a slight wavi-
ness of one or both margins, but more frequently a series  of  distinct
swellings or varicosities separated  by constricted  portions.   These
swellings are found at very irregular  distances from each  other, and
vary  extremely in shape and  size.   They are much more apt  to form
upon some  nerve-tubes  than upon others  ; and  this is  apparently
owing to a feebleness of the tubular membrane, and perhaps,  also,  to
a less degree of consistence of the  contained nervous pulp.   In the
nerves of special  sensation the tubes are very delicate in structure,
and very apt to exhibit this  change; and in the fibres of the  brain
Tig. 53.
 Nerve-tubes  of the common
eel:—a. In water.  The delicate
line on its ex'er'or indicates the
tubular membrane.  The dark,
double-edged inner one is the
white substance of Schwann,
slightly wrinkled,  b. The same
in ether.  Several oil-globules
have coalesced in the interior,
and  others have accumulated
around the exterior of the tube.
The white substance has in part
disappeared.—Magnified 300 di-
ameters. 
196
INNERVATION.
and spinal cord  the same tendency is  observable.  It was formerly
supposed  by Ehrenberg, that these  varicosities  were natural,  and
existed during life ; and that they afforded a valuable morphological
character of the nerves of pure sense, and of the  cerebro-spinal cen-
tre. Many circumstances, however, oppose this view: thus, the irre-
gularities in the shape, size, and  number of the  varicosities appear
very unlike a natural  disposition:  in a piece of the brain  or spinal
cord which has not been much pressed or torn, the nerve-tubes often
exhibit a cylindrical  figure, and even in the manipulated  specimen
the varicose  tubes form  only a  portion.   In some nerves, such as
those  of muscles, the tubes, although not prone to become  varicose,
may be made so by firm pressure  and violence in manipulation ;  and
in the nerve-tubes of young animals, the tissues  of which  are more
tender, and contain more abundant water, this change is  particularly
apt to take place.
   The nerve-tubes, for the most  part,  lie parallel to each other,  al-
ways  without branching, and if we except their terminal looping in
other textures, without any inosculation.  This very interesting and im-
portant feature in the anatomy of the nerve-tubes was recognized long
ago by Fontana, and has been  confirmed by nearly every subsequent
observer.   It may be seen in the  nervous centres,  as well  as in the
nerves themselves.  In the  latter it may be  well  demonstrated by
examining a piece of nerve on a dark  ground as an opaque object.
The primitive fibres, viewed in this way, appear as so many trans-
parent tubes,  containing  an  exquisitely delicate, soft, pearly-white
material.   The tubular fibres vary in  diameter, from T/oo  to even
Toiotf of an inch ; but their  average width is from 20V0 t0 tdVo of
an inch.
   2.  Of the gelatinous nerve-fibre.—This  term is applied  by Henle
to certain fibres found principally in the  sympathetic  nerve. They
are flattened, soft, and homogeneous in appearance ;  containing nu-
merous cell-nuclei,  some of  which are round,  others oval; some
situated in the  centre of the fibre, others  adhering to either edge;
their  longest diameter being generally parallel to the longitudinal axis
of the nerve.   These nuclei are  arranged  at nearly equal  distances,
and frequently exhibit distinct nucleoli (fig. 52, c). Sometimes these
fibres show a disposition to split  into very  delicate fibrilla?.   Acetic
acid dissolves the fibre, leaving the nuclei unchanged. These fibres,
containing nothing analogous to the white substance of Schwann, are
devoid of that whiteness which characterizes the  tubular fibre; and it
would seem that the gray color of certain nerves depends chiefly upon
the presence of a large proportion of the  gelatinous  fibres.   Hence
they  are sometimes called gray fibres.
   The mode or connection of the gelatinous fibres with the elements
of the nervous centres,  is, as yet, quite unknown.  They are found,
in considerable  numbers, in what are  called the  roots of the sympa-
thetic, or the communications of that nerve with the spinal  nerves:
it has been supposed by Valentin that they are continuous with cer-
tain elements of the vesicular nervous matter.
   These fibres are smaller, in general, than the  tubular fibres ;  their 
GELATINOUS FIBRE.
197
diameter ranges between the  FrVo  and the ToVo  of an inch.   They
resemble very much the fibres of unstriped muscle.
   Of Die vesicular nervous matter.—This is distinguished by its dark
reddish gray color, and soft consistence :  it is found  in the nervous
centres, but never in  nerves, probably so  called, and it is always
supplied by a considerable plexus of blood-vessels.
   The essential  elements of  the
gray nervous matter are vesicles
or  cells,  containing  nuclei and
nucleoli.   They have  been also
called nerve or ganglion globules.
The wall of each vesicle consists
of an exceedingly  delicate mem-
brane,  containing  a soft but te-
nacious  finely  granular  mass.
The nucleus of the cell is gene-
rally eccentric, much smaller than
the  containing vesicle, and adhe-
rent to some part of its interior.
Its  structure   is  apparently  the
same as that of the outer vesicle.
The nucleolus is  a minute,  re-
markably  clear    and  brilliant
body,  also  vesicular,  inclosed
within  the  nucleus.   It forms  a
most  characteristic  and
often conspicuous part of
the  nerve-vesicle.
   The ordinary  or  pre-
vailing form of these ele-
ments is that of a  globu-
lar vesicle.  So  soft and
compressible   are   they,
however,  that  a  good
deal of diversity of shape
is  manifest in  them,  by
reason of  the compres-
sion they  suffer  as  they
lie   packed  together  in
situ.   Hence  some  are
spherical, others ovoidal,
or ellipsoidal.   In some
vesicles we find, external
to  the nucleus,  particles
of a coarser kind, which
are   accumulated   in  a
mass,  frequently   Of  a   Ganglion globules, with their processes, nuclei, and nucle-
Semilunar  form.   These  "L1,;""-"• ^om the/le,ePer P"t of the gray matter of the con-
                            volutions ol the cerebellum. The larger processes are directed
are   pigment  granules ;  towards the surface of the organ,  b. Another from the cerebel-
., •            °  •        lum. c.d Others from the post, horn of gray matter of the dor-
tlieir  presence  gives  a  sal region of the cord  Tii-s.- contain pigment, which sur-
flarlr rnlnr tn  a  nortinn  roullds the nucleus in c. In ;i!l tl„se specimensthe procures
UdrK COiOr to  d  poiuuil  are more or led* broken—Magmacd 200 diajnetera.
  Nerve-vesicles from the Gasserian ganglion of
the human subject:—a A globular one with de-
fined border j 6. its nucleus ; c. its nucleolus,  d.
Caudate vesicle, e. Elongated vesicle, with two
groups of pigment particles, f. Vesicle surround-
ed by its sheath, or capsule, of nucleated parti-
cles,  g. The same, the sheath only being in fo-
cus.—Magnified 300 diameters.
Fig. 55.
 
198
INNERVATION.
 of the vesicle.   Sometimes we find two groups of pigment  granules
 in one vesicle.  They are usually of a reddish, or yellowish-brown
 color.
   Another form of nerve-vesicle is characterized by one or more tail-
 like processes extended from it, and to such  nerve-vesicles  we  may
 apply the term caudate.   They possess  the nucleus and nucleolus, as
 in the more simple form ; and contain one or more masses of pigment,
 which are  often of  very considerable  size.   Both the vesicles and
 their caudate processes  vary greatly  in  size and shape.  The largest
 nerve-vesicles  are found among those of this kind.  Sometimes there
 is but a single  process from this vesicle ; or  there may be two, pro-
 ceeding from opposite sides ; or there may be several, extending  in
 various directions.   There is great  difference in  the  shape  of these
 caudate  vesicles,  as may  be  observed in figs.  55 and 56,  where
 different  varieties of them  are  represented.   In  point of structure,
 the  caudate processes are exceedingly  delicate, and finely granular,
 like the interior of the vesicle,  with which they distinctly seem to be
 continuous. Such is the delicacy of these processes, that they readily
 break off;  in general, very close  to  the vesicle.   Sometimes, how-
 ever, one or more of them may be traced to a considerable distance,
 and  will be found to divide into  two  or into three branches,  which
 undergo a further subdivision, and give off some extremely fine trans-
 parent fibres (fig. 56, 6), the connection of which with the other ele-
 ments of the nervous tissue has yet  to  be ascertained.   It is most
probable, however, that they either serve to connect distant vesicles,
or else that they become continuous with  the axis cylinders of the
tubular fibres.  In the cerebro-spinal centre,  we have found the tis-
sue in the vicinity of the caudate vesicles freely traversed in all direc-

                                Fig. 56.
 a. A large caudate nerve-vesicle, with diverging and branching processes, some of which, b, are
seen to pass off into extremely minute filaments.  These seem to bear a very close resemblance to
the central part of a tubular fibre, c, which is prolonged some way bevond the broken ed<^e of its
tubular membrane and white substance, d.  At e, are some small nerve-vesicles, stellate in form,
doubtless from numerous processes given off from them : /, several extremely small nerve-tubes,
some of which are varicose. This figure exhibits the great variety of size of the vesicles and tubes.
a. is from the posterior horn of the gray matter of the spinal marrow, and is magnified only 120 diame-
ters, while the vesicles and tubes at e, from the gray matter of the lower end of the cord are mag-
nified 300 diameters,  d. is also from the spinal marrow, and is magnified 200 diameters.  ' 
NERVES.
199
tions by numerous very delicate filaments, which seem to be the rami-
fications of the caudate processes.   These often exhibit considerable
tenacity and elasticity.   The situations from which we  may obtain
such caudate vesicles as  are best suited for examination are the locus
niger in the crus cerebri, and  the gray matter of the cerebellum  and
spinal cord.
   The nerve-vesicles do not lie in immediate contact with  each other.
They are either imbedded in a soft, granular matrix, as in the  brain,
or  enveloped  in  a  capsule  of
nucleated cells, as  in the gan-
glia (fig. 54,/, g).  The inti-
mate connection of this granular
sheath to the vesicle, and to its
processes when they exist, in-
creases greatly the difficulty of
examining them. It is not easy
to detach them from this invest-
ment. This is generally effected
by accident more  than  by skill
in manipulation, and it is along
the broken margin of the piece
under examination that we shall
succeed  in  detecting the most
perfect vesicles.
   In  most  situations   where
vesicular matter is found in the
nervous  centres, tubular fibres
of  small though  variable  size
mingle  with   its elements   in
greater or less number, and  in
some places both  varieties  of
fibre are found (figs. 57 & 58).
To determine the precise con-
nection which  these  respective
elementary parts form with each
other is a problem of the deep-
est  interest.    No  more,  how-
ever, can be said respecting it
at present, than that the relation
of nerve-fibres to nerve-vesicles
in the centres is most  intimate,
and  that the  latter  are  rarely
met with without one or more of
the former in immediate connec-
tion with them.
   Having premised this general
account of the anatomical ele-
ments of the two kinds of nerv-
ous matter, w7e may now con-
sider separately the two leading
Fig. 57.
  A. Blending of the vesicular and fibrous nervous
matter in the dentate body of the cerebellum :—o.
Ganglion globule, with its nucleus and nucleolus.
6. Nerve-tube, slightly varicose, in close contact
with the ganglion globule, b'. Smaller nerve-tubes.
These parts all lie in a finely granular matrix in
terspersed with nuclei, c.  b. Vesicular and fibrous
matter of the laminae, of the cerebellum,  a. Gan-
glion  globule.  6. Very minute nerve-tubes tra-
versing a finely granular matrix, in which are nu-
merous rounded nuclei, c.
 From the Gasserian ganglion of an adult:—a. a.
Ganglion globules with their nucleus, nucleated
capsule, and pigment, t. Tubular fibres, running
among the globules in contact with  their capsule.
g. Gelatinous fibres  also in contact with the gan-
glion globules.—Magnified 320 diameters. 
200
INNERVATION.
 subdivisions of the nervous system; namely, the nerves and the cen-
 tres.
   Of nerves.—A bundle of nerve-fibres, surrounded and  connected
 by areolar tissue, constitutes a nerve.
   The nerves of the cerebro-spinal system differ in several  important
 particulars from those of the sympathetic, and they should,  therefore,
 be examined separately.
   Of the  cerebro-spinal nerves.—The  areolar  tissue which  invests
 the nerve-fibres  is  called the neurilemma.  It is analogous to the
 sheath of the same  membrane which surrounds the elementary fibre
 of striped muscle.   From its deep surface the layers of areolar tissue
 pass, forming so many partitions between the smaller bundles, or the
 individual fibres, of which the nervous trunk is composed.  The office
 of this structure is evidently to give protection to the delicate nerve-
 tubes, and to  support  the  plexus of minute capillary  vessels from
 which they derive their nutriment.
   The neurilemma is composed of fibres of white fibrous tissue, and
 presents to the naked eye the silvery aspect of that texture.  Some
 persistent cell-nuclei are scattered throughout it.  That portion of it
 which forms the partition between the fibres contains a  little yellow
 fibrous tissue of the  finest description.
   The blood-vessels are distributed upon the external investing sheath,
 and upon the septa.  They are disposed  similarly to  those of mus-
 cles,  and run parallel to the fibres of the nerve.  The  capillaries are
 among the smallest in the body : they form oblong meshes  of consi-
 derable  length, completed at long intervals by vessels which cross the
 fibres of the nerve more or less transversely.   These blood-vessels
 are generally derived from neighboring arterial  branches;  sometimes
 a  special vessel accompanies a nervous trunk,  and even  perforates
 it, passing along its  axis,  as in the great sciatic  and the optic nerves.
   The composition  of  a cerebro-spinal  nerve  may be shown by re-
 moving the neurilemma, and separating the fibres by needles.  These
 fibres are  chiefly of the tubular  kind.   In diameter they vary con-
 siderably, but do not exceed  the  TTV?  of an  inch in man  and  the
 mammalia.   They lie within the sheath in simple juxtaposition, and
 parallel to each other ; excepting where a branch is about to separate,
 when a bundle of nerve-tubes gradually deviates from  its previous
 course,  and forms a  very acute angle with the  trunk, still,  however,
 preserving the  parallelism of its constituent fibres.
   Nerves are said to arise or have their origin  in the nervous centre
 to which they are on the  one hand attached, and to terminate or be,
 distributed among the elements of  the various textures on  the other
 hand.  It is best to continue the use of so definite and simple a mean-
 ing to these terms.  Attempts to alter their signification in accordance
 with opinions of the functions of the constituent fibres  can at present
 do little but confuse descriptions.   We call a nerve cerebral or ence-
phalic, if it be connected at its origin with some part  of the nervous
 mass  within the cranium ;  and spinal, if its apparent origin be from
 the spinal cord.
   Origin.—The fibres of nerves may be traced  into the nervous cen- 
ORIGIN OF NERVES.
201
tres, the white or fibrous part of which they contribute to form.   As
they enter the centre, the fibres diverge slightly either  singly or  in
separate bundles, and pass on to  form a connection with vesicular
matter, in the immediate vicinity of the point of immergence or at a
more remote situation.  How the fibres comport themselves with re-
spect to the elements of the vesicular matter is not exactly known.  It
is certain,  however, that nerve-tubes frequently adhere to the sheaths
of nerve-vesicles, and that many of them pass between the nerve-
vesicles, probably to form a connection with more distant ones.  This
may be well seen in the vesicular  matter  of any of the  centres.   It
is very distinct in the ganglions, and also sufficiently manifest in the
spinal cord or  brain.  In the last-named  centres  some of the tubes
which are found in the vesicular  matter are reduced to an extremely
minute  size (figs. 56,/; 57, A, b' and B, b), and  exhibit small vari-
cosities, sometimes at very regular distances from  each other.
   Valentin describes a looped and plexiform arrangement of the fibres
in the vesicular matter of the centres.  Hitherto, such  an arrange-
ment has  eluded our observation so  completely, that,  but for the
high  authority on which  this  statement rests, we should not have
deemed it  necessary to  allude  to it.   The only confirmation of this
view with which we have met is derived from an highly interesting
dissection, by Mr. Lonsdale of  Edinburgh, of a monstrosity, in which
the spinal cord, medulla oblongata, and cerebellum were absent, but
the hemispheres of the brain were present.  Several of the encepha-
lic and spinal nerves hung " as loose  threads" in the cavity of the
cranium or  spine.   On examining the  free or  central extremities  of
these nerves, their constituent fibres were found to form distinct loops,
convex towards the  cranial or spinal cavity.  These loops were im-
bedded in granular  matter, supposed  to  be vesicular matter in  an
early stage of formation.  Similar loops were observed by the same
anatomist in the cranial  nerves  of an anencephalous foetus wrhich had
been preserved in spirits.*
   Branching.—As a nerve passes from centre to periphery, it breaks
up into a number  of small  bundles, which  form so  many branches
destined for the organs or  tissues among  which they are placed.
These branches generally separate from the  parent trunk  at  an acute
angle, and soon plunge into the muscles or other parts to which they
tend, dividing  and  subdividing among them.   Some exceptions  to
this  rule, however, are  occasionally met with, in which  the branch
forms a right or an obtuse angle with the trunk.
   Before a branch separates, the parent nerve  seems wider for some
distance above the point of visible  separation.  This is owing to  a
divergence of the fibres within the trunk before they actually  leave it,
and not to any increase in the number  of the nervous elements.    A
good  example may be seen in the  auricular  nerve of  the neck, as it
winds upwards over the sterno-mastoid muscle.
   Anastomosis.—In their branchings nerves subdivide,  not only to
pass immediately to their distribution in muscles or other parts, but

   * Dr. Lonsdale's case of Monstrosity. Ed.  Med. and Surg. Journ., No. 157.
     14 
202
INNERVATION.
Fig. 59.
also  to form  a connection,  by some of their  filaments, with  other
nerves and to follow the course of the latter, whether to the periphery,
or back again to the centre,  instead of passing  to  the destination  of
the primary  trunk.  By these means nervous filaments connected
with very different parts of  the brain and spinal cord become bound
together in the same neurilemma, and a nerve is formed compound-
ed of nerve-tubes possessing different functions.   The anastomosis
of nerves thus formed differs from the more correctly named anasto-
mosis of blood-vessels; for in the latter case the canals of the anasto-
mosing vessels communicate, and their contents are mingled; but  in
the former the nerve-tubes  simply lie  in  juxtaposition, without any
coalescence of their walls, or any admixture of the  material contained
within them.                                            .
   The simplest  kind of anastomosis is that which occurs in  almost
every spinal  nerve.  The anterior  and the posterior roots of these
                  nerves, emerging from different parts of the spinal
                  cord,  and possessing, as is now  proved, very dif-
                  ferent endowments, are united after  passing through
                  the dura mater, and are  bound together  as one
                  nerve ; the respective tubules being so completely
                  intermixed that the ramifications, which  pass  off
                  in the subsequent course of the  nerve, for the most
                  part contain tubules from both roots, and therefore
                  possess the functions of both.
                     And even in a nervous trunk, thus formed, there
                  is an  interchange of place between the component
                  filaments, so that those which were at first on  the
                  surface of  the nerve pass into  its centre, and  are
                  replaced by others which had been deep-seated; a
                   decussation of the fibres  occurring as they change
                   places (fig. 59).   Hence it  is often difficult to fol-
                   low a bundle for any distance  in a nervous trunk.
                   According to Kronenberg, this kind of interchange
                   is more  frequent in some  nerves  than in others;
                   and it is stated  by this author  that in the external
                   cutaneous nerve of the arm he found some bundles,
 which passed through a distance  of six  inches without uniting with
 neighbouring ones.
   By another form of anastomosis nervous loops or arches are formed,
 the convexities of which are directed towards the  periphery, and give
 off filaments to  the  neighbouring  parts.   The  well-known anastomo-
 sis between the ninth or hypoglossal nerve,  and the  cervical plexus,
 in front of  the carotid  artery,  may be  quoted as a good example.
 Certain fibres, which come from  the medulla oblongata as part of
 the ninth nerve, leave that  nerve as it crosses  over the  carotid artery,
 pass down in front of the artery, and apply themselves to a descend-
 ing branch of the cervical plexus, forming in front  of the carotid artery
 and jugular vein an arch with the concavity directed upwards, several
 nerves passing  from the convexity to neighbouring  muscles.  Some
 of the filaments which are  given off from this arch, are dprivpd from
 Diagram to show the
decussation of the fibres
within the trunk of a
nerve.—(After Valentin.) 
PLEXUSES OF NERVES.
203
the ninth nerve, and others from the cervical plexus ;  whilst others
seem to form a complete arch, and to be equally connected with both
nerves; and, if we  trace these latter  fibres  from the ninth nerve,
we find them  passing  upwards and backwards into  the  descending
branch of the cervical plexus, and  so  returning to the spinal cord.
The nervous loop, thus formed, must evidently establish a communi-
cation between the cervical region of the spinal cord and that portion
of the medulla oblongata whence the ninth nerve  appears  to derive
its origin.
   Similar nervous loops, leaving the nervous centre as a constituent
of one nerve, and returning to it at some distance in company with
a  different nerve, are found in  various parts of the nervous system.
The commissural fibres of the optic  tracts may be quoted as an ex-
ample.   These fibres leave  the  centre by one tract,  and return to  it
by the other.   It is probably owing  to an  anastomosis of this kind,
between the posterior and anterior roots of the spinal nerves, that the
latter enjoy a slight degree of sensibility. Other instances of a similar
kind have been  described by Volkmann.  In  the calf he found  an
anastomosis between the fourth pair  of nerves and the  first branch of
the  fifth pair, forming an arch,  from  the  convexity of which several
branches passed off  in the peripheral direction.  By far  the greater
part of these, on microscopic examination,  appeared to receive  their
fibres from the fourth;  while those fibres of  the  fifth, which contri-
buted to the formation of the arch, passed  centripetally to the brain,
bound up in the sheath of the fourth nerve.  There is a similar nerv-
ous arch formed between the second or third cervical  nerve and the
accessory nerve.   Certain fibres, when  traced  from  the  former, ap-
pear to pass back to  the centre in the sheath of the latter.  This anas-
tomosis Volkmann found in the human subject, and in several of the
lower animals.*
   According to  Gerber, similar loops are  found in the sheaths of
spinal nerves.  Certain fibres emerge from  and return to the nervous
centre, forming a loop with the convexity directed towards the  peri-
phery, without connecting themselves with any peripheral organ or
texture, or going beyond the nerve-sheath.  To these loops this ana-
tomist has given the fanciful title, nervi nervorum.
   Plexuses.—When  several neighbouring nerves freely interchange
their fires, a complicated form  of anastomosis is produced, which
is  called a plexus.   Four or five nerves, for example, proceed  from
the spinal cord, for  a certain distance without any communication
with each other.   A division of each then takes place, and from the
conjunction of their neighbouring branches  new nerves result, which
again subdivide and  interchange fibres, and by the free communica-
tion which is thus established,  a network is sometimes formed, (as
in  the  cervical plexus,) in  the  meshes  of  which areolar tissue, and
sometimes fat, are deposited.   Finally, certain nerves emerge  from
the plexus thus formed, which are  composed  of fibres derived  from
several of the original trunks.  Examples of this kind of anastomo-
* Miiller's Archiv., 1840. 
204
INNERVATION.
Fig. 60.
 sis are found  in connection with the anterior branches of the spinal
 nerves in the  neck, the axilla, the loins, and the sacral region ;  and
 there are also plexuses formed in  the course  of the fifth  nerve, the
 portio dura of the seventh, the glosso-pharyngeal, and the par vagum.
   The fibres, which pass through a plexus, notwithstanding the ap-
 parent intricacy of their communication, preserve their individuality.
 This may be proved by irritating a single nerve before it has broken
 up in the plexus.  Such irritation will produce  contraction of certain
 muscles  only;  of those, namely, to which the fibres of that nerve are
 distributed.   It is probable that, owing to the frequent change of
 place which the  fibres undergo within  the plexus, they are brought
 into communication with a greater number of muscles than if no such
 subdivision had taken  place.  Kronenberg's experiments showed that
 the irritation of certain nerves of  the plexus before their subdivision
 caused the contraction of those muscles only which received filaments
 from them.*
   Termination of Nerves.—The connection which the terminal fila-
 ments of nerves  form with the proximate constituents of the striped
 muscle has been already described (p. 161).  From that description
 it  will appear  that the nervous  fibres do not come into  immediate
 communication with the sarcous substance, unless we have  recourse
                               to the supposition that some minute
                               elements proceed  from  those fibres,
                               and penetrate the sarcolemma. Such
                               a supposition has no foundation in
                               anatomy, so far as our present know-
                               ledge extends.   It is a curious sub-
                               ject  of  investigation  to  determine
                               what  becomes  of  the  nerve-tubes,
                               which,  after  the  formation of  the
                               loops which cross the muscular fibres,
                               take a retrograde course towards the
                               nervous  centre.   Do  they,  for  in-
                               stance,  return  to  the spinal cord?
                               and can it be their office to form a
                               second  connection with the vesicu-
                               lar matter of the cerebro-spinal cen-
                               tre, the descending fibre coming from
                               the brain, and the returningone being
                               implanted in  the gray matter of the
                               cord ?
                                 In the  skin  the  arrangement is
                               plexiform ; but  this is reducible to
                               loopings, as will be explained in the
                               chapter  on Touch.
                                 The arrangement of the primitive
                               fibres in loops has been also seen by
Henle on some parts  of  mucous membrane ; in the membrana nic-
 Terminal nerves on the sac of the second
molar tooth of the lower jaw in the sheep,
showing the arrangement in loops.— (After
Valentin.)
* Plexuum nervorum structura et virtutes.  Berol. 1836. 
SYMPATHETIC NERVES.
205
titans  of the  frog," for  example, and in the mucous  membrane of
the throat in the  same  animal.   A similar disposition has been de-
scribed and delineated by Valentin in the pulps of the teeth (fig. 60),
and we have seen it in the papilla? of the tongue.
   The so-called nerves of pure sense, the olfactory, optic, and audi-
tory nerves, may more  properly be regarded as portions of the brain
itself than as mere nerves, for they possess most of the  anatomical
characters of nervous centres.  The intra-cranial portion of  the first
is as distinctly compounded of vesicular and fibrous matter as a con-
volution of the brain.    In the peripheral expansion of the optic nerve,
the retina, it will be hereafter shown that the vesicular elements of a
nervous centre are as unequivocally present as in the olfactory bulb.
As regards the  auditory nerve, there are also  some grounds  for the
statement that the vesicles of gray matter are deposited  at  its peri-
pheral expansion in the internal ear.*
   Of the Ganglionic or  Sympathetic Nerves.—The composition of
these nerves is essentially si-
milar to that  of  the cerebro-                  Fig. 61.
spinal nerves.  They consist
of a  series  of nerve-fibres
bound together  by  areolar
tissue which forms their neu-
rilemma.   This  sheath  is,
however, denser than in  the
cerebro-spinal nerves, so that
the  nerve-fibres  are  more
difficult of separation, and
the fasciculated character is
not so obvious.  It consists al-
most entirely of white fibrous
tissue  longitudinally  dispos-
ed, which are crossed by some
fine circular  fibres of yellow
tissue, surroundingthe nerves
at various distances from each
other.   When a nerve is torn
up by needles, and treated by
acetic acid, numerous  small
oval cell-nuclei are seen  ly-
ing in and among the fibres,
with their long axes parallel
to the latter.
   The  sympathetic  nerves
contain   the  fibres of  both
kinds, the  tubular and the
gelatinous,  in very variable
quantity in  different nerves.
Thus, the former are numerous in the ramifications of the solar plexus
 Roots of a dorsal spinal nerve, and its union with
sympathetic :—c, c. Anterior fissure of the spinal cord
o. Anterior root. p. Posterior root, with its ganglion.
a1.  Anterior branch,  p'. Posterior branch  s. Sympa-
thetic,  e. lis double junction with the anterior branch
of the spinal nerve by a white and a gray filament.
* See further on these points the chapters on Smell, Vision, and Hearing. 
206
INNERVATION.
and in the cardiac nerves ; and the latter almost exclusively compose
one of the fascicles by which the sympathetic communicates with the
spinal nerves (fig. 61, e): they are so numerous, while the tubular
fibres are few, in the sympathetic cord in the neck.   In some nerves,
the tubular fibres are quite on the  surface ; and in  others, they are
enclosed in the axis  of  the nervous trunk.   It is  probable  that the
same change of place between the  fibres  occurs in  these nerves as
that which we have  noticed in  the cerebro-spinal nerves ; so that
those fibres which at one part of the nerve were superficial, would at
another be deep-seated,  and vice versa.
  The mode of branching of these nerves is essentially the same as
that  of the cerebro-spinal.  But the frequent formation of ganglia in
the course of the trunks, and of their ramifications, constitutes a re-
markable feature.  The  branches attach themselves to the exterior of
arteries, forming very intricate plexuses, which entwine around them,
"hedera? ad modum" (Scarpa).  Along these vessels the nerves are
conveyed to the tissues; but of the  mode  in which their filaments
connect themselves immediately with those textures we are at present
entirely ignorant.  The  ramifications of the  sympathetic seem to  be
limited to the trunk  and head :  it has probably no connection, or at
most a very limited one, with the extremities.
  The connection of the sympathetic system with the brain and spinal
cord appears to take place through the  cerebro-spinal nerves.   Cer-
tain  filaments connect each spinal  nerve to some portion of the gan-
glionic  chain which lies on each side of the spinal column.   And a
similar connection takes place between ganglia of the cephalic portion
of the sympathetic and the encephalic nerves, of which the following
may be cited as well-known  instances  :—The  third  nerve  is con-
nected with the ophthalmic ganglion ;  the  sixth with  the  superior
cervical  ganglion ;  the  fifth nerve  with  the spheno-palatine and otic
ganglia.   These connecting filaments have  been called the  roots of
the sympathetic ; and thus this nerve has been represented as taking
an extended origin from numerous points  of the cerebro-spinal cen-
tre.   This is true :  but, in dissecting  the  connection  between the
sympathetic  and the  spinal nerves, we find that, for the most part,
two  distinct fascicles  connect them, one  of which  is white, being
composed of tubular fibres ;  the other  is gray, and consists of gela-
tinous  fibres.   The  former  seem  evidently cerebro-spinal  fibres,
which pass to  or from  the periphery conjoined with the other  ele-
ments of the sympathetic : but, in the present state of our knowledge,
it is difficult to  form a  correct idea  as  to the precise  object of the
latter bundles,  or as to the central  connection which  they form, whe-
ther with the ganglion on the  posterior root of each spinal nerve, or
with the spinal cord.  That the sympathetic has intimate and  exten-
sive connections with the brain and spinal cord, is abundantly proved,
not only by the anatomical statements above detailed, but by the cir-
cumstance of which  every one is conscious, that pain may be excited
in parts supplied from this system of nerves alone, as in the intestines;
as well as by the fact that irritation of  the  spinal cord may produce
contraction of muscles which derive their nerves from this source, and 
THE NERVOUS CENTRES.
207
Fig. 62.
that destructive disease of that organ may occasion paralysis of those
muscles.
   Of the nervous  centres.—The nervous  centres exhibit to us the
union of the vesicular and the fibrous nervous  matter.   Indeed, the
association of these two forms of nervous substance in a mass of vari-
able shape or size is the main anatomical condition for the formation
of a nervous centre.   The former  is never  met with in  nerves pro-
perly so called, and when  a true nerve has a grayish appearance, we
find that it is owing to a paucity of the tubular, and an excess of the
gelatinous fibres.
   All nervous centres are provided with a proper covering which
serves to isolate them  from adjacent textures, and to protect them, as
well as to support their nutrient blood-vessels.   In the  ganglia this
covering is continuous and identical with the neurilemma of the nerves
which are connected with  them, and it is in every respect of the same
structure as the latter membrane.
   In  the larger centres, the brain and spinal cord, the coverings are
of a more complicated kind.  They are called meninges,  membranes.
Three of them are enumerated :  The  dura mater, which is external;
the pia mater,  which is in  immediate connection with the nervous
matter of the centre; and the  arachnoid membrane, a serous  sac inter-
mediate to the two tunics just mentioned, which is evidently destined
to facilitate the movements of these organs within their proper cavi-
ties.   These will  be more  particularly described
further on.
   In  examining the ganglia, we  obtain  a  good
idea  of the minute structure of nervous centres
in general.   A thin slice of one  of the larger gan-
glia, torn up by needles, or a small ganglion from
some small animal, serves to show  the disposition
of the vesicular and fibrous matter in these bodies.
   A ganglion may be  compared to a plexus, with
nerve-vesicles deposited in its meshes  (figs. 62,
63).   In tracing a nerve into a  ganglion, its com-
ponent  fibres  appear  to  separate, and  to pass
through the ganglion in different directions ; some
maintaining their  original course,  others  diverg-
ing from it for a short  way and  afterwards return-
ing to it, and  others taking altogether a new direc-
tion and passing out of the ganglion in combination
with  other fibres, to form an emerging nerve.   A
certain degree of  interlacement of the fibres thus
takes place within the ganglion, and in  its inter-
stices are lodged the nerve-vesicles enveloped by
their  proper sheaths.  A great  number of nerve-
fibres may be traced through the ganglion, so that
the emerging nerves may be regarded as resulting from a new com-
bination  of the fibres  that compose  the nerves which  entered the
ganglion.  These, however, are possibly not the only constituent fibres
of the emerging nerves, for it has yet to be ascertained whether some
   Second  abdominal
ganglion of the green-
finch, slightly compress-
ed.  The course of the
nerve-tubes only is re-
presented, a. l'ntering
fibres, b. Emerging fi-
bres, i. Outline of in-
vesting  tunic, beneath
which vescles exist.—
(After Valentin.) 
208
INNERVATION.
Fig. 63.
 A small piece of the otic ganglion of
the sheep, slightly compressed; show-
ing the interlacement of the internal
fibres, and the vesicular matter.—(Af-
ter Valentin.)
 fibres may not take their rise from  the vesicular matter of the gan-
                            glion, and it  is  a not less interesting
                            object  of inquiry whether some of the
                            entering fibres may not  terminate  in  it.
                            That the  nerve-tubes have  an intimate
                            connection with the elements of the ve-
                            sicular  matter is  apparent from the fact
                            that  they lie in  close  apposition  with
                            them, and appear to indent their sheaths
                            of nucleated  corpuscles (fig. 57).  Some-
                            times the sheath seems to taper off from
                            the nerve-vesicles, and to become  con-
                            tinuous with  the  nerve-tubes.  It is a
                            conjecture by no  means devoid of  pro-
                            bability, that the  processes of  the  cau-
                            date vesicle may, after passing some way,
                            become  invested  by the tubular mem-
                            brane and by the  white substance  of
                            Schwann, and  we have seen  some ap-
pearances to  warrant  this view  (see fig. 56,  c, d).   Yet  it should
be  stated, as  opposed  to  this view, that in the  gray matter of the
cerebellum the caudate vesicles are so placed that their processes pass
toward the free surface of the cortical layer,  and not into the white
matter.
  Besides the tubular fibres, the ganglia  contain likewise gelatinous
ones, which, however, are more abundant in the sympathetic than in
the cerebro-spinal ganglia  (fig. 58, g).  These fibres are, doubtless,
continuous with those  of the same  kind  which may exist in the en-
tering or emerging nerves.   We may also add, that  the vesicular
matter does not appear to be  confined to  the interstices between the
fibres, but is  likewise found at the surface of the ganglia,  lying in
immediate contact with their investing tunic.
  In the brain  and  spinal cord, there is a greater separation of the
vesicular and  fibrous matter than in  the  ganglia.   The former very
complicated organ, indeed, consists of various masses which are in
all essential points very similar to  the ganglia in structure, and doubt-
less also  in function : but its  hemispheres  are larger masses, of which
the interior substance is composed exclusively  of fibrous matter, sur-
rounded  by a layer of vesicular, which forms a rind or cortex to it.
The fibres of the former,  however, are  prolonged into this cortical
layer, and the intermixture of the two forms of nervous substance  is
thereby effected (fig. 57).
  The spinal cord is  composed of certain  columns  of fibrous sub-
stance, in which a large number of the fibres take a longitudinal
direction.  These, in a great  degree, enclose a distinct  arrangement
of vesicular matter, into which, however, as in the cortical layer of
the cerebral hemispheres, some, at least, of the fibres of the external
white matter are continued, intermingling  with  its elements.   It may,
therefore, be stated  generally that in the brain the vesicular matter
is external and cortical, and in the  spinal cord it is internal and al- 
DEVELOPMENT OF NERVOUS MATTER.
209
most completely surrounded by the white fibrous matter.   This dif-
ference of  arrangement is  probably to  be  ascribed to  the fact, that
throughout the whole course of the spinal cord nerves are being given
off, whilst from the encephalon they come only from certain regions.
In these regions the white matter is superficial; but in the hemispheres,
from which no nerves proceed, it is deep-seated.   We shall describe
more minutely the disposition of  the two kinds of nervous matter in
the cerebro-spinal centre at a future page.
Of the Nerves and Nervous Centres in Invertebrate Animals.
Fig. 64.
  The description above given applies to the  human  subject, and to the verte-
brate classes generally.  In all essential points, so far as the present state of our
knowledge  enables us to  judge, the structural arrangement of the nerves and
nervous centres of the invertebrate classes accords with this.   Some differences,
however, exist which require  to be noticed  here.  In the  lobster, the nerve-
tubes  are large; the tubular membrane has
the same  transparent, homogeneous  ap-
pearance,  which we have  noticed in the
vertebrata.  But  it encloses many delicate
nuclei at various intervals.  Within the  tu-
bular  membrane there is  a very thin layer
of the white  substance of Schwann.  The
nerve-tubes are  very  transparent,  and are
much larger than the average size  in verte-
brata.  Respecting the  existence or structure
of the gelatinous fibres, we can offer no  re-
mark.  In insects and myriapoda, the nerve-
tubes  vary considerably in  size: they are
collected  into bundles, and  are surrounded
by a  transparent  sheath  of homogeneous
membrane, which  accompanies  the  larger
ramifications of the nerve-trunks.  The white
substance of Schwann is not so obvious nor
so constant in  these nerves as in those of the
lobster, and the existence of nuclei (fig. 64)
makes them resemble closely the gelatinous
fibres of  the vertebrata.  The anatomical
characters of the vesicular nervous matter of
invertebrata do  not essentially differ  from
those of the same substance in the vertebrate
classes, so far as our observation enables us
to judge.  The  nerve-vesicles with nuclei and  nucleoli are equally apparent
in both, though in the former they are more transparent,  and contain less pigment.
0
  Nervous fibres of insects :—a. Trans-
parent sheath, b. Nerve-fibres, with oval
nuclei,  e. Shows the  bifurcation of the
sheath
0
   Of the development  of nerve-fibres.—We  can add nothing to the
account given  by Schwann of the development of nerve.   The fol-
lowing is quoted from  Dr. Willis's translation of  Wagner's  Physio-
logy :—
   " The nerves appear to be  formed after the  same manner as the
muscles, viz., by the  fusion of a number of primary cells arranged
in rows into a  secondary cell.  The primary nervous cell, however,
has not yet been seen with perfect precision, by reason of the diffi-
culty of distinguishing  nervous cells whilst yet in their primary state,
from the  indifferent cells  out  of  which entire organs are evolved. 
210
INNERVATION.
/
ff*=!v
 Various stages of the development of nerve :—a.
Earliest stage.  6. Detached fibre,  c. Nucleated fibre
in the lower part of which, rf, the white substance of
Schwann has begun to be deposited, e. Nucleus in a
more fully-formed fibre between the white substance
and tubular membrane, f. Displays the tubular mem-
brane, the contained matter having given way.—(After
Schwann.)
When first a  nerve can be distinguished as such, it presents itself as
                                     a  pale  cord  with a  longitu-
               Fig. 65.                dinal  fibrillation,  and in  this
                                     cord a multitude of nuclei are
                                     apparent  (fig.  65,  a).  It is
                                     easy to  detach individual fila-
                                     ments from a cord of this kind,
                                     as the  figure just referred to
                                     shows,  in the interior of which
                                     many nuclei are included, si-
                                     milar to those of the primitive
                                     muscular fasciculus, but at a
                                     greater distance from one ano-
                                     ther.   The filaments are pale,
                                     granulated,  and  (as  appears
                                     by their farther development)
                                     hollow.  At this  period, as in
                                     muscle, a  secondary  deposit
                                     takes place upon  the inner as-
                                     pect of the  cell-membrane of
the secondary nervous cell.   This secondary deposit is a fatty white-
coloured  substance, and it  is through  this that the nerve  acquires
its opacity.   This  is seen  in fig. 65 ;  superiorly, at c, the fibril is
still pale ; inferiorly, at d, the deposition of the white substance has
occurred, and its effect in rendering the fibril dark is obvious.  With
the advance of the secondary deposit, the fibrils become  so thick, that
the double outline of their parietes comes into view, and they acquire
a  tubular appearance.   On the occurrence of this  secondary deposit
the nuclei of the cells are generally absorbed; yet a few may still be
found to remain for some time longer, when they are  observed lying
outwardly between the deposited  substance and the  cell-membrane,
as in the muscles (e).  The remaining cavity appears to be filled by
a  pretty consistent substance, the band of Remak, and discovered by
him.  In the adult a  nerve, consequently, consists, 1st, of an outer
pale thin  cell-membrane,—the membrane of the original constituent
cells, which becomes visible, when the white substance is destroyed,
by degrees;  2d, of a white fatty substance deposited on the inner as-
pect of the cell membrane, and of greater or less thickness ; 3d,  of a
substance, which  is frequently firm or consistent, included within the
cells, the  band of  Remak."
   The  fully-formed vesicular  matter exhibits the  persistent state of
the cells of primitive development.  According to Schwann, the  only
change which the full-grown cell exhibits consists in an increase of
size, and in the  development  of the   pigmentary granules within.
According to Valentin's description, the following is  the process of
development of the  nerve-vesicles.   In the  very young embryos of
mammalia, as the sheep or calf,  the cerebral  mass in  the  course of
formation  contains, in the midst of a liquid and transparent blastema,
transparent  cells  of great delicacy with a  reddish-yellow nucleus.
Around these primitive cells, which we  find likewise formed after the 
              REGENERATION OF NERVOUS MATTER.           211

same type in  the spinal cord, a finely granular mass becomes  depo-
sited, which probably is not at first surrounded by an enveloping cell-
membrane.   At this early period of formation the  primitive cell still
preserves its first delicacy to such a degree, that the action of water
causes it to burst  immediately.   In proportion as the granular  mass
contracts itself within certain limits, a  cell-membrane probably  is
developed around it, so that the vesicle gradually  acquires the exact
form and size, and its  contents the  proper characters, which belong
to the fully-formed nervous corpuscle.
   Of the regeneration of nervous matter.—Our  chief knowledge  on
this subject is with  respect to the regeneration of  the tubular fibres.
Many years  ago  our countryman, Dr.  Haighton,  in making expe-
riments  to determine the functions of the vagus nerve, showed that
when  a nerve is simply divided,  without removing any  portion of it,
union would  take place,  and the nerve resume its  proper  office.   If
a  considerable piece  were  excised,  so  as  to  leave much interval
between the cut ends, there would be union after the lapse of  some
time, but not by true nervous fibres, nor in such a way as to restore
the  action of the  nerve.   It appears,  however, from recent observa-
tions,  of which  those of Schwann, Steinruch, and Nasse are the most
interesting, that true nerve-fibres may be  developed in this  uniting
substance, but apparently in smaller numbers than  in the nerve itself.
The proof of the regeneration of the true nerve-fibres depends upon the
restoration of the nerve's function, and the demonstration of the pre-
sence of proper nerve-tubes by microscopical examination.  Perfect
restoration of the action of  the nerve does not generally take place,
owing, most probably, to the fact that the central and peripheral por-
tions of the same fibres do not always meet again.  The central portion
of a motor fibre might unite with  the peripheral segment of a sensitive
one, and thus the action of each would be neutralized.
   Nothing satisfactory is known  respecting the regeneration of the
nervous matter of  the brain or spinal cord after a loss of substance
from  injury or disease.  When a portion  of the brain is removed in
animals, its place is supplied by new matter;  but, whether this be-
comes true cerebral substance, future research with good microscopes
must  determine.

  We refer on the subjects of this chapter to the various works on General Anatomy
quoted in former chapters, especially to  that  of Henle; to Midler's, and Wagner's
Physiology; to the articles Nerve, and Nervous  Centres, in  the Cyclop. Anat. and
Phys.; to the fourth vol. of Soemmering's Anat. by Valentin (German and French) ;
to Valentin, iiber den Verlauf und die letzten Enden der Nerven ; and to Bidder and
Volkmann, Die Selbstandigkeit des sympathetischen Nervensystem. Leipzig, 1842.
7'he researches of Bidder and Volkmann on the sympathetic  system are of great in-
terest, if further observation shall confirm them.  These authors describe the pecu-
liar fibres of the sympathetic as originating independently of the spinal cord or brain.
Their description of these fibres does not exactly accord with what  we have seen of
the gelatinous fibres, nor are we at present  prepared to express any decided opinion
respecting the accuracy of their observations, which are very favourable to the theory
of the independence of the sympathetic system. 
212
                         CHAPTER IX.

VITAL PROPERTIES OF NERVES AND NERVOUS CENTRES.--CLASSIFICATION
   OF NERVES ACCORDING TO THE VITAL ENDOWMENTS OF THEIR FIBRES.
   --STIMULI OF NERVOUS  ACTION, MENTAL AND PHYSICAL.--VIS NER-
   VOSA--ITS NATURE;  IS IT ELECTRICAL?

   Of the vital properties of nerves and nervous centres.—There  are
no textures  which exhibit such proneness to molecular change, under
the influence of their proper stimuli, as nerve and  muscle.  It  has
already been stated in  the first chapter (p. 69), that each of these  tis-
sues manifests its vital  action in a different, although a very analogous
way. Muscles, while they are capable of responding to other stimuli,
almost invariably act in obedience to that of nerve;  and the changes
which  muscular  contraction  produces  are  obvious  to our unaided
senses in  the shortening of the muscle, and in its greater thickness
and  hardness.  Even the  alterations in the condition of its sarcous
elements may be discerned  by the microscope, and have  been  de-
scribed at page 170.
   The changes, however, which take place in nerve, when in action,
are known to us only by the effects which they produce on the sentient
mind or on  muscular parts.   There  is no alteration in the physical
appearance  of the nerve or  its fibres, which can be detected by our
aided or unaided vision.  Yet, from the rapidity  with which stimuli
applied to nerves produce  their effects on  distant  muscular parts,
from the instantaneous cessation  of  these  effects  on the removal of
the stimulus, and the speedy renewal of them on its reapplication,  we
can refer the phenomena to nothing so wTell as to a molecular change,
rapidly propagated along the course  of the nerve  from the point of
application to the stimulus.   And in the instantaneousness of its pro-
duction, and the velocity of its propagation, we  may compare it to
that  remarkable  change in the particles of a  piece  of soft iron, in
virtue of which it acquires the properties of a magnet so long as it is
maintained  in a  certain relation to  a galvanic current; these pro-
perties being instantaneously communicated when  the circuit is com-
pleted, and  as instantaneously removed when it is broken.  A state
of polarity is induced in the particles of the nerve  by the action of  the
stimulus, which is capable of exciting an analogous change in other
particles, whether muscular or nervous ;  whence  results the peculiar
effect of the nerve's influence.
   Thus, if a nerve be distributed among muscular fibres in  the man-
ner described at a former page, it will be capable of exciting muscu-
lar contraction, and is properly a  muscular or motor nerve; and it is
so connected, at  its origin, with  the nervous centre,  that a change
there, whether  induced by mental or by physical influence, may be
readily communicated to it.   When  a  nerve is distributed upon an
expanded surface, as upon the skin or mucous membrane, or is other- 
ENDOWMENTS OF NERVE-FIBRES.
213
wise  favourably disposed for  the reception  of any physical stimulus
from without, it will propagate the change induced by such stimulus
to the nervous centre;  and this change in  the centre  may produce
an impression upon the mind, giving rise to a sensation ; or it may
affect a motor nerve connected with  the excited one or arising from
the nervous centre adjacent to it, and thus may indirectly excite mus-
cular movement.   When a nerve is capable  of acting in the former
way, it is called a nerve of sensation, or sensitive; when in the latter, it
is an excitor of a motor nerve.
   It is not necessary to suppose any intrinsic  difference of structure
in the nerves which are thus  capable of producing  effects so mani-
festly different.   The action of a nerve depends upon the nature of
its central and peripheral connections.  It cannot  be motor, unless it
be intimately connected with  muscles; nor sentient, if its relation to
the nervous centre be not such  as will  enable it to  affect the senso-
rium commune.  The terms  efferent  and efferent are only so far ap-
plicable  to  certain nerves, as they refer to  the  direction  in which
such nerves appear to propagate the change produced in them, or to
the position at which the effects of the  stimulation become manifest,
that direction having reference to the point  at which the stimulus is
destined to  act.   In a motor  nerve, the ordinary stimulus acts from
the nervous centre; but a mechanical or electrical stimulus affecting
such a nerve  at any part  of  its course  will cause contraction of the
muscles supplied by it below the point of irritation.  In the sensitive
or excitor nerves, the usual situation from  which the  stimulus acts
is at their peripheral distribution;  but at whatever point  a  sentient
nerve be stimulated, a sensation will be produced, which will be re-
ferred to those parts, and to those  only, to which the fibres irritated
are distributed;  and, wherever the stimulus be applied to an excitor
nerve, it will, with equal  effect, rouse its corresponding motor nerve
to action.  There are no good grounds for  supposing that the mole-
cular change consequent upon the stimulation  of a nerve is limited to
that part of the nerve which is included between the point stimulated
and  the centre, or the muscles, where the effect of the stimulation ap-
pears : on the contrary, it is not improbable, that, at whatever point
the stimulus be applied, the whole  length of the  nerve-fibre partici-
pates in the change.  This is not unlikely in the case of motor nerves.
For  a continued or violent irritation of a motor nerve in some part of
its course, causing spasm or convulsive  movement of the muscles it
supplies,  may be propagated along its whole length to the centre, and
may there give rise to irritation of neighbouring fibres, whether motor
or sensitive, exciting more convulsion and pain.  The phenomena of
many cases of epilepsy,  in which the fit begins with irritation of a few
muscles, may be referred to in illustration  of this position.  And it
is equally probable as regards sensitive nerves.   If the ulnar nerve be
irritated where it passes behind the  internal condyle, a sensation  of
tingling is excited, which  is referred to the  sentient surface of the
ring and  little fingers;  and if the  irritation  be kept up, the  skin of
those fingers becomes tender  to the touch, its sensibility being very
much exalted.  This fact cannot be explained unless upon the sup- 
214
INNERVATION.
position that the molecular change  in  the  nerve-fibres, produced by
the irritation, extends peripherad as well as centrad, exalting the ex-
citability of their distal extremities.
   At whatever part of their  course sensitive  fibres be irritated, the
same sensation will  be produced,  whether the seat of irritation be
the centre, the periphery, or the middle of their course, provided only
the same fibres are irritated in the  same  degree.   Nothing is more
certain than that an affection of the central extremity of the nerve-
fibres is sufficient to excite sensations precisely similar to those which
the excitation of the peripheral portion of the same fibres would pro-
duce.  Hence it is that a morbid irritation at the centre is frequently
referred to the periphery; and that  the sensation of tingling or formi-
cation, in  the  hand or foot, leg or arm,  becomes  an indication of
cerebral  or spinal disease.   The remarkable fact, that persons who
have suffered amputation will continue to feel a consciousness of the
presence of the amputated limb long after its removal, derives some
explanation from this doctrine.   Two  cases have lately come before
us, in one of which the arm,  in the  other the leg,  was amputated, so
long before as  forty years ; yet  each person had the sensation of his
fingers or toes as distinctly as immediately after the operation.   And
not only  is there, in such cases, the consciousness above referred to,
but likewise, when the principal nerve of the limb is irritated, the pa-
tient complains of pains or tingling, which he refers to the amputated
fingers or toes.
   It may be stated, in confirmation  of the view above  taken, that
in many  cases of complete paralysis of a limb from  cerebral disease,
the patient is not  conscious  of its  presence, and really feels as if it
did not exist.   We have known instances in which this unconscious-
ness has  been so  great, that  when  the paralyzed  part came in con-
tact with some sensitive portion of his body, the  patient for a time
believed it to belong to another person, or imagined it some entirely
foreign substance.   In such cases the  affection of brain necessary to
create the feeling cannot be produced  in consequence of the morbid
state of that organ.
   The distinction which  has been  made between nerves of common
and of special sensation, is indicated by the fact, that  while a stimu-
lus to the  forrner causes pain, that  to  the latter gives rise to a  pecu-
liar or special sensation, as of light, sound, or taste.  These nerves
are so organized at their periphery  as to be peculiarly adapted to re-
ceive impressions from  the agents  to  which they specially respond:
and in this, as well as in their  connection  with  some special part of
the great centre of sensibility,  consist  their main  anatomical peculi-
arities (see p.  69).
   The same law of nervous action  applies  to these nerves as to those
of common sensation.   Thus, their  ordinary mode of action  is to pro-
pagate to the centre impressions made  at the periphery ; but irritation
at any part of them may give rise to their peculiar sensation ;  and if
the brain be stimulated at the part  whence these nerves arise, similar
sensations are produced.  Such phenomena of vision and hearing, to
which the  term subjective has been applied, are familiarly known to 
THE NERVOUS FORCE.
215
practitioners, as not unfrequent forerunners of more serious symptoms
of cerebral disease. Muscse volitantes, ocular spectra, tinnitus aurium,
are instances of these phenomena, which, although of every-day oc-
currence, ought always to excite the attention of the medical man, as
indicating some departure from the normal state of the optic or audi-
tory nervous apparatus.  Pressure on the eyeball, a galvanic current
passed through it,* rotation of the body, are capable of giving rise to
similar  phenomena, by exciting the  retina, or the  central connec-
tions of  the optic  nerve.  A sense of giddiness, similar  to that pro-
duced by the means last named, is also a very common symptom of
cerebral affection  arising from a  disturbed  circulation,  or  from the
blood being defective  in  one or more  of its staminal principles, or
vitiated  by some morbid element.
   The nervous trunks as they exist in  different  regions  are usually
compound ; that is, they contain fibres of different endowments.   In
some situations, it is true, the fibres of one kind predominate so much
as to give the  trunk  the  physiological character which  belongs  to
them; but it likewise enjoys in a proportionate degree the functions
of those fibres, which  are few  in  number.   For example, the facial
nerve, or portio dura of the seventh pair, is called motor because it
is almost wholly composed of motor fibres; but it contains, besides,
in  very  much  smaller  number, some sensitive filaments, which it
probably derives from  anastomoses with  neighbouring nerves.   The
third, fourth, and  sixth pairs  of nerves may be quoted as of similar
constitution to the facial.   In the  ramifications of the fifth nerve, on
the other hand, the filaments  of sensation are predominant;  those  of
motion being much fewer, and  confined to the branches of its inferior
maxillary division.
   It is at the points of emergence of the roots of  the  nerves from
the nervous centres that we find the most complete isolation of func-
tion.  This is well exemplified in the spinal nerves and  in the fifth
pair.   These nerves  emerge  from their  respective centres by two
bundles  of fibres, of which one  is sensitive, the other motor; the for-
mer having almost always the distinctive features of greater size than
the latter, and of  having a ganglion formed  upon it.  But, even in
these instances, it  has lately been made a matter of question whether
the  smaller root,  which experiment  has satisfactorily shown to be
motor in its function, does not also contain  a very slight proportion
of sensitive filaments.
   The stimuli by which the action of nerves is ordinarily provoked
are of two kinds, mental and physical.  In all voluntary actions, an act
of the mind is  the excitant of the nerve.   Sensations are caused by
the influence of physical agents upon nerves, which communicate with
the sensorium commune.  The change in the  nerve, by reason  of this
communication, gives rise to  a  corresponding affection of the mind.
It is wonderful how quickly such  changes are propagated, and with
what precision they are perceived by the mind, although the physical

  * A strong sensation of a flash of light may be  produced by passing a galvanic
current in the close vicinity of the eyeball. 
216
INNERVATION.
excitant may itself be a fine point invisible to the naked eye, applied
with the slightest force,  and coming in contact with a spot equally
difficult  of  appreciation.   If the  communication between the nerve
and the  centre be cut off", the will can exert no  influence  upon the
muscles supplied by the nerve below the  section; nor will the mind
perceive any stimulus applied to parts which derive their nerves from
it below the separation.   And the reason is obvious;  the solution of
continuity of the nerve interrupts the propagation of the change which
the mental or physical stimulus excites in it.  In the case of the vo-
luntary nerve, the mental stimulus is propagated  no further  periphe-
rad than the point of section: and in that of the sensitive nerve, the
change travels no further  centrad than the same point.   That the in-
terruption is caused  solely by the solution  of continuity, and not by
any alteration in the properties of the nerve, is proved by the fact that
the lower segment of the motor nerve will  still continue to respond to
a physical stimulus.   Mechanical  or chemical irritation, or  the pas-
sage of an electric current across it, will cause its muscles to contract.
Such  a degree of injury to a nerve as will destroy the continuity of
the nervous matter within the tubular fibres is  likewise sufficient to
destroy its power as  a propagator  of nervous change.  This effect
will be produced by tying a ligature very tightly round a nerve, or
by pressing it very forcibly between  the blades of a  forceps.   The
paralysis which results from the compression of a nerve by a tumor,
or in  any other way, is no doubt due to a  similar solution of conti-
nuity  in the nervous matter.
  From these facts  we draw the  important inference that, in propa-
gating the  influence  of a  stimulus, either from  periphery to centre,
or vice versa, nerves are not mere  passive conductors.   The whole
extent of the fibre between the point stimulated and its peripheral
or central connection is the seat of change.   How necessary, then,
to the normal action of nerves must it be  to preserve their physical
condition in a healthy state !  A morbid fluid impregnating  a nerve
at any point  may irritate it, or may suspend or  destroy its inherent
property by modifying its  nutrition.  It is thus, likewise, that nerves
may be paralyzed by soaking them in a solution of opium,  or of bel-
ladonna, aconite, tobacco, or other  powerfully  sedative or  narcotic
substances,  or that  they may be  unduly excited by applying a solu-
tion of strychnia. The contact of a solid body with a nerve may irri-
tate and keep up a continual state of excitement, if  it do not destroy
its properties.  A spicula of bone in  contact with nervous fibres is
often  the cause of the severest forms of neuralgia.   That alteration
of nutrition which we call inflammation  may produce  like effects.
Various physical agents are followed by similar  consequences.   The
benumbing influence of cold is explained in this way.  Exposure to
a continuous draught of cold air is a frequent cause  of facial paraly-
sis.   How instantaneously will  the giving  way of a carious tooth
occasion toothache by exposing the nerves of its pulp to the irritating
action of the air, or of the fluids of the mouth !   And  heat is equally
injurious to the physical constitution, and consequently to the action,
of nerves. 
THE NERVOUS FORCE.
217
  The organic change, whatever be its intrinsic nature, which stimuli,
whether mental or physical, produce in a  nerve, develops that won-
derful power long known to physiologists by the  name vis nervosa,
the nervous force.  This force is more or less engaged in the play of
all the vital functions, whether organic or animal.   In the former its
office is to regulate, control, and harmonize, as will be hereafter  ex-
plained ;  in the latter, it is the main-spring of action,  without which
none of the phenomena can take place.  It is the natural excitant of
muscular motion, and the  display of  that wondrous power depends
upon its  energy.   Unless there were vigour in the development  and
application of the nervous force, a well-formed muscular system would
be of little avail,  for it would quickly suffer in its nutrition if deprived
of that exercise which is so necessary to it.
  Although the workings of the mind are  doubtless independent of
the  body, experience convinces  us that  in  those  combinations of
thought which take place in. the exercise of the  intellect, the nervous
force is called into play in  many a devious track throughout the in-
tricate structure of the brain.   How else can we explain the  bodily
exhaustion which mental labour induces?  The brain often gives way,
like an overwrought machine, under the long-sustained exercise of a
vigorous intellectual  effort; and many a  master-mind of the present
or a former age has, from this cause, ended his days "a driveller and
a show."  A frequent indication of commencing disease in the brain
is the difficulty which  the individual feels in "collectinghis thoughts,"
the loss of the  power of combining his ideas, or impairment of me-
mory.  How many might have been  saved from an  early grave or
the madhouse, had they taken in good time the warning of impend-
ing danger which such symptoms  afford!   The delicate mechanism
of the brain cannot bear  up long against the incessant wear and tear
to which men of great intellectual powers expose it, without frequent
and  prolonged periods of repose.  The precocious exercise  of"  the
intellect in childhood  is frequently  prejudicial to its acquiring vigour
in manhood, for the too  early employment of the brain  impairs its
organization  and  favours the development of disease.  Emotion,
when suddenly or strongly excited or  unduly prolonged, is most  de-
structive to the proper texture of the brain, and to the operations of
the mind.  Our lunatic hospitals afford many examples  of men,  the
working  of whose minds has been wholly or partially destroyed by
the shock which a sudden reverse of fortune, or the loss of some near
and  dear  relative, may have occasioned.   Constant or frequent  ex-
cesses in the use  of ardent spirits may probably be thus injurious in
two  ways; first, by the direct influence of the alcohol on  the cerebral
fibre itself, producing  a chemical alteration in the nervous substance;
and secondly, by the frequent mental excitement which the use of such
a stimulus induces.
  Can we form any conception of the nature of this wonderful power,
which  is  so  intimately connected  with the functions  of  our bodies
and  with the working of our minds?  That it presents  many points
of resemblance to electricity, a comparison of the laws of these two
forces leaves no room to  doubt; although there are abundant reasons
     15 
218
INNEIt VATION.
for questioning  their identity.  The comparison  may be  best insti-
tuted between the nervous power and the force of voltaic electricity,
or current affinity, as it has lately been called, which is developed in
the galvanic battery.  For the production of this force  the ordinary
requisites are two  dissimilar metals, and an interposed compound
liquid.   When the metals  are brought into contact with each other,
a chemical  action immediately commences, and an  electric current
sets in a definite direction, namely, from the  metal which exerts the
greatest affinity for one of the elements  of the  interposed liquid to-
wards the other metal.   Thus if zinc, platinum, and  dilute sulphuric
acid be used, the fluid is decomposed ;  its oxygen is attracted to the
zinc,  which being oxidized and uniting with sulphuric acid, sulphate
of zinc is rapidly formed, and dissolved as quickly as formed, in the
liquid;  its hydrogen is evolved at the platinum.   So long as there is
fluid for decomposition, and  so long as contact between the metals is
maintained, these phenomena will continue.  During  the continuance
of  these chemical actions, the metals as well as the interposed  fluid
are supposed to be in a peculiar molecular condition, upon which the
development of force in a current form depends.   Commencing from
the immersed portion of the  zinc, each  particle, whether of metal or
fluid, communicates its peculiar state to that which succeeds it,  until
the whole circuit, from the zinc through the  fluid to the platinum,
and back again to  the zinc, is in the same state, one, namely, of
polarity  or  electrical tension.  A similar state may be induced in
glass, sealing-wax, &c,  by friction;  or in two  dissimilar metals in
intimate contact, by heating them at the place of junction; or in one
metal, as a coil of  platinum wire, by heating  it unequally (thermo-
electricity).  The simple  contact, indeed, of two  plates of different
metals with perfectly clean surfaces is sufficient to excite a state of
polarity in each.
   In the development of the galvanic current in the battery, one plate
or metal may be regarded  in the  light of the generator of force, the
other as its propagator or conductor.  The former has therefore been
called the positive, the latter  the negative pole.  The absolute contact
of the metallic  plates  themselves is not necessary.   It will suffice if
they be connected by any material which is itself capable of serving
as  a  conductor.   A piece of platinum wire, for  instance, extended
between the two  plates, although it actually connects only a  very
small portion of the  surface of each, will answer the  purpose.  From
such an arrangement it may  be concluded that, during the develop-
ment of the galvanic current,  the conducting metal is in a state similar
to that of the generating plate, for the temperature of the conducting
wire is  raised considerably; and, when there is much energy of action,
the wire is melted.
   The existence of a galvanic current is readily detected, even when
of feeble intensity, by  certain phenomena, which  are now  familiar to
those who conduct such  investigations.   If the  poles of a battery be
connected by conducting wires with  a  delicate galvanometer  (elec-
tro-dynamic multiplier),  the needle is obviously deflected during the
passage  of the  current,  and  returns  to  its previous position when- 
          NERVOUS AND ELECTRICAL FORCES COMPARED.       219

ever the  current is interrupted.  By making  and breaking the con-
nection, in rapid succession, the needle moves to and fro with corre-
sponding  rapidity  and energy.  So  delicate is this  test of  galvanic
action, that it will  detect even the very feeble current which results
from the heating of two dissimilar metals, or from the partial heating
of a coil of platinum wire.  As this is the most delicate test, so is it
also the most constant, and it  has the  additional advantage of ena-
bling the  observer to judge of the direction  of the current from the
position which the needle assumes under the electric influence.
   When a galvanic  current is made to pass through certain liquids,
as dilute sulphuric acid, solution of iodide of  potassium, of sulphate
of copper, &c, it  induces such  an amount of  disturbance of the at-
tractions existing in  them as to cause their decomposition, and give
rise to chemical actions of a similar kind to  those which take place
in the generation  of the current (electrolysis).   This, therefore, be-
comes a test of the presence of galvanic action.   The decomposition
of iodide of potassium will detect the existence  of a current deve-
loped by a  single  pair of plates, and iodine will be set .free at the
positive pole.
   Further tests of the presence of galvanic action are found  in the
magnetization of a steel needle placed within  a coil  of  wire through
which the current  is made to pass; and in the evolution of  heat and
light, which takes place when the  circuit is  completed or broken.
This latter effect, however, does not occur from currents of very fee-
ble intensity.
   Let us inquire how far the phenomena of the nervous force corre-
spond with those of this current electricity, and  whether it will respond
to any of the tests just described.
   It has already been remarked that the instantaneousness with which
nervous power is  developed,  when a mental or physical stimulus  is
applied to a nerve, resembles  remarkably the  rapid evolution of the
galvanic force throughout the  whole  circuit, the instant the necessary-
contacts are completed.  And both cease with equal rapidity when
the conditions for their production are  destroyed.
   Some analogy is  apparent  in the conditions  which  are  requisite
for the development  of both forces.  The  dissimilar metals and the
interposed fluid, which we have seen to be necessary for the produc-
tion of the galvanic  force, may have as analogues for  the develop-
ment of the polarity  of nerves, the two kinds  of nervous matter (the
vesicular and  fibrous), and  the blood.  Nervous power  is never
developed from a centre without the conjoint  action  of these two
kinds of nervous matter. The analogy fails, however, when we com-
pare  the relation of  the  metals in the  battery with that of  the gray
and white matter in  the nervous centre.  The former need not have
any connection but such as a conducting wire  of ever so minute  di-
mensions passing from one to  the other is capable of  effecting;  that
is to  say,  union of  a few points of one  metal with as many of the
other, is sufficient  for the generation and  transmission of the polar
state.  In the nervous centres,  however, the points of contact are pro-
bably most numerous.   The vesicles of the gray matter certainly are 
220
INNERVATION.
brought most extensively into connection with the nerve-fibres; and
there is much to justify and  confirm  the  opinion  that each  fibre is
connected with a vesicle, and that each vesicle, at least of the cau-
date kind, may be regarded as the point of departure of one or more
fibres.   If such an arrangement exist, we may regard each  nerve-
vesicles, and the fibres emerging from it, with the blood-vessels which
play around it, as a distinct apparatus for the development of nervous
polarity.
  There appears to be a provision for the insulation  of  the central
axis of each nerve-fibre in the white substance of Schwann; but there
is no such arrangement for insulating  the  vesicles.   In like manner,
we can insulate the galvanic  current by covering the conducting wire
with silk, or some other  non-conductor, and thus  cause it to pass
through an indefinite  length of wire disposed in coils, or through any
number of separate wires disposed parallel to each other,  which may
be brought into connection with the metals.
   These remarks are  clearly most applicable to those nervous actions
which emanate^/rom  a  centre.  But in those in which the nervous
force is propagated to a centre, as when pain is excited by touching
a nerve, or in the excitation of the  motor nerve  of an  amputated
limb by artificial stimuli, the analogy  of the mode of its development
with that of the  galvanic  force is not so obvious.  Still, when we
remember how7 easily thermo-electric currents may be excited by the
disturbance of the equilibrium  of heat in a wire  of even a single
metal, it seems not unreasonable  to  refer this excitability of nerve
to some similar proneness to  change in it.
   Nothing is more certain  than that a very slight mechanical or che-
mical  stimulus to a nerve, whatever be its proper vital endowment,
is capable of producing in it that state of polarity on which we sup-
pose the manifestation of nervous force to depend;  and it seems  not
incorrect to imagine that, in the battery, the point of departure of the
galvanic action may  either be  at the poles or  at  the  battery itself,
according to the  place at which the completion of  the circuit takes
place;  thus affording a more marked analogy to the two  kinds of
nervous actions above  referred  to.  Thus the conducting wires may
be in contact with each other, and with their respective metals; but,
if there be  no fluid interposed, there  is no action.   The instant  the
fluid is added, the current  begins; and in this case its point of depar-
ture may be regarded to be from the battery—in analogy with those
nervous actions which proceed from the centre.   On the  other hand,
the arrangements  of the battery  itself may be perfect, but action will
not begin  until the circuit is  completed by bringing the conducting
wires  into  contact.   In this case, the polar change may be said to
commence  at this point of contact, and to travel to the battery, in  a
manner analogous to  that in which nervous action is propagated from
the periphery to the centre.  In both  cases, moreover, so long as gal-
 vanic action continues, the whole apparatus is in the polar state:  and
 so long as nervous action continues, the particular nervous apparatus
 involved (vesicular matter and nerve-fibre) must be considered to be
 in a state of polarity  through its whole extent. 
NERVOUS AND ELECTRICAL FORCES COMPARED.      221
  Thus far we remark unquestionable analogy in the mode of deve-
lopment  and  of  propagation  of  the  electrical and nervous forces.
We must not, however, omit to notice the following points in which
the analogy does not  hold  good.  In the development of nervous
power,  there  is nothing, so far  as our present anatomical  know-
ledge enables us to decide, resembling that completion of  the circuit
which is the necessary prelude to galvanic action, or the interruption
of it which is followed by the cessation of  that action.  The mental
or physical stimulus, which  must be regarded as a necessary element
in every nervous  action, stands  in lieu of the former; but  how it
could accomplish the completion  of a  nervous circuit is a question at
present involved in the greatest  obscurity.   It is, indeed, a favorite
notion with  some, that  the looped arrangement of  the  peripheral
nerve-fibres,  in muscles and on some sentient surfaces, forms part of
a nervous arc, which is completed at the centre ; nor is it  impossible
to conceive a mechanism by which the completion  or interruption
necessary for the  development or the  stoppage of the  nervous power
might be accomplished.  But it would be hazardous to speculate  on
such  a subject until anatomical  research has revealed to us more
information respecting the exact disposition of the  elements of the
vesicular matter.
   The gelatinous fibres appear to want the provision which we have
noticed in those of the tubular kind for insulating the  nervous power.
They supply  the unstriped muscular fibres, which probably require a
stimulus less definite, as well  as of less intensity, than that necessary
to excite and  regulate  the action of the striped fibres.   This difference
of character in the conducting fibres is worthy of note in making com-
parison between the respective modes of action of the nervous and
electric forces.
   We come now to inquire  whether, by means of  the ordinary tests
for electricity mentioned in a former page, we can obtain any evidence
of  the identity of  the  nervous and electrical forces.   The results of
experiment certainly afford no support to the advocates of the elec-
trical theory  ; and indeed it will  be seen that there are difficulties in
the way of obtaining  the necessary conditions for a  satisfactory  re-
sult, which of themselves invalidate the experiments which have been
reported to prove favourable to that theory.
   Attempts have been made to  affect the galvanometer by bringing
 the nerves of living animals into connection with it.   This is done
 by inserting  wires into the exposed nerve, and  attaching their oppo-
site extremities to  the galvanometer.   When the  nervous power is
excited so as to cause muscular contraction, the  needle, it is said, is
deflected.*   The  experiment, however, has failed in the hands of
Prevost and   Dumas, who are advocates of the electrical theory, as
well  as in those of Person, of Muller, and of Matteucci; and on seve-
ral trials we  have  been unable  to observe the slightest  movement
of the needle.  Person  connected the wires of a galvanometer with
the surfaces  of the spinal cord in kittens and rabbits, in which spas-
• David, quoted by Muller, p. 685. 
222
INNERVATION.
modic action of the muscles had been excited by the influence ofnux
vomica, and could not discover any evidence of electrical action.  It
has been also affirmed that needles introduced into the nerves of a liv-
ing animal become magnetic, so as to attract iron filings.   No  such
result, however, could be obtained by Muller, or by Matteucci,  from
their repetition of these experiments.  The latter philosopher took the
precaution of  employing astatic needles  for the  purpose, but could
discover no trace of magnetization.  He also introduced the prepared
limbs of a frog into the interior of a spiral covered on its inside  with
varnish: the extremities of this spiral were united to those of another
smaller spiral, into which  he  introduced a wire of  soft iron.   The
nerves of the frog were irritated to excite  muscular action, and at the
same time Matteucci sought to  ascertain if an induced current would
traverse the spirals, and magnetize  the wire.  But, he adds, all his
endeavours were useless.
  No one has tried to  obtain a spark from a nerve during its action,
as a test of the electrical nature of the nervous power. Nor have any
experiments been devised  with a view to ascertain wThether decom-
positions similar to those which occur  in electrolysis may be effected
by it.  The separation of certain elements from the blood, in the  vari-
ous secretions, has, indeed, been attributed to a  kind  of electrolytic
influence of the nerves upon the  secerning organs.  But it has  been
proved that the secretions may go on to a considerable extent inde-
pendently of nervous influence, and it seems highly probable that the
nervous system can affect the  act of secretion only through its influ-
ence upon  the  blood-vessels of the secreting organ.
  But even were it certain that an electrical current  passes along the
nerve-fibres during nervous action, it  does not seem likely that the
required evidence of such a current could be obtained from any of
the experiments above detailed.  For if the nerve-tubes are to be re-
garded as insulated conductors, of which  the central axis is the active
portion, and the white  substance  of Schwann merely the  insulator,
sinking a needle between these  fibres will  not  obtain that contact
with the true  conducting  material which  is necessary to  affect the
galvanometer.  Let it  be remembered that  these nerve-fibres are  of
microscopic size ; and  that, when a needle is sunk into a bundle of
them, it does not pierce the nerve-tubes, but passes in between them,
and is separated from their central axes by the  insulating structure.
And were the electric current, passing through such  minute conduct-
ors as nerve-fibres, of sufficient intensity to magnetize a needle, it is
scarcely possible to conceive that it would be completely or perfectly
insulated by the delicate membranes which  invest the central  axis.
Yet, without some provision for very complete insulation of the seve-
ral conductors  in such a bundle as a nervous  trunk, it  is  obvious
that disturbances must  continually arise  from the secondary  currents
induced in neighboring fibres by the electricity passing through those
in action.
  The proofs, therefore, of the passage of an electric current through
the nerve-fibres during  nervous action must be held to be altogether
defective.  Not only is  experimental evidence wanting to support the 
ANIMAL ELECTRICITY AND LUMINOUSNESS.        223
electrical theory, but certain facts are  admitted  which greatly inva-
lidate it.  Of these, a very important one has been adduced  in the
preceding paragraph.   The following may be added, some of  which
have already been adduced by Muller.
   1. The firm application of a ligature to a nerve stops the propaga-
tion of the nervous power below the points of application, but  not  of
electricity.   The nervous trunk is as good  a conductor of  electricity
after the application of the ligature as  before it.
   2. If a small piece of a nervous trunk be cut  out, and be replaced
by an electric conductor, electricity will  still  pass along the  nerve,
but no nervous force, excited  by stimulus above the section, will be
propagated through the conductor to the parts below.
   3. Nervous fibre is not a better conductor of  electricity than other
tissues.   Matteucci assigns to muscle a conducting power  four times
greater than  that of nerve or cerebral matter;  and Weber  states that
no substance in the human body is so good a conductor as the metals.
From our own observations on this subject, made with the most deli-
cate instruments,  we are led to  state that both nerve and muscle are
infinitely worse conductors  than  copper, and that we have failed  in
detecting any appreciable difference in the conducting power of these
two animal substances.  In fact, their power of conduction does not
rank above that of water holding in solution a small quantity of saline
matter.
   From the  preceding  review of the arguments for and  against the
theory of the identity of the nervous force and electricity, we  are led
rather to reject than to  adopt it.  The same reasons induce us to re-
gard the nervous force as a power developed in  the nervous structure
under the influence of appropriate stimuli; as muscular force is deve-
loped  in  muscle  under similar  influence.   Both tissues are charac-
terized  by their tendency to assume a  polar state, different in each,
although  analogous,  in obedience to certain excitants.   That this
                                                     ill
polarity bears a remarkable analogy to that which may be produced
in inorganic matter is evident.   Further  observation and research
conducted with a full  knowledge of the details of anatomy, as  well
as of the laws of the polar forces, as displayed in  inorganic  sub-
stances, will doubtless throw great  light on this intricate subject;
for, as Faraday remarks, if there be reasons for  supposing that mag-
 netism  is  a  higher relation of force  than   electricity,  so it may well
be imagined that the  nervous  power may be of a still  more exalted
character, and yet within  the  reach of  experiment.   (Phil.  Trans.,
 1839.)
    Of the electrical fishes.—The  fact that some fishes possess a pecu-
liar electrical apparatus, which they are  enabled to discharge under
voluntary influence, is  supposed by the adherents of the electrical
theory to favour  their views.   The torpedo, the gymnotus electricus,
or electrical eel, and  the silurus electricus, are the best known of the
electrical fishes.   From the two former, the most unequivocal  evi-
dence has  been  obtained  by Walshe, Davy, Linari, Matteucci, and
recently by Faraday,  that  electricity is  discharged.  Conductors  or 
224
INNERVATION.
non-conductors are affected by the electrical apparatus of these fishes
just as by ordinary electricity: a chain of several persons, of whom
those at the extremities touch the fish, feel the  shock as they would
that of a Leyden jar.   The  sensation  produced by the shock  from
the fish is exactly that which is caused by accumulated electricity as
developed  by the  ordinary  machine.  A spark has  been obtained
during the  discharge: chemical decomposition or electrolysis has been
effected by it.  The galvanometer is  also readily disturbed, and  indi-
cates  that the current passes from  the  anterior to the posterior part
of the animal.   And a needle has been made a magnet when placed
in a helix through which the current passes.  These effects have  been
obtained from the torpedo and the gymnotus.
   It is further shown  that the electricity cannot be developed in
these animals if the organ be removed, or if its communication with
the brain be cut off.  If the nerves of  the organ of one side  be cut,
it will cease to develop  electricity ; but the opposite organ will con-
tinue  to  act perfectly.   When the organ is partially cut away, the
remaining portion continues to  discharge; or,  if  some of its nerves
be cut, that portion of which the  nerves  are entire will continue to
develop electricity.   The nerves excite  some  change in the organ
which causes the development or discharge of electricity, but no traces
of an electrical current can be detected in the nerves themselves.  If
the nerves  of an electrical organ be cut,  irritation of those segments
of them which adhere to the organ will excite discharges, just as the
irritation of muscular nerves under similar circumstances will cause
contractions ; or  direct irritation of portions of the  organ itself will
produce discharges (Matteucci). Any general excitation  of the nerv-
ous system will cause discharges; thus  strychnine, while it  throws
the muscular system into  spasms, provokes frequent and violent dis-
charges of the electrical organs.
  From these observations it seems  impossible to adopt any other
conclusion  than that the  electrical organ is the generator of the  elec-
tricity ; or,  at least, that it may collect  and accumulate  the  electri-
city generated all over the body in the ordinary nutritive  processes.
This latter  opinion, however, is rendered unlikely from the imperfect
conducting power of animal substances, unless further research should
develop  some channels by which electricity generated at a distance
might be conveyed to the electrical  organ.   Whatever view of the
case be adopted,  it  is difficult to discover in  the  facts above stated
respecting the electrical fishes any support to the electrical theory of
nervous power.  On the  contrary, the very existence of a peculiar
organ for the specific purpose of generating electricity would appear
adverse to such a doctrine.   Were the nervous centres the source of
electricity,  surely an arrangement, of a less complex character, and
deviating to a less extent from the natural structure of other fishes
of the same genus,  would have sufficed for the manifestation of the
peculiar power of the electrical fishes.
  Some insects  (the  glow-worm for instance), and other creatures,
possess the  faculty of generating light.   The power resides in a par-
ticular organ, and is regulated by the nervous  system.   It is strik-
i 
THE NERVOUS SYSTEM IN VERTEBRATA.         225
ingly analogous to that by which electricity is developed.  Yet no
one would assign the nervous system  as the source of the luminous
emission.  Nor are we justified in affirming from the one instance
that  the nervous  power  is  electricity, any more than we should,
from the other, be authorized in  asserting that  the  nervous power  is
light.

  On the subjects discussed in this chapter, reference is made toMuller's Physiology
byBaly; Daniell's Chemistry; the articles " Animal Electricity" and " Animal Lu-
minousness," in the Cyclop. Anat. et  Physiol.; Matteucci, Traite des  Phenomenes
Electrophysiologiques des Animaux.
                         CHAPTER  X.

ARRANGEMENT OF THE NERVOUS SYSTEM IN VERTEBRATA.--IN INVERTE-
   BRATA.--NERVOUS CENTRES IN MAN.--THEIR COVERINGS OR MENIN-
   GES.--THEIR VENOUS SINUSES.--THE SPINAL CORD.--THE ENCEPHA-
   LON.--THE CIRCULATION WITHIN THE CRANIUM.

   The leading subdivision of the animal kingdom into Vertebrate and
Invertebrate  animals is  so  obviously sanctioned  by the  disposition
of the nervous system peculiar to each, that  no naturalist hesitates
to adopt it.  In the vertebrate  animals, an osseous or cartilaginous
column,  composed of separate pieces united by amphiarthrosis, forms
the principal support and bond  of connection for the other  parts of
the trunk.  This column encloses a canal, within which  is placed
that portion of the nervous centres called the spinal cord, or marrow,
with some of its nerves.  At its anterior or upper extremity, the com-
ponent pieces of the column are so modified  as to  form a dilated
cavity, the cranium, in which another portion of the central nervous
system, the brain, or encephalon, with part of the nerves  connected
with it, is contained.   In the invertebrate animals generally there is
no internal skeleton, if we except the slight traces which exist in the
cephalopodous mollusks; but in many of them a modification of the
external  integument affords  the requisite amount  of protection and
support  to the soft  tissues  and  organs.  The  nervous system, the
central part of  which is disposed either in detached  masses, or in a
series along the abdominal surface of the animal, receives no special
protection from this external  skeleton.
   The brain  and spinal cord, in the vertebrate classes, form a central
axis with which all other parts of the nervous system are connected.
The former  is  evidently  an aggregate  of gangliform  swellings,
each possessing the characters of a  nervous  centre, but  so con-
nected with the others, that  their functions are in  no small degree
mutually dependent.   The latter has throughout its entire length all
the characters of one uniform  nervous centre, of cylindrical shape ;
but experiment has shown that, if divided into  segments,  in animals 
226
INNERVATION.
tenacious of vitality, each  portion  may exert  an  independent influ-
ence on that  segment of the body whose nerves are connected with
it.   From this fact we may properly regard the cord also in  the light
of a  ganglion cotnpounded of smaller ones, which have been, as it
were, fused together.   And certain anatomical  indications in  the
lower animals, as well  as  in  man, favour  this view ;  thus,  in the
common gurnard {trigla lyra), there is a series of  gangliform swell-
ings situate on  the  posterior  surface of  the  cervical  portion of the
cord at its upper part, from  which large nerves pass off to the feelers;
and in all animals the cord  exhibits a  distinct enlargement, at each
segment with which large nerves are connected, or a  contraction, if
the nerves be of  small size and of  comparatively little physiological
importance.
   The cerebro-spinal axis,  with the nerves  pertaining to it, consti-
tutes the greatest portion of the nervous system of the  human  sub-
ject and of the vertebrate  animals.  The sympathetic system, how-
ever, is  connected with  a large number of those parts on which the
principal organic  functions depend.  This  portion of  the  nervous
system always bears a direct relation in point of development to that
of the cerebro-spinal portion, with every part of which it is  very in-
timately associated.   If  we except the  olfactory, optic, and  auditory
nerves, there is no nerve with  the origin of which it does not form a
connection.   Its segments remain  separate, as distinct ganglia, con-
nected, however, by  intercommunicating cords  passing  from one to
the other, by which the  continuity of the chain  on either side of the
vertebral column is maintained.   In mammals and birds the sympa-
thetic is fully developed; but in some reptiles and fishes it  is partly
deficient, and its  anterior part  which is wanting, is supplied by the
vagus nerve.  In  the cyclostomatous fishes, as the lamprey, it is want-
ing altogether, and the vagus seems to supply its  place.  In no animal
is it so fully  developed as in man.
             Arrangement of the Nervous System in Invertcbrata.

  It is foreign to the purpose of this work to  enter into details of comparative ana-
tomy.  The following paragraphs are  merely intended to call the reader's atten-
tion to the general plan of the nervous system  in the Invertebrata. The arrange-
ment adopted is that suggested by Professor Owen.
  The Invertebrate animals maybe classed in three groups, according to the pre^
vailing type of arrangement of the nervous system.  1. The first, or Ncmatoneurose,
exhibits no other trace of nervous system than is to be found  in  simple threads
or filaments. In the  asterias, one thread surrounds the  mouth, and others pass
from it to the rays;  and in the strongylus  gigas, a slender nervous ring sur-
rounds the upper part of the gullet, and from it a single thread is continued along
the ventral surface to the opposite extremity, where another nervous loop is found
surrounding the anus.  No distinct evidence of the existence of ganglia in animals
included in this group has been obtained.   It would be  premature, however, to
suppose that the absence of gangliform swellings implies that of vesicular nervous
matter.
  2.  The second group of animals is designated Heterogangliate, from the unsym-
metrical disposition of the nervous system.  The principal portion of it consists
in a ring surrounding the gullet, on which one or more  ganglia are placed.  In
the ascidia mamillata there is but a solitary ganglion, which regulates the orifices 
THE DURA MATER.                       227
of ingestion and egestion by nerves which it  sends to their respective sphincter
muscles.  And in all the other classes of mollusks the nervous system is the more
complex, as the kind and number of the vital actions demand a higher degree of
organization.  In conchifera, for instance, ingestion  of the food, respiration, and
locomotion have  distinct organs assigned to them, and accordingly the nervous
system is so disposed that there is a nervous centre  or ganglion in immediate
relation to the principal organs connected with each of these functions.  Thus, in
the more perfect animals of this class we find, 1, two oesophageal ganglia situate
near the mouth, connected to each other by nervous filaments, which form a ring
round the gullet.   These ganglia are  connected wiih all  the rest, and probably
exercise an influence upon them, as the principal centre of the nervous system or
the brain.  2. There is a branchial ganglion, which presides over the function of
respiration.   When there is but one respiratory organ, this ganglion is single; but
it is double when there are two branchiae. From this source are supplied not only
the organs of respiration themselves, but also the muscles upon which the respira-
tory movements depend.  The  posterior  adductor muscle, the mantle, and intes-
tine, derive nerves from it.   3.  We  find a.pedal ganglion, which  is immediately
connected with the locomotive function.  This ganglion exists only in those genera
in which a muscular organ called the foot is developed, and its size is always in
direct proportion to the muscular power of that organ : it is situated at its base, and
imbedded in it. We find it, therefore, in the mussel (mytilus), but not in the oyster.
The development of organs of sense in the higher animals of this group demands
an increased development of the cerebral ganglion, as is the case in thegasteropod
and cephalopod mollusks.  And the great powers of locomotion enjoyed by the
latter animals require a high development of the pedal ganglion, and a multiplica-
tion of smaller ganglia in connection with the muscular apparatus of their arms or
tentacles.  These organs are supplied with nerves from the subcesophageal gan-
glion ; and, where suckers exist upon  the arms, an additional series of ganglia is
provided, which seem to exert an especial influence in the exercise and the main-
tenance of their suction power.
  3. The third, or Homogangliate group, is distinguished by the symmetrical ar-
rangement of the nervous system. The articulate classes furnish examples of this
type.   A bilobed ganglion  is situated above the oesophagus, and is connected with
the organs of  sense  when  they are present.   From this there proceeds on  each
side of the oesophagus a nervous cord to a pair of ganglia beneath that canal,
and therefore on  the ventral surface.   To these succeed, in most of the articu-
lata, and likewise on the ventral surface, a pair of ganglia for each segment, from
which are supplied  the  nerves to that segment.   The  ganglia are connected
throughout, however, by cords of communication from the cephalic to the caudal
segment.  The number of  pairs of ganglia is always in accordance with the num-
ber of segments of the animal: and, if some of these segments be fused together,
a similar coalescence of the ganglia takes place.  This is observed in insects in
the change from the  larva to the perfect state;  and, in some genera of Crustacea,
the permanent form of the  nervous system has obvious relation to peculiarity in
the shape of the body.  The annular arrangement of the ganglia in  the body of
the common crab (cancer}, and of the  king-crab (limulus), is evidently explained
by reference to the compressed form of the body, and the articulation of the legs
around it.
  Some additional ganglia are met with in a few animals of the  homogangliate
group, which seem to represent rudimentary conditions of the  sympathetic sys-
tem.  These have been best observed in insects, and they are described under the
name of stomatogastric ganglia.   They are two or more in number, connected by
delicate filaments with the cephalic ganglia; and they give off long nerves, which
supply the digestive  organs and the dorsal vessel, or  heart, and which, in  some
instances, unite with small ganglia in the abdomen to be distributed on the viscera
of that cavity.

  Of the Spinal cord and Brain.—The  cerebro-spinal  centre  is  en-
closed in certain membranes or meninges, which are three in number ;
the dura mater,  the arachnoid, and the pia mater.
  The dura mater consists of white fibrous  tissue.   It  is thick, very 
228
INNERVATION.
strong and flexible, without  being elastic.   Its fibres  are disposed
on different planes, but freely intermingle.  At  certain situations it
separates into two layers to form the venous canals, which are called
sinuses.  The inner  surface of the  cranial cavity is covered by dura
mater, which adheres  closely to the bones, and serves as an internal
periosteum to them ; and certain processes of the dura mater pass into
the interior of the cranial cavity, dividing it into compartments, which
contain certain  segments of the encephalon.  These processes are, 1.
The falx  cerebri, which extends from the crista galli to the  occiput
along the  line of the sagittal  suture, and forms a vertical septum be-
tween the hemispheres of the brain.  2. The tentorium cerebelli, which
is attached to the occipital bone along the groove for the lateral sinus,
and to the posterior superior edge of the petrous bone.   This process
forms a vaulted roof to the compartment which contains the cerebel-
lum, and extends between the upper surface of that organ and the
inferior surface of the posterior cerebral lobes.  In some animals, the
cat, for instance, it is partially replaced by bone.   3.  The falx cere-
belli, a small nearly vertical process which descends from the internal
occipital protuberance,  and occupies  the notch between the hemi-
spheres of the  cerebellum.
  In the spinal  canal,  the dura mater does not adhere to  the inner
surface  of the spinal bones as a periosteum.  On the contrary, it  is
separated  from  it by a  soft unctuous  fat  mixed with very numerous
veins.  It  adheres pretty closely to  the  anterior  common ligament
which intervenes  between it and the bodies of the vertebras,  and
seems to be continued  from  the cranial dura  mater  at the  foramen
magnum as a funnel-shaped process of that membrane adapted to the
shape of  the spinal canal.   It  ends in  a blunted extremity in the
sacral canal, and is tied down  in  that situation  by certain  filiform
processes, of which the central one is attached to the coccyx.  The
spinal dura mater is evidently much more capacious than is necessary
merely to  contain the  spinal  cord, and therefore  it  generally has a
loose  and  flaccid appearance.   During life it is kept tense by the fluid
which surrounds the cord.  The dimensions of the canal of the dura
mater vary with those of the  spinal canal.  It is wider, therefore,  in
the neck  and  loins, and narrow in  the  back.  In the lumbar  and
sacral region it forms a wide sac  around the leash of nerves called
cauda equina.
  The  dura mater, in both  cranium and spine, exhibits numerous
perforations for the transit of nerves from the contained centre to the
peripheral parts.   In  the spinal region each  of these perforations is
subdivided, by a vertical  slip of the membrane, into two  foramina,
which correspond to the  anterior and posterior roots of the spinal
nerves, and extend on each side down to the lower part of the sacral
region.
  The  blood-vessels of the  dura  mater are very numerous.   Those
of the cranial membrane communicate freely with those of the bones.
Hence, when separated from  the cranium, the external surface of the
dura mater has a rough appearance from the number of blood-ves-
sels which have been  torn.   This  membrane derives its supply of 
SINUSES OF THE DURA MATER.
229
anterior blood  from the ophthalmic and ethmoidal arteries in front;
in the  middle, from  the  internal  maxillary artery  by the  middle
meningeal, which  enters the  cranium by the  foramen spinosum,
and by small branches  from the internal carotid, called  the inferior
meningeal arteries.  Posteriorly the  vertebral, the occipital, and  the
ascending pharyngeal supply branches which go by the name of pos-
terior meningeal  arteries.    The  arteries  of  the spinal dura mater
come from the  deep cervical, the occipital, and  the vertebral, in  the
cervical region, from the intercostals in the back, and from the lum-
bar arteries in the loins.  These vessels pass in  at the vertebral fora-
mina, and send branches to the bones as well as to the spinal mem-
branes.
   The veins of the dura mater in the cranium  constitute a remark-
able portion of the  vascular system  of  that cavity.  The  venous
radicles collect  the blood from the dura mater, and from the bones of
the skull; large veins are formed on the former membranel and  dis-
tinct canals in the osseous diploe, figured at pages 110  and 111.  These
all tend to certain venous channels, rigid canals, formed by the sepa-
ration of  two layers of the dura mater, which are lined by processes
of the inner membrane of the venous system,  and are so placed as to
collect  the blood from all parts of the cranium.  These canals, sinuses
of the  dura mater, receive likewise the venous blood of the brain.
The largest  sinuses are the superior longitudinal  and the  lateral
sinuses.   The former extends along  the convex  edge  of the falx cere-
bri, commencing very small by receiving veins from the ethmoid  and
frontal bones, and terminates in a reservoir common  to it and  other
sinuses at the internal occipital protuberance {torcular Herophili).   It
thus  serves to  collect  blood  from the superior and  lateral parts of
the  dura mater, from the vault of the cranium, and  from the hemi-
spheres of the brain; the veins of the latter entering  it obliquely  for-
wards.   The lateral  sinuses are lodged in tortuous  furrows, which
mark the occipital, the parietal, and the temporal bones.  They are
two in  number, and extend on each side from the torcular Herophili to
the jugular foramen, where they are continued  into the internal jugular
veins.  These  sinuses serve not only to carry into the jugular veins
all the blood which is poured into the torcular, but likewise to receive
blood from the  lateral and  posterior parts of the dura mater and  cra-
nium, from the  inferior surface of the posterior lobes of the brain,  and
from the  cerebellum.  A short  sinus, also  of considerable width, is
 lodged in the tentorium cerebelli.  This is the straight sinus; it passes
from before backwards, occupying about the  middle of the vault of
the tentorium, and opening behind into the torcular. It receives blood
from the  interior  of  the brain by two large veins, the vena magna
 Geleni.   The cavernous sinuses, two in number, lie one on each  side
of the sella Turcica, from which the internal carotid arteries separate
them.  Their  irregular shape  is rather  that of reservoirs  than of
canals.   They  receive the  ophthalmic veins from the  orbit, as well as
numerous small veins from the cranial bones, the dura mater, and the
anterior and middle lobes of the brain. 
230
INNERVATION.
   Other small sinuses are met with which serve chiefly to  establish
a communication between those above mentioned, while at  the same
time they receive  some blood from the neighbouring textures.   The
petrosal sinuses, two on each side, superior and inferior, pass between
the cavernous and lateral sinuses: the transverse sinus runs between
the petrosal and cavernous sinuses of opposite sides ; and the circu-
lar or coronary sinus, while it receives blood from the pituitary body
and from the sphenoid bone, connects together the cavernous sinuses
in front, and thus  completes the venous circle  around the sella Tur-
cica.
   We see, in this arrangement of venous canals, a beautiful provision
against  the effects of undue venous congestion within the  cranium,
insured  not merely by the inextensible nature of the  principal venous
canals,  but also by the free anastomosis that exists between them, and
by the numerous points at which they communicate with the veins
of the cranium, and through these with  the  superficial veins of the
scalp.
   The spinal veins are extremely numerous and complicated. A very
intricate venous plexus surrounds  the  dura mater on  its lateral and
posterior surfaces, imbedded among the lobules of soft fat by which
the exterior of that  membrane is invested.  This plexus, less intri-
cate in  the dorsal than in the  cervical and lumbar regions, commu-
nicates  very freely with a plexus of veins which surrounds the ex-
terior of the vertebral lamina?  and processes (the  dorsi-spinal veins
of Dupuytren).   In front of the dura mater,  and situate between the
outer edge of the posterior common vertebral ligament and the pedi-
cles of  the vertebras, we find two remarkable venous sinuses which
extend the whole length of the vertebral column from the occipital
foramen to the sacrum.  They are the  longitudinal spinal sinuses  of
Willis.   In calibre  they present many inequalities, being dilated at
one part and constricted at another, according to the number and size
of the  vessels which communicate immediately with them.   The
sinuses  of opposite sides are parallel to each other, and communicate
by transverse  branches, which pass beneath  the posterior  common
ligament.   These  transverse  branches  are  of variable  calibre, like
the sinuses themselves, and are  dilated at their middle ;  at which
point they receive veins which  emerge  from the spongy texture of
the bodies  of the vertebras {basi-vertebral veins of  Breschet).*  At
the highest part of the vertebral canal, the spinal sinuses communi-
cate with the internal jugular veins; in the neck, they communicate
with the deep and  superficial vertebral veins ; with  the intercostal
veins in the dorsal region, and with the lumbar  ones in the loins.
   The arachnoid is the serous membrane of the cranio-spinal cavity.
By its parietal layer it  adheres  to the dura mater, both  of the cra-
nium  and  spine, and by its  visceral  layer to  the  brain  and spinal
cord, with  the intervention  of the pia  mater.  The space  between
these two layers is the arachnoid cavity.   In most  regions  an  inter-
val exists between the visceral layer  of the arachnoid and the  pia
* See his very beautiful illustrations of the venous system. 
THE CEREBRO-SPINAL FLUID.
231
mater, which is  called the sub-arachnoid cavity.   This space may be
demonstrated by driving air or  coloured  liquid  beneath the visceral
layer of the arachnoid.  In the spine the connection of the arachnoid
and pia mater is very loose, being  effected by some  long filaments
of fibrous tissue, which interlace slightly, and are most abundant in
the cervical region.   Along the posterior surface of the spinal cord,
in the  middle line, the sub-arachnoid space is divided by means  of a
septum, which is probably only a modified portion of the tissue of the
pia mater.   This septum is most perfect in the dorsal region, but in
the lumbar and cervical regions it is cribriform,  and in some parts is
very difficult of demonstration.  Dr. Sharpey regards it as the reflec-
tion along the median line of a serous membrane, which he supposes
to line the  sub-arachnoid cavity.   Did such a  membrane exist, we
should find an epithelium, which, however, we  have sought  for in
vain.
   The connection of the arachnoid to the subjacent pia mater is not
so loose in the head  as in the spine. On the superior and lateral sur-
faces  of the brain, where the  convolutions are  most  prominent, the
adhesion is very close, but opposite the sulci between the convolu-
tions the pia mater recedes from the arachnoid  and sinks to the  bot-
tom of each fissure, leaving large areolae in which fluid may accumu-
late.   Along the fissure of Sylvius, at the base of the brain between
the cerebellum and the  posterior surface of the  medulla oblongata,
and between the posterior edge of the corpus callosum and the supe-
rior surface of the cerebellum, the  arachnoid and pia mater are very
loosely connected, so that at these  situations  spaces are found which
are favourable for the accumulation of fluid.
   The cerebro-spinal fluid.—This fluid,  which fills the sub-arachnoid
space during life, keeps the opposed surfaces of  the arachnoid mem-
brane  in intimate contact.  Its quantity, which varies between two
and ten ounces,  is in the inverse ratio  of the bulk  of the brain  and
spinal cord.  Thus it is most abundant in old persons in whom these
organs have shrunk, and it accumulates in cases of  deficiency of any
portion of them  from malformation  or disease.   Its presence seems
necessary to the  healthy action of the nervous centres, for the removal
of  it in dogs by Majendie caused  considerable  disturbance of their
functions, probably by favouring distension of the blood-vessels.  It
is,  however, capable of being regenerated as quickly as the aqueous
humour of the eye, and  its reproduction restores the nervous  centres
to their natural state.  When removed from the  body a few moments
after death, this  fluid is, according  to Majendie, remarkably limpid  ;
it has  a sickly odour and a saltish taste,  and is alkaline, restoring the
colour of reddened litmus.
   The cerebro-spinal  fluid is most probably secreted by  the  pia
mater, since  it is found  wherever that membrane and sufficient space
exist.  The ventricles of the brain contain a secretion of very similar,
if not identical characters, which Majendie describes as communicat-
ing with that of  the  sub-arachnoid space through  an orifice at the
inferior extremity of  the fourth ventricle.  This, however, is extremely 
232
INNERVATION.
doubtful, as the fluid of the ventricles is enclosed by a proper mem-
brane which lines their cavity.
  The cerebro-spinal fluid obviously affords mechanical protection to
the nervous centres which it surrounds.  The interposition of a fluid
medium between them and the walls  of the  cavities is well adapted
to guard the former against shocks communicated from  without.  Its
accumulation at the base of the brain is highly favourable for the pro-
tection of the large vessels and nerves situate there.
  The pia mater is the immediate  investing membrane of the brain
and  spinal  cord.  It is composed of white fibrous tissue and blood-
vessels.  The former is most abundant in the pia mater of the cord,
the latter are most  numerous  in that  of the brain.   The principal
distinction,  therefore, between the spinal and cerebral pia mater is as
regards strength and thickness ;  the spinal being dense and  strong,
the cerebral being very delicate, almost wholly  composed  of minute
blood-vessels, which  are accompanied by white  fibrous tissue in small
quantity.  The spinal membrane forms a complete sheath to the cord,
and sends in processes which dip  into its  anterior  and posterior me-
dian fissures.  It is continuous with the neurilemma  of the roots of the
nerves on each side. At the  inferior extremity of  the cord it tapers and
terminates in a thread-like process {fllum terminate) which is inserted
into the inferior  extremity of the dura mater.  Superiorly it gradually
diminishes in density as it passes over the medulla oblongata to the
cerebral and cerebellar hemispheres.   To the surface of these it ad-
heres closely, and  innumerable minute blood-vessels pass from it into
the nervous substance.   It sinks into all the sulci  and  fissures, and
passes into  the lateral, the third and fourth ventricles.  In  the lateral
and fourth ventricles it forms projecting processes or folds, somewhat
fringed, highly vascular, and invested by epithelium derived from the
membrane which lines the ventricles.   These  processes  are  called
the choroid plexuses.   Into the  third ventricle it sends a lamellar fold
of triangular shape {velum interpositum), which forms a roof to that
cavity and supports the fornix.
  Attention has lately been directed to some minute sandy particles,
globular in shape, which are frequently connected with the minute vas-
cular ramifications of the internal pia mater.   They are found chiefly
in the choroid plexuses, and in that portion of the velum which invests
the pineal gland.  This sabulous matter is composed of phosphate of
lime, with  a small proportion  of phosphate of magnesia, a trace of
carbonate of lime, and a little animal matter.  (Van Ghert de pelxubus
choroideis.)
   Of the ligamentum dentatum.—This remarkable structure, found in
the sub-arachnoid  space, requires a  brief notice.   It  seems to be a
process of the pia mater,  which exhibits more  of  the glistening ap-
pearance of white fibrous tissue than the rest of that membrane.  It
extends from the occipital foramen to  the filiform  termination of the
pia mater, adhering by its inner straight border to that membrane, and
attached on the  other hand  to the dura mater by a  series of dentated
processes which penetrate the visceral and parietal layers of arachnoid, 
THE SPINAL CORD.                    233
 pinning them, as it were, down to the fibrous membrane.  They form
 a  vertical septum  between the anterior and posterior roots of the
 spinal nerves.  The dentated processes vary in number from eighteen
 to twenty-two.  The first is attached to the dura mater which covers
 the occipital foramen just behind the vertebral  artery; the  rest are
 inserted between the orifices  for the  exit of the spinal nerves, and
 the  last is on a level with the first or second  lumbar vertebra.  A
 considerable quantity of yellow fibrous tissue exists in this structure,
 especially in its dentated processes.
   The Pacchionian glands or bodies  are whitish granules, composed
 of an albuminous material,  which are found among the vessels of the
 pia mater, on the edges of the cerebral hemispheres, which push the
 arachnoid before them, and even project into the longitudinal sinus.
 They do not occur in the earliest periods  of life, and are frequently
 absent  even at the  more advanced ages, but they are so often met
 with in the brains of adult  and old persons that  many anatomists
 regard  them as normal structures.
   Of the Spinal Cord.—The  spinal cord is somewhat cylindrical  in
 shape,  slightly flattened on  the anterior and  posterior surfaces.  Its
 anatomical limits are, the occipital plane above, and  a point ranging
 in different subjects between the last  dorsal and second lumbar ver-
 tebra below.  It tapers to its  inferior extremity,  which lies concealed
 among the leash of nerves which comes off from its lumbar region,
 the cauda equina.   Superiorly the spinal cord is separated  from the
 medulla oblongata by the decussating fibres of the anterior pyramids.
   In the cervical and lumbar regions the cord exhibits distinct swell-
 ings, of which the  cervical is the larger.   The cervical swelling ex-
 tends from the third cervical to the third dorsal  vertebra, the lumbar
 one commencing about the ninth or tenth dorsal vertebra, and not
 extending beyond  the space corresponding to two vertebras.   These
 enlargements correspond to  the situations at  which the large  nerves
 to the  extremities  emerge, in conformity with  a law that the  phy-
 sical development of  any portion of the cord is in  the direct  ratio
 of the sensitive and motor power of the parts which  it supplies with
 nerves.
   The  spinal cord is divided  along the median  plane by an  anterior
 and  posterior fissure into two equal and symmetrical portions, of which
 one may be called the right, the other  the left spinal cord.   A trans-
 verse bilaminate partition, extending throughout the  entire length  of
 the cord, separates these fissures, and serves  to  unite its lateral por-
 tions.   This partition is composed of a vesicular or gray and  a white
 or fibrous  lamina or commissure, the  gray  being situate posteriorly.
 When examined in a  transverse  section, the anterior fissure  appears
 evidently wider but of less depth than the posterior ;  it is penetrated
 by a distinct fold of pia mater  ; its floor is formed by  the white com-
 missure, which has a cribriform appearance, from being perforated by
numerous blood-vessels.   The posterior fissure is much more delicate
than the anterior, and about the middle of the cord its existence may
be doubted; its depth, in the upper part of its course, is equal to fully
     16 
234
INNERVATION.
one half of the thickness of the cord.   A single, very delicate layer
of pia mater enters it and penetrates to its floor, which is formed by
the gray commissure.
   On further examination of a transverse section of the  cord, we ob-
serve that the interior of each half of it is occupied by vesicular mat-
ter, disposed somewhat in a crescentic form.   The concavity of this
crescent is directed outwards: its anterior extremity, or horn, is thick,
but its margin  has a  dentated or stellate appearance, which is very
distinct in some situations.  The gray  matter is prolonged  backwards
in the form of a narrow horn, which reaches quite the surface of the
cord, near which it experiences a slight enlargement.   This enlarge-
ment appears to consist of a gray matter, paler and softer than that of
the remainder of the crescent, which has been distinguished by Ro-
lando as substantia cinerea gelatinosa,  surrounded by a layer of red-
dish-brown substance (see  fig. 66, d., where the central part  of the
posterior horn is pale).   An exact symmetry exists between the gray
crescents of opposite sides, so that the description of one is applicable
to the other.
   The prolongation of the posterior horn  of each gray crescent to the
surface divides each half of the cord into two portions.  All that is
anterior to the posterior horn is called  the antero-lateral column:  and
this comprehends the white matter forming the sides and front of that
half of the cord, limited in front by  the anterior  fissure, and posteri-
orly by the posterior horn.   The posterior column is situated behind
the posterior horn of gray matter, and  is separated from its fellow of
the opposite side by the posterior fissure.  The antero-lateral columns
are united across the middle line by the anterior or white commissure;
the gray crescents, by the posterior or gray commissure; while the
posterior columns are not connected,  except where the posterior fis-
sure is imperfect or deficient.
   In  the different  regions of the cord great variety exists as regards
the quantity of gray and white matter,  and  the disposition of the
lateral portions  of  the former.   There seems  to be  a  much greater
proportion of gray matter to white in the lumbar, than in the cervical
or dorsal region of the cord.   In the  cervical region the crescentic
portions are small, and the white matter  is abundant.   That portion
of the white substance which  is placed  between  the posterior gray
horns, is augmented by the existence of two small  columns {posterior
pyramids), which extend from the medulla oblongata into this region.
In the dorsal region the gray matter is at its minimum of development,
and the white  matter is likewise small in quantity.   The  diminution
in the quantity of the latter appears more striking as affects the antero-
lateral,  than the posterior columns.   In the  lumbar region both the
horns of the gray matter are manifestly thicker, and the stellate cha-
racter of the  anterior horn is  well marked.  Towards  the inferior ex-
tremity of the cord the white matter appears gradually to cease, leaving
the gray to form the principal constituent, until in the commencement
of the filiform process it is found alone (fig. 66).
   The roots  of the spinal nerves emerge from the cord on each side 
THE SPINAL CORD.
235
Fig. 66.
along two  lines which are separated by the ligamentum dentatum.
The posterior line corresponds to the margin of  the posterior horn of
gray matter, the anterior one is placed about mid-
way between  it and the  anterior fissure.  When
the roots  of the  nerves have  been carefully re-
moved, their points of emergence are indicated
by two series  of  foramina in linear sequence on
each side, but there is no  appearance of fissures
in those situations.  The roots of the nerves pe-
netrate the substance of the cord, and  are chiefly,
if not entirely, connected with  the antero-lateral
columns.
   The fibrous matter of the cord consists of some
fibres  which  pass  in  a  longitudinal  direction,
which are chiefly superficial or contained in the
posterior columns, and of others which are oblique
or transverse, and are found in  the antero-lateral
columns,  or in the  white  commissure,  which is
wholly composed  of  such fibres.   Among the
elements  of the  gray matter fibres are found in
great  numbers, the direction  of  which is  pro-
bably  for  the  most  part  oblique or transverse, as
considerable portions  of them may be seen  so
running,  when  a   piece  of  gray  matter,  cut
transversely, is examined  under the  microscope.
The gray matter  of the cord is disposed in two
longitudinal columns,  the  shape of which in the
several regions of the cord is represented  in the
above transverse  sections (fig.  66).   These co-
lumns extend from the lower part of the medulla
oblongata, with  the gray matter  of  which  they
are continuous.  The  aspect of their surfaces is
outwards  and inwards.  That  which looks in-
wards is  convex,  and is united to  the  corre-
sponding  surface of the opposite side by the gray
commissure, which is  a vertical plane, with sur-
faces looking  directly forwards and  backwards.
At the inferior extremity of the cord these columns
gradually taper to  a point, and  coalesce  as the
white  matter diminishes.
   Caudate and spherical  vesicles, imbedded  in
their usual granular matrix, exist in  the  gray
matter of the cord  at all  situations, in the horns
as well  as in the  commissure.   The caudate
vesicles are most numerous and distinct in the anterior horn, and at
the root of the posterior  one.   The  rest of the posterior horn and
the gelatinous  substance resemble very closely in  structure the gray
matter of the convolutions of the brain.   When  very thin transverse
sections are examined with low powers, a good general view of  the
relative disposition of the gray and white  columns is  obtained,  but
  Transverse sections of
the spinal cord:—a. Im-
mediately below the de-
cussation of the pyramids.
b. At middle of cervical
bulb.   c. Midway  be-
tween cervical and lum-
bar bulbs.   d. Lumbar
bulb.  e. An inch lower.
f. Very near the lower
end. a. Anterior surface.
p. Posterior surface. The
points of emergence of
the anterior and posterior
roots of the nerves are al-
so seen. 
236
INNERVATION.
Fig. 67.
we gain no satisfactory information as  regards the relation of the
elements of  these columns (fig. 67).   Stilling and  Wallach's plates
                                       accord generally with  the re-
                                       sults  of  our own  examina-
                                       tions,  but  we  cannot admit
                                       the accuracy of their interpre-
                                       tation  of some of the appear-
                                       ances  which they have  wit-
                                       nessed and delineated.
                                          In  such  a section  as that
                                       just described, the  distinc-
                                       tion of gray and white  mat-
                                       ter  is very obvious.  From
                                       the  surface  of each  horn of
                                       the  former  several  lines,  of
                                       the same colour and general
                                       appearance  as the   central
                                       mass,  pass,  in a  radiating
                                       mariner,  towards the surface
                                       of the cord and to the sur-
                                       face of  the fissures (fig. 67).
                                       These  lines,  according  to
                                       Stilling   and   Wallach,  are
                                       continuous w7ith the  roots of
                                       the nerves,  and are  nerve-
tubes proceeding from  the gray matter to form  these roots.  Their
existence, however, in sections made in situations intermediate to the
points of emergence of  the nerves,  shows that this explanation can-
not be the true one.  Moreover, they radiate over a  surface  much
more extensive than that from which the  roots  take  their rise, and
several pass to that part of the surface of the cord which bounds the
fissures, and from which it is impossible that they could reach the point
of emergence of either root to contribute to  its formation.   It is not
improbable, however, that they may be processes  of the gray matter
prolonged toward the surface, to which  blood-vessels  may pass from
the pia mater.*
   We observe in the gray matter numerous  nerve-tubes of various
size passing among its elements in different directions.  Besides these,
the  branching processes from  the  caudate vesicles are found here:
these processes differ from the nerve-tubes in  the absence of the white
substance of Schwann,  in their grayish colour, in their  branching, and
in a certain minutely granular texture.   Numerous extremely minute
fibres, perfectly transparent in texture, may be traced to be continu-
ous with the finer  subdivisions of these processes (fig. 56, p.  198).
Fibres of the same appearance are occasionally found among the  tubes
of the white substance of the spinal  cord; their connection with  those
of the gray matter is unknown.
 Transverse section of human spinal cord, close to
the third and fourth cervical nerves; magnified ten
diameters, (from Stilling :)—/. Posterior columns,  ii.
Gelatinous substance of the  posterior horn. k. Pos-
terior root.  I. Supposed anterior roots,  a. Anterior
fissure,  c. Posterior fissure.  6. Gray commissure, in
which a canal is contained, which, according to these
writers, extends through the length of the cord.  g.
Anterior horn of gray matter  containing caudate vesi-
cles, e. Antero-lateral column (from A; to a).
  *  Mr. Smee has lately exhibited to us some well-injected preparations, in which
these lines are shown to contain vessels. 
WEIGHT OF THE BRAIN.
237
  Capillary blood-vessels are met with in great numbers ramifying
in the gray matter.   They are much more numerous in this than in
the  white matter, and the observer should be careful not to confound
the  most minute of them with some of the fibrous elements above de-
scribed.
  So far  as our present knowledge of the minute anatomy of the
spinal cord extends, it is favourable to the supposition that the spinal
nerves derive their  origin, at least partly, from the gray matter.  The
longitudinal fibres of the cord may consist in part of fibres continuous
with those of the brain or  cerebellum, and in  part of  commissural
fibres,  serving  to  unite various  segments  of  the cord with  each
other, or to connect some part or parts of the encephalon with them.
Those fibres which  may be  regarded as strictly spinal  are  probably
oblique in their course, forming their connection with  gray matter at
a point higher up in the cord than  that  at which they  emerge  from
its  surface, and  may be readily confounded with the  longitudinal
fibres when their course is long.  Other  oblique or transverse fibres
probably  do not emerge from  the cord, but connect the  segments
of opposite sides, forming  a transverse commissure.   So  that  four
classes of fibres, each  different in function,  may be considered to ex-
ist in the cord.   1. Spinal fibres, oblique or transverse, which  pro-
pagate nervous  power to  or from the segments  of the cord itself.
2. Encephalic fibres, longitudinal, the paths of volition  and sensation,
which  connect the  spinal cord with the various segments of the en-
cephalon.  3. Longitudinal  commissural fibres.   4. Transverse  com-
missural fibres.
  Of the encephalon.—The  brain or encephalon is that  mass which
is  contained within the cranial cavity.   The plane of the  occipital
foramen  separates it from the spinal  cord, inasmuch  as that plane
would  about pass through the inferior extremity of the  medulla ob-
longata.
  Four segments are obviously distinguished in the encephalon.   1.
The medulla oblongata.  2. The cerebrum.  3. The cerebellum.  Some
fibres of the medulla oblongata extend to the cerebrum,  and some to
the cerebellum.  The fourth  segment, which is called the  mesocephale,
contains fibres passing between all the rest, as well as some connect-
ing opposite sides.  This constitutes a  sort of conflux to the segments
above named,  and may be compared to a railway terminus,  at which
several  lines meet and  pass each other.
  The brain of  the adult man weighs about 50 oz., or a little more
than 3 lbs. avoirdupois.*  This great weight depends mainly upon the
cerebrum and cerebullum, the medulla oblongata and   mesocephale
forming not more than  one-tenth of the whole weight.   These parts
exist in their highest state of development in man.  Their size  does
not appear to be regulated by the physical development  of the body,
either in man or in  the lower  animals.  Thus the horse, although
greatly exceeding the  human subject in the size of his  body, has a

  *  See Reid's Tables.  Lond. and Edinb. Monthly Journal of Med. Science. April,
1843. 
238
INNERVATION.
brain considerably inferior.  The largest brain of a  horse weighs,
according to Soemmering, 1 lb. 7 oz., but the smallest adult human
brain may be estimated at 2 lbs. 5^ oz.  Many other instances might
be cited, of animals of great bulk, with brains weighing considerably
less than that  of  man.   The brains  of the elephant  and the whale,
however, although inferior to it in general organization, are absolutely
heavier than that of man. That of an elephant, dissected by Sir Astley
Cooper, had a weight of 8 lbs. 1 oz.;  and Rudolphi found the brain
of a wThale,75 feet long, (Balanamysticetus,) to weigh 5 lbs. 10^ oz.
Yet how inferior must be the development of the brain in these stu-
pendous animals relatively to the whole body, if, with their enormous
superiority of bulk, their brains exhibit so little excess of weight over
that of man!
  Even among men there does not appear to be  any fixed  relation
between the bulk of the body and that of the brain.   A large man
has by no means  necessarily a large  brain, and it often happens that
persons of small  stature have the brain above the  average size.  In
women the brain  is generally lighter than in men.   Dr. John Reid
assigns an average difference of 5 oz. 11 dr. in favour of the male
brain.  Yet this  difference is  scarcely proportionate to  the  general
inferiority of  organization and of size of the  female to the male.
  It is impossible to explain the great superiority of the human brain,
both in organization  and in the  absolute quantity  of  nervous matter
which it contains, without  admitting its connection with the mind,
and  the  influence exerted  upon its nutrition and growth  by  that
immaterial principle.    The men of greatest intellectual power  are
those who  possess the  largest brains.   Cuvier's brain, as stated by
Tiedemann, weighed 4lbs. 11 oz. 4 dr. 30 grs. troy; and that of Du-
puytren 1 oz. 4 dr. 30 grs. less.   On the other hand, the brain of an
idiot weighs scarcely more than  that of the horse  mentioned above.
Tiedemann found the  brain  of an idiot, fifty years old, to weigh 1
lb. 8 oz. 4 drs.;  and that of another,  forty years  old, 1 lb. 11 oz. 4
drs.   In advanced age, when the mental faculties have declined,
the brain generally experiences a decrease of  size  ; there are many,
however,  who preserve  their intellectual vigor to a very advanced
period of  life, and in such  persons, doubtless, the  brain does not ex-
hibit any evidence of  shrinking.   It is during the  period of greatest
mental activity and power  that the brain  acquires and maintains its
highest point of development, that is, between the ages of twenty and
sixty.
  Whilst there is an evident connection between  a large quantity of
cerebral matter, and a  highly developed intellect, the quality of  the
mind and that of  the brain substance may also be supposed to have a
close relation to each other.  For great power of action a large mus-
cle is needed, but for vigorous and well-adjusted muscular movement
a certain quality of fibre is also  necessary to  give full scope to  the
nervous  power (see pp. 175-7-79).  It is impossible  to determine
what this peculiarity in quality is, but some idea  of the great influence
which it may possess in  the exercise of the two great vital forces, the
muscular and nervous, may be gained from comparing the energy and 
THE MEDULLA OBLONGATA.
239
action of a well-bred horse with those of one which, in the language
of the turf, shows little or no breeding.   The actual amount of mus-
cular or nervous fibre may be the same  in both, or it may be  less in
the  horse of good breeding than in the other, yet the former does his
work and endures fatigue better.
  The nature of the connection between  the mind and nervous matter
has ever been, and must continue to be, the deepest mystery in phy-
siology ;  and they who  study the laws  of  Nature, as ordinances of
God, will regard it as one  of those secrets of his counsels " which
Angels  desire to look into."*   The individual experience of every
thoughtful person, in  addition to the  inferences  deducible from re-
vealed Truth, affords convincing evidence that the  mind  can work
apart from matter, and we have many proofs to show that the neglect
of mental cultivation may lead to an impaired state of cerebral nutri-
tion ; or, on the other hand, that diseased action of the brain may in-
jure or destroy the powers of the mind.  These are  fundamental truths
of vast importance to the student of  mental  pathology as well as of
physiology.  It may be readily understood that  mental and physical
development should go hand in hand together, and  mutually assist
each other; but  we  are not, therefore,  authorized to  conclude  that
mental action results from the  physical  working of  the brain.   The
strings of the harp, set in motion by a skillful performer, will produce
harmonious music if they have been previously duly attuned.  But if
the instrument be out of order, although the player strike the same
notes, and evince  equal skill in the movements of his  fingers, no-
thing but  the  harshest discord will ensue.   As, then, sweet melody
results from skillful playing on a well tuned instrument of good con-
struction,  so a  sound mind, and a  brain of good  development  and
quality, are the necessary conditions of  healthy and  vigorous mental
action.
  Medulla oblongata.—Of the segments of the  encephalon above
enumerated, the medulla oblongata is that  which is more immedi-
ately connected with the spinal  cord, and  through which  the brain
is brought into communication with the other vital  organs and with
most of the peripheral parts.  It is, therefore, truly " the link which
binds us  to life."   In form  and  general  anatomical  characters,  it
very much resembles the  spinal cord, with  which it is  continuous,
standing in the same  relation to it as the  capital to the shaft of a
column.
  In the sense in which we here speak of  it, the  medulla oblongata
is limited above by the mesocephale; but  its constituent  fibres ex-
tend beyond that segment, and form important connections with the
rest of the brain. It is completely contained within the cranial cavity,
its lowest part being just above the  level of the plane of the occipital
foramen.
  The size of the medulla oblongata is  in the direct ratio of that of
the  nerves which proceed from it. Hence it is very much larger, both

  *  The admirable chapter in Bp. Butler's  Analogy "Of a Future Life," cannot be
too attentively studied in reference to this subject. 
240
INNERVATION.
absolutely and relatively, in some of the lower animals than in man:
in many of them it forms the largest of all the segments of the ence-
phalon, while in man it is much the smallest.
   In the medulla oblongata there is the same symmetry of arrange-
ment which we have noticed in the  cord.   An anterior and posterior
fissure divide it into two  equal and  symmetrical portions.  The pos-
terior fissure is deep and narrow, and is  continuous with that of the
cord.   The  anterior fissure is wider and  less deep, and  is separated
from the same fissure of the cord by certain fibres which cross obliquely
from each side in its lower third, decussating each other.   These fibres
are called the decussating fibres of the anterior pyramids,  and form,
very fitly, an anatomical  demarkation between the medulla  oblongata
and the spinal cord.
   The floor of the  anterior fissure  is formed by a  layer of fibrous
matter which is  rendered cribriform by the orifices of the  numerous
bloodvessels which  penetrate  it.  This  constitutes a commissure of
transverse fibres, similar to  that  described in the spinal  cord.   The
posterior fissure extends  to the posterior surface of  this commissure,
there being  no such  transverse lamina of  vesicular matter in the me-
dulla  as in the cord.
   When the pia mater has been  carefully removed from  the surface
of the  medulla oblongata, certain grooves are seen which indicate  a
subdivision  of the  organ, which   is  convenient for  the  purposes of
description.    In front are the anterior pyramids {corpora pyramidalia
antica) separated from  each other along the middle line by the ante-
rior fissure.   External to each anterior pyramid there is an  oval pro-
minence surrounded by a superficial groove, which in some instances
is  partially interrupted  by some arciform fibres which cross it at its
                      lower  part.   These projections  are the oli-
                      vary bodies.   External to these, and forming
                      the lateral and a great part of the  posterior
                      region of the medulla oblongata,  are the res-
                      tiform bodies, two thick  columns of fibrous
                      matter, which are  separated  from each  other
                      along the middle line by two slender columns,
                      the posterior pyramids. These last bound the
                      posterior  fissure.
                         The anterior pyramids  are   bundles of
                      fibrous matter  which extend between the
                      antero-lateral columns of the cord and the
                      cerebral hemispheres.  Below the  mesoce-
                      phale the fibres are compactly applied to each
                      other so as to form on each side  of the me-
                      dian line  a column of white matter, the trans-
                      verse section of which has more  or less of a
                      triangular outline.    Traced  upwards, the
                      pyramids  are found to pass  into the meso-
                      cephale above its inferior layer of transverse
                      fibres,  the pons  Varolii.   At its  entrance
                      into this   part of the brain  each pyramid
Fig. 68.
 Front view of the medulla ob-
longata:—p.p. Pyramidal bo-
dies, decussating at d.  o, o.
Olivary bodies, r.r. Restiform
bodies,  a. a. Arciform fibres.
v. Lower fibres of the Pons Va-
rolii. 
THE MEDULLA OBLONGATA.
241
experiences a slight but well-marked constriction, but immediately
expands again ; and its fibres  in  their further course upwards gra-
dually diverge, and contribute to form the inferior lamina of the crus
cerebri.
  In their ascent through the mesocephale the fibres of the pyramids
are crossed at right angles by some  deep transverse  fibres on differ-
ent planes which belong to the same system as those which constitute
the pons.   With these fibres those  of the pyramids  interlace.  Ve-
sicular matter is deposited  in the intervals between  the more deeply
seated fibres, from which probably some fibres take  their  origin, and
join the pyramids at their emergence from the pons, to form the in-
ferior layer of the crus cerebri.
   Traced downwards, the  fibres  of each anterior pyramid  pass  in
greater part backwards as well as downwards, sinking  into the ante-
ro-lateral column of the cord of  the opposite side (fig. 68, d), whilst
a small portion of them, those, namely, which  constitute the outer
margin of each pyramid, pass to  the column of the same side.   Other
fibres of these bodies do not pass  down into the spinal cord at all, but
taking a curved course around the inferior extremity of each olivary
body they ascend towards the cerebellum, forming the arciform fibres.
Or, if the description be pursued  in  an opposite direction, each pyra-
mid may be stated to be  composed  of some fibres from  the antero-
lateral spinal  column of its own side, and of  others which  greatly
exceed the  latter in number,  from the antero-lateral column of the
opposite side, and  it is connected with the restiform body  of the same
side by the arciform fibres.
  The decussation takes place by from three to  five bundles of fibres
from each pyramidal body.  In separating the margins of the anterior
fissure, these fibres are found to  interrupt its continuity with the an-
terior fissure of the  medulla  oblongata, and, therefore, may be con-
veniently referred to as a  boundary between the  medulla oblongata
and the spinal cord.
  This decussation has great interest in reference to  the explanation
of the phenomena  of diseased brain.   It is well known that lesion  of
one hemisphere of the brain when sufficiently extensive to cause pa-
ralysis, will induce that paralysis  on the  opposite side of the  body.
And,  although a very few exceptions have been recorded, this is  so
constant that it must be regarded  as a law, that  the influence of each
hemisphere is rather upon the opposite half of the body than on that
of its own side.  It is not, however,  meant that the  hemisphere has
no influence on the same side of the body.   On the contrary, it  is
most probable that it does exert some influence from  the partial con-
nection of each anterior pyramid  with the antero-lateral column of the
spinal cord on the  same side. Now the decussation, above described,
obviously suggests  an explanation of this phenomenon, which is among
the most interesting that anatomy can  offer.  In  confirmation  of this
statement it may be remarked, that lesion of one side of the cord,6e-
low the decussation, affects the same side of the body, and  that alone ;
whilst disease of a paralyzing influence, wherever it  occurs above the
decussation, affects the opposite  half of the body.  The  exceptions 
242
INNERVATION.
Fig. 69.

to this rule are too anomalous and few to  invalidate the explanation
so long adopted.
   The restiform bodies form the lateral and posterior part of the me-
                                dulla oblongata.   They  are  cylin-
                                drical in  form.   Below  they are
                                distinctly continuous  with the an-
                                tero-lateral  and  posterior  columns
                                of the cord.  As they ascend, they
                                diverge  and leave a considerable
                                space between them, which  is the
                                fourth  ventricle.  Each  restiform
                                body passes into the corresponding
                                hemisphere of the cerebellum, form-
                                ing  a considerable portion  of the
                                crus, the  stalk  of  fibrous  matter
                                around   which  the hemisphere  is
                                formed.   These bodies are, there-
                                fore, the bond  of connection  be-
                                tween  the  cerebellum  and  the
                                spinal cord, for which reason they
                                have been appropriately designated
                                processus cerebelli  ad  medullam ob-
                                longatam.
                                   The  posterior median  fissure  is
                                bounded on each side  by a small
                                column, not exceeding one-eighth
                                of an inch  in breadth.   These co-
                                lumns are called the posterior pyra-
                                midal bodies.  Their outer limit and
                                line  of demarkation from the rest-
iform  bodies is  indicated  by a  superficial  groove, along which a
separation of the two structures readily takes place, in a preparation
previously hardened in spirit.
   The olivary bodies are oval projections on each  side of the anterior
pyramids.   When the latter have been carefully removed, it maybe
demonstrated that these bodies are continuous with the central part of
the medulla oblongata.  They are coated on the  outside with fibrous
matter, within which is a folded lamella or capsule of vesicular sub-
stance, enclosing a white nucleus.  By slicing off" a layer of this body
even with the surface of the medulla, the capsule  may be seen dis-
posed as a wavy line, surrounding an  oval space of white matter.  If
examined in transverse section, this wavy line of vesicular matter is
still apparent, but it is incomplete behind and within; and the same
may be observed  on  a vertical  section  of  the  olivary body.   This
lamina is called the corpus  dentatum.
   When the pyramids are very largely developed these oval projec-
tions on the surface of the medulla oblongata do  not appear.   Hence
the olivary eminences are peculiar to the  human  subject, and some of
the monkeys.
   On tracing the olivary bodies downwards, they  are found  to ap-
 Postenor view of the medulla oblongata :
—pp. Posterior pyramids, separated by the
posterior fissure, rr. Restiform bodies, com-
posed of ec, posterior columns, and dd,
lateral part of the antero-lateral columns of
the cord. an. Olivary columns, as seen on
the floor of the fourth ventricle, separated
by  s, the median fissure, and  crossed by
some fibres of origin of nn, the seventh pair
of nerves. 
THE MEDULLA OBLONGATA.
243
proximate towards  each other, the  anterior pyramids which separate
them gradually diminishing in breadth, and they apparently terminate
by becoming continuous with the antero-lateral columns of the spinal
cord.
  The olivary bodies, though separated from the margin of the pons
Varolii by a distinct depression, may be traced upwards through the
mesocephale along with the  central substance of the medulla ob-
longata {fasciculi innominati  of Cruveilhier), forming a considerable
portion of the  superior layer of each crus cerebri, and apparently
becoming continuous with the optic thalamus and quadrigeminal
bodies.
  The olivary bodies and the central substance  of the medulla oblon-
gata may be described as connecting the spinal cord with the quadri-
geminal bodies and the optic thalami.
  It seems highly probable that the olivary bodies constitute the es-
sential portion  or nucleus of the medulla oblongata; that on which its
power as an independent centre depends.  Strong support to this view
is derived from the important fact, that  these  bodies and the central
portion of  the  medulla oblongata, with  which  they are directly con-
tinuous, contain that  intermixture of vesicular  and fibrous matter
which constitutes the main character of a nervous centre.
  If this be correct, the anterior and posterior pyramids,'and the rest-
iform bodies, must be regarded as consisting chiefly of fibres which
pass from the spinal cord  to  the  cerebrum, or  cerebellum, and not
essentially concerned  in the formation  of the medulla oblongata.
The fibres of these bodies  are  in  fact mainly commissural; the an-
terior pyramids  serving to  connect the  cerebral hemispheres  to the
spinal  cord, the restiform  bodies connecting the cerebellum  to it,
and the posterior pyramids  being the means of connection posteriorly
between the medulla oblongata and the cervical  and dorsal regions
of the spinal cord.   But the  olivary bodies and the central matter of
the medulla are directly continuous with  certain principal gangliform
masses of the brain, the optic thalami and quadrigeminal  bodies, and
by their prolongation upwards form a large portion of the  crura of the
brain.
  From  the description of  the  minute structure of the medulla ob-
longata by  Stilling, founded upon investigations  conducted in the
same way as those  on  the  spinal cord,  it would  appear  that nume-
rous transverse fibres pass  into the central and posterior part of the
medulla.  It is not  unlikely that many of  these so called fibres may
be bundles of nerve tubes,  but  it is also highly probable that many
of them are blood-vessels, which pass in  great numbers into the cen-
tral substance of the medulla.   The same mode of connection which
exists between  the roots of the nerves and the spinal cord, whatever
that may be, will no doubt be found to prevail  in  the medulla ; and
as  several important nerves  emerge  from  this portion of the  ence-
phalon, it seems very likely that  their fibres  should penetrate to its
central part to form a connection with its gray matter.   This ques-
tion, however,  is not to be  decided  by the  use of low  powers of
the  microscope, such as Stilling  employs; nor have our  trials wilh 
244                         INNERVATION.


higher ones as yet led to any information sufficiently specific to ena-

ble us to make a positive statement respecting the  points in question.

There is nothing in the results of Stilling's researches which does not

confirm that which previous dissections, by coarser means of obser-

vation, had pointed out—namely, that the  restiform and  pyramidal


                                  Fig. 70.
 Transverse section of the medulla oblongata through the lower third of the olivary bodies. (From
Stilling.)  Magnified 4 diameters.
 a. Anterior fissure. 6. Fissure of the calamus scriptorius.  c Raph6.  d. Anterior  columns.
e.  Lateral columns, f. Posterior columns, g. Nucleus of the hypoglossal nerve, containing large
vesicles,  h. Nucleus of the vagus nerve, i, i.  Gelatinous substance,  k, k. Roots of the vagus
nerve. I. Roots of the hypoglossal, or ninth nerve,  m. A thick bundle of white longitudinal fibres
connected with the root of the vagus, n. Soft column {Zartstrnng. Stilling), o. Wedge-like column
{Keelstrang, Stilling),  p. Transverse and arciform fibres, q. Nucleus of the olivary bodies r. The
large nucleus of the pyramid. s,s,s. The small nuclei of the pyramid,  u. A mass of gray substance
near the nucleus of the olives (Olk-en-Nebenkem..  u, q, r, are traversed by numerous  fibres pass-
ing in a transverse semicircular direction, v, w. Arciform fibres,  x. Gray fibres.


bodies are composed in  great  part  of  fibres, taking  a  longitudinal

course, while  the central  portion  contains  both the  vesicular and

fibrous nervous elements.   The fibres of the latter, according to Stil-

ling, taking chiefly,  if not exclusively, a transverse direction.

   There  is no evidence of any interchange of fibres between the rest-

iform bodies, nor  between  the posterior pyramids of the right and

left sides, such  as has  been noticed between  the anterior  pyramids

in the description of their decussating fibres.   The central or olivary

columns of the medulla oblongata,  however, have a  very intimate con-

nection with each other, along the mesial plane,  apparently  by fibres

passing from one to  the other. 
THE CEREBELLUM.
245
  When the medulla oblongata is divided vertically along the median
plane, a series of fibres is seen to form a septum between its right and
left half.   These fibres take a direction  from before backwards, and
appear to connect  themselves with the posterior olivary columns.
They are  limited inferiorly by the decussating  fibres.   Cruveilhier
proposes for them the name antero-posterior fibres; they appear to be-
long to the same system as the arciform  fibres.
   Of the cerebellum.   This segment of the encephalon  is situated
above and behind the medulla oblongata in a distinct compartment of
the cranium, which has for its roof the tentorium  cerebelli.  It bears
to the cerebrum in point of weight about the proportion 1: 8, and to
the entire encephalon, 1: 10.
   The cerebellum consists of a  central and of two lateral portions.
The former, also called the median lobe, is the primary part; it is the
only part of the organ which exists in fishes and reptiles ;  the lateral
portions  or hemispheres are additions to this, and denote an  advance
in  development.  It is in birds that these are first found ;  they are
most highly developed in mammals, and attain  their maximum in
man.
   Upon  removing the pia mater from the surface of the cerebellum,
we observe its arrangement in numerous thin lamellae, which  are at-
tached to a  central  column of fibrous matter.   A vertical section of
either hemisphere serves  well to display their structure.  A series of
planes of fibrous  matter become detached from the central white
column,  each plane separating from it  at a  different  angle.   These
planes are in number  about ten, counting those on the upper as well
as the under surface.  Those situated in front are detached at  a right
angle, the posterior ones  at an acute angle.   Each plane forms the
centre of a lobule, and as it proceeds  outwards secondary planes are
detached  from it, and from these  again others separate.  These se-
condary and tertiary planes are clothed by a layer of vesicular matter,
which also invests the primary planes at the angles of separation from
the principal central column.
   We have described each primary plane as forming the central por-
tion,  or stem of a lobule.  Each lobule is circumscribed and separated
from  those in immediate relation to it, by a fissure which  extends to
the principal column.   The lobules  are composed of laminae  which
derive their fibrous  matter from the central stem.
   Thus the  substance of each hemisphere of the cerebellum is pene-
trated by a  number of fissures, easily traced by  following the pia
mater, which lines them.  These fissures  are divisible into two classes,
primary and  secondary.   The primary penetrate to the principal cen-
tral column, and isolate the lobules;  the secondary  separate the
lamellae of which each lobule is composed.   The deepest and most
remarkable of the former corresponds to the posterior margin of each
hemisphere,  passing in the horizontal plane  forwards  and separating
the posterior lamina? into a superior and inferior set.
   The structure of  the median lobe is essentially  the  same as that of
the hemispheres.  A stem of fibrous  matter, continuous with the pro-
cessus cerebelli  ad testes, constitutes  the central column, and  planes 
246
INNERVATION.
radiate from it in the same manner  as in the hemispheres.   Lobules
are formed around these  planes, and the aggregate of those on  the
superior  surface  of the median lobe constitutes what is called  the
superior vermiform process; and that of the inferior ones, the inferior
vermiform process.  The  lobules of the  median  lobe have  a distinct
continuity of substance with those of the hemispheres on each side,
and thus the entire lobe becomes a medium  of connection, or a com-
missure between the  hemispheres;  nevertheless, the similarity of its
structure to that of the hemispheres, and its  existence in the animal
series without the lateral  portions, denote that it exercises an inde-
pendent function.
   Within the  central stem of each hemisphere of the cerebellum,  the
fibrous matter is partially interrupted  by a  peculiar arrangement of

                                Fig. 71.
  Analytical diagram of the encephalon—in a vertical section. (After Mayo.)
  s. Spinal cord. r. Restiform bodies passing to. c. the  cerebellum, d. Corpus dentatum of the
cerebellum, o. Olivary body. /. Columns continuous with the olivary bodies and central part of
the medulla oblongata, and ascending to ihe tubercular quadrigemina and optic thalami.  y. An-
terior pyramids,  v. Pons Varolii,  n, b. Tubercula quadrigemina. g. Geniculate body of the optic
thalamus,  t. Processus cerebelli ad testes, a. Anterior lobe of the brain, q. Posterior lobe of the
brain. 
THE CEREBELLUM.
247
the vesicular substance, called by Vicq d'Azyr corpus dentatum (fig.
71, d).   This is only found in the inner half of the stem, at about a
quarter of an inch from the origin  of the crus.  It  may be demon-
strated by making a vertical section through the cerebellar hemisphere,
leaving two-thirds of its substance to the outside of the section. The
surface of the section presents at  the situation above  described a  re-
markable layer or capsule of gray matter, surrounding in great part
an oval space; the gray layer has an  undulating disposition, and is
convex towards the surface, but open towards the crus.  The precise
object of this remarkable structure is not  known; but the  microscopic
investigation of it shows that in it there is a mingling  of the elements
of the vesicular and fibrous substances.
   The central stem, or crus, around which  each hemisphere of  the
cerebellum is developed, is formed by three  bundles of  fibres, each
on  a different plane.  These are called its peduncles.  Through them
the cerebellum forms a connection with other parts of the  encephalon.
The superior layer  or peduncle  is a bundle of fibres which extends
to the corpora  quadrigemina, processus cerebelli ad testes; the middle
layer passes  to the  medulla oblongata, the restiform bodies; and  the
inferior peduncle consists of transverse fibres (Pons Varolii),  which
pass to the opposite side, and also form a considerable portion of  the
mesocephale.
   Lesions of the cerebellum, when so deep seated  as to affect  the
primary  planes of fibrous matter or the central stem, have the same
crossed  effect as those of the cerebellum.  This is not so obviously
explicable as the similar instance of the cerebrum, for the cerebellar
fibres of the medulla  oblongata  (restiform bodies) do not appear to
decussate.   Yet it  seems scarcely necessary, in order to  explain  the
phenomenon, to have recourse to the supposition that they do decus-
sate.   The  close connection between the restiform bodies and  the
pyramids, by means of the arciform fibres, renders the latter exceed-
ingly liable to sympathise with the condition of the former, and, there-
fore, prone to propagate the morbid influence to the  opposite half of
the spinal cord, and through that to the opposite half of the body.  It
must be  borne in mind that some of the fibres of the anterior pyra-
mids very probably derive their origin  from the central gray matter of
the medulla oblongata, as well as of the mesocephale, and that some,
at least,  of those  which affect the right half of the cord, probably  de-
rive their origin from the left side of either or both of those segments
of the encephalon.   That lesion of one hemisphere of the cerebellum
may influence  the  corresponding half of the medulla oblongata, is
likely, from the connection which the restiform fibres establish between
them.   The  connection of the  cerebellum with the  mesocephale is
most clearly  established by means of the  transverse fibres which con-
stitute the pons Varolii.
   Respecting the intimate structure of the cerebellum, little is known
of a very exact nature.   The white stems and plates are  fibrous, and
consist  of  multitudes  of  nerve-tubes  of all  sizes, which follow  the
general direction of each stem or plate.  These fibres doubtless tend
principally to propagate the peculiar influence of the cerebellum to  the 
248
INNERVATION.
spinal cord and the mesocephale.  Some probably are commissural,
as the  processus  cerebelli ad testes (or cerebro-cerebellar commis-
sures), the fibres of the pons, and some of those of the median lobe.
Mr. Mayo supposes that others pass between the laminse, but  their
existence is extremely doubtful.
   The vesicular matter which covers the plates  contains  the ordi-
nary elements, of  which, however, the caudate  vesicles constitute a
principal portion (p. 198).  These are so disposed that their processes
pass off chiefly towards  the  circumference, their  obtuse extremities
being directed towards  the laminae.   Besides these, there is in  each
layer of vesicular matter a thin lamina composed of round  clear nu-
cleus-like particles, which cohere to each other without the interven-
tion of any matrix or  other connecting substance.   Fine nerve-tubes
and  blood-vessels pass through  it.  This lamina is intermediate to
two which contain nerve-vesicles, one of which  is in immediate  con-
nection with the fibrous matter of the  cerebellum, the other with the
pia mater.
   Of the fourth  ventricle.—The  divergence  of  the  restiform bodies
in their ascent to the hemispheres of the cerebellum leaves a  con-
siderable space, which  is of a lozenge  shape, having its superior
angle towards  the brain, its lateral  angles towards  the cerebellar
hemispheres, and  its  inferior angle  at the point of separation  of
the restiform bodies.  Along its  floor  are seen the central or olivary
columns of the medulla oblongata, extending upwards  to  the optic
thalami.   A  fissure,  continuous  with  the posterior median fissure,
separates these columns.   Some  bundles of white fibres, which may
be traced to the  soft portion of the seventh pair of nerves, cross these
bundles  nearly at  right angles to them  and to  the  fissure (p. 242),
and form with the latter the calamus scriptorius, the white fibres con-
stituting the barbs of  the pen.  The roof of this  ventricle is formed
in front by the anterior  lamina?  of the superior vermiform process,
which constitute  the valve of Vieussens; and behind by the inferior
vermiform process.  A  process of pia mater enters  it at its inferior
angle, just as the choroid plexus  penetrates the  inferior cornu of the
lateral  ventricles of the brain. The reflexion of the lining membrane
on the process of pia mater  seems to  close up the ventricle below,
and cut off its direct communication with the subarachnoid space.  A
canal, which passes  through  the  mesocephale,  establishes the com-
munication of this with  the  third ventricle, iter a tertio  ad quartum
ventriculum.
   The fourth ventricle properly belongs to the medulla oblongata.  It
is, therefore, present  in all the vertebrate classes,  and is, in point of
size, directly proportionate to the medulla itself.
   Of the mesocephale.—This term, suggested by  Chaussier, denotes
that this portion  of encephalon is the  bond of union to the rest, the
cerebrum above  the medulla oblongata below, and the  cerebellum
behind.
   The inferior surface of the mesocephale, the pons Varolii, consists
of a series of curved fibres, which pass from one crus cerebelli to the
other.   When the brain  lies  with its base uppermost, these fibres ap- 
THE MESOCEPHALE.
249
pear to cross over the upward continuations of the anterior pyramids,
as a bridge over a stream.  Hence the term pons was applied to them
by Varolius.*  The fibres form a series of curves, convex forwards,
concave towards  the  medulla oblongata, the  posterior being much
less curved  than  the anterior.   At either side  they  become  more
closely packed, taper, and form the inferior layer of each crus cere-
belli.  Along the middle line a groove traverses the surface  of the
pons from its posterior  to its anterior margin, in which the basilar
artery usually lies.
   The fibres of the pons are always developed in the  direct ratio of
the hemispheres of the cerebellum.   In animals which have only the
median lobe, there is no pons; and when the hemispheres are  small,
the pons is small likewise.   Hence these fibres must be regarded  as
especially belonging  to the  cerebellum,  and  as serving,  whatever
other office they may perform, to connect  the  hemispheres  of oppo-
site sides.   They constitute, therefore, the great transverse commis-
sure of the cerebellum, and are to the  hemispheres of that organ what
the corpus callosum is to those of the brain.
   These  transverse  fibres do not form merely a superficial  plane,
which covers the pyramids in their upward passage : on the  contrary,
they extend  to more  than one-half  of the depth of  the mesocephale,
as is apparent on  a  transverse section of  it.   The  more superficial
fibres simply cross from one side  to the other;  the deeper-seated ones
interlace with those of  the pyramids.  The fibres are irregularly dis-
posed in planes, and  vesicular matter is interposed between  the more
deeply-seated ones.   From this  gray matter it is  not improbable that
some of the  fibres of the pyramids may take origin.
   On the superior surface of the mesocephale are the quadrigeminal
bodies, {nates and testes,) and beneath these the olivary columns.  A
slight longitudinal groove separates the quadrigeminal bodies  into a
right and  left pair, and  a transverse groove indicates  their division
into an anterior and posterior pair.   They are gangliform bodies, of
a  grayish white  colour, containing  fibrous  and vesicular matter.
The anterior {nates) are  somewhat  elliptical  in shape; they are the
larger in man.  The  posterior {testes) are  hemispherical, and  some-
what lighter  in colour.   These bodies are  much  more developed  in
the lower animals than  in man.   In mammalia only do they exist as
four.  In  birds, reptiles, and fishes, they  are  only two  in  number,
and are called optic lobes, from their connection with the optic nerves.
They are  hollow in these classes, but in mammalia they are  solid.
   Between   each  testis  and the corresponding  hemisphere of the
cerebellum, a band of fibrous matter  extends—processus cerebelli ad
testem.   Each band may be traced into the crus cerebelli of the same
side, of which it forms the superior layer,  so that  its fibres are doubt-
less continuous with  some of those which form  the white  plates of
the median and lateral lobes.   The  connection  of these  processes
with the testes is more apparent than  real.  They seem rather to pass
beneath them to the optic thalami; and, therefore, it has been justly
  * The terms  annular protuberance, isthmus, encephali, nodus encephali, are also fre-
quently used.
     17 
250
INNERVATION.
remarked, they might be more appropriately named processus cerebelli
ad cerebrum.   The valve of Vieussens occupies the interval between
these processes.  This layer evidently results from the spreading out
of some of the anterior lamellae of the superior vermiform  process.
  From the preceding description,  it will  appear, as before stated,
that the stem of fibrous matter which forms the crus cerebelli derives
its fibres from, or is continuous with,  three planes of fibrous matter;
the highest, or  most superficial, being the processus cerebelli ad tes-
te ni; the second,  or middle, the restiform body ; and the inferior the
fibres of the  pons.   By the first,  the  cerebellum  and  cerebrum are
connected ; by the second the cerebellum is connected with the  me-
dulla oblongata ;  and by the third, each hemisphere  is brought into
union  with its fellow, and with the  mesocephale.   Foville assigns
other fibres as constituents of the crura cerebelli, which he describes
as expansions connected with the fifth and auditory nerves.
  The crura  cerebelli seem  to emerge from the posterior  angles of
the mesocephale.  From its anterior part there proceed  upwards,
with  a slight  divergence,  two  similar  processes, of  considerable
thickness, which  enter each hemisphere of the  brain, and  upon which
each of those masses rests, as a mushroom upon its stalk.
   A septum of a  similar kind to that described in the medulla oblon-
gata is found in the mesocephale.  The fibres derived from the super-
ficial layer of the pons  pass  backwards from the median groove to
the posterior  and  superior part of the  mesocephale.
   Of the  cerebrum.—The constitution of each  crus  cerebri may be
best  understood by examining a transverse section made  a  little be-
yond its emergence from the mesocephale.  Upon the surface of such
a section three  planes of nervous matter  may be distinctly  observed.
The  inferior one  is composed of fibrous matter,  continuous below
with that of the mesocephale, and the anterior pyramids, and which
passes upwards to the corpus striatum.  Immediately above it is a
remarkable mass  of  a peculiarly dark, almost  black,  matter, which
constitutes the well-known locus niger of the crus cerebri.  It con-
tains large caudate vesicles, abounding in pigment, with nerve fibres
passing among them, or originating from  them.   This  black  layer
does not extend beyond the crus.  It forms a  partition between the
inferior or fibrous layer, and  a superior one, which  composes the
principal  portion of the crus.  This consists  of a grayish matter,
continuous with the central portion of the medulla oblongata, or the
olivary columns,  and passes into  the optic thalami.
   The optic thalamus and corpus striatum are large  ganglia formed
upon the anterior and upper extremity of each crus, and with which
the nervous matter of its upper and lower planes appears to be inti-
mately connected.  The optic thalamus is manifestly continuous with
the superior  plane, or olivary columns:  its colour and texture are
quite of the same nature with those of that plane; and when a longi-
tudinal section  of it is carried down through the  mesocephale and
medulla oblongata, no distinction is apparent between  the ganglion
and  the olivary column, so complete is  the  continuity of texture.
The colour of these bodies has been not inaccurately compared to that 
OPTIC THALAMUS AND CORPUS STRIATUM.         251
of coffee largely diluted with milk {cafe au lait).  This  arises from
the intermixture of vesicular matter with a  very close  interlacement
of fibres.
   The  corpus  striatum  has a  much  darker  colour than  the  optic
thalamus.  When a section of it is  made in an oblique  direction,
upwards and  outwards,  it exhibits the striated appearance whence
its name is derived. This arises from the passage of the fibres of the
inferior layer  of the crus into the vesicular matter of the ganglion.
The fibres do  not at first blend with the  vesicular matter,  as  in the
thalamus, but are collected into bundles, which are large at their en-
trance from the crus, but subdivide into much smaller ones,  diverg-
ing from each other, and radiating through the  ganglion in  various
directions, upwards, forwards,  outwards, and  backwards.
   WThen thin  sections  of the corpus striatum are examined by trans-
mitted light, the  smallest bundles of fibres observable in them appear
to consist of tubules reduced to their minutest dimensions, and closely
united to each other.   So compactly applied are they, that  very little
light passes through or between them.  Hence they appear to  be dark
masses lying in the substance of the  ganglion, and, from their  opa-
city, it is very difficult to determine  their  exact  relation to the ele-
ments of the  vesicular matter.  Many of  the bundles,  however,
appear to us to  attach themselves, at different parts of the  ganglion,
as if  around  a large  vesicle  of which, with its  nucleus, we have
sometimes seen  indications at one  extremity of the  dark mass  of
aggregated fibres.  Other bundles of  fibres appear to  emerge from
the corpus striatum, and to  contribute to form the fibrous  matter  of
the hemisphere.
   If this view of the  structure of the corpus striatum be  correct, it
would appear, that while a large proportion of the fibres which con-
stitute the inferior layer of the  crus penetrate  that  ganglion, many of
them do not pass beyond it.  They may be described as terminating
in it—or, more properly, if  traced from above, as taking their origin
or point  of departure from it.  Many of the fibres which seem  to
pass from the corpus striatum into the white matter of the hemisphere
are  doubtless similarly related  to the former body, i. e., take  their
rise from the vesicular matter, or, to speak more  exactly, pass  be-
tween the vesicular matter of the hemisphere  and that of the  corpus
striatum.  It is also highly probable that some fibres pass completely
through the corpus striatum.
   Thus, three sets of  fibres may be described as existing in the cor-
pus striatum; 1st, those which below enter into the formation of the
crus, and above  are connected with that ganglion ; 2dly, those which
are connected inferiorly with  the corpus striatum, and above with
the cerebral  convolutions; and lastly,  those which  pass from the
white substance  of the hemispheres through  the corpus striatum to
the crus cerebri.  And  of  these three sets of fibres, the first serves
to connect the corpora striata with the mesocephale  and medulla ob-
longata ;  the second to  connect the  cerebral convolutions with the
corpora striata;  and  the third  to connect the convolutions with the
mesocephale and medulla oblongata.  It must be confessed, however, 
252
INNERVATION.
that the evidence upon which the existence of the third class of fibres
rests is less  satisfactory than  that for the first and  second, although
most of those  anatomists who are  contented with  coarse dissection
seem to recognize only the third class.
  The fibres of the optic  thalamus are doubtless, also, continuous
with some of those which form the white matter of  the hemispheres;
and from the intimate manner in which this body is embraced by the
corpus striatum,  and the  close  connection  which exists  between
them, there  can be but little  doubt that  fibres  pass from the  one to
the other.
  Projecting from the external and posterior part of each optic thala-
mus, there are two small gangliform masses, similar in colour  and in
structure to  that body.  These are the  corpora geniculata, externum
and internum (fig. 71, g).   Some fibres of  the  optic tracts appear to
form a connection with them. By a transverse  section through either
geniculate body into the substance of the thalamus, the  distinctness
of the former may be demonstrated.
  A fissure  which exists between the optic thalami  is called the third
ventricle.  Its roof  is formed by the velum interpositum, one  of the
principal internal processes of the pia mater.   It contains a  bridge
of soft  grayish matter, extending  from  one optic thalamus  to  the
other.   This is called the middle or soft  commissure.
  The free and continuous surface of the optic thalamus and  corpus
striatum, which  projects into the anterior and middle  part of each
lateral ventricle,  is covered  by a delicate  epithelium, which  is con-
tinuous  with, and of the same nature as, that which  lines the whole
interior  of   the ventricle.   This  epithelium is, probably, ciliated.
Beneath it we find a layer of nucleus-like particles, which also  extend
over the whole internal surface of the ventricles.
  The pineal body, or gland  as it has been miscalled, is placed  im-
mediately behind the posterior extremity of the third ventricle.   It
is a cone-shaped  body,  of  a  dark gray colour,  intimately connected
with the deep surface of the  velum interpositum, a process  of which
encloses it and adheres  closely to it.  It rests in a groove between
the nates:  its base  is turned forwards towards the  third ventricle,
and its apex is directed downwards and backwards.  No part of its
base is contained in the third ventricle ;  but it  is  connected  to the
inner surfaces  of the  thalami by some  fibres  which  pass  forwards
from each angle of  its base.   These are called the peduncles  or ha-
bena, of the pineal  gland.  A  cord of transverse fibres,  some of
which appear to be  continuous with the peduncles, is situated beneath
the base of the body; most of these fibres are connected with the pos-
terior extremity of  each thalamus, and  constitute what  is called the
posterior commissure.
   The  pineal body consists  principally of large nucleated vesicles,
and contains some  tubular fibres.  In a cavity which  is formed  to-
wards its base, is contained a mass of sabulous matter, which  is com-
posed of phosphate  and carbonate of lime.    To this Soemmering
gave  the name  acervulus.   It is found  only in subjects after seven
years of age, and is in a great degree peculiar to the human subject. 
THE CEREBRAL HEMISPHERES.
253
  The structure of the pineal body is very imperfectly known;  and
although its office has been a theme  for some of the wildest specu-
lators in physiological theories, we are still utterly in the dark respect-
ing it.
   Of the Cerebral  Hemispheres.—The hemispheres of the brain are
ovoid masses, which in man constitute by far the largest portion of
the encephalon.  All that mass of nervous matter which is external
and superficial to the optic thalami and corpora striata constitutes the
hemispheres properly so called.   A vertical fissure separates the right
and left hemispheres, which, although not perfectly symmetrical, very
closely resemble each other.  This fissure contains the great falciform
process of the  dura mater, which thus forms a septum between the
cerebral hemispheres.
   When  a horizontal section is made through either hemisphere, an
oval surface is exposed {centrum ovale of Vieussens), which consists
of  an area of white or fibrous matter, bounded by a waving margin
of gray.   The latter is about an eighth of an inch in thickness: it  is
covered on its exterior by pia mater, from which innumerable minute
vessels penetrate it; and  within it adheres intimately to the white
matter, the fibres of which extend into it, and mingle with its  ele-
ments.
   In examining the surface of a hemisphere from which the pia mater
has been stripped, the peculiar folded arrangement of it  is manifest.
These folds, commonly known as  the convolutions of the brain, re-
semble  the rugae which are produced in the mucous membrane of the
stomach when its muscular coat is very much contracted.  They are
evidently destined  to  pack into a small compass a  large surface of
vesicular matter.   A  sulcus separates each convolution from the
neighbouring  one.   The  gray matter  is found  at the bottom of the
sulci, as well  as  upon the prominences of the folds, and its union
with the fibrous matter takes place equally  in the  one as in the other
situation.  A  sulcus,  therefore, contains  the gray  (vesicular)  and
white (fibrous) elements as distinctly as a fold or  convolution.  It  is
evident, that if the surface of the  gray did  not  exceed  that of the
white matter, folds  or convolutions would not  be necessary, but a
simple expanse of the former would suffice  to cover the surface of the
latter.  The convoluted  arrangement  increases the vesicular surface
to  an immense extent, without occupying much additional space;
and,  by the prolongation of the fibres, which correspond   to the con-
cavities of the convolutions, some distance beyond those which pene-
trate  the gray matter of the sulci, the fibrous matter is adapted to it.
   The  existence of convolutions on the surface of the hemispheres
affords evidence of a large relative amount of the  dynamic or vesicu-
lar nervous matter in those segments of the brain, and their number
and complexity are a  measure of the  extent to which the vesicular
surface is increased.  Of two brains, equal as  regards bulk, and occu-
pying the same space, that which has the more numerous convolutions
on  its surface  has the greater quantity of vesicular matter, and  must
be  regarded as physiologically the more potential.
   A remarkable gradation  is observable as regards the number of the 
254
INNERVATION.
cerebral convolutions from the lowest mammalia up to man.   Some
of the Rodentia,  Cheiroptera, and Insectivora, occupy the  lowest
place; and monkeys, the elephant, and the whale, rank next to Man,
in whom the convolutions reach their highest point of  development.
In the rat, mole, &c, the surface of the  brain  is perfectly smooth;
and  the  only tendency to  complication which it exhibits, is  to  be
found in the convolution of the gray matter at the fissure of Sylvius.
The brains of these animals resemble, in this  respect, to a striking
degree, those of birds, which are equally destitute of all semblance
of a convolution.  But  in  the rabbit,  guinea-pig,  beaver, &c, the
occurrence of certain fissures on the surface of the hemispheres, and
the greater depth of the fissure of  Sylvius, denote the first steps in
the development of convolutions.
   A further stage of development  is  indicated  by the existence of
certain rounded folds which generally take a  direct course parallel to
the long axis of the hemispheres.  These folds are but few in number,
and  quite simple, but may be  readily distinguished from the  rest of
the cerebral surface, by the fissures which bound them.
   However complicated  and numerous the convolutions of the most
highly developed brains may be, it  cannot be supposed that their ar-
rangement is accidental,  or has reference merely to  the space within
which the brain is enclosed.  On the contrary, there seems no doubt
that the position,  size, and connection of  certain primary folds influ-
ence mainly the number and variety of those  which occupy the inter-
vening  spaces.   This interesting point  has been  strongly insisted
upon by M. Leuret, who shows, by comparison of the most completely
convoluted brain  with those in which  the folds are few and simple,
that the convolutions of the latter, which  are, as  it were, the original
landmarks in this  intricate  arrangement of the cerebral surface, may
be  demonstrated  in each successive group of brains which form a
stage in the ascending series.
   Taking the brain of the fox as  the  standard of comparison, M.
Leuret* describes in it six obvious convolutions, prominently marked
on the surface of  its hemispheres.   Four of these  are external, the
uppermost of which occupies also the principal portion of the supe-
rior  surface; one  is internal, and situate  immediately above and
parallel to  the corpus callosum ; while the  sixth is on the inferior
surface of the anterior lobe, and rests  upon the orbit, whence it is
named supra-orbitar.   Of the four  external, the inferior one bounds
the fissure of Sylvius above, in front, and behind : and its relation to
that fissure enables the observer to  distinguish it very readily.  The
three remaining  ones, curved similarly  and parallel  to  the first, and
to each other, occupy the remainder of the external, and, in part, the
superior surface of the hemisphere.
   M. Leuret distinctly traces these convolutions in other groups of
animals in which the general organization of the brain has manifest-
ly acquired  a considerable increase.   Some of them, however, are

  * Professor Owen  has pursued the same subject extensively, and has given his
results in his lectures at the Royal College of Surgeons ; but we believe these have
not yet been published. 
CONVOLUTIONS OF THE BRAIN.
255
fissured,  or  exhibit  a tortuous appearance;  or one or more small
folds unite neighbouring convolutions  at one or more  points ;  or a
fissure may be of such depth as to divide  a  convolution at one ex-
tremity into two, either or both of which may form a  junction with
others.   Thus, from a few  primary or fundamental convolutions, a
highly complicated  surface of the  brain may be  formed,  by their
subdivision,  by their  tortuosity,  and  by their junction at various
points, through  the  intervention  of straight or tortuous secondary
folds.
   In  some animals,  however, the primary convolutions may even be
less numerous than those above mentioned ; and  yet  the surface of
the brain may appear more complex, owing to the tortuosity of those
which do exist, and their subdivision into, or junction with, numerous
secondary folds.  This is the  case in  that  group of which the sheep
forms the type.  There are  but two  primary convolutions  on the ex-
ternal surface, one  of which  corresponds  to  that  of  the fissure  of
Sylvius in the fox, the other  to the one immediately above it; and
there are the internal convolution  and  the  supra-orbitar one, making
in all only four primary convolutions.  Yet the surface  of the sheep's
brain exhibits a much greater number  of folds than that of the fox.
   On the other hand, when the brain has acquired  an enormous
increase of size, as  in the  elephant and in man, new convolutions
seem to  be added to the primary ones met with in inferior groups, and
the secondary folds are greatly increased in number. The additional
convolutions are found chiefly at the superior and anterior part of the
hemisphere.
   In  the human brain the following convolutions are constantly pre-
sent,  and resemble  the  primitive ones, which have  been  already
referred  to in the brains of the inferior animals.   The internal one is
always well marked  ; it lies parallel  to the  corpus callosum, overlap-
ping it slightly on either  side.  In front it winds round the anterior
margin of the corpus callosum, and  is connected with  the convolu-
tions of  the anterior lobe  ; posteriorly  it divides, appears to be con-
tinuous with some posterior convolutions, and passes into  the middle
lobe  forming the hippocampus  major.  Numerous small folds pass
from  its  upper edge to the superior convolutions.    The supra-orbitar
convolution is well  developed, and  bears a constant relation to  the
fissure for the olfactory process.   The fissure  of Sylvius is  bounded
by a tortuous external convolution, which forms numerous connections
with  others on the  external surface  of the brain.   In  this fissure is
found constantly a group of shallow convolutions,  which form what
has been called by Reil the island, insula, from their isolated position,
having  only deep-seated  connections  in the vicinity  of  the  corpus
striatum.  Some longitudinal  convolutions are found on the superior
and on  the inner surfaces  of the hemispheres, uniting with  neigh-
bouring  ones by means of numerous transverse folds.
   According to Leuret,  that only can be properly  called  a  convolu-
tion wThich is primary ; and these, for  the most part, take a  direction
in the length of the brain.   Those  which  form angles with the pri-
mary convolutions  are, in  his estimation, mere folds   derived from 
256
INNERVATION.
them, and connecting them  to  others.  When the convolutions are
very highly developed, as in man and the  elephant, their numerous
undulations  obscure in a great degree their real  direction.   Hence
many of the primary convolutions in  the  human brain seem to  take
a vertical direction.
  There are, however, other differences in the convolutions, whether
of the brains  of the same or  of different groups, besides those depend-
ent  on form  and degree of undulation.  These are referable  to their
depth and their thickness.   Animals,  even of the same group, or  of
the  same species, exhibit much variety with respect to these points.
The wolf has precisely the same  convolutions as the fox ;  but those
of the former are deeper, and thicker, as well as more undulating
than those of the latter.  Much difference is also observable in these
respects in the human brain.   The convolutions of the female brain
are  not  so deep nor so thick as those  of the male.   Age, too, causes
a marked  difference.   The convolutions  of the child just born,
besides  being much more simple, and having fewer undulations, are
less deep and less thick than those of the adult; and in old age, when
the  brain  has shrunk, the mental faculties  being  less vigorous and
active, the convolutions have become much smaller in every dimen-
sion, and water is apt to accumulate in the intergyral spaces.
  In man, the  convolutions of the right and left hemispheres do not
present  a perfect symmetry.   It is important, however, to notice, that
careful  examination  will invariably display the  same  essential con-
volutions on each side, although they present such striking differences
in detail that it is at times difficult to  recognize the  likeness  ; and it
is not a  little  remarkable, that, in  general,  the lower the development
of a brain, the more exact will be the symmetry of its convolutions.
Thus the brains  of all the  inferior mammalia, even of those which
make the nearest approach to  man,  are exactly symmetrical.   The
imperfectly developed brain  of the child exhibits a similar symmetry;
and that of the inferior races of mankind,  in whom the neglect  of
mental culture, and habits approaching those of the brute, are opposed
to the growth of the brain, also presents a symmetrical disposition  of
the  convolutions.
  A convolution  consists of a fold of the  gray, or vesicular  matter,
enclosing a process of the fibrous.  The gray  matter of neighbouring
convolutions  is obviously continuous throughout at the bottoms of the
sulci, so that  it forms one unbroken although  undulating sheet over
the  whole convoluted surface of the brain.   That portion of the gray
layer which is in contact with the pia mater is purely vesicular, i. e.,
unmixed with nerve-tubes, with the exception of a few stray  ones on
the  surface;  but  blood-vessels penetrate  it in very great  numbers.
The more deeply seated portion, however, contains very  numerous
tubular fibres, which become larger as they approach the white matter.
It is very plain, that a large  proportion of the constituent fibres of the
white matter of  the convolutions penetrate  the gray matter:  these
appear to  enter it  more or  less at right angles to that portion of the
gray surface with which they are  more immediately in relation ;  and,
on the other hand, they converge  inwards towards the central  parts of 
COMMISSURES OF THE BRAIN.
257
  the brain, the corpora striata and optic thalami.   A large proportion,
  therefore, of the white substance  of the  hemispheres,  the  centrum
  ovale, consists of fibres which establish a communication  between the
-  gray undulating surface and these central gangliform bodies.
     We are  unable, however, to  state that  all the fibres  of the  con-
  volutions take this  inward direction.  Some of them,  it  has  been
  asserted, pass from convolution to convolution,  uniting those imme-
  diately adjacent, as well as the  more remote.  Such  fibres, did they
  exist, would  pass at right angles to those above described, and parallel
  to the gray surface.   They would constitute intergyral commissures.
  But the existence  of such  a series of fibres rests on  a foundation too
  uncertain to  warrant us in  speaking confidently respecting it.  When
  a  brain which has been hardened by long immersion in  alcohol is
  torn along the surface of the convolutions, the  torn surfaces take on
  a fibrous appearance.   But nothing of the kind can  be shown in the
  fresh brain, in which the  direction of the fibres which  converge to
  the corpora striata may be as easily demonstrated as upon the hardened
  one.
     The gray  matter of the  convolutions does not exhibit a uniform
  colour throughout its  entire thickness.   Much  depends, as regards
  the depth  of colour of the whole layer, upon  the quantity of blood
  in its vessels.   Compare  the gray matter  of an anaemic brain  with
  that of a healthy one, or, still more, of  a  congested one, and the
  difference  cannot  fail to strike  the  most  superficial observer.  The
  external  portion has  the darkest colour, and the internal in general
  the lightest.   In some convolutions, however, the intermediate  layer
  is  white, and appears on the section  like a white line  separating the
  inner from the outer layers.   This is very obvious in the convolutions
  forming the exterior  of  the descending horn of the lateral ventricles.
  This white layer contains fine nucleus-like particles, similar to those
  which form the intermediate layer of the gray matter of the cerebellum;
  a coincidence of structure between certain convolutions of the brain,
  and the gray matter of the  cerebellum, which, doubtless, is  not with-
  out some physiological  significance.
     Certain  systems of fibres  exist in  the cerebrum, which seem very
  evidently to  unite portions of the same, or of opposite hemispheres.
  The most obvious of these commissures  are, the  corpus callosum, the
  anterior commissure, the posterior commissure, the soft commissure, the
  superior  longitudinal commissure,  and the fornix.   All, except the
  two last, are  transverse, and unite parts of the hemispheres of opposite
  sides.
     The corpus callosum is a thick stratum of transverse fibres, bent at
  its anterior and posterior extremities, situate between the hemispheres,
  and forming  a floor to a portion of the  great median fissure which
  separates them.   Its fibrous  structure is very apparent to the naked
  eye, the  fibres being collected  in  coarse bundles.  On each  side it
  penetrates  into the hemisphere, under cover of the internal convolu-
  tion already mentioned, which  overhangs it in its entire length.  It
  thus connects the anterior, middle, and part of the posterior lobes of
  each hemisphere; at  least, its fibres penetrate the hemispheres at these 
258
INNERVATION.
parts.  Foville describes the fibres  of this commissure  as being de-
rived partly  from the posterior columns of the medulla oblongata,
from the  optic thalami, from  the corpora striata, and, lastly, from the
fibrous matter of the hemispheres ; and although the demonstration of
these numerous  sources of  origin of these fibres is attended with
much difficulty, it nevertheless seems highly probable that the  nume-
rous fibres, of which so extensive a  stratum  is formed, would  derive
their origin from several sources.
  The corpus callosum is  crossed from  before backwards along the
median line  by two  stripes  of longitudinal fibres, which, although
easily separable, generally lie in close apposition with each other and
form a kind of raphe, dividing  the upper surface of the corpus callo-
sum into  two  equal and symmetrical portions.   These fibres seem to
be commissural in their office.
  The anterior commissure is  a remarkable bundle of transverse fibres;
which passes  from one hemisphere to the  other.   It is in its  centre
a cylinder of fibrous matter, a little  thicker than a crowquill, but
becoming very much flattened  and expanded at its extremities.  Its
central part is seen at the anterior  extremity of the  third ventricle, in
front  of the anterior pillars of the fornix, crossing  from  side to side,
quite free, and unconnected with nervous  matter.  It plunges on
either side into  the anterior extremity of the  corpus striatum, and,
passing through it, its fibres diverge and  spread out into the  white
matter at the floor of the  Sylvian fissure, and near the  anterior per-
forated space.
  The posterior commissure  crosses  the posterior  extremity  of the
third  ventricle, and  passes transversely  between the  optic thalami.
It is  a slender cylinder of  fibrous  matter, which lies  immediately
above the anterior orifice of the aqueduct of Sylvius.   On each side
it seems to sink into the posterior part  of the  optic thalamus.   The
base  of the pineal body rests upon  it, and is  connected with  it by
fibrous matter, which is continuous with the peduncles.
  The soft commissure is a soft pale-gray layer consisting of vesicular
matter with nerve tubes, which  stretches from one optic thalamus to the
other, having no other connection, and being free on its upper as well
as its under surface.  This layer, thus extended horizontally between
the thalami, divides the third ventricle into a superior and an inferior
portion.   As it comprises vesicular  matter, it is not a commissure in
the same sense as the others, which  contain none.
  The superior longitudinal  commissure is enclosed in the internal
convolution overhanging the corpus callosum.   Posteriorly it  passes
over the posterior border of the corpus callosum, to the under part of
the middle lobe, where it is chiefly connected with the hippocampus
major.  Anteriorly it winds over the front  border of the  corpus callo-
sum to join the lower convolutions of the anterior lobe in front of the
fissure of Sylvius.   Thus it takes a course similar to that of the fornix,
though more extensive and superficial.
  The fornix or vault is the most  extensive, and in every way the
most  remarkable  of the cerebral commissures.   It  is placed  imme-
diately beneath the corpus callosum, with the posterior half of which 
COMMISSURES OF THE BRAIN.
259
it is  intimately connected, and from which it  is with difficulty sepa-
rated.   A  principal portion of the fornix  consists of a  horizontal
lamella of  fibrous matter, parallel to the corpus callosum, of a trian-
gular shape, with the apex forwards {corpus fornicis).   The base is
enclosed by the posterior reflection of the corpus callosum, the termi-
nal transverse fibres of which are seen on its inferior surface, forming
the appearance which has been designated lyra.
   The fornix may be divided along the middle line into  two equal
and  symmetrical portions, one belonging to each hemisphere.   Suf-
ficient indication of its double form is  evinced by the prolongation
from its apex  of two cylindrical cords, which  curve forwards  and
downwards, then backwards, with their convexities touching  the
posterior border of the anterior commissure.  These are the anterior
pillars  of  the  fornix.  In  their  descent they diverge slightly from
each other, leaving an  interval  between them, through  which the
anterior commissure appears.  These pillars form the anterior boundary
of the foramen commune anterius, through which the lateral ventricles
communicate with the third, and with  each  other.
   Each anterior pillar of the fornix in its descent  penetrates the an-
terior and inner part of  the optic thalamus.  Here it is surrounded
by vesicular  matter, which may be readily  scraped  away  from it.
Numerous striae of fibrous  matter join the pillar as it passes through
the vesicular matter ; their constituent fibres, doubtless, being derived
from the thalamus.  Finally, each pillar terminates in a small spheri-
cal  body at  the base of the  brain.   These bodies called  corpora
mamillaria, are  white outside, but when cut  into, exhibit  a reddish-
gray colour, like that of the optic thalami.  They contain nerve-tubes
and  vesicular  matter in considerable quantity,  and therefore resemble
ganglia in structure.  A considerable fasciculus of fibres connects
each mamillary body  with the optic thalamus.
   From each angle of the base of the  fornix a broad band of fibrous
matter passes  outwards, and spreads partly into  the posterior horn of
the lateral ventricle, and partly into  its descending horn.   These
bands constitute the posterior pillars  of the  fornix.  They connect
themselves wTith certain convolutions which project into the posterior
and  inferior cornua  of the  lateral  ventricles ; in the latter with the
hippocampus minor, and in the former with the hippocampus major.
   The fornix  consists of  longitudinal fibres, unmixed with vesicular
matter, save in the optic  thalami and corpora mamillaria.   The supe-
rior  surface of the body of the  fornix is connected to the inferior
surface of  the corpus callosum, at its base  apparently by  the  direct
adhesion  of the fibres of the two planes, but  towards  its apex by
the septum lucidum, which extends vertically from the middle line of
the  inferior surface of the  corpus  callosum to that  of the superior
surface of  the fornix.
   From the great extent of the fornix, and the numerous connections
which its pillars form, it  is plain that it  must  serve as a commissure
to many and distant parts.   Each  half of it is a longitudinal or antero-
posterior commissure for  the hemisphere of its  own side.  It is not
improbable that some of the  convolutions contain antero-posterior 
260
INNERVATION.
commissures for the superficial part of the hemisphere ;  such is cer-
tainly the case with the longitudinal convolution above the corpus
callosum.  The fornix, however, connects  deep-seated  parts, for it
passes between the optic thalamus  and the deep convolutions of the
posterior and middle lobes.
  The septum lucidum consists of two layers of fibrous matter, which
enclose a space or cavity called the fifth ventricle.  The  fibres of this
layer radiate upwards and forwards, and connect the anterior pillars
of the fornix with the corpus callosum.   Each fibrous layer is covered
on its outside by a layer of nuclear particles, which again is covered
by the membrane of the lateral ventricle.
  A band of fibrous matter, which belongs to  the  same system  of
commissural fibres as the fornix, is found, on each side, in the groove
between the corpus striatum and  optic thalamus.   This is called tania
semicircularis.   It may be described as  connected with the corpus
mamillare, in much the same way as the anterior pillar of the fornix.
Traced from this point, it is found  to penetrate the  optic thalamus,
following the general  course of the anterior pillar of the fornix, but
slightly diverging  from it, and to emerge from  the  thalamus in the
anterior part of the groove between it and the corpus striatum, whence
it passes backwards, outwards, and  downwards into the inferior cornu
of the lateral ventricle.
  Other structures exist in the brain, which seem likewise  to act  as
commissures to the parts between which they  are placed.  Thus,
between the crura  cerebri a layer of fibrous matter, mingled with a
few vesicles, is placed, which fills up the angle  formed at their diverg-
ence ;  this layer is remarkable  for being  perforated by numerous
foramina, which give passage to the blood-vessels of the locus niger.
It is called the pons Tarini; it probably connects the gray matter  of
the crura.
  The innermost fibres of the optic  tracts  are evidently commissural.
These fibres form  an  arch, which  crosses the  tuber cinereum.   In
the mole, they are the only fibres of the optic tracts existing:  those
which form the optic nerves are  not present.   These  fibres connect
the quadrigeminal  tubercles and the geniculate bodies of  opposite
sides.
  The tuber cinereum is a remarkable layer of vesicular  matter,  with
which nerve-tubes freely intermingle, which  extends from  the ma-
millary bodies forwards  to  the  posterior reflection of  the corpus
callosum, and has  intimate connections with  the anterior  pillars  of
the fornix, the optic tracts, the septum lucidum, and, at the floor  of
the third ventricle, with the optic thalami.  An infundibuliform tube
passes from it down towards the  pituitary gland, which  is situate  in
the sella Turcica.
  It is curious  how few are the fibres which seem  to  connect the
cerebrum and cerebellum.  The  only ones to which this  office can  be
assigned  are  those which  form  the processus  cerebelli ad testes.
Hence  these structures may  more fitly be denominated  cerebro-cere-
bellar commissures.  They extend between the cerebellum on the one
hand,  and the optic tubercles and thalami on the other. 
         PITUITARY BODY.—VENTRICLES OF THE BRAIN.      261

  Of the manner in which the commissures connect the various parts
between which they are placed, it is difficult to form an exact opinion.
Are the commissural fibres directly continuous with those of the seg-
ments  which  they unite? or do  they intermingle or  interlace with
them in some  intricate way, so that they may come into  intimate or
frequent contact?   Or, do they, like other fibres, blend with the gray
matter, and thus connect the really dynamic portion of the segments?
This latter view seems to be the most probable.
  The pituitary body ox hypophysis is a glandiform mass lodged in the
sella Turcica, and surrounded by the  coronary sinus.   It is connected
with  the  brain by the infundibular  process, the  small extremity of
which is attached to its superior concave surface.
  This body consists of two lobes,  of which  the anterior is much the
larger; and which  also differ in  point of colour, the  anterior being
of a yellowish gray, the posterior  more similar to the  gray matter of
the brain.   The former is  considerably denser  and firmer  than the
latter,  which does not differ in consistence  from the cerebral gray
matter.  The infundibulum  is chiefly connected with the  posterior
lobe.
  In point  of structure this body resembles  somewhat the  vesicular
matter of the brain.  We find in it large vesicles with distinct nuclei
and nucleoli lodged in a granular matrix, and between  them numerous
bundles  of white fibrous tissue.   These are most numerous in the
anterior lobe.  Its  use is quite unknown.
   Of the  Ventricles  of the Brain.—By  the  apposition  of the  two
hemispheres of the brain along the median plane, a fissure-like space
is enclosed beneath the corpus callosum and fornix, limited in  front
by the anterior pillars of the latter, and behind by the  posterior com-
missure; this is the middle or third ventricle.   This fissure  is closed
inferiorly by the pons Tarini, mamillary tubercles, and tuber cinereum ;
its roof is  formed by  the velum interpositum, a process of pia mater,
which separates it  from  the body of the fornix.  It communicates
posteriorly with  the fourth ventricle through the aqueduct of Sylvius
{iter a tertio  ad quartum  ventriculum), and immediately behind the
anterior pillars of the fornix it freely opens into each lateral ventricle.
At the same situation the velum interpositum and  the choroid plexuses
communicate with  each other.  The optic  thalami form the lateral
boundaries of the third ventricle, and its  cavity is crossed by the soft
commissure.
   The lateral  ventricles result from the  folding of  the  convoluted
surface inwards and downwards.  By their extension inwards, and
their junction along the median line by the corpus callosum, the
horizontal portion of each ventricle is enclosed;  and  by the  folding
inwards of the inferior convolutions, posterior to the fissure of Sylvius,
the  inferior horn is formed.  The horizontal portion extends into the
anterior lobe {anterior or frontal horn), and into the posterior  lobe
(posterior  or occipital horn).  The central part of the  horizontal por-
tion is separated from the third  ventricle by the body of the fornix.
In this portion of the  ventricle are seen the upper surfaces of the corpus
striatum and optic thalamus, with the taenia semicircularis between 
262
INNERVATION.
them, covered by the  lamina cornea.  The thalamus  is partly con-
cealed by  the  choroid plexus.   The descending or  inferior  horn
{sphenoidal horn) communicates with the body of the  ventricle just
behind the corpus striatum, and from that point  passes downwards
and  outwards, and then forwards  and inwards.  It contains a re-
markable convolution, the hippocampus major, which projects into it,
and is a continuation of that enclosing the superior longitudinal com-
missure ; this is covered by an expansion of fibrous matter continuous
with the posterior pillars of the fornix.   The posterior  horn contains
a similar but smaller convolution, called  hippocampus minor.
  The inferior horn of the lateral ventricle  contains a considerable
portion of the choroid plexus.   This enters at its inferior extremity
between  the hippocampus major and the crus  cerebri,  and passes
upwards into the  horizontal portion  of the ventricle.
  The fourth and the fifth ventricles have been already described.
  All the ventricles are lined by a very delicate  membrane, similar
in structure to serous  membrane.  It is covered by a fine epithelium
consisting  of polygonal scales, and provided with cilia, which were
first  observed by Purkinje and Valentin.  This epithelium  is found
covering the surface not only of the wall of the ventricle, but also of
the pia mater within it, the choroid  plexuses, and the deep surface of
the  velum interpositum.  It is  by means of  the reflection of this
membrane  upon the intraventricular processes  of  pia mater that  the
ventricles are closed at those points where nervous  matter does  not
exist, such as the inferior cornua  of the lateral ventricles, and  the
inferior  extremity of  the  fourth  ventricle.   There  is, therefore, no
direct communication  of these cavities at these points  with the sub-
arachnoid space; and, if fluid pass  from  one to the other, it must be
by filtration through the delicate ventricular membrane.
  In a state of health  there is little or no fluid in  the lateral or other
ventricles of the brain.  Their inner surfaces are doubtless in contact,
but lubricated with a  moisture, as  all serous  surfaces are.   When
fluid is found in them, it results either from changes which take place
after death, or  from  some morbid  process during life.  A  state  of
anaemia, or  an  impoverished condition  of the  blood, in which its
colouring  matter  and  its  fibrine  are found in  small  quantity, is very
favourable to the effusion of fluid into the ventricles.
  It  may serve, in some degree, to convey a clearer general idea  of
the anatomy  of the brain, if, in  conclusion, we  explain  the course
which the nervous force might, and probably  does  follow,  when
developed  in any particular segment of this complex organ.
 _ If we suppose the source of power to be the convolutions on either
side, the nervous force  would  be propagated by the fibres of the
hemisphere to the vesicular matter of the  corpus striatum ; from which
it would pass along the fibres of the inferior layer of the crus cerebri,
through the  mesocephale, to the anterior pyramids  of the medulla
oblongata; along which it would be conveyed to the opposite half of
the soinal cord, exciting the  nerves which spring  from  that segment.
Supposing this to be  the route  in which the  impulse  of volition is
propagated to the muscles, it  becomes very easy to understand why a 
THE CIRCULATION IN THE BRAIN.
263
state of paralysis must ensue, when an apoplectic clot, or other morbid
deposit in  any part of the  course above described, compresses  or
ruptures the fibres, or  when a state of softening  destroys their vital
powers, or causes a solution of their continuity.  If the seat of disease
be in the white matter, the  channels along which the nervous power
travels will be interrupted ; if it be in the gray matter, the sources of
nervous power are impaired.  In all cases the extent of the  paralysis
will be proportioned to that of the lesion, and for the  most obvious
reasons.
   If the cerebellum be the source of power, the nervous force will
travel from either hemisphere along the fibres of the crus, and by those
of the restiform body  to the spinal cord, and from  the  continuity of
the former with the posterior column of  the latter it is probable that
this column would  be  more immediately excited.
   So little is known of the precise channels through which impressions
created at the periphery are propagated  in the central organ, that we
can hardly do  more than  speculate on  the subject.   We may, how-
ever, fairly conclude, that those segments with which nerves admitted
to be sensitive are  in  close  connection, must be instrumental in  the
propagation of the nervous power, when excited  by sensitive impres-
sions ; and hence we  are  led to assign to the olivary columns of  the
medulla oblongata, and their continuations in the mesocephale, with
the optic  tubercles  and the thalami, a considerable share in this office,
inasmuch as the auditory, the fifth, and the optic nerves, are intimately
connected with them.  And admitting, for the present, that the hemi-
spheres are the common centre  of sensitive impressions, it is easy to
understand how nervous power, excited by the impulse of sound upon
the ear, for example, may be propagated along the auditory  nerves to
the  olivary columns in the fourth ventricle, and thence  to  the optic
thalami, in which are  found many fibres which  are  continuous with
those  of  the  hemispheres, and  capable  of propagating the nervous
force to the convolutions.
   To this it may, however, be objected, that perfect sensation is  fre-
quently co-existent with a cerebral lesion, sufficient  to produce very
complete paralysis  of motion, and that an enduring paralysis of sensa-
tion is a rare accompaniment of cerebral disease.  But such facts do
not so much  militate against these views, as they serve to denote that
the channels of sensation are more numerous than those  of motion ;
and that, if one route be  interrupted, another is easily opened.   It
may be, that the commissures are valuable instruments for this pur-
pose; and it is highly worthy of notice,  that no segment of  the cere-
brum  has  so many  commissures either with the opposite  or its own
side, as the optic thalamus.
   It should be borne  in mind that the  foregoing remarks are partly
conjectural,  and that they  are introduced  rather as a  convenient
form of illustration, than  as implying more than a probability of their
general correctness and accordance with the best established views.
   Of the  Circulation in the Brain.—An organ of such  great size, of
such high vital endowments, so active, and which exerts so  consider-
able  an influence  upon all other parts  of the body, must necessarily 
264
INNERVATION.
require a large supply of the vital fluid.  Hence we find that the
blood-vessels of the brain are numerous and capacious.   Four large
arteries carry blood to it; namely, the  two internal carotids, and the
two vertebrals.   Each carotid penetrates the cranium at  the foramen
on  the side of the  sella Turcica, and almost  immediately divides into
three branches, the anterior and the middle cerebral  arteries, and the
posterior communicating artery.
  The anterior cerebral arteries supply the inner sides of the anterior
lobes of the  brain: they ascend through the great longitudinal fissure,
and pass along the upper  surface  of  the corpus callosum, giving
off  branches to the inner convolutions of both hemispheres of the
brain.  These  arteries anastomose with each other just  beneath the
anterior margin of the corpus callosum  by  a transverse branch, called
the  anterior communicating artery.   The middle cerebral  arteries, the
largest  branches of the  carotids, pass outwards in  the  fissures  of
Sylvius, and supply the outer convolutions of the anterior lobes, and
the  principal portion of the middle lobes.   At the inner extremity of
each  fissure  of Sylvius  numerous  small  branches  of these arteries
penetrate, to be  distributed to the corpus striatum.  The choroid
arteries which  supply the choroid plexus sometimes  arise from these
arteries, but also  occasionally come  from  the  carotid  itself.  The
posterior communicating artery is an anastomotic vessel, which passes
backwards along the inner margin of the middle lobe on the base  of
the  brain, and communicates with the posterior cerebral  artery, a
branch of the basilar.
  The  vertebral  arteries, having  passed through the canals in the
transverse processes of the cervical vertebrae, enter the cranium through
the  occipital  foramen  towards  its  anterior  part.  In their ascent they
incline towards each  other in front of  the  medulla oblongata, and  at
the  posterior margin of the pons they coalesce to form a single vessel,
the  basilar, which extends the whole length  of the pons.
  The vertebral arteries furnish the anterior and posterior spinal arte-
ries, and the  inferior cerebellar arteries.   These last vessels arise from
the  vertebrals very near their coalescence, and pass round the medulla
oblongata to  reach the inferior surface of the cerebellum, to which
they are principally distributed.
  The basilar  artery sends numerous small vessels  to penetrate the
pons, and at  its  anterior  extremity divides into four  arteries two on
each side: these are, the  two superior cerebellar, and the two posterior
cerebral arteries.
  The  superior cerebellar  arteries  pass backwards  round  the crus
cerebri, parallel to  the   fourth nerve, and  divide   into numerous
branches on  the  upper  surface of  the  cerebellum,  some of which
anastomose with branches  of the  inferior  cerebellar  artery  over the
posterior margin of the cerebellum.  Some branches of these arteries
are  distributed to the  velum interpositum.
  The posterior  cerebral  arteries are the largest  branches  of the
basilar.   They diverge and pass upwards  and backwards round the
crus cerebri, and  reach  the  inferior surface  of the  posterior lobe,
anastomosing in the  median fissure with ramifications of  the anterior 
THE CIRCULATION IN THE BRAIN.
265
cerebral, and on  the  outside with branches of the  middle  cerebral
arteries.   Numerous  small vessels pass from this artery at its origin,
and penetrate the interpeduncular space, and one or two are distri-
buted to the velum.  Shortly after its origin the artery receives the
posterior communicating branch from the carotid.
  A remarkable freedom  of anastomosis  exists between  the arteries
of the brain.  This takes place not only between the  smaller rami-
fications, but likewise between  the  primary trunks.  The former  is
evident all over the surface of the  cerebrum  and cerebellum.  The
latter constitutes the well-known circle of Willis.  This  anastomosis
encloses a space, somewhat of an oval figure, within which are found
the optic nerves, the  tuber cinereum, the infundibulum,  the corpora
mamillaria, and the interpeduncular space.  The anterior communicat-
ing artery, between the  anterior  cerebral arteries, completes the circle
in front.  The lateral portion  of the circle is formed by the posterior
communicating artery, and it  is completed behind by the bifurcation
of the basilar into the two posterior cerebral arteries.   Thus, a stop-
page in either  carotid, or in  either  vertebral, would  speedily be
remedied.   The coalescence  of the vertebrals to  form  the basilar,
affords considerable security to  the brain against  an impediment  in
one vertebral; and, should the basilar be  the  seat of obstacle, the
anastomoses of the inferior cerebellar arteries with  the  superior ones
would insure a sufficient supply of blood to that organ.    If either  or
both  carotids be  stopped up, the  posterior communicating arteries
will supply  a considerable quantity of  blood to  the intracranial por-
tions of them; or, if one carotid be interrupted, the anterior commu-
nicating branch will  be called into requisition to supply  blood  from
the opposite  side.
   Obstruction to the circulation in  both carotids and  both vertebrals
is productive of  a  complete  cessation  of cerebral action, and death
immediately  ensues, unless the  circulation  can be quickly restored.
This was proved clearly by Sir  A. Cooper's experiments  on  rabbits.
The circulation  may, however,  be interrupted in both carotids, or  in
both  vertebrals, without permanent bad effect; or in one carotid  or
one vertebral, provided the condition of the  remaining vessels be
such as not to impede  the circulation  in  them.  In cases where the
neighbouring anastomotic branches are not sufficient to  restore the
circulation to a part from which it has  been cut off by the  obliteration
of its proper vessel, the cerebral substance of that region is apt  to
experience a peculiar form of softening or  wasting, which is distin-
guished by the absence of any discoloration by the effusion of blood,
and of any new matter.
   The four great channels of sanguineous  supply to  the brain are
continued up straight from the  aorta itself,  or from an early  stage  of
the subclavian.   The contained columns are  propelled very directly
towards  the base  of the  brain, through wide canals.   Were  such
columns to  strike directly upon the base of the brain, there can be
no  doubt it would  suffer  materially.   Considerable protection,  how-
ever, is  afforded to the brain ;  first, by the blood ascending against
gravity, during at least  a great portion of life ; secondly, by a  tortuous 
266
INNERVATION.
Fig. 72.
arrangement of both  carotids and vertebrals  before  they enter  the
cranial cavity, the carotid being curved like the letter S in and above
the carotid canal, and the vertebral being slightly bent between the atlas
and axis, then taking  a horizontal  sweep above the atlas, and after it
has pierced the occipito-atlantal ligament, inclining obliquely upwards
and inwards; thirdly, by the breaking up of the carotids into  three
branches, by the inclined position of the vertebrals, and by their junc-
tion into a single vessel, which takes a course obliquely upwards, and
afterwards  subdivides into smaller branches.   Such  arrangements
most effectually  break the force of the two  columns, and, as it were,
scatter it in different directions.
   A further conservative provision is found in the manner in which the
blood-vessels penetrate the brain.   The larger arterial branches run
in sulci between convolutions, or  at the base of the organ;  smaller
branches come off from them, and  ramify on the pia mater, breaking
up into extremely fine  terminal arteries, which penetrate the brain ; or
                    these latter vessels spring directly from the larger
                    branches, and enter the  cerebral substance.   As
                    a  general  rule, no vessel penetrates  the cortical
                    layer of the brain, which, in point of size, is more
                    than two removes from the capillaries; and, when-
                    ever any vessel  of greater size does pierce  the
                    cerebral substance, it is  at a situation where  the
                    fibrous matter  is external, and the part perforated
                    by foramina for  the  transmission of  the vessels.
                    Such  places are the  locus perforatus, the inter-
                    peduncular space, &c.   The accompanying figure
                    shows  the manner in which the terminal arterial
                    twigs dip vertically into the cerebral substance,
                    and break up into  a solid plexus of capillaries in
                    the stratum of vesicular matter.   The capillary
                    plexus of the fibrous or white matter has similar
                    characters, only its meshes are much  wider (fig.
                    72).   The  capillaries  of the  cerebral substance
                    are easily seen to possess an  independent dia-
                    phanous wall, with  cell-nuclei disposed  at  in-
                    tervals.  The  smaller arteries and veins can also
                    be admirably studied in the pia mater of the brain.
                      The venous blood  is collected into small veins,
                    which  are formed in  the  pia  mater  at various
                    parts of the  surface, and in  the interior of  the
                    brain.   The   superficial veins  open  by  short
                    trunks  into veins of  the dura mater,  or into  the
                    neighbouring sinuses;  the  superior longitudinal,
                    the lateral, and the  strait  sinuses  receiving  the
                    greatest number.   Those from  the  interior form
two trunks, vena magna Galeni, which pass out from the ventricles
between the layers  of the velum interpositum.    The  cerebral  veins
are devoid of valves.
   We remark here, that the venous blood of the brain  is returned to
  Two terminal arteries
leaving a branch on the
surface of a convolution
of the cerebrum, dipping
vertically inwards, and ex-
hibiting the mode of origin
and distribution of the ca-
pillaries inthe gray cortical
layer.  From an injected
specimen. Mag. 30 diame-
ters. 
THE CIRCULATION IN THE BRAIN.
267
the centre  of the circulation through the same channels as that  of
the dura mater, of the cranial bones, and of the  eyeball: the deep
jugular veins are the outlets  by which the venous  blood of the
cranium  is discharged.  An obstacle, therefore, in both or either of
these trunks must affect  the  entire venous system  of the brain, or at
least that of the corresponding hemisphere.   A  ligature tied tightly
round  the  neck impedes the circulation, and may cause  congestion
of the brain.   The  bodies of criminals who  have died by hanging
exhibit great venous congestion, both of the walls and the contents of
the cranium, in consequence of the strong compression to which the
veins have been submitted.
   We have seen, that, when  the blood of one carotid artery is cut off,
the parts usually supplied by it are apt to become exsangueous and
softened; and this is more especially the case if  the vertebral be also
impacted, or the circulation in it impeded. And it has been remarked,
that these  effects will follow the  application of a ligature to either
common carotid artery.
   Notwithstanding  these facts, a doctrine has received very general
assent, and the support of men of high  reputation, which affirms that
the absolute quantity of blood in the brain cannot  vary, because that
organ  is  incompressible, and  is enclosed in a spheroidal case of bone,
by which it is  completely exempted from the pressure of the atmo-
sphere.
   The cranium, however, although spheroidal, is not a perfectly solid
case, but is perforated by very numerous foramina, both external and
internal,  by which large venous canals  in the  diploe of the bones
communicate with the circulation of the integuments  of the  head  as
well as with that of  the brain; so  that the one cannot be materially
affected without the other suffering likewise.   And as the circulation
in the integuments is not removed  from  atmospheric pressure, neither
can that which  is so  closely connected and continuous with it, be said
to be free from the same influence.   Still it must be admitted, that the
deep position of the central  vessels, and the complicated series  of
channels through which they communicate with  the superficial ones,
protect them  in some degree  from the pressure of the air, and render
them less amenable  to its influence than the vascular system of the
surface.
   If it were essential to the integrity of the brain that the fluid  in its
blood-vessels should be  protected from  atmospheric pressure asthe
advocates of this doctrine would have us to believe), a breach in the
cranial wall would necessarily lead to the most injurious consequences;
yet, how frequently has the surgeon removed a large piece of the cra-
nium by  the trephine without  any untoward result!  We have watched
for several weeks a case in which  nearly the whole of the upper part
of the cranium had been removed by a process of necrosis,  exposing a
very large surface to the immediate pressure of the atmosphere; yet  in
this  case no  disturbance of the cerebral circulation existed.  In the
large and open  fontanelles of  infants we have a state analogous to that
which  art or disease produces in the  adult: yet the vast majority  of
infants are free  from cerebral  disease  for the whole period during 
268
INNERVATION.
 which their crania  remain incomplete; and  in infinitely the greatest
 number of cases in which children suffer under cerebral disease, the
 primary source of irritation is in  some  distant organ, and not in the
 brain itself.
    Neither can it be said that the  brain is  incompressible.   That only
 is incompressible, the particles of which will not admit of being more
 closely packed together under  the  influence of pressure.  That the
 brain is not a substance of this  kind, is proved by the fact that, while
 it is always undergoing a certain degree  of  pressure, as essential to
 the integrity of its functions,  a  slight increase of pressure is sufficient
 to produce  such an amount of physical  change in it as at once to
 interfere with  its healthy action.  Too much  blood distributed among
 its elements, and too much serum effused upon its surface, are equally
 capable of producing such an effect.
    Magendie's experiments, alluded to at p. 231-2, show that the brain
 and  spinal cord  are surrounded by fluid, the pressure of which, pro-
 bably, antagonises  that which  must be exerted through  the blood-
 vessels.   The removal of this fluid disturbs the  functions of these
 centres apparently by allowing the vessels to become too full.   The
 pressure exerted by the former we shall call the fluid-pressure  from
 without the brain ; that by the blood, the pressure from within.  As
 long as these  two  are balanced,  the  brain enjoys  a healthy state of
 function,  supposing its  texture  to be normal.   If either  prevail,
 more  or  less  of disturbance will ensue.   Their relative quantities,
 if not in just proportion,  will bear an inverse ratio to each other.  If
 there be  much  blood, the surrounding fluid will be totally, or in a
 great measure, deficient;  if the brain be anaemic, the quantity of sur-
 rounding fluid will  be large.
    The existence of these two antagonizing forces  may be takf n as a
 proof that either of them may prevail;  and therefore, from the exist-
ence of the cerebro-spinal fluid we may infer that the actual quantity
. of blood circulating in the brain  is liable  to  variation.
    This fluid is  a valuable regulator  of vascular fullness within the
 craqium, and a protector of the brain against too much pressure from
 within.  So long as it exists in  normal quantity, it resists the entrance
 of more than a certain proportion of blood into the vessels.   Under
 the influence of an unusual force  of the heart, an undue  quantity of
 blood  may be forced into the  brain; the effects of which will be, first,
 the displacement of a  part, or  of the whole surrounding fluid, and,
 secondly, the compression of the brain.
    On the other hand, the brain may receive too little blood.  In such
 a  case, if  the surrounding  fluid  do  not increase too  rapidly, the
 requisite degree of pressure will be maintained, and the healthy action
 of the brain preserved.   But, if the brain be deprived of its due pro-
 portion of blood by some sudden depression of the heart's power>  there
 is no time nor source for the  pouring out  of  new fluid, and a state of
 syncope, or of delirium, will ensue.  Such seems to be the explana-
 tion of those cases of delirium which ensue upon hemorrhages, large
 bleedings, or the sudden supervention of inflammation of the peri-
 cardium or endocardium.  In many of  these cases, however, it is
 jimportant to notice, that the blood is more or less damaged in quality, 
                   ROOTS OF THE SPINAL NERVES.               269

deficient in some of its staminal principles, or charged with some mor-
bid matter; and this vitiated state of the vital fluid has, no doubt, a
considerable share in  the production of  the morbid phenomena.
   The following inferences, which are of practical  application, will
form a suitable  conclusion to these remarks on  the circulation within
the cranium.
   1. That the  brain, although  not so amenable to the influence  of
atmospheric, pressure as more superficial parts, is sufficiently so  to
admit of variations in the quantity of its circulating fluid.
   2. That, consequently, general or local  bleeding  will  exert the
same kind of influence upon the circulation in the brain, as in other
organs, so far as relates to diminishing the quantity of blood in it.
   3. But that the  brain is liable to suffer from the loss of blood in a
different way from other viscera, inasmuch as copious bleeding  may
occasion serious disturbance in  the functions of the brain by lessen-
ing the force of the heart's action, and  thereby depriving  the brain
of that amount of pressure on its vascular surface which seems essen-
tial to  its healthy action.
   4. That the depression of the heart's force from  any other cause,
is capable  of producing similar  cerebral disturbance for  the same
reasons.

  The following works maybe consulted upon the subjects treated of in this chapter:
  Cruveilhier's Anat. Descr. t. iv.—Meckel, Anat. Gen. Descr. et Pathol, t. ii.—Reil's
Essays, translated in Mayo's Anat. and  Phys. Commentaries.—The article Nervous
Centres in the Cyclopaedia of Anatomy.—Mayo's Plates of the Brain.—Stilling und
Wallach, Untersuchungen iiber die Textur des Riickenmarks.  Leipz. 1842.—Still-
ing, liber die Textur und Function der Medulla oblongata.  Erlang. 1843.—Foville,
Anat. du Syst. Nerveux.  Par. 1844.—Leuret, Anat. Comparee du Syst. Nerveux.
Par. 1839.
  The subject of the  circulation in the  brain has been treated with great acuteness
and learning by Dr. George Burrows, in the Lumleian Lectures for 1843, Lond. Med.
Gazette, vol. xxxii.
                          CHAPTER  XI.

OF THE SPINAL NERVES.—OF  THE  ENCEPHALIC NERVES.—METHOD OF
   DETERMINING  THE FUNCTIONS OF NERVES.--OF THE FUNCTIONS OF
   THE SPINAL CORD AND ENCEPHALON.

   Before we can satisfactorily investigate the functions of the cere-
bro-spinal centre, or of its various segments, it will be necessary to
give some account of the nerves which are connected  with them.
   These  nerves  are described in two classes, the spinal and the ence-
phalic.   The former class  consists of  all those which arise from  the
spinal cord,  and emerge from the  spinal canal through orifices in its
wall.  The  latter consists of those  which  are  connected with  the
encephalon.
   Of the spinal nerves.—There is a pair of  spinal nerves for each 
270                       INNERVATION.
pair of intervertebral foramina on the same  level, and for those be-
tween the atlas and occiput.  We can thus enumerate in all thirty-one
pair of nerves having their origin  from the spinal cord, exclusive  of
the spinal accessory nerve, which is connected with the upper part of
the cervical region.
  The spinal nerves have the  following  very constant characters.
Each has its  origin by two roots, of which the  anterior is distinctly
inferior in size to the posterior (fig. 61, p, a, p. 205).   The ligamen-
tum denticulatum is placed  between these roots.   Each root passes
out by a  distinct opening in the dura mater.   Immediately after its
emergence a ganglion is formed on  the posterior  root, and the  ante-
rior root  lies  imbedded  in the anterior  surface  of  the ganglion, and
inclosed  in the same sheath, but without mingling its fibres with  those
of the  ganglion.   Beyond it, the nervous  fibres of both roots inter-
mingle, and a compound spinal nerve results.  The  trunk thus formed
passes  immediately through the intervertebral canal, and divided into
an anterior and  posterior branch (fig. 61, a',p').   The  former  is in
general  considerably the larger.  The latter passes backwards, and
sinks in among the muscles of the posterior regions  of the trunk.   The
anterior  branches in the cervical, lumbar, and sacral regions  form
large and intricate plexuses, (cervical,  axillary, lumbar, and sacral,)
from which nerves are furnished to  the extremities and  the anterior
part of the trunk.
  The first spinal nerve, called by Winslow the suboccipital, offers an
exception to this arrangement.   Generally it arises by two  roots, of
which, however, the anterior  is the  larger.   Sometimes it has  only
one root, corresponding to the anterior.
  The spinal nerves are  arranged  naturally in  classes, according to
the regions of the spine in which they  take their rise.  We number
eight in  the cervical region, the suboccipital included; twelve in the
dorsal  region; five in the lumbar,  and six in the sacral regions.   All
the nerves after the second pass obliquely outwards and downwards,
from their emergence from the spinal cord to  their exit from the verte-
bral canal; and this obliquity gradually increases from the higher to
the lower nerves, so that the inferior ones are  nearly perpendicular,
and, as their intraspinal course is of some length,  they are collected
into a leash,  which constitutes the cauda equina.
  All  the spinal nerves  arise from  the cord by separate fasciculi of
filaments, which, as they approach the  dura  mater, converge to each
other, and are united together to constitute the anterior or the posterior
roots.  The  posterior roots arise at a pretty uniform distance from the
posterior median fissure in all regions of  the cord, indicating but a
very trifling change in the thickness of the posterior columns through-
out their entire course.   Not  so the anterior ones : they are farthest
from the anterior median fissure in  the neck, but  very near it in the
dorsal  region ; this difference being due to the variation in the thick-
ness of  the  antero-lateral columns in the  different  regions.   The
ganglia on the  posterior roots are always proportionate in size to the
roots themselves.
  In tracing  the mode of connection of the roots of the spinal nerves 
ENCEPHALIC NERVES.
271
with the cord, great care is required, from the sudden change of con-
sistence which their fascicles experience on penetrating the substance
of the cord.  They lose the sheath of pia mater which gave firmness
to that part which is external to the cord, and soon break up into their
component fibrillae.  For this reason, the  specimen employed for the
dissection should be quite recent, and  slightly hardened by previous
immersion in spirit.
  The anterior roots penetrate the  lateral part of the  antero-lateral
columns.   Their fibres soon radiate, some passing  upwards and in-
wards, others horizontally inwards towards the centre of the cord,
mingling, no doubt, with the elements of the  vesicular matter com-
posing the anterior horn.   It is a matter of uncertainty whether the
fibres which take an upward course pass into the gray  matter, or simply
merge into the longitudinal fibres of the cord and pass upwards to the
brain.   Mr. Grainger's researches lead him to suppose that each root
consists of a  double set of fibres,—one which penetrates,  and has its
origin  from, the gray matter,  and the other which is continuous with
the longitudinal fibres.  This  view is considered to derive proba-
bility from the hypothesis which  ascribes the voluntary and involun-
tary actions of the cord to two distinct series of fibres,  of which one
is under cerebral influence, and the  other merely excito-motory, and
it might be acknowledged to do so,  if the necessity  of distinct fibres
for the two kinds of action were first  proved.   It is possible, how-
ever, that all the fibres penetrate  and  arise  from  the gray matter.
But we have seen nothing to justify  Stilling and Wallach's assertion,
that the anterior and posterior roots coalesce in the gray matter, form-
ing loops, the convexities of which  are directed to the  centre of the
cord ;  and we have already stated our reasons (p. 236) for doubting
the fibrous nature of the lines which  these writers represent as radiat-
ing between  the gray matter and the surface of the cord.
  The  posterior  roots  adhere  to the  posterior part of the antero-
lateral column, and are doubtless closely connected with the posterior
horns of gray matter.   In separating  the columns of the cord along the
line of sequence of the  fascicles of the posterior roots, we have always
found  these  roots to  remain with the antero-lateral columns, and to
have  little or no  connection with  the  posterior ones.   We would
therefore  refer the origin of these  nerves to the posterior horns of gray
matter, and to the posterior part of the antero-lateral columns.
   Of the encephalic nerves.—The arrangement of these nerves, ori-
ginally proposed by Willis, although  open to many objections, has
nevertheless been  so  long adopted  in this country  and on the Con-
tinent, and is so  constantly  used by scientific as well as  practical
writers, that to abandon it  would be productive of great  inconveni-
ence, and would be of no advantage, unless some other arrangement
of unexceptionable kind could be substituted for it.  In the absence of
any such  new mode of arrangement, we propose to  adhere to that of
Willis; at the same time remarking, that much of the imperfection of
it is obviated by naming each  pair of nerves from  some prominent
feature either of its function or its anatomical connections.
  Twelve pairs of nerves are found connected with the base of the 
272
INNERVATION.
encephalon.  Five pairs  have been so classed by Willis as to form
two in his arrangement;  three pairs being allotted to his eighth pair
of nerves, and  two to his seventh.  Willis' arrangement, therefore,
comprises the following  nine pairs of nerves, which  he enumerates
in passing from the anterior to the posterior part of the base ; the first
pair, or olfactory nerves; the second pair, or optic; the third pair,
motores oculorum; the fourth  pair, pathetici; the fifth pair; the sixth
pair, abducentes oculum; the seventh pair, including the portio mollis
or auditory nerve,  and the portio dura or facial nerve ;  the eighth pair,
including the glosso-pharyngeal, the pneumo-gastric,  and the spinal
accessory; the ninth pair, or hypoglossal.  Willis included among his
encephalic nerves the first cervical nerve or sub-occipital, which he
therefore numbered as the tenth pair.
  As the cranium  may be shown to be composed of the elements of
three vertebrae, it has been attempted to prove that among these nerves
some may be classed with the vertebral or spinal  nerves.  The fifth
is obviously of this kind, from its anatomical characters, namely, two
roots ; one small, ganglionless, the  other large, ganglionic ;  and with
the former, the analogue of the anterior spinal root, the third, fourth,
and  sixth nerves may be  conjoined from their similarity in structure
and  distribution.   Thus  one cranio-vertebral  nerve  is formed, the
anterior or motor root of which consists of the smaller portion of the
fifth, the third, fourth, and sixth nerves, and the posterior or sensitive
root of the larger portion of the fifth.  A second cranio-vertebral nerve
consists of the  eighth pair, to which might be added  the facial, con-
tributing to its motor portion.   A third is formed by the hypoglossal,*
but the analogy, in the latter  case,  is certainly far from obvious.
   How to determine the function of a nerve ?—It has been stated in a
former chapter  that nerves  evince  special  properties, depending on
the connections which they form at the periphery, or  at the  centre;
that they may be divided into motor, sensitive, and, according to one
view, excito-motor, according to the manner in which  they respond
to particular stimuli;  and that fibres possessing each  of these  endow-
ments may be bound together in a common sheath as one nerve.  To
determine with precision  the office  which each nerve performs  is a
problem of great importance,  not only from its bearing upon the phy-
siology of the nervous centres, but from its great practical value in
the diagnosis and treatment of disease.—(Introd., p. 47.)
   The following are the  means on  which we should rely, in order to
determine the function of a nerve.
   First, its anatomy in man.—The origin by a double root denotes a
double  function.   Its  peripheral distribution, however, gives  more
valuable assistance.   If  distributed to muscles only, it clearly must
be motor;  it to sentient surfaces only, sensitive and perhaps excitor;
if to both, motor,  and sentient, or excito-motor.
   Secondly, its anatomy in  animals.—The comparison of the origin
and distribution in the lower  animals with those in man often throws
light on the function,  by  confirming the  result of anatomical  investi-
* Muller's Physiology by Baly, vol. i. p. 841. 
            FUNCTIONS OF NERVES, HOW DETERMINED.         273

gation in the human subject, or by displaying either a peculiar deve-
lopment of the nerve, in reference to some special function proper to
particular animals; or,  on the other hand, the  non-development of a
nerve, or of a part of  one, where some function may be  deficient.
The enormous development of a branch of the fifth nerve in animals
with proboscides, or highly tactile snouts,—of a branch of the facial,
where such an organ is very movable,—the small size of  the latter
nerve where  the  muscles of the face  are few, are instances quite in
point.
   Thirdly, experiment on animals just  dead, or on those living.—The
irritation  of a motor nerve in an animal recently dead causes contrac-
tion of the muscles to which it is distributed.  The section of one in
a  living animal paralyses its muscles ;  but irritation of  the  portion
below the section causes contraction of those muscles which that seg-
ment of the nerve supplies.  The simplest way of applying a stimulus
for experimental purposes is by passing a galvanic current from a small
battery.   If the  current be  directed through a nerve so  that it shall
pass  along the smallest portion of it, by  placing one pole on one side
of it, and the other on the opposite, but  a little lower down or higher
up, we may gain  a strong indication of the motor  power of the nerve,
if contractions are thereby excited.  This indication becomes certain
if the same effect be produced by galvanizing the nerve  in this way,
after it has been separated from all connection with the spinal cord or
brain.   Such an experiment on  a sensitive nerve would produce no
motor effect.   Matteucci has shown that to  produce the  motor effect
in a motor  nerve, the current  must pass along some portion of the
nerve-fibre, however small;  and that  a  current directed  precisely at
right angles to the fibres will not excite  nervous powrer.*
   MM. Longet and Matteucci affirm that a motor nerve  may be dis-
tinguished from a compound one by the different  effect of opening or
closing an electric current on  each under certain circumstances.  It
had already been ascertained by Lehot,  Bellingeri, Nobili, and Mari-
anini, that compound nerves, the sciatic, for instance, are at first ex-
cited, equally on closing and on opening the electric  circuit, whether
the current be direct {i. e. from the brain  or cord to  the nerves), or
inverse (from the nerves to the brain  or cord); but after a time they
are excitable, as shown by the contraction of the muscles  below the
point of'the  nerve stimulated, only on  closing the direct current or
opening the inverse.  With a  purely  motor  nerve, however, such as
the anterior root of a spinal  nerve, a  different result is obtained ; in-
asmuch as the contractions of the muscles can  only be excited on
opening the direct current or closing the inverse, f
   Sometimes we  find that, if the trunk of a nerve be divided  at some
distance  from its  origin, irritation of the central segment will excite
contractions, whilst that of the peripheral one will fail  to do so.  Such
a  nerve has been called an excitor ; for it causes muscular movement,

   * See an account of Matteucci's observations on the different effects of electricity
on nerves, in the appendix to this chapter.
   -j- Matteucci et Longet, sur la relation qui existe entre le sens du courant electrique
et  les contractions musculaires dues a ce courant.  Paris. 1844. 
274                       INNERVATION.
not by its direct influence upon muscles, but by exciting the centre,
which in its turn stimulates motor nerves arising from it.   We judge
a nerve to be sensitive, if, when irritated in man or the lower animals
during life, a peculiar sensation or pain be excited ; or if section of it
destroys the sensibility of the parts to which it is distributed.
  Fourthly. Clinical observation furnishes most valuable opportuni-
ties of testing the true function of nerves.  We observe a particular
form of paralysis, and we  inquire what  nerve  is diseased;  we find
pain felt in particular regions, and we ascertain that this is  in conse-
quence of a morbid state of particular nerves ; certain functions are
impaired or suspended, if certain nerves  be affected  with disease.  A
woman, lately in King's College Hospital, had a singular  train of
symptoms, which were at  first referred to hysteria.   However, in  a
little time they became so  confirmed, that no doubt could be enter-
tained of organic lesion.   There were  ptosis of the upper  lids,—
paralysis of the  muscles of the  eyeball supplied by the third nerve,
—paralysis of the pharynx, so that the power of deglutition was de-
stroyed,—paralysis  of the trapezii muscles, and  of those on the back
of the  neck,—great feebleness of voice.   She died like one asphyx-
iated.   After  death, the following  nerves were found involved in  a
thickened neurilemma, with altered nerve-tubes,—the third pair, the
fourth  pair on the left  side, the glossopharyngeal, the  vagus, the
spinal accessory; each of  which contributed more or less to supply
with nerves the  parts paralyzed.
  Functions of the  roots of spinal nerves.—The application of ana-
tomical investigation, and  of  experiment, to determine the functions
of the anterior and  posterior roots of  spinal nerves respectively, was
the first important step towards a right understanding in the physiology
of the nervous system.   This  was undoubtedly taken by Sir C. Bell;
and, although there were  other  labourers in the same field not un-
worthy claimants of some share in the merit of  this important inves-
tigation, it cannot be denied that the endowments of the roots  were
discovered by Bell.
  The original experiments of Bell, in which he was assisted by the
late Mr. John Shaw, consisted in laying open the spinal canal in rab-
bits, and irritating or dividing the roots of the spinal nerves.  Bell
distinctly affirmed that irritation of the anterior roots caused muscular
movement, and  that  the posterior roots  might be  irritated without
giving rise to any muscular action.  Destruction of the posterior roots
did not impair the voluntary power over the muscles.  Hence it was
inferred that the anterior roots were motor, and the posterior roots not
motor; but, from the violence of the operation, and the pain produced
in performing it, the experiments having been tried on rabbits, it was
impossible to determine what  degree  of  sensibility remained in parts
supplied from  the divided roots.
  Numerous subsequent experimenters arrived  at similar  results to
those of Bell; but  no one  obtained such satisfactory conclusions as
Muller, who adopted the expedient of experimenting on frogs instead
of mammalia, with  which latter the experiments involved the neces-
sity of a tedious and painful  operation,  and much bloodshed. In 
FUNCTIONS OF THE SPINAL CORD.
275
frogs, on the contrary, from the great width of the lower part of the
spinal canal, the roots of the nerves can be exposed with facility, and
their excitability lasts sufficiently long to yield every result.  These
experiments we have repeated frequently, with results precisely similar
to those which Muller obtained.
   In the experiments on frogs, irritation, mechanical or galvanic, of
the anterior root always provokes muscular contraction.   No  such
effect follows irritation of the posterior root.   Section of the anterior
root causes paralysis of motion ;  that  of the posterior, paralysis of
sensation.   This latter  effect is evinced by the  utter insensibility to
pain shown on pinching a toe,  whilst in the limb in which the poste-
rior root is entire such an irritation is evidently acutely felt.  If the
anterior roots of the nerves to the lower extremity be cut on one  side,
and the posterior roots on the other, voluntary power without sensation
will remain in the latter, and sensation without voluntary power in the
former.
   Valentin, Seubert, Panizza,  and  Longet have performed similar
experiments upon mammiferous animals with^precisely the same ef-
fects.
   The conclusion to be derived from these experiments is as follows:
that the anterior root of each spinal nerve is motor, and the posterior
sensitive.
   Comparative anatomy confirms  this conclusion, by showing that  a
similar arrangement of the spinal roots prevails among all classes of
vertebrate animals, and that if, in any particular cjass of animals, either
the motor or sensitive power predominate, there is in correspondence
with it a marked development of the anterior or posterior roots; and
the frequent occurrence of paralysis  of sensation and  motion, as  a
consequence of disease within the spinal canal, also tends to the same
inference.
   Magendie affirms that the anterior root is slightly sensitive, owing,
as Kronenberg has shown, to an anastomotic filament which it derives
from the posterior root.
   Functions of the spinal cord.—Since  nerves of  sensation and mo-
tion have their origin from  the cord, it cannot be  doubted that this
organ  is the medium for the reception and propagation, first, of sensi-
tive impressions made upon those surfaces on  which  its nerves are
distributed, and secondly, of those impulses which are the ordinary
excitants of muscular movements.
   Experiment and clinical observation, however, show  that sensa-
tion and voluntary motion are  not connected with, or dependent on,
the spinal  cord alone.   If the connections of this organ with the en-
cephalon be perfect, and uninterrupted  by any solution  of continuity,
morbid deposit in it, or morbid growth causing compression, then the
essential condition for the full play of the  nervous force,  whether for
sensation or voluntary motion, is fulfilled.  But if the cord be severed
just below the plane of the  occipital foramen, as when an animal  is
pithed, all voluntary power over the parts supplied by spinal nerves
ceases, and all sensation in those  parts disappears at the same time. 
276
INNERVATION.
Here the cord itself is uninjured; but  its continuity with the ence-
phalon is destroyed.
  In cases  of injury to  the vertebral column, causing fracture  and
displacement of  the vertebrae, and destruction of the cord, the parts
supplied from that portion of the  cord which  is below  the  seat of
injury are paralyzed as regards voluntary motion and sensation.  The
higher the  seat of injury, the more  extensive will be the paralysis.
A man who has received extensive injury of the  spinal cord in  the
neck, is like a living head and a dead trunk,—dead to its own sensa-
tions, and to all  voluntary control over its movements.
  Similar remarks may be made respecting those cases in which dis-
ease, or compression  of the cord by some intra-spinal  growth,  has
interrupted  its continuity in some region.  The extent of the para-
lyzed parts always affords  a correct indication of the  seat of  the
solution of continuity.
  If the spinal cord be divided partially in  the  transverse direction,
there will be paralysis of parts  on the  same side with the injury in-
flicted.  A longitudinal  section of the  cord along the median line
does not cause any paralysis; a temporary disturbance of its functions,
however, ensues, which  soon subsides.
  So long, then, as the spinal cord and  encephalon are  continuous,
and in their normal state, the former organ must be regarded  as spe-
cially adapted to receive  and propagate sensitive impressions from the
trunk and extremities, or to  convey the stimulus of volition to their
muscular nerves.
  There is nothing, however, in these facts to denote that the spinal
cord does not share, in some degree in  the function of sensation and
voluntary motion.  All that we are justified in inferring from them is,
that the union of the encephalon with the spinal  cord is necessary for
voluntary motion and for sensation.
  Indeed, the recent discovery of the amphioxus lanceolatus, a small
fish found in the Archipelago, makes it  probable that voluntary mo-
tion and sensation  may exist where  there is  a well-developed spinal
cord, the anterior extremity  of which tapers to a fine point, and is far
from exhibiting the ordinary characteristics even  of a brain so inferior
in organization as that of fishes.*
  In most instances where the spinal cord has been divided, whether
by design or accident, it has been found that, although the will can-
not move the paralyzed parts, movements do occur in them of which
the individual is unconscious, and which he  is wholly unable to pre-
vent.  These take place sometimes as if spontaneously, at  other times
as the effect of the application of a stimulus to some surface supplied
by spinal nerves.  The apparently spontaneous movements frequently
resemble voluntary actions so closely, that it is almost impossible to
distinguish them.
  These phenomena occur in all classes of animals, warm-blooded as
well as  cold-blooded.  In the latter, however,  they are  much more
marked ; the nervous force endures much longer in these animals than

   * Goodsir, in Ed. Philos. Transactions, and Cyclop, of Anat., vol. ill., p. 615. 
FUNCTIONS OF THE CORD.
277
in the higher classes of mammalia and birds, just as we have already
seen that the muscular power  does, although we have  no reason to
suppose that either force is more energetic, because it is more enduring.
On this account cold-blooded animals must be selected for exhibiting
the phenomena; and accordingly hosts of frogs, salamanders, snakes,
turtles, and fishes have fallen a prey to  the experimental researches
of the numerous physiologists who have devoted  themselves to these
investigations.
   The following experiments serve to illustrate these actions:
   If a frog be pithed by dividing the spinal cord between the occi-
pital hole and the first vertebrae, an universal convulsion takes place
while the knife is passing through the  nervous  centre.   This, how-
ever, quickly subsides;  and, if the animal be placed on  a table, he
will assume his ordinary position of rest.  In some exceptional cases,
however, frequent combined movements of the lower extremities will
take place for a longer or shorter time after the operation.  W~hen all
such disturbance has ceased, the animal remains perfectly quiet,  and
as if in repose, nor does there  appear  to be the slightest expression
of pain or suffering.  He is quite unable to move by any voluntary
effort.  However one may try to frighten him, he remains in the same
place and posture.  If now a  toe be  pinched, instantly the  limb is
drawn up, or he seems to push  away the  irritating agent, and  then
draws up the leg  again  into its old position.  .Sometimes a stimulus
of this kind causes both limbs to be violently moved backwards.   A
similar movement follows stimulation  of  the anus.   If  the skin be
pinched  at  any part, some neighbouring muscle or muscles will be
thrown into action.   Irritation of the anterior extremities will occa-
sion movements in them ;  but it  is worthy of note, that these move-
ments are seldom so energetic as those  of the lower extremities.
   It is not out of place  to state  here, that phenomena of this kind
are not confined to the trunk and extremities which are supplied  by
spinal  nerves only.  The head and face with which the  encephalon
remains in connection exhibit similar actions.  The slightest touch to
the margin of either eyelid, or to the surface of the conjunctiva, causes
instantaneous winking; the attempt to depress the lower jaw, for the
purpose of opening the mouth, is resisted; and the act  of deglutition
is provoked by applying a mechanical stimulus  to the back of the
throat.
   The stimuli which excite these  movements are those ordinary ones
which are capable of calling nervous power into play, such as mecha-
nical irritation, heat, cold, galvanism, chemical irritants.
   There  can be no grounds for supposing  that the will has anything
to do with these  movements.   An animal pithed, which is to all in-
tents and purposes in the same condition as  one  decapitated, shows
no sign of voluntary action, excepting  perhaps for a short time after
the operation, whilst the irritation caused by the division  of the cord
remains.   He maintains one and the same position, without evincing
any sign  of  sense or motion, unless  a  stimulus  be applied to some
part of the surface; and, after the movement which such a stimulus
excited has ceased, he resumes the same state of inactivity. 
278
INNERVATION.
  Comparing  this state of a pithed  or  decapitated  animal with  the
phenomena which we  know  to  take place in the  human subject in
effect of particular forms of accident or disease, it  is impossible to
regard these actions in any other light than as involuntary ones.   To
refer once more to such  a case as that cited in  a  former paragraph,
when,  from the destruction of the cervical part of the cord, the trunk
appears as if dead, while the head lives, we find in  many instances,
if the stunning effect have not been too  great, that similar motions to
those described in  the frog may be  produced by the application of
mechanical or other stimuli to the surface.   Tickling the soles of the
feet causes movements of the lower extremities : the introduction of
a catheter into the  urethra, which is not felt by the patient, excites
the penis to erection.   Over these acts not only have the patients no
control, but they are absolutely unconscious of their occurrence, as
well as of the  application of the stimuli by which they were provoked.
It is plain, then, that these  movements take place without the con-
currence or even the cognizance of the mind, whether as the recipient
of stimuli, or as  the source of voluntary  impulses.
  In hemiplegia, the result of diseased brain, when the paralysis is
complete, the influence of the will over the paralyzed side is altogether
cut off.   In such  cases,  movements  may  be excited in the palsied
leg—very rarely in the  arm—by stimuli  applied to  the  sole of  the
foot, or elsewhere; and we  often astonish the patient himself, who
expresses his  utter inability, by any effort  of his will, to move  his
leg, by exciting  active movement of it  on touching the  sole of  the
foot very lightly with a feather.  It  is  proper to add, that there is
much variety as  regards the extent to which  these actions take place
in hemiplegic  cases, owing to causes which are not yet fully under-
stood.   Still, they do occur in a large proportion of instances, and in
the  most marked way.   In most of  the  cases of hemiplegia the sur-
face retains its sensibility; but in most of those of paraplegia sensi-
bility is much  diminished or completely destroyed.
  In the anencephalic  foetus, in which all  the encephalon but part of
the  medulla oblongata is wanting by congenital defect, actions take
place in obedience to stimuli propagated to the  cord from some sur-
face, or applied  directly to it; but no movements are seen which can
be supposed to originate in an effort of the will, nor is there any proof
of the existence of sensibility.
  Other facts  may be adduced in evidence of the involuntary nature
of these movements.
  It is remarkable that actions of this kind will continue to be mani-
fested after decapitation, not only in the trunk, but also  in segments
of it with which a portion of the spinal cord  remains in connection.
If the body of a snake or an eel be divided into several segments,
each one will  exhibit movements for some time, upon the application
of a stimulus.   The same thing may be observed  in frogs,  salaman-
ders, turtles, and other cold-blooded creatures.  In  birds and mam-
malia, however, they are less conspicuous, because in them the nervous
power is so soon extinct.
  These  facts  suggest an obvious comparison between the spinal cord 
FUNCTIONS OF THE CORD.
279
of vertebrate animals and the abdominal ganglionic chain of articulate
invertebrata.   In the latter, each segment of  the body has its proper
ganglionic centres, and is, therefore, to a certain extent, independent
of the rest.  Every schoolboy has witnessed the  writhings  of  an
earthworm, which his mischievous propensity has prompted him to
divide into several pieces.  Movements will  continue in each piece
so long as the irritation produced by the subdivision  remains ; and,
after that has ceased, movements may be excited in any segment by
stimulating its surface.   These movements seem precisely analogous
to those which may be excited in the subdivisions of the  trunk of a
vertebrate  animal.   The spinal cord, then, may be viewed as  one
continuous centre, made up of a number of segments  fused  together
at their extremities.  In  the articulate ganglionic chain the centres of
the segments remain distinct, although connected by fibres which pass
from one to the other.
  When the spinal  cord is divided about its middle, a remarkable
difference may be noticed in the effects  of irritation on the  anterior
and the posterior segment, as shown in some of Flourens' experiments.
When the  anterior segment (that which still  retains  its connection
with the brain) is irritated, not only are  movements of the  anterior
extremities  produced, but  the animal evinces unequivocal  signs of
pain ;  but, when the posterior segment is irritated, the animal  seems
not only insensible to pain, but unconscious even of the movements
that have been excited in the posterior extremities.
  Nothing can be more conclusive than such an experiment, in illus-
tration of the fact that connection with the encephalon  is necessary to
sensation; and that  movements, not only without volition, but even
without consciousness, may be excited by stimulating the posterior
segments.
  Direct irritation of the spinal cord is capable of exciting these move-
ments  as much as when the stimulus is applied to the skin.
   When the spinal  cord is removed, all these motions  cease ;  no
movement of any kind, voluntary or involuntary, can then be  excited,
except by directly stimulating  the  muscles, or the  motor  nerves  by
which the  muscles are  supplied.   Division of all  the  roots of the
nerves at their emergence from the cord produces precisely the same
effect.  Under such circumstances no motion can be excited  by stim-
ulation of the surface,  nor by stimulation of the  cord itself;  and
this fact may be regarded as an unequivocal proof that the nerves, in
ordinary actions, are propagators of the change  produced by  im-
pressions to or  from the centres;  and that in the physical  nervous
actions the stimulus acts  not from one nerve to another directly, but
through the afferent nerve upon the centre, by which the motor nerve
is excited.
   From these details we may draw the  following  conclusions:—1,
that the spinal cord, (we use the  term in  its simple anatomical  sense,
—the  intra-spinal nervous mass,) in union with the brain, is the instru-
ment of sensation and voluntary motion to the trunk and extremities;
2, that the spinal cord may be the medium for the excitation of move-
ments, independently of volition or sensation, either by direct irritation 
280
INNERVATION.
of it's substance, or by the influence of a stimulus conveyed to it from
some surface of the trunk or extremities by its nerves distributed upon
that surface.
   This latter office of the  cord,  although recognized  by  Whytt,
Prochaska, Blane, and  Flourens,  had not  attracted all the  notice
which its great importance merits, until  the researches of Dr. Mar-
shall Hall and Professor Muller drew attention to them ; and to these
physiologists, but especially to the former, much praise  is due for the
zealous and efficient manner in which they have investigated the sub-
Ject
   The class  of actions which take place in virtue of  this power of
the cord are  so independent  of all  mental influence, and so purely
physical in their cause, as  well as in their nature, being provoked by
a physical  stimulus, and consisting essentially in a physical  change
in the centre,  as  well as  in its afferent  and  efferent nerves,  that
they may be  distinguished from those  of volition  and sensation, in
which the  mind has a necessary share, by being designated " phy-
sical."   It has been already stated that Dr. Marshall  Hall uses the
not unobjectionable  title of " excito-motory" in reference to these
actions.
   In genera], when a  stimulus is applied to the  spinal cord, the ac-
tions which are excited by it are confined to a part which derives its
nerves from that segment of the cord on which the stimulus falls.  In
some instances, however, parts supplied from other and even distant
segments are thrown  into  action.   Thus irritation  of one  leg will
cause movements of one or both of the upper extremities; the intro-
duction of a  catheter into  the urethra will sometime cause  forcible
contractions of the muscles of all the limbs.  No doubt these effects
are due to the extension of the irritation in the cord beyond the point
first stimulated ; and they may be regarded as proofs that that peculiar
state  of physical change which nervous irritation can excite in a
centre may be  propagated  in  the spinal cord, upwards, downwards,
or sideways from the seat of the primary stimulation.
   Disease  affords some striking instances in confirmation of this re-
mark.
   A wound in  the  sole of the foot, or the ball  of the  thumb, or in
some other situation favourable to the  maintenance  of prolonged
irritation, is capable of exciting a particular region of the cord, from
which the state of excitement spreads so as to  involve not only the
whole  cord, but part of the medulla oblongata also ; and in this state
a large proportion  of the motor nerves participate,  so as to induce
tonic  contraction of the  muscles they supply.   This is  the rationale
of the  development of that fearful malady called tetanus.  It consists
not in an inflammatory affection of the cord, or of its membranes, nor
in congestion of them, but simply  in  a state of prolonged physical
excitement, the natural polar force of the centre being greatly exalted,
and kept so by the constant irritation propagated to it by the  nerves
of the wounded part.
   In cases of paraplegia from disease  of  the spinal cord, even when
the paralysis  of sensation and  of  motion  is complete, patients are 
POLAR STATE OF THE CORD.
281
tormented  with  involuntary movements of the lower  extremities  at
night, which not only prevent sleep, but occasion considerable pain
and distress.  Thus, parts which in their quiescent state are insensible,
become painful in the  state of excitement.  The cause of this is no
doubt to be found in a periodical exacerbation of the primary disease
of the cord, and  the  extension of the  state of excitement from the
seat of  the lesion to  the whole cord; to that portion which is in con-
nection with the brain, as well as to that which is below the lesion.
   The rigid and contracted state of the muscles  of paralyzed limbs,
which frequently accompanies red softening of the brain, arises from
the propagation  of the excited state of the diseased part of the brain
to that portion of the spinal cord which is connected with it, and from
which the nerves of the paralyzed parts arise.  These nerves likewise
participate in the irritation of the cord, and thus  keep  the muscles in
a continual state of active contraction.   There is  no organic lesion of
the cord in these cases;  its state of excitement is dependent  on the
cerebral irritation.
   The  convulsions  of epilepsy  arise from  a  similar  cause, namely,
irritation of the brain, involving the whole or a part of the spinal cord,
and the nerves arising from it.  In many instances the convulsions are
limited to one-half of the body : in such cases there is generally lesion
of the brain  on  one side, and the cerebral excitement is  propagated
only to one-half (the opposite) of the cord.
   Some substances  exert a peculiar influence  upon the spinal cord,
and throw it into a state of considerable polar excitement.  Strychnine
is the most energetic substance of this  class.  If a certain quantity of
this drug  be injected into the blood,  or  taken  into the  stomach  of
an  animal, a state of general tetanus  will  quickly ensue, sensibility
remaining  unimpaired.  The  slightest touch  upon any part  of the
surface, even a breath of wind  blown upon it, will cause a general
or  partial  convulsive  movement.  The whole extent of the cord is
thrown into  this polar state, and even the medulla  oblongata is in-
volved in it; whence the closed jaws, the spasmodic state of the facial
muscles, the difficult deglutition.  In this remarkable state of excite-
ment it is curious to observe that the  spinal cord is perfectly  natural
in point of structure, as far as our means of observation enable us to
judge.  We have  examined  some  spinal cords, of animals which
have died  exhausted by the effects of the strychnine, but have  always
found the nerve-tubes and other elements of the cord exhibiting their
natural appearance.
   Opium is capable of creating a similar state of  polarity in the cord.
This is most conspicuous in cold-blooded  animals; but  no doubt it
produces, in a much less degree, a similar effect in the warm-blooded
classes.  Hence there is an objection to  the use of opium in large
doses in cases of tetanus ; and experience has shown its  utter inefficacy
when administered to a large amount.
   This polar state  of the cord, at least of a part of it, is sometimes
developed  naturally.  The most remarkable example of this  with
which we are acquainted is in the case of the male frog, in the spring
of  the year,  the  season of copulation;  the thumb on  each hand be-
        19 
282
INNERVATION.
coming at this  season considerably enlarged, as is well  known to
naturalists.  This enlargement is caused principally by a considerable
development of the papillary structure  of the  skin which covers it,
so that large papillae are formed all over  it.  A male frog at this season
has an  irresistible propensity to cling to any object by seizing it be-
tween his anterior extremities.   It is in this way he seizes upon  and
clings to the female, fixing his thumbs to each  side of her abdomen,
and remaining there for weeks, until the  ova have been  completely
expelled.   An effort of the will alone could not keep up such a grasp
uninterruptedly for so long a time ; yet  so firm  is the hold that it  can
with difficulty be relaxed.   Whatever  is  brought in  the way of  the
thumbs will be  caught by the  forcible contraction of the  anterior
limbs;  and hence we  often  find frogs  clinging blindly to  a piece of
wood, or a dead fish, or some other substance which they may chance
to meet with.  If the finger be placed between the anterior extremi-
ties, they will grasp it firmly; nor will they relax their grasp until they
are separated by force.   If the animal be decapitated whilst the finger
is within grasp of  its anterior extremities, they still continue to hold
on firmly.  The posterior half of the body may be cut away, and  yet
the anterior extremities will still cling to the finger; but immediately
that segment of  the  cord from which the  anterior extremities derive
their nerves has  been removed all their motion  ceases.   This curious
instinct, then,  of the male  frog, which naturalists have  long noticed,
is evidently connected  with an  exalted polarity of the cord, which is
most manifest in the anterior extremities by reason of the enlargement
of the thumb.  It only  exists during the period of sexual excitement,
for at other periods the excitability of the  anterior extremities is con-
siderably less than that of the posterior.
   Nothing seems to control this polar state of the cord so effectually
as cold.   Ice  applied  along  the spine,  or the  cold douche, may be
frequently employed with great advantage in cases of muscular dis-
turbance dependent on this polar state of the cord.  We know of no
substance which, when introduced into the  blood, effectually calms
this excited state.   Conium and belladonna have been, in our hands,
very useful in relieving the cramps and  startings in paraplegic cases.
We have seen no  marked benefit from hydrocyanic  acid, although
we have administered  it freely:  on the contrary, we fear that both it
and the two former substances might, if given in large doses, have
the contrary effect, and increase the polarity  of the cord.   Certain it
is, that  animals poisoned by large  doses of these drugs always  die in
a state  of general convulsion, and that  in  the  instances where they
have  acted as poisons on  the human  subject, general convulsions
have come on a longer or shorter time before death.
   Functions of the columns of the cord.—Having so  far determined
the functions of  the entire  cord, the next question which  demands
our attention  is, whether  its columns have special functions,  in  ac-
cordance with those of the separate roots of the nerves.  Could it be
proved  that the  anterior or motor roots were exclusively  connected
with the  antero-lateral columns, and that the  posterior  or sensitive
ones arose exclusively from the posterior  columns, then there would 
OFFICE OF THE COLUMNS OF THE CORD.         283
be good anatomical grounds for the doctrine so long erroneously pre-
valent, that  the functions of these  columns coincided with those of
the roots, that trfe posterior columns were sensitive and the anterior
motor: but nothing  is more certain than that both roots are connected
with the antero-lateral columns; and it  is a  matter of some  doubt
whether the posterior roots have any connection at all with the  poste-
rior columns.  Hence, all that anatomy warrants us in stating is, that
the antero-lateral columns are probably  compound in  function, both
motor and sensitive.   Respecting the office of the posterior columns
little can be said.  Are  they sensitive?  Were they so, it  might be
expected  that  they would  exhibit  an obvious enlargement  at the
situations which  correspond  to  the  origins of the largest sensitive
nerves;  but it is remarkable that the posterior columns exhibit little
variation of size throughout the  entire  length of the cord.   And it is
not likely they can  be motor, inasmuch as the apparent origin  of the
motor roots  is so  distinctly remote from them.
   Comparative anatomy  throws no light on  this question.   New and
careful researches are much needed to  determine the development
of the posterior  columns, and the exact relation which the posterior
roots bear to them in different classes of animals.
   Nor do we derive much positive knowledge from the researches of
the morbid anatomist. Cases, indeed, are on record, which show that
disease of the posterior columns does not necessarily destroy sensi-
bility; that  perfect  sensibility is  compatible with total  destruction of
the posterior columns in  some particular region, the posterior roots
remaining intact; and others have  occurred in which  sensibility has
been  impaired or destroyed, while  the posterior columns  remained
perfectly healthy.  In a remarkable case, related by Dr. Webster,
there was complete  paralysis  of motion in the  lower extremities, but
sensibility remained ;* yet there was  complete  destruction  of the
posterior columns in the lower part of the cervical region.  Similar
cases have been put on record by Mr.  Stanley and by Dr.  W.  Bu'dd.
Dr. Nasse, of Bonn, refers to several cases of the same kind, observed
by himself or others.f  We have ourselves seen two cases in  which
the prominent symptom  was  great  impairment of the  motor  power
without injury to the sensitive; yet the seat of organic lesion in both
was in the posterior columns of the cord.   Such a  case as that  of Dr.
Webster's appears to us to be conclusive, so far as the  following pro-
position extends, namely, that sensation may be enjoyed in the inferior
extremities  independently of the posterior columns ; and that, even  if
those columns be sensitive, there must  be some other channel for the
transmission of sensitive impressions besides them.
   We are not aware of  any well observed case in which the  motor
power persisted after extensive lesion  of the antero-lateral columns;
on the contrary, we believe it may be  laid down as the general rule,
that lesion of  those columns  always  impairs both the motor and the
sensitive functions  to an extent proportionate to the amount of morbid
structure.

       * Med. Chir. Trans., vol. xxvi.
       f Untersuchungen zur Physiologie und Pathologic  Bonn, 1835-36. 
284
INNERVATION.
  Pathological observations, then, appear to warrant the conclusion
that the antero-lateral columns are compound in function, both sensi-
tive  and motor,  but  they do not justify us in attributing sensitive
power to the posterior columns.
  Direct experiments on the  anterior  and posterior columns of the
cord are surrounded by difficulties, which embarrass the experimenter,
and weaken  the  force of his  inferences.   The  depth at which  the
cord is situate in  most vertebrate animals, its extreme excitability, the
intimate connection of its various  columns with each  other, so that
one can scarcely  be irritated without the participation of the others,
the proximity of  the roots of its nerves to  each  other, and the diffi-
culty of irritating any  portion of the cord itself without affecting either
the anterior or the posterior roots,  are great impediments to accurate
experiments, and sufficiently explain the discrepancies which are ap-
parent in the results of  the various experiments  which have been
published.   Moreover, the resultant phenomena, after experiments of
this  kind,  are extremely difficult  of interpretation, especially with
reference  to sensation.   "The  gradations  of sensibility," remarks
Dr. Nasse, "are  almost  imperceptible; the shades are so delicately
and so intimately blended, that every attempt to determine the line
of transition proves inadequate.  There is a great deal of truth in an
expression of Calmeil, that it  is much easier to appreciate a hemi-
paralysis of motion than a hemiparalysis of sensation.   If the anterior
fasciculi of the cord  possess  sensibility, but only in a slight degree,
the mere opening of the vertebral canal and laying bare the cord must
cause  such a degree of pain as would weaken or destroy the manifest-
ations of sensibility  in  the  anterior fasciculi.   This  has not been
sufficiently attended to by experimenters.  Again the practice of first
irritating  the posterior fasciculi, and  afterwards the anterior, must
have had considerable effect in producing the same alteration.  It is
plain that, in this way, the relations which the anterior fasciculi bear
to sensation must be greatly obscured; yet with the exception of some
few  experiments, this has  been  the order  of proceeding generally
adopted."*
   All those who have made experiments with the view of ascertaining
the functions of the columns of the cord, agree in  stating that irritation
of the anterior columns was attended with  more or less movement.
The  results  of stimulation  of the posterior columns, however, have
been differently stated by various observers: many found that it was
attended with the excitation of motion;  and others, that the least irrita-
tion of the posterior columns excited pain.  M. Longet, who is among
the latest experimenters on this subject, observes, that motions result
from irritation of the  posterior columns only when the experiment has
been made immediately  after the transverse division of the cord, and
he refers such motions to the excitability of the  cord itself.  After a
little time, however, this subsides; and then M. Longet has been able
to pass the  galvanic  current through each or both of  the posterior
columns, without exciting any motions when the lower segment of the

   * Loc. cit.; quoted from an abstract in the Brit, and For. Med. Review, vol. iv. 
OFFICE OF THE POSTERIOR COLUMNS.          285
cord was acted upon, but causing pain, as evinced by loud cries and
writhing of the body, when the upper segment was tried.  Dr. Baly's
experiments on tortoises showed that movements might be  excited
whether the  anterior  or  posterior columns were irritated,*  much
stronger motions being excited by the posterior than by the  anterior
columns.
  It is clear, then, that we must not draw any other conclusion from
experiment  than  that the  antero-lateral columns appear to be  motor
in their function.  Respecting their sensitive power we gain no inform-
ation from this source: and it must be confessed that our knowledge
is no more advanced by it as regards the posterior columns.
  We are much disposed to think that the antero-lateral columns are
the centres of  the main  actions of the cord, whether mental or physical.
Both roots of the nerves are connected with these columns, and there-
fore fibres of sensation and of motion must be found in them.  These
columns are always proportionate to the nerves which arise from them:
they enlarge when the nerves are large, and contract when the nerves
diminish in size.  The posterior columns, on  the  other hand, are of
uniform dimension throughout nearly the entire length of the cord,
although the  posterior roots  of  the nerves  exhibit considerable dif-
ference in point of size in different regions.
   We venture1 to suggest that the posterior columns may have a func-
tion different  from any hitherto  assigned to them.  They may be in
part commissural between  the various segments of the cord, and in
part subservient to the function  of the cerebellum in regulating and
co-ordinating the movements necessary for perfect locomotion.
   The  analogy of the  brain, in which the various  segments  are con-
nected  by longitudinal commissures, suggests the probable existence
of fibres similar in office for the spinal cord.  If we admit such fibres
to be necessary to  ensure harmony of action between the several seg-
ments of  the  encephalon, there  are  as good  grounds for  supposing
their existence in the cord, which in reality may be regarded as con-
sisting  of a number of ganglia, each a centre  of  innervation to its
proper  segment of  the body, and  therefore  requiring some special
connecting  fibres to  secure consentaneous action with the rest.
   The  attribute of locomotive power rests upon the connection of the
posterior columns with the cerebellum, and the probable influence of
that organ over locomotion.   If the cerebellum be the regulator of
locomotive actions, it seems reasonable to suppose  that those columns
of the cord  which  mainly pass into it, should enjoy a similar function;
that, as they are the principal medium through which the cerebellum
is brought into connection with the cord, it must be  through their
constituent fibres that the cerebellum exerts its influence on the nerves
of the lower extremities, and of other parts concerned in the locomo-
tive function.
   The  nearly uniform  size of the posterior  columns in the  different
regions of the cord has been already remarked  as unfavourable to
their being  channels of sensation.  But  this anatomical fact may be
adduced as a  good  argument in support  of the hypothesis which we
        • See his translation of Miiller's Physiology, Second Edit., p. 796. 
286
INNERVATION.
are now discussing.  It is worthy of notice that these  columns ex-
perience no marked diminution in size until the large  sacral nerves,
which furnish the principal nerves of the lower extremities, begin  to
come off.
   In  examining a transverse section  of the lumbar region of the cord,
we observe a great predominance of its central gray matter; the pos-
terior columns appear large, and the antero-lateral columns inadequate
in proportion to the  large roots of nerves which emerge from it.
Now, an analysis of the  locomotive actions renders it highly proba-
ble that they are partly of a volitional character and partly dependent
on  the inherent power  of that segment of the cord from which the
lower extremities derive  their nerves.   In  progression there are two
objects to be attained,—to support the centre of gravity of the body,
and to propel it onward ; the former object requiring, first, that the
muscles of the lower  extremities, the pillars of support to the trunk,
should be well contracted, in a  degree proportionate  to  the  weight
they have to sustain.   Those actions by which the trunk is balanced
upon  the limbs, and by which  the movements of progression arc
effected, are subsequently called  into play  through mental influence-
The contraction of  the muscles of the limbs seems well provided for
in an  arrangement for  the development of nervous power by a stimulus
propagated to the centre.   This stimulus is afforded by the  application
of the soles of the feet to the ground ; it is therefore proportionate to
the weight which presses  them downwards.   It  is well known that
physical  nervous actions are more developed in the lower  than in the
upper extremities, and the surface of the sole of the foot is well adapted
for the reception of sensitive impressions.  No object can be assigned
for this peculiarity, unless it have  reference to the locomotive actions;
and the great development of the vesicular  matter in this region be-
tokens the frequent and energetic evolution of the nervous  force.  All
the structural arrangements necessary for this purpose are found in the
antero-lateral columns.   The  posterior columns come into  play in
balancing the trunk, and in harmonizing its movements with those of
the lower extremities.
  Experiment, while  it fails to elucidate the function of the posterior
columns, exhibits  nothing in  opposition to  the views we have ex-
pressed.   It is not to be  expected that commissural and  co-ordinat-
ing fibres should react with stimuli similarly to  fibres  of voluntary
motion.
   We think that the phenomena of disease  may be referred to in
support of our view.   In many cases where  the principal symptom
has been a gradually increasing  difficulty  of  walking, the posterior
columns  have been the seat of disease.  We may notice two kinds
of paralysis of motion, distinguished respectively by impairment or
loss of voluntary motion, and of  the power of co-ordinating  move-
ments.  In the latter form, while  the voluntary powers are consider-
able,  the patient walks with  great  difficulty, and a gait so tottering
that his centre of gravity is easily displaced.   These cases are gene-
rally of the  most chronic kind, and  many of them go on from  day to
day without any increase of the disease or improvement in their con- 
MECHANISM OF THE ACTIONS OF THE CORD.         287
dition.  In two examples of this variety we ventured to predict disease
of the posterior columns of the cord: and this was found to exist on a
post-mortem  inspection.   All cases  on  record, which we have had
the opportunity of examining, in  which the posterior  columns were
the seat of disease, began  by evincing more  or less disturbance of the
locomotive powers; and it seems to us that the degree to which sensi-
bility may become affected  will  greatly depend  upon the extent  to
which the posterior roots of  the nerves are involved in the disease.
   The  hypothesis, then, which we are  most  disposed to adopt, is the
following:—That the antero-lateral columns  of the spinal cord with the
gray matter are, in connection with the brain, the recipients of sensi-
tive impressions and volitional impulses, and that they are the centres
of the independent or physical nervous actions of the cord; and that
the posterior columns propagate the influence of that part of the  ence-
phalon which combines with  the nerves of volition  to regulate the
locomotive powers,  and  serve  as commissures  in harmonizing the
actions of the several segments of the cord.
   What is the mechanism  of these actions of the spinal cord—mental,
physical, locomotive ?  This is a problem of  the highest interest, bear-
ing upon the mechanism by which nervous  power  developed in any
nervous centre, as well as in  the cord, is capable of affecting peripheral
parts ;  and it is on that account  well  deserving the  most patient in-
vestigation.
   We assume, as necessary postulates, preliminary to  the discussion
of this question, the two following propositions:—1. That the brain,
or some part of it, is the sensorium commune; or in other words, that
mental nervous actions (acts of  volition and sensation) cannot take
place without the brain.   2. That the vesicular is  the  truly dynamic
nervous matter, the source of  all nervous power.*                   •
   The  following hypotheses have been  proposed in  explanation of
these actions.

   * The first of these postulates will be considered farther on  in this chapter. The
second appears to us to have a sufficiently firm foundation to warrant us in assuming
its correctness, for the sake of arguing the important  question referred to in the text.
We shall state briefly here the proofs that the association of the vesicular and fibrous
matter is necessary to the development of nervous force.
   1. Nerves, when separated for a time from the nervous centre, lose all power of
stimulating their muscles to contraction. No irritation, mechanical or electrical, is
sufficient to excite  them.  If a  nerve be divided some distance from the centre, the
peripheral portion, will, after a time, waste, and lose all power of developing nervous
force; but the central portion, which remains in connection with the centre, retains
its nutrition and its vital properties unimpaired.
   2. All nervous centres contain vesicular matter, with which nervous fibres freely
intermix.
   3. The power of a nervous centre appears to be proportionate to the quantity of its
vesicular matter. This is well exemplified in the cerebral convolutions, the vesicular
surface of which is always in the direct proportion  of the development  of  mental
power; or, in general terms, the gray matter increases in the exact ratio of the nervous
energy.  (Grainger.)
   4. AH nerves appear to arise from vesicular matter.  Stilling represents special
accumulations  of vesicular matter at the origins of the nerves of the medulla
oblongata.
   5. Nerves, whose power is exalted for some special purpose, have an increased
quantity of gray matter at their  origin, of which the electric lobe in the  torpedo,
connected with the origins of the fifth and eighth pairs of nerves, is an extraordinary
instance.—See Mr. Grainger's excellent  work on the Spinal Cord, pp. 18-21. 
288
INNERVATION.
    1. The various muscles and sentient surfaces of the body are con-
 nected with the brain by nerve-fibres, which pass from the one to  the
 other.   Those fibres  destined for, or proceeding from, the trunk to
 the brain pass along the spinal cord, so that  that organ is in  great
 part no  more than a bundle of nerve-fibres going to and from  the
 brain.   These fibres are  specially for sensation and voluntary motion.
    But, in addition to these, there is another class of fibres proper to
 the spinal  cord and to  its intra-cranial continuation, which form a
 connection with the gray matter of the  cord.   Of these fibres, some
 are afferent or incident, others efferent or reflex, and these two kinds
 have an immediate but unknown relation to each other, so that each
 afferent nerve has its proper  efferent one, the  former being  excitor,
 the latter motor.   The aggregate of these fibres together with the gray
 matter constitutes the true spinal cord of Dr. Marshall Hall, which is
 not limited to the  spinal  canal, but passes up into the cranium as  far
 as the crura cerebri.   These fibres are quite independent of those of
 sensation  and volition, and of the sensorium  commune.   Although
 bound up with sensitive and  motor fibres, they are not affected by
 them, and they maintain  their separate  course in the nerves  as well
 as in the centres.  Such is the hypothesis of an excito-motory system
 of nerves, and-of a true spinal cord, the  centre of all physical nervous
 actions, which has been proposed and  most  ably advocated by Dr.
 Marshall Hall.
    2. The fibres of sensation and  volition proceed to and from  some
 part or parts of the intra-cranial mass.   Those which are distributed
 to the trunk pass along the spinal cord, separating from it with  the
 various roots of the nerves, and in their course within the spine they
 mingle more or less with the gray matter.  There are no other fibres
*but these (save the commissural), and they are sufficient to manifest  the
 physical as well as the mental  acts.   Nerves of sensation are  capable
 of exciting nerves of motion  which are in their vicinity; and they
 may produce this effect even  when the  spinal cord has been  severed
 from the brain, for their relation to the gray matter of the cord is such
 that their state of excitement is readily conveyed to it.  This explana-
 tion tallies with the  views of  Whytt, Prochaska, and the other phy-
 siologists who had recognized the existence of a  class of actions
 produced by the influence of sensitive upon motor nerves.
    3. According to a third hypothesis, it is assumed that all the spinal
 and encephalic  nerves,  of whatever  function, are  implanted in  the
 gray matter of the segments of the cerebro-spinal centre with which
 they are severally connected, and do  not  pass  beyond them.  The
 segments are connected with each other through the continuity of the
 gray matter from one  to  another,  and through the  medium of com-
 missural fibres which  pass between  them.  Through these  means,
 motor or sensitive impulses are propagated  from  segment to segment;
 and a  stimulus conveyed to  any segment from the periphery may
 either simultaneously affect the brain and cause a  sensation, or  be
 reflected upon the motor nerves of that segment and stimulate their
 muscles to contract. 
DR. HALL'S HYPOTHESIS.
289
  The first hypothesis, which  assumes the existence of a distinct
series of incident and reflex nerves for the physical nervous actions,
offers a very beautiful  explanation  of those cases in which, while
sensation is entirely destroyed,  movements may yet be excited with-
out the consciousness of the individual.   In such cases it is supposed
that the fibres of sensation and  volition are  alone paralyzed, but that
those of the true spinal cord remain free  from injury or disease, and
therefore competent to perform their functions.  Sometimes, however,
these fibres participate in  the general shock which the spinal cord or
brain experiences at the onset  of disease or accident, and therefore
reflex movements are not to be excited in all cases in which the in-
fluence  of  the brain has been cut.off by disease of that organ, or of
the cord itself.
   This hypothesis has very much to commend it; and not  the least
argument in its favour is  that  drawn from  the compound nature of
spinal nerves, as proved by Bell, in which filaments of very different
endowments are bound together in the same sheath.   If it be proved
that filaments of sensation and  of motion may be  thus tied together,
it is not going too far to conjecture the existence of another series of
fibres of distinct function.
   The movements of decapitated animals, of parts in connection with
small segments of the spinal  cord, of limbs paralyzed to  sensation
and voluntary motion from diseased brain or spinal cord, are satisfac-
torily explained by  this hypothesis.  But there are two phenomena
familiar to those who observe disease with a knowledge of the many
interesting  discussions now going on upon the nervous system, which
are not explained by it: these are, the movements which may be ex-
cited by mental emotion in limbs paralyzed to the influence of the
will, and the total paralysis of the sphincter  ani, which frequently
accompanies diseased brain, whilst, at the same time, the limbs are
only affected to a partial degree.
   Cases occur  sometimes in which  hemiplegia  arises from an apo-
plectic clot or other destructive  lesion in one hemisphere of the brain.
The arm and leg, or either of them, are completely removed from the
influence of the will; yet, occasionally,  under the  influence of some
sudden  emotion, fear, joy, surprise, the  palsied limb is raised invo-
luntarily with considerable force.*  Mental emotions probably affect
some part of the brain: if the only communication between the brain
and the limbs be by the fibres of sensation and volition, it is impossi-
ble to understand how, in such  a case, the emotional influence could
be conveyed through a channel  which has long been stopped.  If we
are to adopt Dr. Hall's theory,  it will be necessary to  suppose, with
Dr. Carpenter,  the  existence of certain  emotional fibres  to explain
the phenomena of this particular case.   But it is  difficult to admit
the existence of three  orders of fibres in  each muscle, which, to be
effective, must have the same relation to the component elements of
the muscle.  It is  impossible  to  imagine how each order of fibre

  * Even so  slight a cause as yawning, which is an action of emotional character,
will excite a palsied limb. In the case of a patient now in King's College Hospital
with very complete hemiplegia, the arm is raised involuntarily every time he yawns. 
290
INNERVATION.
should comport  itself with  reference to the other two, so that their
actions may not interfere.   Nor can any one fail to perceive that the
emotional fibres must be infinitely less frequently employed than  the
others, and in some individuals, so little called into action, as to  ex-
pose the fibres greatly to the risk of atrophy for want of use.
  Paralysis of the sphincter ani is most frequently produced by dis-
ease of the spinal cord ; but it is by no means a rare accompaniment
of diseased brain, and generally indicates  a lesion of grave import.
Now, such a lesion is always accompanied with  paralysis, chiefly of
the hemiplegic kind, but not necessarily complete ; on  the contrary, in
several such cases we have seen distinct reflex movements, indicating,
that although the brain's influence was withheld from the limbs, that of
the cord was not.   If then  the cord be  sufficiently free from morbid
depression to allow of reflex movements taking place in the inferior
limbs, why is the sphincter  so completely paralyzed that it offers  not
the slightest resistance to the introduction of the finger into the anus?
It is admitted that the  sphincter is  under  the influence of  the will;
according to  Dr. Hall's theory, this must be through special fibres of
volition  distributed to  it: but it is  also under the influence  of  the
spinal cord,  as the limbs are; yet, if the cerebral fibres be diseased,
there seems  no  reason why  the influence of the cord  upon  it should
be at the same time destroyed.   A cerebral lesion ought not to affect
the sphincter further than to destroy the control  of the will upon it,
unless its depressing influence extend to the whole  cord, and in such
a case there ought to be complete paralysis of the limbs likewise.
  These are  not unimportant  pathological  objections  to this theory:
to them we  must add  the fact, that  this view wants  the support of
anatomy.  However disposed we  may be  to admit the existence of
fibres implanted solely in the gray matter of the cord,  it must be con-
fessed that it is  as yet far from being proved that either such fibres,
or those which are continued up into the brain, exist in the cord of
vertebrata, or in its analogue of the invertebrata.   Dr. Carpenter and
Mr. Newport, it is true, affirm that they have demonstrated the  two
sets of fibres in  insects—the sensori-volitional, and the excito-motory.
The former author describes the nerves of articulata as consisting of
fibres  derived from two sources—namely, the anterior or cerebral
ganglion, and the ganglion of that segment  of the body to which they
belong.  Those fibres which are connected with the brain, he states,
pass down along the dorsal surface of the ganglionic  chain, and  are
fibres of sensation and voluntary motion ; those which are immediately
implanted in  the ganglia are excito-motory.   Mr. Newport, in  his
recent able and elaborate description of the nervous system of Myria-
poda, thinks  that he shows  a somewhat similar arrangement in those
animals.  The ganglionic chain has on  its dorsal  surface  a pair  of
columns, superior longitudinal fibres, which pass  over the ganglia,
sending a few fibres to mingle with them,  or with an  inferior pair of
longitudinal  columns.   These  latter, the inferior longitudinal fibres,
are placed along the abdominal surface of the ganglionic chain, and
are intimately connected  with the ganglia.   In the  intervals between
the ganglia these two  columns  lie in close juxtaposition, separated 
MR. NEWPORT'S RESEARCHES.
291
only by some transverse fibres.   The inferior columns appear, as Mr.
Newport states, to receive fibres from the superior columns, and pro-
bably to send some to  them, "thus decussating each  other in  the
middle  substance of the cord, where these two longitudinal series are
in close apposition;  since it is almost  impossible, even in the large
nervous cord of Scolopendra, to separate these two tracts from each
other, although their distinctness is evinced in their relative size and
longitudinal lines of separation."*   The  ganglia, then, are placed
between these two  columns, the inferior pair being intimately con-
nected  with them.  Almost the whole  of the  fibres  of the  inferior
longitudinal series  are  traceable, says  Mr. Newport,  in the  Iulidae,
directly through each  enlargement  of
assist to form.   Two other sets
the cord which they mainly

       Fig. 73.
 of fibres are distinguished by
 this anatomist in these animals,
 which  do not take a longitu-
 dinal course.  These are, first,
 the commissural  fibres, which
 pass transversely between cor-
 responding nerves of opposite
 sides of the body ; and second-
 ly, the fibres of reinforcement
 of the  cord,  which communi-
 cate  between  nerves  of  the
 same side of the body, passing
 from a nerve which arises from
 a superior ganglion to one that
 comes  from  an inferior one.
 These nerves do not appear to
 penetrate  the cord:  judging
 from Mr.  Newport's  descrip-
 tion, they  merely pass  from
 nerve  to nerve, forming  loops
 which are convex towards the
 cord, and constitute the lateral
 portion of the cord in the  in-
 tervals between the points of
 emergence of the nerves with
 which   they  are  connected.
 The two sets  of transverse and
 lateral fibres agree in  the fact
 that they do not pass upwards to the brain; but of their connection
 with the cord nothing is known.   Indeed it is by no means apparent
 that the  lateral fibres form any junction with the vesicular matter  of
 the cord or with any other than peripheral portions of the  nervous
 system ;  Mr.  Newport's  researches  show only that they are in juxta-
 position  with  the margins of the cord, but we cannot infer from them
 that they mingle with its elements.  Moreover it is  far from being
proved that the  longitudinal fibres pass up to the brain.  The brain,
 Upper and under surfaces of a portion of the cord
in Spirostreptus.—After Newport.
 a. Under surface, b. Upper surface.
 a. Inferior longitudinal fibres. «. Superior longitu-
dinal fibres,  f. Fibres of reinforcement, also seen at
b and c. g. Commissural fibres, also seen at d, a.
•Phil. Trans., 1844. 
292                      INNERVATION.
indeed, is not necessarily the largest of the ganglia, and it must be
admitted to bear a most inadequate proportion to the number of longi-
tudinal fibres.  Let any one compare the size of the cerebral ganglia
of the scorpion (as figured by Mr. Newport) with the size  of the
animal and that of its cord, and it will be evident to him how dis-
proportionately small such  a centre is to the number of sensori-voli-
tional fibres which must be distributed over so large a surface, and to
so many muscles.  When too it is stated that the observations of these
physiologists  were made with low powers of the microscope, it must
be confessed  that there is as much obscurity as to the origin of the
nerves in invertebrata  as  in  vertebrata;  and that we are not yet
entitled to conclude that the existence of two  orders  of  fibres has
been actually demonstrated in the former class.  Anatomy offers no
objection to the hypothesis that the roots of the nerves are implanted
in the  ganglia, and that the longitudinal fibres  act as  commissures
between different segments (both adjacent and remote) of the cord.
   And  we may add here, that  Mr.  Newport's  experiments on the
myriapods and other articulata throw no light on the question of the
existence  of  two orders of fibres ; nor do they add anything to our
knowledge beyond the important fact,  that actions take place  in in-
vertebrata after decapitation which are of the same nature with  those
which occur in vertebrata after a similar mutilation. The mechanism
of these actions has not been at  all elucidated by these  experiments.
   Respecting the  second hypothesis, we must remark, that it is just
as competent to explain the phenomena of decapitated  animals, and
paralyzed limbs, as that of Dr. Hall, and that it receives some support
from the almost universal concurrence of sensation with  those normal
actions which Dr. Hall would attribute to excito-motory fibres.   If it
be supposed that these fibres have a certain relation to the gray matter
of the spinal cord, there can be  no good reason against the further
supposition, that they may continue to be affected by it after the  brain
has been separated from  the cord.   This hypothesis, however, is
liable to the  same objections as that of  excito-motory fibres: it is
inadequate to explain the influence of emotion on paralyzed limbs,
and the paralysis of the sphincters; and,  moreover, it cannot be con-
sidered to be proved that fibres  are  continued  up directly from the
spinal nerves to the brain.   The fibres of the  anterior pyramids, no
doubt, are true cerebro-spinal fibres;  but they may be  merely com-
missural.  We have no evidence that fibres of the lumbar  region of
the cord pass into the brain.  The longitudinal course of fibres in the
spinal cord affords no proof that those fibres pass into the brain, for it
is well known that most of the nerves take a very oblique course from
their point of separation from the cord to  their emergence from the
spinal canal; and it is probable that the fibres continue their obliquity
in the cord itself, so that their  real origin would be  higher up than
their apparent one.   This great length of oblique course gives to the
fibre the appearance of being strictly longitudinal, whereas  it may be
implanted in  the gray matter of  the cord.
   The  third  hypothesis appears  to us to  admit of fewer objections
than either of the others, and to be more consonant with what seems 
MECHANISM OF A VOLUNTARY ACTION.
293
to be the correct anatomy of the cord.   It supposes that the mechan-
ism of a mental and that of a physical nervous action are  essentially
the same, differing only in the nature and the mode of application of the
stimulus.  The same afferent and efferent fibres are  exerted in the one
case as in the other; the  former acting as sensitive or excitor, or both;
the latter as channels for voluntary, emotional or strictly physical im-
pulses to motion.
  This hypothesis is content to  assume that fibres of sensation  and
voluntary motion do not pass beyond that particular  segment of the
cord with which they are connected; and that each  segment of the
cord communicates readily *vith the brain  through the horns of gray
matter, or through  commissural fibres which pass  between the seg-
ments  of the cord, and from the upper segment of the latter to the
brain.   The anatomy of the cord, so far  as our present knowledge
extends, is favourable to  this  hypothesis, for it is much more probable
that all the roots of the  spinal  nerves are implanted in their proper
segments of the cord, than that some pass up to the brain, and others
remain in the cord.  The varying dimensions of the cord,  at different
regions, disincline us to  admit the existence of fibres which are con-
tinued up into the brain from the spinal nerves.  It is impossible  to
understand the great superiority of size of the lumbar portion over the
dorsal segment of the cord, if we admit that this latter segment con-
tains, in addition  to its own fibres, (sensori-volitional and  excito-
motory,) the sensori-volitional  fibres of the lumbar swelling  also.
The fibres of sensation and volition, which pass to the great  lumbar
and sacral nerves, could, in that case, be  only  extremely few in pro-
portion to the excito-motory  ones; nor would they seem adequate  to
the motor and sensitive endowments of the lower extremities; where
it must be admitted volition  and sensation enjoy an extensive sway.
Moreover, it may be stated that  the great size of the lumbar swelling
depends mainly on the large  quantity of vesicular matter which exists
in it;  and the  total amount of fibrous  matter is  hardly so much  as
might  be expected to exist  if  the lower  extremities  and the  pelvis
were supplied  with  both sensori-volitional and excito-motory fibres.
   It is very generally admitted that the only channel by which the
will can influence the spinal cord is through the fibres of the anterior
pyramids, the greater number of which decussate each other along
the median line, as already explained in page 241.  The most frequent
pathological phenomena favour this view.   Now it is in the  highest
degree improbable that  these  fibres, occupying so small a space  as
they do, should form the aggregate of the  volitional fibres (still less
of the  sensori-volitional fibres) of the trunk and extremities.  It seems
to us much more  reasonable to  regard  the fibres of the pyramids  in
the light of commissures, connecting the gray matter of the cord with
that of the  brain,  and serving to associate these two great divisions
of  the cerebro-spinal centre  in the voluntary, if not in all the mental
nervous actions.
   The mechanism of a voluntary action, in parts, supplied  with spinal
nerves, would  be, according to  this hypothesis, as follows:  The im-
pulse of volition, primarily excited in the brain, acts at the same time 
294
INNERVATION.
upon the gray matter of the cord (its anterior horn), which in virtue
of its association with the former, by means of the fibres of the ante-
rior pyramids, becomes part and parcel of the organ  of the will, and
therefore as  distinctly amenable to acts of the  mind as that portion
which is contained within the cranium.   If we destroy the commissural
connection through the pyramidal fibres, the spinal cord ceases to take
part in mental actions; or, if that  connection  be only partially de-
stroyed, that portion of the cord which the injured fibres had associated
with the brain, is no longer influenced by the mind.   Again, if the
seat of  volition in the brain be diseased, the cord, or part  of it, par-
ticipates in the effects  of the disease, as far  as  regards voluntary
actions.  That it is not too  much  to ascribe such power to the pyra-
midal fibres,  appears reasonable, if we consider how the fibres of the
corpus callosum, and perhaps other transverse commissures, so con-
nect the hemispheres and other parts of the brain that  the  separate
divisions of a double organ act harmoniously in connection with the
operations of a single mind; or that, conversely,  two impressions from
one and the same source on a double sentient organ are  perceived as
single by the mind.
  An  objection to  this explanation will readily be  raised, that the
excitation of the anterior horn  of the gray matter, in the way stated,
does not explain the remarkable power which the  will has of limiting
its action to one or two, or a particular class of  muscles.  We  reply
to this,  however, that there can be no reason for denying to the mind
the faculty of concentrating its action upon a particular series  of the
elementary parts of the vesicular matter, or even upon one  or  more
vesicles, if we admit that it can direct its influence  to one  or  more
individual fibres, as the advocates of the first and second hypotheses
do.   If, indeed, we admit  the one, we must admit the other; for
whether the primary excitation  of a fibre take place in the encephalon
or in the spinal cord, the part first affected must probably be  (accord-
ing to our  second postulate) one  or  more vesicles of the gray sub-
stance.
  The  series of changes which would develop a sensation, admits
of the following explanation : A stimulus applied to some part of the
trunk or extremities is propagated by the  sensitive nerves  to the
posterior horn of the  gray matter  of  the spinal  cord, and from the
junction of this part with the brain either through the direct continuity
of the vesicular matter of the cord with that of the centre of sensa-
tions, or through longitudinal commissural  fibres, analogous to, or
even  perhaps forming part of, the  anterior  pyramids, this organ is
simultaneously affected.   To this likewise it will be objected, that
the limitation of sensations is not sufficiently explained.   But the
reply is obvious: the intensity and kind of sensation depend upon the
nature of the primary stimulus at the  surface;  the  extent upon the
number of  fibres there stimulated.   Wherever these fibres form their
proper organic connection with the vesicular matter, that matter will
participate in their change to an extent proportionate to the number of
fibres stimulated, and with an intensity commensurate with the force
of the primary stimulus.  It is not necessary to the development of 
THEORY OF NERVOUS ACTION.               295
sensation that the fibre stimulated should be implanted directly in the
brain ; if it be connected with this  centre  through the medium  of
vesicular matter of the same character as that which is found in it  or
through commissural fibres, all conditions necessary for the develop-
ment and propagation of nervous  force would appear to be fulfilled.
It must not  be  supposed, however, that in making this statement we
mean to assign the spinal cord to be  the  seat of sensation ;  all we
assert is, that the posterior horns of its gray matter, as being the part
in which the sensitive roots are implanted, participate largely in the
mechanism  of sensation; and that  by their  union with the brain they
become, pro tanto, a part of the centre of sensation, so long as that
union is unimpaired.
   This hypothesis offers an explanation  of the hitherto unexplained
phenomenon of impaired sensation on that side of the body which is
opposite to  the seat  of cerebral lesion.   If we  regard the anterior
pyramids  as commissures between the sensitive, as well as between
the  motor portions of the  cerebro-spinal centre, it will be obvious
that the posterior  horns  of the spinal gray matter on the right side
will be associated with the left centre of sensation in the brain, and
vice versa.
   And we  gain,  moreover,  an  explanation  of the almost universal
association of sensation with reflex or physical actions.  The excitor
nerves of these actions being the  same as the sensitive nerves, the
impression conveyed  by  them is calculated at once  to excite motion
and sensation.   Were it not for the  controlling influence of the will,
all sensitive impressions made through the spinal cord would likewise
be  accompanied  by  corresponding  movements.   When  the  spinal
cord  has  been excited  by strychnine, the physical power prevails
over the mental, and  the will ceases to be able to control the  move-
ments excited by impressions through sensitive nerves.
   A highly  important argument in favour of this view is  derived from
the marked  difference of structure  of the anterior and posterior horns
of the spinal vesicular matter.  The anterior and posterior roots  of
the  nerves  exhibit no difference  of structure ;  no anatomist  could
distinguish  in  a compound nerve  the  sensitive  from the  motor fila-
ments. The vesicular matter, however, in the anterior horn, contains
large caudate vesicles of a remarkable and peculiar kind  (fig. 56,  p.
198) ; whilst  that in the posterior horn resembles very  much the
vesicular matter  of  the  cerebral convolutions, and of other parts  of
the cerebrum, and does not  contain caudate vesicles, except near the
base.  Here, then, we  find associated with  the  well-attested differ-
ence in the  functions of the anterior and posterior  roots, a striking
difference in the structure of the anterior and  posterior horns of gray
matter.
   This hypothesis is  adequate to the explanation of the influence  of
emotion  or limbs paralyzed as to voluntary movement, without the
necessity of assuming the existence of a totally distinct series of fibres
for this class of actions.  The change in the brain, excited by emotion,
is propagated to the spinal gray matter, in a manner analogous to that
in which  the influence of the will is brought  to bear on it.   It thus 
296
INNERVATION.
affects the ordinary motor fibres; and, therefore, the movements which
are produced by emotion  resemble very closely those excited by the
will.
   This hypothesis suggests  a very obvious  explanation of the kind
of antagonism which appears  to exist between voluntary and reflex
actions.  It is well known that in health the will can in a great de-
gree control  and prevent the development of reflex actions  in the
lower extremities.  If  one be paralyzed, as  in hemiplegia, from dis-
ease of the brain, whilst  the other  remains  sound, a  very striking
contrast is  sometimes to be observed between the two limbs.  On
stimulating the sole of the foot in the diseased limb, reflex actions are
readily produced ; but, on applying the same stimulus to  the same
part of the sound limb, no such movements occur, the patient being
conscious of the application of the stimulus, but resisting the tendency
to action which it produces.   The will has lost its  control over the
diseased limb ;  but, as the motor  nerves and the  spinal gray matter
are sound, actions may still be excited through a  stimulus from the
periphery; and, the  more complete has been the separation  of the
brain's  influence  from  the cord, the  more perfect will be the reflex
actions.  Hence  we frequently find  these  movements  more perfect
in cases where sensation as well as voluntary power is destroyed in a
limb, than  where the latter only has ceased.
   It may be here remarked, that  movements which  at one time are
voluntary,  may at another time be physical.   If the influence of the
will be suspended for a brief  period,  stimulation of  the surface  will
produce the same movements which previously were excited by volun-
tary impulse.  Thus, tickling the soles of the feet, in a person asleep,
excites movements which doubtless are of the reflex kind ; but the
same stimulation, in a person awake, will give rise to precisely the
same movements, which he is conscious are, at least in a great degree,
voluntary.
   Some  reflex actions are  imperfectly controllable by the will; of
which the contraction of the pupil, and the  movement of deglutition
at the isthmus faucium, are examples.   It  is remarkable, however,
that the will  may give rise to these actions by associating others with
them : the pupil may be contracted at will, by directing the  eye in-
wards ; and the fauces may be contracted by bringing some saliva in
contact with them.   In the latter case the stimulus of volition alone
is not sufficient to excite  the movement; the addition of a physical
stimulus is likewise necessary: and,  in the former, the excitability of
the fibres of  the third nerve by a mental stimulus  may be materially
modified by their re-association with vesicular matter in the ophthalmic
ganglion.
   There is nothing in this hypothesis repugnant to the idea, that cer-
tain nerves may be connected in the centres with masses of vesicular
matter over which the will usually exercises little  or no control, and
which, perhaps, have but a  slight  connection with  the brain  through
commissural fibres.   Facts like those instanced in  the preceding para-
graphs  may  be  accounted for on  such a supposition as this.   This
supposition may be required to explain  some of the  actions of nerves 
           MANY ACTIONS NEED A DOUBLE STIMULUS.         297

connected with  the  medulla oblongata, the vagus  for instance, but
certainly not of spinal nerves.
  It is  probable that in  many actions the double  stimulus, mental
and physical, is necessary to their perfect development.   The former
is excited by the mind  acting on the vesicular matter; the latter is
propagated at the same time, by  sensitive nerves, to  the same region
of vesicular matter; and both simultaneously influence the same mbtor
fibres.   In locomotion, it  seems  probable  that this  is the case: the
degree of contraction of the muscles necessary to maintain the super-
incumbent weight is obtained by the physical  stimulus  of pressure
against  the soles of the feet; but the movements of the limbs, and
the harmonizing association of the muscular  actions, are effected by
mental  influence.  The pressure against the  soles is felt, however;
and the same nerve-fibres which excite  the sensation, stimulate the
vesicular matter in which  the motor nerves are implanted.   In many
actions of familiar occurrence, the voluntary effort is  greatly enhanced
by the simultaneous  application  of a physical stimulus to  a part of
the surface which is supplied with nerves from the same region of the
cord.   The horseman feels  more secure  when his  legs  are in close
contact  with  the horse's  flank.   We gain a much firmer hold of an
object which adapts  itself well to  the palmar surface of the  hand,
than of one which, although  of no greater bulk, is yet so irregular
in  surface  as not to  allow of such intimate  contact with the palm.
Closure of the eyelids in winking is an action of similar1 kind, result-
ing from a physical stimulus, which, in the perfect state of the cerebro-
spinal centre, produces sensation, and excites motion which is at once
the result of the physical impression, and of the exercise of volition
provoked by the sensation.   Every one  must be conscious that he
exercises considerable control over the movements of his eyelids, and
that it requires a great effort to prevent winking for  a  certain period.
At length, however, the physical impression, arising from the contact
of air with the conjunctiva, and  the diminution of temperature  from
evaporation on  the surface of that membrane, which at  first caused
but a slight sensation, produces pain ; the physical stimulus overcomes
the mental resistance, and causes contraction of the orbicular muscle.
And it may be remarked further, that the closure of the lids by volun-
tary effort is much more powerful if a stimulus be applied at the same
time to  the conjunctival surface, than if left solely to the exercise of
the will.
  In the action just  referred to, as well as  in  all other  instances of
reflex actions which  the will can prevent, no  satisfactory  explanation
of this  controlling power of the mind  can be  given by Dr. Hall's
hypothesis—Do the  volitional fibres exceed in number the excito-
motory?  If this were  admitted, then we could understand that an
excito-motory act might be prevented by substituting a voluntary act
for  it;  but, in  the cases in question, the mind prevents action  alto-
gether, notwithstanding the exciting influence  of the impression.  The
true explanation seems to  be, that the  mind can exert upon the vesi-
cular matter a power which can prevent the exercise of that change,
    20 
298
INNERVATION.
or neutralize the change, without which the  motor fibres will not be
affected by a physical stimulus.
   Reflex  actions are more  manifest in  some situations than others:
thus, in cases of hemiplegia from diseased brain, they are generally
very obvious in the lo^wer extremity, but totally absent in the  upper.
This, the  advocates of the excito-motory theory ascribe to a paucity
of excito-motory fibres in the latter  limb, and  to a larger amount of
them  in  the former.  Or, it has been attributed to the greater and
more enduring influence  of shock upon that segment of the cord from
which the nerves of the  upper extremities arise, as nearer the seat of
lesion, than upon the lumbar segment.   But another explanation ap-
pears to us  equally satisfactory,  and more accordant with other phe-
nomena.   A certain  disposition of  the nerves  upon the tegumentary
surface is  as necessary for the development of reflex actions as of sen-
sations; and these movements will be more or less easily manifested,
according as this organization of the nerves on the surface is more or
less perfect.
   That disposition of the cutaneous  nerves which renders the surface
easily excitable by titillation seems most favourable to the develop-
ment of these actions.  Hence, there is no place where they are more
readily excited than  in the lower extremities by stimulating the soles
of the feet or the intervals between  the toes,  both of which situations
are highly susceptible of titillation.  At the isthmus  faucium  the
slightest touch on the surface excites a movement of deglutition ; and
this touch, at the same  time, produces  a very peculiar sensation  of
tickling, quite distinct from  that which may be excited at other parts
of the pharynx, or mouth.   When this part of the mucous membrane
is  in a state of irritation  as an effect  of coryza,  this tickling sensation
is  present, and repeated  acts of swallowing are provoked.
   Two facts may be stated here, which illustrate the position we have
laid  down respecting the necessity of  a certain  disposition  of the
nerves on  the tegumental surface, for the development of reflex actions.
The first is one which has been noticed by Volkmann, and which  we
had ourselves  repeatedly observed,  namely, that in frogs, and other
animals, reflex  actions are readily excited by  stimulating the feet; but
irritating the posterior roots of the spinal nerves, which supply those
parts, is not sufficient for this purpose.  In experiments repeatedly
made upon the posterior  roots of the nerves we have very rarely seen
movements excited whilst they have been subjected to irritation, and
the recorded statements  of all modern  experimenters agree  in  the
main with this  statement.   The second fact is  this:  in the male frog
the development of a papillary structure  on  the skin  of the  thumb
seems to have reference to the excitation of the physical power of the
cord, to enable the animal  to grasp the female without the necessity
of a prolonged  exercise of volition.   Stimulating  the fingers will
scarcely produce reflex actions, but the slightest touch to the enlarged
thumb will cause the animal to assume the  attitude of grasping.   If
the papillae be shaved off the thumb, its power of exciting these ac-
tions is instantly lost.
   When the polarity of  the cord is  greatly excited by strychnine  or 
          DISPOSITION OF NERVES FOR REFLEX ACTION.       299

other substances, or when tetanus exists, all parts of the surface  are
equally capable of exciting reflex actions.  The least touch will cause
them, not only in the  limb touched, but in all that side of the trunk,
or even  throughout  the whole body.   So general is the  excitation,
that  the least impression made on the peripheral extremity of a sensi-
tive  nerve in any part of the body is instantly converted into muscular
spasm, more or  less  general.  A  slight current of air, in  tetanus,
is sufficient  to excite  general spasm.   Muller remarks, that,  in such
states of the cord, the reflex actions excited by stimulating the nerves
themselves  are much less than those produced by excitation of the
surface.
  The readiness with  which a physical change, induced in one part
of the centre, is propagated to others, whether above or below it, is
due  no doubt to the vesicular matter.  An experiment  made by Van
Deen illustrates  this statement.  If, in an animal poisoned by strych-
nine, the cord be  divided in its entire length along the median line,
leaving only a slight bridge of gray matter, stimuli  applied  to  any
part  of the surface will exhibit as extensive reactions as  if the cord
were entire.   It  is evident  that the only medium of communication
between the opposite halves, must be the small portion of vesicular
matter left undivided.
  Impressions conveyed to the cord by the posterior roots of any of
its nerves, may  be reflected to the corresponding motor nerves  and
cause movement, or may extend irregularly along the posterior horns
of gray matter, and stimulate the  nerves implanted  in them, and thus
give rise to  new sensations, which may be referred  to other and even
distant parts of  the body.
  The hypothesis, under consideration, affords  us an explanation,
more satisfactory than any other,  of the paralytic state of the sphinc-
ter ani in brain  disease, already referred to, as well as in  that of the
spinal cord.   This muscle is certainly chiefly under the influence of
the will.  In ordinary cases of diseased brain where the lesion is con-
fined to one side, the centre of volition is not sufficiently impaired to
affect its influence upon the sphincter.   In  graver  lesions, however,
although the will may still continue to exert its control upon one side
of the body, it loses  its power over the sphincter,  which is  not ex-
citable by any stimulus.   In disease of the spinal cord, there is para-
lysis of the  sphincters if the lesion involve  a sufficient portion of the
cord's substance, in whatever region of the cord it may exist.   Even
when the lesion  is situate high up in the neck, or in the dorsal region,
leaving the  lumbar portion perfectly whole,  the sphincter will never-
theless be paralyzed.   In the former instances, the  centre of  volition
in the cranium is diseased ;  in the latter, the defect consists in  the
destruction of the communication of the brain with that portion of the
cord in which the nerves of the sphincter muscle are implanted.
  An examination of the action  of the sphincter will show that  the  .
anus is kept closed ordinarily by the passive contraction of the muscle
itself (see p.  180); but that its active contractions are mainly excited
by voluntary influence, allowance being made for some slight action
which may be produced by the stimulus of  sudden  distension, as in 
300
INNERVATION.
other circular  muscles.   Now, as a stimulus to  sentient nerves con-
stitutes no necessary part of any of these actions, it is  probable that
the motor nerves of the sphincter have little or  no connection with
the sentient ones ;  and, consequently, that muscle is not excitable to
contraction  by a stimulus applied to  a  sentient  surface.  Hence,
whenever the  influence of the will upon the lumbar portion of the
cord is suspended, this muscle ceases to act, whether a mental or  a
physical stimulus be exerted.
   Dr. Hall indeed cites two experiments which  imply that the action
of the sphincter is dependent  on the  cord.  In both, however, (one
on a horse, the other on a turtle,) the observations were made imme-
diately after division of the cord.  By the  division, the whole  organ
was thrown into an excited state, both above and below the section,
and therefore manifested phenomena similar to those excited by voli-
tion.   Indeed, we  have  seen the  sphincter repeatedly contracting
after division of the cord without the application of any new stimulus
to it;  and the dog continuing to raise and depress his tail  as long as
the irritation of  the cord produced by the section has continued.
   On the  same  principle, animals will exhibit movements of volun-
tary character  for some  time after decapitation.   A bird thus treated
will fly for some distance, and  with considerable energy, and will flap
its wings if the cut surface of the cord be irritated.  A fly decapitated
flies for some  way immediately after the  removal of the head ; and
Walckenaer observed a singular fact respecting the Cerceris ornata,
a wasp which  attacks a bee that inhabits holes: " at the moment that
the insect was forcing its way into the hole  of the bee, Walckenaer
decapitated  it; notwithstanding which, it continued its motions, and,
when turned round, endeavoured to resume its position, and enter the
hole."*  The  change in the vesicular matter of the ganglia necessary
for the  movements of the wasp  in pursuit of its prey, had already
been  excited by a powerful  stimulus  of volition, which  continued
even  after the  removal of the centre from which it had  emanated.
   So  similar is the  change which a physical stimulus can  excite in
the gray matter to that produced by the  influence of the will, that, as
has been often remarked, the actions  excited in  decapitated animals
present a striking resemblance to the ordinary voluntary movements.
When a certain portion  of the  skin is  irritated, the animal pushes
against the offending substance, as if trying to remove or displace it.
If the anus be  irritated, both  legs are excited  to action.  It  may
also be observed, that the same motions follow the same irritations of
the skin.  If, in a frog, the seat of irritation be on the right side, the
corresponding hind-foot will be raised, as if to remove the irritating
cause.  The exact resemblance of these to voluntary movements
seems to admit of  being explained  only on the  supposition that the
same  fibres are employed in the execution of both.
,   It must be borne in  mind, that, while this hypothesis rejects the
class  of sensori-volitional fibres which  pass with the spinal nerves
along  the cord  into the brain, it admits the existence of  only three

         • Quoted in Miiller's Physiology, by Baly, vol. i. p. 787, 2d ed. 
PHYSICAL ACTIONS OF THE CORD.             301
orders of fibres implanted in the various segments of the cord, viz.,
those at once sensitive and excitor;  those at once for voluntary and
involuntary  motion ; and commissural  fibres.  Moreover, it is  not
intended by this hypothesis to  assume that the intervention of sensa-
tion  (i. e. the  perception of an impression by the mind) is necessary
for the production of those  muscular actions which are excited by
stimulation of the surface.  No more is affirmed  than that the same
stimulus to the sensitive nerve which can and does excite a sensation,
may simultaneously, but independently, cause a change in the vesicular
matter which shall stimulate the motor nerves ;  and that this change
is of the same kind as that which the will may excite, and  affects the
same motor nerves.
   Lastly, this  hypothesis involves the  enunciation of a highly im-
portant proposition with reference to nervous centres.  It is this : that
all the  centres  which are connected  to  the brain  by commissural
fibres, are thereby submitted  to, and brought into connection  with,
the mind, to an  extent proportionate to the number of connecting
fibres, so that voluntary impulses act upon  them  as part and parcel of
the centre of volition ; and sensitive impressions, in affecting them,
affect the sensorium commune  simultaneously.
  In voluntary actions, then, it may  be stated,  that, while the brain
is the part primarily affected, the  mental impulse is at the  same time
directed  to that portion of the cord upon  which the required action
depends.
  In the development of sensation the stimulus affects the posterior
horns of the gray matter of the cord, which, from  its commissural
connection with  the brain,  is  in reality  a  part  of the sensorium.
When  the power of mental  interference is  removed, or kept under
control, physical actions develop themselves; being effected  through
the same nerves  as  those which  volition influences, or which sensi-
tive  impressions affect.  The latter are, in such instances, the  excitors
of the former,  no doubt through the vesicular matter in which  they
are implanted.  These actions become most manifest when the  con-
nection  of the  brain with  the spinal cord has been severed ; and they
occur in the most marked way in those situations where the  cutaneous
nerves are so organized as readily to  respond to the application  of  a
stimulus applied to the surface, or they become universal  when the
cord is in a state  of general excitement.
   The movements in locomotion and the maintenance of the various
attitudes, are effected through the ordinary channels of the physical
and  volitional  actions ; and the posterior columns of the cord,  by their
influence on the vesicular matter of the segments in which the nerves
are implanted, co-ordinate and harmonize  the complicated muscular
actions  of the limbs  and  the trunk under the control of that portion
of the  encephalon which probably is  devoted to that purpose.   This
power of co-ordination is probably mental, and  intimately  connected
with the muscular sense.
   To conclude the discussion of the  functions of the cord, we shall
here enumerate the physical nervous actions of which it is the centre,
remarking, at the same time, that we continue to  use the terra spinal 
302
INNERVATION.
 cord in its ordinary sense, and that we reject the hypothesis of a true
 spinal cord, anatomically distinct from that which has  to  do with
 mental nervous actions.
   We have already stated, that probably part of the muscular adjust-
 ments in locomotion are excited by the pressure against the soles of
 the feet.  All involuntary movements of the muscles of the trunk or
 extremities, when  excited by external stimuli, have their centre in
 the spinal cord.  The sudden application  of cold to  the surface of
 the  trunk  or extremities  frequently excites  respiratory movements.
 This may be attributed to cutaneous nerves affecting the gray matter
 of the cord, and through this the intercostal  and phrenic  nerves  im-
 planted in it.
   Certain conditions of the  generative organs are dependent on  the
 spinal cord ; but they are developed  only in a polar state of that
 organ, usually  present under sexual excitement.   Erection of  the
 penis  is evidently dependent on the  cord in this way.  In a state
 of irritation of the cord, such as may be  caused by traumatic injury,
 erection  or  semi-erection is frequently present.  In paraplegia there
 is frequently an absence  of  the  power.   The excited state  of  the
 Fallopian tubes in the female  is attributable to the  same cause.  The
 action of the uterus in parturition, of  the bladder and rectum when
 distended, is partly due to the stimulus of distension on the muscular
 coats,  and partly to the  physical power  of the cord  excited by  the
 sensitive nerves of those organs.
   The nervous  actions which accompany the nutritive functions  are
 of the physical kind, although not altogether removed from the  in-
 fluence of volition  and emotion,  and have their centre in  the  spinal
 cord.  Thus, the heart  is very liable to  be influenced by the  spinal
 cord, and, no doubt, the  blood-vessels are similarly related to it; and,
 through  their influence upon the distribution  of blood  to the various
 textures, it is plain that the state of the spinal cord, or of parts of it,
 may readily affect the molecular changes in which nutrition and secre-
 tion intrinsically consist.   This subject will  be further discussed when
 we come to consider the functions in question.
   It has been  supposed, that the tone  of the  muscular system is
 maintained by the spinal cord.   If by tone be meant what we have
 described as passive contraction, we  can only remark, that the phe-
 nomena  which  characterize that state are just as obvious in  muscles
 taken from animals recently deprived of the spinal  cord as in others;
 and  that the analogous state, rigor  mortis, comes on as distinctly
 when the spinal cord and brain have been  removed, as if they were
 untouched.   Healthy nutrition, in our opinion, supplies all the con-
 ditions necessary for the  maintenance of  the tone or the passive
 contraction;  nor is  the  spinal cord (although itself healthy) able  to
preserve  the tense condition of the  muscles, if they are not well
nourished.   The removal of  the spinal  cord,  indeed, immediately
produces a flaccid state of the muscles of the limbs; but this is owing
to the immediate cessation of the slight degree of  active contraction
necessary to maintain a  certain posture.  A decapitated frog will
continue  in the  sitting posture through the  influence  of  the "spinal 
FUNCTIONS OF THE ENCEPHALON.
303
cord ; but, immediately this  organ is removed, the limbs fall apart,
from the loss  of the  controlling and co-ordinating  influence of the
nervous  centres.  But careful examination will show, that in these
limbs the molecular phenomena which  characterize passive contrac-
tion continue.  It must be remarked, however, that muscles separated
from their proper nervous  connection soon  suffer  in their nutrition,
from the want of that amount of  exercise which is necessary for it.
For this important  observation we are indebted  to Professor John
Reid, who likewise called  attention to  the confirmatory fact, that, in
those palsies with which there is combined  more or less irritation of
the nervous centre,  the  muscles do not suffer  in their nutrition, in
consequence of the exercise they undergo in  the startings so frequently
excited in them by the central irritation.
   After these remarks, it is  scarcely necessary to  add, that we must
enter our protest against the doctrine which assigns the spinal cord as
the source of muscular irritability.  This doctrine, indeed, has  but
slender support either in reason or experience.  It is contrary to all
analogy to assign to one tissue the  power of conferring vital properties
on another.  If bone, tendon, and cartilage have their distinctive pro-
perties, they possess them  in  virtue  of some peculiarity inherent in
their mode of nutrition, and do not derive them from any other texture.
And, surely, it is too much to  suppose that a tissue, like muscle, so
complex in its chemical constitution, and so exquisitely organized for
the development of its  proper force, should be  dependent on  the
nervous  system, or a  portion of it, for its  contractile power!  Our
own experience is quite opposed  to the statement of Dr. Hall, that,
in cases  of palsy dependent  on cerebral lesion, the muscles of the
affected limbs acquire an increased irritability, from the cord, which
he supposes to  be the source  of  irritability, remaining intact, while
the influence of the  exhauster of  irritability (the brain) is removed.
In all our experiments, which have been numerous, we  have found
the palsied muscles less excitable by the galvanic stimulus than those
of the sound side, and the difference  has  been more manifest  the
longer the period since the paralytic  seizure.   Exceptions to  this
statement, however,  are found in  those cases in which the paralysis
has been accompanied with cerebral irritation sufficient to keep up a
state of more or less active contraction of  the affected muscles.*
   Functions of the  medulla oblongata,  mesocephale, corpora striata,
and optic thalami.—Although  the anatomist may  find it  convenient
to describe  these parts each by itself, it is impossible, in  the consi-
deration of their functions, to separate them completely,  they are so
closely connected with each other, and  the functions of one  part are
so readily affected by any change in those  of the  other.   Thus, the
olivary columns, which form  the central and most  essential part of
the medulla  oblongata, extend upwards through the mesocephale to
the optic thalami; and the anterior pyramids form an intimate con-
nection not  only with the vesicular matter of the  mesocephale, but,

        * See also Dr. Pereira's experiments, Mat. Med., vol. ii. p. 1301. 
304
INNERVATION.
to a great extent, with  that of the corpora striata.   All these parts
taken together, with the quadrigeminal tubercles, will be found to be
the centre of the  principal mental nervous  actions, and of certain
physical  actions which  are very essential  to  the integrity of the
economy.
   The office of the  nerves which  arise from the segment of the ence-
phalon throws light upon its function.  These nerves  are partly de-
stined for respiration, partly for deglutition, and partly also for acts of
volition and sensation.
   Destruction of the medulla oblongata is followed by the immediate
cessation  of  the  phenomena  of respiration  ; and  this  takes  place
whether  it be  simply  divided, or completely removed.  When an
animal is  pithed, he falls  down apparently senseless, and exhibiting
only such convulsive movements as  may be due to the irritation of
the medulla by the  section, or such reflex actions as may be excited
by the application of a stimulus to some part  of  the trunk.
   If, in an animal  which breathes without a  diaphragm, as in a bird
or reptile, the  spinal cord  be  gradually removed in successive por-
tions, proceeding from below, up to  within  a short distance  of the
medulla  oblongata, loss of motor and  sensitive power takes  place
successively in the  segments  of  the  body with  which  the removed
portions  of' the cord were  connected.  But  the animal still retains
its power of perceiving impressions made on  those parts of the body
which preserve their nervous connection with the medulla oblongata,
and continues to  exercise voluntary control over the movements of
those parts.  The movements  of respiration go on, and deglutition is
performed.  The higher senses are unimpaired.   (Flourens, p.  179.)
   These phenomena are sometimes observed in  man—in such  cases
as that alluded to in a former  page; where, from injury to the spinal
cord in the neck, below the origin of the phrenic nerve, the patient
appears as a  living head with  a dead trunk.   The sensibility and
motor power  of the head are  perfect; respiration goes on partially,
and deglutition can be readily performed.   The  senses and the intel-
lectual faculties remain for  a time unimpaired.
   Irritation of any part of the  medulla oblongata excites convulsive
movements in muscular parts which receive  nerves from  it, and,
through the spinal cord, in the muscles of the trunk.  Spasm of the
glottis, difficulty of deglutition, irregular acts  of breathing, result from
irritation of the medulla oblongata ;   and, if  the  excitement  be pro-
pagated to the cord, convulsions will  become more  or less general.
   If a lesion affect one-half of the medulla  oblongata, does  it pro-
duce convulsions or paralysis on the opposite side of the body ?  This
question  may be certainly answered in the affirmative, when the seat
of the lesion is in  the continuations of the  columns of the medulla
oblongata above the posterior  margin  of the pons.   It is not so  easily
solved, however, when the disease is situate below the pons.   The
results of experiment on this subject are contradictory, owing probably
to the extreme difficulty of limiting the injury inflicted to a portion of
the medulla on one  side;  and those of Flourens are of no value for 
FUNCTIONS OF THE ENCEPHALON.
305
the decision of this  question, as it appears  that he  injured chiefly
the restiform  bodies.   Anatomy suggests, that  a lesion  limited to
either anterior pyramid would affect the opposite side of the trunk, for
it is known  that such an effect follows disease "of  the continuation of
it in the mesocephale or crus cerebri;  and that lesion limited to the
posterior half of the medulla on either side would  affect the same side
of the body, no decussation  existing  between the fibres of opposite
restiform or  posterior pyramidal bodies.  The irritating or  depressing
influence of the lesion would probably be extended to the spinal gray
matter of the same side.
   That the medulla oblongata  is the channel  through  which the
operations of  the  brain are associated in voluntary actions with the
spinal cord, is shown by the fact that  paralysis of all the muscles of
the trunk follows the separation  of the latter organ from the former.
It seems not improbable that the centre of volition is connected with
one or both  of the gangliform bodies  (corpora striata and optic tha-
lami)  in which the columns of the medulla oblongata terminate above.
When the cerebral hemispheres have  been removed, as in Flourens'
and in Magendie's experiments,  the bird  is thrown into a deep sleep,
a state of stupefaction, and insensibility to surrounding objects.   But
he  can maintain his attitude-^stand—walk, when  first propelled—fly,
if thrown into the air.   This continuance of the locomotive power
implies some  degree at least of mental or volitional effort.  All the
animal's movements  have much  of the appearance of the exercise of
will, although, doubtless, many of them are in a great degree excited
by physical  stimuli.   Hence there seems reason to believe that the
will exerts a primary  influence upon either or both  of these  gangliform
bodies, more vigorous when  aided and guided by the  power of the
cerebral hemispheres.   The frequent  paralysis of motion apart  from
sensation when the upward continuations of  the pyramidal fibres in
the corpora  striata are  diseased, renders it extremely  probable that
these  fibres  are the media of connection between  the brain and cord
in voluntary actions.
   The medulla oblongata is not less the medium for the transmission
of sensitive impressions from all the regions of the head, trunk, and ex-
tremities ; and from its olivary columns at their upper and posterior part
being, as it  were, the concourse of all the nerves of pure sense, it
seems fair  to assign these parts  as the prime seat of those  central
impressions which are  necessary for  sensation.   The  reception of
these  impressions by  the cerebral hemispheres is the stage immediately
associated with mental perception.  True sensation, therefore, cannot
take place without cerebral hemispheres.   In a sensation  excited in
parts  supplied by  spinal nerves, the  first central  change is probably
in  the posterior horn of the  vesicular matter of  the cord; and the
olivary column of the medulla oblongata is simultaneously affected,
from its connection with the cord.  The change in this latter part is
then propagated to the cerebral hemispheres.
   Thus much  is suggested by anatomy, as regards the  mechanism of
sensitive impressions.   Experiment affords us no  aid in this intricate 
306                      INNERVATION.
and difficult subject; neither does pathological anatomy : for the parts
are so closely associated with each other, that any morbid state of one
readily involves the  others, so that it is almost  impossible  to find a
morbid state of the parts devoted to sensation, apart from an affection
of those  more immediately concerned in motion.
  The function of the  restiform bodies  is probably associated  with
that of the hemispheres of the cerebellum, and  of the posterior col-
umns of  the spinal cord.
  The experiments of Le Gallois and Flourens  render it certain that
the medulla oblongata is the centre of respiratory movements.   The
latter physiologist  assigns as the "primum movens" of these acts all
that  portion of the  medulla which  extends  from the filaments  of
origin of the vagus nerve to the tubercula quadrigemina, the former
only inclusive.   Destruction  of this  portion, in whole  or in part,
invariably impairs or destroys the respiratory actions, and a morbid
state of it gives rise to irregular or excited movements of respiration.
Sighing,  yawning, coughing, are probably connected with  excitation
of this centre,  either direct,  or  propagated to it from some  sentient
surface.
  This portion  of the encephalon is also  the centre  of action in the
movements  of  deglutition, through  fibres of the glosso-pharyngeal
and vagi nerves.  A morbid  state of it occasions difficulty, or even
paralysis, of deglutition.   Animals  deprived of the cerebral hemi-
spheres and cerebellum will preserve the power of swallowing food
introduced within  the grasp  of the fauces, so  long as the  medulla
oblongata continues  uninjured.  In foetuses born without cerebral
hemispheres, those  actions are present which depend on the spinal
cord and medulla oblongata; all the movements of respiration and
deglutition are  performed as well as in the perfect foetus.   Mr. Grain-
ger's experiments  show that puppies deprived of the hemispheres of
the brain can perform the movements  of suction with considerable
vigour, when  the  finger  is introduced  into the mouth, (loc. cit.,
pp. 80-1,) and the remarkable fact of the adhesion of the foetus  of
the kangaroo to the nipple within the pouch, no less than its respira-
tory movements, must, as  this author remarks, be regarded as a  most
interesting display of the physical power of the medulla oblongata,
while the rest of the brain is as yet undeveloped.
  The actions of respiration and deglutition are, to a great extent, of
the physical kind, being excited by impressions propagated from the
periphery.   In  those of respiration, the  ordinary exciting cause  is
probably, as Dr. Hall supposes, due to the chemical  changes in the
respired  air which are effected in the lungs.   These movements may
be, to a certain extent,  controlled by the  will; but every  one is con-
scious, from his own sensations, that after a time the physical stimulus
is capable  of conquering  the restraining influence of the mind; a
striking example of  a mental stimulus giving way to a physical one;
and illustrative, as we think, of the doctrine that the same fibres are
affected by both stimuli.  The  excitation of the  medulla oblongata in
respiration does  not, however, depend  solely  upon the pulmonary 
FUNCTIONS OF THE ENCEPHALON.
307
nerves.   Those of the skin are capable of exciting it,  either directly
as the fifth pair, or through the  spinal cord, as  is proved by the in-
spirations which are instantly excited by suddenly dashing cold water
on the face or trunk.
  In deglutition, the exciting cause is the stimulus of contact applied
to the mucous membrane of the fauces.   So highly sensitive  is  the
mucous membrane in  this situation, that the slightest touch of  it  with
a feather is sufficient to produce contraction of the muscles of deglu-
tition, which the will is scarcely able to control.   Without this stimu-
lus, it is doubtful whether these  muscles would  obey the will  alone ;
and it seems probable that this part of the act of deglutition must be
regarded as one of those  actions referred to at a former page, which
require  a double stimulus, both mental  and  physical, for their  full
performance.  (See p. 296.)
   The medulla oblongata and its  continuations  in  the mesocephale
appear  to be the centre of those actions which are influenced by
emotion.  The common excitement of movements of deglutition or
respiration, or of sensations referred to the throat, under the influence
of emotion, evidently points to this part  of the cerebro-spinal centre
as being very prone to obey such impulses ; and as the  nerves of pure
sense, especially the  optic and auditory, are  very  commonly the
channels  of sensitive  impressions well calculated to arouse  the  feel-
ings,  it  seems highly probable that the centre of such  actions  should
be contiguous to the origin of these nerves.   We would assign this
office to that region of the mesocephale which is in the vicinity of the
quadrigeminal tubercles.  It is not a little remarkable that the  nerves
which arise  from  this  and the  neighbouring parts are very readily
influenced by emotions.   Thus, the  third and fourth pairs of  nerves
regulate the  principal movements  of the eyeballs, those especially
which most quickly betray emotional excitement; and the portio  dura
of the seventh pair, the  motor  nerve of the face, is the  medium
through which changes of the countenance are  effected.  It may be
added, that  the centre of emotional  actions ought  to be so situated
that it could readily communicate with the centres  of all the  volun-
tary actions of the body, and with  the  immediate seat  of the in-
tellectual operations, as well  as with the  nerves of pure sense ; and
no part possesses these relations so  completely as that to which we
refer.
   In  those diseases which mental emotion is apt  to give rise  to, many
of the symptoms are referable to affection of the  medulla  oblongata.
In hysteria, the globus, or peculiar sense of suffocation or constriction
about the fauces; in chorea, the difficulty of deglutition, the peculiar
movement of the tongue, the  excited state of the  countenance, the
difficulty of articulation, may be attributed to the exalted polarity of
the centre of emotional actions.  In hydrophobia this part is probably
always affected, and frequently so in tetanus.
   Certain  gangliform  bodies  are  connected with  the upward  con-
tinuations of the  medulla oblongata, both  in the brain and  in  the
mesocephale, which doubtless have proper functions.   These are the
corpora striata, optic thalami, and quadrigeminal bodies. 
308
INNERVATION.
   Corpora striata.—The  anatomy  of  the corpora striata and  optic
thalami, while it  denotes a very intimate  union between  them, also
shows so  manifest a difference in their structural characters, that it
cannot be doubted that  they perform  essentially different functions.
In the corpora striata the fibrous matter is arranged in distinct fascicles
of very different size, many, if not all of which, form a special con-
nection  with its vesicular matter.   In the optic  thalami, on the  other
hand, the  fibrous matter forms a very intricate interlacement, which is
equally complicated at every part.  Innumerable fibres pass from one
to the other, and both are connected to the hemispheres  by extensive
radiations of fibrous matter.   The corpora striata, however, are con-
nected chiefly, if not solely, with the inferior fibrous layer of each
crus cerebri; whilst the optic thalami are continuous with the superior
part of each crus, which is situate above the locus niger.
   It  will  be observed, then, that while  these  bodies possess, as a
principal character in common, their extensive  connection  with the
cerebral hemispheres, or, in other words, with the convoluted surface
of the brain, they are, in  the  most  marked way, connected inferiorly
with  separate and distinct portions of the medulla  oblongata; the
corpora striata with the  inferior fibrous planes  of the  crura cerebri
and their  continuations, the anterior pyramids; and the optic thalami
with the olivary columns, the central and probably fundamental por-
tions of the  medulla oblongata.   And this  anatomical  fact must be
taken as an additional proof of  their possessing separate functions.
   Now, it may be inferred, from their connections with nerves chiefly
of a sensitive kind, that the olivary columns, and the optic thalami,
which are continuous with  them, are chiefly concerned in the recep-
tion of sensitive impressions, which may principally  have reference
merely to  informing the mind (so to speak), or partly to the excitation
of motion, as in deglutition, respiration, &c.  The posterior horns of
the gray matter of the cord, either  by  their direct continuity with the
olivary columns, or their union with them through commissural fibres,
become part and  parcel of a great centre of sensation, whether  for
mental or physical actions.
   The pyramidal  bodies evidently connect the  gray matter of the
cord  (its anterior horns?)  with the corpora striata; and not only these,
but also the intervening masses  of vesicular matter,  such as the  locus
niger, and the vesicular  matter  of the pons, and of the olivary col-
umns; and, supposing  the corpora striata to be centres  of volition
in  intimate connection with  the convoluted  surface  of the brain by
their numerous radiations, all these several parts  are  linked together
for the  common purposes  of volition, and constitute a great centre
of  voluntary actions, amenable  to  the  influence of the  will at  every
point.
   It has been pretty generally admitted by anatomists, that both  the
corpora striata and the  anterior pyramids are concerned in voluntary
movements.   The motor  tracts of Bell  were regarded by that phy-
siologist as passing upwards from the anterior columns of the cord to
the corpora striata, and, after traversing those bodies, as diverging
into the fibrous matter of the hemispheres; and the  fact of the origin 
     FUNCTIONS OF CORPORA STRIATA AND OPTIC THALAMI.    309

of certain  motor nerves, in  connection with those fibres, was con-
sidered to be very favourable  to this view.  The decussation  of the
pyramids, likewise, so illustrative of the cross influence of the brain
in lesions sufficient to produce paralysis, has been looked  upon as an
additional indication of the motor influence of these parts.
   The invariable occurrence of paralysis as the result of lesion, even
of slight amount, in the corpora striata, must be regarded as  a fact
of strong import in reference to the motor functions of these bodies.
   Nor is this fact at all incompatible with the statements made by all
experimenters, that simple section  of the corpus striatum does not
occasion either marked paralysis or convulsion ;  and that in cutting
away the different segments  of the brain, beginning  with the hemi-
spheres,  convulsions are not excited  until the region  of the mesoce-
phale is involved.  The influence of  the corpora striata is not upon
the nerves directly, but upon the segments of the medulla oblongata
or of the spinal cord, and, through them, upon the nerves which arise
from  them.  Were the  nerve-fibres  continued up  into the corpora
striata, according to an opinion which has been long prevalent, there
would be no good reason for supposing that they should lose  in the
brain that excitability to physical stimuli which  they are known  to
possess in the spinal cord, and at their peripheral distribution.
   The latest experiments, which are  those of Longet and Lafargue,
agree  in  the  following  result, which is  not  at  variance with that
obtained  by Flourens.   The  animals remain immovable after the
removal  of  the corpora  striata, whether those bodies have been re-
moved alone or in conjunction with  the hemispheres; nor do  they
show any disposition to move, unless strongly excited by some exter-
nal stimulus.   None  of these observers had noticed the  irresistible
tendency  to rapid  propulsion, which was described by  Magen'die.
Removal of the  corpus striatum  of  one side caused  weakness  of
the opposite side.
   In order  to form a  due  estimate of these experiments, it must  be
borne in mind, that the  effect  of simple  excision of either  corpus
striatum would be very different from those of diseases  of it.  The
depressing  effects of the latter would be  absent, at least, until some
alteration in the process of nutrition had been  set up in the mutilated
parts.  Simple  excision of the  centre of volition, and inflammatory
diseases of its substance, or an apoplectic  clot, must produce essen-
tially different effects;—the  one  simply cuts off  the  influence  of
the will, the other affects the  vital  action,  and,  consequently, the
 vital power of the centre, and of the commissural fibres connected
 with it.
   Judging from structure only, it might be conjectured that the locus
niger, that  remarkable mass of vesicular matter which separates the
 anterior and posterior  planes of  each crus cerebri, exerts  a motor  in-
fluence.  It resembles in structure the anterior horns of the gray matter
of the cord, and contains numerous large caudate vesicles with very
abundant pigment.
    Optic thalami.—The same line of argument which  leads us to
view the corpora striata as the more essential parts of the nervous 
310
INNERVATION.
apparatus which  control direct  voluntary movements, suggests that
the optic thalami may  be viewed as the principal foci of sensibility,
without which the mind could not perceive the  physical  change re-
sulting from a sensitive impression.
   The principal anatomical fact which favours this conclusion, is the
connection of all the nerves of pure sense, more  or less directly,  with
the optic thalami or with the olivary  columns.    The olfactory pro-
cesses,  which apparently have  no  connection with them, form, no
doubt, through the fornix, such a union with them, as readily to bring
them within the influence of the olfactory nerves.
   According to this sense of its  office, we must regard the  optic
thalami as the upper and  chief portions of an  extended  centre, of
which the  lower part is formed by the  olivary columns, which we
have already referred to as taking part in the mechanism of sensation.
The continuity of the olivary columns with the optic thalami justifies
this  view:  nor is it invalidated by the  fact, that  some of the nerves
which arise from the medulla oblongata are motor in function ; for
Stilling's researches render it probable  that these fibres  have  their
origin  in special accumulations of  vesicular  matter, which contain
caudate vesicles of the same kind as  those found in the anterior horns
of the gray matter of the cord.  (See fig. 70.)
   The results which experiments have yielded, add little that is posi-
tive  to  our  knowledge of the functions of these  bodies.  Flourens
found that neither pricking nor cutting away the optic thalami by  suc-
cessive slices, occasioned any muscular agitation, nor did it even in-
duce contraction of the pupils.  Longet found that removal of one
optic thalamus in the rabbit was followed by paralysis on the oppo-
site side of the body.   It appears, however, that this was done after
the removal  of the  hemisphere and corpus striatum,  whereby the
experiment was so complicated  as to invalidate  any conclusion  that
might be drawn from it respecting the  function of the thalamus.  In-
deed, vivisections upon so complex an organ as  the brain are ill cal-
culated to lead to useful or satisfactory results ; but we do not hesi-
tate to quote such as have  been  made, from the  imperfect negative
information which they afford.
   Nothing definitive respecting  the proper office of  the  thalami can
be obtained from pathological anatomy.  Extensive  disease of these
bodies is attended with the same phenomena during life, as lesion of
similar kind in the corpora striata.   Hemiplegic  paralysis accompa-
nies  both; nor does  it appear that  sensation  is  impaired when the
thalamus is diseased, more than when the corpus striatum is affected.
   We see nothing in the phenomena which attend morbid states of
the thalami, to oppose the conclusion  which  their anatomical  rela-
tions indicate, namely, that they form  a principal  part of the centre
of sensation.   The intimate connection between the striated bodies
and the thalami, sufficiently explains the paralysis of  motion which
follows disease of the latter ;  whilst, as the thalami do not constitute
the whole centre of sensation, but only  a part,  it  cannot be expected
that  lesion  of this part would destroy sensation, so  long as the re-
mainder of the centre on the same side, as  well as that of the  oppo- 
FUNCTIONS OF THE ENCEPHALON.
311
site side, retain their  integrity.  Complete paralysis of sensation on
one side is very rare in diseased brain : a slight impairment of it fre-
quently exists in the  early periods  of cerebral  lesion, apparently as
an effect of shock ; for it quickly subsides, although the motor power
may never return.
  According to the views  above expressed, the corpora  striata and
optic thalami bear to  each  other a relation analogous  to  that of the
anterior to the posterior horn of the spinal gray matter.  The corpora
striata and anterior horns  are centres of motion ;  the optic thalami
and posterior horns centres of sensation.   The anterior pyramids con-
nect the former; the  olivary columns, and perhaps some fibres of the
anterior pyramids, the latter.   The olivary columns, however, are in
great part continuations of the thalami on the one hand, and of the
gray matter of the cord on the other:  and contain  abundance of ve-
sicular matter, in which nerves are implanted.
   And it must be admitted that the  intimate connection of sensation
and motion, whereby sensation becomes a frequent  excitor of motion,
—and voluntary motion is always, in  a state of  health, attended with
sensation,—would a priori lead us to look for the  respective centres
of  these two great faculties, not only in juxtaposition, but in union
at least as intimate as that which exists between the  corpus striatum
and optic thalamus, or between the anterior and  the posterior horns of
the spinal gray matter.
   Saucerotte, Foville, Pinal Grandchamps, and others, advanced the
opinion that the corpora striata and the fibrous substance of the an-
terior lobes of the brain had a special influence upon the motions of
the lower extremities, and that the optic thalami and the fibrous sub-
 stance of the middle  and posterior part of the brain presided over the
 movements of the upper  extremities.  We  find, however, but little
 to  favour this theory either in the results of experiments, in patho-
 logical observation, or the anatomy of the parts.  Longet states, that,
 in  his experiments  upon  the optic thalami, the  paralysis affected
 equally the anterior and the posterior  extremities.  Andral analyzed
 seventy-five cases of cerebral  lesion limited to the  corpus striatum or
 optic  thalamus.   In  twenty-three  of these  cases, the paralysis was
 confined to the  upper extremity:  of these, eleven were affected with
 lesion of the corpus striatum or of the anterior  lobe ;  ten with lesion
 of the posterior lobe, or of the optic  thalamus; and  two with lesion
 of the middle lobe.*   Hence it is plain, that  a  diseased  state of the
 corpus striatum is as  apt to induce  paralysis of  the upper extremity,
 as lesion of the thalamus ;  and we are forced to conclude, that patho-
 logical anatomy is not competent to decide the question.  Lastly, the
 anatomy of these two bodies renders it highly  improbable that they
 perform a function so similar, as that  of directing  the movements of
 particular limbs.  The great size of the optic thalamus, its multitude
 of fibrous radiations, its extensive  connections both  in  the medulla
 oblongata and in  the hemispheres by means of commissural fibres,
Clin. Med. t. v. 
312
INNERVATION.
the marked difference of its structure from that of the corpus striatum,
its connection more with the posterior horns of the spinal gray matter
than with the anterior  ones, and  its intimate relation to nerves of
sensation, are, in our judgment, sufficient anatomical facts to warrant
the opinion that the thalami must perform a function which, although
it may be subservient to, or associated with, that of the striated bo-
dies, is yet entirely dissimilar in kind.
  It has  been supposed that the corpora striata are special centres or
ganglia to the olfactory  nerves, and to the sense of smell.  But such
a supposition is  altogether superfluous, inasmuch as  a very distinct
and obvious centre to these nerves exists in the olfactory process or
lobe, miscalled nerve by descriptive  anatomists.   The small olfactory
nerves are implanted  in the anterior  extremity or bulb  of this pro-
cess, which is provided with all the structural  characters of a nervous
centre, and  contains  a ventricle.   This lobe,  moreover, is  always
developed in the direct ratio of the  size and number of the olfactory
nerves, and of the development of the sense  of smell; and in the
Cetaeea,  a class in which the olfactory nerves and process  either do
not exist at all, or are so imperfectly developed  as  to  have escaped
the notice of some of the  ablest anatomists, the  corpora striata are
of good size proportionally to that of the entire  brain.
   Corpora quadrigemina.—The marked connection  of these  gangli-
form bodies with the optic nerves  plainly indicates  that  they bear
some special  relation to those nerves, and to the sense of vision ; and
this indication becomes more certain when we  learn, from  compara-
tive anatomy, that in all vertebrate tribes in which the encephalon is
developed, special lobes exist,  bearing a similar relation to the optic
nerves (pp. 249-50).  When the optic nerves are large, these lobes are
large;  and in the pleuronecta, in which the eyes are of unequal size,
Gottsche states that the optic lobes are  unequal.   Still, as Serres has
remarked, the quadrigeminal tubercles probably perform  some other
office besides that which refers to vision; inasmuch as the absence,
or extremely  diminutive size, of the. optic nerves  in  some animals
(the  mole, for instance), does not  materially affect that of these bo-
dies.   (Cyclop. Anat., art.  Optic nerves.)
  Flourens found that destruction  of either of these tubercles on one
side  was followed by loss  of sight of  the  opposite  side, and  conse-
quently that the removal of both  deprived the  animal  altogether of
the power of vision, but did not affect its  locomotive or intellectual
powers, nor its sensibility, except to light.  In these experiments the
action  of the iris was not  impaired if the  tubercles were  only par-
tially removed ; as long  as any portion  of  the  roots of the  optic
nerves remained uninjured, the iris continued to  respond to the  stimu-
lus of light, but the total removal of the tubercles paralyzed the irides.
If the lobes of the brain and cerebellum were removed, leaving the
tubercles  untouched,  the irides would  continue to contract.   These
experiments leave no room to doubt that the optic  tubercles  are the
encephalic recipients of the impressions necessary to vision, which
doubtless are simultaneously felt by means of the optic thalami; and 
           FUNCTIONS OF THE CORPORA QUADRIGEMINA.       313

that they are the centres of those  movements of the  iris which con-
tribute largely not only to protect the retina, but  likewise to increase
the perfection of vision.  The optic  nerve is at once  the nerve of
vision, and the excitor of motor impulses which are conveyed to  the
iris by the third nerve, which takes  its origin very near to the optic
tubercles.   It is interesting to add, that irritation of an optic tubercle
on  one side causes contraction of both irides:—this is quite in accord-
ance with  the well-established fact, that, if light be  admitted to  one
eye so as to cause contraction of its pupil, the other  pupil will con-
tract at the same time.  So simultaneous is the action of the two
centres ; so rapid must be  the transmission of the stimulus from  one
side to the other.
   When the injuries inflicted on these tubercles were deep, more or
less general convulsive movements were produced ;  if one tubercle
were injured, the opposite side only was so affected.   These con-
vulsions were due  to the  lesion of  the central  parts of the medulla
oblongata, with which the  optic tubercles are intimately connected.
A remarkable vertiginous movement was likewise caused, the animal
turning to the side from which the tubercle had been removed.   It
does not appear that this rotation  could be attributed to any special
influence of the medulla oblongata, but rather to a state of vertigo
induced by the partial destruction of vision ;  for Flourens found that
the same effects could be produced  in pigeons by blindfolding one
eye.  The  movements,  however, were  not  so rapid, nor did they
continue so long.   And Longet saw the same movements in pigeons
in which he had evacuated the humours of one eye.*
  It may be remarked, that deep injuries to the quadrigeminal tuber-
cles are very likely to affect the only commissural connection between
the  cerebrum and  cerebellum (processus cerebelli ad  testes), the  in-
tegrity of which must doubtless be  essentially necessary to ensure
harmony of action between these two great nervous centres.
  There are many instances on record in which blindness was coin-
cident with pathological alteration  of structure in one  or both quadri-
geminal  tubercles.   In some of the cases where the lesion extended
to parts seated  beneath the tubercles, disturbed movements were ob-
served, as in the experiments above related.
  We are  ignorant  of the object of the extensive connections of  the
optic tracts with the tuber  cinereum, the  crura cerebri,  and the cor-
pora geniculata; but  these  points are highly worthy of future inquiry,
especially  with  reference to  the office of these last-named bodies,
which is at present involved  in much obscurity.   Many of  the fibres
of the optic tracts are undoubtedly commissural between the corre-
sponding  points of opposite sides, and exist when those which form
the optic nerves are deficient.
  We see, then, in  the quadrigeminal tubercles,  centres,  which,
whatever  other  functions they may perform,  have a  sufficiently ob-
vious relation to the  optic  nerves, the eye, and  the sense of vision.

  * Flourens' experiments have  been amply confirmed by those of Hertwig and
Longet.
21 
314
INNERVATION.
This is clearly indicated by anatomical facts, by the results of experi-
ment, and  by the phenomena of disease.   These bodies may, there-
fore, be justly reckoned as special ganglia of vision;  and we are led
to seek for similar centres in connection with the other senses.   The
olfactory processes seem  very probably to perform  a similar office in
reference to the sense of smell.   Their structure, their relation to the
olfactory nerves, and their direct proportion of bulk to that of these
nerves,  and to  the development  of the  olfactory apparatus,  place
this question  beyond all doubt.  It is not so easy to determine the
special  ganglia  of hearing;  but the  olivary  bodies,  or the  small
lobules connected with the crura  cerebelli, called  by Reil the flocks,
may be referred  to as bearing a sufficient close anatomical relation to
the. auditory nerve to justify our regarding either of them as well cal-
culated  to perform this function.   And, with respect  o touch, the
ganglia  on the posterior roots of the spinal and the fifth nerves may
perhaps be considered in the same light;  for this sense being diffused
so universally,  in various degrees, over  the whole surface of  the
body, and  being seated in a great number of different nerves, would
need ganglia in connection with all those nerves  which are adapted
to the reception of tactile impressions.  The analogous sense of taste
has its ganglia in those of the glosso-pharyngeal and the fifth.*
   The upper and posterior part of the mesocephale has already been
referred  to, as being  most probably that part of  the  brain which is
most directly influenced  by emotional excitement.   Dr. Carpenter
appears to localize the seat of  emotional  influence more  specially in
the corpora quadrigemina, and  refers to certain fibres, which he con-
siders terminate in those bodies, as channels of emotional  impulses.
Although we cannot agree with this able  writer in this limitation of
the centre of emotion (so to speak), nor in the existence of a distinct
series of fibres  for emotional  acts, we think the  arguments he  ad-
vances  are most applicable to that view which refers the  influence of
emotion to  the  gray matter of this entire region, which  s brought
into connection   with the  spinal cord by the fibres of the anterior
pyramids,  as  well as  probably through the continuity of the olivary
columns and the  posterior horns of the spinal gray matter.
   Every one has experienced in his own  person how the emotions of
the  mind, whether excited by  a passing thought, or through the ex-
ternal senses, may occasion  not  only involuntary movements, but
 subjective sensations.   The thrill which  is felt throughout the entire
 frame when  a feeling of horror or  of  joy is excited, or the involun-
tary shudder which the idea of imminent danger or of some serious
hazard gives rise to, are phenomena of sensation and motion excited
by emotion.  The  nerves which take their origin from the medulla

   * It may be urged against this conjecture respecting the functions of the ganglia
 of the spinal nerves and the fifth, that the analogy between these bodies  and the
 quadrigeminal  tubercles is incomplete, inasmuch as the optic nerves are probably
 implanted in the latter, but the nerves of touch merely pass through the  former.  But,
 in truth, we know so little of the positive  relation of the nerves in question to the
 ganglia, that no argument, either for or against the above view, can  rest upon such
 imperfect information. 
FUNCTIONS OF THE ENCEPHALON.             315
oblongata,  mesocephale, or crura  cerebri, are especially apt to  be
affected by emotions.   The choking sensation  which accompanies
grief is entirely referable to the pharyngeal branches of  the glosso-
pharyngeal and vagi  nerves, which  come from the olivary columns.
The flow of tears which the sudden occurrence of joy or  sorrow is
apt to induce may be attributed to  the influence of the  fifth nerve,
which  is also implanted in the  olivary columns, upon the lachrymal
gland ; or of the fourth  nerve, which anastomoses with the lachrymal
branch of the fifth.   The more  violent expressions of grief, sobbing,
crying, denote an excited state of the whole centre of emotion,  in-
volving all the nerves which have connection with it, the portio dura,
the fifth, the vagus, and glosso-pharyngeal; and  even the respiratory
nerves, which take their origin  from  the spinal cord, as the phrenic",
spinal  accessory,  &c.  And  laughter, "holding  both his sides,"
causes an analogous excitation of the same parts of the central organ
and of the  same nerves.  The very  different  effect produced by the
excitement of the  same parts  must be attributed to the different
nature of the mental stimulus.
   As the passing  thought—the  change wrought during the exercise
of the intellect—may excite the centre of  emotion, so this latter
may exert its influence upon the general tenor of the mind, and give
to all our thoughts the tinge of mirth  or sadness,  of hope or despond-
ency, as one or the other may prevail.  We say of one man, that
he  is constitutionally  morose ; of a second, that he is naturally gay
and mirthful;  and of a third, that he is a nervous man, and that  he
is not likely to be otherwise.  One man allows his feelings to  hurry
him on to actions which his intellect  condemns; whilst another has
no difficulty in keeping all  his  feelings in entire  subjection to his
judgment.   " Of two  individuals with differently constituted minds,"
remarks Dr. Carpenter,  "one shall judge of  everything through the
medium of a gloomy morose temper, which, like a darkened  glass,
represents to his judgment  the whole world in league to injure him  ;
and  all his determinations, being based upon  this erroneous  view,
exhibit the indications of  it in his  actions,  which are themselves,
nevertheless, of an  entirely voluntary character.  On the other hand,
a person of a cheerful, benevolent  disposition,  looks  at the  world
around as through a Claude-Lorraine glass, seeing everything in  its
brightest and  sunniest  aspect, and,  with  intellectual faculties pre-
cisely  similar to those of the former individual, he will come to oppo-
site conclusions;  because the materials which form the basis of  his
judgment are  submitted to it in a very different form."    Such ex-
amples abundantly illustrate the  important share which the emotions
take in  the formation and  development of  character, and how  all
things presented to the mind through the senses may take their hue
from  the prevailing state of the feelings.   If a certain  part of the
brain be associated with emotion, it is plain that  that part must be in
intimate  connection with the seat of  change in the operations of the
intellect, in order that  each may affect the other;  that  the  former
may prompt the  latter, or the  latter excite  or  hold in  check  the
former.  And  this association of the emotions with a certain portion 
316
INNERVATION.
 of the  brain explains the influence of natural temperament, and of
 varying states of the physical health, upon the moral and intellectual
 condition of individuals.  We may gather from  it how necessary it
 is to a well-regulated mind that we should attend not to mental cul-
 ture  only, but  to  the vigour and  health of the body also; that to
 ensure  the full development of the mens sana we  must  secure  the
 possession of the corpus sanum.
   Certain diseases are evidently associated with disturbed or excited
 states of emotion.   In such cases, the nerves most affected are those
 connected with  the mesocephale and medulla oblongata, denoting an
 excited state of those portions of the encephalon.   Of these diseases
 the most remarkable are hysteria  and chorea;  both of  which may be
 induced either  by a cause acting  primarily upon  the mind, or by
 functional  disturbance of the body, as deranged assimilation, in per-
 sons of a certain character of constitution.  In hysteria, the globus,
 the  tendency to cry or  laugh, the disturbed breathing, the variously
 deranged state  of the respiratory  acts, all denote affection of  most, if
 not  all,  the  nerves coming from those segments.   In chorea the
 frequent movements of the  face and eyes, the peculiar and very
 characteristic mode of protruding the tongue, the impaired power of
 articulation, are dependent on an altered state of that  part in which
 the portio dura of the seventh pair, the third, fourth, and sixth, and
 the  ninth  nerves  are implanted.  In  both diseases  the principal
 central disturbance  is  in the mesocephale; and  that  may be caused
 either by the direct influence of the mind upon it, or by the propaga-
 tion of a state of irritation to it  from some part of the periphery.
 Chorea, even of the most violent and general kind, is  very  com-
 monly produced by Sudden fright; and it  is well known how fre-
 quently  mental  anxiety  or excitement develops  the  paroxysm of
 hysteria.
   There is no  part of the cerebro-spinal  centre which appears to
 exercise such extensive sway over the movements and  sensations of
 the body as this portion, the  mesocephale,  which we  regard  as the
 centre of emotional  actions.   Its influence  extends  upwards to the
 cerebral convolutions—backwards to the cerebellum—downwards to
 all the nerves of sensation and motion.  Through its connection with
 the posterior horns of the spinal gray matter, it can excite the sensi-
 tive as well as the motor nerves of the trunk.   Hence it is not to be
 wondered at  that a highly disturbed state of this centre is capable of
 deranging all the sensitive as well as motor phenomena of the body,
 and  even  the  intellect.  Hence  we may  explain the extraordinary
 movements  in  hydrophobia and  general  chorea, in  both of which
 diseases this part of the nervous centre is doubtless affected.   It has
 often  been remarked how much more powerful are  the voluntary
 actions when prompted by some strong emotion, than when excited
only by  an effort of  the will.   Rage, or despair, is able to magnify
the power of the muscles to  an  incalculable degree.   This maybe
due to the increased stimulus derived from the influence of the centre
of emotion being conjoined with that of the centre of volition.
  The intimate  connection of the  olivary  columns  with the gray 
FUNCTIONS OF THE CEREBELLUM.
317
matter of the cord, and through that with all the roots of the spinal
nerves, illustrates the power of emotional changes upon the organic
processes.   How often does the state of the feelings  influence the
quantity and quality of the  secretions, no doubt  through the power
of the nerves over the capillary circulation!  Blushing is produced
through an  affection of the  mind, acting  primarily on  the  centre of
emotion, and through  it  on  the nerves, which are distributed to the
capillary vessels of the skin of the face.
   The sexual passion  must  be ranked among  the mental emotions.
Like  them,  it may be excited and  ministered to by a certain line of
thought, or  by particular physical states  of the sexual organs.  It
seems, therefore, more correct to refer this  emotion to the common
centre of all, than to a special organ—according to Gall's theory;
and  it may be remarked, that great development of this part of the
brain is just as likely to produce great width of cranium in the  occi-
pital region  as a large  cerebellum.
   Of the functions of  the cerebellum.—All anatomists  are agreed in
admitting, in the whole vertebrate series,  (the amphioxus excepted,)
the existence of a  portion of the encephalon which is analogous to
the cerebellum.  This  extensive existence of such an organ indicates
its great  physiological  importance, as a special  element of the ence-
phalon.  The cerebellum exhibits much  difference both as regards
size  and complexity of  structure  in  the  different classes;  and al-
though, upon the whole, it increases in its development in the  same
ratio as the hemispheric lobes, it exhibits no constant relation of size
to those parts.
   The large size  and complicated  structure of  this  organ  in the
higher vertebrate animals, and its distinctness from the  other parts of
the brain,—for its  commissural connections are not extensive,—have
excited the  interest and  curiosity of speculative physiologists;  and,
accordingly, we find  no  part  respecting which a greater variety of
hypotheses have been suggested, most of them being entirely devoid
of foundation.  The  experiments of Flourens have, however, thrown
more light  on this subject than  any previous observations;  and his
hypothesis appears to  us nearer the truth than any which has  been
proposed.   We shall content ourselves with examining this theory,
as well as that of Gall, which  assigns the  cerebellum as the organ of
the sexual instinct.
   The facility with which the  cerebellum may be  removed or in-
jured, especially in birds, without involving the  other segments of
the brain, renders it a  much more favourable object for direct expe-
riment than them.  A skilful  operator may remove the greater part
or the whole of the  cerebellum  without inflicting any injury on the
hemispheres or other parts.
   Flourens  removed the cerebellum from pigeons by successive slices.
During the  removal of the  superficial layers tfiere appeared only a
slight feebleness and  want of harmony in the movements, without
any expression of  pain.   On reaching the middle  layers an almost
universal  agitation was manifested, without any sign of convulsion:
the animal performed  rapid and ill-regulated movements;  it  could 
318
INNERVATION.
hear and' see.  After the removal of the deepest layers, the animal
lost  completely the  power of standing, walking, leaping, or flying.
The power had been injured by the previous mutilations, but now it
was completely gone.  When placed  upon  his back, he was unable
to rise.   He did  not, however, remain  quiet  and  motionless, as
pigeons  deprived of the  cerebral hemispheres do; but evinced an
incessant restlessness, and  an inability to accomplish any regular or
definite movement.   He  could  see the instrument raised to threaten
him with a blow, and would make a thousand contortions to avoid it,
but did not escape.   Volition and sensation remained ; the power of
executing movements remained ; but that of co-ordinating these move-
ments into regular and combined actions  was lost.
   Animals deprived of the cerebellum are in a condition very similar
to that of a drunken man, so far as relates to their power of locomo-
tion.   They are unable  to  produce that combination of action in
different sets of muscles which is necessary to enable them to assume
or maintain any attitudes.   They cannot  stand still for a moment;
and, in attempting  to walk, their gait is unsteady, they totter from
side to side, and their progress is interrupted by frequent falls.   The
fruitless attempts which they make to stand or walk is sufficient proof
that a certain  degree of intelligence  remains,  and that  voluntary
power continues to be enjoyed.
   Rolando had, previously to Flourens, observed effects of a similar
nature consequent upon  mutilation of the  cerebellum.  In  none of
his experiments was sensibility affected.  The animal could see,  but
was unable to execute  any of the movements  necessary for loco-
motion.
   Flourens' experiments  have been confirmed by those of Hertwig
in every particular, and they have been lately repeated  with similar
results by Budge and by  Longet.   The removal of  part of the cere-
bellum  appears capable of producing the same vertiginous affection
which has  been already  noticed in the case of deep injuries to the
mesocephale.  After  the well-known  experiments  of Magendie, of
dividing either crus cerebelli, the animal  was seen to roll over on its
long axis towards the side on which the injury was  inflicted.
   The effects of injuries to the cerebellum, according to the reports of
the experimenters above  referred to, contrast in a very striking man-
ner with those of the much more severe operation  of removing  the
cerebral hemispheres.  " Take two pigeons," says M. Longet; " from
one remove completely the cerebral lobes,  and from the other only
half the cerebellum; the  next day,  the first will be firm upon  his
feet, the second will exhibit the unsteady and uncertain gait of drunk-
enness."
   Experiment,  then, appears strikingly to favour the  conclusion
which Flourens  has drawn,  namely, that the cerebellum possesses
the power of co-ordinating the voluntary  movements which originate
in other parts of the  cerebro-spinal centre, whether these movements
have reference to locomotion or to other objects.
   That  this power is mental, i. e., dependent on a mental operation
for its excitation and  exercise, is rendered probable from the  expe- 
FUNCTIONS OF THE CEREBELLUM.
319
rience of our own sensations, and from the fact that the perfection of
it requires practice.  The voluntary movements of a new-born infant,
although perfectly controllable by the will, are far from being co-ordi-
nate: they are, on the contrary, remarkable for their vagueness and
want of definition.   Yet all the parts of the cerebro-spinal centre are
well developed, except  the cerebellum and  the convolutions of the
cerebrum.   Now, the power  of co-ordination improves  earlier  and
more rapidly than the intellectual  faculties; and  we find, in accord-
ance with Flourens' theory, that  the cerebellum reaches its perfect
development of form and structure at a much  earlier period than the
hemispheres of the cerebrum.
   It may be stated  as favourable to this view of the mental nature
of the power by  which voluntary movements  are co-ordinated, that,
in the first moments of  life, provision is made for  the  perfect  per-
formance of all those  acts which are of the physical kind.  Thus,
respiration and deglutition are as perfect in the new-born infant as
in the full-grown  man; and the excitability of the nervous centres to
physical impressions is much greater at the early age, partly perhaps
in consequence of the little interference which is  received at  that
period from the will.
   That the  cerebellum is an organ favourably disposed for regulating
and  co-ordinating all the voluntary movements of the frame, is very
apparent from  anatomical  facts.  No  other  part of the  encephalon
has  such extensive connections with the cerebro-spinal axis.   It is
connected  slightly  indeed with the hemispheres of the  brain, but
most extensively  with the mesocephale, the medulla oblongata, and
the spinal cord.   Now it is not unworthy of notice that its connection
with the brain  proper is more immediately with that part which we
regard as the centre of sensation ;  namely, with  the optic thalami,
through the processus cerebelli ad testes.  And it cannot be doubted
that  the muscular  sense materially assists in the  co-ordination of
movements.   •
   The  cerebellum is  connected with  the  medulla oblongata  and
spinal  cord by the  restiform bodies, and  the  posterior  columns of
the cord, and with the mesocephale by the fibres of the pons.  Thus
this  organ is brought into union with each segment of the great nerv-
ous  centre, upon  which all the movements  and sensations of the
body depend.   It would be difficult to conceive  any other function
for which so elaborate a  provision would  be necessary, excepting
that of regulating and co-ordinating the  infinitely complex move-
ments which the muscular system is capable of effecting;  more espe-
cially when it is plain that the antero-lateral columns of the cord and
the anterior pyramids and  olivary columns supply all the anatomical
conditions which  may be necessary for the development  of acts of
sensation  and volition.
   So far,  then, we derive from experiment  and from anatomy argu-
ments  highly favourable to Flourens' theory of the  use of the cere-
bellum.   The  results  of pathological  inquiry afford no  Satisfactory
information on this point; for so closely connected are the transverse
fibres of the pons with the anterior pyramids in the mesocephale, that 
320
INNERVATION.
the morbid influence of any deep-seated lesion of either hemisphere
of the cerebellum is very readily transferred to that  segment, and
produces  symptoms  precisely resembling  those  of  lesion  of  either
cerebral hemisphere.  The signs referable to cerebellar  lesion are
therefore obscured by those which result  from the affection of the
pyramidal bodies.  A few cases, however, have been put on record
in which a tottering gait, like that of a drunken man, and a defective
power of co-ordination existed in connection with a diseased state of
cerebellum.  (Andral, Clin. Med., t.  v. p. 428.)
   It remains for us to notice the celebrated  theory  of  Gall, that the
instinct of propagation has its seat in the cerebellum ; which, indeed,
according to the author of the theory, and the majority of his followers
of the phrenological  school, is exclusively devoted  to that function.
We conceive that this view is far from admissible, on several grounds,
of which the following deserve particular  mention.
   1. It is extremely questionable how far  the sexual instinct admits
of being separated from the emotions—from those  especially which
are clearly instinctive in  their nature ;  and, even if it were separable
from  them, it  seems  scarcely of such importance,  when compared
with the  other instincts,  as to need a separate organ of  great magni-
tude and of complex structure.  If we compare it, for example, with
the instinct  of self-preservation, as manifested in providing either for
the wants of the body, or for defence against assault, it certainly can-
not be admitted to have  a  superior  influence in the  animal economy
to this the most pressing of all.   Yet it is not pretended to assign a
separate seat even to this.
   2.  The nature of the generative  instinct is scarcely such as to re
quire in its central organ connections  so extensive as those possessed
by the cerebellum.   It is  not  likely that  this organ would  be con-
nected with any other part of the spinal cord  than  that from which
nerves are derived to the organs of generation; nor is it conceivable
that an instinct like this should require for its exercis^ fibrous matter
in such large quantity as exists in the cerebellum, taking its rise from
so great a surface of vesicular matter.
   3.  The generative instinct is  not  so pre-eminently developed in
man as to account for the  great superiority in size, as well as struc-
ture, of the human cerebellum over that of the lower animals, even
of the  mammiferous class.   On the contrary, it may be safely asserted
that this  instinct is much more powerful in the monkeys, and also in
the frogs; in the latter of which the  cerebellum is absolutely very
small, and especially so,  relatively to the spinal cord and the cerebral
lobes.
   4.  If the  cerebellum be  the seat of the generative instinct, it ought
to exhibit marked  indications of wasting,  in cases where  the genital
organs have been  mutilated ; or where  they have decayed in the
natural progress of  age.   Yet the recorded cases of this  nature are
by no  means conclusive;  on  the contrary, M. Leuret's remarkable
observations show, that, in the gelding, the  cerebellum is actually
heavier than in either the stallion or the mare.
   5.  It does not appear,  from pathological research, that the cerebel- 
          FUNCTIONS OF THE CEREBRAL CONVOLUTIONS.        321

lum has any peculiar  influence upon  the  genital organs.   Injury or
disease of that organ very rarely produces any effect upon  the penis;
but lesion of the medulla oblongata or of  the  spinal cord  is very apt
to occasion a semi-erection of that organ.
   Of the Convolutions of the brain.—These, with the fibrous matter
which connects them with the optic thalami and corpora striata,-form
by far the largest portion of the encephalon;  and this  fact alone
ought to stamp them with great physiological importance.  The com-
plexity of the convolutions in the animal  scale is in the  direct ratio
of the advance of intelligence.  It must be remarked, however, that
the weight of the brain, whether absolute, or in relation to the body,
affords  no criterion, or  at best an imperfect one, of the extent  of
the convoluted surface.  Highly complicated convolutions may exist
along with a brain both absolutely and relatively small.   Thus Leuret
asserts,  that the ferret, which has several  well-marked  convolutions
on each hemisphere,  has a brain no larger than that of the squirrel,
which  has no  convolutions  at all, and which wants even the  few
fissures  which mark their first development in the rabbit, the beaver,
the agouti, &c.   And the last-named animals have  the  brain both
absolutely and relatively larger than that of the cat, the pole-cat, the
roussette, the unau, the sloth, and the pangolin, all of which possess
convolutions.   We hence learn the physiological distinctness of these
organs from the more deeply-seated  gangliform bodies of the brain,
to which we have  already seen that separate functions may be
assigned.
   At the early periods of human life, in infancy and  childhood, the
convolutions of the brain are very imperfectly developed, and their
increase  of size  goes on simultaneously with the advance of mental
power.   If the former be arrested, or if some congenital fault prevent
the further growth of  the convolutions, the mental powers are of the
lowest and  feeblest  kind,  but little  above those of  the  brute with
imperfect convolutions.   In all idiots the brain is not only small, but
its convoluted surface is extremely limited.
   We  remark  here that the  convoluted form must be regarded no
otherwise than as a convenient mode of packing, which  affords an
indication of a greater or less superficial extent of  vesicular matter,
for in cases where a slow and gradual accumulation of water takes
place within the ventricles of the brain, when accompanied with  cor-
responding enlargement of the cranium,  the  convolutions become
unfolded; and yet the intellect  may remain  unimpaired,  at least so
far as the obvious damage to the quality of the nervous matter in
such cases will allow.
  In examining the brains  in  the animal series, we  observe  a pro-
gressive increase in the complication of the convolutions,  and  there-
fore  in  the  extent of the  convoluted surface, as we pass from the
inferior to the  higher classes,—from  those  endowed with  but  feeble
intelligence  to  those  which  enjoy sagacity, docility, and memory.
Instances have been already referred to of animals of the same group,
although of different species, having brains  very differently developed
as regards the convoluted surface.  In the animal with greater mental 
322
INNERVATION.
power, the convolutions are always deeper or more complex (vid. p.
256).
  If a similar comparison were instituted between the brains of dif-
ferent men, whose intellectual powers had been known, there can be
no doubt that a similar result would be obtained.   A series of outline
views of the  convolutions of the  brain in various known individuals
would be of great interest and advantage in reference to the question
of their function.
  Thus anatomy leads to  the  conclusion that the operations of  the
mind are associated  with the convolutions.   Perception,  memory,
the  power of abstraction, imagination, all possess, as instruments of
corporeal  action, these folds of vesicular and fibrous matter.  These
parts, in the language of Cuvier,  are the  sole receptacle in which  the
various sensations  may be as it were consummated, and become per-
ceptible to the animal.   It is in these that all sensations take a distinct
form, and leave lasting traces of their  impression;  they serve as a
seat to memory, a property by  means of which the animal is furnished
with materials for his judgments.*
  It is quite established as the result of all the experiments  upon  the
cerebral convolutions and the  white matter of the centrum ovale, that
mechanical injury to  them occasions no pain,  nor disturbance  of
motion.   The endowments of the nerve-fibres which form the fibrous
substance of the cerebral  convolutions  appear to be quite distinct
from  those of sensitive or motor nerves.  They are internuncial
between parts which are  beyond the  immediate influence of  the
ordinary physical agents, and  which have no direct connections with
muscular organs.  And if, under the influence of morbid irritation,
they do excite pain  or convulsion,  which is frequently the case in
disease of the  cerebral meninges, this is effected through  a change
produced in the corpora striata or optic  thalami  propagated to  the
origins of motor and sensitive  nerves.
  The recorded experiments upon the removal of the hemispheres of'
the  brain do not lead  to any satisfactory conclusion, as in all of them
the  corpora striata  and thalami have been removed at the  same time.
But it may be here stated, that the effect of the removal of the  hemi-
spheres in Flourens' experiments  was to throw the animal  into a state
of deep  sleep, retaining its full muscular  power, yet apparently  in-
capable of a  single  mental nervous  action, whether voluntary or
sensitive.
  When the membranes of the brain are in a state of inflammation,
disturbance of the  mental faculties  is an invariable  accompaniment
to an  extent proportional  to  the degree of cerebral irritation, and
more especially so when the  inflammation is seated in the pia  mater
of the convolutions.   This disturbance of mind is frequently  indicated
by the manifestation of delirium of a more or less violent kind.  It is
plain that in such a case the delirium arises from the altered state of
the circulation in the  gray matter of  the  convolutions, the blood-ves-
sels of which are immediately  derived  from those of the pia  mater, so
that the one cannot be affected without the other likewise suffering.
      * Cuvier, Rapport sur le me-moire de Flourens sur le systeme nerveux. 
          FUNCTIONS OF THE CEREBRAL CONVOLUTIONS.       323

And it may be stated, as a fact no less interesting in a physiological
than important in a practical point of view, that in many, if not in
most, instances  of violent delirium, such, for example,  as delirium
tremens, the vesicular matter of the convolutions is found after death
to be  bloodless, as if its wonted supply  of blood had been com-
pletely cut off from it.   Thus it happens in the delirium after great
operations—in that of rheumatic fever—and perhaps also of gout—
and in that which occurs in the more advanced stages of continued
fever.
   We learn from  the most trustworthy reports of  the dissections of
the brains of lunatics,  that there is  invariably found more or less
disease of the vesicular surface, and of the pia mater and arachnoid
in connection with it, denoted by opacity  or thickening of the latter,
with altered colour or consistence of  the former.
   From these premises it may be laid down as a just conclusion, that
the convolutions of the brain are the  centre of intellectual  action, or,
more strictly, that this centre  consists in that vast sheet  of vesicular
matter  which crowns the convoluted  surface of  the hemispheres.
This surface is connected with  the centres of volition and sensation
(corpora striata  and optic thalami), and is capable at once  of being
excited by, or of exciting them.   Every idea of the mind is associated
with a corresponding change in some part or parts  of this vesicular
surface; and, as  local changes of nutrition in the expansions of the
nerves of pure sense  may give rise to subjective sensations of vision
or hearing, so  derangements  of nutrition in the  vesicular matter of
this surface may occasion analogous phenomena of thought,  the rapid
development of ideas, which, being ill-regulated or not at all directed
by the will, assume the form of delirious raving.
   The  actions of the convoluted surface  of the brain, and of the
fibres  connected with it, are  altogether of the mental  kind.   The
physical changes in these parts give rise to a corresponding mani-
festation of ideas; nor is it likely that any thought,  however simple,
is unaccompanied by change in this  centre.   The  shock of concus-
sion so far checks the organic changes of  the vesicular surface, and
perhaps also of the  fibrous  matter, as to interrupt  for  a time those
conjoint actions of the  mind  and the brain which  are necessary for
perfect consciousness.   The  condensation of the  substance  of the
hemispheres which is produced  by an apoplectic clot, or by the effu-
sion of some other foreign matter, prevents a similar consent of action,
and thus gives rise to the phenomena of coma, in which all  mental
nervous actions  are  destroyed  or suspended.  Those  parts  of the
cerebro-spinal centre on which  the  physical  actions depend, being
more completely protected from compression, do not suffer in their
functions, and consequently actions of this kind remain unimpaired.
   This view of the function of the convolutions of the brain  has been
held by nearly  all the  great  anatomists  who  have directed their
investigations to  this wonderful organ.   Our countryman, Willis,
distinctly advanced  this  opinion in  the  seventeenth century,  and
conjectured that the various gyrations were intended for retaining the
animal  spirits " for the  various acts of imagination and  memory" 
324
INNERVATION.
within certain  limits.   The  distinguished  Gall, however, proposed
to assign certain  convolutions as the seat of certain faculties of the
mind—moral  feelings,  or instinctive propensities—and  upon  this
basis  raised the  celebrated theory  of Phrenology, which has been
pursued since  his. time with all the zeal and interest naturally attach-
ing to a science which professes from external  signs to detect  the
natural tendencies of the spirit within.
   We do not  propose  to  discuss the validity of this theory, which
seems to have  been taken up with  more  apparent zeal  for victory,
than  love of  truth.  But  we  shall  remark, that, in considering the
truth  or falsehood of Phrenology, it is absolutely necessary to separate
the metaphysical  question—as to the existence of  certain  faculties of
the mind—from what has been admitted as a physiological fact before
the foundation  of the phrenological  school, that the vesicular surface
of the brain is the prime  physical agent in the working of the intel-
lect.   A physiologist may hold the validity of this latter doctrine,
and yet think as  we do, that  many  of the so-called faculties  of the
phrenologists are but phases of other and larger powers of the mind ;
and that the psychologist must determine what are, and what are not,
fundamental faculties of the mind, before the physiologist can venture
to assign to each its local habitation.   The empirical method, by which
Gall first fixed upon certain parts of the brain as the seat of certain
faculties, is  exposed to  this serious  fallacy, that a part on  the surface
of the brain may  appear largely developed, by reason of the large size
of some subjacent or  neighbouring part.   We have already shown
how this may  be the case with reference to  the cerebellum, and that
a thick neck and large  occipital  region may, and  probably do, indi-
cate a large mesocephale  more  frequently than a large  cerebellum.
At the same time we think that all  observation, both in man  and in
the lower animals,  proves that  the energy of any  nervous centre
always bears   a  direct  proportion  to its bulk, whether  absolute  or
relative ; and  that the phrenologists do not err in attaching great and
primary importance to the size of those parts with which they asso-
ciate  certain  faculties:  while the   attention which  recent writers of
that school  have paid to the  temperaments  of the individuals under
examination,  is  a  proof of their admission that  the quality of the
nervous matter constitutes a highly  important element in the develop-
ment of nervous power.*
   We have seen that the convoluted vesicular surface, and the fibres
of the centrum ovale,  are the seat  of  those physical changes which
accompany, and  are necessary to, intellectual action.  A large num-
ber of these fibres is commissural, but the greatest proportion of them
serves to establish a communication between the centre of intellectual
action, and the centres  of  volition and sensation.   Through the con-
nection with the  former the intellect may prompt or excite the will;
and the will,  on the  other hand,  may control, direct, or apply the
powers of the  intellect.   The faculty of Attention, and, therefore, in

  * Carus has lately^propounded a new Cranioscopy, founded upon the tripartite
composition of the cranium, which bids fair to rival the system of Gall.  See a Lec-
ture in Lond. Med. Gazette, vol. xxxiv., translated by Dr. Freund. 
PHRENOLOGY.
325
a certain degree, the power of Memory, are dependent on the  influ-
ence of the centre of volition upon  the centre of  intellectual action.
Every one  is  sensible of a power which he possesses  of  fixing  his
attention on any given subject, as  distinct as that by  which he  can
contract  any particular muscle.   Again, the association of the intel-
lectual centre with that of sensation  is necessary to ensure the  full
perception  of  sensitive impressions.   The  experience  of  each indi-
vidual can  supply him with numberless instances in  which,  while
the mind was  employed upon  some other  object of interest, an  im-
pression was made upon some one of the organs of sense,  and  indis-
tinctly felt, but not  fully perceived.   When the  mind has become
disengaged, the fact that an impression had been  made is remembered,
without any ability  to recollect its precise  nature.   And in  many
lunatics the centre of intellectual action is so impaired as to destroy
or  greatly  reduce the power of perception, whilst there is abundant
evidence to show that the affections of the organs of sense still make
a sufficient impression on the  centre  of sensation.  In some  cases,
however, this centre likewise participates in the general hebetude.
   Perfect  power of  speech, that is, of expressing our thoughts in
suitable language, depends upon the due relation between  the  centre
of volition  and that of intellectual action.   The latter centre may have
full power to frame  the thought; but, unless it can prompt the  will
to a certain mode of sustained action,  the organs of speech cannot be
brought  into  play.   A loss of the  power of speech is frequently a
precursor of more extensive derangement of sensation and motion.
In  some cases  the  intellect seems clear, but the patient is  utterly
unable to express his thoughts; and in others there is more or less of
mental confusion.  The want of consent between the centre of intel-
lectual action and  of volition, is equally apparent in  cases of  this
description, from the inability of the patients to commit  their thoughts
to writing.
   The hemispheres  of the brain,  as  has  been already  stated,  are
insensible  to pain from mechanical division or irritation ;  in wounds
of  the cranium in the human subject, pieces of  the brain  which  had
protruded  have been removed without the knowledge of the patient.
Nevertheless, pain is felt in certain lesions of the  brain,  even when
seated in the substance of the hemispheres, or in the optic  thalami or
corpora striata.   This results from  the  morbid state  affecting other
parts with which nerves are connected, as the medulla oblongata  ; or
in  which nerves are distributed, as the membranes.   The nearer a
cerebral lesion is to  the membranes or to the medulla oblongata, the
more likely is it to excite pain.   Headaches, of whatever nature, must
 be referred to irritation either at their  centres or at their periphery, of
 those nerves  which  are distributed  in the dura mater, or in the scalp.
 The branches of the fifth pair, of the occipital nerve, and  the auricu-
 lar branch of the cervical plexus, are those most frequently affected.
   Certain  sensations are referred to the  head which  may  occur from
 a morbid  state, or  may be  produced by changes of position  in the
body.  Such are, vertigo, a sense of fullness,  or of a weight in the
head, a feeling of a tight cord round the head.  These  are, no  doubt, 
326
INNERVATION.
truly subjective, arising from alterations in the distribution or in the
quality of the blood sent to the brain.  A sensation of a  rushing of
blood to the head is often consequent upon excessive hemorrhage, or
accompanies  a state of  extreme debility from any cause.  This is
owing in great part to the feeble tone of the arteries, resisting imper-
fectly the flow of blood to the  head, and  allowing it to  impress the
nervous  matter too much.   It is well known, that, by turning round
quickly  on  one's own axis, the  sense of vertigo may be produced,—a
confused feeling in the  head, and an  inability to maintain perfectly
the balance of the body,  accompanied by an appearance as  if external
objects were  revolving.   If-the eyes be kept  shut, the  uneasy  feeling
of the head will take place, but no true vertigo.   To obtain this  feel-
ing perfectly, the eyes  must be open, and objects presented to them.
And Purkinje has shown that the direction in which external  objects
appear to revolve is influenced by the position of the body  and of the
head while turning round, and  by the position of it afterwards, when
the experimenter has ceased  to move round.   If the experimenter
have kept his head in the vertical position while  moving round, and
afterwards  when standing still, the objects appear to revolve in the
horizontal direction.  If the head be held with the occiput upwards
while turning round, and then erect when standing still, the  objects
seem  to rotate in  a vertical plane, like  a wheel placed  vertically
revolving round its axis.  (MiXller^s Physiology,  by Baly, vol. i., p.
848.)   It is  highly probable that these  sensations, as well as those
which arise  spontaneously, are due to some  irregular distribution of
blood to various parts of the brain.  A sense of giddiness frequently
precedes fainting, and is attributable to the  temporary deficiency in
the supply  of blood to the head.   If the horizontal position be imme-
diately adopted, or the  body be laid  with the  head inclined  down-
wards, the  faint may be prevented.   The sense   of giddiness which
is experienced upoft rising from  the horizontal position  after  illness,
is doubtless of the same  kind.  Anemic patients experience this  feel-
ing of giddiness even in  the horizontal posture;—and both it and the
headache and delirium, which accompany this state of bloodlessness,
may be  somewhat  relieved by placing the  patient  on  an inclined
plane with  the head downwards.
   The mind  possesses a  remarkable power of exciting and  of exalting
painful sensations in various  parts of the body.   If the  attention be
directed very strongly, and for  some time, to any part, that part may
become the seat of pain, for which the most effective remedy  is to
engage  the thoughts as   much as possible on  some other object.   In
many instances,  where pain has been  excited by a physical cause,
there  can be  no doubt it has been continued  long after the cessation
of its exciting cause,  by the  attention  of the patient having  been
directed to it.  It  is probable, that in such cases the perceiving  parts
of the brain (so to  speak) become habituated  to a certain condition of
the centre  of sensation, produced by the  original exciting cause of
the pain.
   Nerves are implanted  only in those  parts of the encephalon which
are capable  of  physical nervous actions: the convolutions of the 
SLEEP.—COMA.
327
brain, the corpus striatum, the optic thalamus, and  the cerebellum,
are capable only of mental  nervous actions.  In  every  change  of
these latter, the mind is either the excitor or excited; the conditions
of the  nerves involve them only through the influence of the centres
in which the nerves are implanted; and they affect the nerves only
through the same medium.  Matteucci's experiments as to the effects
of electricity on the different  parts of the brain, showed that, as long
as the  current was confined to those parts which are capable only of
mental actions, no apparent effect was  produced.  But  when  the
poles of the battery had  penetrated to  the  base of the brain so that
the current might pass through the-deeper seated parts, then the animal
cried out with  pain, and strong convulsions were produced.
   Those parts  in which physical nervous actions take place, (although
capable of partaking in the mental actions,) require the excitation of
physical stimuli in order  to  develop their peculiar phenomena, and
thus have frequent remissions in the active performance of their func-
tions in the frequent absence of the ordinary stimuli.  But the ever-
active mind keeps up a constant and proportionally rapid  train of
changes in those parts which  are more  especially connected with
mental actions:  hence these parts, requiring repose, fall  at  certain
periods into that peculiar and inscrutable  state called sleep; in which,
whatever be the condition of the mind  itself, the brain either refuses,
or is  slow to respond to its  stimulation, or to convey impressions to
it.  In deep sleep we are completely unconscious, and may remain
for a considerable time motionless.   But, as the accustomed period
 of repose  approaches  to its termination, the  sleep becomes lighter, a
 degree of consciousness returns,  and  mental  changes take  place,
 which, whether incoherent  or  connected, constitute what are fami-
 liarly  known  as dreams.   In  lighter sleep, it cannot be  said  that
 there  is complete want of consciousness ;  nor is the mind, although
 comparatively quiescent, in complete  repose.   The readiness with
 which, at times, some persons, during  sleep, reply when addressed,
 and resume the waking state,—the power which many unquestionably
 have  of limiting the  duration of  sleep to a predetermined period, as
 contrasted with  the deep unconsciousness and  slowness to awake of
 others,—strongly favour this idea.
    This state, with  which the revolution of each diurnal period makes
 us familiar as one of  repose to the great centres  of mental nervous
 actions—"tired Nature's sweet restorer"—occurs, with modifications,
 as the result of certain morbid processes, as the effect of certain phy-
 sical  agents, or even as the  consequence of peculiar states of mind.
 Thus, under the influence of pressure, from a clot of blood compress-
 ing the brain, or from lymph or fluid at its base, a state varying from
 that  of drowsiness up to the profoundest sleep, or coma, may be in-
 duced.   Whatever be  the  nature  of the compressing substance, or
 wherever situate, if the hemispheres experience general pressure, this
 result will ensue.  Again, a class of drugs, of the sedative or narcotic
 kind, exerts a similar influence;  and,  if given  in  too large a dose,
 will paralyze  the brain.  We have daily evidence of this in the effects
 of opium, which paralyzes  at first the centres of mental actions, and 
328
INNERVATION.
ultimately those of physical actions.   Lastly, particular states of the
system, induced, perhaps, by deranged  assimilation, or by great pre-
vious disturbance of mind, dispose persons to fall into that state which
is called somnambulism.   The somnambulist is one who dreams, and
acts in his dream as if he were awake, and as if all the  phenomena
presented to him were real.   He  appears to the  bystanders in a deep
sleep, but acts  with wonderful precision, walks with steady gait, and
avoids obstacles.  Yet frequently accidents,  injurious or even  fatal,
occur; which show that on  such  occasions he is asleep, and  has not
the full  command of his senses.   Persons in this  state will  answer
questions rationally and with readiness, and do not appear to be at all
disturbed by being  questioned.   The hypochondriacal or  hysterical
diathesis disposes greatly to the development of somnambulism both
in male and female.
  A state remarkably analogous to this  of  somnambulism may be
induced in persons of  nervous  temperament,  which  has been  called
the Mesmeric sleep,  or trance.   It requires  for its production the
apparent influence  of another  individual, who  watches the  person
experimented on with an intent look,  and makes certain  movements
before him,  which are called passes.   All  persons are not susceptible
of passing  into this  state, any  more than they are of  exhibiting the
phenomena of somnambulism.   The same state of constitution  which
disposes  to the latter is favourable to the former.   Remarkable state-
ments  have  been  made, and confirmed by the  testimony of  a large
number of observers, tending to imply that in these cases the faculties
become exalted in an extraordinary manner;  and that  the individual
acquires  powers of a  novel description, and even of  a superhuman
kind.  It behoves all sober-minded  persons to be slow  to accept
such statements as true,  and, without impugning the veracity of the
reporters, to inquire whether they do not rest more upon a misinter-
pretation than upon a misrepresentation  of facts.   The polar force of
the mental nervous centres may, in this  peculiar state, be so affected
as to favour the development  of  subjective phenomena, which it is
evident may assume  particular forms under the  influence of impres-
sions  made  from time to time  upon the senses.  The ravings of a
delirious or of a lunatic patient often take a particular direction under
the influence of a question  or remark let  fall by some bystander; it
is not unlikely that persons, with a mental bias  for  the marvellous,
might discover in such patients quite  as much evidence of superhu-
man power, as  has been  adduced  by the Mesmerists.
  We  cannot avoid  remarking how much it is  to be  lamented  that
inquiries of  so delicate a nature, affecting  the very confines between
mind  and matter, should have  usually fallen  into the  hands of per-
sons ill qualified for such pursuits, either  by mental  constitution or
by previous experience in the  study of  subjects involving  both phy-
sical and metaphysical knowledge.   Little is to be expected in such
difficult researches from dilettanti of either sex; much less from those
whose excessive zeal for novelty  and  notoriety must necessarily cast
suspicion on their statements.   Nor can we hope  that truth  can be
elicited from experiments  and observations which are made  before 
FUNCTIONS OF THE COMMISSURES.
329
the public gaze, with more of the characters of a theatrical exhibition
than of a sober philosophical investigation.
  Functions of the Commissures.—The commissures of the brain have
long been regarded as provisions to ensure the harmonious co-opera-
tion of certain parts of the  nervous  centres, whether on the same or
on  opposite sides.   This opinion rests mainly upon their anatomical
connections; for but little that is satisfactory can be concluded from
either the comparative anatomy or  pathological conditions of them.
It is evident that the principal  commissures bear a direct  ratio in
point of  development  to that of certain parts; and that, when those
parts are imperfect or absent, the commissures are deficient  or wholly
wanting.  Thus the corpus callosum and the hemispheres  are deve-
loped together;  the fornix and  the hippocampi,  the pons Varolii and
the cerebellar hemispheres.
  The anatomy of  the corpus  callosum favours the hypothesis that
it is the bond of union to the convoluted surface of the  hemispheres,
and that it is the medium  by which the double organic change is
made to correspond with the working of a single  mind.  There is
nothing in the recorded observations of morbid change  or congenital
defect of this part  to  militate  against this idea;  but it must be re-
marked that all these cases  are accompanied with  lesion or defect of
other parts,  which weaken the inferences to be drawn respecting the
corpus callosum.  Direct experiments  upon  this  commissure  yield
only negative results.  Longet and  others found that irritation of it
did not  cause  convulsions: and Longet  states, that injury  to  the
corpus callosum in young rabbits and dogs did not  appear  to disturb
voluntary movements ; and  that, when he incised  this  body in its
whole  length  in rabbits standing, they have  continued  to maintain
that position;  or,  when urged  on, ran; and  that  no convulsive
movement  whatever, nor any sign  of pain was manifested.   Such
statements are certainly favourable to the supposition that these fibres
are destined to connect centres  whose appropriate stimulus, is mental.
  The fibres of the fornix manifest the same insensibility to mechani-
cal irritants; and their obvious anatomical connection with  particular
convolutions warrants but  one conclusion,  that they associate  the
actions of those parts.  Lallemand relates a ease in which the symp-
toms were  altogether  limited  to mental  disturbance,  without any
affection  of  the sensitive or  motor powers, and the fornix and corpus
callosum were found in a state  of  complete  softening  without  dis-
coloration.
  The fibres of the pons Varolii bring the cerebellar  hemispheres
into connection with each other, and with the vesicular  matter of the
mesocephale.   Direct experiments on these fibres can yield no satis-
factory result, because they are so intimately  associated  with  the
deeper seated parts of the  mesocephale, and with the nerves  of  the
fifth pair and others, that it is impossible to irritate them  in the living
animal without likewise irritating these other parts.   And  it is suffi-
ciently evident that  these fibres  have no necessary connection with
sensation and volition, from their non-existence in birds;  nor even
with the cerebellum when that  organ is single.   It will be borne in
       22 
330
INNERVATION.
mind that at a previous page we have referred to the connection of
these fibres with the mesocephale as explaining the crossed influence
of lesion of one  hemisphere of the cerebellum.
   We conclude this  chapter with  the following  inferences, which,
we think, the present  state of knowledge justifies:
   1.  The  spinal  cord contains within itself all the physical condi-
tions necessary  for the mental and  physical actions of the  trunk and
extremities, so long as its  connection with the  encephalon is perfect
through the anterior pyramids.
   2.  There is no sufficient evidence to prove the existence of a class
of sensori-volitional  fibres distinct from those  which  are  the instru-
ments of physical actions.
   3.  Each segment  of the  cerebro-spinal centre,  whether  in the
cranium or in the spinal canal, gives origin to its own proper nerves,
and has no  connection with the  neighbouring segments, otherwise
than by commissural fibres or vesicular matter.
   4.  The  antero-lateral  columns of the cord, with  the  anterior and
posterior horns of the  gray matter, are the  effective centres of motion
and sensation of the trunk and extremities.   The posterior columns
are longitudinal commissures by which the  influence of the cerebellum
is brought to bear on  the various segments of the cord.
   5.  When  the  pyramids are  in  a  state of  integrity,  the corpus
striatum, certain  accumulations of gray matter connected with the
nerves of  the medulla oblongata, the  locus  niger,  and  the anterior
horns of the spinal gray matter are  the centres of voluntary motion to
the whole  body;  while the optic thalami,  olivary  columns, and pos-
terior horns of gray matter are the centres  of sensation.
   6.  The  medulla oblongata, when  connected to the corpora striata
by the pyramidal fibres, is a centre of voluntary actions to  those parts
whose nerves are derived  from it; and, in  addition, it is the principal
centre of the actions of respiration and  deglutition.
   7. The  corpora quadrigemina are  primary centres of  visual im-
pressions,  and,  with a large  portion of the gray matter in the  meso-
cephale, are centres of emotional actions.
   8. The  cerebellum is the co-ordinator of voluntary and locomotive
actions.
   9. The  convolutions of the brain  are  the  centres of intellectual
actions, and are intimately associated with the  mental phenomena of
attention,  association,  and memory.

   On the subjects discussed in this chapter we refer to the more recent treatises on
Physiology, by Muller, Wagner, and Carpenter;—to Dr. Marshall Hall's writings on
the Nervous System; the  most important of which will be found in an octavo vol-
ume "On the Diseases and Derangements of the Nervous System," 1841; and in  a
quarto volume "On the Nervous System," 1843;—to Henle's  General Anatomy;—
Whytt on vital motions;—Prochaska, Annot. Academics;—Le Gallois, CEuvres;—
Flourens sur le systeme nerveux;—DesmoulinsetMagendie surle systeme nerveux;
—Longet, Anat. et  Physiol, du systeme nerveux;—Volkmann, in Mailer's Archiv. ;—
Van Deen, sur la  Physiol.de la Moe'lle Epiniere,  and the works referred to at the
conclusion of the last chapter.
  Appendix to the Eleventh  Chapter.—Whilst the preceding pages were passing
through the press, we were favoured, through the kindness of Prof. Matteucci of Pisa, 
         MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES.     331


 with several  opportunities of witnessing his highly important electro-physiological
 experiments.   As these experiments tend very much to confirm and substantiate the
 views expressed in Chap. IX., we subjoin here a succinct account of them.
   The facts which M. Matteucci's researches have developed are the following:—1.
 That muscle  is a better conductor of electricity than nerve, and that nerve conducts
 better than brain.  2.  That in the muscles of living  animals, as well as of those re-
 cently killed, an  electric current exists, which is directed from the interior of each
 muscle to its surface.   3. That  in frogs, a current exists peculiar to the  Batrachian
 reptiles, which proceeds from the feet to the head, and  is distinct from the muscular
 current.  4. In  continuation of Marianini's and Nobili's researches, Matteucci illus-
 trates the effects of the inverse and direct currents in nerves of different function, and
 shows very strikingly the difference in the influence of the electrical stimulus  upon
 nerves, from that of other stimuli upon these organs.
   For these researches Matteucci employed the galvanometer of Rumkorff (Paris),
 which is the same as that of Nobili with the addition  of a small apparatus, by means
 of which the  needles  may be rendered more or less astatic, and thus the  sensibility
 of the galvanometer may  be  more  or  less increased.  But he also takes  the pre-
 caution, to guard against the development of currents by unequal chemical action
 upon the poles of the galvanometer, to have them made of plates of platina, which is
 not acted upon by water or saline solutions.  He takes two plates of platina, about a
 quarter of an inch in  breadth, and  fixes each in a handle of wood.   The plates are
 then soldered  to the wires of the galvanometer, and both the handles and the  plates
 are covered with  a layer of sealing wax-varnish, leaving only a  space  of  about a
 quarter of an inch uncovered at the extremity of each  platinum plate.
   The frog's leg, prepared in a certain way, is most susceptible of electric influence,
 and therefore  may be used as a galvanometer of extreme delicacy.  The skin is strip-
 ped off one lower extremity of a lively frog, and the whole length of the sciatic nerve is
 dissected out from among the muscles of the posterior part of the thigh ; after which,
 the thigh is cut across just above the knee, the nerve remaining attached to the  knee
 and leg.  The leg is now placed in a glass tube* in  such a position that the  nerve
 hangs loosely from the end of the tube.  To use this gal vanoscope, the operator holds
 the glass tube at the opposite extremity to that in  which the leg is placed, and causes
 the nerve, which hangs loosely  from the tube, to touch at two points the electromotor
 element  under examination.  If the nerve be traversed  by a current, the leg instantly
 contracts.   This  apparatus,  called  by  Matteucci grenouilk galvanoscopique, is the
 most delicate we possess, if it be renewed from time to time.  And it is capable, not
 only of Indicating the  existence of an  electric current, but also of showing, with a
 great degree of probability, the direction of that current.   When the frog has  become
 a  little weakened, it  almost constantly happens  that  the  contraction takes place on
 closing the circuit, if the current pass from the nerve to the leg; but if it pass from
 the leg to the nerve, contraction  will  take place on opening the circuit.*
   1. Matteucci's  experiments upon  the  relative  conducting power of animal  sub-
 stances,  were founded upon a law of derived currents.  When  a liquid, Or any other
 body, is  traversed by an electric current,  and the plates of the  galvanometer are
 plunged  into it, there are immediate indications of a derived current, so directed in the
 galvanometer, that the  point at which it enters the coil of the galvanometer, corre-
 sponds to  the positive pole of the current which  traverses the  liquid.  The  derived
 current is always greater, as the plates of the galvanometer, plunged in  the liquid,
 are more distant from  each other.   If a current be  made to traverse different sub-
 stances,  which correspond as nearly as possible as regards shape, bulk, etc., the de-
 rived current from each will be  exactly in the inverse ratio of the conducting power
 of  the substance traversed.
   Pieces of nerve, brain, and muscle, from  a rabbit just killed, were selected  for the
 comparative experiments; these were cut so as to correspond as nearly as possible
 in point of size and shape, and disposed as a chain on an insulating plane.   Platinum
 wires, fixed by sealing-wax to two pieces of cork,  which were held apart at a  certain
 distance  by a rod of glass which transfixed each of them, were soldered to the wires
 of the  galvanometer, the platinum wires having been previously varnished  to within
 a very short distance of their extremities.  A current from twelve cells of a Constant
 battery, was now passed through the chain  of animal substances.  The  platinum
 wires,  held always at the same distance from each other, were  successively brought

  * Those who propose to employ the galvanometer in physiological experiments, should
carefully observe the precautions assigned by Matteucci, in  the third chapter of his book,
to guard against erroneous inferences. 
332   '
INNERVATION.
  into contact with brain, nerve and muscle, and  the deviation of the needle  resulting
  from the  derived  current in  each case was carefully noted.  The derived current
  from nervous matter was  always greater  than that from  muscle; that  from brain
  greater than that  from nerve, denoting a less  conducting  power in nervous matter
  than in muscle—in brain  than in nerve.  By increasing the distance between the
  platinum  wires, a derived  current may be obtained from  muscle equal to that ob-
  tained from  brain ; and Matteucci, from this latter  experiment, infers that the con-
  ducting power of  muscle may be taken as  four  times greater than that of brain or
  nerve.
    Another interesting experiment confirmed the results obtained from those just de-
  tailed.  The current was made to traverse the whole trunk of a rabbit just killed and
  flayed,  and the platinum wires, held at a constant distance, were applied successively
  to different parts, muscles, nerves, etc.;  the current was  found to traverse  all  parts,
  with such difference as was due to the different power of conduction of the different
  substances; that is, so as to yield a derived current of less intensity from muscle than
  from nerve, or from nerve than from brain.
    2.  To demonstrate  the existence of an electric current in the muscles of animals
  recently killed or living, the following experiments have been adopted by Matteucci.
    If a deep wound be made in a muscle of any living animal, and the nerve of the
  galvanoscopic frog be introduced into it, so that the nerve shall touch the cut surface
  at one point, and the outer surface of the muscle at the other,  contractions  instantly
  take place on completing the circuit.  It is evident that this effect is due to an electric
  current developed by the muscle, because it is necessary that the nerve should touch
  the muscle at two points; and because,  if the nerve  be brought into similar contact
  with two  points of any other body, no such effect will follow.  To  guard against the
  fallacy that might arise from contact with the blood, Matteucci shows, that if a nerve
  be brought into contact with a layer of  blood at two  different  points, no evidence of
  an electric current will appear.   In this, and all experiments with the galvanoscopic
  frog.it is  to be remembered that the frog's leg must be held in  the glass  tube  to in-
  sure perfect insulation.  The experiment is always followed by the same results,
  whatever be the muscle or the animal touched, or even  if muscles  separated from
  the  animal be operated on.  The indications of the electric current remain longest in
  those animals in which the  muscular contractility lasts  longest;  in cold-blooded
  animals,  such as fish and reptiles, Matteucci  has  seen  the phenomena last  for many
  hours.   The current  is sufficient to excite  the  nerve of  a warm-blooded animal.
  The thighs of a rabbit having been removed, a long  portion of the crural nerve was
  dissected out, and the muscles exposed.   With a glass  tube the nerve was raised and
  brought  to touch the muscles at two points, when the whole  limb was thrown into
  contraction.
    So far, distinct evidence was afforded by the animal galvanometer, (so to speak,)
  of the existence of a muscular current.  When the frog's leg  becomes a little weak,
  it indicates the  direction of the current to be from  the interior to the surface of the
  muscle.
    In order to demonstrate the influence of this current on the  galvanometer, a parti-
  cular arrangement is necessary.
    Several small cup-like cavities are scooped out in a piece of wood, twelve inches
  square, and an inch and a half thick.  The wood  and its little cavities are coated
  over with a layer of varnish, or small capsules sunk into the wood may be employed.
  Five or six frogs  are prepared, by flaying the posterior extremities, and the legs are
  separated by disarticulating  them at the  knee; which  must be done with care, in
. order not to wound  the mass of crural muscles. Next, each thigh is divided at its
  middle, and thus a certain number of conical masses (the lower halves of the thighs)
  are obtained.  These must be  arranged on the  board in a chain.   One half-thigh is
  placed at the edge of  one of the cavities, with its apex to the cavity, and the cut sur-
  face outwards; and the chain is completed  by arranging the others  in a semicircle,
  so  that  the apex of one freely touches the  cut  surface of the other,  and  the  piece
  which forms the opposite extreme of the series ought to touch the edge of  another of
  the cavities by its cut surface.  Thus, a pile is formed, of  which one of the extremi-
  ties is the  interior of the  muscle, and the  other its external surface.  The  board,
  with the muscular pile arranged upon it in this way, is now brought to the galvano-
  meter, the platinum  poles of which, if it be  a very sensible one, have been  some
  time placed in distilled water; or, if not very sensible, in a saline solution.  The
  next step of the experiment is with a pipette, to pour into the  cavities with  which the
  extremes of the pile  are connected, either water or some of the saline solution, ac-
  cording  as the plates of the galvanometer have been immersed in either of those
  fluids. 
       MATTEUCCI'S  ELECTRO-PHYSIOLOGICAL RESEARCHES.    333


  The  platinum poles of the galvanometer are  now withdrawn from the fluid in
which they had been immersed, and introduced into the fluid of either of the cavities;
if no deviation of the needle follow this, they are at the same time plunged into the
two extreme cavities of the pile, so as to close the circuit.  A deviation of the needle
takes place immediately,  which varies in amount according to  the  number of seg-
ments which constitute the pile.  Matteucci has obtained a deviation of 15°, 20°, 30°,
40°, 60°, etc., according to the number of half-thighs, supposing the  frogs employed
to be equally lively ; he obtained  3° or 4° with two elements, 6° or 8° with four ele-
ments, 10° or  12° with six, and so on.  These numbers are obtained, using distilled
water in the cavities; but the deviation may be increased considerably if a few drops
of sulphuric acid be added to it, so that a pile of eight  half-thighs, which  gave a de-
viation of 15° with  distilled water, will cause  50° with the acid liquid.   When the
fluid was slightly saline or alkaline, the same number of elements caused a deviation
of 35°.   In all the trials the current had the same direction—that is, from the internal
part of the muscle to its surface.
  The muscular current  may be demonstrated with the muscles of other cold-blooded
and of warm-blooded animals.  In  all cases it is necessary so to arrange the elements
of the pile, that the  inner surface  of one  segment shall be  in contact with the  outer
surface of the next, and that the inner surface of a piece of muscle shall form one
pole, and the outer surface of another piece the opposite pole.
  The duration of the muscular  current corresponds with  that of contractility.  In
cold-blooded animals, therefore, it is greatest.  In mammalia  and birds  it is very
brief.  Temperature has a considerable influence upon the intensity of the current.
If frogs  are placed for some time in a very cold medium, piles made  from their mus-
cles yield no evidence of electricity ; but, if the frogs are placed in a warm medium
for a short time after they have been taken from a cold one,  the  current of electricity
obtained from their muscles will be stronger than that from  a similar pile which had
not been subjected to any change  of temperature.
  Any circumstances which enfeeble frogs, and derange their general nutrition, will
diminish the power of the  muscles to generate  electricity, as  they  also  impair the
contractile force.  Thus, Matteucci found the great heat of summer to impair mate-
rially the development of electricity.  We have found the same  result in frogs which,
having been kept crowded together in a small compass during the month of Decem-
ber, became ill-nourished, with soft, flabby muscles, full of moisture.  The  redder
and more consistent the muscles are, as Matteucci remarks, the more distinct will be
the signs of electricity.
  The muscular current  appears to be quite independent of the nervous system. The
segments of which  the piles are formed, are obviously beyond the  influence of the
nervous  centres ; and Matteucci has taken great pains to remove from such segments
all the larger nervous trunks and  filaments  distributed among  the  muscles without
affecting the electrical current.  And in frogs, in which the lower part of the spinal
cord  had been destroyed by burning, there was no evidence of impairment of the
electric current in the muscles of the lower extremities.
  Matteucci found that narcotic poisons, in moderate doses,  had little or no influence
upon  the muscular current.  On one occasion, he found it slightly increased in a frog
to which a very small dose of opium had been given.  In very strong doses, such  as
to kill the animal, the muscular current is destroyed.  The.iniiuence of the narcotic
gases upon the current is of no importance, with the  exception of sulphuretted hy-
drogen, which has the effect of materially weakening its intensity.
  On one  occasion, we  endeavored to obtain a  current from  a pile composed of
pieces of human muscle  from a leg that had just been amputated;  but the muscles
were  in so atrophied a condition, that  the experiment  failed with the galvanoscopic
frog, as well as with the galvanometer.   We have since learned from Professor Mat-
teucci, that he has obtained evidence of the current in human muscle under similar
circumstances.
  It is plain, from the statements above given, that the essential  condition  for the full
development of the  muscular current, is a healthy and vigorous state of the muscles
themselves, and that the nervous system contributes to the electrical phenomena only
so  far as  it contributes  to  the healthy nutrition of the muscles by  promoting their
natural actions. The muscular current  is  one of the phenomena which attend the
passive  contraction of muscles;  it disappears from dead muscle, and from  living
muscles which have so suffered in their nutrition as to lose  their characteristic pro-
perty.   All external influences which  materially affect the  nutrition, and therefore
the passive contraction of muscles, exert a corresponding effect  upon the muscular
current.   The duration of the current after systemic death, continues in the different
animals just so long as the phenomena of contractility are present. 
334
INNERVATION.
   3. In the latterpart of the  last century, Galvani announced his celebrated experi-
 ment, of causing contraction of the frog's leg by bringing its muscles in contact with
 the lumbar nerves.  The following are the steps of this experiment: The integuments
 are stripped off the lower extremities, which are separated from the trunk at the
 middle of  the back; a  small portion of the lumbar region of the spine, from which
 the lumbar  nerves emerge, is left with  these  nerves in connection with the  lower
 limbs, the  pelvis having been cut away.  If, now, the limbs be suspended by the seg-
 ment of  the spine, and one leg be carefully bent  up, so as to bring the foot into con-
 tact with  the lumbar nerve, the whole limb is convulsed at the  moment of contact.
 The foot may be made to touch the muscles at various parts of the limb without any
 such  effect.  The contraction is general, and evidently of the same  nature as that
 which the  passage of an electric current through the lumbar nerves would produce.
 When the  experiment is carefully tried, it is impossible that the nerve can experience
 any mechanical dragging, such as would produce an effect like that described.   Gal-
 vani pointed out, that, in order to succeed perfectly in the experiment, it is necessary
 to wait until  the frog has recovered from  the  tetanic  state which is likely to ensue
 upon  the  necessary mode of preparation.  He  also  stated, that the  experiment is
 more likely to be successful if the frog have been previously moistened by a solution
 of salt; and that the contraction of the muscles may be produced if the  nerve and
 foot are  connected by  a piece of muscle, and  not directly.  The accuracy of Gal-
 vani's observations has been fully established by Humboldt, Valli, and many mod-
 ern experimenters.  We have frequently  repeated the experiment with the same re-
 sult.
  Fifty years after Galvani, Nobili* took up the same  line of inquiry.  Having pre-
 pared the legs of a frog according to Galvanfs method as above described, he plunged
 the lumbar nerves into one capsule and the feet into another, the capsules being filled
 with water.  When the  poles of a galvanometer were introduced into the fluid of the
 capsules, a deviation of the needle followed to the extent of 5°, 10°, or 15° or more.
 The deviation could be increased by making a chain of frogs' legs prepared in the
 same way.  The legs were placed on  an  insulating plane, so that the nerves of one
 touched the feet of  the next, and so on.  It is necessary  that the  extremities of this
 pile should be plunged into capsules filled with water., Or, a pile may be made with
 a series of capsules containing water, connected together by frogs' legs; the nerves
 being placed  in one, and the feet in the next.  With such piles, a deviation of the
 needle to the extent of 60° may be obtained ; or to a much greater extent, if, instead
 of distilled water, a weak  solution of  salt  be employed  to fill the capsules; or still
 more, if the fluid of the  capsules be slightly acid.
  In all these experiments the direction of the  electric  current was found to be con-
 stant, from the feet to the head.  At the same time that the needle was made to deviate,
 the frogs'legs, whatever be  the  number  constituting the pile, are thrown into con-
 traction.   It is not necessary for the production of the phenomena that the several
 legs should touch one another;  it will  suffice if they  be. connected by a conducting
 material, such as a  skein of cotton moistened, wire, wet paper, or even water.
  Nobili  found that these signs of an electric current continued for many hours after
 the preparation of the animal.  He distinguished the current by the title of le courant
 de la grenouille, ou courantpropre ,■ and  he  attributed it to a thermo-electric current
 caused by the unequal cooling of the nerve and muscle produced by evaporation.
  It is evident that the experiment of Nobili is  essentially the same as the original
 one of Galvani.   In the  latter the electric current was brought to act upon the nerves
 of the limb;  in the former, upon the galvanometer.
  The galvanoscopic frog maybe used as  a test of the  electric current when Nobili's
 arrangement  is preserved.  If the extremes of the pile be connected by the nerve of
 the galvanoscopic limb,  the instant the circuit is completed, its muscles will contract;
 and, as in other experiments with the galvanoscopic frog, we may determine the di-
rection of the current when the frog becomes a  little weakened.
  Matteucci gives the  name " contraction propre"  to the contraction of the muscles
 which  takes  place  in the frogs'legs, whether used singly or as a pile, at the same
 time that the deviation of the  needle  occurs. In  order  to  obtain this phenomenon,
the lumbar nerves must  not be plunged completely in  the water; otherwise the pro-
per current circulates without passing through the nerves, and consequently the con-
tractions  do  not take place, or are extremely feeble.   These contractions continue,
generally, only for ten or fifteen minutes, but rarely for half an hour after preparation.
  Nobili  has stated, that in arranging the  frogs, so that  the nerves of one touched
those of the other, or the  muscles came in contact with muscles, no contractions
•
* Bibliotheque Universelle, 1827. 
        MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES.    335


 ensued, because, as he explained, the electromotor elements were opposed.  In Mat-
 teucci's hands, however, such a result was  not obtained.  If care be taken not  to
.oppose to  each other the nerves or muscles of symmetrical  parts, contraction will
 always ensue.
   The following is Matteucci's mode of showing this remarkable experiment.  The
 limbs of a frog are prepared  in the ordinary way ;  but, in addition, the heads of the
 thigh-bones and the ilium  are completely removed,  so as to leave the legs connected
 to each other only by the nerves, through the portion of the cord which is contained
 in the segment of  the spine which remains.  The parts  are placed on an insulating
 plane.  If the  muscles of one  leg are made to touch the other thigh, contractions
 ensue; but not so if the  leg of one  side touch the leg of the other.  Or the same
 effect may be produced by bringing  the  different parts of the  limbs into connection
 by moist  paper or cotton; or, if the  galvanometer be employed, signs of a current
 are afforded, by touching a thigh with one pole, and the opposite leg with the other.
   In these experiments, when the frog is lively, contractions are produced,in touching
 the muscles of the thigh with those of the  leg, as well on opening  as on  closing the
 circuit.  But when it has become weak, contractions take place in one limb on clos-
 ing the circuit, and in the other on opening it.
   Matteucci explains the  failure in  producing contractions by touching correspond-
 ing parts, on the supposition  that, under such circumstances, the currents of the two
 limbs  circulate with equal  intensity, and in a contrary direction.  This he proves by
 the following experiment: If the frogs' legs, prepared as above described, are severed
 from each other, and the nerve of one leg  and the foot of the other are placed in one
 capsule filled with water, while another capsule receives the other nerve and foot; the
 moment the circuit is completed, strong contractions  in  both limbs  are produced.
 But to the galvanometer no sign of an electric current is afforded when its poles are
 plunged into the capsules.  "In this case," says Matteucci, "the currents of the two
 limbs  circulate  together, passing equally through the limbs; and if even the parts of
 the current were to take  the course of the  galvanometer, it is easy to see that they
 would circulate in it in opposite directions, and therefore would produce no deviation.
 If, on the contrary, the disposition of the two limbs be such that the  nerves are placed
 in one vessel, and the feet in the other, it is easy to see that the two portions of the
 current which do  not circulate through  the animal  arc, enter the extremities of the
 galvanometer, and circulate  in it in the same direction.  It is  the sum of these two
 portions which constitutes the proper  current of the frog, which sum is measured by
 the galvanometer.
   If several frogs' legs be  arranged with opposed nerves and feet in the two capsules,
 the effect upon the galvanometer is not increased.
   Comparative experiments  as to the difference of the currents in piles  formed  of
 both the lower extremities of frogs, as already described, and in piles formed of an
 equal number of single extremities, showed no greater effect upon the galvanometer
 in the one case than the other.
   From these and  numerous  other experiments, varied with great ingenuity and skill,
 Matteucci draws these conclusions:—1, that the complete electromotor  element  in
 the current of the frog is formed by one of its limbs—that is, of one leg, the thigh, its
 spinal nerve, and  a piece of its  spine;—2,  that the current of one limb circulates
 by the other every time that, leaving the frog intact, a communication  is established,
 in any way, between the two legs of  the same  frog;—3, that  in the experiment by
 which we  detect the  current of the frog by the galvanometer, there is never in the
 wire of the instrument any other current save that which results from the sum of the
 two portions of the currents of  the two limbs which are not discharged from limb to
 limb.
   It is important to notice, that there is no necessary connection between  nerves and
 muscles in the  production of the proper current of the frog.   Matteucci shows by
 several ingenious  experiments, that, although in Galvani's and Nobili's observations,
 the nerve and  muscle were brought  in contact, or  were  made to form conspicuous
 parts of the arrangement employed in the  development of the  phenomena, the signs
 of the electric current are just  as distinct  when the circuit is  completed by the con-
 tact of other parts; or if the  continuity be maintained by muscles,  the main nervous
 trunks having been removed.  Thus,  if a  frog be flayed, and  the bones and muscles
 of the pelvis be cut away, so as to leave the lower extremities attached to the thorax
 by the lumbar nerves, contractions will be produced by bending up the leg so as  to
 bring it in contact with the eyes, the  muscles of the head, or the back.   And if this
 frog be placed with its head in one capsule and its legs in another, the current may
 be  detected by the  galvanometer in the ordinary way.   Or, if  the spinal nerves arid
 the piece of the spinal cord be removed from the lower limbs prepared in the ordinary 
336
INNERVATION.
way, the signs of the current may be obtained by the usual methods.  Piles made of
legs'prepared in this way develop a  current equally intense  with that  produced
from piles with an equal number of elements composed of limbs with the nerves re-
maining.  It thus appears  that the electromotor element of the current is reduced to
the muscles of the leg and thigh in organic union.
  So  far, indeed, is the nerve from contributing to the production  of the  electrical
phenomena, that Matteucci found that a more feeble current was developed in piles
formed of the legs of frogs in which a very long portion of the nerve formed an ele-
ment.  He prepared the legs, leaving attached to them the  lumbar and crural parts
of the nerve, and formed the pile by placing the nerve on the adjacent leg, so that the
communication between the segments was maintained only by  the  nerves.  And it
may be shown further, that the nerve in these experiments  acts  only as a bad con-
ductor of the  electricity developed by the muscles; for, if the nerves be cutaway, and
the segments of the limbs connected by pieces of moist cotton instead, the phenomena
of the pile continue unchanged.
  Nothing analogous to the proper current has been found in any other reptiles but
the Batrachian—nor in any other class of animals.  It is not improbable, therefore,
that the proper current of  the frog may be due to some undiscovered peculiarity of
structure in ihat animal.
  How can we explain these remarkable electrical phenomena in the muscular cur-
rent directed  from the interior to the exterior of  all muscles in all animals ; and the
proper current of the frog, directed from the feet to the  head, and peculiar to the Ba-
trachian reptiles?
  It is not difficult to discover an explanation of  the muscular current.  The  essen-
tial conditions necessary  to develop  the signs  of this current  are simply, that, by
means of a conducting material, the interior of the muscular mass should be brought
into communication with the exterior of the muscle, which is more or less tendinous,
and covered with areolar tissue, and therefore different  from the interior in structure
and function.  And as  the signs of this current are apparent only whilst the muscle
is living—that is, while it continues  to display its contractile power, we may infer
that the same organic conditions which are necessary to the development of contrac-
tion, are requisite for the  development of  electricity.  Now all that is necessary for
the development of the contractility of muscle is (as has been shown in Chap, vii.)
a healthy nutrition, a due supply of arterial blood, and sufficient exercise of the  organ.
And it would be impossible, as Matteucci  remarks, not to admit that the  chemical
action which must be going on  throughout muscle, in the  constant supply and waste
of which it is the seat, can be unattended with the development of electricity.
   In short, the organic  actions of muscle, by which the electrical  current is developed,
may be compared to the inorganic phenomena attending its production from the de-
composition of metals.   When  a plate of metal,* immersed in an acidulated fluid, is
oxidized by the oxygen of  the water, and  then dissolved in the acid, we admit that
an enormous quantity of  electricity is developed during this action; we  add, like-
wise, that, just  as the  two electrical  states are  disengaged, a synthesis takes place,
and the effects of the previous decomposition are neutralized.  It is only by means
of certain arrangements, that we can obtain the free electricity which is developed
during chemical action. We unite to the metallic plate, another which is not attacked
by  the water, and plunge  this  second plate  also in the water.  The circuit is thus
established, and the electric  current circulates in the liquid from the metal acted on
to the other, and from this latter back again to the first through the metallic  arc of
union.
   The metal  acted upon in the  artifical arrangement is represented, in the phenome-
non of the muscular current, by the muscular fibre; the acidulated fluid is the arte-
rial blood.  The surface of the muscle, or any  other conducting body not muscular
fibre, but which is in contact with the muscle, represents the second plate of metal,
which does not suffer chemical action, and which serves only to form the circuit. The
direction of the  muscular  current is precisely  such as  it should  be, supposing the
current to be, as we have represented it, due to a chemical action taking place in the
interior of the muscle.
   The nervous system may act in two ways in connection with this phenomenon; 1,
as  an imperfect conductor, which makes part of a circuit, but is  not the source of
electricity; it represents  the  electrical state of  the muscular mass, interior  or sur-
face, with which it is in connection ;  and  2, it acts in the conservation of the cause
which disengages electricity, namely, nutrition.   It  is fully proved,  that  the integrity
of the nervous system,  and the nutrition of the muscles, are closely  leagued together;
* Matteucci, loc. cit., p. 124. 
         MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES.    337


 but as it cannot be admitted that the chemical action which takes place in nutrition is
 immediately arrested or suspended by the  cutting off nervous influence, so we must
 allow that the muscular current may continue after the nerve has ceased to exert any
 control over the muscle.
   The proper current of the frog does not admit of being explained upon these prin-
 ciples.   It has been supposed, as already stated, that this current-is a thermo-electric
 one, due to the unequal  cooling of nerve and muscle,depending on the difference of
 evaporation in these two parts of the animal.   But it has been shown that this cur-
 rent persists even  after the  removal of the nerve ; and, moreover, as Matteucci re-
 marks, a current which is sensible to a galvanometer with a long coil, which traverses
 thick layers of liquid, which  may be  obtained  by bringing muscle  in contact with
 muscle,  and which may be produced by holding animal parts in water, cannot,  cer-
 tainly, be of thermo-electric  origin.   It  has also  been supposed that this current is
 due to an electro-chemical action; that the leg of the frog is charged with alkali or
 salts, whilst the thigh or the lumbar nerve contains acid.  But chemical analysis
 of these parts  affords  no countenance whatever to this  hypothesis.  There  are
 remarkable points of analogy between this current and the muscular current. Mat-
 teucci's  experiments have shown that the  former has some marked connection with
 muscles, and with those of the leg more especially; and he has found that the same
 circumstances which increase or diminish the muscular current, exert a similar in-
 fluence upon the proper current.  But they differ remarkably in point of  duration;
 as the latter continues long after all  traces of a muscular current has ceased to be
 discoverable.  It is highly probable, as before stated, that the true source of this cur-
 rent will be found in some anatomical peculiarity of the frog.
   As in  the ordinary phenomena of the nutrition of muscles, by which their state of
 passive contraction or tone is maintained, electricity is developed, it is most reasona-
 ble to expect that during active contraction there  should be a  development of elec-
 tricity, as there is of heat likewise, according to  Becquerel and Breschet's observa-
 tions. This is  shown by Matteucci  in  a  very beautiful experiment which we have
 frequently repeated with the same results.  Place a prepared frog upon an insulating
 plane; then prepare the  legof another frog with the crural nerve dissected out and left
 attached to the leg, the thigh being removed.  Place  the  nerve of this leg upon one
 or both thighs of the other frog, and every time that those legs are excited to contract
 by a galvanic or a mechanical stimulus,  contractions will be produced in the second
 leg, which  is connected with the first only by the contact of its nerve with the sur-
 face of their muscles.  The same effect  will be produced, if the nerve of the frog's
 leg be placed on the muscles  of a warm-blooded animal,—a rabbit, for instance,—
 care being taken to remove any thick aponeurosis which may cover the latter.
   If an insulating substance be placed between the muscles of the thigh and the nerve
 of the leg,  no action will take place.  The  same effect is observed when gold-leaf is
 interposed; but if the gold-leaf be torn,  to however slight a degree, the  leg will be
 thrown into contraction.
   The electricity developed during the  contraction of the muscles,  stimulates  the
 nerve which is laid upon them;  the  interposition of a non-conducting substance
 prevents  the electric discharge from reaching the nerve ; and gold-leaf, being a better
 conductor than nerve, carries the electricity along it, passing by the nerve.
   4. The study of the effects of electricity applied in various ways upon nerves has
 led to some highly interesting and curious results.
   Nobili  ascertained that, in passing an electric current  through the  lumbar nerves
 of a frog, contractions  occurred under different circumstances, according to the state
 of vitality of the nerves.   He divided the vitality of the nerve into five  periods,
 during each of which different phenomena were produced by the passage of the cur-
 rent. In the first period, the  direct current, or that directed from the brain  to  the
 nerves, caused contractions in  the muscles  on closing the circuit; the inverse current,
 or that from the nerves to the brain, on opening  it. In the second period, the direct
 current causes contractions on closing the circuit, and slight ones on opening it;  the
inverse current causes contractions only on opening the circuit.  In the third period,
contractions occur only on closing the direct current and opening the inverse.  In  the
fourth period, contractions occur only on  closing the direct current; and in  the fifth,
the nerve ceases to be influenced by the electrical stimulus.  Marianini, who subse-
quently studied this subject, affirms that  contractions take place only under two cir-
cumstances, namely, from the  closure of the  direct current, or from opening the  in-
verse,- and  that a sensation is caused by the direct current on opening, but by the
inverse on closing.
   Matteucci repeated these observations on the sciatic nerves of the rabbit, devoting
one  nerve  to the direct, the  other  to  the  inverse, current.  On closing the direct 
338
INNERVATION.
current, contractions were produced in the  muscles of the limbs and back, with
marked signs of pain; the same phenomena result from closing the inverse current,
and from opening both.  The signs of pain were greatest at the closure of the inverse
current, and the contractions were most at the closure of the direct current.  The
commencement and the  interruption of an electric current of a certain intensity,
acting upon a certain portion of the nervous system, are followed by the  same phe-
nomena, whatever be the  direction of this  current  in the  nerve.  After some time,
which is shorter as the current is more intense, the phenomena take place in a differ-
ent manner.  Upon interrupting the direct current, the contractions of the muscles
of the limbs are feeble, but there are signs of pain, and the muscles  of  the back are
contracted;  but, when the direct current is closed, the effects are limited to contrac-
tions of the  posterior limbs.  When the inverse current is  used, contractions of the
muscles of  the back and signs of pain occur on closing it, while the contractions of
the limbs are slight; but, on the interruption of it, contractions of the limbs alone take
place.
  The following tabular view will  exhibit these latter results more clearly.

                                            contractions in muscles  of posterior
                                              limbs.
                                            marked signs of pain, and contraction
                                              of muscles of the back.
                                            feeble contractions of posterior limbs.
                                            signs of pain, contractions of muscles
                                              of back, and feeble ones of the pos-
                                              terior limbs.
                                            contractions of the posterior limbs.

  So that, after the lapse of a little time, the phenomena produced by closing  the
inverse current, become precisely the same as  those on opening the direct, and vice
versa.
  The contractions  of the muscles  of the back, which are supplied from nerves which
come off above the  point of excitation, are due to the irritation of the nervous centre,
affected through sensitive nerves ;  for these contractions cannot be produced if the
portion of the cord  from which the nerves arise have been removed.
  After the  nerve has been exhausted, so as  to  yield the phenomena of the second
period, as shown in the table, it may be excited  to act as at first, either by increasing
the intensity of the current, or by exciting points of the nerve nearer its peripheral
extremities.
  A simple  experiment illustrates  the different effects  of the direct and inverse cur-
rent in a very striking manner.  The limbs of a frog are prepared according to  the
ordinary method of Galvani.  If  a current be  passed from one side  to the other
through the  lumbar nerves, it is plain that it will be direct in the nerves of one side,
and inverse  in those of the other side. During the first period, there are contractions
both on completing and interrupting the circuit; but in the second period, one limb
contracts on opening, the other on closing, so that the  limbs are made to kick alter-
nately, that which is traversed by the direct current on closing, and that by the inverse
current on opening.
  It is impossible  to observe these curious phenomena, whether of the  muscular
current, or of the effects  of electricity on nerves, without  perceiving how utterly in-
explicable they are by the electrical theory of nervous power, or, indeed, how much
opposed they are to such  a view.  They serve, in  the  most remarkable  manner, to
confirm the views which we have  advocated in  a former  chapter, which regard  the
nervous power as a polar  force developed  by molecular changes  in  nerves excited
by various stimuli, of which, next to the  mental, that of electricity is the most power-
ful.
  We  have  already (p. 223) given the general results  of Professor Matteucci's very
interesting series of experiments on the torpedo.  We shall content ourselves, now,
with remarking that he has succeeded in illustrating very strikingly the marked ana-
logy between the actions of the electrical organ  and those of muscle, and the relation
which  each bears to the nervous system. Both are organized to act in a particular
way:  the one to develop electricity without any visible change  in itself;  the other
to contract, with a demonstrable evolution  of both  heat  and electricity.   Both will
manifest their peculiar phenomena by direct irritation, or by indirect irritation through
the nerves.  Both are  brought under the control  of the will by the nerves  ; the section
of which paralyzes the influence of the will over both, but does not destroy the  pe-
culiar  power of either.  In the  electrical fish, irritation of  the electrical lobe of  the
                      .closing
Direct current .  .   .  <
                      ( opening

                      C closing
Inverse current .  .  .  ?
     t                (opening 
   SYMPATHY AND SYMPATHETIC SENSATIONS* AND MOTIONS.  339

brain is capable of exciting a discharge of the organ ; just as irritation of a segment
of the spinal cord causes  contraction  of the muscles supplied by it. A current of
electricity transmitted through  the electrical organ or its nerves, causes discharge;
and a similar current sent through a muscle or its nerves, causes it to contract.  All
the circumstances which modify the nutrition of muscle, will similarly affect that of
the electrical organ.*
                         CHAPTER XII.

      ON SYMPATHY AND SYMPATHETIC SENSATIONS AND MOTIONS.

   It is popularly known that the  act of yawning, performed by one
 individual in a company, is apt to induce  in  many of the others an
 irresistible tendency to the same act.   In a similar manner, the ex-
 citement of certain emotions (mirth or sadness, laughter or tears) is
 apt  to  spread through an  assemblage of persons with extraordinary
 rapidity.   The power of eloquence, of music, or of spectacle, to pro-
 duce such effects, is witnessed every day in places of public  resort,
 whether for devotion, business, or amusement.
   Many instances are  known in which  convulsions have been ex-
 cited in persons not previously subject to them, by the  sight of a
 patient in an epileptic fit.   And peculiar nervous disorders, of a con-
 vulsive kind, have been found to  affect nearly all the members of a
 community, without the slightest evidence of their being contagious
 or infectious.   An  impression upon  an organ of sense may produce
 effects very different in their nature to anything  which could be anti-
 cipated ; and these  may be purely of a  physical  kind, or they may
 act primarily upon the mind.  Thus  certain odours will induce syn-
 cope in some people; and  the smell  of a  savoury dish  to a  hungry
 person, or even  the  mention or the thought of a meal, will  excite a
 flow of saliva.   The emotion of pity excited by the sight of some
 object of compassion, or  by a narrative of a mournful  kind, will pro-
 duce a copious flow of tears.
   All such  phenomena  are  said  to  result from Sympathy.    When
 one  yawns, immediately  in consequence of another's yawning, the
 former  evidently and  truly  sympathises  with  the  latter ; and the
 convulsions which are  induced by the sight of  another in a fit, are
 not less sympathetic.  The individual in whom the convulsions are
 induced sympathizes with  the other.  Such obvious instances  of
 sympathy between  different individuals  led to the supposition  of
 some such similar consent between different or even distant parts in
 the same person.
  Motions or sensations caused in certain parts in  consequence of a
 primary irritation of  other  and distant parts are of the  sympathetic
 kind.  These motions or sensations  are  produced in, as it were,  an

  * Traite des phenomfenes electro-physiologiques des  animaux, par C. Matteucci; suivi
 d'etudes anatomiques sur le systfcme nerveux  et sur I'organe electrique de la Torpille, par
Paul Savi.  Par. 1844. 
340                      INNERVATION.
indirect or circuitous manner, or  one different from that in which
they are ordinarily excited.
  Thus a  stimulus  to  the olfactory  membrane  causes  a peculiar
affection of the sense of smell, and thus occasions that depression of
the  heart's action from which results a  state of syncope.   Or, another
affection of the same sense causes  a suddenly increased action of the
salivary glands.
  If we analyze any one of these examples of sympathetic actions, it
will appear that three circumstances are to be  noticed in the produc-
tion of the phenomena: 1st, the primary  exciting cause,  which may
be  an object presented to the mind  through one  of  the organs of
sense, or causing an impression upon any sensitive nerve, and there-
fore upon some part of the centre of sensation ;  2dly, the part affected
directly by this primary stimulus;  and, 3dly, the  action or sensation
resulting from the affection of this part.
  Many  other  sensations  or  motions may be enumerated besides
those above  referred to, whether  occurring in health or in disease;
and we shall give examples of these before we discuss this subject
further.
  The examples of sympathetic sensations which may be adduced
are chiefly of the morbid kind.   Pain is felt at a certain  part, in
consequence  of an  irritation in another part distant from it, and ap-
parently altogether unconnected with it.   One of the most familiar of
these is pain in the  knee  from disease of the  hip-joint.   So marked
in some instances is the pain in the knee, and so much has it absorbed
the patient's attention, that the real  seat of  the disease has been
overlooked, and the remedies  been applied exclusively to the knee.
Pain  in the right shoulder from disease of the liver is  a sympathetic
sensation of similar kind ; and  sometimes the hepatic irritation causes
pain  over a more extensive surface.  Whytt  mentions, that, in two
cases of suppuration of the liver,  he had seen  the patients " affected
with  a numbness  and debility of  the right  arm, thigh, and leg."
The  peculiar sensations felt in the teeth from a  noise which grates
upon the ears, is sympathetic of the irritation of  the  auditory nerve.
Practitioners  are well  aware how  many  morbid  sensations  in parts
remote  from  the intestinal canal  may be cured  by the  removal of
scybala or other accumulations from  it.  Painful affections of the
nerves of the face,  and of other  parts, are often due  to a cause of
this kind.  The irritation of a stone in the bladder gives rise to pains
in the thighs, or to itching at the end  of  the penis ; and uterine irri-
tation, whether from disease or from the enlargement of that organ in
connection with the early stage of pregnancy, causes similar pains in
the nerves of the thighs.
  Headache  and defective  vision  are frequently produced by disor-
dered stomach.   A  draught of very cold  water, or ice, taken quickly
into the stomach, may occasion acute pain  in the  course of either
frontal nerve.  This same nerve on one side is frequently the seat of
pain  after the imprudent use of acid wine or other fermented liquors.
   Movements, excited by the  operation  of a  stimulus applied at a
distance,  form a large proportion  of the  instances of sympathetic 
SYMPATHETIC MOTIONS.
341
phenomena.   All  the ordinary physical  nervous  actions  in  which
motions  are  excited  by stimulating a sentient surface,  may  be re-
garded as  examples  of sympathetic actions.*  The  contraction  of
the iris upon the application of the stimulus of light-to the retina, or
of the pharyngeal  muscles by stimulating the mucous membrane of
the fauces, are instances in point, where the stimulus acts indirectly
upon the contracting fibre.  Nothing is more sure than that in these
instances the change wrought by the stimulus in  certain sentient
nerves travels by a circuitous route through a nervous centre to the
muscles which  are called into action.  Akin to these actions are the
forcible respiratory movements which may be excited by irritation of
the tracheal  membrane, as coughing ; or sneezing, by stimulating the
nasal membrane; or vomiting, by irritating the fauces.   Spasmodic
affections  are  often  instances of  morbid actions in sympathy with
intestinal irritation, or the irritation of teething in children.   Partial
or general convulsions are very frequently due to  either or both these
causes.  We have known the most violent opisthotonos  co-existing
for a considerable time with the presence of lumbrici in the intestine;
but ceasing immediately on  the removal of  the worms.  Vomiting is
commonly sympathetic of diseased kidney, or of the passage  of a
calculus along  the ureter; or it may be  induced  by the  introduction
of a catheter into the urethra.   Irritation of the  intestines, as in
cholera, causes cramps of the most violent kind in the lower extremi-
ties  and abdominal  muscles.  The contractions  of the abdominal
muscles in parturition, although  materially aided by the will, are in
consent with the expulsive efforts of the  uterus.
   The consentaneous action of symmetrical parts is no doubt due to
a similar cause to that by which most of the sympathetic actions are
excited, and more especially in those parts where symmetry of action
is constant,  although  liable to be interrupted by the influence of the
 will.
   A distinct class of sympathetic  actions consists of those in which
 certain parts enlarge or become  developed  simultaneously with, and
 to a  certain  extent in effect of, the increase of others.   The penis,
 the beard, the vocal  organs, experience a marked increase of de-
 velopment at the adult period of life simultaneously with the  enlarge-
 ment of the testes ; and, it may be added, in effect of their increase,
 because the early removal of these organs prevents the growth of the
 others.  And so likewise as the ovaria are developed, the uterus, the
 vulva, the mammas, increase  in size;  the ovarian and uterine irrita-
 tion  which accompanies the menstrual flux causes enlargement of the
 breasts, which subsides as-soon as that period has gone by.
    The various examples  enumerated  in  the  preceding paragraphs
 maybe  classed under three heads: first, sympathies between  different
 individuals; secondly, those which  affect the mind, and, through it,
   * It has been remarked, that the term "sympathetic actions" involves a contradic-
 tion.  But it may be observed, that the  contraction of  the muscles, on  which the
 action depends, is only the natural mode  in which  that class of vital organs can
 manifest their consent with certain states of nervous centres, or of sensitive nerves.
 The action is the result of the state which the muscle assumes in sympathy with the
 stimulated nerve. The contradiction is therefore apparent, not real. 
342
INNERVATION.
 the body; and, thirdly, those which  are  strictly organic, and there-
 fore physical.
    Of  the first class of sympathies we can offer no physical explana-
 tion.  Whether'the  nervous system of one  individual can directly
 affect  that of another, or  whether the  effect is produced on the ima-
 gination, and afterwards  on the nervous  system, are questions  still
 sub judice.   The serpent  fascinates his prey, apparently by the power
 of his eyes, and it is well known that one man can exert a marked
 control over another by a mere look;  and in the same way man  can
 control other animals, even  the fiercest carnivora, by a firm  and de-
 cided  glance of the eyes.   It is no explanation of sympathetic  pheno-
 mena  of this kind to ascribe them to the effect of a tendency to imita-
 tion.   Imitation is voluntary; these actions  are involuntary,  or take
 place  even  in despite  of the will.  (Bostockh Physiology, vol.  iii.,
 p. 227.)
   In the second class of sympathetic phenomena, an affection of the
 mind is a necessary link.   But why that affection  of the mind should
 produce its  peculiar  effect is a question of difficult solution.   Why
 should the perception of certain odours produce in one case increased
 action of the salivary glands, and in the other case cause syncope?
 The only reply which can be made to this question is, that in these
 instances the impression  on  the sensorium  causes a change there
 analogous to that which an original affection  of the mind of  similar
 kind would produce, and therefore gives rise to effects of the same
 nature as those resulting  from that mental change.   Thus the smell
 of  savoury food excites in the mind  the  idea  of food, which in a
 hungry man  would, if it occurred spontaneously,  occasion a flow of
 saliva.   And the odour which occasions syncope, creates in the mind
 an  emotion of disgust, which, if it arose independently of the physi-
 cal impression, would affect the heart through the  centre of emotion.
 It is plain, however, that that portion of the nervous centre  which
 is affected in such cases, must have a direct influence upon the parts
 in which the sympathetic  phenomena appear; and this through com-
 missural  fibres, or the continuity of its gray matter with that of the
 centre  from  which its nerves immediately spring;  thus, in  the  in-
 stances referred to, the centre of  sensation, which  is first affected, is,
through the  medulla  oblongata,  connected with the  salivary  glands
by the  fifth nerve, and with the heart by the  vagus.
  We  derive an explanation of the  third class of sympathetic phe-
nomena from the  known laws of  sensitive and motor nerves.   It is
known that stimulation of a sensitive nerve at its origin, or in any
part of its course,  will give rise to a sensation which will be referred
to the peripheral extremity of the  stimulated fibres; and that a  stimu-
lus applied to a  motor  nerve causes  a change in it  which spreads
peripherad from the point  stimulated, and therefore affects the muscu-
lar parts with which it is connected. It is known, also, that a sentient
nerve may excite a motor  or sensitive nerve which is  implanted near
to it in the nervous centre—doubtless through the change which it
produces in that centre; nor can it be doubted that a sensitive nerve
may receive  such  a powerful stimulus as  to  exalt the polar force of 
SYMPATHETIC SENSATIONS AND MOTIONS.         343
a large portion  of the nervous centre  in the neighbourhood of its
insertion, and thus to excite a  similar change  in  all the  nerves,
whether motor or sensitive, which  are connected with it.   Thus,
according to  the  intensity of the original stimulus, there will be a
radiation of nervous force  from the centre,  either in one  or two
motor or sensitive nerves, or in several such; and  the number and
variety of the sympathetic phenomena  will  thus depend on  the in-
tensity and extent of the change in the nervous centre  excited by the
primary stimulus.
  To explain then the  phenomena  of sensation and  motion under
consideration, we  must  determine the individual  nerves  affected in
each  instance, and ascertain what connections they have  with each
other.   We learn from anatomical investigation, that, although nerves
anastomose  with each other in  their distribution, this anastomosis is
by no means  of that  kind which would justify the supposition that
an irritation could be communicated from one to the  other  in their
course.  The nerve-fibres only lie in  juxtaposition, but do not com-
municate: and there is an evident provision in the tubular membrane
and  white  substance of Schwann for  the  insulation  of the  central
axis,  which is probably the  effective substance in the nervous action.
We must seek, therefore, in the nervous centres for such a communi-
cation between these nerves as may explain  the excitability of one by
the other.  In the present state of our knowledge we can do no more
than state it  as in the highest degree probable that nerves implanted
in the centre immediately contiguous to  each other can  exert an influ-
ence upon the vesicular  matter of the centre, and upon each  other.
  But there are certain facts which demonstrate  beyond all doubt,
that, in such actions as we refer to, the  integrity of the centre  forms
a necessary condition.  First, in many of the instances,  it is plain that
there can be  no connection between the affected nerves  elsewhere
than in the  centre, for they are so distinct from each other that there
is not even that  apparent connection which results from the anasto-
 mosis of a fasciculus of  fibres of the one with a portion of the other.
 Secondly, the  removal  of the portion  of the nervous centre  with
 which any one of the nerves concerned in  the sympathetic action is
 connected,  will prevent  the  development  of the phenomenon, al-
 though the  nerves themselves remain  uninjured in  their  peripheral
 distribution, or in  their connection with each other.  Thirdly, if there
 were any  peripheral communication between nerves, it would be
most likely to take  place  in  the plexuses.   Experiments, however,
 upon the nerves which lead to these show that each nerve-tube, in its
 passage through them, retains its isolation as distinctly as in any other
 part of its course.  The three  nerves  which supply the  lower  ex-
 tremity in the frog, says Muller, form a plexus from which two  nervous
 trunks  issue : if one  of  these latter be divided and isolated from all
its connections with muscles, and the portion of it connected with the
plexus irritated, the impression will be transmitted in  the centripetal
direction by the sensitive fibres of the nerve ;  but the motor  fibres of
the other nerve arising from the plexus are not affected,  and excite 
344
INNERVATION.
 no contractions in the muscles to which they are distributed.  {Baly's
 Muller, vol. i. p. 756.)
   In  applying these principles to the  explanation  of the instances
 which we' have quoted, we  shall find  it difficult  to determine the
 central connection in  some, although in  others such a connection is
 highly probable.  It remains, therefore, for future anatomical research
 to ascertain what that  connection is which enables one nerve  to sym-
 pathize  with  another.   In  the  instance of pain  in the  shoulder  in
 sympathy with irritation of the liver, the hepatic irritation excites a
 change  in some  sensitive nerves, which is propagated to the centre,
 and there affects some of the sentient fibres  distributed in the region
 of the shoulder.  The phrenic and the external thoracic nerves  are
 both  or either of them, but  more especially the former, favourably
 situated to constitute  the  excitant  of such  a  sympathetic sensation.
 The  phrenic  nerve  of the right side is largely distributed upon the
 peritoneal  surface of the diaphragm, and upon  the inferior vena cava,
 and forms  many connections with the hepatic plexus in the substance
 of the liver.  It may  therefore  readily participate in any  irritation of
 that organ.   Now the phrenic nerve is  implanted in the  spinal cord
 on a level  with the third or fourth cervical nerves; and the nerves of
 the shoulder form their connection  with  this central organ about the
 same level.   The origins of these  nerves are sufficiently contiguous
 to each other  to warrant the belief that an irritated state  of one may
 be propagated to the other through the vesicular matter of the centre.
 But  it maybe inquired why the  irritation is limited to sensitive nerves
 of the shoulder; and why movements are not excited by  the stimula-
 tion of the motor  fibres  of the phrenic itself, or of other  nerves?
 The limitation of the  irritation to one or two nerves depends  on the
 degree of  the stimulus,  and the absence of  movements is  due to
 the disposition of the  phrenic on the  surface being unfavourable for
 the excitation  of  motions by irritation of its peripheral branches (see
 page  298).  And the  experiment cited from Muller, in the last para-
 graph, shows  that simple irritation of the trunk of a compound nerve
 in connection with the centre  is not sufficient  to produce motion;
 which requires probably either a more prolonged and violent  irrita-
 tion  of the  nerve, or  a polar state of the centre in which it is  im-
 planted.
  Some  of the instances of sympathetic sensations, referred to  above,
 do not admit of an explanation so obvious.   The pain over the brow,
 from ice  or cold water in the stomach, may be referred  to irritation
 of the gastric  branches of the vagus, communicated  in the medulla
 oblongata to the filth ;  but why the irritation  should  be limited to the
 ophthalmic division of the fifth, cannot be accounted for in the pre-
 sent  state of our knowledge.
  In  those sympathetic movements which are of ordinary and nor-
 mal occurrence, two provisions seem to be secured, namely, a certain
 peripheral organization of the excitor nerve,  and a certain central
 relation between it and the motor nerve.  But  in those which are of
a morbid kind, it is necessary to suppose the existence of a more  or
less exalted polarity of the centre, in order to explain the  phenomena 
PACINIAN CORPUSCLES OF THE NERVES.           345
fully.  This polar state will  continue, in many instances, even after
the primary peripheral irritation has been removed, as  in  tetanus, or
in the convulsions from intestinal irritation ; and we learn from this
fact the importance in practice of attending  to the state of the nerv-
ous centre, as well as to the  removal of the irritating cause.
   There are other sympathetic phenomena, of the physical kind, in
which, however, the nervous  system does not appear to take a pro-
minent part.  Such are  the changes which occur in  different and
distant organs in connection with  a  particular  period  of life, or the
development of a particular  function.  Among these, are the pheno-
mena of puberty in  both sexes; the enlargement of the mammse in
pregnancy.   Whatever part the  nervous system may take in such
changes, it is impossible to account for them by reference to that sys-
tem only; they must rather  be regarded as phenomena of nutrition
occurring in harmony with the laws of  growth, and therefore  affect-
ing the vital fluid more  particularly than  any part of the system of
solid parts.
   Continuity of texture disposes, as  is  well known, to the  extension
of a diseased state originating  at some one point.  So also does con-
tiguity.   Phlegmonous inflammation of the areolar tissue, and ery-
sipelas in the skin, spread with great rapidity.    Inflammation arising
in one of the opposed surfaces  of a serous membrane, readily attacks
the other.   These effects have been vaguely assigned  to  sympathy,
(the continuous and contiguous  sympathy of Hunter.)   But it cannot
be supposed, that the nervous system takes  part in the  production of
such phenomena, which ought rather to be  ascribed, in the one case,
to the continuity of  blood-vessels,—and, in the  other, to contamina-
tion either by effused fluids or by morbid blood.

  On the subjects referred to in this chapter, consult Whytt on the  Sympathy of the
Nerves, an admirable exposition of the phenomena, obscured, however, by his erro-
neous views respecting  the all-pervading influence of the  mind upon vital pheno-
mena;—Hunter on the Blood, &c.;—Alison on the Physiological Principle of Sym-
pathy, Edin. Med. Chir. Trans., vol. ii.;—Miiller's Physiology.
                        CHAPTER  XIII.

            OF THE PACINIAN CORPUSCLES OF THE NERVES.

  We propose to  give in  this  chapter an account of certain very
remarkable structures,  appended  to  the nerves, to  which attention
has only very recently been drawn in this country.*  These  are  the
Pacinian  corpuscles, so named by  Henle and Kollikerf from their

  * Brit, and For. Med. Rev., Jan. 1845.
' f Ueber die PacinischenKorperchen an den Nerven des Menschen und der Siiuge-
thiere.  Zurich, 1844.
       23 
346
INNERVATION.
discoverer, Pacini.*   In the human subject they are  found in  great
numbers, in connection with  the  nerves  of the hand  and foot, the
nerves, as it may be  presumed, of touch  ; but  they also exist spar-
ingly on other spinal  nerves,  and on the plexuses  of the sympathe-
tic, though never on the nerves of motion.  In the  mesentery of most
cats they are very readily seen by the naked eye, (usually in  consider-
able  numbers,) as  pellucid, oval grains, rather  smaller  than  hemp-
seeds, and they are here  very  favourably situated  for  examination.

                                 Fig. 74.
 a. Nerve from the finger, natural size; showing the Pacinian corpuscles.
 b. Ditto, magnified 2 diam ; showing their different size and shape.
 c. Unusual form, from the mesentery of the cat; showing two included in a common envelop:
—a. b. are the two nerve-tubes belonging to them.
 d. Another, from the same : showing an offset from the central cavity, containing a branch of the
paie nerve.
 e. Rare form, from the mesentery of the cat (reduced from Henle and Kolliker); showing two cor-
puscles placed in succession on a single stalk, and furnished with the same nerve-tube, which re-
sumes its white substance in the interval between them.
Fig. 74, a, b, will give a correct idea of their relation  to  the nerves
in the palm and sole.  They are  especially numerous on  the smaller
twigs, to which they are  generally placed parallel, though frequently
at an acute, and sometimes at  an obtuse  angle.  They are  more  or
less oval, often elongated and bent;  sufficiently tough to resist mode-
rate pressure, and nearly transparent, with a  whitish line traversing
their axis.   They lie imbedded in the areolar tissue, and  adhere to it
by their outer surface.  They always  present a proximal end, attached
to the nerve by a stalk of fibrous tissue, prolonged from  the neuri-
lemma, and occasionally  TV of an inch long;  and a distal end, lying
free in the areolar tissue.  The corpuscles in the human subject have
an average length of from ^V to TV of an  inch.

   * Pacini first noticed them in 1830, and subsequently in  1835 ; and in 1840 gave an
account of them (Nuovi organi scoperti del corpo umano dal Dott Fillippo Pacini.
Pistoja, 1840), which has been rendered much more accurate and complete in its de-
tails by Henle and Kolliker.  Coming to the investigation of these corpuscles  with
the knowledge of what these eminent  anatomists had  accomplished, we have con-
firmed their results by numerous observations, from which the account about to bl
given has been principally taken. A. G. Andral, Camus, and Lacroix had announced
their existence at a concours in Paris in 1833, but do not appear to have apprehended
their real nature. 
PACINIAN BODIES.                      347
Pie. 75.
   A minute examination of these singular bodies discloses an internal
 structure of a highly interesting kind.   They consist, first, of a series
 of membranous capsules, from thirty to sixty or more in number, en-
 closed one within the  other; and, secondly, of a single nervous fibre,
 of the tubular kind enclosed in the stalk, and advancing to the central
 capsule, which it traverses from end to end.
   By reference to the accompanying figure (75), which exhibits the
 general structure,  the  ten  or fifteen innermost capsules   may be ob-
 served to  be in contact with one  another, while the rest are separated
 by a clear space containing fluid.  This is almost constantly observed,
 unless the  specimen has  been allowed to  imbibe  water  sufficient to
 detach the  inner capsules from  each other ;  and hence  these  have
 been distinguished from the rest as
 the system of internal capsules.  The
 intercapsular spaces between  the
 others  vary in  width, especially
 under pressure, and sometimes we
 have seen  some of the outer capsules
 in close contact.   The capsules are
 here and there united by connecting
 bands  of  similar structure, passing
 transversely or obliquely across the
 spaces; the spaces do not commu-
 nicate: if some of the outer capsules
 are punctured, their fluid  escapes;
 but  those within remain distended.
 A single  puncture  down  to  the
 inner series  of  capsules  causes all
 the fluid to  escape,  and the  whole
 to collapse;  and again, the capsules
 may be often peeled off in succes-
 sion, showing their union to  be but
 slight.  In fact, except by the few
 bands  already mentioned, they are
 united  only along the stalk, and for
 a  variable extent at  the  opposite
 end. The stalk seems to be inserted
 into a kind of conical  tube, which
 penetrates all the  capsules in suc-
 cession, but has its proper wall, so
 as  not to  communicate  with the
 intercapsular spaces.   This  wall
 connects   the  capsules,  and  the
 fibrous tissue of the stalk is gradu-
 ally  united  with  its inner  surface
 as far as the central  capsule, where
 it terminates.  There is generally a
strong union between a variable number of  the capsules, as we trace
them from  the opposite end of the central capsule towards the surface
(fig.  76, b, o); this was  called by Pacini  the intercapsular ligament.
 Pacinian corpuscle, from the mesentery of a
cat; intended to show the general construction
of these bodies. The stalk and body, the outer
and the inner system of capsules, with the cen-
tral eavity, are seen. a. Arterial twig, ending
in capillaries, which form loops in some of the
intercapsular spaces, and one penetrates to the
central capsule, b. The  fibrous tissue  of the
stalk  prolonged from the  neurilemma,  n.
Nerve-lube  advancing to the central capsule.
there losing its white .substance, and stretching
along the axis to the opposite end. where it is
fixed by a tubercular enlargement. 
348
INNERVATION.
We do not, with Henle and Kolliker, deny its  existence, but have
seldom seen it reach the surface of the corpuscle.
   The wall of the  capsules  of the external system often  appears to
consist of two laminae.   The  inner  of these contains, at  intervals,
flatfish, oval nuclei projecting inwards (fig. 76, a, d).   The outer is
sometimes seen, as if in  section, by a series  of dots, representing
transverse or circular fibres.  The capsules always exhibit a decided
transverse fibrillation, which in a great measure disappears  on the
addition of acetic acid,  showing the  almost complete absence  of the
yellow  fibrous tissue.   The outermost capsule  of all, however, is
invested with the network of this, as  well as of the white fibrous ele-
ment of the areolar tissue.   The  internal capsules do  not show the
double wall, but they contain nuclei.
   The capsules seem to  be over-distended by their fluid, so as to  be
naturally kept  tense.   If allowed to  dry, they do not  fill again  on
being moistened.
   The fluid of the intercapsular spaces is so abundant as to constitute
far the largest portion of the bulk of  the entire corpuscle, and by  its
clearness imparts the peculiar pellucid lustre so characteristic of these
bodies.  It is supposed to resemble the serum of the blood.
   There are generally a  few  capillary blood-vessels ranging over the
surface of the capsules;  but  the  corpuscles are chiefly  supplied by a
minute artery that enters in the  fibrous tissue of the stalk, sends off
a few capillaries which perforate  the  tubular canal, and form each a
short loop in the intercapsular  spaces (fig. 75):  one capillary  vessel
usually reaches the central capsule (fig. 76, a), and sometimes, though
rarely, may be  traced some way along its wall.   In  the larger cor-
puscles of the  palm and sole, the capillaries penetrate  to the  distal
part of some of the intercapsular spaces, and may there form  a kind
of bunch before returning.   If a quite recent specimen  be  examined,
under a high magnifying power, the blood-globules are often  visible
in the capillaries, and, by their swelling on the  addition of water,
may be sometimes  hurried  into  a sort of  circulation.  When this
happens, the course of the blood in the corpuscles is displayed with
singular beauty.
   We have  said that the stalk of every corpuscle contains a  single
nerve-tube.  When two corpuscles  are seated on a common  stalk,
two nerve-tubes  are  included, one of which  belongs  to  each (fig.
74, c).
   The nerve-tube is proportioned in  size  to that of the  corpuscle,
that is, to the number of capsules composing it.   Even when smallest,
it is conspicuous enough, if the specimen be recent; for it is invaria-
bly furnished with the white substance  of Schwann, and displays the
double contour.  When  largest, it equals any found in  the body.  It
is very liable to present varicosities,  and its course  in the stalk  is
more or less undulating.
   On entering  the innermost capsule, the nerve-tube suddenly loses
its envelop  of  white substance and becomes pale; the  axis-cylinder
alone remaining, perhaps still invested by the tubular membrane (see
p. 194).  Thus reduced  in size and rendered pale, the nerve stretches 
PACINIAN BODIES.                       349
 like an arrow along the  very centre of the  capsular  cavity to  the
 opposite  end, where  it  swells into a knob, or  button, which fixes
 itself to the inner  surface of the capsule.   In this swelling nothing
 can be detected beyond  the pale, faintly fibrous character of the axis-
 cylinder.   No nucleus, like
 that of the caudate  nerve-
 vesicles,  can  be  seen.—
 Sometimes the  axis-cylin-
 der divides near its  termi-
 nation into two or even into
 three   branches,  each  of
 which terminates by an ad-
 herent  swollen   extremity.
 Sometimes this division oc-
 curs near the  proximal end
 of the central capsule, and
 one of  the  branches  passes
 in a retrograde course into
 a subordinate offset from the
 central cavity,  and   there
 terminates  (fig. 74, d).   In
 the midst of these varieties
 one thing is constant, viz.,
 the  remarkable   accuracy
 with which the  pale  nerve
 pursues its  path in  the axis
 of the  cavity, everywhere
 equidistant  from the  walls.
 This is  most apparent when
 the cavity is bent upon itself,
 and when it might be  imag-
 ined that the  nerve would
 incline  from the centre  to-
 wards  the  concavity of the
 bend; but it keeps a central
 course there as well as else-
 where.  This,  perhaps, may
 depend on the   nature  of
 the contents of the central
 cavity,  immediately envel-
 oping the pale nerve.   Near
 the wall  of the  cavity an
 appearance of soft, delicate,
 longitudinal fibres, with elongated nuclei, is  often visible (fig. 76, a) ;
 and although the  space immediately surrounding  the nerve is quite
 transparent, we are disposed  to consider the substance occupying it
 sufficiently solid  to keep the nerve in its place.   It does not seem  to
 be mere fluid,  like that distending the intercapsular  spaces.
   Henle and Kolliker  have remarked, that, where two  corpuscles are
seated in succession on a  single stalk (fig. 74, e), the pale axis-cylin-
  a. Termination of the stalk, and commencement of the
central cavity, n. Nerve-tube advancing to the central
capsule, and there suddenly  losing its white substance
and becoming pale. a.  Artery ending in  capillaries;
one of which enters an intercapsular space, the other
advances with the nerve into  the inner capsule,  b. Coni-
cal tube which receives the  stalk : the fibrous tissue of
the stalk is not represented,  c. Wall of this tube, con-
tinuous with the successive capsules, here seen in section.
d. Corpuscle  of the capsular wall,  e  More spherical
granular corpuscle, of which a few only exist.
  B. Distal end of the central cavity,  n. Pale nerve ad
vancing along the axis, to be fixed by a swollen part at
the further end.  c. Wall of the central cavity, receiving
the insertion of some of the neighbouring capsules, here
a little separated from each other by water, o. Intercap-
sular ligament of Pacini, continued a  little way towards
the surface.
  c. Two varielies of bifid extremity of nerve, attached to
the distal extremity of the central cavity.— All magnified
320 diam.                              5 
350
INNERVATION.
der regains its envelop  of white substance from its point of leaving
the central cavity of the first, to its entering that of the second; and
that in  some cases, where the central cavity is bent suddenly upon
itself, so that it cannot be  fairly surrounded  by capsules at the  bend,
it  is there provided for a little way with white substance.  A very
delicate layer of the same  substance, just thick enough to give a dark
edge, occurs occasionally  along the course of the pale fibre.
   We have  gone  thus minutely  into the structure of the Pacinian
corpuscles,,because  of  the  novel  aspect in which they present  the
constituent parts of the nerve-tube, placed  in the heart of a system
of concentric membranous capsules with intervening fluid,  and  di-
vested of  that layer which we  regard as an isolator  and protector of
the more potential central  axis within.   The object of this arrange-
ment is quite unknown, and in the present  uncertain  state of our
knowledge respecting the nature of the nervous force, it seems almost
idle to  hazard guesses  on  the subject.   The apparatus of lamellae
may either effect some  change in  the enclosed nerve, by which the
nervous centres  in connection with it may be influenced as  to their
polarity ;  or, on the  other hand, this  apparatus may be the special
instrument of some peculiar vital agency, which the nervous filament
is  designed simply to bring into  communication with  the  nervous
system.  The latter view, to  which we  incline, would bring these
organs under the same  category with muscles, and the  organs which
develop light  or electricity in certain of the lower  animals.   Pacini
has already drawn a comparison, in point of structure, between them
and the electrical organs of the torpedo ;  and Henle and Kolliker
favour this idea.   The well-known prisms of the  electrical organs,
according to  Savi,* consist of a congeries of very delicate transverse
lamella?, on which the  nerve-tubes are  distributed  in  a  plexiform
manner; and, if we  may judge from his figure, this plexus is not
resolvable into loops, but consists of true inosculations of the  ultimate
tubes, which also retain the white  substance  of Schwann: but further
researches are greatly needed  on  this  point.  Wagner, with  more
probability, describes the  nerves to  terminate on the lamellae in  the
same looplike  manner  as  in  striped  muscle.f  These lamellae  are
separated  by fluid, and  only adhere  through the medium of  the wall
of the prism.   If this be the true history of this structure, it appears
to establish some general analogy between the electrical organs and
the corpuscles ; but how  far this  can  be shown  to  hold in essential
characters, especially in the mode  of termination of the nerves, and
their arrangement with  regard to the membranes and fluid, is still a
matter of doubt.  Meanwhile  we deem  it  most prudent  to forbear
from speculating concerning the office of the Pacinian corpuscles.
  Having thus far completed  the physiological  anatomy and phy-
siology of nerves in general and nervous  centres, we proceed next

               * Paul Savi, in Matteucci, loc. cit.
               j Comparative Anat., translated by Tulk. 
GENERAL REMARKS ON SENSATION.
351
to the consideration of particular nerves; and we shall state here the
order in which we find it  convenient to examine  them.   The Ence-
phalo-spinal  nerves  very conveniently arrange  themselves  into the
three following  classes:—I.  The nerves  of pure  sense.   II. The
nerves of motion.   III. The  compound nerves.  The first  class in-
cludes some nerves, namely,  the  nerves  of touch  and taste, which
are mixed up with those of the third class;  but, as the consideration
of these  senses could not without  great inconvenience be separated
from the others, we prefer to consider these particular  fibres  along
with the other nerves of pure  sense, namely, the olfactory, the optic,
and the auditory.  As the peculiar function  of these  nerves  depends
upon their peripheral organization, as well  as on their central con-
nection,  their physiological anatomy involves necessarily that of the
organs of sense.  We shall commence with  the most simple, namely,
Touch and  Taste, and afterwards proceed to  Smell, Vision, and
Hearing.
   The second class of nerves contains the third, fourth, sixth, portio
dura of the seventh, and the ninth pairs of nerves according to Willis's
arrangement, all of which are motor in function.
   In the third class we place the fifth and eighth pairs of nerves, and
the spinal nerves.
   Lastly, we shall examine the Sympathetic nerve.
                        CHAPTER  XIV.

GENERAL REMARKS ON SENSATION.--OF THE SPECIAL SENSES.--OF THE
   SENSE OF TOUCH.--ANATOMY OF THE SKIN, AND ITS APPENDAGES.

  Sensation is an affection of the mind occasioned by an impression
made on certain parts of the nervous system, hence called sensitive.
A state of the  sensitive  organs, and  a  corresponding perception by
the mind, must concur  to produce  sensation: either  condition may
exist alone, but then the phenomenon is not a true sensation, in the
acceptation here given to the word.   Thus, light falling on  the eye
in sleep excites the whole visual sensitive apparatus, while the organ
of perception is inactive: on the other hand, in dreams, vivid pictures
of objects float before the mind, and are referred  by it to the  external
organ, which may be all the while entirely quiescent.
  The  organs  of sensation are those parts of the nervous system,
and their  dependencies, which,  when  stimulated, occasion in the
mind a perception of the  impression.   Hence certain  parts of the
cerebro-spinal  centre, as well as  certain nerves  and their peripheral
expansions, are comprehended under this term.  It is remarkable that
the organ of the mind itself does not  appear  capable of thus under-
going  sensory excitement.   Little is  known of the central parts of
the organs  of  sensation, in consequence of  their deep  seat, and of 
352
INNERVATION.
their ill-defined limits.  The peripheral parts are more conspicuously
placed, and on several accounts are  commonly styled, par excellence,
the organs of sensation: they are specially adapted to receive  in the
most advantageous manner the impressions to which their excitability
is  adapted to  respond.   The intervening  nerves are, more properly
speaking, media of transmission.
   Sensations excited by a  stimulus originating in  the  body itself,
especially if it  act rather on the intermediate or central part of the
sensitive apparatus than on  the peripheral, are termed subjective: on
the other hand, they are styled objective if the  stimulus  be  derived
from without.
   Under the name of common or general sensibility may be included
a variety of internal sensations, ministering for the most part to the
organic functions  and to the  conservation  of the body.   Most parts
of the frame have their  several feelings of comfort and pleasure, of
discomfort and pain.  In many of the more deeply seated organs  no
strong sensation  is ever excited, except in the form  of pain, as a
warning of an  unnatural condition.  The internal sensations of warmth
and  chillness,  of  hunger,  thirst, and their opposites, of  nausea, of
repletion of the alimentary and genito-urinary organs, and  of the relief
succeeding their  evacuation, of the privation  of  air, &c, with the
bodily feelings attending strongly excited passions and emotions, may
be mentioned among the principal varieties of common sensation.
   The special  sensations are referable to five leading forms, and are
distinguished  not  less by their  several modes  or characters, than by
the more special and elaborate construction of the peripheral parts of
their  respective organs, whereby these are adapted  to  receive the
impressions of  their appropriate stimuli.  The  special sensations ex-
cited through  the instrumentality of the peripheral organs of  touch,
taste, smell, vision, and  hearing, are primarily designed to inform the
mind of the conditions  of the external world ;  and it is for the most
part only in a  secondary manner, or through the mind, that they ope-
rate  on the organic functions, or for  the construction of the body.
   Almost all sensation is attended with the idea of locality, the mind
referring the cause of the change it experiences to the peripheral part
of the sensitive apparatus excited.   Thus the  ideas of distance, ex-
tent, and  relative  position  originate  in the very construction of our
bodies, and soon become applied to the material objects around us by
the comparison of the impressions on our different organs, and their
several parts,  with one  another.   The abstract idea of space  is a
further conception of the mind.
                           OF TOUCH.

  This is the simplest and most rudimentary of all the special senses,
and maybe considered as an exalted form of common sensation, from
which  it rises, by  imperceptible  gradations, to  its state  of highest
development in some particular parts.   It has its seat in the whole of
the skin, and in certain mucous  membranes, as that  of  the  mouth. 
OF TOUCH.—THE SKIN.
353
and is therefore the sense most  generally diffused over the body.  It
is also  that which  exists most  extensively in the animal  kingdom ;
being,  probably, never absent in any  species.  It is, besides, the
earliest called into operation, and the least  complicated  in  its im-
pressions and mechanism.  On these accounts  it  will  be the  first
treated of.
  The nerves of touch are the same, or at least are  derived from the
same part of the cerebro-spinal centre as those of common sensation.
They are the posterior roots of  the spinal nerves, and some fibres of
the eighth and fifth encephalic nerves.  The peripheral organ of touch
to which they are distributed is a tissue everywhere  diffused over the
sentient surface, but which in most situations is elevated into  papillae
more or less  distinct from one  another, and  closely  set, according to
the  tactile power.   The  nerves  of touch  are  remarkable  for the
ganglia which are  formed upon them on their emergence from the
vertebral canal, and for the  subsequent admixture with most of them
of nerves of motion.   In  these respects they differ from those of the
other special senses, except taste, which ranks next to touch in the
ascending scale.
   In accordance with our general plan, we shall commence with an
anatomical  description  of the  skin, which  is the  principal  seat of
touch ; and it will be convenient to include with it an account of the
various glands and appendages found in  connection with this organ,
whether they have any relation to the sense in question or not.   We
must premise, however, that this external integument is a part only
of a great physiological system, which comprehends also  the  mucous
membranes, and the true  or secreting  glands;  all of which, taken
together, and reduced to their most simple expression, are a continuous
membrane,  more  or less involuted,  more  or  less modified in the
elementary tissue which compose  it or are in  connection with it, and
within which all the rest of the animal is contained.  This expanse
consists of two elements ;  a  basement tissue composed of simple mem-
brane, uninterrupted, homogeneous, and transparent,  covered by an
epithelium, or  pavement, of nucleated  particles.  Underneath the
basement membrane vessels, nerves, and areolar tissue  are  placed
(p. 62).
   The sense  of touch exists only in those regions of this great sys-
tem which are exposed to the  contact of foreign bodies,  and where
it is essential to the comfort or preservation of the animal that the
presence  and  qualities of  external  objects should  be  perceived.
These regions, however, demand  a greater  protection, for the  same
reason ; and hence  it happens that the development of this  sense
is found to  be generally accompanied with the  most remarkable in-
crease and transformation  of the epithelial element, and of the areolar
tissue  lying under the basement membrane.  In the  skin the  thick
and hard epithelium is termed cuticle or epidermis, and the dense and
altered areolar tissue constitutes by far the largest proportion of the
cutis derma,  or cutis vera.
   The  external surface of  the skin, formed by the cuticle, (which
everywhere adapts itself to the  form of the surface on which it rests,) 
354
INNERVATION.
is  marked by furrows  of various kinds.   Some of these (furrows of
motion) occupy the neighbourhood of joints, especially on the side of
flexion, and  are generally transverse, facilitating  the  formation and
determining the position of the folds that result from the movements of
one segment of a limb  or another.  Others correspond to the insertion
of cutaneous muscles;  for  example, many of  those which  give force
and character to  the features; and these are  much modified by the
quantity of subjacent fat.   The elevator muscle of the lower lip thus
causes the " double chin."  Furrows of another kind are  seen in
aged  and emaciated persons, and after the subsidence of any great
distension of the integument, such as that occasioned  by anasarca or
pregnancy.   But, besides these coarser lines, almost every part of
the skin is grooved by  numberless very minute furrows, which, in the
more  highly developed regions, run in nearly parallel curved lines,
and elsewhere assume  a stellated arrangement, or  from a close inter-
lacement of no regular figure.  Those lines  are  important, as they
depend upon peculiarities in the texture of the  skin, having particular
relation to the sense of  touch: they may be best studied on the palmar
aspect of the hand and fingers, and on the sole  of the foot.  The
outer  surface of the skin  likewise  presents  innumerable  pores, the
orifices of the  sebaceous follicles  and sudoriferous ducts;  and the
various modifications of the  epidermis, termed " appendages of the
skin," as hairs, nails, &c, all project on the same aspect.
   The deep  surface of  the skin is formed by the  cutis, or cutis vera,
and is attached to  the  parts which it invests by an extension of the
areolar tissue, of which it is  itself principally composed,  as well as
by vessels,  nerves, and sometimes muscular  fibres, passing into its
substance from the subjacent  region.  It is on this surface  that the
sweat-glands rest;  they are imbedded in it more or less deeply, ac-
cording to  their  size, and the length of their excreting ducts; and
together with the fatty pellets, so abundant in  most parts of  the sub-
cutaneous fascia, occasion that areolar or cribriform appearance which
is  seen on this  aspect  of a  cleanly dissected  portion  of integument.
In preparing such  a specimen, it is at  once made evident, however
great  the difference  may seem to be between the dense and closely
woven texture of the cutis and the  lax  fascia  to which it owes its
mobility  on  subjacent  organs, that these tissues blend insensibly to
gether, and  are not separated from  one another by any abrupt limit.
Their ultimate  texture is, indeed, essentially  the  same.   Hence the
boundary we assign to the skin in this direction is in  some  measure
artificial.  Its precise  nature will be seen by considering the
   Intimate  structure of the  Cutis.—The white  and  yellow fibrous
elements of the areolar tissue are both much   modified, to constitute
the framework of this layer;  and  in  different parts  of the  skin, as
might be expected, they exist in different proportions, and  in  some
variety of arrangement.   These varieties are  not yet made out in
all their particulars ; but  we believe we  may state in general, that,
where great  extensibility, with elasticity, is required, the elastic ele-
ment  predominates (as in  the  skin  of the  axilla); and that where,
on the contrary, resistance  is demanded, the cutis  is chiefly composed 
THE CUTIS.
355
Fig. 77.
of a dense interweaving of the inelastic white element (as in  the sole
of the foot).  But in all situations the meshes are very close, and the
quantity of the mixed fibrous tissues  very great, as compared  with
almost any other  part of the  body (pp. 86—8).
   The fibres of the yellow element take a generally horizontal course,
and lie in multiplied  series over one another, branching at very fre-
quent intervals, to join those above, below, and on either side.  The
resulting meshes  are open on all sides, but are most flattened in a
direction parallel with the general surface.  They are more or  less
lozenge-shaped, and vary in  size not only with the region of the skin
in which they are examined, but according to their immediate relation
with  the  sudorific ducts,  and of other cutaneous appendages which
traverse them.   This  element of the cutis can  be  easily studied on
thin vertical slices, moistened with  acetic acid, which acts on other
parts, leaving it entire, and,  as it were, isolated.  (Fig. 77.)
   The thick and abundant fibres of
the white element  twine in  great pro-
fusion among  the interstices just
described,  but what  their precise
attachments are it is  difficult to de-
termine.  They  accompany  all  the
larger vessels and nerves,  and invest
the several small  glands with a loose
capsule.
   The gelatine, which may  be  ob-
tained in considerable quantity from
the skin, is derived from  this latter
part of the  cutis, and  it is probably
this element also which is principally
concerned in the  changes the skin
undergoes during the process of tanning.   The varieties in the quali-
ties of different  skins for this  purpose  might  be  explained  by  a
reference to those two varying elements of their fibrous framework.
In the museum of King's College is a specimen of excellent leather
tanned from the  skin  of Bishop, one of the murderers of the Italian
boy, who  fell a victim to the infamous system of "Burking" many
years since.
   Some anatomists have thought that the contractility of the  skin,
 manifested under the  influence of cold, and even under certain emo-
tions, is due to the existence  of peculiar  fibres; and Gerber  has very
recently figured what  he  considers to be  such fibres.  He  describes
them as begirting the hair-bulbs.
   There is a good reason for believing that these fibres, if they exist,
do not essentially differ from those of unstriped muscle ;  for in  the
dartos we  have  found the latter intermingled with an abundant and
lax areolar tissue ; and the close resemblance between  the  contrac-
tion of the scrotal membrane and that of the skin has been generally
recognized.  In  fact, the dartos seems  to be  nothing more than a
modification of the dermoid and subdermoid  tissue, of which  the
principal peculiarities are the excess of this form of muscle, the laxity
 Yellow fibrous element of the cutis of the
axilla.—Magnified 320 diameters. 
356                      INNERVATION.
of the meshes, and the absence  of fat.   It is probable, also, that the
phenomenon of "erection" of the nipple is due to the contraction of
similar fibres.  (Cyclop, of Anat. and Phys., vol.  iii. p. 518.)
  The thickness and strength of the cutis, or areolar framework of
the skin,  differ greatly in different parts according to the amount of
resistance required against internal or external pressure.   On  the
hinder surface of the body  it is denser than in front, and on  the outer
than on the  inner surfaces  of the limbs.   It is usually thin  over the
flexures of the joints.  It is particularly delicate on the  eyelids, and
proportionately so  in  some other situations, where  great mobility is
demanded.   In regions which are most subject to external  pressure,
as the soles  of the feet, it is firmly united by very dense laminae, to
the  subcutaneous fascia ; and the intervals between these are provided
with pellets of fat, forming a cushion, as an additional means of pro-
tection to the delicate organs it encloses and  covers.
  Among the lower animals we may notice  numberless examples of
an analogous kind.   One  of the most striking  is  that of the great
whales, which, being liable to enormous pressure on the surface  of
their bodies, from the medium in which they live, are provided with
a cutis of extraordinary toughness  and density, as  well as  with a
growth of subcutaneous fat, called blubber, of prodigious thickness.
  Fat occurs very generally in  the subcutaneous areolar tissue, serving
as a soft  bed on which the skin  may rest, and giving roundness and
symmetry to the outline of the body.
  It is on the exterior  surface of the cutis  that the tactile papillae
are  developed; and it is here  to be  remarked that there is no neces-
sary relation between the  degree  of their development, and of that
either of the dermoid  framework which supports, or the cuticle which
covers them.   It is true that in  the palm and sole all these  attain a
large  size, but, in  the back, the tactile  organ  is well-nigh  absent,
though the  cutis is dense; and in the tongue, on the contrary, this
organ  is  highly developed, while the  areolar framework is nothing
more  than a  very thin expansion ;  and the investment of cuticle is so
thin that the papillae form separate projections from the surface.  On
the  buccal surface of the lips and cheeks, too, the cuticle is  compara-
tively thin.
  In  all parts of the  cutaneous surface, as well as  in some portions
of the internal mucous tracts, common sensation exists, attended with
a feeble discriminating power, which must be regarded as the lowest
condition of the sense of  touch;  but  the organ peculiarly fitted for
receiving tactile  impressions  is concentrated  in  a  very remarkable
manner in certain portions  of the integument, which in other respects,
whether  from the precise  and  varied  movements they can perform,
or from their peculiar position, are the best  adapted to be  inlets of
this kind of  sensation.   The palmar surface of the hand and fingers,
or the sole of the foot, may be selected for description, as presenting
the most highly developed form of the organ of touch.
  The integument in these regions is finely and regularly furrowed
by  grooves, separated  from  one  another by corresponding ridges. 
TACTILE PAPILLA.
357
The direction  of these grooves and  ridges is various; they run  in
sweeping curves,  frequently branch to adapt themselves to the ine-
qualities of the general surface, and differ
somewhat  in  width  and  distinctness.
These lines indicate the arrangement and
development of the tactile organ below.
Each  ridge  is  produced by a single  or
double row of elongated conical processes,
termed papillae, projecting from  the sur-
face of the cutis into the epidermis.  The
grooves are occasioned by the  epidermis
sinking in to occupy the intervals  between
the rows of papillae.  The papillae in each
row are  usually  arranged in  pairs,  the
intervals between which  are indicated on
the outer surface by corresponding minute
and very  shallow grooves, crossing  the
tops of the ridges more  or less  at right
angles.   Each pair of papillae thus occu-
pies a little division of the ridge.  In the
centre  of  each cross  line, between  the
pairs of papillae,  is observed the  orifice
of a  sweat-duct (shortly to be  noticed),
which often is so large as to destroy the
linear character of the cross groove.   In a  square inch of the palm

                                Fig. 79.
 Surface of the skin of the palm,
showing the Tidges, furrows, cross
grooves, and orifices of the sweat-
ducts.  The scaly texture of the cuti-
cle is indicated by the irregular lines
on the surface.—Magnified 20 diam.
' Under surface of the cuticle, detached by maceration from the palm ; showing the double row* of
depressions in which the papillae have been lodged, with the hard epithelium lining the sudoriferous
ducts in their course through the cutis  Some of these are contorted at the end, where ihey have
entered the sweat-gland.—Magnified 30 diameters. 
358
INNERVATION.
 we  may generally count rather more than forty rows of papillae, and
 in each row rather more than sixty pairs of them.
   In the natural state the papillae are intimately united at all points of
 their surface to the epidermis which invests them.   By a slight mace-
 ration this union  may be so loosened that the two  structures  may be
 readily separated from one another.  In gradually tearing off the epi-
 dermis, the foregoing account of the arrangement of the papillae may
 be fully verified with the aid of a pocket lens.   They are seen  to
 form a close pile on  the surface of the chorion, each one being lodged
 in a separate cavity  in the deep surface of the cuticle.   The  papilla?
 are not equal in size, but frequently a small one is joined with a large
 one : and the clefts left between them, by the removal of the epidermis,
 are  unequal  likewise;  those between the rows being deepest, and
 those  between the individuals of  a pair being  commonly shallower
 than those between the pairs.  This  subordination corresponds (though
 not accurately in degree) with that of the grooves on the outer  surface
 of the  cuticle, where the shallow intervals between the individuals
                                      of a pair are not even visible
                FiS- 80-                 at all,  being  lost by the  thick-
  r^-r->'■'"..'":;'■?'?. '-"£; ^7iTT7-:'^:V'-:f"::n     riess of the superimposed sub-
  ■ :-:-'""-».^a, i*-:'"'   «; ■          'v,   stance.  Such is the exactness
  W-.'::'**r-& ^  • *       .    -„-> -     °f ^ne  impression or  mould of
     0    '  **W           ~'  '■  ■*     the  papillary structure  which
       V£. „     ».'"""'  *'*•*,}     tne  under surface of the  epi-
  '-■   '■'":,--!'< (^   .'   ^      .'-■/ -'     dermis  presents, that  it  fur-
  ?      W' ^   '  "•  "f%  ^  ''  ' '     nishes  an  excellent test  of the
  ?-^v  '• jsa • ^   )'/■;,  *.,  ■l'r'f-"'":     amount and   complication of
  :%%/.,         'XS*   .   -\-       the  former   structure  in  dif-
    &                          .      ierent  regions  ot the  skin.
        -,.,,-   '   ®.        r        lhis will be seen by compar-
   ":; : •"- :  '■"""'    '  ' *"               ing  figs. 79 and 80; the latter
  Under-surface of the  cuticle, from  the leg:-a.  0f  which, taken from  the CU-
hmall creases or furrows. 6. Shallow depressions for  . .    _  '                 ,
the papillary structure, c. Epithelium of sudoriferous  tide of the leg, represents the
ducts, corresponding to those in  fig. 79.—Magn.  30  in    j       •    •  .    u#„U
diam.                                  shallow depressions into which
                                      the few dwarf papillary eleva-
tions of  the cutis in  that part have been  received.   The gradations
of size in the papillary structure can be everywhere  admirably traced
in this way ;  and will be  found to correspond  accurately with the ac-
count  of the  relative acuteness of the sense of touch  in  different
parts, deduced from  experiments, which will  be  subsequently given.
  The papillae are of an  average length, in man, of T^-o of an  inch ;
at their  base, where  they spring from the  cutis, they measure  about
2io of an inch in diameter, and they taper off to a slightly rounded
point.   They are  semi-transparent and flexible ;  but sufficiently firm
in texture to  resist maceration  long, and not readily to admit of being
detached from the cutis.   Viewed, when fresh,  with a high microscopic
power, their outline is definite and sharp, and  there  is good reason to
suppose  it formed  of an unbroken expansion of the  homogeneous -
basement membrane  already spoken of.  Within this it is difficult to
distinguish any special  tissue, except by artificial modes of prepara- 
TACTILE PAPILLAE.
359
tion.
Fijj. 81.
 Papillae of the palm, the cuticle
being detached. —Magnified 35
diameters.
Fie. 82.
       A  fibrous structure, however, is  ap-
parent, having a  more  or less  vertical  ar-
rangement: and with the help of solution of
potass, filaments of extreme  delicacy, which
seem to be of the elastic kind, are generally
discoverable in it.  Injection of the blood-
vessels demonstrates the existence of a small
arterial twig derived from the arterial plexus
of the cutis, entering at the base, advancing
up  the interior of  the  papilla,  and  subdi-
viding into two or more capillary vessels, according to the size of the
particular organ.  These, after forming small loops, reunite either at
the base of the papilla, or in  the subjacent texture, into small veins,
which empty their blood  into the venous plexus  of the  cutis.  The
capillaries of the smaller papillae  frequently join with those of the fat-
vesicles that lie beneath.   The vascularity of the papillae is such, that
their  presence and  relative  size may be
determined simply  by  the  depth  of the
colour imparted to a portion of skin by a
good injection of  its vessels.   The  vascu-
larity  of  the  integument is  therefore, in
general terms, proportioned to its perfection
as an organ of touch.
  Since  the  discovery  of the papillae  as
the sentient organs,  the existence of nerves
within them  has  been  usually  taken for
granted,  or they have been  loosely styled
expansions of the  nerves; and to the gene-
ral  truth of such statements we may readily
assent.  But we have reason to  doubt the
accuracy of some  recent writers, who have professed  to give  minute
details of  the  mode of termination  of the nervous  tubules  in the
papillae.   The subject is difficult  of investigation.   According  to
Ernst Burdach (Beitrag  zur Mikroskop. Anat. der JYerven: Konigsb.
1837), and others, the  nerves are arranged in  a plexiforra  manner
under the skin of the frog, and> loops are formed by the  union  of
tubules from  neighbouring branches.  On  examination we  find this
description correct as far as it goes, but that it does not carry us to the
papillary structure.  The plexus in question is situated  underneath
an  expansion  of fibres crossing  each other at right angles, which is
itself placed beneath the  true skin, and separable  from it;  and we
have observed single tubules from the plexus penetrating this  expan-
sion in their course to the skin.   They have then been lost to view.
We have hardly been  more fortunate in discovering the true termina-
tion of the nerves  in the nictitating membrane of the eye in the same
animal, or in the papillary tissue so largely developed on the  thumb
at a certain season.
   In our  attempts to follow  the nerves  for  any distance under the
papillary structure in the higher animals,  the fibrous tissue (and espe-
cially the elastic variety), forming the cutis, has been found so much
 Vesselsof papillae, from the heel :
—a. Terminal arterial twig. v. Com-
mencing vein.—Magnified 80 dia-
meters. 
360
INNERVATION.
Fig. 83.
 to impede the view, that no  satisfactory conclusion has been arrived
 at.   In regard to their  presence  in  the papillae themselves, we  can
 affirm that we have distinctly tracetKsolitary tubules ascending among
 the other tissues of the papillae about half-way to their summits, but
                          then becoming lost to sight, either by simply
                          ending, or else by losing the white substance
                          of Schwann, which alone enables us to dis-
                          tinguish them in such  situations from other
                          textures.  Thin vertical sections of perfectly
                          fresh specimens are essential fortius investi-
                          gation, and the  observer should try upon
                          them the several effects  of  acetic acid and
                          solution of potass.   In thus describing the
                          nerves of the papillae from our own observa-
                          tions,  we do not deny the existence of true
                          loop-like terminations as figured by so  re-
                          spectable an authority as Gerber,  (General
                          Anatomy, translated by Gulliver,)  but  nei-
                          ther do we feel entitled  to assent to it.  We
                          have in numerous instances failed to detect
                          any nerves  at all within the papillae, when
                          such were plainly visible at their base, and
                          when,  consequently,  the  chemical agent
                          employed  could  scarcely  have destroyed
                          their characteristic structure, had they been
                          present.   We incline  to  the belief that the
                          tubules either entirely or in a great measure
                          lose  the white substance when within the
                          papillae.   We  would, however, refer the
                          reader to what will  be found respecting the
                          nerves of the papillae  of the tongue in the
                          chapter on taste.
                            The  essential  tissue  of the papillae pro-
                          bably exists even where no projections large
                          enough to be called papillae are  present.
                          These portions of the skin are more scantily
                          supplied with  nerves ;  and it  is probable
                          from this circumstance, as well as from  ex-
                          periments afterwards to be detailed, that the
                          individual nervous  tubules are wider asun-
                          der,  and  occupy each  a more  extensive
                          surface than  in  parts  thickly set  with  pa-
                          pillae.
                            The cuticle, or epidermis, (fig.  83, a,) like
                          the  cutis, varies  greatly in  its  thickness.
As its chief use is that of affording protection, it attains most  density
on parts most  exposed to pressure and friction, as  the soles of the
feet and the palms of the  hands.  In the  same parts, too, it varies
with the amount of pressure to which it is subjected at different times;
whence the hard hands of the artizan, compared with those of persons
  Vertical section of the sole :—a.
Cuticle ;  the deep layers (rete mu-
cosum) more coloured than the up-
per, and  their particles  rounded;
tlie superficial layers more and
more scaly. 6. Papillary structure.
c. Cutis,  d. Sweat-gland, lying in
a cavity on the deep surface of the
skin, and imbedded in globules of
fat. Its duct is seen passing to the
surface —Alagnitied 40 diameterF. 
STRUCTURE OF THE CUTICLE.
361
 who have spent their time in gentler occupations.  This increase  in
 thickness probably results from the  mechanical stimulus  applied to
 the capillaries of the part.   But, in whatever  manner it may admit
 of explanation, there is scarcely a more striking instance of that  in-
 herent power which the  body possesses of adapting  itself to varied
 external circumstances, than  this one presented by the human cuticle.
   This investment  is not permeated by either vessels or nerves, but
 consists  solely  of a  congeries of  nucleated  particles,  arranged  in
 numerous superimposed laminae, and united together  by  an interven-
 ing substance in very small quantity.   Those particles that lie deep-
 est, and  rest  immediately on  the cutis, are  little  more than small
 granules, scattered  in  a homogeneous matrix, which serves to unite
 them together.  Those of the  next layers  are rounded cells, consist-
 ing of a  transparent membrane, in  which similar granules, but  some-
 what larger in size, are visible.  In the succeeding layers these cells
 are more and more compressed as
 they are nearer to the surface ; and
 on the surface they are so flatten-
 ed, that their opposite surfaces are
 in contact, and  adhere, forming
 mere scales, in which the nucleus
 remains.  The  diameter of  the
 deep particles is about 30V0- inch,
 and  of the superficial ones  eiw
 inch.
   We  know  that  the superficial
 scales  are being continually shed
 in  small lamelliform masses, and
 it  is  evident that  their  loss  is
 supplied from  below ; hence  new
 particles must be  constantly  pro-
 duced  in the  deepest layers, and
 must be in uninterrupted advance,
 through  a  series of  changes, till
 they are cast off from the surface.*
 These changes are not confined  to
 their figure ; the laminae they first
 form are moist, and comparative!)
 soft, and rest like a cushion on the
 highly  sensitive  surface to which
 they are adapted, and whose ves-
 sels supply the materials for  their
 development.  The more external
 ones  are hard, horny, and much
 drier.   Schwann has also pointed out that their chemical properties be-

  * The cuticle of reptiles and amphibia is periodically cast off in a more or less
entire stale, a new one being previously formed beneaih it.  In amphibia the epider-
mis is tesselated; the scales adhering to one another by their edges,  and being usually
pentagonal.  A similar ecdysis, or shedding, occurs in the larva state of insects, and
in the arachnidans.
        24
Fig. 84.
  a. Section of the skin of the heel, treated with
weak solution of potass :—a. Basement mem-
brane of papilla, ft. Layer of nucleated cells
resting on the basement membrane,  c. Several
succeeding layers, partially dissolved and theii
nuclei gone. d. Higher layers, not affected by
the menstruum,  e. Elastic fibrous tissue of the
papilla,  v. Its capillary vessel.
  b. A  similar specimen, treated with  strong
solution  of potass:—a. e, and v. as in a. The
layer b is wanting, having been displayed,  c.
Converted into a gelatinous mass with striae,  d.
Unaffected.
  The more external layers of the epidermic
scales are not represented in  these figures.—
Magn. 150 diam. 
362
INNERVATION.
came modified ; that at first they are soluble, but afterwards insoluble,
in acetic acid; and this circumstance of a chemical change occurring in
the  stages of their development seems to us so important that we shall
illustrate it by two views, fig. 84, a and c.  In the former the action
of weak solution  of  potass is  shown:  the layer of cells  immediately
resting on  the basement mernbrane, together with the more super-
ficial scales, is but slightly or not at all dissolved ; while several inter-
mediate layers are swollen and rendered very transparent, having lost
their nuclei.   The abruptness of the  change is remarkable, and con-
tinues after the whole specimen is saturated.   In the  latter figure  a
stronger solution  has been employed ; the deep layer is dissolved, but
the  superficial scales are still unaffected, while the intermediate part is
reduced to a semi-fluid mass, in  which scarcely any vestige of  struc-
ture remains.  It is very possible that  other  agents  might disclose
further varieties  of chemical constitution  in smaller  subdivi.sions of
the  cuticular lamellae.
  These facts will go  far to explain why it  happens  that  the  union
between the panicles  composing the same layer  is in general more
intimate than that between different layers,  so  that it is not difficult
to divide the cuticle into two, three, or more laminae  ; and, in parti-
cular, why it is easy, at a certain stage of maceration,  to separate the
harder from the softer layers, and thus to isolate the structure termed
" rete Malpighii."  This is  nothing  more than the deepest, or most
recently formed,  part of the  cuticle.   When isolated, it presents de-
pressions, or sometimes complete apertures, which have been occupied
by  the projecting papillae;  and hence the term rete.  When apertures
exist, the cuticle  on  the top of the papillae has been detached with the
outer hard  layer,  and that  in  contact with and encircling their bases
remains by itself.
  In the  coloured  races  of mankind,  there  is, at  first  sight, some
ground  for  supposing the rete Malpighii  to  be a  structure  distinct
from the other layers of the cuticle, the colouring matter being found
to reside chiefly  in this part.  However various in quantity and hue,
the colouring matter always  consists of oblong or  oval grains of ex-
treme  minuteness, (aorjorj of an  inch  in their  long diameter,) and
occupying the interior of some of the  epidermic particles.   In the
                         negro  it is accumulated in enormous quan-
         Fig. 8">.          tity, and  completely  envelops  the  nuclei
                         immediately  resting on the  cutis.  On ex-
                         amining a  vertical section of  the  whole
                         cuticle, we  find the colouring  matter gra-
                         dually  diminishing as  we  approach  the
                         surface ; and it is most clear that there  is
  vertical section of the cuticle, n° true line  of demarkation  between the
feHiS^S^ u:° portions.  We may observe the  colour
b. cei!» at a higher level, pn'.-r  and  0f  i]]e rete mucosum deeper at points; and
more rnnened. c. Cells at the sur-                  .       '      ' -   .    •
face, scaly and colourless as in the  a  greater proportionate  depth of colour  is
white races.—Maguiicil :J00 diame-  .  '    11          1    • .    .v.   _i   „u iUa
t:.rs.                      traceable over such points, through  all tne
                          layers, as far as the surface: we may even
discern a  sort of stream of coloured grains advancing towards the
surface.   Hence there can be little doubt that the decrease of colour
 
NAILS  AND HAIRS.                    363
in the superficial laminae  is due to that  chemical change which has
just been described as gradually taking  place in the interior of the
epidermic particles.  As it is not always easy in this country to obtain
specimens of the negro's skin, the above facts may be verified in the
skin of  coloured domestic animals, or, less satisfactorily, in that of
some portions of the skin of the white race, as  that of the  scrotum,
of the nipple during pregnancy; or of accidental moles, or freckles.*
The bronzing of parts exposed to  the sun is  effected  by a  similar
deposit of colouring matter in the  deeper laminae of the cuticle.
   The  subject  here referred  to has been  invested with  additional
interest by its  supposed  bearing on the warmly debated question of
the specific difference of  the negro  from the white  man.  We  need
not inquire how far the existence of a distinct cuticular lamina might
avail the advocates of such  a difference, for we may freely  state our
conviction that no  such peculiar layer exists.   The sole variety is in
the  presence of pigment—which  may occur, partially, under many
circumstances in the white  races,  and may be  wanting in  the   true
negro.   (See Dr. Prichard, Natural History of Man.)   The reader of
the preceding paragraphs will understand how little such processes as
maceration,  and even the most delicate dissection by the naked  eye,
and with ordinary  instruments, are to be depended on  for the deter-
mination simply of the anatomical  fact.
   The nails and hairs are peculiar modifications  of the epidermis, and
consist essentially  of nucleated particles.
   The  nails  are flattened, elastic,  horny,
protective coverings, placed  on the dorsal
surface  of the terminal phalanges  of the
hands and feet, and projecting beyond the
flesh.    Hoofs, claws, &c,  are  varieties
of them.  The nail has   a  root,  or part
concealed within  a fold  of the  cutis;  a
body, or exposed part attached to the sur-
face of the cutis ; and a free or projecting
edge.   The cutis underneath the root and
body is  termed the matrix, from its being
the producing Organ of the nail.  This is   Section of the  stein on the  end of
,, . ,     ii-ii       l       1 *t     1     the finger:—The cuticle and nail n,
thick and highly vaSCUlar, and its  COlOUr  detached from the cut.s and matrix, m.
is  seen  through the transparent  tissue.
Near the root it is white,  and occasions the appearance termed lunula.
The nail has a firm adhesion to (he  matrix, and is  moulded upon it,
like the epidermis  in other situations.  The true epidermis (as   dis-
tinguished from the nail), is continuous  with the nail  at the whole
circumference of its body ; the root dips  into the fold of cutis, within
the epiderm's, and  the free edge projects  beyond  it.  In  the advanced
foetus we find the edge of the  nail  to be  directly continuous with the
epidermis of the  end of the  finger, and only to become free  by a
rupture  of  this connection  after birth.   Thus  the nail covers  that
portion  of cutis which is without  cuticle.  It   has  been frequently
discussed whether  the cuticle is continued over and under the nail;
   • Dr. Simon of Berlin has  ably investigated  this part  of the subject.—Miiller's
Archiv. 1840.
 
364
INNERVATION.
but this is a question  of words only, the nail being the same essential
structure  as the cuticle.  The border of the root of the nail  is jagged,
thin,  and  soft, and consists of  newly formed  substances ;  the deep
surface of the body is also soft, and marked by longitudinal grooves,
corresponding to the  papillary ridges on  the surface of the matrix.
These soft under-parts consist  of nucleated particles, similar to those
of the deep layers of the epidermis.  The more superficial  laminae of
the nail are more and more dense and fibrous; but when treated with
acetic acid, some imperfect  traces  of nuclei may still be detected in
them.  The nail grows both at  the root  and on  the deep  surface of
the body  ; as the substance  furnished by  the  root advances towards
the free edge, it receives accessions from the surface of the matrix.
   Hairs are found on all parts of the surface, except the palms of the
hands and the soles of the feet, and differ much in length, thickness,
shape, and colour, according  to situation, age, sex, family, or race.
We may  select one of average size  for a description  of their structure
                           and mode of growth.   The  shaft  of  the
                           hair is that part which  is fully formed, and
                           which projects beyond  the surface.  Trac-
                           ing  this into the  skin, we  find it  lodged in
                           a follicular involution of the basement mem-
                           brane (fig.  87,  a),  which  usually  passes
                           through  the  cutis into the  subcutaneous
                           areolar tissue.   This hair-follicle is bulbous
                           at its  deepest part, like the hair which it
                           contains. Its sides have a cuticular lining,
                           b, continuous with the epidermis, and  re-
                           sembling the  cuticle in the rounded form
                           of its deep cells,  and the  scaly character
                           of the  more  superficial ones, which  are
                           here in contact with  the outside of the hair,
                           c.  The hair grows from the bottom of the
                           follicle,  and the  cells of the deepest stra-
                           tum  there resting on  the basement mem-
                           brane are very similar to those which in
                           other parts  are transformed into scales of
                           cuticle.    A gradual  enlargement occurs in
                           these cells as they mount in  the soft bulb
                           of the hair, which, indeed, owes its size to
                           this  circumstance.   If the hair  is  to  be
                           coloured, the pigment  grains are  also here
                           developed—for  the  most  part  in  scattered
                           cells, which  may  send out radiating pro-
                           cesses—at other times, in a diffused man-
                           ner around the nuclei of the cells generally.
                           It frequently happens that the cells in  the
                           axis of  the bulk become  loaded with pig-
                           ment at  one period,  and not at another; so
                           that, as  they pass  upwards in the shaft, a
                           dark central tract is  produced of greater or
 Bulb of a small black hair, from
the scrotum, seen in  section,  a.
Basement membrane of the follicle.
b. Layer of epidermic cells resting
upon  it, and becoming more scaly
as they approach c, a layer of im-
bricated  cells, forming  the  outer
lamina, or cortex, of the hair. These
imbricated cells are seen more flat-
tened and compressed, the higher
they are traced on the bulb. Within
the cortex is the proper substance
of the hair, consisting at the base,
where it rests on  the basement
membrane, of small angular cells
scarcely larger than their nuclei.
At d, these cells are more bulky,
and the bulb consequently thicker;
there is also pigment developed in
many of them more or less abund-
antly. Above d. they assume a de-
cidedly fibrous character, and be-
come condensed  e A mass of cells
in the axis of the hair, much loaded
with pigment. 
STRUCTURE OF HAIR.
365

ii
less length, often  only in irregular patches, and the hair  appears here
and there to be tubular, e.   The shaft is much narrower than the bulb,
and is produced by the rather abrupt condensation and  elongation into
hard  fibres of the  cells, both  of  those which  contain  pigment and
those which do not.  These  fibres may be  demonstrated  by simply
crushing small  fragments of hair,  but they become more conspicuous
when the tissue is softened by a strong acid.  The granules of pigment
assume  a linear arrangement between the fibres, which  are  firmly
united into a solid  rod by a  material similar, it may be  supposed, to
that which cements the  scales of the cuticle.
   The central series of cells just mentioned, when filled with pigment,
seems less disposed to become fibrous than  those  around ; and some
authors  have described it as a medulla,
in  distinction  from the fibrous part of
the shaft,  which they then term cortex.
But  the  tubular character,  however
constant in  the hair of  many  animals,
is very variable in human hair, both in
different  situations, and in the  same
hair  at  different points of its  length,
 as may  be seen very well by means of
transverse sections (fig. 88, a, b).*
    The human  hair has  a proper bark,
or cortex,  formed in the following way.
A  single layer  of the cells immediately
surrounding those about to  form the
fibrous tissue of the shaft are  seen near
the bottom of the follicle to assume an
 imbricated  arrangement (fig.  87. c),
 and gradually to mount on  the hair,
 becoming more compressed  against it
 in their ascent,  until they form upon
 its surface a thin  transparent colour-
 less film,  in which the  overlapping of
 the delicate  cells is still exhibited by
 elegant and exceedingly fine  sinuous
 cross lines (fig. 88, d, dl).   The fibrous
 interior and this  peculiar cortex to-
 gether compose  the shaft  of the hair.
 By the continual  emergence  of  fresh
 portions of  the shaft from  the follicle,
 fragments of the cuticular  lining  of the latter are apt  to be drawn up

   * Transverse sections of extreme thinness may be made by fixing a lock of hair
 between two pieces  of c#rd or wood in a vice, and then shaving  it with a razor.   In
 many animals, as the  horse  and dog. the hairs are tubular.  In others they present a
 central series of cells, round or  compressed, with  or without pigment, as in the cat
 and mouse. In others, again, their external surface is regularly  marked by annular,
 and sometimes toothed projections,as in the Indian bat: and numerous other varieties
 mieht be enumerated.  The quills of the porcupine, and the feathers of birds, are
 modifications of the epidermic tissue, and, in their essential characters, are closely
 allied to  hairs.  See Busk, in Microsc. Journal.

 a. Transverse section of a hair of the
head,  showing the  exterior cortex, the
fibrous tissue with its scattered pigment,
and a central space filled with pigment.
b. A similar section of a hair, at a point
where no aggregation of pigment in the
axis exists, c. Longitudinal section, with-
out a central cavity, showing the imbrica-
tion of the cortex, and the arrangement of
the pigment in the fibrous part.  d. Sur-
face, showing the sinuous transverse lines
formed by the edges of the cortical scales.
d'. A portion of the margin, showing their
imbrication. Magn. 150 diam. 
366
INNERVATION.
upon the hair, aided, probably, in this, by the imbrication of its sur-
face, and are often found clinging around it for some way; but they
are not to be regarded as any part of the hair itself.
   In the larger hairs  there is usually a double series of these imbri-
cated cortical scales;  the outer having its teeth interlocked with  those
of the  inner,  but apparently but loosely adherent to  them.  This
outer series seems to be intermediate between the true  cortex and the
cuticle  of the follicle, and to belong rather to the latter,  since it does
not appear upon the extended portion of the hair.   The  cortex  is
much denser than even the fibrous part of the hair, and  is less  acted
upon by strong solution of potass.
   From the preceding description it will  be  evident that the fibrous
part  of the hair is a peculiar development  of the  cuticular  cells
resting on  the bottom of the follicle, that the imbricated  cortex  is
formed by  a single series differently developed at the  circumference
of these, and that beyond this series comes the cuticular lining of the
follicle ; so that the hair is neither covered nor underlaid by cuticle,
but it is in  fact the modified cuticle of the bottom of the follicle.  A
thin layer of papillary tissue  probably coats the bottom of the follicle
in most cases; and where the hairs are  large, and especially where
they serve  principally as tactile organs, there may be  a  projection of
a true papilla, furnished with nerves and capillaries, into the bulb of
the hair, as is very conspicuous in the whiskers of some animals and
in the quills of the porcupine   An approach to  this papillary pro-
jection may be frequently seen in  the hairs of man; but its  real size
appears to  have been much overrated, from the basement  membrane
having been overlooked.  Where a papilla exists, the basement mem-
brane is of course  continued over it, and separates it from the true
hair, which is never penetrated by either vessels or nerves.
   The  sebaceous glands of the skin  very generally open  into the hair
follicles at  a short distance from the  surface.
   The  hair follicle is fixed more or less firmly in its place, according
to the size  and stiffness of the hair,  by the dermoid and subdermoid
tissues uniting intimately with it on its deep or convex surface, where
also are spread  out the capillary vessels  which furnish the materials
of growth.  These latter are adapted in number to  the dimensions
of the follicle.
   Thus the hairs, like  the  cuticle, are  beautifully  organized, and
maintain a vital, though not  a  vascular, connection with the body.
Some evidence of their retaining a degree of vitality is  found in the
fact,  first pointed  out by Mandl, and  verified in  some  instances by
ourselves, that hairs have a tendency to become pointed after having
been cut short  off.   The process is  very slow, and seems to consist
in a further condensation and  elongation  of  the elementary cells at
the new extremity.
   Well-authenticated instances have occurred, in which the hair has
grown white in a single  night, from the sudden  influence  of  some
depressing  passion ; and some have held this circumstance a  proof
that fluids circulate through them.   It seems most probable that this
phenomenon results from the secretion, at the bulb, of some  fluid— 
LYMPHATICS OF THE SKIN.                 367
perhaps an acid, as Vauquelin supposes—which percolates the tissue
of the hair, and  chemically  destroys the  colouring matter.  The
ordinary gray hairs of age resemble other hairs in  every respect but
colour, and the process  of change from dark  to  gray seems to take
place rapidly in each individual hair.
  According to Vauquelin, the colour of hair  depends on  the pre-
sence of  a peculiar oil,  which is  of a sepia  tint in  dark  hair, blood-
red in red hair,  and yellowish  in  fair  hair.    When  extracted, as it
may be by alcohol or aether, the hair is left of a grayish yellow.  The
colour is  destroyed by chlorine, and  probably otherwise  resembles
closely that  of the cuticle in the dark races.   The substance of hairs
is similar in chemical  composition to that  of  horn.   After being
softened  by maceration in cold nitric  acid, it is soluble in  boiling
water, and the solution after evaporation becomes  a  gelatinous mass
on  cooling.  The horny  matter  is  said  to be  distinguishable from
coagulated albumen  or  fibrine  by its being readily soluble in caustic
fixed alkalies, but not in caustic ammonia.  The ashes of  hair amount,
according to Vauquelin, to one  and a half per  cent, of its weight;
and contain oxide of iron, a trace of oxide of manganese, of sulphate,
phosphate, and carbonate of lime, and of silica.  Black hair contains
most iron, and  light hair least.  (Baly's Muller,  p. 424-5, quoted
from Berzelius.)
   Hairs, when  dry and warm, are easily rendered  electrical.  They
readily attract moisture  from the  atmosphere,  and no  doubt from the
body also, yielding it again by evaporation,  if the air  be  dry.  When
moist, they elongate considerably ;  a property which Saussure took
advantage of in  the construction of his hygrometer, in  which a human
hair, by its elongation and shortening in moisture and dryness, is made
to turn a delicate index.
   The shape of the hairs in  different situations offers some variety.
In general they taper towards their free end.   Those  of the head are
often not  cylindrical, but  compressed  on  one or both sides, so that
their transverse  section is reniform or oval.   The eyebrows and eye-
lashes taper towards both  extremities.   Hairs  also vary in being lank
or woolly, permanent or deciduous.  The frizzled  hair  of the negro
is one of his most remarkable  characteristics, but has  all  the essential
structural characters of the hairs of the other races.
   The diseased  condition called  plica  Polonica is a matting together
of the hairs from the effusion of a glutinous matter  probably from the
cutaneous glands.   It is said that hairs so affected bleed, if cut close to
the skin.  This, if true, may result  from  a morbid  elongation of the
vascular  papillae at their roots.   In  the whiskers of large animals
these papillae are so  long that  they are cut and bleed if the whiskers
are shaved off".
   In some regions of the  skin  it  appears certain that  a lymphatic net-
work exists  immediately under  the surface  of the  cutis, probably
under its  basement membrane.   Mercury injected into  this  network
through  a puncture  in  the  cuticle passes readily into the neigbour-
ing  lymphatic trunks, and removal of  the cuticle does not  injure its
meshes.   These circumstances may be observed in  the penis, scro- 
368
INNERVATION.
rig. 89.
 Vertical section of the skin
and sweat-glands of the axilla;
—a. Layer of glands with their
ducts traversing b. the cutis and
cuticle, c. Small hair,  d, d.
Portions of  larger  hairs. —
Magn. one and a half diam.
 turn, and n:pple ;  but it is probable that the  network sometimes  ex-
 hibited by  his procedure in  other parts of  the  skin, is a  fallacious
 appearance due to the mercury having insinuated itself between the
 cutis and cuticle, in the furrows at the base  of the papillary structure ;
 for it does not find its way into the lymphatic trunks, and is deranged
 by a complete  separation of the cuticle.  (Cycl. of Anat. and Phys.;
 art. Lacteal and Lymphatic System.: by Mr.  Lane.)
   The sweat-glands exist  under almost  every part of the  cutaneous
 surface.  They lie  in  small  pits (fig. 83, d) on  the  deep aspect of
 the cutis ; or, if large, entirely  in the subcutaneous fascia.   As before
 mentioned, their orifices  are  discernible in  the  middle of the  cross
 grooves that intersect the ridges of papillae  on  the  hands and feet.
                        Here their arrangement is necessarily regular,
                        and their size  is about that of a pin's head.
                        But in  other parts they are irregularly  scat-
                        tered,  though in general in pretty equal num-
                        bers over areas of the same dimensions.   In
                        certain  situations,  however,  they   are  very
                        large ;  and, as  might be  expected, we  find
                        their size and number in  different districts of
                        the skin to  correspond with  the amount of
                        perspiration afforded  by  each.   Thus,  they
                        are nowhere so remarkable, or so  easily ex-
                        amined, as in  the  axilla, over a space  pre-
 cisely defined  by the growth  of the hair in  the  adult.   They here
 form a layer, which towards the middle, is often an eighth  of an inch
                                  thick, but thinner towards the edge.
                                  It is of a reddish colour,  and mam-
                                  millated by the individual glands
                                  which compose  it.   Some of these
                                  are as large as  the  labial glands,
                                  but  most  of them  are  somewhat
                                  smaller.   They  are  soft, and more
                                  or less flattened by lateral apposi-
                                  tion with one another.  They lie in
                                  an  atmosphere  of delicate  areolar
                                  tissue, and are  covered  and  per-
                                  meated with a network of capillary
                                  blood-vessels.
                                     The sweat-glands can be shown,
                                  wherever they  exist, by dissecting
                                  a piece of fresh integument on  its
                                  deep  surface.    They  are  distin-
                                  guishable  from  the pellets  of fat,
                                  with  which they have  doubtless
                                  been  repeatedly confounded,  by
                                  their pink  colour semi-transparent
                                  texture.  Where the areolar frame-
                                  work of the cutis is densely inter
woven, they are less readily discerned, but injection  of the  blood-
 Sweat-gland and the commencement of its
duct:—a. Venous radicles on the wall of the
cell in which the gland rests. This vein anas-
tomoses with others in the vicinity, b. Capilla-
ries of the gland separately represented, arising
from their arteries, which  also anastomose.
The blood-vessels are all situated on the outside
e>r deep surface of the tube, in contact with the
basement membrane.—Magn. 35 diam. 
THE SWEAT GLANDS.                    369
Fis.91.
vessels makes their detection easy.   On detaching one of these glands,
and highly magnifying it, it is seen to consist of a solitary tube intri-
cately ravelled, one end of which is closed, and usually buried within
the  gland;  the  other  emerges
from  the gland, and opens on the
skin.  Sometimes  this  tube is
branched, but its  diameter is
usually very uniform  from  end
to end.   When  very long, the
open end forming the duct is a
little wider  than  the  rest.   The
wall  is comparatively thick, so
that the calibre is not more than
a  third of the whole  diameter.
It consists, like the correspond-
ing part of most other glands, of
two layers :  an outer or basement
membrane, with which  the ves-
sels are in contact; and an  epi-
thelium, lining the interior.  The
basement membrane is extremely
thin, and is  continuous  with the
outer surface of the papilla?. The
epithelium is much thicker, and
is an involution of the epidermis
that  rests on  the  papillae  and
dips  in between  them.   Hence
the  tube, traced  outwards  from
the  gland,   loses the  basement
membrane at the surface of the
papillae;  and  the remainder of
its course is  pursued  upwards
through  the successive laminae
of cuticular  scales.
   The preparation exhibited in
fig.  91 shows the  continuity of
the  epithelium  lining  the  ex-
creting part  of the duct .with the
cuticle,  and  also  discloses  its
hardness and cuticular character,
quite  different from that of the
secreting epithelium  within the
gland, which  is  soft  and  easily-
decomposed. We have remarked
that  the duct, in traversing the layers of the cuticle,  is lined by epi-
dermic particles having a different arrangement  from those  of the
cuticle itself;  being flattened in the vertical instead of the horizontal
direction, and especially distinct in the deeper and softer stratum  of
the cuticle.   This special  cuticular tunic of the duct is best exhibited
by treatment of recent specimens with solution of potass.
 a Vertical section of the cuticle from the heel,
detached by maceration as in fig 79.  The epithe-
lium of the sweat-duct, continuous with the cuticle,
has been drawn out of the tube of basement mem-
brane, as far as the gland, where it begins to be
contorted. The cavity of the duct is seen dilating
as it enters the cuticle, and then stretching up to
the surface through the  epidermic lamintc. The
deep surface of the duct is continuous with the
surface of the cavities in which the papillae are
lodged —Magn. :j-5 diam.
 b Duct at its entrance into the cuticle.—More
highly magnified. 
370
INNERVATION.
  The duct, on leaving the gland, follows a meandering, and  often
rather spiral direction, through the areolae of the cutis, to the interval
between the papillae, where it becomes straight; and it again assumes
a spiral course in perforating the  cuticle (fig. 83).   In the  cutis its
curves are unequal, elongated, and  wide ; but, in the cuticle, they
are  commonly as close  and regular as  those of a common  screw, the
form of which may  be taken as a fair model of the duct in this part.
It is not easy to explain the mode  in which the spiral form  is given
to the cuticular  part of the duct.  It has been imagined to result
from the condensation  and flattening of the laminae of epidermis as
they approach the surface ; but the fact, that the spirals are not closer
near the orifice, is opposed to this notion.   Their use, also, is obscure;
for  we cannot admit the validity of the ingenious idea that the orifice
of  a spiral tube  must be  valvular, and, therefore, that  they mecha-
nically resist the  entrance of foreign substances.  If they do offer
this opposition, it is only by the tortuosity resulting  from  the spiral
arrangement.   The  proper tunic of the duct in  the substance of the
cuticle  seems designed to  keep it pervious, and may be that which
gives it its peculiar  spiral form.   The  average  diameter of the cavity
of the duct is TTVo  inch; but, as  it enters the  cuticle, it  usually be-
comes wider.
  The last two  figures, as well as some  of the  preceding ones, illus-
trate the anatomy of the sweat-glands.
  The sebaceous  glands are found in most parts of the  skin, but are
                                                 absent  from  the
                                                 palms  and  soles.
                                                 They  are   most
                                                 abundant   on the
                                                 scalp and  face (es-
                                                 pecially about the
                                                 nose),  and  about
                                                 the anus and scro-
                                                 tum. The glandules,
                                                 odorifera   of the
                                                 genital organs are
                                                 a variety of them,
                                                 only   remarkable
                                                 by their secretion.
                                                 The  orifices  open
                                                 either on the gene-
                                                 ral surface, or into
                                                 the  hair-follicles,
                                                 and they lie either
                                                 in  the cutis or sub-
                                                 dermoid tissue, ac-
                                                 cording  to  their
size.   They are usually associated with  the hairs,  in the manner re-
presented in fig. 92.  They consist of a more or less  capacious  duct,
generally branched,  and terminating in blind, pouch-like extremities.
The basement  membrane of these glands  is thicker than that of the
 Sebaceous glands, showing their size and relation to the hair-folli-
cles :—a and b from the nose ; c from the beard.  In the latter the cutis
sends down an investment of the hair-follicle.—Magn. 16 diain 
ENTOZOA OF THE SEBACEOUS GLANDS.
371
Fig. 93.
sweat-glands, and is lined by an epithelium, in the particles of which
are included granules of sebaceous matter.  The terminal vesicles and
the ducts are filled with an  accumulation of this epithelium, which,
having been detached from the walls, constitutes the secretion.  On
the deep or parenchymal  surface of the basement membrane a web of
capillary vessels is spread out.
   While speaking of the  sebaceous glands, we must say a few words
of a parasite so generally found  in their ducts in  many parts  of the
body, that it may almost be regarded as a denizen.   This was recently
discovered  by Dr. Simon, of Berlin, (Muller''s Archiv., June, 1842,)
and  has  been  further described  by  Mr. Wilson, (Phil.  Transact.,
1844,) who speaks of two  principal varieties of the  adult animal,
chiefly distinguished by their length;  the one  measuring from T-^ to
5-V, the other from T^o to  T^5 of  an inch.  He details several interest-
ing particulars concerning their  structure and development, for which
                                        we  must refer  to the origi-
                                        nal memoir.  These singular
                                        animals " are  found  in  al-
                                        most  every individual, and
                                        especially in  those  possess-
                                        ing a torpid skin, and they
                                        multiply  in   sickness.  In
                                        living and  healthy persons
                                        from  one  to three or  four
                                        may be found  in  each folli-
                                        cle."  We have represented
                                        them as we have found them
                                        in a sebaceous follicle of the
                                        scalp  (fig. 93).
                                          The ceruminousglands of
                                        the  ear  resemble  in  their
                                        structure  those  just  de-
                                        scribed.  They exist in great
                                        abundance  in  the  skin of
                                        the cartilaginous part of the
external  meatus,  and  provide  an  adhesive  secretion  calculated to
entangle particles of dust  and small insects, and to prevent their access
to the delicate membrane of the  tympanum.*
   Of the functions of the Skin.—Having now considered the several
constituents of  that very  complicated organ, the  skin, it remains for
us to take a brief general view of its  functions before  proceeding to
a  particular  account of that  one which  brought us  to this structure,
viz., the sense  of touch.   All these functions have reference to its
external  anatoniical  position with respect to the other  structures of
the body.   Regarded as a protective covering, the skin possesses the
united advantages of toughness, resistance,  flexibility, and elasticity.
The areolar framework of the cutis is  the part chiefly conferring these

   * In the sharks and rays there is a remarkable system of mucous tubes  opening
on the skin.   These tubes are nearly as large as crow-quills,  and of great length*.
They end  by a blind extremity, to which a small nerve of the fifth pair is attached.
 Knt07oa from the sebaceous follicles :— a. Two seen in
their ordinary position in the orifice of one of the seba-
ceous follicles of the scalp,  b. Short variety, c. Long
variety. 
372
INNERVATION.
properties, which  are  due also in some measure  to the epidermis.
Both these structures are  developed in  a degree proportioned to the
force and frequency  of external contact to which different regions of
the body are liable.  They are thickest on the palms and soles, on the
back of the trunk, and the outer surface of the limbs:  thinner on the
front of the body,  and  on the inside of the limbs.
   These two elements also afford protection and support to the other
more delicate ones with which they are associated.   The areolae of
the cutis sustain the intricate networks of blood-vessels, lymphatics,
and nerves,  which  traverse it.   The sweat-glands are imbedded in
cavities  accurately fitted to receive  them; and their ducts, with the
sebaceous follicles,  and  hairs,  are  all lodged  in channels or spaces
adapted  to their respective sizes.   The epidermis  is a defensive in-
vestment to the tactile  organ, and, while it shields it from  the  inju-
rious effects of pressure, is the medium  through which impressions of
contact are  conveyed to it with  admirable  nicety and truth.  The
epidermis furnishes also special organs, such as nails and hairs; which
are developed in  particular situations, for the purposes of defence,
the preservation of  warmth, or as  aids to the  sense of touch.  The
infinite variety of  modifications which the epidermis presents among
the lower animals, joined with  others of nearly equal diversity in the
neighbouring textures, adapt it to very numerous and even opposite
uses in the animal kingdom.
   The skin combines the opposite functions of absorption and secre-
tion.   Its lymphatic network, and the capillaries, are both concerned
in the  former, which, under certain conditions, is  very actively per-
formed.
   Secretion may be  said to be carried on at every point of the surface
of  the  cutis, since  the cuticle is a deciduous  product, constantly in
course of separation from it.   But the  principal seat of this function
are those  glandular offsets from  the skin that lie scattered in num-
berless multitudes beneath it.   It may be safely said, that the secreting
membrane they comprise  far exceeds, in extent, the  surface of the
whole  body.   By the  involutions of the  sweat-glands, the surface is
multiplied, for the  sole  purpose  of secretion, and the  quantity of
material capable of being thus eliminated is enormous.  There is one
peculiarity connected with this great glandular surface, which results
from its not being  made up into a solid organ, but disseminated in
detached points under the integument, viz., that  it is more than all
others  subject to the influence of external temperature, acting  upon
the cutaneous blood-vessels; but an apparatus for adjusting  the irre-
gularities hence resulting is provided in the kidneys, as will be here-
after explained.
   The sebaceous glands are another great system, chiefly subservient
to the  protection  and  health  of the skin itself, but resembling the
sweat-glands in their disseminated arrangement.  They are extremely
numerous, and yield an oily material for the lubrication of the surface
of  the  cuticle.  On  most parts of the body they are  as abundant as
the hairs themselves.  They are an important accessory organ for the
elimination of hydro-carbonous matters from the system.  Thus the 
FUNCTIONS OF  THE SKIN.                  373
skin is a superficial emunctory of great  extent and  importance, and
will demand subsequent consideration in that character.
   We  may now consider the function of the skin as the organ of touch.
One of the distinguishing characteristics of this sense is its universal
diffusion over the exterior of the  body, by which  its sphere  of action
as a recipient of impressions, and  as  a criterion of locality, is rendered
more extensive than that of any other.   The contact of foreign bodies
is perceived as occurring at the point at which they actually strike the
organ of touch, whether that point be within the  sphere of operation
of any other sense or not.   The precision with which this is effected
depends very  much on  the  degree  of development of the  papillary
tissue in the several regions  of the body.
   We  have  already seen that  the papillae present  great  varieties in
different parts.  These  varieties will  be found  to  correspond  very
much  with  differences  in the mobility of such  parts.   In general,
touch is most acute in regions  best suited, by their structure, for easy
and diversified  contact with external substances;  for the power of
nicely  determining  the  position,  direction, and amount  of pressure
upon the organ of touch, is essential to  the perfection of the sense.
The will can not only excite and  check  the contractions of the mus-
cles, but is able to regulate their  force and  duration with wonderful
precision; for,  by  the muscular sense, as stated in  a previous chapter,
the mind is  able to appreciate the state of contraction of a muscle by
impressions  originating  in the nerves supplied  to  its fibres.  This
power, both of recognizing and governing the muscular movements,
is from our earliest  infancy brought into association  with the impres-
sions derived from the tactile orfjan,  and  made  accessory to its func-
tion ; and the perfection to which  habit, in numerous instances, brings
the sense of touch, is chiefly due  to  an improved  capacity it confers,
of appreciating the impressions made on the organ, in connection with
niceties of muscular movement.
  In animals,  as in man, we may notice the local concentration of the sense in
general  obedience to this relation of  mobility. In monkeys the fingers  are highly
endowed with it, and the papilla; there developed closely resemble those on the human
hand.  The prehensile tails of certain tribes possess great  mobility, can readily be
applied all round an object, and are  largelv supplied  with nerves and papillae.  In
addition  lo this, there is an ab-ence of hair from that surface adapted for contact with
bodies.  In some ant-eaters the  tail is highly tactile, and likewise in the chameleon.
  In the canine and feline races the sense of touch resides  in the paws, which pre-
sent a large papillary structure;  in (he lips, where the whiskers are developed; and
in the tongue.  In  ruminants and solipeds it has its special seat in the lips, which are
long, very movable, and largely supplied with sensitive and motor  nerves.  The
upper lip of the rhinoceros is an excellent example of these  conditions; and, still
more so, the snout of the tapir and the trunk  of the elephant, where the integuments
about the orifice of the nostrils are endowed with exquisite powers both of sense and
motion.
  But nowhere, perhaps, is the sense of touch more acute  than  in the membranous
expansions of the  wings of bats, whereby they are enabled lo traverse dark and tor-
tuous passages, in rapid flight,  without injury.   Spallanzani blinded them with a view
of determining whether sight  conferred  any part of this singular power, but found
that this  mutilation interfered in no respect with the faculty.  They were still able to
fly in the space between suspended threads  without touching them. He could not
conceive it possible that so wonderful an  endowment could depend on any exaltation
of mere  touch, and he resorted to the  supposition of the existence of a sixth sense,
possessed of some  unknown  mode of action.  But Cuvier, with more sagacity, has 
374                       INNERVATION.

referred it to an eminent sensibility of the nerves, which are profusely expanded over
the web of ihe wings.  This membrane seems admirably calculated to receive exact
impressions from the vibralions of the air, and so to be a means whereby the animal
may be informed of the distance and figure of the neighbouring objects, which reflect
or otherwise modify the undulations of the surrounding medium.  It is very probable
that hearing also may be concerned in this power.
  In  man, as compared with animals, the sense of touch is extensively
diffused; but very  interesting differences in its intensity are observable
in different parts of the surface, which have been especially illustrated
by the experiments of Weber.
  These consisted in placing the two points of  a pair of compasses,
blunted  with sealing-wax, at  different   distances asunder,  and in
various directions, upon different parts of the skin of an individual,
who was  not permitted  to see  the  bodies in contact with him.  It
was   then  found,  that  the smallest distance at which the  contact
can be distinguished to be double, varies in different parts between
the thirty-sixth of an inch and three inches;  and this seems a happy
criterion of the acuteness of the sense.   We recognize a double im-
pression on  very sensible  parts of the skin, though  the  points are
very near each other;  while, in parts of  obtuse sensibility, the im-
pression is  of a  single point, although they may  be, in reality, far
asunder.
  In  many parts we perceive  the distance and situation of two points
more  distinctly when placed  transversely than when placed longitu-
dinally, and vice versa.   For example, in the middle of the  arm or
forearm, points  are  separately  felt  at a  distance  of two  inches, if
placed  crosswise; but  scarcely so at a distance of three, if directed
lengthwise to the limb.
  Two points at a fixed distance apart feel as if more -widely  separated
when placed on a very sensitive part, than when  touching  a  surface
of blunter sensibility.  This  may  be easily shown  by drawing  thera
over regions differently endowed ;  they will seem to open as they ap-
proach parts acutely sensible, and  vice versa.
  If contact be more forcibly made by one of the points than by the
other, the feebler ceases to be distinguished ; the stronger impression
having a tendency to obscure the weaker, in proportion to  its excess
of intensity.
  Two points  at a  fixed  distance  are   distinguished more  clearly
when  brought into contact with  surfaces varying in structure and
use,  than when applied to the same  surface, as, for example, on the
internal and external surface of the lips,  or the front  and back of the
finger.
  Of the extremities, the least sensitive parts are the middle  regions
of the chief  segments,  the  arm, fore-arm, thigh, and  leg.   The con-
vexities of the joints are more sensible than the  concavities.
  The hand and foot greatly excel the arm and leg, and  the hand the
foot.   The palms and  soles respectively  excel the opposite surface,
which are even surpassed by the lower "parts of the forearm and leg.
On the palmar  aspect  of the hand the acuteness of  the sense corre-
sponds very accurately with the development of the rows of papilla?; 
NICETIES OF TOUCH.
OIO
and where these papillae are almost wanting, as opposite  the flexions
of the joints, it is feeble.
  The scalp has a blunter sensibility than any other part of the head,
and the neck does not even equal the  scalp.  The skin of the  face
is more and more sensible as we approach the middle line; and the
tip of the nose and red part of the lips are acutely so, and only inferior
to the tip  of the tongue.   This last, in a space of a few square lines,
exceeds the most sensitive parts of the fingers; and points of contact
with it may be generally perceived distinctly from one another, when
only one-third of a line intervenes between them.  As  we recede from
the tip along the back or sides of the tongue, we find the sense  of
touch much duller.
  The sensibility of the surface of the trunk is inferior to that of the
extremities or head.   The flanks and nipples, which  are so sensitive
to tickling, are comparatively blunt in regard to the  appreciation of
the  distance between points of contact.  Points placed  on opposite
sides of the middle line, either before or behind, are better distin-
guished than when both are on the same side.
  The  above are the results obtained  by making the several  parts
mere passive and motionless recipients  of impressions.  They evince
the precision of the  sense in so far only  as it depends  on the organi-
zation of the tactile  surface.   The  augmented  power derived  from
change of po^iiion.of the  object  with  regard to the  surface, is well
illustrated by keeping the hand passive, while the object is made to
move rapidly over it.  In this case the  contact of the two  points is
separately perceived, when so close that they  would, if stationary,
seem as one.   If, still  further, the fingers be made to freely traverse
the surface  of  an object, under the guidance of  the mind, the appre-
ciation of contact will be  far  more exquisite, in  proportion to the
variety of the movements, and the attention  given to  them.   We are
then said to feel, or to examine by the sense of touch.
   How great is the  aid thus capable of being afforded, is manifest in
 the  following  experiment.   With  shut  eyes, and  the hand  still,  let
 another apply to the finger various articles, such as books, paper,
 glass, metals, wood,  cork, &c;  they will  be very  imperfectly dis-
 tinguished.   That our power of varying the force  of contact  adds
 much to the delicacy of touch, is evident from this: that a plane sur-
 face may be made to seem  concave, by drawing it over the passive
 tip of the finger of  a person whose eyes are covered, provided it be
 pressed at first strongly, then lightly, then  strongly again ; or it may-
 be made to seem convex  bv reversing these gradations of pressure.
 But, if the  individual himself is the regulator of the pressure, the
 deception vanishes.   We may obtain some knowledge of the irregu-
 larities of surfaces,  and the shape of objects, by simply bringing the
 tactile organ into contact with them ;  but much more by moving it
 over them  with  attention.  Thus, too, the  infinite diversilies of tex-
 ture may be made distinguishable by the education of tact combined
 with  that of the  muscular sense.   It  is related of  Saunderson, the
 blind professor of mathematics at Cambridge, that he could di.siinguish
 a spurious  from a genuine medal, when the deception had imposed 
376
INNERVATION.
 upon connoisseurs; and  the case of the blind man, referred  to by
 Rudolphi, who  was  able  to  distinguish between woollen  cloths of
 different colours, of course by some slight variety in their texture, is
 rendered  credible by many well-attested examples of a parallel kind.
   Our power of appreciating the weight of bodies,  as well as resist-
 ances in general, depends on  those of estimating, separately and in
 concert, both pressure on  the  tactile  organ and the amount of con-
 tractile energy acting in the muscles.   Weber performed experiments
 to ascertain how far we are capable of judging of weight by the mere
 sense of contact.  He found that when two equal weights, every way
 similar, are placed on corresponding  parts of the skin, we may  add
 to or subtract from one of them a certain quantity without the person
 being able to appreciate the change; and that  when  the parts bearing
 the weights, as the hands, are inactively resting upon a table, a much
 greater alteration may be  made in the  relative amount of the weights
 without his perceiving it, than when the same parts are allowed free
 motion.   For example, 32  ounces  may  thus be altered by from 8 to
 12, when the hand is motionless and supported ; but only by from \\
 to 4,  when the muscles are in  action:  and this difference is in spite
 of the greater surface affected (by the counter pressure against  the
 support) in the former than in the latter case.   Weber infers that  the
 measure of weight by the mere touch of the skin is more than doubled
 by the play of the muscles.  We believe this estimate to be rather
 under than over the mark.
  The  relative  power  of different parts to estimate weight corre-
 sponds very nearly with  their relative capacities of touch.   Weber
 discovered that the lips  are  better estimators of  weight  than  any
 other part, as we might have anticipated from their  delicate sense of
 touch and their extreme mobility.  The  fingers and toes are  also very
 delicate instruments of this description.   The palms and soles possess
 this power in a very considerable degree, especially over the heads
 of the metacarpal and metatarsal bones; while the back,  occiput,
 thorax, abdomen, shoulders, arms, and legs, have very little capacity
 of estimating weight.
  Heat and cold are peculiar sensations excited by alterations of tem-
 perature on the surface of the body.   They are, beyond all other sen-
 sations, of a relative rather than of  an  absolute kind, and are always
 most marked in contrast.   Thus, in the familiar experiment of dipping
 one hand into hot, and the other into cold water, and then plunging
them both into water of an intermediate temperature, the new medium
 will seem  cold to the former and  hot to the latter; and natives of the
 polar  and  tropical regions  of the globe  will respectively complain of
the warmth or chilliness of our  temperate climate when they  visit our
shores.  But it is observable that the  sensations of heat and cold,
 when exalted in  degree, resemble each other very nearly.  The sus-
 ceptibility to both is greatest within  moderate limits;  and impressions
 of either,  when acute and powerful, amount to pain, and soon cease
to be distinguishable from one another.
  Temperature appears higher in degree when  it is applied to a larger
surface : thus, water feels hotter when we put our whole hand into it, 
DURATION OF IMPRESSIONS OF TOUCH.
377
than when we only dip a finger; the extent of the sensation augment-
ing the intensity with which it is appreciated, perhaps by more forcibly
attracting the attention.
  Sensations of temperature have been usually,  and we believe pro-
perly, attributed to  the nerves of common sensation.   These  sensa-
tions are certainly quite different  from touch, both  in their  peculiar
characters and in the source of excitement; but no less may be said
of various other  modifications of common  sensation, to which it is
impossible to assign nerves of special endowment.   The existence of
fibres fitted to be acted on by heat and cold, but by no  other stimulus,
may be fairly doubted so long as they are undistinguishable from those
of touch, both at their origin from the nervous centre and in their
peripheral distribution.  Still, however, it may be noted that in certain
states of paralysis, the sensibility to heat and cold may be destroyed,
while common sensation and touch remain.*
  The sensation of  tickling, tingling, itching, and many others allied
to them, are also referrible to the nerves of touch.  Respecting tickling,
it has been well observed by Weber, that it  is most apt to be excited
in parts of feeble tactile power.
  Impressions made on the organ of touch, as on the other organs of
sense, continue perceptible for a period more or less prolonged after
the stimulus  has  ceased to be applied.  The sting of a smart blow
does not soon subside; and even the simple contact of any object, as
a ring or an  article of clothing, with  a part of the skin, if long con-
tinued enough, leaves, after its removal, an impression of its presence,
which is apt  to deceive the individual  for a  considerable time.  The
influence of habit on  sensation  in general, may be well illustrated  in
the case  of the nerves of common sensation and of touch.   Impres-
sions  sufficiently strong in the first instance to arouse the attention,
soon  become feeble, and in time  wholly disregarded, if continued
uniformly or frequently repeated; although the mind can still,  at any
moment, take cognizance of them by a  voluntary effort.  The sen-
sations of heat and  cold may, by long  habit, in like manner come to
be  unnoticed, or lightly heeded, within certain  bounds.  This is a
matter of common experience, and may be exemplified in the case of
the lower classes of society, among whom the privation of the com-
forts of warm clothing and lodging, and the  absence of the mistaken
luxury of over-heated rooms, are compensated for by the possession
of that  diminished  susceptibility to cold, under slight exposures,
which is so remarkable in those subject, in a moderate degree, to the
inclemencies of the  seasons.
  Little  needs be said of the subjective sensations pertaining to  the
nerves now  under consideration.   They are among the best known,
and most familiar  in  the body.   The  peculiar tingling of a limb
" asleep," which commonly depends  on  pressure on its  trunk, may
result from morbid  changes in the centre;  as may likewise sensations
of formication, or the creeping of insects, and those of itching, of heat,
of chilliness, &c, and lastly of pain of various kinds.

   * See an instructive  case by Dr. W. Budd, in the Med. Chir. Trans., vol. xxii.
       25 
378
INNERVATION.
  Besides the references in the foot-notes and the various treatises on Physiology and
general Anatomy already cited, we may refer on the subject of the preceding chapter
to Rudolphi, Grundriss  der Physiologie, band ii.;—Weber, de  pulsu, resorptione,
auditu, et tactu; Lips., 1834;—Breschet et Roussel de Vauzeme, Ann. d. Sciences
Nat., 1834, torn, i.;—Schwann, Mikroskop. Untersuchungen;—Eble, die Lehre von
den Haaren;—Gurlt,  Mullers Archiv., 1836;—Van Laer, de structura capillorum
humanorum; Traj. ad Rhen., 1841.
                         CHAPTER  XV.

OF TASTE.--OF THE  MUCOUS MEMBRANE OF THE TONGUE, AND  OF ITS
  SIMPLE AND COMPOUND  PAPILLiE.--NERVES OF TASTE.--NERVES OF
  TOUCH IN THE TONGUE.—SEAT AND PHENOMENA OF TASTE.

  The sense of taste is subservient to  the nutritive function by guid-
ing us in the discrimination of the qualities of our food, and is there-
fore appropriately situated in  the mouth,  the  antechamber  to the
digestive canal.   The food being delayed more or less in this cavity,
is brought, by the movements  to which it is exposed, into intimate
and varied contact with the surface; and, its properties being ascer-
tained while it is still under  voluntary control, we are able to reject
it or to  propel it onwards, according to the impression  produced on
the nerves of taste.
  The mucous membrane of the tongue, as the principal seat of the
sense, will now demand description.    The muscular apparatus of this
organ, though increasing its powers  of taste, relates  chiefly to its
employment  in the processes of mastication and deglutition, and will
therefore be  considered at a future page.
  In  the mucous membrane of the tongue we find a chorion, a papil-
lary structure, and an epidermis or epithelium;  all corresponding, in
essential characters,  with  the same constituents of the skin.
   The chorion, or cutis, is tough, but thinner and less dense than in
most parts of the skin: it receives the insertion of all the intrinsic
muscles of the tongue, which send up their fibres to it in small separate
bundles, so that the surface of the tongue is exceedingly mobile, even
in its minute portions, and its powers as an organ of touch are thereby
much exalted.  The termination of the muscular fibres in the  fibrous
tissue of the chorion can be well seen in thin vertical  sections.  The
chorion  contains the ramifications of the vessels and  nerves  from
which the papillary structure   is supplied.   Both the  arteries and
veins form plane  plexuses, open on all sides, like those of the  skin,
and  respectively  connected  with the vessels of the papilla?  above
them.
   The papillary structure has, in general, this peculiarity, that it is
not concealed under the  epithelium, but stands out  freely from the
 surface, like the villi of the, intestinal tube, occasioning the familiar 
MUCOUS MEMBRANE OF THE TONGUE.
379
roughness of the tongue.   This, however, is to be taken with the
limitations hereafter to be detailed.
   The  epithelium of the tongue is of the scaly variety, and in this
respect  resembles the cuticle.   Like the cuticle also, it undergoes
certain modifications in its mode of aggregation in different localities.
In  general it is much  thinner than in the skin, so that  the intervals
between  the  large  papillae are  not filled up  by it, but each has  a
separate  investment, from  root  to summit.   The  continuity of the
epidermis over the  whole organ  admits of  easy  demonstration by
maceration, or boiling; by which it  it detached  entire, bearing the
print of  the  surface  below, on  which it has been moulded.   The
deeper epithelial  particles  may  sometimes be detached  as a separate
sheet, corresponding to the so-called rete mucosum; but these par-
ticles never  contain  colouring matter.  In animals which have the
epithelium of the tongue much thicker than in man,  it admits of beino-
separated with care into a great many layers, at the will of the  ana-
tomist.    The density of the epithelium  is evidently a  provision  to
defend  the invested structures from the bad effects of the pressure and
friction to which they are exposed during mastication,  and hence it
is greatest about the middle  of the
upper surface of the organ.   It is
here that the "fur" usually accu-
mulates most in disease, being,
in fact, no other than a depraved
and over-abundant formation  of
the  epithelium.
   Three  principal  varieties of
papilla are visible with the naked
eye  on  the dorsal aspect of the
tongue.  These are, 1, the circum-
vallate or calyciform, eight to ten
in number, situated in a V-shaped
line  at  the  base  of  the  organ
(fig. 94, a); the fungiform, scat-
tered over the surface, especially
in front of the circumvallate, and
about the sides and apex, b; and
the conical or filiform, much the
most numerous,  studding  most
of the surface, though most large-
ly developed in  the central  part,
d.   These three  varieties  will
require  a  separate description;
they are very distinct from one
another  if well-marked speci-
mens are  selected ; but, as might
be expected, there are  many in-    „,
      r.,.'     ,     i- ,  ,,      , longue, seen on its upper surface:—a. One of
termediate IOrmS by Which they   the  circumvallate papilla, b.  One of the fungi-
sppm rn  rnn ;rr,r>f»rr.pnfihlv intr»   form papillne.  Numbers of the conical papilla;
Seem TO  run lmperCeptlDly into   are  seen about d, and elsewhere,  e. Glottis, epi-
One another   Wp mav nrpmisp    glottis, and glosso-epiglottidean folds of raucous
unt, aiiuuiei.   vve UJdy pieuu&e,   membrane.-From Soemmering.
 
 380                       INNERVATION.

 however, with  regard to them all, that although they appear to have
 been hitherto regarded as simple papillae, analogous to, though larger
 than, those of  the  skin, yet we have found  them to be compound
 organs, clothed with  secondary, simple, and much more minute pa-
 pillae, concealed under the epithelial investment, and  scarcely or not
 at all visible until this covering is removed.
   In their compound  nature they present much resemblance to the
 intestinal villi of  the  rhinoceros and other large animals.   We  have
 further ascertained  the existence of  similar minute papillae, inter-
 spersed very unequally among the compound forms, as well as occu-
 pying much of  the surface behind the circumvallate variety, where
 the  compound  forms do not exist.  These  minute papillae seem to
 have hitherto escaped detection, in consequence of their being  com-
 pletely buried and concealed under  the common sheet of epithelium.
   If we examine  the  mucous  membrane immediately  in front of the
 epiglottis, we find it  perfectly smooth, almost transparent, and supplied
 by capillary vessels spread uniformly under the surface,  and connected
 with simple  plane  submucous plexuses of  arteries and  veins:  here
 the  papillary tissue  is  undeveloped.   Further  forwards, however,
 where the  membrane still seems smooth, the  plexus of arteries be-
 neath it sends upwards, at pretty regular intervals, a series of twigs,
 each of which  terminates in one or two  capillary loops, sometimes
 dilated in the bend, from which a small vein returns the  blood to the
 submucous venous plexus.   These  loops correspond to those  of the
                                            simple papillae  of the
                                            skin, p. 359; they sup-
                                            ply simple papillae, bu-
                                            ried  under  a  common
                                            investment of scaly epi-
                                            thelium,   that   differs
                                            from  the cuticle  only
                                            in its  greater  tenuity
                                            and moistness.  On the
                                            removal of this delicate
                                            epithelium  by macera-
                                            tion, the  papillae stand
                                            out free from the mem-
                                            brane, and  are seen to
                                            consist of  an  envelop
                                            of basement membrane
                                            (p.  353), enclosing a
                                            parenchyma obscurely
                                            granular, with the ca-
                                            pillary   loop  already
                                            mentioned.  Aftermuch
                                            care, we have not been
                                            able  to  see  nervous
                                            tubules  within  them;
but they must exist under  some important modification, which most
Fig. 95.
 Simple papillae near the base of the tongue :—a. a. concealed
under the epithelium; b. uncovered by it.—Magnified 10 diame-
ters, b.o. Arterial twig, supplying their capillary loops, v. Vein
The vessels are all contained within the line b. b, of basement
membrane,  c, c. Deeper epithelial particles resting on the base-
ment membrane, d. Scaly epithelium on the surface.  The
granular interior of the papilla: is represented at e. c. Papillte
in which the basement membrane is not visible; and the deep
iayer of epithelium seems to rest on the capillary loop.—Magni-
fied 200 diam.                               8 
COMPOUND PAPILLJE OF THE TONGUE.
381
probably consists in the absence of their characteristic white substance
of Schwann.   These simple papillae are represented in fig. 95.
   The circumvallate papilla (fig. 94, a, and fig. 96) consist of a cen-
tral flattened  projection of the mucous membrane, of a circular figure,
and  from 2V  to ^ of an inch  wide, surrounded by a tumid  ring of
about the same elevation, but less
diameter, from  which it is sepa-                F'g- 96-
rated by a narrow circular fissure,
with, it is said, a few mucous ducts
opening  at   the  bottom.   In  the
smaller examples this fissure exists
only on  one side.   The  surface of
both centre and border is smooth,
and  invested  by scaly epithelium,
concealing a  multitude  of  simple
papillae, in all respects similar to
those just described.
   About the  point where the two lines of circumvallate papillae meet,
there  is  usually one with the  fissure so large  and deep as to  have
received the  name of foramen cacum.   The central part is frequently
small, or elongated and  thrown on  one side of the foramen.   In the
specimen next  represented (fig. 97),  this is  shown  covered  with
                                Tig. 97.
 Vertical section of one of the circumvallate
papillae:—a. Central part.  b,b. Border, c, c.
Fissure between centre and border. The se-
condary papillae are seen covered by the epi-
thelium. Similar papillae are seen, d, d, on the
membrane beyond.—Magn. 8 diam.
  a. Compound papillae on ihe side of the foramen caecum, injected:— a. a. Arterial twigs. v,i\
Viens. The capillary loops indicate the simple papillae; in one of which, b, the injected matter has
bi en extravasated within the basement membrane of the papilla, the outline of which is thus dis-
tinguished  c. Capillary plexus, where no papillae exist, e, e. External surface of the epithelium of
the papilia.— Magn. 15 diam.
  b. One of the simple papillae of a.:—a. v. v. Arterial and venous sides of the capillary loops  b.b.
Basement membrane,  d. Deeper epiihelial particles resting on the basement membrane, s. Scaly
epithelium on the surface.—Magnified 300 diameters.

secondary papillae, having  all  the characters  of those  above men-
tioned.  In its interior we failed to detect any  nerves  provided  with
white substance.   In  this region of the tongue fissures  and papillae of
irregular size and shape  are  often met with, and mucous glands are
disseminated beneath  the surface. 
382
INNERVATION.
  The fungiform papillae (fig. 94, b, and fig. 98) are scattered singly
among the filiform papillae, chiefly on the sides and tip of the tongue,
and  very sparingly in the middle of the  dorsal  region.   They are
usually narrower at their base than summit, where they are from 2V to
3V of an inch in diameter.   Like those last described, they are clothed
Fig. 99.
  a. Fungiform papilla, showing the secondary papillae on its surface, and at a its epithelium cover-
ing them over.—Magnified 35 diameters.
  b. Another, with the capillary loops of its simple papillae injected,  a.  Artery.  11. Vein.  The
groove around the base of some of the fungiform papillae is here represented, as well as the capil-
lary loops, c, c, of some neighbouring simple papillae.—Magnified 18 diameters.

with  simple papillae;  and their investing  epithelium is  so thin, that
the blood, seen through it, gives them  a red colour,  usually sufficient
to  distinguish them  from  the  filiform ones  among which  they lie.
They contain nerve-tubes, having a loop-like arrangement.
   The compound papillae of  the third variety (fig. 94,  d, and figs. 99
and 100) are of  the average length of T'o  of  an inch, and, as their
name  implies, are more or less conical or filiform in  shape.   They
                                              are distinguished, more-
                                              over, by their  whitish
                                              tint,  derived  from the
                                              thickness and density of
                                              their epithelium.  This,
                                              indeed, frequently com-
                                              poses two-thirds of their
                                              length,  being sent  off
                                              from the sides and sum-
                                              mits of their  secondary
                                              papillae in long pointed
                                              processes,  which   are
                                              immersed in  the mucus
                                              of the  mouth, and may
                                              be moved in  any direc-
tion, though they are generally inclined  backwards.   These epithelial
processes are more stiff, according as the particles of which they con-
sist approach  more nearly to the dense texture of hair; and a few
among them actually  enclose minute  hairs, pointed  at the  end, and
provided in  some cases with  an  extremely fine central canal.  One of
the largest of these  we found TV of an inch long, and  from 20V0 t0
 Various forms of the conical compound papillae, deprived of
their epithelium :— a, b, and especially c. are the best marked,
and were provided with the stifTest and longest epithelium;
their simple papilla; are more acuminated,  d, approaches ihe
fungiform variety :  e, /, come near the simple papillae —Magni-
fied 20 diameters. 
             STRUCTURE OF THE SECONDARY PAPILLA.          383

s^oo- of an inch thick (fig. 100,  2).   The others have an imbricated
arrangement of the particles in various degrees, which will be under-
stood without detailed description on reference to figure 100, 3, 4, 5.
Many of them  may be  regarded as soft  or uncondensed  hairs,  and
preserve the same thickness for a considerable length.
                                 Fig. 100.
 a. Vertical section near the middle of the dorsal surface of the tongue :—a, a. Fungiform papillae.
6. Filiform papillae, with their hair-like processes, c. Similar ones deprived of their epithelium.—
Magnified 2 diameters.
 b. Filiform compound papilla;:—a. Artery,  v. Vein. c. Capillary loops of the secondary papillae.
b. Line of basement membrane, d.  Secondary papillae, deprived of e, e, the epithelium. /.Hair-like
processes of epithelium capping the simple papillae.—Magnified 25 diameters,  g. Separated nucleated
particles of epithelium, magnified 300 diameters.
 1, 2. Hairs found on the surface of the tongue.  3, 4,5. Ends of hair-like epithelial processes, show-
ing varieties in the imbricated arrangement of the particles, but in all a coalescence of the particles
towards the point. 5, encloses a soft hair.—Magnified 160 diameters.

   The structure  of the secondary papillae, from which these hair-like
processes pass off, differs somewhat from that of the simple papillae
in  the  situations previously described.   This  difference  consists  in
their larger size  and more pointed  form, as well as  in their  greater
stiffness and elasticity;  the latter  quality depending on  the abundant
yellow fibrous tissue  they contain, and which, with  a wavy, almost
spiral character,  has a general longitudinal direction (fig. 101, c, c, c).
They are commonly found to contain tubular nerve-fibres, which we
have on several occasions, but not always, seen to terminate  in loops
(fig. 101,  a, b, c).   We have  usually found it easiest to  distinguish
the tubular fibres in the  papillae at the front of the tongue. 
384
INNERVATION.
   The reader will  at once recognize the broad and obvious distinc-
tion between the papillae last described and all the other varieties, and

                                Fig. 101.
 a  Secondary papilla of the conical class, treated with acetic acid :—a. Its basement membrane.
6. Its nerve-tube forming a loop. c. Its curly elastic tissue. The epithelium in this instance is not
abundant; but the vertical arrangement of its particles over the apex of  the papilla is well seen, d,
and illustrates the mode of formation of the hair-like processes described in the text.—Mag. 160 diam,
 b.  A similar papilla, deprived of its epithelium :— a. Basement membrane,  b. Tubular fibTe. pro-
bably forming a loop, but its arch not clearly seen, c, c. Elastic fibrous tissue at its base and in its
interior.—Magnified 320 diameters.
 c.  Nerves of a compound papilla near the point of the tongue, in which their loop-like arrangement
is distinctly seen.—Magnified 160 diameters.

will probably surmise, on structural  grounds, that  they can scarcely
share in the reception of impressions  which depend on the contact of
the sapid material with the papillary tissue.  The comparative thick-
ness of their protective covering, the stiffness and brush-like arrange-
ment of their  filamentary productions, their greater development in
that portion of the  dorsum of the tongue which  is chiefly employed
in the movements of mastication,  all evince the subservience of these
papillae to the latter function rather  than to that of taste; and it is
evident that their isolation and partial mobility on  one another must
render the delicate  touch with which they are endowed more available
in directing the muscular actions  of the  organ.    The  almost manual
dexterity of the organ in dealing with minute particles of food is pro-
bably provided for, as far as sensibility conduces to it, in the  struc-
ture and arrangement of these papillae.
  The simple  papillae on the base  of  the tongue, and  those clothing
the circumvallate and fungiform papillae, do not appear to differ from
one another  in any important  structural condition, notwithstanding
their variety of outward form and arrangement in the compound organs: 
PRECISE SEAT OF TASTE.
385
their epithelium, though of the scaly kind, is  very thin, and would
easily permit  the  transudation of sapid  substances dissolved in the
mucus of the mouth.  The softer and perhaps cellulated interior of
these  papillae may have a further influence on the act of sensation.
With regard to the use of the singular configuration of the circum-
vallate and  fungiform papillae, it may be conjectured that the fissures
and recesses about their base  are  designed to arrest on their passage
small portions of the fluids in which, the sapid materials are dissolved,
and thus to  detain them in  contact with the most sensitive parts of
the gustatory membrane.
   We may here allude to a certain gradation that is apparent from
the papillae  of touch, through those of taste, to the absorbing villi of
the small intestines.   Touch  shades into taste, and at a lower  point
sensibility is lost.   In the tactile  papillae,  the  excitant of the nerves
merely comes into contact with  the exterior  of a thick epidermic
covering: in those of taste,  the epithelium  is permeated by the special
excitant  of the nerves; while  the intestinal villi  are still more  elabo-
rately and exclusively organized for  absorption.   Another class of
papillae might be here spoken of  in conjunction with those of  taste,
as will be seen at a future page.
   On the precise seat of Taste.—Authors  differ considerably on this
subject:  some limit it to the hinder part  of the  tongue, about the root
and sides;  some extend it more or less over the whole dorsal  aspect
and to the tip; others describe it  as existing also on the soft palate;
while Magendie is of  opinion that the pharynx, gums, and teeth are
likewise  possessed of it.  This  contrariety, while it shows the diffi-
culty of the subject, may be in some measure explained  by the inde-
finiteness of tastes when  faintly perceived by  small portions  of the
surface, by the influence on taste of the commonly associated  senses
of touch  and smell, by some  diversities really existing  in different
individuals, and  by the ambiguity necessarily attending experiments
on special sensation  among the lower  animals.   As the subject is
interesting in its bearing on the question of the nerves  of taste, we
shall here briefly consider it.
   Touch, as it exists in the tongue and  other highly endowed parts,
discovers to  us not  merely the presence and physical properties of
bodies, but  their actual position:  we recognize  the situation  of the
impression  in reference to the whole organ, by virtue  of  a  power
common  in  a greater or less degree to all  sensitive nerves (p. 352).
Every one who has attended to the effect of sapid substances applied
to small  separate parts of the tongue must  feel  that a similar capacity
of assigning the  position  of flavours accompanies the  sensation of
taste;  and on this power in the nerves of taste, aided, as is usually
the case, by the nerves of touch, we greatly rely for the determination
of the question before us.
   In the first place, all  allow that acute taste resides at the base of
the tongue,  over a region, of which the circumvallate papillae may be
taken  as the centre, and  also  on the sides near  the base.   These
parts are supplied solely by  the glossal twigs of the glosso-pharyngeal
nerves. 
386
INNERVATION.
  Secondly, some writers, among whom are Valentin and Wagner,
believe the middle and anterior parts of the dorsum of the tongue to
be usually incapable of appreciating flavours; while numerous others
hold the contrary opinion, with which  our own careful  and repeated
experiments, on  other persons as  well as ourselves, quite  accord.
Sour, sweet, and bitter substances applied  to the sides, and especially
to the  tip, of  the protruded tongue, we  find to be  at once  distin-
guished; though, when  placed  on the middle of the dorsal region,
they make  little or no impression till pressed against the roof of the
mouth.  In  the latter case, however, the taste of sugar is sufficiently
distinct, and referred definitely to  the spot  on which it is laid ; so that
its being tasted does not  depend on its diffusion or  removal from the
central to the  circumferential parts, as some imagine.   The  region
now spoken of is supplied almost solely by the lingual branch of the
fifth  nerve,  though Valentin has described a twig of the glosso-
pharyngeal running on the under  surface towards the tip.
  We conclude generally, with regard to  the tongue, that the whole
dorsal surface possesses taste, but especially the circumferential parts,
viz., the base, sides, and  apex.   These latter regions are most favour-
ably situated for testing the sapid qualities of food: while they are
much less exposed than the central part, to the pressure and friction
occasioned by the muscles of the tongue  during mastication.   The
central region, as a  whole, is more strongly protected  by its dense
epithelium, and is rougher, to aid in the comminution and dispersion
of the  food.
  Thirdly, the soft palate and its arches, with the surface of the ton-
sils,  appear to be endowed with taste in various degrees in different
individuals.   Admirault  and Guyat affirm  that the sense is acute in
a spot about the centre, above the uvula;  and in some individuals it
has so appeared to us.  We have also found evidence of the existence
of taste on the sides and  arches of the soft palate in  some individuals,
but not on  the pharynx, gums, or  elsewhere.  The  soft  palate and
its arches are supplied by the posterior palatine branches of Meckel's
ganglion, and  sparingly by the glosso-pharyngeal nerves.
  Of the JVerves of Taste.—Taste having been shown to  exist inde-
pendently in  parts supplied, on the one  hand solely by the glosso-
pharyngeal nerves, on the other solely  by  the lingual branches of the
fifth  pair, it follows,  as a direct consequence, that these nerves  must
respectively participate in the sense; and  there is, besides, reason to
attribute a share  to  the  palatal branches  of the fifth.  Amid  many
conflicting, and some quite irreconcilable  statements on this disputed
point,  with which it  would be needless to distract the reader's atten-
tion, the weight of evidence derived from other sources seems to be
much in favour of the above conclusion.
  The origin and connections of the glosso-pharyngeal nerves, which
will  be described at a future page, may be referred to in connection
with this question.   Rapp found  no lingual branch of the fifth in the
tongue of the  swan or parrot, both of  which have acute taste.   The
glosso-pharyngeal and par vagum supplied the organ.
  Evidence from Experiments.—From observations on the effects of 
NERVES OF TASTE.
387
section of the glosso-pharyngeal nerves in dogs, Panizza, and, subse-
quently, Valentin and Wagner, concluded that taste was completely
lost after  their division, and, consequently, that these are  the  sole
nerves of the sense.   But in such an inquiry negative results have far
less value than positive ones; and we therefore consider the experi-
ments of Muller, Gurlt, and Kornfeld, and those of Alcock and Reid,
who all agree that decided indications of taste remained after these
nerves had been cut, as proving that the lingual branches of the fifth
share in the sense.   Mtiller,  Gurlt, and Kornfeld, however, failing to
find signs of taste after the lingual branches of the fifth were divided,
concluded too  hastily that these are the  sole, or by far the principal
nerves of the sense,  in opposition to the  experiments of Panizza and
his followers, the positive evidence of which in this  regard carries
greater weight.  The experiments of Dr. Alcock directly tend to re-
concile these  inconsistencies.   He found that though taste remained
after  dividing  the lingual branches of the fifth, yet it seemed  com-
pletely lost in the anterior part of the tongue.   Besides, it is not impos-
sible that the rude injury inflicted in these contradictory  experiments
on either  the glosso-pharyngeal or the lingual branch of the fifth might
temporarily deaden the sense of taste in the other, in a way somewhat
similar to that, whatever it be, in which  loss of smell impairs taste.
Valentin admits that one of the dogs in which he had cut the glosso-
pharyngeal nerves was able to taste a fortnight afterwards;  a period
quite too  short to have allowed reunion  and  restoration of function
to the nerves, and making it likely that  the sense had been only ap-
parently,  and not really lost.
  Evidence from Disease.—In some cases loss  of common  sensation
consequent on disease of the fifth nerve  has been reported as being
attended  with  loss of taste  (Bishop, Med. Gaz., 1833; Romberg,
Mullens Archiv., 1838, heft  iii.); in others, taste  appears to  have
been  preserved (Noble, Med. Gaz., vol. xv. p. 120;  Vogt,  Mullens
Archiv., 1840, p. 72): on the other hand, taste has been sometimes
lost while common  sensation in the  tongue remained (Noble, Med.
Gaz., vol. xvi.).   We would interpret  the apparently contradictory
evidence  of these cases by one which we have ourselves lately  wit-
nessed, and  which  will  be  found  to  accord remarkably with the
foregoing views.   A  middle-aged man suffered for  eight years from
complete  loss of sensation in all parts supplied  by the fifth nerve on
the left side, with the exception of the forehead.  The left eye  was
lost by destructive inflammation: the tongue was quite without feel-
ing on the left side.   On experimenting  on his  sense of taste, it was
found  to  be clearly absent in the  anterior and middle  part of the
affected side; but to  be present behind, in the region supplied by the
glosso-pharyngeal.   He tasted acutely enough  on the other side  in
front.
   Blumenbach and others relate cases of congenital deficiency of the
tongue, in which taste existed.  These would show that  taste resides
in other  parts of the mouth  besides  the  tongue, if it were not  very
probable  that a portion of the base of the organ with its gustatory
papillae, supplied by the glosso-pharyngeal nerves, existed  in these 
388
INNERVATION.
individuals.  Without accurate dissections of the parts, such instances
throw little light on the question.
  The tongue, as an organ of mastication, is provided, with the sense
of touch;  the  anterior portion,  and especially the  sides  and tip,
possessing this sense in an eminent degree.   Division of the lingual
branches of the fifth nerves in animals is attended with  evidence of
severe pain, and is immediately followed by loss of sensation  in the
front part of the organ; while cases of disease of  the fifth nerve in
the human subject are  marked by loss of sensation in the tongue, in
common with the other parts which the nerve supplies.  The experi-
ments of Alcock and Reid further show,  that mechanical irritation of
the glosso-pharyngeal nerve in animals is accompanied with manifest
pain.   Hence there can be no doubt that the lingual branches of the
fifth pair are the chief nerves of touch to the tongue, while the glosso-
pharyngeal nerves furnish the feeble common sensation existing in its
hinder part.
   Conditions of Taste.—Taste may be produced by a mechanical or
chemical excitation of its nerves.   Dr. Baly has observed that a smart
tap with the fingers on the tip of the tongue causes a taste sometimes
acid, sometimes saline, which lasts several seconds; and galvanism
acts in a similar way.   Any tasteless substance pressed upon the base
of the tongue occasions a  bitter sensation, and, if prolonged, a feeling
of nausea.   These phenomena show that the sensation of taste follows
excitation of its nerves, however produced: and analogous ones have
been  observed in  connection  with the other sensitive nerves.  But
sapid substances cause taste only when  dissolved and  made to per-
meate the tissue of the papillae, so as to come into contact with their
nerves.  This is proved by the fact that no insoluble substance admits
of being tasted, and constitutes a  broad distinction between taste and
touch; which in some respects approach  each other very nearly, par-
ticularly in regard to the effects of strong chemical agents  on their
respective nerves, producing a harsh, pungent, burning taste ox feel.
Taste, like touch, is much influenced by the extent of surface acted
on: and it is also heightened by  the motion and moderate pressure of
the substance  upon  the gustatory membrane.  By the  latter  move-
ments, the mucus  and  outer layers of the epithelium  are  removed,
and the sapid  material is brought into closer contact with the papillae.
The act of swallowing seems further necessary to the perfect  appre-
ciation  of flavours.   This  is partly explained by considering  how
much the concurrent exercise of smell exalts the sense of taste.  Most
sapid substances, though in different degrees, affect the nose through
the throat on being swallowed;   and  we are  thus  led to attribute to
taste much of what is in reality due to smell.  The nurse's device of
holding  the nose  of the  child  in giving it disagreeable medicine,
though  commonly said to  deaden  taste, seems rather serviceable by
excluding  smell.  Thus  tested,  taste is a  less  acute and  definite
sensation than most persons imagine.  Nevertheless the difficulty of
discriminating between the two senses indicates a real, though obscure,
alliance between them, rendered  closer by habit and association.
   The impression of cold  air deadens the sense of taste, and has, we 
CONDITIONS OF TASTE.
389
believe, been the source of some of the discordance in the recorded
results of experiments'.   Cold acts similarly on touch.
  Do taste  and touch co-exist in any of the papilla!—A papillary
structure is, essentially, an arrangement for increasing  the  surface by
which a membrane may have contact with external substances ; and,
while the analogy with the skin leaves no doubt that this structure in
the tongue is concerned in the exquisite touch enjoyed by  the organ,
it is almost  as certain that it is also concerned in taste.   The question
then arises whether touch and taste reside in the same papillae or in
distinct ones.
  Now it is possible, as far as we know, that nerve-fibres of different
endowments may be  associated in the  same papillae, and therefore
that one and the  same  papilla may possess both capacities.  Taste,
however, it is evident, demands a more delicate  external apparatus
in connection  with its nerves than touch; so  that touch might be ex-
ercised with an  apparatus adapted  to  taste, though not in all cases
the reverse.   As far, therefore, as regards the simple  papillae  at the
base of the tongue, and those covering  the circumvallate  and fungi-
form varieties, it seems impossible, in our ignorance of  any anatomical
distinction between the nerve-fibres of the two endowments, to decide
whether the two senses are or are not resident together in the same
papillae.   But there are good grounds for supposing that the conical
or filiform papillae are not designed for taste.   They are most largely
developed  in  a part of the tongue where taste is feeblest, and are
there intermixed with a number of fungiform  papillae  sufficient to
account  for the little that  exists.   Their structure  and position, as
already remarked, lead to  the same conclusion.  It may  be  added,
that, in the lion, where these papillae are capped with spines, so thick
and rigid as totally to incapacitate them for  taste, they are furnished
at the base with an additional tuft of soft secondary papillae, that seem
specially adapted  for the latter  function.  It is possible that  certain
soft papillae, which we have  frequently seen  springing up about the
base of the less developed filiform  ones in  the human tongue, may
contribute, in  a similar manner, to the sense  of taste.
  Are the varieties of taste referable to the varieties of  the papilla!—
It has been  imagined  that the differences of form met with  in the
papillae might be in some special relation to the leading varieties of
tastes, as the bitter, sweet, sour, &c;  but the careful  experiments of
Horn on this interesting point can scarcely be considered  as tending
to  establish such a correspondence.   The  difficulties, however, of
experimenting are so  great, that neither can they be said to disprove
it:  for a considerable  extent  of impression is necessary to ensure a
perception sufficiently definite to be relied on ;  and the different papillae
are for the most part too much intermingled  to admit of several of a
similar kind being tested apart from others.   The most that can be
deduced from Horn's observations is, that more than three-fourths of
the substances he applied to the circumvallate papillae, including, we
suppose, the simple papillae  we have described on the neighbouring
surface,  excited a bitter taste, or one in which the bitter  was  asso-
ciated with some other, especially an alkaline or saline flavour; and 
390
INNERVATION.
that on the region where the filiform papillae abound the majority of
substances tasted acid, or  acid with a mixture  of bitter or sweet.
In regard to the fungiform variety no decided  results were obtained.
These facts will perhaps help to explain the effect of the act  of swal-
lowing in modifying and heightening flavours, since the food is much
more  completely brought into contact with the papillae on the base of
the tongue during that act.
  After-tastes.—Impressions of taste remain longer than those of the
other  senses, because the fluids exciting them  must of necessity con-
tinue  for some time in contact with the nerves after having saturated
the intervening papillary investment.  For the same reason it is  diffi-
cult to say how  much of the taste that lingers after the substance has
apparently left the mouth is due to  the excitation of the nerves by
particles still  remaining in the  papillae, and how much to that  slate
of the nerves, which, in all the  senses, prolongs the perception,  after
the mere excitation  has ceased.   The  taste  left  in the mouth by
many substances is, however,  very different  from that which  they
produce  in the  first instance.   Horn  has remarked that this after-
taste is usually bitter;  while, with one of the  most bitter substances
known, viz., tannin, it is sweet.  This circumstance appears  to show
something in taste  corresponding to the complementary colours in
vision, and seems dependent on a state of the  nerves which, for want
of a better word, may be termed one of exhaustion, consequent on
their previous stimulation.   It will illustrate the cause of many fami-
liar phenomena  of taste; such as the effect some flavours have in ex-
alting, modifying, or destroying our appreciation of others.  Repeated
over-stimulation of the nerves by the same substance exhausts their
excitability by that or similar substances for some time afterwards.
  There also appear  to be  relations  between certain  varieties of
taste,  which, though not classified or described by philosophers, are
instinctively perceived, and  constitute the foundation of the art of
cookery.  Attention and study given to the perceptions of this sense
greatly enhance their delicacy.
  Little  is known of the subjective phenomena of taste, or those
dependent on excitation of the  nervous  apparatus  of the sense by
internal causes.   The various tastes which are  experienced in disease
are probably  occasioned by depraved secretions in the mouth acting
as foreign substances on the papillae.   The epithelium of the  tongue,
it is well known, is very prone  to accumulate in the form of sordes,
loaded with unnatural materials; on the removal of which, the natural
taste is, in a great measure, restored.   Magendie observed that dogs,
after the injection of milk into their veins, licked their lips, and gave
other  signs of tasting.   Such phenomena, if uniformly present, might
be occasioned by the transudation of the fluid  from  the vessels to the
nerves of the papillae.

  On the subject of taste we refer to the general treatises  already cited; to Magendie's
Physiology; Rudolphi's Physiology; Horn.uber den Geschmackssinn des Menschen,
Heidelberg, 1825; Panizza, Richerche Sperimentali sopro i Nervi, 1834, given by Dr.
G. Burrowes in  Med. Gaz., vol. xvi.; Dr. Alcock, Med. Gaz., Nov. 1836; Dr.Jno.Reid,
Brit, and For. Med. Rev., vol. v. p. 309; Valentin, de funct. nerv., p. 116. 
OF SMELL.                       391
                        CHAPTER XVI.

OF SMELL.--CAVITIES OF THE NOSE.--STRUCTURE OF THE NASAL MUCOUS
  MEMBRANE.--OLFACTORY REGION.--NERVES OF THE  NOSE.—CONDI-
  TIONS OF SMELL.

  This sense, designed to acquaint us with the  odorous qualities of
particles  suspended  or dissolved in the atmosphere,  is seated in a
portion of the nasal mucous membrane to which the air has access
during ordinary breathing, and it  may fairly be regarded as appended
to the  respiratory organ, much as the sense of taste has been seen to
pertain to the digestive apparatus.   But though it may serve to pro-
tect the lungs from the inhalation of deleterious gases, its principal
use appears to be that of seconding the impressions of taste in con-
veying intelligence of the properties  of food ; for it almost invariably
happens, that food possessing a decided flavour has likewise  a not
less characteristic smell.
   Unlike the organs of touch and taste, that in which  smell resides
has no capacity of movement in relation  to its ordinary stimuli;  a
deficiency quite supplied by the  expansion  of the chest in breathing,
which carries the stream of odorous  particles over the sentient sur-
face.
   The nose consists, 1, of two chief cavities  or nasal fossa separated
from one another by a vertical, bony, and  cartilaginous septum, and
each  partially subdivided, by the spongy or turbinated bones, pro-
jecting from the outer wall, into  three passages or meatuses: and,  2,
of subordinate chambers, cells, or sinuses, of irregular  size, hollowed
principally in the  ethmoid, sphenoid, frontal, and superior maxillary
bones, and  communicating by narrow apertures with one  or  other
meatus.
   The nasal fossa are lofty and of considerable depth, but much nar-
rowed in lateral extent by the projection of the  spongy bones towards
the septum,  which they almost  touch.  They open in front by the
nostrils, which, by their horizontal position, direct the air, as  it enters,
towards  the  upper  region, where the sense of smell  is developed ;
behind, they lead, through a vertical slit on  each side, the  posterior
nares  or nostrils, into the  upper compartment of the pharynx, above
the soft palate, into which the food never penetrates, which is strictly
a part of the respiratory tract, and which  communicates through the
Eustachian tubes with the middle ear.  The nostrils,  as parts of the
countenance, and placed as  safeguards at the commencement of the
air-passages, are more elaborately organized than the posterior nares,
which indeed are simple  communications, without anything remark-
able in their construction, except the shelving of the floor of the nose
into the upper surface of the soft palate, favouring the gravitation  of
mucus from the nose into the  pharynx.   The  nostrils have a carti-
laginous  framework, which  keeps them  open, unless forcibly com- 
392
INNERVATION.
Fisr. 102.
 Front view of the cartilages
of the nose.  Above is seen the
outline of the nasal bones —a.
Front edge of the septal car-
tilage. 6, b. Lateral cartilages.
c, c. Alar cartilages, with their
appendages.—After Soemmer-
ing.
pressed.   This framework consists of five principal pieces: one in the
middle, the septal cartilage, a, completing the septum in  front; and
                      two on each side, the lateral and  alar  carti-
                      lages, b, c, forming respectively the  side  of
                      the nose below the nasal bones, and the wing
                      of the nose.   The former of these  is triangu-
                      lar, and rests  against the  front edge  of the
                      septal cartilage; the latter is thinner and more
                      flexible, and  curved upon  itself to form the
                      dilatable chamber  just  within the  nostril.
                      Several  loose nodules or  flakes of cartilage
                      frequently exist in  connection  with  the alar
                      cartilages.  The nostrils are further supplied
                      with three pairs of muscles ; viz.,  that called
                      by Albinus  compressor naris,  but which is
                      rather a lateral dilator, the levator and depres-
                      sor ala nasi.  By these the  orifices  are dilated
                      when we sniff the air in  smelling, as well  as
                      under the influence of certain passions.   The
                      integuments of the nose are studded with the
                      orifices of sebaceous follicles, which are among
                      the largest in  the  body, and so numerous  as
                      to form  a thick continuous layer  under the
                      cutis;  and  immediately within  the nostrils is
                      a growth of strong hairs, ox vibrissa, designed
to obstruct the entrance of injurious substances.
   With regard to the interior of the  nose, its cavities are formed  of
bone, generally thin, compact, and laminated, everywhere  invested
with  periosteum.  This latter is lined with mucous membrane, the
Schneiderian or pituitary membrane,  continuous with the skin of the
face at the nostrils, with the mucous  covering of the eye through the
lachrymal  passages, and  with that of the  pharynx and middle ear
through the posterior nares.
   The  mucous membrane of  the nose varies in its  structure in dif-
ferent regions.  In many situations, especially in the sinuses, it is so
intimately connected with the periosteum that that fibrous membrane
is in  fact a submucous areolar tissue;  and the  entire lining of the
bone has  been sometimes called a fibro-mucous  membrane, which,
as a whole, is delicate in the  extreme.  On the septum and spongy
bones, bounding the direct passage  from the nostrils to  the  throat,
the lining membrane is much more thick, partly  in consequence of a
multitude of glands  being disseminated beneath it, and opening upon
it, but chiefly perhaps from the presence of ample and capacious sub-
mucous  plexuses of both arteries and veins, of  which the latter are
by far the more large  and tortuous.   These plexuses,  lying, as they
do, in a region exposed  more than any other to external cooling in-
fluences, appear to be designed  to promote the  warmth of the  part,
and to elevate the temperature of the air on its passage to the lungs.
They also serve to explain the tendency to  hemorrhage from the nose
in cases of general or local plethora. 
THE SCHNEIDERIAN MEMBRANE.
393
   Tn the vicinity of the nostrils  the mucous membrane  exhibits pa-
 pillae, and a scaly epithelium, like the corresponding parts of the skin.
 In the sinuses and  in all the lower region of the nose, the epithelium
 is of extreme delicacy, being of the columnar variety, and clothed
 with cilia.  This  being the first occasion on which we  have had to
 speak of this kind of epithelium,  we shall briefly describe its structure
 and mode of growth.
   The nucleated particles of which it consists  are found in a double
 series:  of which the first, resting on the subjacent basement tissue,
 is as yet imperfect; and the  second, rising  to  and forming  the free
 external surface of the  membrane, is  completely developed, and
 furnished with  cilia.  The deeper  series is the more  adherent, and
 if recent will be found to remain more  or  less attached,  when  the
 superficial and  perfect  layer has  been removed by a gentle stream of
 water.  It will  then have the appearance represented at b, fig. 103.
 The nuclei, which  are arranged  nearly on the same level, are ovoid,
 and  contain usually two nucleoli, even more pellucid than themselves.
 The surrounding substance is in  relatively small quantity, and is seen
 either as a mere film  around the nucleus, or vertically elongated in
various  degrees.   In  the  superficial series, a, the nuclei, though
lying on the same general  level, are placed some higher and some
lower, as  if for convenience of package, since the particles  bulge
where the nuclei are situated.  The nuclei  are  scarcely different  in

                              Fig. 103.
  View of the ciliated epithelium of the nose, seen in section :—a. Superficial series, clothed with
 cilia, b. Deeper series, becoming elongated vertically, c. Various shapes of the perfect ciliated
 particles.—Magnified ISO diameters.

 size or shape from those below.  The surrounding granular substance
 of  the particle is, however,  much  longer  than before; below, where
 it is implanted between the particles of the deep series, it is pointed,
 though sometimes blunt, and often club-shaped, while the upper  end
 enlarges, and terminates  by a flat  surface, from  which the cilia pro-
ject, c.   It must be observed, that  the cell-membrane, so apparent in
 the scaly epithelium heretofore described, is not to be found in  this
 variety.   It is  either early absorbed, or else so delicate and so united
 to the contained substance, as not  to be distinguishable as a separate
 object.
  It appears  clear that this double  series of particles constitutes two
stages of growth of the  same structure.   Instances are not wanting of
particles intermediate between the two, in which the future surface
of the  membrane  is  marked by a horizontal line, above which  the
granular substance exhibits  a vertically fibrous  structure, indicative
       26 
394
INNERVATION.
of the coming  cilia.   Moreover,  we  have  met  with examples in
which a  surface  perfectly ciliated  was still covered with a  layer of
other ciliated particles, that, from their half-dissolved  appearance,
had  evidently passed  their  prime, and  were  in .process  of decay.
This  progressive  development of  the  particles as they recede  from
the vascular  source of  their nutriment, and especially the evolution
at last of those delicate evidences of life, the ciliary appendages, is a
glaring example of the essential  independence of the  vitality of the
tissues on the blood-vessels, and makes it more easy to conceive the
really subordinate or ministerial office of those channels.
   We now come to the proper  seat of the  sense of smell, a com-
paratively limited district of the nasal organ, to which  we shall apply
the term olfactory region.   As this  olfactory region has  not  hitherto
been  distinguished, nor its character understood, we  shall describe
it  somewhat  minutely.   This, as  well  as  other  parts, can  be best
examined in  animals, because  they can be procured  fresh, and in a
state of health.   The  mucous membrane so soon loses many of its
most  interesting  features, especially where  death has followed  on
chronic disease,  that the  human subject is not the most favourable
for the investigation  of its physiological anatomy, and  can  only be
advantageously  inspected after  the lower  animals have furnished
the general  clue.   This remark is well illustrated   by the present
instance.
   The olfactory region  is situated at the top of the nose, immediately
                               below  the cribriform plate of  the
                               ethmoid  bone,  through  which  the
                               olfactory nerves reach the membrane;
                               and  it  extends about one-third, or
                               one-fourth, downwards on  the sep-
                               tum, and .over the superior and part
                               of the   middle  spongy bones of the
                               ethmoid.   Its limits  are  distinctly
                               marked by a more or less rich sienna-
                               brown  tint of the  epithelium, and by
                               a remarkable increase in the thickness
                               of this structure,  compared with the
                               ciliated region  below ; so much so,
                               that it  forms an opaque soft pulp upon
                               the  surface of  the membrane, very
                               different  from  the   delicate,   very
                               transparent  film of the  sinuses  and
                               lower spongy bones.  The epithelium
                               indeed here quite  alters its character,
                               being  no longer  ciliated, but com-
                               posed  of an  aggregation  of super-
                               posed  nucleated  particles, of  pretty
uniform  appearance throughout; except that, in many instances, a
layer of  those lying deepest, or almost deepest, is of a darker colour
than the rest, from the brown  pigment contained in the cells (fig.
104, b).   These epithelial particles, then, are not ciliated; and they
Fig. 104.
 Vertical section of the olfactory region of
the nose of the rabbit:—a. Surface of the
epithelium, b. Layer coloured by pigment.
c. Line of basement membrane,  d. Nu-
cleated tissue seen below,  e. Olfactory
nervous  filament branching. — Magn. 250
diam. 
THE OLFACTORY REGION.
395
form a thick, soft, and pulpy stratum, resting on the basement mem-
brane.  The deepest layer often adheres after the others  are washed
away.   On  looking  on the under surface of this epithelium, when it
has been detached, we observe projecting tubular  fragments, similar
to the cuticular lining drawn out of the sweat-ducts of the skin, when
the cuticle is  removed  after  maceration (figs. 79 and 80).   In fact,
glands apparently identical with the sweat-glands exist in this region
in great numbers.  They dip down in the recesses of the submucous
tissue, among the ramifications of the  olfactory nerves;  and  their
orifices are very easily seen, after the  general brown coat of epithe-
lium  has been  detached,  lying jnore  or less  in  vertical  rows, the
arrangement of which is probably  determined by the course of those
nerves beneath.  They become more and more sparing towards the
limits of the olfactory region.   The epithelium of these  glands  is
bulky, and like t^iat  of the sweat-glands, contains some pigment.   As
the duct approaches the  epithelium of the general surface, its wall
becomes thinner and more transparent;  and, in its  subsequent course
upwards, it is difficult to be traced, for it does not appear  to be spiral,
or its particles to differ from those which  they traverse.   We  have
sometimes seen rods of epithelium, apparently hollow, left projecting
from the basement membrane,  after the  brown  epithelium has been
washed away; and these are perhaps portions of the excretory ducts
of these glands.
   A good injection of the  nasal organ in the foetus, both  of man and
animals, will display a multitude of minute capillary loops  upon the
surface of the olfactory region, bearing  a close  resemblance to those
of rudimentary papillae.   These loops were first  pointed out  to us two
years ago by Mr. Quekett  in the foetal  pig, and also in  the human
foetus at its full term;  and so  clearly did they seem to indicate the
presence of true papillae in this region, that we
made repeated and close  examinations  of the
recent organ, in order to expose their structure,
supposing  them to be concerned in the  sense
of smell.   These researches, pursued on adult
specimens,  have  been hitherto  fruitless;  at
least, we have  found  no other evidence  of
papillae than  delicate hollow  epithelial pro-
cesses  remaining, after  a gentle current  of
       ,  ,     , °,       ,i     •  •  i     .•      Dilated loopings of the ca-
water  had  washed away the principal portion   piiiaries of the olfactory re-
of  the  brown  epithelial  investment—an ap-   fced^d S^ll™™ <
pearance too ambiguous to be spoken of with
confidence.   In the human foetuses we have injected, the  loops are
such as are represented above (fig. 105).   The convexity  of the loops
presents a decided  dilatation,  being from  20V0 to tiVo  °f an  inch
wide,  while the  diameter of  the  capillary on either  side  is only
about 30V5- inch.   We have hitherto failed in seeing any  loop-like or
projecting capillaries in  injections of adult specimens.   Care must be
taken not to confound these loops in the olfactory region of the foetus
with the loops of the undoubted true papillae, situated just within the
nostrils, and which belong to touch.
 
396
INNERVATION.
   Of the JVerves of the Nose.—These are the first pair, and branches
 of the fifth pair, besides motor filaments from the facial  nerve to the
 external muscles.  The  first pair has long  been  considered as the
 proper nerve of smell, though not without dispute.   That it has been
 rightly so regarded, however, is evident for many reasons.  Its limi-
 tation to the upper  and middle spongy bones, to the roof of the nasal
 fossae, and to the  upper half of the septum, where the mucous mem-
 brane exhibits  peculiar characters, and smell is  principally, if not
 exclusively, exercised ; its development in the  vertebrate class, pro-
 portionate, cateris paribus,  to the acuteness of smell, being largest in
 animals of  keenest scent; the  loss# of  smell,  without  other effect,
 consequent on its division; together with  the  perversion or  loss of
 smell found  in many authentic  cases in connection with disease of
 these nerves or their associated cerebral  region: all  these facts point
 irresistibly to this conclusion.
   Of the  First Pair.—Under this head  are  to  be  described  the
 olfactory process  or lobe,  and  the olfactory filaments distributed to
the nose.
   The olfactory process,  or lobe (a,  b, fig. 106), is  a slender  prism

                                Fig. 106.
 Outer wall of the nasal fossa, with the three spongy bones and meatus: the nerves being shown
as they would appear through the membrane if it were transparent—a. Olfactory process  6. Ol-
factory bulb (represented rather too short) resting on the cribriform plate.  Below is seen the plexi-
form arrangement of the olfactory filaments on the upper and middle spongy bones,  c. Ffth nerve
within the cranium with its Gasserian ganglion,  d. Its superior maxillary division, sending
branches to Meckel's ganglion, and through that to the three spongy bones, where they anastomose
with the olfactory filaments, and with s, branches of the nasal division of  the ophthalmic nerve.
o. Posterior palatine twigs from Meckel's ganglion, supplying the soft and hard palate,  t  Orifice
of the Eustachian tube on the side of the pharynx, behind the lower spongy bone.—From Soemmer-
ing, two-thirds diameter.


of fibrous and vesicular nervous  matter,  terminating  in front  in a
bulb;  and it is sunk  in  the fissure which  bounds  the supra-orbitar
convolutions on the under surface of the anterior lobe  of the cerebrum
(p. 255).  It is connected with  the inferior surface of the brain  by
an external  and internal root.   The  former is  the  longer, and  may 
THE OLFACTORY NERVE.
397
be traced in the nervous matter forming the floor of the fissure  of
Sylvius,  and among the arteries of the locus perforatus, towards the
lower and outer part of the corpus  striatum, near the anterior com-
missure of the cerebrum.  In the dog and cat, where this process is
much larger, the anterior commissure seems to have a more intimate
relation to the olfactory processes.   In the same animals the white
matter of the  process  is  continuous also with that of  the  largely
developed hippocampus major.  The  internal  root winds inwards,
and is lost in the gray matter in front of the optic  commissure, near
the anterior extremity of the corpus  callosum.   In front of the point
where the roots  join, there is a process of gray  matter constituting a
third  or  gray root, and  which is continued forwards as a portion  of
the olfactory process, as  far as the bulb, where it expands.
   The bulb of the olfactory process  (fig. 106, b) is an elongated oval
mass  of  nervous matter, which lies  upon the cribriform plate. The
white  portions of  the olfactory process terminate in its posterior ex-
tremity.   It contains a small ventricle, which, in some of the lower
animals,  is prolonged backwards as for as the cerebral  ventricles.
This ventricle is lined with a delicate white layer, but with this ex-
ception,  the whole olfactory lobe consists of gray matter. In particular
it is to be observed, that the under portion, which  reposes  on the
cribriform plate, and  sends down the olfactory filaments, contains no
tubular fibres.
   The olfactory filaments (figs. 106, 7, 8) are from fifteen to twenty-
five in number, and, passing through the apertures of the cribriform
plate, may be seen, invested with fibrous sheaths  derived from the
dura  mater, upon the deep or attached surface of the mucous mem-
brane of the olfactory region.   They here  branch, and sparingly re-
unite  in  a plexiform  manner, as they descend.  They form  a con-
siderable  part  of  the entire thickness of the membrane, and differ
widely from the  ordinary cerebral nerves in structure.  They contain
no white substance of Schwann, are
not divisible into elementary fibrillae,
are nucleated, and  finely granular in
texture,  and are  invested  with a
sheath of homogeneous membrane,
much  resembling  the sarcolemma,
or, more  strictly,  that neurilemma
which we figured from the nerves of
insects in fig. 64, p. 209. These facts
we have  repeatedly ascertained, and
they appear to be of great importance
to the general question of the  func-
tion of the several ultimate elements
of the nervous structure, especially
when   viewed  in  connection with
what  will be said on the  anatomy
of the retina.  We are aware that
some  anatomists deny the existence
of the white substance of Schwann as a natural element of the  nerve
Tig. 107.
 Olfactory filaments of the Dog: — a- In
water, b. In acetic acid.—Magnified 230 dia-
meters. 
398
INNERVATION.
fibre in any case, pretending that  it is formed by artificial modes of
preparation ; we hold it to be a true structure ; but, however that may
be, these  nerves never  exhibit  it, however prepared.   They rather
correspond with the  gelatinous  fibres.   Now there is no kind  of
doubt that they are a direct continuation  from the vesicular matter
of the  olfactory bulb.   The arrangement of the  capillaries in  well-
injected  specimens is a convincing proof  of this, as these  vessels
gradually become elongated on the nerve assuming a fibrous character
as it quits the surface of the bulb; and further, no tubular fibres can
ever be discovered in the pulp often left upon the orifices of the crib-
riform plate  after detachment of the bulb.  It must be  remembered,
that a few tubular fibres from the nasal nerve of the fifth here and
there accompany the true olfactory filaments, but these  only serve to
make the difference more evident by contrast.
   Although these nucleated olfactory filaments lie in great abundance
under the mucous membrane of the olfactory region, we have  been
quite foiled in our attempts  to trace their  ultimate distribution in the
membrane, and the difficulty is attributable to their want of the cha-
racteristic white substance.   Their elongated nuclei render the larger
branches  unmistakeable; but if these  become  resolved at last into
fibrous  elements, the nuclei cease to be distinct from  those of the
numerous nucleated tissues  which  they traverse.   In this respect they
correspond, in all probability, with the nerves of some of the papillae
of the  tongue  (see pp. 379-380); and,  considering the similarity
between the two senses, an argument may be hence deduced for the
limitation of the sense of taste to those elementary nerve-fibres  going
to the tongue which are without the white substance of Schwann.   If
this be so, the looped tubular fibres are confined to the impressions of
touch in that  organ.
   We are averse from  speculating prematurely on the rrfeaning  of
anatomical facts, but as some hypothesis will intrude itself, we would
venture to hint that this amalgamation of the elements of the peripheral
part of the  olfactory nervous apparatus in the larger branches, and
probably  in the  most remote distribution, as well as the nucleated
character indicative of an essential continuity of tissue with the vesi-
cular matter of the lobe, are in accordance with the oneness of the
sensation resulting from simultaneous impressions on different parts
of this organ of sense, and seem to show that it would be most correct
to speak of the first pair of  nerves, as a portion of the nervous centre
put forward beyond the cranium,  in order that it may there receive,
as at first hand, the impressions of which the mind is to become cog-
nizant.   No true tubular fibres belong to the olfactory nervous appa-
ratus,  except  those commissural ones  passing between the bulb and
certain portions of the cerebrum.
   The branches of the fifth  pair given to the nose (figs.  106 and 108),
 are derived from  its ophthalmic and superior  maxillary divisions.
 The nasal twig of the former, crossing the orbit, passes  over the crib-
 riform plate of the ethmoid bone into  the  nose, in close contact with
 a portion of the olfactory nerve, and most probably forms some anas-
 tomoses with it.  Its subsequent  course  is downwards, subdividing 
CONDITIONS OF SMELL.
399
to supply the mucous membrane and skin in the neighbourhood of the
anterior orifices.   The pungent sensation preceding sneezing seems
to be an  affection of this twig,
and  the flow of tears that accom-
panies that act is accounted  for
by the^ common  source  of  this
and  of the lachrymal nerve. The
nasal branches of Meckel's gan-
glion enter the nose  through the
spheno-palatine  foramen,  or  by
pores between this and  the pos-
terior  palatine  canal,  and  then
spread over the three turbinated
bones and the septum nasi, anas-
tomosing at several  points with
the  olfactory  filaments, and with
the nasal branch  of the ophthal-
mic  (figs. 106 and 108).   When
the fifth nerve is  diseased, so that
sensation is lost  generally in the
parts supplied by it,  a brush may
be introduced into the nostril, and
rubbed over the  surfaces  usually
so  extremely sensitive,  without
the  slightest  discomfort  to  the
patient.   Similar effects follow division of the nerve.   Hence it may
be concluded that the fifth  gives common sensibility to the nose, in
common with most of the  other parts which it supplies.
   Conditions  of smell.—In addition to  the essential  conditions of
integrity of the nervous apparatus, and the presence of the requisite
stimulus, a healthy condition of the epithelial investment of the papillae
seems necessary for perfect smell.   If the mucous surface is dry, or
if it is  in the raw irritable  state, attended with wTatery discharge,
induced  by cold, smell  is  impaired or lost.   This is  explained by
considering the  manner in which  the  nerves  are ordinarily brought
under the  influence of  the stimulus.   As in taste, a solution of the
stimulus in the surface of the membrane is requisite in  order that the
odorous  substance may actually reach  the  nerve.   Insoluble  sub-
stances cannot be smelt.   Hence, whether the  membrane be too dry,
or an inordinate  excretion of  fluid be  going on from its surface, the
necessary penetration of the stimulus to the nerves is alike  interfered
with.  In  the latter  case, the effect  may partly depend  also  on  a
change produced by the inflammatory action, in the excitability of the
nerves themselves.
   Since  odorous  substances must undergo solution before they can
affect the olfactory nerves, why, it may be asked, cannot such  sub-
stances, if dissolved  in water and  injected into the nose, be recog-
nized by their smell ?   In answer to this it may be stated, that there
is no reason to deny the  possibility of their  being so recognized, as
far as the excitability of the  nerves is concerned.   But the ciliated
Fig. 108.
 Nerves of the septum of the Nose:—a. Olfac-
tory bulb resting on the cribriform plate, below
which its branches may be traced on the septum
about halfway down.  Behind, the naso-palatine
nerve from Meck.el's ganglion is seen descending
to the naso-palatine canal.  In front, the nasal
twig of the ophthalmic nerve descends  towards
the tip of the nose, dividing into two principal
branches,  p. Roof of the mouth,  e. Orifice of the
Eustachian tube.—From Arnold, one-half diam. 
400
INNERVATION.
epithelium of the nose, and the nerves of common sensation supply-
ing the lining membrane, instantly resent the contact of all other fluids
than the film which moistens the surface, and which is naturally fur-
nished  by it in  due proportion to the exigencies of the part; and
when the  membrane  is thus irritated, and its texture altered by the
water, it need not excite surprise that its special sensibility should be
altered or disguised.  The organ of smell in fishes resembles'that of
air-breathing animals in every essential point of structure, and differs
mainly in  the  habitual contact of its  sentient surface with the sur-
rounding water.  It may therefore be  concluded, that  sensations of
smell are excited in it by substances brought to it through the water,
corresponding in kind with  those  brought in the other case  through
the air,  but eventually dissolved in the  moisture of the  membrane.
The nature of  the sensation will depend on the special sensibility
of the nerve, which in both cases can be excited only by the stimu-
lating substance in  solution ;  and whether air  or water brings the
stimulus to the surface of the membrane, is made important  only by
the special adaptation of that surface to the contact of one or the other
medium.
   We may here notice two  important reasons for the situation of the
organ of smell, so high up in the nose, in addition to the obvious one
of the protection from mechanical injury thus afforded to so  delicate
a part.  These are, that it is thereby screened from the contact of air
either too  cold  or  too  dry.  The interposition  between the outer
orifice and the organ of smell of projecting and folded membranes of
active secreting powers,  and containing large reservoirs of blood (in
the plexuses already described), seems designed to answer both these
purposes.   These  parts break the force of the current, warm it, and
impart that  degree  of moisture which is best calculated to  aid the
solution of the odoriferous particles on the sentient surface to which
they are  afterwards  applied.   The remarkable  complexity of the
lower turbinated bones  in  animals with acute  scent, without any
ascertained distribution of the olfactory nerves upon them, has given
countenance to the supposition that the fifth nerve may possess some
olfactory endowment, and seems not to have been explained by those
who rejected that idea.   If  considered as accessory to the perfection
of the sense in the way above  alluded to, this striking arrangement
will be found consistent with  the view which  limits the power of
smell to the first pair of nerves.
   We have already remarked that the  exercise of the sense of smell
is not attended with  more than a general idea of locality.  The sen-
sation is even more simple in this respect than that of  taste.   Unless
the experiment be made, we  know not that we are constantly exerting
the sense  on two sides, for  the double sensation is perceived as a
single one.  Our observations on the anatomy of the olfactory nervous
apparatus  may assist in the explanation of this fact.
   The  sense  of smell maybe voluntarily heightened by short and
quick inspirations, which drive the air smartly against the upper region
of the nose, and thus lead to the more effectual detention of its odori-
ferous particles by the membrane, while  the  attention is given to its 
OF VISION.
401
sensations.   On the other hand, by closing the nostrils, and breathing
through the  mouth, all  access to the  organ of smell is  prevented,
except that  gradually effected by  admixture through the pharynx
and  posterior nares.  It  is  through this latter  channel  that  the
odorous  particles of food, rising  from the throat to the nose  during
expiration, blend the sensation of smell  with  that of taste  so strongly
and  habitually, that it  becomes difficult  to discriminate between
them.
  Analogy would lead to  the belief that the nervous apparatus of
smell, if irritated by an internal cause, would be the seat of olfactory
sensations.   Such subjective phenomena have  been  known to exist
in certain cases of  disease, in which the nerve, or the anterior lobe
of the brain, has been afterwards  found  disorganized.   Occasionally,
too,  odours  are  perceived without the actual presence of the object
usually giving rise to them.   These also must be regarded as  sub-
jective.
  The quality of the sense, also, seems to vary not a little  in different
persons ;  some being strongly affected,  even to  faintness,  by a scent
which is almost imperceptible to others.   The odours of flowers, for
example, are very variously appreciated, as every one must have more
or less observed.  There are corresponding idiosyncrasies in the other
senses.

  On the subjects of this chapter, in addition to the elementary works before quoted,
the following  may be consulted:—Schneiderius, de osse  cribriformi  et sensu ac
organo odoratus; Scarpa, de organo olfactus; also, de auditu et olfactu ; Soemmering,
Icones organi humani olfactus, 1809; H. Cloquet, Osphresiologie, ou traitedesodeurs.
Paris, 1821.
                        CHAPTER XVII.

OF  VISION.--OF  THE ANATOMY OF  THE EYEBALL, OPTIC NERVES, AND
           APPENDAGES.--OF THE  PHENOMENA OF VISION.

  It would appear  that an animal may be sensible to light without
possessing an organ of vision.  Thus, that beautiful little polyp, the
hydra, shows a decided predilection for the light side of the vessel
in which it is kept.   Most animals, too, require the presence of light
for  the full performance of their functions; and this is not the  case
with animals alone,  but with plants likewise: both, in the  great ma-
jority of instances, pine away in the dark, or fail to arrive at  complete
development.
  But the  presence of an organ of vision implies something more than
the  mere power of  distinguishing between light and darkness.  It
must enable the animal to  discern something of the colour,  or at least
of the form, of surrounding objects ; and this in a degree proportioned
to the perfection and complexity of its  organization. 
402
INNERVATION.
  The principle on which the organ is constructed seems to be  in
all cases the same, viz., that of the camera obscura—a dark chamber
with a small aperture for the admission of light, a  quantity of black
matter for the absorption of superabundant rays, and a nervous expan-
sion on that wall which receives the rays of light.
  Among the lower invertebrata, the eyes, or ocelli, consist only of a
nervous  point,  shielded with a minute quantity of  colouring matter.
The chief additions which increase the complexity of these organs in
the higher  animals  consist of transparent  media and lenses for  the
refraction of the light, and the production of a more precise image ; of
an apparatus for the regulation of the quantity of light admitted to the
retina; and of other appendages for protection and movement.
  The position of the human eye at the upper part of the face and
directed forwards, while it gives to the* countenance its most important
element of beauty, adds greatly to the utility of the organ, by increas-
ing the visual range.   For protection in this  exposed situation, it is
sunk deeply in  a cushion of fat, within a  bony cavity, the orbit,  the
prominent  borders of which are well adapted to  receive the force of
blows  directed  towards that region.  It is furnished with muscles
capable of moving it towards any side, and of protruding or sinking
it.   It is likewise provided with  movable  lids to  guard its exposed
surface from mechanical injury, and its nerve from the effects of  ex-
cessive light; and with a lachrymal apparatus, by which the front of
it is continually irrigated with a bland fluid.
   In the globe of the eye itself we recognize, as the most essential
constituents, the expansion of the optic nerve, called the retina; and,
in front of this, the transparent refracting media which, as a whole,
transmit the light so as to bring its rays to a focus  upon the nervous
sheet.   The curved form of the retina, and the rounded figure of the
eye  thence derived, are perfectly adapted  to the curvatures  of  the
refracting  media: so that, if the nervous  lamina  had assumed any
other shape, it would have been more or less out of focus, and vision
consequently have been indistinct.
   To  maintain  the figure of the  retina, and to protect a part of so
much delicacy, in which the slightest change of form would be attended
with injury to the function, the whole is encased in a dense tunic of
great strength,  termed the sclerotica (s^x^o?, durus), which is opaque,
except in front, where it is modified in structure, becomes perfectly
transparent to allow the light to  enter, and is  known as the cornea.
Between the sclerotica  and the  retina is interposed a layer of dark
pigment, contained in a delicate  membrane termed the choroid.   In
front of the  retina are the  transparent media.   One of  these  (the
vitreous  body or humor)  is contained  immediately  within the cup
which the  retina forms, and  appears specially constructed to give it
that necessary  support  inside whfch the  sclerotica furnishes on  the
outside.  The  vitreous body occupies four-fifths of the whole globe.
Imbedded  in its anterior part is a double convex lens (the  crystalline
lens or body), which comes nearly up to the cornea;  leaving, however,
a small cavity containing  a watery fluid, the aqueous humor, between
itself  and  that  transparent part of  the external case.  Across this 
THE EYE.
403
cavity, and dividing it into  an anterior and posterior chamber, hangs
a vertical curtain-like process of the choroid, called the iris, perforated
in the centre by an aperture, the pupil, for the admission of light to
the interior, and contractile  under the influence of light on the  retina,
in order that it may regulate the amount of light entering the  organ.
The perfect fluidity of the aqueous  humor is a provision to allow of
the expansion and contraction of the pupil, and of the  movements of
the lens itself towards or from the cornea.
   The human eye would  be nearly globular were  it not that the
anterior portion, formed by the cornea, is a part  of a  smaller  sphere
than  the  rest, and is therefore slightly protuberant.   Hence the an-
teroposterior axis  of the  eye is longer than the transverse, in the
proportion of twenty to nineteen.

  In terrestrial quadrupeds its shape is for the most part nearly similar. In animals
that inhabit the water, as Cetacea and fishes, the  eye is considerably flattened  in
front; so that, in some fishes, it is almost a half-sphere.  In birds, on the contrary,
especially those which fly high, the cornea is very prominent compared with the rest
of the eye, which is of a  more or less flattened form.  These differences  have an
evident reference to the density or rareness of the medium  through which the light
passes to the organ.

   A more  detailed description of the  several  structures composing
the ball of the eye will now be given,  in  which  we shall follow the
order most natural to a dissector, viz., that from without,  inwards.
   The sclerotic coat consists of white  fibrous tissue,  in which,  how-
ever, the ultimate filaments are more distinct, and  less wavy  than in
ordinary specimens.  These form  numerous  layers, crossing one an-
other chiefly at right angles, and thus constitute a membrane capable
of resisting  distension, and of retaining  its figure under pressure.
It has a white glistening aspect, especially in front, where it receives
the insertion of the tendons of the four straight  muscles, and, being
visible,  is  familiarly  known as  the  " white  of the eye."   The
 sclerotic is thickest behind, and becomes gradually thinner in front,
till nearly in contact with the cornea, where it increases in strength  a
little.

   In the animal series, the sclerotic becomes of greater relative thickness behind, in
proportion to the flattening of the organ in front, and the pressure which it will have
to sustain from the  surrounding medium.  In aquatic mammalia this is effected
simply by an accumulation of the fibrous tissue in that situation, as in the  whale,
where it is often an inch in thickness, a wonderful  provision against the enormous
pressure to which that animal is exposed at great depths. In  reptiles and fishes
there  is a thick cartilaginous lamina included in the fibrous tissue; and in some this
cartilage ossifies, as in the sea-bream, mentioned by Dr. Jacob.  In birds, too, where
the sclerotica is flattened from before backwards, a thin cartilaginous plate  exists in
it, which confers a peculiar elasticity and firmness,  and is at the same time  light and
 slender.  Its anterior  part is further fortified by fourteen or fifteen osseous  plates,
 disposed in a regular  series round the margin  of the cornea. Similar plates occur
 in various reptiles, and are especially remarkable in those gigantic specimens of this
 class, the  Ichthyosauri and Plesiosauri, which  are only known to us  by their fossil
 remains.

   The optic nerve comes  through the sclerotic behind, at a distance
 of about its  own breadth,  or nearly one-eighth of an inch,  on the
 inner side  of the axis of the eye, by which is meant the  axis of the 
404
INNERVATION.
dioptric media.  This nerve contains a considerable quantity of fibrous
tissue separating and supporting  its  fasciculi, and as it traverses the
sclerotic this tissue becomes continuous with the borders of the aper-
ture, so that the aperture itself may be said to be cribriform; the nerve
passing through a number of distinct canals of fibrous tissue, before
it reaches the inner surface of the  sclerotic.   It is indifferent whether
this cribriform tissue be  called neurilemma or sclerotic.   One thing,
however, may be always observed.   The  nerve, as  it pierces  the
sclerotic, contracts, and  lies in a smaller  compass, so that the entire
aperture is somewhat funnel-shaped,  and  wider behind than in front;
and, though  the nerve  is movable on  its entrance  into the  sclerotic
aperture, it is always fixed firmly at the  inner surface of that aperture,
where the retina commences.
  The  aperture in the  sclerotic in front, for  the  cornea, is circular,
and usually about r7gths of an inch in transverse diameter, and rather
less  vertically, though in some  individuals  altogether  smaller.   Be-
tween the point of entrance of  the optic  nerve, and the attachments
of the recti muscles, there are several minute apertures for the trans-
mission of vessels and nerves to the  interior.   The  nutrition of this
tunic itself is provided for by small vessels  ramifying  on its surface,
and sparingly continued into its substance.  Its own proper vascularity
does not seem to be greater than that of other fibrous structures.
   Of the Cornea.—The  size and shape of this transparent part of the
outer case of the  eye have  been already indicated.   It is spherical
rather than spheroidal, and its posterior  surface is of parallel curvature
with the anterior; so that it does not appear to be a meniscus  lens,
thicker in the middle, as some authors  have described : this  at least
is the result of our careful examination.  The cornea, when its con-
cavity is filled up with  the  aqueous  humor, is of course  a powerful
converger of the rays of  light towards the iris, and through the pupil
to the  lens.    Viewed from within, its  circumference is  exactly cir-
cular; but on the outside  it generally appears wider transversely, from
the sclerotic, which overlaps it on all sides, encroaching upon it rather
more  above  and  below.  The  cornea and  sclerotic are firmly con-
nected  by continuity of  texture, and cannot  be  disunited  even by
maceration.    The cornea is possessed of great toughness, and will
even resist a force capable of rupturing the sclerotic.
  The  cornea, though a beautifully  transparent substance, and ap-
pearing at first sight as homogeneous as glass, is nevertheless full of
elaborate structure.  It is, in fact, composed of five coats or layers,
clearly distinguishable from  one  another.  These  are, from before
backwards, the  conjunctival  layer of epithelium,  the anterior elastic
lamina, the cornea proper, the posterior elastic lamina, and the epithe-
lium of the aqueous humor, or posterior epithelium.   The cornea, when
uninflamed, contains no blood-vessels; those  of the surrounding parts
running back  in loops, as they arrive at its border.
  On  the  cornea proper, or lamellated  cornea,  the thickness  and
strength of the cornea mainly depend.    It is a peculiar modification
of the white fibrous tissue, continuous with that of the  sclerotic.   At
their line of junction (fig. 109), the fibres, which in the  sclerotic have 
OF THE CORNEA.
405
been  densely interlaced  in various  directions, and mingled  with
elastic fibrous tissue, flatten  out into a  membranous form, so as to

                               Fig. 109.
 Vertical section of the Sclerotic and Cornea, showing the conlinuily of their tissue between the
doited lines:—a. Cornea, b. Sclerotic.  In the cornea the tubular spaces are seen cut through,
and in the sclerotic the irregular areolae.  Cell-nuclei, as at e. are seen scattered throughout, ren-
dered more plain by acetic acid.  Magnified 32U diameters.

follow in the main the curvatures of the surfaces of the cornea, and
to constitute a series of more than sixty lamellae, intimately united to
one another by  very numerous processes of  similar structure, passing
from  one to  the other,  and making it impossible to trace any one
lamella  over even  a  small portion of the  cornea.  The resulting
areolae, which in  the sclerotic are irregular, and on all sides open, are
converted in the cornea  into tubular spaces, which have a very sin-
gular arrangement, hitherto undescribed.   They lie  in superposed
planes, the contiguous  ones of the same plane being for the most part
parallel, but  crossing  those of the  neighbouring planes at an angle,
and seldom communicating with  them (fig. 110).   The  arrangement

                               Fig. no.
  Tubes of the Cornea Proper, as shown in the eye of the Ox by mercurial injection. Slightly
magnified.

and  size of these tubes can be shown by driving mercury, or coloured
size, or air, into a  small  puncture  made in the cornea.   They may
also be shown under a high  power by moistening  a thin section  of a
dried cornea, and opening it out by needles.   The tissue  forming the
parietes of these tubes is membranous rather than fibrous, though  with
the best glasses  a fibrous striation maybe frequently seen, both in the
laminae separating the different series of tubes, and in that dividing
those of the same layer from each other.   By acetic acid, also, the 
406
INNERVATION.
structure swells, and displays corpuscles resembling those  apparent
in the  white fibrous tissue.   Such  is the lamellar structure of the
cornea, which makes it so much easier to thrust an instrument hori-
zontally than  vertically into its substance.   The  tubes  or elongated
spaces of which we have  spoken, are not distended with  any fluid,
but are merely moistened  in the same way as the  areolae of ordinary
areolar tissue.   A perfectly fresh and  transparent cornea is rendered
opaque by pressure, but it regains its brilliance on the removal of the
compressing force.  Some have supposed this to result from the ex-
pulsion of fluid  from between its laminae ; but that the opacity is owing
simply to a derangement of the elementary  parts  of its structure is
                          plain from the fact, that the  same pheno-
        Fig. UK           mena are exhibited  by  a section, however
                          thin, immersed in water, and deranged by
                          stretching.
                             Of the anterior elastic lamina.—This is
                          a  transparent, homogeneous  lamina,  co-
                          extensive with the front of the cornea, and
                          forming the anterior  boundary of the cornea
                          proper.  It is a peculiar tissue, the office
                          of which seems to be that of maintaining
                          the  exact  curvature of the  front of the
                          cornea;  for there  pass from all parts of its
                          posterior surface, and in particular from its
                          edge,  into  the  substance  of the  cornea
                          proper  and sclerotic, a multitude of fila-
                          mentous cords, which take hold, in a very
                          beautiful artificial  manner, of  the fibres and
                          membranes of those parts, and serve to
                          brace them and hold  them  in their right
                          configuration  (fig. Ill, b).    These cords,
                          like the elastic lamina of which  they are
                          productions, appear to  be  allied to the
                          yellow element of the areolar  tissue.  They
                          are unaffected by  the acids.   The anterior
                          elastic  lamina  sustains  the  conjunctival
                          epithelium  which covers the cornea, and
                          is very probably the representative of the
                          basement membrane of the mucous system,
                          as it  occupies the corresponding position
                          in regard to the epithelium.   Its thickness
                          is about 20V0  of an  inch.
                             The conjunctival epithelium of the cornea
                          may always be  obtained from  a fresh eye,
                          by gently scraping its surface.   It consists
                          of  three or four  layers of superposed par-
                          ticles,  inclining  to  the columnar form,
                          where  they rest  on the  anterior elastic
                          lamina,  and becoming imbricated  scales
                          on the  surface (fig. Ill, a).   In  many of
 a. Vertical section of the Human
Cornea, a. Conjunctival epithelium.
b. Anterior elastic lamina, from
which there pass off a number of
fibres into c, the layers of the cor-
nea proper, among which the nu-
clei are apparent.  d. Posterior
clastic lamina  e. Posterior epithe-
lium.—Magnified 80 diameters.
 b. The posterior epithelium, 0,
seen in section; p, seen in face.—
Magnified 300 diameters. 
CHOROID COAT OF THE EYE.
407
the larger animals this epithelium consists of a much deeper series of
nucleated particles, and its transparency then becomes a remarkable
character.
   It is in this epithelium that particles  driven with force against the
eye generally lodge, and it is easily detached by the instrument used
to extract them.  Vessels shooting into  the cornea in disease lie under
it, and small ulcers are formed by its destruction.  In animals which
cast their skin this lamina is shed with  the cuticle of the body.
   The posterior  elastic lamina of  the  cornea (fig. Ill, d) is a very
thin membrane in which no structure can be detected.   It has all the
transparency of glass, and  does  not become opaque by maceration,
boiling,  or the action of acids.  It adheres but slightly to the cornea
proper, and, when peeled off, it has such a tendency to  curl with  its
anterior  surface inwards, that it is difficult to  retain a piece of it in an
extended form.   If floated  in water, it  exhibits a peculiar glistening
lustre resulting from  its density.   It  readily tears, yet is so  hard that
it is bitten  through with difficulty.  Its  elasticity is great, and has
been supposed to contribute to the exact maintenance of the curvature
of the cornea, so necessary for correct  vision.   This lamina extends
only to the  circumference of the cornea, where it becomes  thinner;
and it ceases  at  the  border of the iris, in a  manner  hereafter to  be
described.
   Of the epithelium of the aqueous humor.—The elastic lamina is itself
lined by an exceedingly delicate epithelium,  which exactly resembles
that existing on serous membranes, (fig. Ill, e, o,p; see also p. 129.)
This epithelium is probably concerned in the secretion of the aqueous
humor, but it does not extend over the whole surface with which that
fluid is in contact.  It is probably limited to the  cornea.
   Of the Choroid.—On turning aside the sclerotic and cornea (fig.
112), the choroid, with its process the iris, is exposed.   The choroid
is of course perforated behind by the  optic nerve.   Around  this  it
adheres  pretty firmly to the  sclerotic, but in the rest of its extent very  i
slightly, and  only by  the medium  of a slender web (lamina fusca),
and of those vessels and nerves which  pass  from the one coat to the
other.   The rupture  of these adhesions occasions a flocculent ap-
pearance of the  choroid, and sets free  some  of the brown  colouring
matter with which its  structure is loaded.   There is no serous cavity
between the sclerotic and choroid, as some have imagined,  for a true
epithelium is wanting, though the lamina  fusca contains nuclei.
   The choroid, on coming  up to the cornea, gives off its process the
iris, and it there  adheres intimately to the sclerotic by a very narrow
ring of white  tissue—the ciliary ligament.   For an eighth of an inch
behind this, however, it is coated by a  semi-transparent band, which
we shall distinguish  as the ciliary muscle, and  the fibres  of which
radiate from the  cornea.
   The choroid contains some fibrous tissue, resembling that of the
sclerotic ; but it is composed principally of blood-vessels  and pigment-
cells.   It has been usual to describe it  as having two layers, an arte-
rial and  a venous; an  incorrect view.  It is in fact essentially a thin
lamina  of  capillaries, disposed in  a close  network, the meshes of 
408
INNERVATION.
which are  rather smaller  behind than in front.   This plexus forms
the inner surface of the choroid, and has been known as the tunica
Ruyschiana.   The arteries  supplying it, and the veins  carrying off its
blood, come to it and  leave it at  very numerous  points,  but on  its
outer surface only,  where  they are so thickly arranged, side by side,
as to appear to form the whole of that surface.   The  veins  in  par-
ticular are  large and  numerous, and  disposed in beautiful  curves,
converging to four or five  trunks, before  quitting  the choroid,  and
styled the vasa  vorticosa (fig. 112, e, e).   The arteries run between
these, but less regularly.
Fig. 112.
Fig. 113.
 Choroid and Iris, exposed by turning aside the sclero-
tica:—c,c. Ciliary nerves branching in the iris. d. Smaller
ciliary nerve, e. e. Vasa vorticosa. h. Ciliary  ligament
and muscle,  k. Converging fibres of the greater circle of
the iris.  I. Looped and knotted form of these  near the
pupil, with the converging fibres of the lesser circle of the
iris within them. o. The optic nerve.—From Zinn.
  Vessels of the choroid Ciliary
processes and Iris, inner surface.
— a.  Portion of the  capillary
network or tunica Ruyschiana.
b. Ciliary processes, c. Portion of
the iris.—From an Infant.  Mag-
nified 14 diam.  After Arnold.
   The capillary network of the inner surface is so close that there is
no room for  pigment-cells in its interstices;  but between it and the
arteries and veins, as well as among the veins  themselves, there is a
great abundance of colouring matter, which deeply tinges the whole
thickness of the membrane.
   The pigment-cells in the substance of the choroid  (fig. 114, b) are
extremely  irregular in  shape, and  lie in various directions amongst
the other elementary tissues.   Similar ones are found in the iris, and
sparingly in the anterior  part of the sclerotic.   They  are  so  loaded
with pigment that their nuclei are often obscured by.it.
   The pigmentary matter within  these cells is of a sepia colour, and
occurs in the  form of oblong or oval grains, less than To£oo of an inch 
THE CHOROIDAL  EPITHELIUM.
409
 a. Choroidal Epithelium, with the cells filled
with pigment, except at a, where the nuclei are
visible. The irregularity of the pigment-cells is
seen. 6. Grains of pigment.
 b. Pigment-cells from  the substance of the
Choroid. A detached nucleus is seen.—Magni-
fied 320 diameters.
long (fig. 114, b).   These grains exhibit molecular motion when re-
moved from the  cells, and  sometimes even within the cells  (p. 72).
They are insoluble in hot or cold
water, in the dilute mineral  acids,
and in strong acetic  acid, in oil,
alcohol, and  ether; but  are dis-
solved, after  long  digestion, by
diluted liquor potassae.  The ash
consists  of common  salt,   lime,
phosphate  of lime, and  oxide  of
iron (Gmelin and Berzelius).
   In albinos the colouring matter
is deficient, not  only in the  eyes,
but in other  organs  in  which  it
usually exists.   The  eyes  have
consequently  a  pink  appearance,
derived chiefly from the blood in
the choroid and  iris.
    Of the Choroidal Epithelium.—
On the  inner surface  of  the choroid, within  the capillary network,
and adhering slightly to  it, is  an  epithelium, consisting of  a single
layer of nucleated particles, of a pentagonal or  hexagonal  shape, filled
with pigment.  This was first particularly described by Mr. Wharton
Jones, who termed it the membrane of the black  pigment.  In using
this name, it  must be remembered  that  the colouring  matter  is not
peculiar to this  epithelium; and that this  epithelium exists  without
pigment in front of  the tapetum lucidum of animals; and also  that it
is present,  without pigment, in  albinos,  as was first  pointed  out  by
Mr. Jones.   Hence  the presence of pigment in its cells is  a secondary
character.   The nuclei of  the  cells  project on the inner surface of
the membrane.  They are  concealed by the  pigment if it  is very
abundant, but in general they are visible.   Both  conditions are seen
in fig. 114, a.

  In many quadrupeds and fishes  the  inner surface of  the  choroid, in its  posterior
part, has a brilliant lustre, owing  to the presence of a thick layer of wavy fibrous
tissue, peculiarly arranged, outside the choroidal epithelium (here colourless).  This
tapetum lucidum must act as a concave reflector, causing the rays of light to traverse
the retina a second time, and thus, probably, increasing the visual power, particularly
when the quantity of light admitted into the eye is small.
  In the osseous  fishes there is,a singular vascular organ of  a horse-shoe shape ap-
pended to the outer surface of the  choroid, and covered by a  silvery membrane.  Its
structure is imperfectly made out, and its  office is quite  unknown. It is called the
choroid gland.
  In birds there is a remarkable plicated, comb-like process of the choroid,  projected
into the vitreous humor, and termed the pecten.   It is a vascular membrane, and
covered with pigment; its base commencing at the entrance  of the optic nerve, and
its apex  reaching more or less nearly to the crystalline  lens.  The retina  does not
extend over it.  No satisfactory use has yet been assigned to it.  Its size and shape
ctre subject to considerable variety.

   The  description of the  choroid now given refers  only  to that por-
tion of it which corresponds to the  retina, and this  latter  membrane
ceases at a line  (ora serrata) about  an eighth of an  inch  behind  the
        27 
410 ■
INNERVATION.
margin of the cornea.  In front of this line, and as far as the iris, the
choroid is known as the  ciliary  body, being  modified  to  form the
ciliary processes;  and it is  covered  on its outer surface by a semi-
transparent tissue, the ciliary muscle, at the anterior edge of which is
a more opaque  white ring,  the ciliary ligament.
  The ciliary processes of the choroid project  as folds, or  plaitings,
into the vitreous humor, and are there  lodged in corresponding folds,
the ciliary processes of the vitreous body.   They are seen from within
to commence at the anterior border of the retina, or ora serrata, as
mere streaks, converging towards the  lens;  and it is only when ad-
vanced more than half way to that body that they become  projected
into about sixty or  seventy plaits, with  subordinate ones  between.
These terminate by  small free extremities, which slightly overlap in
front the border of the lens, without touching it, being united  to it
through the medium of a delicate  layer of the hyaloid membrane of
the vitreous humor.  These folds take firm hold of the vitreous humor
in its front part, all round  the lens.  Their  texture is very vascular
(fig. 113, b) and  filled  with irregular pigment-cells, (which in the
human eye are  least numerous on the most prominent parts,) and on
their inner surface is a tough colourless lamina, composed of ill-defined
nucleated cells, (continuous with the border of the retina, but clearly
not composed of nervous matter,) by means of which they are imme-
diately connected with the  hyaloid membrane.   The strength of this
connection is evinced in attempts to sever it in the recent eye.  After
a certain amount  of  decomposition has taken place, the separation is
much more easy.   The ciliary processes by their  anterior surface,
near their apex, contribute  to form the posterior wall and side of the
posterior  chamber, and are continuous  with the back of the iris.
They are there  free, and washed by the aqueous humor.   The ciliary
processes are covered, and  therefore concealed, on the outside by the
ciliary muscle.
  The iris may rightly be regarded as  a process of the choroid; it is
continuous  with  it, although  of a  modified structure.   It forms a
vertical curtain stretched in the aqueous humor before the  lens, and
perforated for  the transmission of light.  It is attached  all round at
the junction of the sclerotic and the cornea, so near, indeed, to the
latter that  its anterior  surface becomes  continuous in the following
manner with the posterior elastic lamina.   This lamina near its border
begins to send  off from its anterior surface, or that towards the lami-
nated cornea, a network of elastic fibres, which stretch towards the
border, becoming thicker as they  advance, until at length the entire
thickness of the lamina is expended by being  converted into them.
These fibres then  bend  backwards from the  whole circumference of
the cornea,  to the circumference of the front  of the iris, and are there
implanted, passing in this course across the rim of the anterior cham-
ber, and through  the aqueous humor.  They are seen more easily in
some animals than in others, forming a regular series of pillars around
the anterior chamber.   Behind  these  there is a more diffused union
of  the tissue of the iris with  the  sclerotic, by means of the ciliary
ligament.  The iris  is continuous  behind, near its border, with the 
STRUCTURE OF THE IRIS.
411
Fig. 115.
ciliary processes, and is only free in the inner half of its extent, near
the pupil, where it is  covered with a dense  layer of  pigment, and
marked by converging  striae.  This posterior surface  is termed uvea.
In consequence of  the  extreme  proximity of  the iris to the lens, the
posterior  chamber  is much less  capacious than the anterior, as it is
likewise of smaller diameter.
   The anterior surface  of the iris has a brilliant lustre, and is marked
by lines  accurately described by Dr. Jacob,
taking a more or less direct course towards the
pupil.  These lines are important as being in-
dicative of a  fibrous structure.   Slender, and
very numerous in the outer three-fourths of the
membrane (the pupil  being contracted), and
often crossed  near the border  by wave-like
differently coloured lines, they unite at  about
tV of an inch from the pupil into a circular
series of knotted and much thicker elevations,
from  which finally proceed a multitude of mi-
nute  branching and anastomosing filaments,
to the extreme verge of the pupil.  When the
pupil is contracted, these converging fibres are
stretched; when it is dilated, they are  thrown
more or less into zigzags.   The pupil is nearly
circular, and is situated rather to the inner side
of the centre of the iris.   By the movements
of the iris it is dilated  or  contracted, so as to
admit more or less  light to the  interior; and its
diameter  under  these circumstances  may vary
from  about 5V to ^ of an inch.
   The  varieties of colour in the eyes of dif-
ferent animals  and individuals depend almost
solely on the colour of the front of the iris,
which itself resides chiefly in pigment-cells,
situated  in its substance rather than as a  layer
on its anterior  surface.   These cells are most irregular in shape and
size,  and lie in the interstices of the more  essential  tissues, which
they much obscure.  The iris is consequently best examined in albino
specimens.
   The iris is undoubtedly  contractile, and the anatomical  characters
of its principal  tissue so nearly resemble those of unstriped muscle,
that it may be considered  as a variety of that tissue.   Its fibres are
loaded with nuclei which are rather rounded  than those of unstriped
muscle,  and  more  loosely  attached to the contractile  material.   The
principal direction  taken by the  fibres is  towards the  pupil, although
they are  more  or  less meandering  and  interlacing  in  this course.
Arrived  near the pupil,  they appear to join, and form indistinct arches.
In many instances  it is easy to/ detect a set  of circular fibres, either
gathered  into a  principal bundle  near the pupil or more diffused, but
always lying in  front of the others.  These  seem to answer to the
circular fibres of the bird's iris, which are of the striped variety, arid
  Network of yellow fibrous
tissue at the border of the
elastic laminaof the cornea:
— a. Outer border, where the
fibres approach the iris.  At
their inner end, 6, they are
lost on the elastic lamina.—
Magnified 70 diameters. 
412
INNERVATION.
occupy the front of  the  membrane.   There  may also be usually dis-
tinguished in  the very thin  margin of the pupil an arrangement of
fibres more circular than radiating.
  The  iris is so vascular that some anatomists have considered it
erectile, and have  erroneously ascribed  its  movements to this pro-
perty.   But its vessels are slender and delicate, and  resemble those of
the unstriped  muscle.   They are  derived chiefly from the two long
ciliary arteries,  which on approaching it bifurcate, and  form a circle
around it, whence pass  inwards a great number of  minute branches,
which form loops near the pupillary margin.
  On the anterior surface near the pupil  a vascular circle marks the
line from which in the foetus the membrana pupillaris stretched across
in front of the pupil.  This membrane at that early period divides the
anterior from the posterior chamber,  and  receives from  several parts
of the  circular vessel last mentioned,  small branches which approach
the centre, and  then return in arches, after inosculating sparingly
across the central point.   The membrana pupillaris is almost absorbed
at birth.
  The grayish structure coating the choroid for about an eighth of an
inch  behind the  cornea, presents at its  anterior edge a more white
and opaque circle, the ciliary ligament,  which  seems to be chiefly of
a fibrous character,  and  to connect the border of the iris firmly to the
sclerotic.  The plexiform tissue of the posterior elastic lamina of the
cornea  already  noticed, adjoins  this ligament, and partially blends
with it.
  The ciliary muscle is that grayish, semi-transparent structure  behind
                        the  ciliary ligament, and covering  the out-
                        side of the   ciliary body.   It has been de-
                        scribed as muscular by many  of the older
                        anatomists,  especially by  Porterfield, while
                        others have  assigned  to it a different  cha-
                        racter.   Lately it has been so  regarded by
                        Wagner  and Dr.  Wallace  of  New York,
                        and we believe correctly.   It belongs to the
                        unstriped variety of muscle, and its fibres
                        appear to radiate  backwards from the junc-
                        tion of the sclerotic and cornea,  and to losa
                        themselves on the outer surface of the ciliary
                        body.   The  more  superficial  fibres are in
                        contact  with, but  scarcely  adhere   to, the
                        sclerotic, and are inserted  into the posterior
                        part of the   ciliary body;  while  the  deeper
                        ones seem to dip behind the iris to the more
                        prominent parts of the ciliary processes which
                        approach the lens.   The ciliary muscle must
                        have the effect of advancing the ciliary pro-
                        cesses, and  with  them the  lens, towards the
cornea.  The ciliary nerves pierce this  muscle  on  their  way to the
iris, distributing to it many filaments which may be  seen for the most
part to cross the fibres.
 Diagram to show the position
and action of the Ciliary Muscle :
—a. Sclerotic, b. Cornea, c. Cho-
roid, separated a little from the
sclerotic, d. Situation of the ci-
liary ligament, and point  from
which the ciliary muscle  radi-
ates, e. Iris. n. Lens, connected
with the ciliary processes by the
anterior wall of  the canal of
Petit, the situation of which is
marked by the *.—Magnified 'J
diameters. 
STRUCTURE OF THE RETINA.
413
    The muscular nature of this structure is confirmed by its anatomy in birds, where
  it is largely developed, as noticed by Sir P. Crampton. We find its fibres to be of
f  the striped variety, like the circular fibres of the iris in the same class, and to be sup-
  plied by ciliary nerves traversing the muscle in a circular  direction. They likewise
  all radiate from the cornea, at the circumference of which they are attached to the
  deeper layers of the cornea proper, the elastic lamina being here exceedingly thin.
    Within the choroid is the  retina, which we  shall  describe as a
  structure distinct from the  optic  nerve, though  continuous with it;
  reserving our account  of  that nerve, and of  the others pertaining to
  the eye,  till the anatomy  of the globe is  concluded.
     The  retina is the  sheet  of nervous  matter  which  receives the
  images of external objects thrown upon it by the transparent media,
  and it  is accordingly placed immediately behind the  vitreous humor,
  the deepest of those  media.   It  may be said  to commence  at the
  foramen  in the  sclerotic and choroid by  which the optic nerve enters
  the eye,  and to  terminate by a finely jagged  border  (the ora serrata)
  at the  hinder border of the striated part of the ciliary body.  It  is
  thicker behind, in the deepest part of the globe,  and gradually thinner
  forwards.  Of  a pinkish-gray tint, and  semi-transparent when fresh,
  the images formed  upon it may be seen through it  from  behind, if
  the sclerotic and  choroid coats be first carefully removed.  When
  thrown into accidental folds, it resembles in  appearance the vascular
  gray substance of the cerebral convolutions.  The exquisite function
  performed  by this nervous  membrane, its expanded form  and  sepa-
  rability from other structures, have always made  it an object of pecu-
  liar interest with physiologists, who have not unreasonably expected
  that important secrets of nervous  function might be  disclosed by an
  accurate insight into its structure.   Whatever the conclusions  to be
  drawn, it is certain that this  structure  is elaborate and  complex, and
  worthy of an attentive study.
     The first part of the retina to be described is the fibrous gray layer,
  which  forms the immediate continuation of the optic nerve, and which
  is seated on its inner  surface.  This is  a layer of fibrous character,
  radiating from the end of the optic  nerve, and  apparently consisting
  of the  tubular fibres  of that nerve deprived of their white substance;
  that  is, being no longer  tubular  and white, but solid  and  gray, and
  united together more  or less  into a membrane.    This  at least seems
  to us to  be certain, that  the  white  substance of Schwann does not
  exist in the nervous substance of the retina, but ceases as the nerve
  perforates the sclerotic.  It has been particularly described as existing
  in the  retina of the rabbit; but the fact seems to be, that in this animal
  the nerve does  not end in the retina till  some way within the globe,
  for, after bifurcating and spreading out  as a white streak within the
  choroid, the bundles of nerve-tubes suddenly lose their white lustre,
  and  assume the appearance of the gray fibres of the layer now under
  consideration.   These  bundles, both  in animals and  man,  may be
  seen to anastomose  in a close plexiform manner, especially near the
  optic nerve, and finally constitute a thin sheet, which  becomes thinner
  and  less fibrous as we trace it forwards,  until at length it can  be no
  longer  discerned.   This fibrous gray layer of the retina is united  to
  the hyaloid membrane, containing the  vitreous  humor, by a layer of 
414
INNERVATION.
nucleated  cells  almost  perfectly  transparent,  and  sometimes  very
difficult of discovery on that account.   It is to  be remarked, that the
fibrous gray layer is the only nervous  element  of the retina existing
over the extremity of the  optic nerve where it enters the globe—a
spot incapable of vision.   Immediately around  this spot, the other

                               Fig. 117.
  Vertical section of the Human Retina and Hyaloid Membrane, h. Hyaloidmembrane. A'. Nuclei
on its inner surface,  c. Layer of transparent cells, connecting the hyaloid and retina,  c'. Sepa-
rate cell enlarged by imbibition of water,  n. Gray nervous layer, with its capillaries.  1. Its fibrous
lamina.  2. Its vesicular lamina. 1'. Shred of fibrous lamina detached. 2'. Vesicle and nucleus
detached, g-. Granular layer. 3. Light lamina frequently seen. g'. Detached nucleated particle
of the granular layer,  m. Jacob's membrane,  m'. Appearances of its particles, when detached.
m".  Its outer surface.  Magnified 320 diameters.

layers commence which  have  now to be described, and the  first of
these is the vesicular gray layer.  This layer is on the outer surface
of the fibrous  layer, and  so  intimately blended with  it, that it might
almost seem as if the fibres successively terminated in it.    The vesi-
cular layer is thicker behind, and gradually thinner forwards.  It very
accurately corresponds with the vesicular  matter of the convolutions
of the  cerebrum, consisting  of  a finely granular matrix with inter-
spersed very delicate vesicles, furnished with pellucid globular nuclei
of characteristic appearance.
  The blood-vessels of the retina, which are thickly distributed, be-
long solely to the fibrous and vesicular layers  now mentioned.   The
central artery of the retina, after entering the globe in the axis of the
optic nerve, sends four or five radiating branches, which almost imme-
diately perforate  the fibrous  layer and  spread  out in a beautifully
arborescent  manner, as a capillary network  in the  substance of the
vesicular  stratum.   After slight maceration, it is easy to  wash the
nervous material  out of the meshes of the vessels; and they then form
a vascular layer, but which it is hardly correct to  describe as a dis-
tinct lamina of  the retina.  They are  merely the  nutrient vessels  of
the  part, and are  the representative of the close network  of the gray
substance  of the cerebral convolutions.  Their wall is a  diaphanous
membrane with nuclei projecting at intervals, and the meshes average
T^o of an inch diameter.
  Behind  the  vesicular  gray layer is  the granular layer, a terra  we
shall  apply to it, because it seems to  consist of a close  aggregation 
STRUCTURE OF THE RETINA.               415
of small granules, which refract the light more  powerfully than the
neighbouring parts, and have scarcely any appearance of intervening
matrix; they might be regarded perhaps as analogous to the nuclei of
cells, and much resemble a layer of granules in the substance of some
of the cerebral convolutions, and of the laminae of the  cerebellum.
They are made more evident by acetic  acid.  This layer is divided
into  two, of which the  inner is much the narrower, by a pale stratum,
which can  only be seen by very careful  manipulation.
  On  the  outside of the granular  layer is that  remarkable lamina,
known  by  the name of its discoverer,
the  membrana Jacobi.   It consists  of            Fig. 118.
club-shaped  rods,  placed uprightly
 the  thin  end inwards, the  thick out-
 wards ; and  it is very easily detached                    5|Gi|SjKij
 from the  rest of the  retina, when the
 choroid is removed,  so as to float as
 delicate  shreds,  visible to  the  naked
 eye, in the water in which  the  eye is
 immersed.   The rods have a tendency
 to separate  from one  another  when
 placed in water, and  the  club-shaped
 extremities  are then  often seen  to  be
 formed by a sudden  bendinp- back of   outer surface of the Retina, showing
 ,        •'.             i • i          the membrane of Jacob, partially detach-
 tne  stem  like a crook, which may be  ed. After Jacob.
 more or less opened out.  Interspersed
 among the rods are seen on the outer surface a number of clear spaces,
 as though transparent cells were disseminated  among them.  This
 layer forms the connecting medium between the retina  and the cho-
 roidal epithelium.
   It has been before stated that  the optic nerve  pierces the sclerotic
 and joins  the retina about an eighth of an inch on the inner side of the
 axis of the  eye.  Precisely in this axis, the retina is of a decidedly
 yellow colour in a roundish  spot of about 2V of an inch  diameter,
 called, after  its discoverer,  the  yellow  spot of  Scemmerring.  This
 spot exists only in man and the monkey among mammalia, but  an
 analogous part has been found by Dr.  Knox in reptiles.   It has been
 described by some as a fold, by others  as a foramen in the retina, and
 after several  examinations we should  speak of it as a small mound,
 or projection  of the retina towards the vitreous humor, with a minute
 aperture in the summit.   On  removing the sclerotic and choroid with
 the utmost care, the interior of the  globe can be seen from  the out-
 side, through this hole; and yet the membrane of Jacob appears to be
 continued over it.  On examining the  structure of the retina about
 the yellow spot, from within, the fibrous expansion of the optic nerve
 (though  stretching in every other  direction to a much greater dis-
 tance) cannot be traced quite up to the spot itself.   Nucleated cells
 occupy the elongated meshes of  the fibrous plexus already described,
 until at length the fibres disappear, and  the closely set cells seem to
 cover the whole surface of the spot.   The gradual subsidence of the
fibres in the interstices of the cells we have distinctly seen.   As for 
416
INNERVATION.
the  colouring  matter,  it is not in grains of pigment, but stains the
several tissues, and  soon disappears in water.   The use of the yellow
                     spot is unknown.  It is interesting to observe, in
      Fig. H9.         connection with  the perfection of vision over the
                     spot, that  the ^principal  branches of the artery
                     and vein of  the  retina, above and below, curve
                     round it at a  distance, going, as it were, out of
                     their course  to  avoid it,  so  that only  capillary
                     vessels are found in  its immediate vicinity.
                       It  now  remains  to  describe  the  transparent
  The yeiiow spot of the   media which occupy the interior of the ball  of
Retina occupying the axis   +y,p pVP
of" the  eye; and the en-   wc cjrc. ^
trance of the optic nerve,     The  vitreous  body, lymg in the  concavity of
with the arteria centralis   ,,     ,.       , «...     ,, , ° .   ,   .   ,     .  J.
retinas on the inner side of   the retina, and rilling all but about the anterior
the^axis.-After Summer-   fifth of ^ g^ ^  ^^  ^j^ the ^^
                     ence of soft jelly.  It consists of an exceedingly
fine and close, but perfectly transparent web  of fibrous tissue, the
meshes of which are exceedingly small, and  contain an aqueous fluid.
If the tissue be cut into, the  water will slowly  drain off, showing the
continuity  of the  cells  with  one  another;  and the manner in which
they are constructed by interlacing  fibres  may be very plainly seen
with  a high power near the ciliary processes, in the vicinity of which
these fibres  are  particularly  strong.   The  whole vitreous  body  is
bounded by or contained  in an envelop  of extremely thin homoge-
neous membrane,  having corpuscles or cell-nuclei on its inner surface,
where the fibrous tissue is attached (fig. 117, h, h').  It would perhaps
be convenient  to restrict the term hyaloid  membrane to this envelop.
Where   the retina extends, that  is,  as far  as   the ciliary body, the
hyaloid  membrane is in  contact with its inner surface,  and united
to it  by an extremely transparent layer of cells, which  often remain
invisible until swollen by the imbibition of  water  (fig. 117, c, c').
These cells serve  merely as a bond of  connection between the hyaloid
membrane  and the fibrous lamina of  the  retina.  Between the ante-
rior border of the  retina and the border of the lens, the vitreous body
is accurately adapted to the ciliary strise and processes of the  choroid,
and presents a  series of plaitings precisely similar to those of the pro-
cesses themselves, and termed the ciliary processes of the vitreous body.
Collectively they form a circle called  zonula ciliaris, or, zone  of Zinn.
The two structures are  in a manner dovetailed  into one another;  and
so intimate is their union, that, when the processes of the  choroid are
drawn away from  the vitreous body, some of their pigment  is gene-
rally left adhering to the processes of  the latter.
   In the centre of its anterior surface,  in a space nearly corresponding
to the area  between  the points  of the ciliary processes, the  vitreous
body is  hollowed  out to receive  the  crystalline lens.  This  latter is
contained in, or bounded by,  a perfectly closed capsule, composed of
a tissue  exactly resembling the  elastic lamina of the cornea  already
described.   To the  whole posterior surface  of this capsule, and to a
very narrow circumferential portion of its  anterior surface, the fibrous
structure of the vitreous body is firmly attached;  the hyaloid  mem-
 
VITREOUS BODY.—CRYSTALLINE LENS.           417
Fig. 120.
brane itself not passing behind the lens, but  adhering to the capsule
all round a little in front of its rim,  after crossing the  interval sepa-
rating the tips of the  ciliary processes of the  choroid  from the  lens.
Thus the rim of the lens is not exactly at the surface of the  vitreous
body, but buried slightly  within  it, and over-
lapped a little by it.   All round the rim of the
lens, there is a cavity in the vitreous body, ex-
tending  under the circle of the ciliary processes
of the latter, and  termed the canal of Petit (fig.
120, and  fig.  J16*).   The hyaloid membrane
constituting  these ciliary  processes forms the
anterior  wall of this canal, which, by its adhe-
sion to the ciliary processes of the  choroid,  is
subject to be drawn forwards by the  contraction
of the ciliary muscle already described (p. 412).
When this occurs, the lens also is advanced,  in
consequence of the union of this  anterior wall
of the hyaloid to its anterior surface near the
rim.  Were the  canal  of  Petit wanting,  the
ciliary muscle  would act rather on the vitreous body around the lens,
than on  the lens itself.  Its existence may be  easily shown by filling
it with mercury or air, through  an  artificial orifice in its anterior wall.
The injected fluid fills out the plaitings of the ciliary processes.
  The refracting  index of ihe  vitreous  body is  about 1-339, that of
water being 1*336, so that the difference  between them is very trifling,
and  may be referred  in part to the transparent  fibrous tissue.   Its
chemical constitution, according to Berzelius, is as follows:
 Position of the Lens in the
vitreous humor, shown by an
imaginary section. Thedark
triangular space  on each
side of the lens is intended to
indicate the position of the
canal of Pelit—After  Ar-
nold.
Water   ....
Chloride of Sodium, with extractive matter
Albumen
 98-40
  1-42
   •18

100 00
   In early life the vitreous body gives passage by a canal to a branch
of the  central artery of the retina to the back of the lens; and in large
animals, though not in man,  this appears to supply some branches to
the vitreous body itself even in the adult state.
   The  crystalline, as already mentioned, is a  double  convex  lens;
but its surfaces are of unequal curvature, the posterior being the more
convex.  In the adult the differ-
ence is nearly  as 4 to 3, but  it is                rio-  121-
liable to some variety in different
subjects.   Chossat has observed
that the curvatures of the  lens in
the ox are ellipsoids of revolu-
tion  round the lesser axis,  but
whether they are so in man is not
determined:  the  subject  is  one
very  difficult  of  investigation.
The  lens alters its shape with age; being  in the foetus more spherical,
more flattened in childhood,  and still  more so in advanced life.  In
 Human Lens: —a. At birth,  b. At six years
old.  c Adult, d. Hardened in spirit, and par-
tially separated into segments.—After Soemmer-
rinsr. 
418
INNERVATION.
122
infancy it projects into the aqueous humor so as to touch the iris; but
in old  age there is a space intervening.   The lens also varies in con-
sistence  with  age ; being very soft at an  early period, very firm in
declining years.  At no epoch of life, however, is it of uniform con-
sistence  throughout;  being  always denser and  firmer from without
inwards.  In the adult its diameter is from £ to # of an inch, and its
antero-posterior axis  about £ to } of an inch.   It weighs  from three
to four grains.
   The lens is divided into capsule  and body.   The  manner in which
it is encased and fixed by the capsule in the vitreous body, has been
already described.  It only remains to add, that the anterior wall  of
the capsule is nearly four  times thicker than the posterior; greater
strength  being required  in front, where  the  surface is  free in the
aqueous humor, than behind, where it is adherent to the tissue of the
vitreous body.   The diminution in thickness does not occur abruptly
at the rim of the  lens,  but  commences  gradually on the anterior
surface near  the  rim, at a line  corresponding  to the  attachment  of
the anterior wall of  the  canal of  Petit.   The  capsule is perfectly
closed, and cannot allow  of  the passage of either vessel or nerve  to
its interior.
   The body of the lens is  constructed in a manner calculated to excite
                                          admiration.   Its  super-
                                          ficies, by which it comes
                                          into contact with the cap-
                                          sule, consists  of a  layer
                                          of extremely transparent
                                          nucleated  cells  repre-
                                          sented  in fig.  122,  a.
                                          These cells form an or-
                                          ganized connecting me-
                                          dium between the  body
                                          and  capsule of the  lens,
                                          and there is no interspace
                                          not  occupied  by them.
                                          After  death  they  very
                                          soon become loaded with
                                          water  (absorbed  most
                                          probably by the  capsule
from the  aqueous humor), which  is the aqua Morgagni, that  some
have supposed to exist naturally between the capsule and body of the
lens near its border.
   The body of the lens is composed of fibres  superimposed  on one
another, and  united side to side in lamina?, of  which many hundreds
must exist.  The mode of arrangement of the fibres is, however, more
artificial than this.  In the mammalia in general there  are visible on
the front surface, when  the lens has slightly lost  its transparency,
three  lines, extending from  the centre two-thirds to the border, and
dividing it into three equal parts:  and on the  opposite surface  three
similar lines  exist, having an  intermediate position.   From and to
these  lines the fibres pass from surface to surface.  Thus, a fibre pro-
 a. Cells connecting the body of the lens to its capsule (hu-
man), b. Fibres of the lens, with slightly  sinuous edges
(human), c. Ditto from the Ox, with finely serrated edges.
d. Ditto from the Cod j the teeth much coarser.—Magnified
320 diameters. 
STRUCTURE OF THE LENS.
419
ceeds from the centre in front, advances midway between two of the
lines over the border, and comes on the  opposite surface  to the ex-
tremity of one of the lines.   Others pass from the extremities of the
lines in front, and are lost in the centre behind.   And the rest of the
superficial  plane are intermediate to these, and as  nearly parallel as
their curved  course will allow.  If we now consider that these lines
on the surface are  but  the edges of planes which dip to  the centre,
and afford points of divergence and concourse  for all the  fibres deep
as well as superficial, we shall readily comprehend what may at first
sight seem an intricate  structure.   This arrangement was known to

               Fig. 123.                       Fig. 124.
elude about a hundred fibres.
—Magnified 3 diameters.
 Leeuwenhoeck, and  has been shown by Sir D. Brewster to present
 varieties in different classes of animals.   In the  human lens we find
 the tripartite division is seen imperfectly, and only in the centre ; for
 the three primary diverging lines bifurcate again and again, and with
 considerable irregularity, so that the ultimate subdivision is into from
 twelve to sixteen  parts in the adult,  but only from four to six in  the
 foetus.
   To the  account now given may be added, that as the fibres  are
 shorter in proportion as they are more  internal, so do they appear
 narrower, more cylindrical, solid,  and  intimately  united to  each
 other, as we trace  the  structure inwards.   The superficial fibres  are
 flattened according to the surface they answer to ; and of all it may
 be  said, that they are narrower  towards their extremities, as their
 arrangement renders necessary.   The edges of the fibres in fishes  are
 most  beautifully toothed, and dovetailed together, as  Sir D. Brewster
 pointed  out  (fig. 122, d); and something similar  may be detected in
 the more superficial fibres of the lens of the larger mammalia, and in
 man.  But the  deepest  fibres present scarcely any trace of this ele-
 gant structure.   Near the tripartite division  of the lens the fibres  are
 more  united than  elsewhere, and appear more or less consolidated
together.  The average thickness of the fibres in man is about ToW °f
 an inch.
  The increasing  density of the  lens towards its  centre is attended
with an  increase of  the  refracting power, designed  to  augment the 
420
INNERVATION.
convergence of the  central  rays of the transmitted pencils in their
course through the lens, and thus to bring them to the same focus with
the circumferential rays.  Sir D. Brewster states the refracting power
of the lens at its surface to be 1-3767, and at the centre 1-3990.
   The lens,  during its  development, has a very copious  distribution
of blood to the outer surface of its capsule, from two  sources.  The
central artery of the retina sends a vessel through the vitreous humor
to the centre of its posterior surface, which branches into a radiating
series  of capillaries  investing it as far  as  the border, where they
anastomose with vessels derived from  the ciliary  processes, which
proceed some way over the front of the capsule, and return in loops.
None of these vessels continue after the lens has attained to maturity.
   The lens consists chiefly of albumen, and becomes hard and opaque
by boiling.   The central parts evidently contain a smaller proportion
of water than the outer layers, which merely become flocculent by the
action of heat.   The  fibrous and  lamellar structure is more easily seen
when thus rendered  opaque, and it then  separates more easily along
the triple or multiple  planes  already indicated.  Berzelius states the
precise chemical constitution of the lens to be as follows:
       Water   .       .       .       .        .       .58-
       Albumen        .....  35-9
       Alcoholic extract, with salts  ....   24
       Watery extract    .        .       .        .       .1-3
       Membrane       .....   2'4

                                                     100-0
   The aqueous humor, as- its  name imports, is very nearly pure water,
containing, according to Berzelius, less than a fiftieth of its weight of
other matters, of which  more than half is chloride  of sodium, and the
rest extractive, soluble either in water or alcohol.
  It fills up the space between the cornea and lens—a space divided
into two cavities  by the membrana pupillaris in the foetus, and still
partially divided  by the iris into an  anterior and posterior chamber,
continuous through the  pupil.   The anterior, though small, is much
larger than the posterior, and is bounded by the cornea in front, the
iris behind, and a portion of the ciliary ligament at its circumference.
The posterior is bounded by the iris in  front, the  lens  and a  narrow
circle of hyaloid membrane  behind, as well as by the ciliary processes
which slope towards the iris, and thus limit the lateral dimensions of
the chamber.  It is very  easy to imagine the existence  of a lining
membrane to this cavity of the aqueous humor, such  as would form
a closed sac, and answer to the serous structures;  and  a membrane of
the aqueous humor has accordingly been described by several  anato-
mists.   But  the  most careful  observation fails to  detect  any such
serous sac, though the  posterior epithelium  of the cornea (p. 407)
closely resembles that of  serous surfaces.  No epithelium  exists in
front of the iris, and certainly none is present on the anterior surface
of the lens:  this we can aver  from repeated examination.   On the
posterior surface of the iris, however, there seems  to be a pigmentary
membrane.
   Of the Optic Nerves, and their central connections.—The  second 
THE OPTIC NERVES.
421
Fig. 125.
 PI an of the optic nerves on
a small scale, showing their
divergence from the chias-
ma, c. and their junction with
the globe, on the inner side
of the axis of the humors.
pair of nerves is devoted to the  sense of sight, and  on  that account
has received the name of Optic Nerves.
  The marked manner in which these nerves terminate inthe retinas,
the  constant  relation in size between them  and the organ  of vision,
the  atrophy which  they suffer  when  the visual apparatus has been
destroyed,  the impairment or loss of vision which follows a morbid
state of them, place it beyond  all question that  they are the proper
conductors of visual impressions to the sensorium.
  The optic nerves form a most extensive connection with the brain
through  the  optic  tracts.  The optic tracts are
two flattened bands of nervous  matter, which
proceed from the posterior and superior surface
of the mesocephale (the region of the quadrige-
minal tubercles) forwards along the inferior  sur-
face of each crus cerebri,  and after passing  in a
curved course (concave inwards) along the base
of the brain,  unite in front of the tuber cinereum
and mamillary bodies, and form a  very intimate
junction, which  is  called the  chiasma or com-
missure of the optic nerves.
  From  this chiasma  the optic nerves spring,
and diverge as they pass forwards into the orbits
through  the  optic  foramina.   This  point  may
be  looked  upon, therefore, as their Origin.   To
understand, however, more exactly their relation
to the brain, it will be necessary to trace the connections of the optic
tracts, and to inquire into the structure of the chiasma.
  In tracing each optic tract back from the chiasma, we find that  it
first forms a pretty close connection with the locus perforatus on the
outside, and with the tuber cinereum  on the inside.   Whether any  of
its  fibres  spring from  the tuber cinereum  is matter  of  great uncer-
tainty.   Further back the optic tract adheres by its outer  margin  to
the crus  cerebri, and is concealed by the  middle lobe of  the brain.
In this course it expands considerably, and at  the posterior  edge  of
the crus cerebri  it forms intimate connections with certain gangliform
masses of the brain.  First,  we observe its connection with  the ex-
ternal geniculate body, a small prominent  tubercle of darker colour
than the  surrounding parts, and situate at the posterior margin of the
crus; it seems to involve the outermost fibres  of the tract, as a gan-
glion, and from it a band of fibres is continued back to the posterior  of
the quadrigeminal  bodies.   Beneath the posterior extremity of the
optic thalamus the innermost fibres of the tract form a  connection with
another similar body, the  internal  geniculate body, from  which fibres
are continued backwards to the anterior of the  corpora quadrigemina.
The tracts, thus, appear to divide, each into two bands:  of which the
outer one, after passing through the external geniculate body, reaches
the testes; and  the inner one, similarly related to  the internal geni-
culate body, reaches the nates.
  The optic tracts are connected with the optic thalami chiefly through
the  geniculate bodies.  Each tract adheres to the outer side cf its cor- 
422
INNERVATION.
126.
 Course of fibres in the chiasma, as exhibited by
tearing off the superficial bundles from a specimen
hardened in spirit, a. Anterior fibres, commissural
between^he two retince. p. Posterior fibres, com-
missural between the thalami.  a',p'. Diagram of
the preceeding.
responding thalamus for some distance, but whether  any fibres sink
into it is not determined.   In the horse, dog, sheep, and  monkey,
this arrangement  is very conspicuous, as the greater portion of the
fibres of the tract expands  over the internal geniculate  body, which
is incorporated with the posterior extremity of the thalamus.   The
diameter of the tubules of the optic  tracts  we have found  to  vary
from Y7V0"  to 50V0 °f an inch.
   The chiasma results from the junction of the optic tracts in  front of,
and inferior to, the tuber cinereum.   The fibres which form the inner
                                    margin of each tract, p, are con-
                                    tinued  across from  one side of
                                    the brain to the other, and form
                                    no connection  with the  optic
                                    nerves,  and exist  where  those
                                    nerves  do not exist, as in the
                                    mole.   These fibres may be re-
                                    garded as commissural  between
                                    the  thalami of opposite sides.
                                    The  remaining  fibres  of  the
                                    tracts  go  to  form  the  optic
                                    nerves; the central ones  pass
                                    into the  nerve  of  the  opposite
                                    side, decussating   the  similar
fibres of the other tract;  and the outermost  fibres, much fewer in
number than the central  ones, pass to the optic nerve  of the  same
side.
   This disposition of the fibres of the chiasma may be demonstrated
on a specimen which has been sufficiently hardened in spirit, by tearing
the fibres in their proper direction  after the removal of the neurilemma.
By such a  procedure it may be shown that each optic nerve derives
its principal fibres from the tract  of the opposite side, and only a few
fibres from those of its own side.
   The existence of such a decussation of fibres in the  chiasma is,
moreover,  rendered highly probable by the strong indications of most
extensive decussation, resembling that of the anterior  pyramids, in
some of the large carnivorous  birds,  and also in the crossing of the
entire optic nerves in some of the osseous fishes, the cod  for example.
   In the  common domestic  quadrupeds the decussation  of the fibres
is  not to be made out so  plainly, probably from its being more  com-
plicated.    The chiasma somewhat resembles a knotted °union of the
two  tracts,  which is dense and  firm in structure.
   The optic nerves appear also to be connected by fibres, forming the
anterior border of the chiasma, and which may be regarded  as com-
missural between the two retinas  (a, fig. 126).
   From  the quadrigeminal  tubercles to  the chiasma,  nerve-tubes,
mostly of large size, are visible by the microscope in the tracts.  In
the chiasma and the optic  nerves, the fibres, although  very  variable
in size, are so closely connected  together that it is exceedingly diffi-
cult  to separate them.   They  seem to be collected into numerous
small bundles, having an intricate plexiform interlacement within the 
THE OPTIC NERVES.
423
common sheath.   Each bundle is  surrounded by a firm but dense
neurilemma, and thus it is impossible by the ordinary means of mani-
pulation to  separate a portion of the  nerve of sufficient delicacy to
examine any considerable  length of its fibres.
The size and character of the  fibres may be          Fi(r 127
estimated by examining   portions  of  them
which project from the margin of the piece.
   The  optic nerve is  abundantly  supplied
with capillaries, which form a network with
elongated meshes in its substance.  A little
behind the  globe,  it receives from the oph-
thalmic artery a branch,  before  alluded  to,
the arteria centralis retinas, which penetrates
to its axis, along which it runs to the interior   ^TeZlt^™ ™e%Sf
of the eye, in a canal of fibrous tissue.  This   various sizes, and varicose. At
,      11       i-              ii      •      a tne central axis projects be-
brancn then radiates  to  supply the retina,   vond the white substance at a
and in the foetus sends forwards a twig to the   £a°raen ^^m^-M^n- 32°
lens.   It is  accompanied everywhere by cor-
responding  veins.
   Other nerves are distributed to the  eye, which are connected with
the nutrient and other actions of the eyeball.  These are derived from
the ophthalmic division of the fifth, from the third pair, and from the
sympathetic.  It is remarkable, however, that all these nerves, with
two exceptions, between  their origin  and  their distribution in  the
globe of  the eye,  meet in a small ganglion situated on the  outer side
of the optic nerve,  called the ophthalmic or lenticular ganglion.  This
body is usually considered a portion of the  cephalic division of the
sympathetic; it is connected with the superior  cervical ganglion by a
long branch which ascends from the carotid plexus along the carotid
artery, and  enters the orbit.   A long nerve  from the nasal  branch of
the ophthalmic division of the fifth also joins this ganglion at its supe-
rior and posterior angle, and a short thick branch from the third nerve
joins the  ganglion at its inferior  posterior  angle.  From the anterior
angles of the ganglion thus formed, proceed two bundles of delicate
nerves, from twelve to sixteen in number (ciliary nerves), which, after
having pierced  the sclerotic at its posterior  third, pass  between that
tunic and the choroid, and are distributed chiefly to the ciliary muscle
and iris,  but also to the cornea.
   From the nasal branch of the ophthalmic there proceed two  long
nerves, called long ciliary nerves, which do not form  any connection
with the  ophthalmic ganglion.   These nerves pass off in  company,
but soon separate from each other,  one going to the inner, the other
to the outer side  of  the  eyeball;  they penetrate the sclerotic,  and
accompany the other ciliary nerves  in their distribution to  the ciliary
muscle and iris.
   The eye  is moved by six muscles, four straight and two oblique.
The former arise from  the margin of the optic foramen, at the apex
of the orbit, and are inserted into the sclerotic near the cornea, above,
below, and  on each side.   The superior oblique arises with the recti,
but has its direction changed by a pulley of fibrous tissue at the upper 
424
INNERVATION.
and inner  part of the margin of the orbit;  whence it passes back-
wards, outwards, and  downwards, under the superior rectus  muscle
to the sclerotic behind the transverse median plane of the globe, be-
tween the  superior  and external  recti.   The inferior oblique arises
from  the lower part of the margin of the orbit, about its inner third,
and passing backwards, outwards, and  upwards, under  the inferior
rectus, is inserted into the sclerotic, near, but beneath the superior
oblique.   The action of the recti muscles is obvious:  when used in
concert,  they fix the eyeball;  when singly, they turn it towards their
respective  sides.   The globe, besides being imbedded in fat, is sus-
pended  or  slung in a capsule  of  fibrous tissue, with which it is in
immediate contact.  This is attached in  front to the tarsal cartilages,
and is prolonged backwards over  the globe  and  optic  nerve, after
being perforated by  the  muscles.   Mr. O'Ferrall, who has lately
directed  attention to this fibrous structure, has termed it the tunica
vaginalis oculi.   It is important, as furnishing  support to  the eyeball
under muscular movements.   The recti  muscles are supplied  by the
third  pair of nerves, except the external, which receives the sixth.
The  oblique muscles  antagonize  the recti, and  must in  addition, if
acting together, draw the globe inwards, and converge  the axes of
the eyes.  The superior oblique, if alone, would most probably direct
the front of the eye downwards and outwards, and the inferior oblique
upwards and inwards; but on these points much difference of opinion
still prevails.   The  former is supplied by the fourth pair, the latter
by the branch of the third that gives the motor fibres to the ophthal-
mic or lenticular ganglion, from  which  the  ciliary muscle and  iris
receive their nerves.   And, in connection with the latter arrangement,
it is interesting to remark that the pupil  contracts when the eyes  are
directed  inwards  and upwards, and generally also in the  adjustment
for  near  vision, which is attended with  a convergence of the optic
axes.  During sleep the eyes are usually turned inwards and upwards,
and the pupil  is contracted—actions  produced through the medium
of the inferior division of the third pair supplying the inferior oblique
and  iris.   The iris  is  evidently involuntary in its movements;  it
contracts only  in obedience to this  stimulus of light upon the  retina,
or when  the eye is turned upwards and inwards.
  The eyelids are exquisitely adapted to shield the eye from too strong
light, and to protect its anterior surface  from the contact of hurtful
substances.   In the upper lid, which is much larger and more move-
able than the lower, there is a thin  sheet of  cartilage, curved to  fit
the  front of the eye, and to facilitate its gliding motion over the globe.
To  the posterior  convex border of this   tarsal  cartilage  the levator
palpebral muscle is attached, which thus  serves to elevate the whole
lid.   The lower lid possesses a very narrow  slip of cartilage, which
meets the upper at each side through the medium  of fibrous  tissue,
which, at the outer angle of the eye is attached  loosely to the malar
bone, and at the inner angle forms  a tendinous cord, the  tendo oculi,
about a quarter of an inch long, which passes horizontally  to be fixed
to the nasal process  of the superior  maxillary bone.  This latter is
the  principal  attachment of the eyelids.  The  eyelids enclose  the 
THE EYELIDS.
425
orbicularis muscle  between the skin and  their cartilages.   Its fibres
run in curves from the lower border of the tendo-oculi  and neigh-
bouring part of the border of the orbit, encircling the eye and form-
ing a thin layer under  the  skin, both of the lids, cheek, and  brow,
and returning to the upper border of the tendo-oculi.  They are sup-
plied by the portio  dura, and perhaps by some fibres of the fifth nerve,
and act generally in answer to the  stimulus of air or foreign  particles
on the fifth nerve in the conjunctiva, as well as of a too strong light
upon the retina.   The  will exerts a limited power over the orbicula-
ris, but is quite unable  to restrain its action  when sufficiently excited
by the before-named  stimuli.  The entire muscle consists of striped
fibres.  The lids are further armed along their free margin by the
delicate curved hairs, called the lashes. These intercept the entry of
foreign particles directed against the eye,  and assist  in defending the
organ  from excess  of light.
  At the border of the eyelids, the skin  becomes continuous with their
mucous lining, termed  the conjunctiva.   This membrane lies  upon
the tarsal cartilages, and is then reflected over the front of the globe,
where it has been  already in part  described with  the cornea.  Be-
tween the cartilages and the
the former,  are  the  Meibo-
mian glands, which may be
seen through the conjunctiva
(figure  128).  Each gland
consists of a series of  folli-
cles, arranged upon an elon-
gated  common  duct, which
empties itself on the  border
of the lid.  They consist of
a basement  membrane  and
an  epithelium  (fig.  129);
the latter contains sebaceous
matter in its cells,  and  is in
continual  course of  forma-
tion.   Its  particles, when
fully developed, are  thrust
forward along the duct,  and
constitute the secretion.  The-
use of the Meibomian glands
is obviously to prevent  ad-
hesion of the lids; and  their
arrangement  side by side, so as to form an even layer, adapts them to
the surface of the globe, over which they are being constantly moved.
They are  a variety of the  cutaneous  sebaceous glands, which they
resemble in every particular except shape.   At the  inner canthus is
a large-sized sebaceous gland, covered with  mucous membrane, and
usually termed  the  caruncle (fig. 130).
  The conjunctiva of the lids presents  on its free  surface a minute
papillary structure, probably connected  with  the exquisite sensibility
which renders this  membrane so valuable  a covering to the eye.   In
conjunctiva, and partially imbedded in

                Fig. 128.
 View of the conjunctival surface of the Eyelids. The
Meibomian glands are seen running towards the edges
of the lids:—I. The lachrymal gland removed with the
lids. d. Orifices of its seven ducts on the conjunctiva.
At the inner extremity of the borders of the lids the ori-
fices of the canaliculi (puncta lachrymalia) are seen. o.
o. Orbicularis muscle beyond the lids.—FromSoemmer-
ring. 
426
INNERVATION.
the disease termed granular lids,  these papilla? are hypertrophied.
To the sclerotic coat the conjunctiva is loosely attached by lax areolar
tissue in which numerous tortuous vessels lie.
   The front of the eye is irrigated by the lachrymal fluid secreted by
the gland of that name.  This gland is placed within the orbit, under
cover of the external angular process of the frontal bone, and is about
the size represented in fig. 128, I.   In appearance and structure it has
much similarity to the salivary glands;  its ultimate parts being vesi-
cular.   Its ducts, about seven in number, open on the  conjunctiva,
at its upper and outer part near its  reflexion on to the globe, and are
arranged  in a row, so as to  disperse their secretion over the mem-
brane (fig.  128, d).   The constant  motion of the upper  lid facilitates
the distribution of the fluid, which thus streams continually over the
Fig. 129.
Fig. 130.
 One of the Meibomian glands of
a Foetus of five and a half months :
—a. Basement membrane of the
follicles. 6. Epithelium constitut-
ing the secretion, c. Orifice of
the common duct.—From a speci-
men prepared by Dr. Goodfellow.
Magn. 30 diameters.
  Anterior view of the Lachrymal Apparatus —7.
The lachrymal gland in outline.  At the inner can-
thus are the puncta, 1, and canaliculi. 2, with the
caruncula between them.  The lachrymal sac forms
the upper third of the vertical tube, 5, 6, and the
nasal duct the remainder. These parts are sepa-
rated within by a fold of the lining membrane.
front of the eye, and  carries off any extraneous particles that  may
have found their way into it.   The fluid is then conducted into the
nostril through a singular system of channels, lined by mucous mem-
brane, continuous between that of the eye and nose.  Near the inner
end  of the border of each tarsus there is an orifice, a little prominent,
and  projecting slightly backwards, so as  not  to  be obstructed when
the lids are closed.   These are the puncta lachrymalia (figs. 128 and
130).  They lead by two ducts (canaliculi), into the lachrymal sac, a 
PHENOMENA OF VISION.
427
cavity  formed  by the  lachrymal  and superior maxillary bones, com-
pleted  by fibrous membrane.   This is  continued, under the name  of
nasal duct, into the  inferior meatus of the nose,  where it opens under
cover of the lower spongy bone.  A fold  of mucous membrane usually
guards its orifice.
   Of the phenomena of Vision*—The  consideration of the changes

  • The following laws affecting the passage of rays of light  through transparent
media of various density ought to be kept steadily in view by the student of the phy-
siology of vision.
  1. A ray of light,  in its passage from a rare into a dense  medium, is bent, or, in
optical language, refracted, towards the perpendicular to the point of incidence, if it
fall obliquely upon the surface of the latter medium.  The direction of the ray, there-
fore, is altered in the dense medium.   The degree of this refraction depends partly
upon the density of the medium, and partly upon the angle  at which  the ray falls
upon it (the angle of incidence).   If the ray of light fall upon the transparent surface
at right  angles to it,  it will  pass through it  without undergoing  any change in its di-
rection.                             \
  2. If the ray pass  from a dense to a rare medium, it will be refracted from the per-
pendicular to the point of incidence.
  3. It is obvious, from what has been stated, that the incident and refracted ray will
be always on different sides of the perpendicular.
  4. In  all cases where rays of light pass from one transparent medium to another, a
certain portion of them is reflected at the surface of each new medium.  If, therefore,
light pass through many different media in succession, much of it will be completely
diverted from its original direction by reflexion.
   5. In general, the greater the specific gravity of a body, the greater is its refracting
power.
   6. If a pencil of rays diverging from a luminous point fall directly upon the surface
of a convex lens, they will not all be equally refracted.  The  central ray will pass
through unchanged  in its course.  Those  nearest the centre will  be least refracted;
those most distant from it (which consequently fall with the  greatest obliquity upon
the surface of the refracting medium) will be most refracted.
   7. On the emergence of the rays of light from a bi-convex lens  into air, or any
other medium less dense than the lens itself, each ray will be bent away from  the
perpendicular to the point of emergence.   The effect of this is to cause a converg-
ence of all the emerging rays towards the  central ray; at this point of convergence,
ox focus, an image of  the luminous point  from which the rays originally passed is
formed.
   8. This point of convergence, or focus, varies as to its distance from the surface of
emergence, according to the refracting power of the lens, the amount of curvature of
its surfaces, and the distance of the luminous body.  Its distance constitutes the focal
length or distance of a lens.
   9. In consequence of the  unequal  refraction of rays passing  through a convex
lens, the focus of convergence of the central rays is more distant from the surface of
the lens than that of the peripheral  rays.  Hence the image formed at the focus of
the lens is in some  degree indistinct at  its edges.  The imperfection is due to what
is technically called spherical aberration,-  and it  can  be counteracted only by  inter-
cepting the passage of the circumferential  rays, or by employing such a combination
of lenses  as will establish  a just proportion between the refraction of the central and
peripheral rays.  This aberration is liable to occur in  all forms  of lenses, whether
convex or concave.
   10. White light is compound, and may be analyzed by passing  a beam of sunlight
through a prism. The solar spectrum thus formed on a  surface opposite the prism is
composed of bands  of different colours insensibly passing into each other, which are,
beginning from above, violet, indigo, blue, green, yellow, orange, and red.  Of these
different coloured rays, that which is most bent from the original direction of the solar
beam is the violet,  and the red is the least refracted.  It is owing, therefore, to this
unequal refrangibility of the different kinds of simple  light  that we are enabled to
decompose white light by  its transmission through a prism.
   11. If the different coloured rays which have emerged from  the prism be allowed
to traverse a second similar prism, held  in a reversed position, they will  on their
emergence unite  to form white light again. 
428
INNERVATION.
produced in the rays of light passing through a double convex  lens
explains, to a great degree, the phenomena resulting from the passage (
of the rays through the dioptric media of the eye.
   A ray, falling on the  surface of such a lens, is  bent towards the
perpendicular to the point of incidence, and continues in that  direc-
tion to the opposite surface of the lens.  It then emerges from the
lens, and, in thus  passing from a dense to a rare medium, it is bent
from the perpendicular to the point of emergence.  It can thus be
shown that  the component rays of a pencil diverging  from a point,
will be bent towards the central ray  of the pencil, or that which falls
perpendicular to the convex surface, and be brought to a focus in the
line of the central ray.   And the several pencils of rays, proceeding
from different points of an object, cross  one another in traversing the
lens, so that the foci to  which they are  respectively brought beyond
the lens  are in positions the reverse of those from which they set out,
and the entire image is a reverse of  the object.
   To  apply this to the eye.—If a luminous object,  as the flame of a
candle, be placed eight or ten inches in front of the organ, some rays
fall on the sclerotic and  are reflected; the more  central ones fall on
the cornea: some  are reflected, and others pass through it, are slightly
converged by it, and enter the aqueous  humour, which, being proba-
bly of the same refracting power, does not alter their course.   Pass-
ing onwards, some meet the iris and are absorbed or reflected by it,
whilst others advance through the pupil.   Thus rays, falling on  a
large extent of the cornea, are converged so  as  to  fall on the lens.
By the convexity  of the  surface of the lens, as well as by the greater
density of that body towards its centre,  this convergence is much in-
creased.   Lastly, by their passage into the rarer medium of the vitre-
ous humour, the rays are further converged by the refraction of each
ray from the perpendicular to the point of incidence, and the several
pencils which they form are brought to as many foci in  the retina. And
still further, the rays from the opposite points of the luminous object,
by reason of the change of direction which they undergo through these
successive refractions, cross one another, (the angle of crossing being
called the visual angle,) and thus the image of the flame on the  retina
appears inverted.
  This inversion of the image may be exhibited by a model,  repre-
senting the  transparent media of the eye, with a  retina of ground
glass ; or it may be shown on a recent eye by simply removing the
opaque coats behind the retina, or in the eye of a white rabbit, after
removing the muscles and areolar tissue around it.
  When the retina corresponds,  or  nearly so, to the points of con-
vergence of the several pencils of light, distinct vision of the object
is obtained;  and the  distance  for distinct  vision is ordinarily about

  1.2. The  different refrangibility of the rays of simple light isanother source of indis-
tinctness in images formed by the transmission of light  through lenses with curved
surfaces.  The images are fringed by prismatic colours.  It  is called  technically
chromatic aberration,- and may be corrected by means analogous to those  adopted for
correcting  spherical aberration.  It is obviously of great importance in all optical in-
struments for aiding or increasing the powers of vision that they should as much as
possible be free from these sources of imperfection. 
ADAPTATION TO DISTANCES.
429
ten inches.   If that distance be increased  or diminished (no change
being produced in the eye), vision is indistinct; for when the object
is removed to a greater distance from the eye, it is obvious that the
focus will be moved forwards, or will fall short of the retina ;  and
when the object is approximated, the focus will be moved backwards
or beyond the retina:  in both which cases the same point of the re-
tina will receive rays from several points of the object.  Hence it is,
that when the eye is adapted to distinct vision at a distance of ten
inches, we cannot distinctly see objects at  a greater or less distance.
From the cause of this, which has been  just alluded to, however, it
is  evident that, provided the rays unite very nearly on the retina,
vision, especially of large objects, may prove  sufficiently distinct, al-
though not perfectly clear.  Hence the distinction of Jurin between
distinct and perfect vision is worthy of being  borne  in mind.   Dis-
tinctness of vision will depend on the size of objects, as well as on
their distance from  the eye;  perfection of vision, on their distance
alone.
  This leads to the consideration of  one of the most admirable  pro-
visions for the extended utility of the organ ; viz.,  its capacity  of
adaptation, under the influence of the will, to distinct vision at every
distance beyond that of  a few inches.   We have  the power of  pro-
ducing some change in the eye by which its focal length is modified
to suit the varying angle at which rays from surrounding objects fall
upon it.  Many different explanations have  been attempted of the
mode in  which this adaptation is effected, of which may be mentioned
that of Jurin,  Ramsden, and Home, that the cornea undergoes a change
in its curvature, becoming more convex for near objects: and that  of
Des Cartes, Albinus, Hunter,  and Dr. Young, who considered the
lens muscular, and to possess  within  itself  the power of changing its
curvature.
  Others, again, ascribe  this power of adaptation  to the iris, the  mo-
tions of which might, as Knox supposed, alter the curvature of the
lens; or, according to Sir David Brewster, cause the lens to change
its place, and come forward during contraction of the pupil.   A change
in the  position of the lens has also been supposed to occur from  con-
tractions in the ciliary processes or zonula,  and many have contended
that the entire eyeball may alter its relative dimensions by the action
of its muscles.
  It is conceivable that any of these changes, could they be proved
actually to take place, might  be sufficient to  account for  the effect;
but, in estimating their relative value, the greatest importance is to be
attached to the anatomical evidence by which they may be supported.
In the eye  of the bird, the ciliary muscle, from its position and at-
tachments, must necessarily approximate the lens to the cornea ; and
the reasons for considering the same  part muscular in mammalia, and
if  so, for ascribing to it the same function as  in birds, have been al-
ready  mentioned, and  appear to us  conclusive.   We, therefore, on
anatomical grounds  alone, adopt this view, ably advocated by  Por-
terfield,* conceiving that, when the eye is  intent on near objects, the
* Treatise on the Eye.  Vol. i. p. 446. 
430
INNERVATION.
ciliary muscle is contracted, the lens advanced towards the cornea,
and  the  latter  membrane, perhaps,  rendered more convex by the
traction of the  muscle on  its border  by means of  the cordage of the
posterior elastic lamina ; while in vision of remote objects the lens is
carried back towards the retina by the elasticity of the  neighbouring
parts.  It is interesting to notice that this adjusting faculty of the eye
is greatly impaired or altogether lost by extraction of the lens, or by
paralyzing the  ciliary and iridial  muscles  by belladonna.   Dr. Clay
Wallace considers that the ciliary muscle  advances the lens by com-
pressing  the veins, and  thus  causing an erection  or lengthening, of
the ciliary processes.
  It has  long been observed that the pupil is very prone to contract
during near vision, and to dilate when the organ  is  adapted to view
remote objects; and it has been imagined that this change is the ne-
cessary condition of  adaptation, and  may affect the lens through the
ciliary body.  In some persons, however, not at all deficient in the
adjusting power, the iris continues to oscillate for some time after the
eye is adjusted, without disturbing vision; and we have occasionally
found the pupil to remain  dilated, though a near object is being gazed
at and the illumination remains  the  same.   Moreover, the action of
light on  the pupil has no effect on the adjustment of the  eye, since
we  can continue to see an object distinctly, whether it be viewed by
a strong or by a feeble light.
  These facts are sufficient to prove that  the movements in the iris,
usually coincident with the act of adjustment, are not the cause of that
act.   They seem rather to be of the nature of associate movements,
produced by the close connection of the iris with  the ciliary muscle,
and  by the community of  source from which both  these  derive  their
motor nerves, viz., from the third pair, through the  ophthalmic  gan-
glion.   And it is an important  circumstance, that certain consensual
movements of the eyeballs, performed through the medium of the third
pair, are likewise associated with the act of adjustment.  The move-
ments of the iris chiefly minister  to  another  function, the  regulation
of the quantity of admitted light.
  The contraction  of the pupil  during near vision, by obstructing
more of  the circumferential rays, answers the important purpose of
correcting the excessive aberration  of sphericity  which results from
the greater divergence of the rays entering the eye from near objects.
  Some  persons have the power of adjusting the eye to distinct vision
at different  distances, either  to a very limited extent  or  not at all;
and we observe two states of vision connected with this defect, which
are  generally dependent on certain physical conditions of the lenses of
the  eye:  these are shortsightedness, or myopia; and longsightedness,
or presbyopia.
  Myopia.—Thus, we meet with many persons who cannot distinctly
see a yard before them,—who  fail to recognize the features of their
acquaintances in  the street.   In reading, they are  obliged  to bring
the book close  to their eyes: in looking at  an object at all distant,
they exhibit a characteristic winking (fxvo, connivo).  Myopia occurs
in adolescence, and is accompanied with a too great refracting power 
OFFICE OF THE IRIS.
431
of the media, so that the image is formed anterior to the retina.  In
order, therefore, to throw back the image on the retina, the object is
brought very close to the eye ; or the convergence of the rays of light
may be diminished by the use of a concave lens.
   It seems probable that the state of myopia may be acquired by the
habit of looking intently at small and near objects, and that the com-
mon practice of remedying the inconvenience by the use of concave
glasses tends to increase the defect.  Frequent exercise of the eyes on
remote objects has, no doubt, the effect of making them far-sighted.
It is a common error to say that myopia disappears naturally in  ad-
vanced life.
   Presbyopia.—Others  again  imperfectly distinguish  near objects,
whilst they see distant  ones very plainly, and the distance at which
they can see distinctly is sometimes very great.  Persons thus affected
cannot  read  small print with  the eyes unassisted, and they prefer
holding the book at a distance.  This condition of vision is  connected
with a too flat cornea, a deficient  aqueous humour, or  a  flattening of
the lens:  and  it is in a great degree accounted for by the diminution
in the refracting power thence  resulting, so that the focus is behind
the retina.  It belongs to the  advanced  periods  of life.   It may be
corrected  by convex glasses, which increase the  convergence of the
rays of  light.
   It is manifest that neither of these defects is dependent on the mus-
cular apparatus of adjustment, but rather on the curves of the refract-
ing media, which throw the organ in one direction or the other beyond
the range  of the adjusting power with which it is  provided.  VVhen
the refracting media are optically corrected, as by the use of glasses,
the adjusting faculty can be exercised.
   In the eye, considered as an optical  instrument, there  are  other
powers besides those  already named, which  serve to  make it more
perfect, and to place it in favourable  contrast with the most success-
ful creations of human ingenuity.
   One important office of the iris is to prevent the  passage of rays
through the circumferential part of the lens, and thus to  obviate that
indistinctness of vision which would  arise from spherical aberration,
or that  unequal refraction which results  from  the difference in the
angle of incidence of the several rays on a curved surface.  In this
respect it  resembles the diaphragms used in optical instruments.  By
its position, close to the surface  of the principal lens,—and behind or
within the first one by which the light is converged, viz., the concavo-
convex one formed by the cornea and aqueous humour,—it  is adapted
to admit the  greatest quantity of light to the lens, consistently with
the correction  of the spherical aberration.
   The aberration of sphericity is further obviated by the  increased
density of the lens from its surface  towards  its centre, so that the
rays falling  on its middle region are made more convergent as they
traverse it, than those passing near its border.
   Chromatic aberration, or that which occasions a coloured image by
the inequality of the  refraction  of the  elementary colours  of  white 
432
INNERVATION.
light by the same medium, is in some way prevented in  the  human
eye, when  adjusted to distinct vision.
  The image formed by a convex lens is slightly coloured at its mar-
gin.  This  colouring is corrected in practice by a compound arrange-
ment of lenses differing in shape and density, of which the second,
while it continues the convergence of the rays from  their original
course, re-associates the dispersed  colours and recomposes the white
light.
  The achromatism of the eye may be in part  due to the  diversity of
shape and density of the refractive media, which seem to bear some
analogy to  the system  forming the achromatic pbject-glass of  Her-
schel.  This is formed of a double convex lens of crown-glass, with
surfaces of unequal curvature, the  more convex being turned towards
the object;  and of a concavo-convex of flint-glass, the concave side
of which receives the lens of crown-glass, while  its convex  side is
towards the eye.  The cornea and aqueous humour form a concavo-
convex lens which differs in density from the crystalline.
  It is possible that the greater density of the  inner fibres of the lens
may likewise share in producing the effect.  But this entire  subject
is involved in much obscurity, and it is right to add that some very
high authorities, including Sir D. Brewster, deny that the chromatic
aberration receives any correction  in the eye ; that,  in fact, it exists
in all cases, and is imperceptible only in consequence of  its being so
slight.  It  may be observed that when the eye is not adjusted to dis-
tinct vision, a coloured fringe is seen around objects.  If the eye be
fatigued and incapable of adjustment, or if belladonna be used, then
colours are seen.
  The rays of  light which have now been traced to the retina, al-
though they come to a  focus in  that  membrane, yet  can scarcely,
from  its extremely thin  and transparent  nature, be   said to form an
image upon it.  The image, however, which becomes visible in the
experiment on a dead eye, though  partly due  to the  opacity the re-
tina acquires soon after death, is yet an evidence that this membrane
does not give passage to the light, like transparent  glass, or the hu-
mours, but rather like ground glass, dispersing and  reflecting some
portion, as  indeed  its peculiar texture  must dispose it to do.  The
pink colour of the pupil in albinos shows the reflection that occurs in
those cases from the vascular choroid and retina; and Mr. dimming
has recently pointed out that in the eyes of  all persons, where the
pupil is tolerably large, a  very decided reflection from  the bottom of
the eye may be observed under favourable circumstances.  To make
it apparent he places the individual at a  distance of ten  feet  from a
single gas-light or lamp, and directing him to look a little on one side,
a strong glare becomes visible to any one standing almost directly be-
tween him  and the light.   In some persons this glare is exceedingly
brilliant, like that from burnished brass; in others it is fainter.   This
reflection can hardly be regarded as important in a physiological point
of view.  It probably proceeds from the hyaloid membrane, the retina,
and from the choroid also, but from the latter more or less according
to the amount  of pigment present  in the  particular  instance.  It is 
EXCITABILITY OF THE RETINA.
433
remarkable that these  reflections do not inteffere with the perfection
of the sense,  do not derange the integrity of the impression resulting
from the first passage of the rays.  Corresponding but more vivid re-
flections from the tapetum lucidum in certain  animals serve a useful
purpose, by giving an additional stimulus to the retina, where but  a
feeble light is admitted to the organ.
   Excitability of the retina, and of the allied  nervous parts.—When
the retina is stimulated,  we have the sensation of light, whatever
may be the nature of the stimulus applied.  Pressure, for instance,
made on the  side of the eye in  the dark, gives rise to the sensation
of a spot of light, the situation and size* of which will  be  determined
by those of the point of the retina touched.   The same is true of the
optic nerve, and of certain parts  of the  encephalon with which the
nerve is connected. The sensation of light, then, consists in a recog-
nition by the mind  of a certain condition or affection of these nervous
parts, and this condition may be induced  by the application of any of
the ordinary stimuli of nerves.   The retina, however, is capable of
being affected in this way by the luminous rays;  and perhaps this
capacity is dependent on the peculiar manner in which the nervous
matter  is spread out  in this part.   However that  may be, the  light
incident on the retina  is the only stimulus which can naturally affect
it; and the other parts, endowed with the same kind of excitability,
can, in  the  natural state,  be stimulated only in a secondary manner,
as though by induction through  the retina.  It  is  certain that the
integrity of these other parts is essential to vision, and it  may there-
fore be  concluded that during  vision they  are all, immediately or
mediately, in a state of excitation.
   The retina is not affected sufficiently for the purposes of vision by
a very faint light;  and, on the other hand, a very strong  light, espe-
cially if long applied, will produce effects analogous to those resulting
from an inordinate  stimulus to other organs: the blood-vessels of the
retina will become  unduly injected, its nutrition disordered, and even
its texture destroyed.   But the  retina exhibits a considerable power
of accommodation to different amounts of light, and  thereby the utility
of the organ  is much  enhanced, as well as its safety provided for.
After a  short stay in the dark, objects  disclose themselves, which at
first were imperceptible; and, on  the other hand, a light which was
at first  too bright, becomes agreeable by use.   This  adaptability is
quite independent  of the iris, and  has its analogue in the case of
every nerve of sense.
   The  iris,  however, by  its contractile power, is a most important
agent in protecting the retina from the effects of sudden transitions
from dark to light; and in thus co-operating for  the maintenance of
its most essential quality, excitability, the  iris is seconded  by the eye-
lids and brows.   The iris contracts under a strong light, by virtue of
the stimulus imparted to the  retina;  for if  this or the optic  nerve be
destroyed or paralyzed, as in amaurosis, the iris no longer contracts.
It  is interesting, however, to notice that  the iris  of the unsound eye
will often contract in company  with  its fellow, when the opposite
sound retina is stimulated.   The motion is therefore evidently caused 
434
INNERVATION.
by a reflexion of the stimulus from the optic nerve, through the nerv-
ous centre along the inferior branch of the third pair to the iris, and
the consensual action of the  two sides  is effected in the nervous
centre.   Mechanical irritation  of the ciliary nerves,  or  third pair,
occasions contraction of the pupil on the  same side.   The orbicularis
palpebrarum  and corrugator supercilii likewise contract under a pow-
erful glare, in obedience  to  a stimulus  reflected  through the optic
nerve,  and quite independently of the will.   This is well exemplified
in children affected with  strumous ophthalmia, in whom  the excita-
bility of the retina is highly exalted.
  The pigmentum nigrum is a permanent shield to the retina, absorb-
ing the light which falls  upon it, and remaining the same under all
degrees of illumination.   The excitability of the  retina in creatures
usually exposed to the full light of day, requires this additional protec-
tion ; and where it is deficient, as in albinos, an ordinary light becomes
painful, and the movable protecting parts are habitually brought into
increased use.  In  animals of nocturnal habits, furnished with a tape-
tum  lucidum, the  excitability  of the retina  is probably somewhat
modified, and the  iris also is generally  larger,  and capable  of an
ampler range  of motion.
  Duration  of impressions on the  retina.—We continue to see an
object  after the rays of light emerging  from  it have ceased to fall upon
the retina, and this for  a  period proportioned  to the  intensity and
duration  of the impression they have  left.   The familiar experiment
of twirling a lighted stick, so as to see a luminous circle, shows that
the impression made by it, when  at any one point of space, remains
on the  retina  until it reaches  that point again.  By ascertaining the
speed necessary for completing a  luminous circle of a certain size we
can estimate  the duration of the impression; and by augmenting or
diminishing the brilliancy of the ignited  point its duration is  found
to be affected.  A momentary impression  of moderate intensity con-
tinues  for a fraction (according to D'Arcy, about an eighth part) of a
second.  But if the impression  be made for a considerable time on
any one  point of the  retina,  it endures for a longer  period  after the
object  is removed.  It is owing to this retentive power of the retina,
that the rapid and involuntary act of  winking does not interfere with
continuous vision of surrounding objects.
  Appearances of objects remaining after the removal of the objects
themselves from the field  of vision,  come under the head of ocular
spectra.  In figure they correspond to  the image the object has thrown
on the  retina,  but they are of the  complementary colour to that  of the
object.   Thus, the  spectrum  left  by a red spot is  green;  by a violet
spot, yellow; by a blue spot, orange;  and these colours of the spectra
are particularly obvious when  the  eye is  directed towards a  white
ground.  It is further remarkable, that after long gazing on a very
bright  light,  as the  sun's disc, the remaining spectrum, if viewed on
a white  surface, assumes  the  different colours in succession, from
black,  through blue, green, and  yellow,  lo  white:  if viewed on  a
black surface, the order of the succession is reversed.  These several
phenomena can only be referred to particular states or modes of exci- 
          OCULAR SPECTRA.—LUMINOUS IMPRESSIONS.         435

tation of the retina, by means of which alone it is that the differences
of the component  colours of white light are made evident to our per-
ceptive powers.
   It appears by a  simple experiment, for  the principle  of which we
are indebted  to Mariotte, that the small  portion  of the retina corre-
sponding to the entrance of the optic nerve,  is incapable of exciting
visual sensation though it receive the image of an object.   Place the
thumbs together at arm's length, shut the left eye and fix  the right
eye steadily on the left thumb ; then  the right thumb, if moved gradu-
ally outwards (so  that  its  image on the retina of course  traverses
inwards), ceases to be visible in a particular spot, but is again seen
beyond it.  It will be remembered that the fibrous lamina of the gray
nervous layer of the retina is here evolving itself from the nerve, and
is not yet invested with the vesicular or other lamina; a  circumstance
of great interest in regard  to  the modus  operandi of the constituents
of the retina in vision.
  It has indeed been denied by an eminent  physiologist, that the
retina is insensible to light at this point, on the ground that, if  such
were the case, we should see a dark spot in our field of view when-
ever we use only one eye.   To produce the  physical sensation of
darkness, however, the  retina seems as  necessary  as the nerves of
ordinary feeling are to the production of the  physical sensation of
cold.  Both  sensations are occasioned by the absence of the respective
stimulus, but the specially  endowed nerve is  as essential to acquaint
us with  the  absence as with  the presence of  the  stimulus.  What
Mariotte's experiment proves is simply that over that spot no nervous
matter, having the peculiar power of excitability by light, exists; and
as far as the faculty of seeing with  that  spot  is  concerned, it  is  as
though the piece of retina  had been punched out.  We no more see
a dark  spot corresponding to it, when we look  with  one eye, than
we see everything dark behind us—where there is no nervous expan-
sion  visually endowed.   For, in  strict language, a distinction  must
be drawn between the sensation  of darkness  and the absence of the
sensation of light.
  This incapacity  of vision at the entrance of the optic nerve, seems
to be essential to the mode of junction of the retina with the nerve,
since it  appears to  have been the  chief reason why the nerve was not
made to enter in the axis  of  the eye.  If the  blind spot had  been
situated in the axis, a blank space would have  always existed in the
centre of the field of vision, since the axes of the eyes,  in vision, are
made to correspond.  But, as it is, the blind spots do not correspond
when the eyes are  directed to the same object;  and hence the blank,
which one eye would present, is filled up by the opposite one.
  Though no other part of the retina is insusceptible  of luminous
impressions, yet there is  good reason to suppose that the hinder part
of it is  much  more capable of appreciating them  than  the  anterior.
WThen  using one eye only, we naturally direct  it  towards the object
we wish to inspect, and  in that way throw the image to the bottom
of the globe.  When the eye is thus  fixed, objects near the boundary
of the field  of vision are less  distinctly seen than those at its centre. 
436
INNERVATION.
The posterior  part  of the retina, too, is  the  best adapted to receive
correct images through the dioptric media, and we find its gray nerv-
ous layer becoming thinner and thinner towards  its anterior border.
  It is probable that the most anterior part of the retina is never used
in vision,  since  it can scarcely receive rays directly from the  lens.
Dr. Young, by fixing the eye in  the  most natural direction, viz., for-
wards and a little downwards, and by then moving before it a luminous
object, in various directions until it passed beyond the range of vision,
ascertained the range upwards to be  50°; downwards, 70°; inwards,
60°; and  outwards, 90°:  the extent in each direction being limited
by the  contiguous parts of the face.   An object, therefore, occupying
only an angle  of 120°, both in the vertical and  horizontal direction,
and suitably placed, would about fill the field of vision  of a single
eye, when the organ was fixed as above described.  Now, it may  be
proved that no part of the image of  such an  object would fall on the
anterior part of  the retina.
  Perhaps it  is only in, or very near, the  axis  of vision, that  sight
can be said to be perfect.   The existence of  the yellow spot of Soetn-
merring at  that point continues  a  riddle which the  most attentive
examination of its anatomy has not yet solved. And from  the absence
of  this spot in almost all  the  lower animals, we are led to doubt  its
importance  to perfect vision.
  To the perfect exercise of vision, as of  all  the other senses,  an
effort of attention is  necessary; and this effort  is naturally accompanied
with a  motion  of the eyeball towards the object, so that  the image
may be thrown  upon the  central part of the retina.   The range  of
motion of the eyeball Dr. Young calculated at 55° in every direction ;
so that, the head being fixed, a single eye may have perfect vision  of
any point within a range of 110°.   This field is further widened  by
the use of the opposite organ, but beyond this an  increased range is
only to be acquired by movements of the entire  head.
  The internal, or gray nervous layer  of the retina seems to be the
essential part on which the power of the retina in the process of vision
depends.   That layer is an  unbroken sheet,  continuous by its fibrous
internal surface with the axes  of the tubules of the optic nerve, and
having its external surface formed by a structure similar to that of the
cineritious substance of the cerebral hemispheres.   Its permeation  by
a close network of capillaries assimilates it  still further  to the gray
nervous matter; for which reasons it may be considered as a  portion
of  the cerebrum advanced  towards the surface of the  body into a
suitable relation to a dioptric apparatus  for  the reception of  rays of
light from external objects.  The optic  nerve  may be regarded as a
commissure between the gray nervous sheet  within the sclerotic, and
the gray nervous matter of certain parts of the cerebrum.   We  have
no  more  reason to  deny the immediate connection  of  the sensorium
with the retina, than its immediate connection with any small  portion
of  the cerebral  convolutions, duly united with the rest.  The nature
of  the connections  between the retina and  the  brain, and the  phe-
nomena to which their disruption gives rise, have  been the occasion
of  many interesting speculations regarding  the  mode  in  which the 
          CORRECT VISION WITH AN INVERTED IMAGE.         437

mind is reached, or, in other words, as to how an impression on the
retina  becomes a sensation  to the  mind.   But we shall probably be
disappointed  if we imagine that any facts which have been or may
be hereafter ascertained, are capable of leading to the solution of a
problem too inscrutable for our limited powers.
  It is a matter of considerable interest, as regards the mode of action
of the retina in vision, to determine how distant the images of two
points  on the retina must be, to be seen distinctly as two; in  other
words, how small a portion  of the  retina is capable of independent
sensation.  As the result of many experiments and  calculations by
Smith, Harris, and others, this may be stated as probably about TqW
of an inch, so that the objects must subtend  an angle of at  least 40".
Two points within an angle of that size would appear as one.   It is
a question somewhat different, what is the smallest portion  of the
retina capable of sensation; and undoubtedly an object whose sides
subtend  an angle very  much smaller than the preceding may be
visible, if sufficiently bright.   But this circumstance  of quantity of
light introduces a difficulty into the inquiry,  since even a mathemati-
cal  point, if  sufficiently brilliant  and out  of focus, might become
visible by its circle of aberration on the retina;  although,  if its rays
met in the retina, it would be invisible.  But, in carrying our  specu-
lations thus far, w7e must cease to regard the retina as a mathematical
plane, and  remember  that  it has  a certain thickness, in  traversing
which the rays would necessarily cover more than a point, either in
front of or behind the exact focus.  It is obvious that a linear object
would be more perceptible than  a point, and  a  moving object more
so than a stationary one, in consequence of wider and more distant
portions of the retina being affected in both  cases.
  The apparent truthfulness of a view, recently  put forward on high
authority in Germany, and copied into several  works in this country,
makes it necessary to explain here that the rod-like particles of Jacob's
membrane, though corresponding nearly in size with the points of the
retina capable of independent sensation, yet being on the choroidal
surface, and separated from  the gray nervous layer by the intervening
granules, can  scarcely have a share in determining  the  size  of the
independent visual points.  The unfortunate  error which placed these
rods as papillae on the hyaloid surface of the retina, was too tempting
a ground  of theory not to be readily admitted  as true, without scru-
pulous examination; and the price fo be paid  will probably be some
degree of discredit thrown on minute anatomical research.
  Correct Vision with an inverted Image.— Visual idea of Direction.—
The image on the retina  being the reverse of the picture of external
objects seen by the mind, it is manifest that in some way or other the
inversion is counteracted ere the impression  becomes a sensation.  It
is conceivable that this correction may take  place in the optic nerve
or brain, but it is far more probable that  it occurs in the  retina.   It
is certain that we do not see the  image as  it exists on the retina,  or
its inversion would not have remained so long unknown ;  we rather
see out of or from  the retina.  The simple experiment  of pressing
with  the  finger on  the  retina through the ocular tunics, and thus 
438
INNERVATION.
eliciting a luminous appearance on the opposite side, seems to prove
that the apparent projection of a luminosity in  a direction  perpen-
dicular to the point stimulated, is a necessary part of the excitability
of the retina.  If this be granted as an ultimate fact, it will explain
why an  inverted image, formed on a concave retina, shows objects
in the  same position as they are  shown by the other senses which
receive direct impressions from them,  particularly touch.
   It  has been  supposed by Muller  and Volkmann, that objects do
really appear inverted; but they argue that, as long as all do so, even
visible  parts of our own bodies, there  is no need of a correction.  But
this will not explain the perfect harmony existing between  impres-
sions conveyed through the senses  of hearing  and touch, with those
derived from sight.  Sounds are appreciated, and tactile impressions
are felt, as proceeding from  a particular direction as regards the body
—our several organs are conceived  as existing in a particular relative
position, altogether independently  of vision—and  vision  accords
entirely, and at once, with these senses  in  the determination of
locality, without the necessity of an education of the sense, such as
a reversed impression on the mind  through the eye would require.
   Were the eye and  the whole body fixed, we  should still have a
knowledge  of the relative position of visible  objects, and of course of
the direction in  which each point of  their surface was placed, as re-
gards the organ of sense; and as rays coming  from objects in the same
direction as regards the body, would then  always fall  on  the same
part of the retina, we might conclude that each part of that membrane
had the power of  conveying the notion of position  in  one  direction
only as regards the body.   But the  eye being a very movable organ,
we are  enabled to make the image  of a  stationary object travel  suc-
cessively over a large tract of the retina without the object appearing
to move; since we are conscious, through the muscular sense, of the
motion  in our own eye.  The visual idea  of direction in regard to the
body, therefore,  does not depend on the  image falling on a particular
point of the retina, but in a great measure on the muscular sense, in
conjunction  with that quality of the excitability of the retina already
spoken of.
   It is proper also to mention that  the limits of the field of vision,
formed  by certain parts of the face,  are a standard to which the mind
refers in estimating the position of visible objects. The outline of the
field  remains the same, through all   movements of the eye.  The
motions of  the  head or body can  alone bring new  objects into  the
field; and the muscular sense thus still further contributes to enhance
the usefulness of the sense of vision.
   Visual Perception of Shape and Size.—If an object form a large
image on the retina, and of a square figure, we conceive it at once
to be large and square; and of this no  other explanation can be given
than that the visual points making up the surface  of the retina have,
as regards space, a relation to one another, of which the mind is in-
tuitively cognizant in framing its ideas from visual impressions.  But
the size of  an image, relatively to the whole retina, will vary with
the distance of the object; and the conception  of its real dimensions 
DOUBLENESS OF THE ORGAN OF VISION.
439
would be erroneous, were it not that the impression were corrected
by the muscular sense engaged in the  adjustment of the eye to dis-
tance, and by the lessons  of experience.  When a person, blind  by
cataract from infancy, is couched, he concludes that the diversified
details of the scene presented to him  are at an uniform distance, as
in a picture: and  a species of education can  alone undeceive him.
He learns, through  touch, that all objects are not equally near to him,
and  gradually familiarizes himself with the changes in their apparent
size, distinctness and colours, produced by the movements of his
whole body with regard to them.  The adjusting faculty is an addi-
tional source of correct knowledge.
   Visual Perception of Motion in Objects.—When an object moves
in a direct line, to or from the eye, its  motion  is inferred chiefly  by
the change effected in the size of its image on the retina, as when a
locomotive  engine, at full speed, approaches the observer.  When
the object moves in an arc, of which  the eye  is the centre, its mo-
tion is known, if the eye be  fixed, simply by the movement  of  its
image across the retina.   But most motions occurring around us are
known in both these ways.  When, too, the  attention is excited  to
the  moving  object, the eye is naturally moved in concert  with  it,
in order to keep its image near  the axis of the organ where vision
is most perfect.  Our  appreciation of  the  direction and velocity of
the motion is thus heightened  by  the exercise of the muscular sense.
   Doubleness of the Organ of Vision.—The preceding  account has
been almost confined to the phenomena of vision with a single  eye;
it remains to be explained how the doubleness of the organ affects the
sense.
   In some animals the eyes are so placed as to  look in  different di-
rections, and in these  the images formed are,  doubtless, independ-
ently recognized by the  animal, just as are those thrown on different
parts of the retina of a single  eye in ourselves.   But where the eyes
are both directed the same way, it is manifest that a double  image of
each object must be received, and that  the singleness of the result-
ing sensation must depend either on our noticing  only one of these
images, or else on our forming a single conception from both conjoint-
ly.   It is easy to prove that  the latter is generally the case,  although
we sometimes derive our information from  the  affection of  only one
eye.
   The eyes are moved in  concert by the muscles  attached to them,
so that their axes always converge towards the  object to which  they
are adjusted.  The  consequence  of this is, that  the corresponding
points of the  two images are made to occupy corresponding  points of
the two retinae, or very nearly  so, and single vision is produced.  If
the two images are unsymmetrically placed on  the retinae, as where
the optic axes do not converge to the object, a double  sensation  is
excited.   Thus, in squinting, two impressions are excited, unless, by
long habit, one eye ceases to  be adjusted and employed, and gradually
loses its excitability: but when two similar objects are presented  to
the eyes of a squinting person, one carefully in the axis of each,  their
images coincide and they are seen as  one.  The double vision  of 
440
INNERVATION.
drunkenness, and of certain cerebral affections, is explicable partly on
the same ground, but in such cases considerable  allowance  must be
made for the disordered state of the sensorium.  Again, if correspond-
ing points of the two retinae are pressed by the finger, a single lumi-
nosity is perceived-, but a double one, if the points touched are non-
symmetrical.  Something similar  to this blending of two impressions
in one sensation exists in the sense of hearing, and, perhaps, also in
taste and smell.
   The corresponding points of the two retinae are such  as would  be
in contact, if the. two retinae were adapted to one  another: the upper
and lower parts correspond with the upper and lower, and the inner
side of one with the outer side of the other.
   As we are entirely ignorant of  the mode in which  the mind takes
cognizance of a single  impression on  an organ of sense,  we cannot
hope to understand how a single  sensation can result from a  double
impression.   But it is most  interesting to remark  a structural pecu-
liarity  in the course of the optic nerves, which certainly allies itself
with this wonderful part of their function.  Their partial decussation
in the  chiasma, or commissure, connects each retina with  both optic
tracts, and with the corresponding portions of  the cerebrum ; and it
is not  improbable, as Dr. Wollaston  conceived, and  Mr.  Mayo  has
described, that the right side of both retinae  is continuous with  the
right optic tract, and the left side of both with the left.  This would
place each side of the central apparatus  in connection with  its own
side of both the symmetrical images, and might be supposed to favor
their conception as one.  Dr. Wollaston relates,  that on different oc-
casions he lost the power of seeing one half of an object to which  he
directed both eyes; and  others have  experienced  similar  temporary
attacks.   Thus, Abernethy would humorously affirm  that he could
sometimes see only his ne and thy, having lost the other members of
his name.   Such phenomena are  readily explained by supposing the
anatomical arrangement of the sides of the retina?, with regard to the
optic tracts, to be such as above described, since any derangement of
one optic  tract would then affect the same part of both optic images.
Indeed, in Dr. Wollaston's own case, a tumour was found involving
one of the optic tracts, as had himself inferred from the phenomenon
above mentioned.
   What we have before advanced, however, regarding the unbroken
sheet of gray nervous matter in the  retina, leads  us  to attach even
more importance to the commissural fibres which  appear  to connect
the two retinae together, through  the  medium of the chiasma, and
independently of parts behind  it.  Wre conceive that these commis-
sural fibres may connect  corresponding parts of  the  retina, much in
the same way as corresponding parts of  the cerebral  convolutions of
the opposite  hemispheres are linked together by the corpus callosum
or other commissures; and  that  the  unity of action of the double
organ  may depend, as to its physical cause, on the same principle in
both.
   This capacity of forming a single conception from a double impres-
sion may  appear, at  first sight, to be given simply to obviate con- 
SINGLE VISION WITH A DOUBLE ORGAN.
441
fusion ; but Mr. WTheatstone has most ingeniously shown that it con-
fers a new power on the sense, viz.,  that of appreciating forms pro-
jected in relief.
   Such  objects, if  sufficiently near the eyes for the optic axes  to
converge in  viewing  them, are seen from  two different directions:
they are represented  on each  retina by a different perspective pro-
jection;  and the more so, the  nearer the object to the observer.
   Mr. Wheatstone  has  shown  that the  single sensation excited by
these two images is that of a  third image different from them both,
but  excitable only by both of them at  once, and attended with the
notion of solidity, or projection in  relief.  He has illustrated this by
an instrument which he terms the stereoscope.  Some object of three
dimensions (as a cube) is represented  in two drawings as it would be
seen at a small  distance by each of the two eyes.   These drawings
are then placed symmetrically in the right and left compartments of a
small box, so as to  be reflected by sloping mirrors to the eyes of the
observer, each  view  to its corresponding  eye.   When he looks at
each separately, it seems a mere drawing on a flat surface; but when
he regards both  views at once, they appear  to coalesce, and a solid
prominent figure seems  to occupy their place.   Mr. Wheatstone has
also shown  that  the  same effect  occurs, although  there  may exist
some  disparity between the  size  of  the  two images;  and that  the
resultant idea is that of  a figure of intermediate size.   Now, unless
an object is placed  directly in front of the eyes, its image is larger in
one  eye than  the other,  because it is nearer one eye than the other;
and  this faculty of striking a  mean between the two impressions is,
therefore, constantly made use of.
   The above facts  abundantly prove the  non-existence of absolutely
corresponding points on  the two retinae, such as were formerly held
to exist.  But they  do not invalidate  what has before been advanced
respecting the  general  correspondence  of  certain tracts of the  two
retinae, and the  absolute non-correspondence of others.
   Mr. Wlieatstone further observes, that if two dissimilar images are
represented  at  once  to the  corresponding  parts of the two retinae,
they are not blended, but seen alternately, according  to  their  dis-
tinctness  and degree of illumination.  This is  a very singular cir-
cumstance, and agrees closely with what takes place when dissimilar
colours are viewed  in the same way.

  On the subjects treated of in this chapter, reference is made to the following works :
Zinn, Descriptio Anatomica Oculi Humani; Haller, Elementa Physiologic, torn, v.;
Porterfield on the Eye and Vision (an admirable work) ; Dr. Jacob's paper on the Phil.
Trans. 1819, and in the 12th vol. Med. Chir. Trans., and the article "Eye" in the
Cyclop. Anat. and Phys., by the same author; Mr. Dalrymple's Anatomy of the Eye,
London, 1834; the introduction to Mr. Lawrence's Treatise on Diseases of the Eye,
2d Edit., 1841; Mr. Wharton  Jones' Essay prefixed to MacKenzie on Diseases of the
Eye; Arnold, ilber das Auge  des Menschen; Socmmerring's Plates of the Eye; Miil-
ler's  and Wagner's Physiology; Mackenzie on Vision; Bowman (W.) Illustrations
of the Anatomy of the Eye in health and disease, now in course of publication.
     29 
442
INNERVATION.
                        CHAPTER XVIII.

OF HEARING.--THE  ORGAN OF HEARING.--ITS  DEVELOPMENT IN  THE
  ANIMAL  SERIES.--THE  EXTERNAL  EAR.--THE  TYMPANUM.--THE
  LABYRINTH.—THE FUNCTIONS OF THESE PARTS.

  It  is by the sense of hearing that  the mind takes cognizance of
those oscillations of elastic matter which give rise to the phenomena
of sound.
  The communication  of these oscillations  to the ear may  take place
through the air, or through the intervention of some solid conductor,
brought into immediate connection with the organ of hearing.
  The essential part of the organ of hearing is a sac, containing fluid,
upon which the nerve  of hearing is freely distributed: this sac being
in connection with the cranial parietes.   This is represented in the
human subject by that  small cavity which is excavated in the petrous
portion of the temporal bone, called  the vestibule.   This, and  three
semi-circular canals, with a spirally disposed canal, divided by a  par-
tition, constituting the cochlea, form the labyrinth.   External to this,
and  situate between the squamous and petrous portions of the tempo-
ral bones is a cavity, the tympanum, which  in front further communi-
cates very freely  with  the  cavity  of the  throat  through  an  open
channel, the Eustachian tube, whereby air has a  free access into the
tympanum.  This cavity is  closed on  the outside  by a  membrane
(membrana tympani) which  extends over its external orifice as over
a drum.   A communication is established between  the  membrane
and  the inner wall of the tympanum, by a chain of small bones which
extends from the one to the other.   These  are the ossicles  of the ear.
The outer bone of the  chain is intimately attached to the  membrana
tympani, and the inner one to a membrane which closes the vestibule
on  the outside.   The three  bones  which compose the  chain are
articulated by moveable joints, and  are moved  by small  muscles,
which are thus enabled to regulate the tension of the membrana tym-
pani, as well as of the membrane of the  vestibule.   Externally is an
apparatus  for  collecting  sounds, and  conducting them  to the  tym-
panum.
  Development of the Organ of Hearing in the Animal Series.—There is no organ in
the body in which we find a more remarkable gradation of development in the various
classes of animals, than in the ear.  We see it existing as a simple sac  in the cepha-
lopod and gasteropod mollusks, and in Crustacea.  In the cuttle-fish, it consists of a
small sac filled with  fluid, lodged in  a  chamber excavated in the cranial cartilage.
The chamber is  closed everywhere except at the entrance of the auditory nerve,
which passes  in to expand upon the  sac.  From  its  inner surface  there project
several obtuse processes, of a soft, elastic nature, which support the sac. The sac
contains a calcareous body or otolithe.   Even  at this early stage of development the
organ is double, and  the two cavities are separated  from each other by a very thin
reptum. It is obvious that  these cavities are strictly analogous to the vestibule in
the higher classes.
  In Gasteropoda, the organ consists of a sac, to which the nerve is distributed, and 
ORGAN  OF HEARING IN THE  ANIMAL  SERIES.         443
which contains fluid and several small otolithes, which, according to Siebold, exhibit
remarkable movements.
  In Crustacea, the organ still exists as a simple sac.  This, as Dr. Arthur Farre has
shown, is situate, in the  lobster, in  the base or  first joint of the lesser antenna.  Its
place is indicated  by a tough membrane which  covers an oval aperture in the upper
surface of this joint; the membrane  being a continuation of the same structure which
forme the shell, but in which the earthy matter  is  wanting.  Towards the inner and
anterior margin of this membrane,  there is a small round aperture, through which  a
bristle may be passed.   "On removing this oval membrane, together with a portion
of the surrounding shell, the internal organ is brought into view, completely imbedded
in the soft integument and muscular structure of the antenna."  It consists of a sac,
in shape like an auricle, and of a horny structure, like soft quill, suspended in the
centre of the joint, free on all sides, and having  only a single attachment near the
aperture  in the oval membrane already described; it nearly fills  the cavity of the
joint.  The sac contains particles  of siliceous sand, which  find  their  way into  it
through the aperture already described, and probably fulfil the office of the otolithes
which exist in other classes of animals.   Numerous very remarkable ciliated pro-
cesses are attached to the lower surface of the vestibular sac: they are arranged in a
semicircular line.  In  the neighbourhood  of this line the auditory nerve attaches
itself to  the sac, and forms a plexus, which covers the whole under surface of the
sac, extending also towards its upper surface.  The nerve is derived from the lesser
and greater antennal nerves.
  Dr. A. Farre has shown that the cavity situate at the base of the greater antenna
is not, as has been hitherto supposed, suited to act as an organ of hearing.  It is a
conical papilla, abruptly truncated, and having  stretched over it a membrane, which
is pierced in  its centre  by an aperture capable of admitting a small bristle.  On
making a  section of this part, nothing more  is  seen than  a narrow canal in the
fleshy substance leading  perpendicularly from  the external orifices, and terminating
abruptly  at the depth of two lines.   A nerve is sent off to this organ from the supra-
oesophageal ganglion.   Such  an organ is  very ill-adapted  for hearing.  Dr. Farre
has  ascertained that this is the most sensitive  part of the  body of  the  lobster;
"since, while the mechanical irritation  of any  other parts  excited only a  slight
movement in the limbs of the animal, when out of water, and somewhat feeble, the
touching of this part was  immediately followed by a violent and almost spasmodic
flapping  of the tail."  {Farre on the Organ of  Hearing in Crustacea.  Phil. Tr. for
1843, p. 233.)
  In Fishes the organ of hearing acquires a considerable increase in the complexity
of its organization.  It consists of a  vestibular sac, with  the accession of, in general,
three semicircular canals.  In the myxine, however, a fish of  very low organization,
there is only one of these canals.  In the lamprey there are only two. The vestibular
sac consists of a large sac (uiriculus of Breschet),  into  which the semicircular canals
open, and with  the walls of which  they are continuous, and  of a  small offset  from
this larger one (the sacculus of Breschet).  This  apparatus is composed  of a  thin,
transparent, elastic membrane.  It is filled  with fluid, and contains in each sac, either
porcelainous  bodies (otolithes), of beautiful structure and great  diversity, as in the
osseous fishes, or masses of pulverulent  deposit,  like  powdered chalk (oiokonia), as
in the cartilaginous fishes.  These, whether hard or soft, consist of carbonate of lime,
and therefore  may be quickly decomposed by  a  mineral acid.  The whole of this
auditory apparatus is deposited in an  excavation of the cranial wall, which commu-
nicates with the cavity of the cranium itself, excepting in the rays and sharks, in which
it is enclosed by the cranial cartilages.  It is suspended in fluid (part, probably, of
the cerebro-spinal fluid), which  constitutes the analogue of the perilymph in the
higher animals.  In some fishes, according to Breschet, an additional offset from the
larger sac exists, to which he gives the name cysticule.  All these parts are analogous
to the membranous labyrinth of the  higher animals, there being nothing to represent
the tympanum or the cochlea.  In many of the osseous fishes  the auditory apparatus
has no communication whatever with  the exterior.  In rays and sharks, however, a
prolongation of the labyrinth extends  through an opening in the occipital portion of
the skull  to the surface just beneath the skin.'   In many fishes, according to Weber,
there  is an intimate connection between  the auditory  apparatus  and the swimming
bladder, although their cavities have no communication with each other.
  In Amphibia, the auditory apparatus is closed off from the cranial cavity, and is
contained in  the  cranial bones.  It consists of a  vestibule with three semicircular
canals.   In some, there  is placed  external to  this  labyrinth a tympanic cavity, 
444
INNERVATION.
closed on the exterior by a membrane, which is intimately united with, or a portion
of, the integument, or a thin  layer of cartilage.  An osseous pillar (the columella),
or a chain of two  or  three ossicles, extends from  the wall of the vestibule to this
tympanic membrane, analogous to the  tympanic bones in  the human subject.  In
the Reptiles, there  is  a  short canal connected with  the vestibule, analogous  to the
cochlea.  The existence of this canal establishes that of a second external opening
belonging to the labyrinth, or fenestra  cochleae, in  addition  to the fenestra vestibuli.
Some of the Reptiles, as the serpents, are devoid of a distinct tympanic cavity; but
the existence of a columella beneath the skin indicates a rudimentary state of it.  In
others, as  the tortoises, crocodiles, and  lizards, such  a cavity exists, with  its usual
canal of communication with the  fauces, the Eustachian tube, and with a columella.
The fluid of the  labyrinth contains crystalline particles in place of otolithes.
  In  Birds, the  organ of hearing has the same parts as in the higher  reptiles. Its
labyrinth has the cochlea and semicircular canals, and the two  fenestra?, and  there
is a tympanic cavity  with a  columella. The cochlea is a very slightly bent  canal,
divided by a membranous septum into two  passages, scala vestibuli, and scala
tympani.
  In  Mammalia, the general characters  and structure of the organ of hearing closely
resemble  those of man.

   In examining the anatomy of the human ear, we shall first describe
the external   ear,  next, the middle ear, or tympanum, and lastly, the
labyrinth.
                                  Fig. 131.
  General view of the external, middle, and internal ear, as seen in a prepared section through a,
the auditory canal,  b. The tympanum or middle ear. c. Eustachian tube, leading to the pharynx.
d. Cochlea; and e. Semicircular canals and vestibule, seen on their exterior, as brought into view
by dissecting away the surrounding petrous bone.  The styloid process projects below; and the
inner surface of the carotid canal is seen above the Eustachian tube. From Scarpa.

   The External Ear  comprises  the  free, expanded part, auricle  or
pinna, and the auditory canal or external meatus.
   The auricle presents an outer surface,  which  is  on the whole  con-
cave, and slightly inclined forwards.   On  this surface are  several
eminences  and  depressions, resulting  from  the  folded,  or  rather
crumpled, form of its cartilaginous basis, and which are seen reversed
on the free portion of the opposite surface.   These are:—a  prominent
rim or helix,  and within  it another curved  prominence, the anthelix, 
THE EXTERNAL EAR.
445
which bifurcates above, so as to enclose a space, the scaphoid fossa,
and  describes  a  circuit round  a  deep, capacious, central cup, the
concha.   At the end of the helix, in front of the  concha, is a small
detached eminence, the tragus, so named  from its bearing a tuft of
hair resembling  a  goat's  beard.  Opposite this, behind and below
the concha, is  the antitragus.   Below is the  pendulous lobe,  com-
posed of dense areolar and  adipose tissues.   The concha is imper-
fectly divided into an upper and a lower part by the anterior curved
extremity of the helix.  The groove of the helix is  continued into the
upper  division,  and  the  auditory canal  leads  from the front and
deepest part of the lower division where it is overhung by the tragus
and its protective tuft of hairs.   The cartilage of  the pinna consists
of one principal  piece, from which that of the tragus and antitragus
is separated by a fissure filled  up by fibrous membrane.  It is very
flexible, and elastic, has a  yellowish  colour, and belongs to the same
category as the cartilages  of the alas nasi, &c.  Ligamentous  fibres
bind the concha  behind and  above, and the tragus in  front to the
bone and fascia in the neighbourhood.  A few muscular fibres passing
between different parts of the  auricle, serve to impress upon  them
movements, but  so slight  as to be  hardly  worthy of note.   These
fibres are found  externally on  the tragus, the antitragus, the upper
end  of the helix,  and behind on  the concha.   The whole of the car-
tilaginous part  of the ear is rendered  movable  by three muscles, the
superior and anterior auris, arising from the epicranial  aponeurosis,
and  converging  to the concha and  helix, and the posterior auris,
passing between the mastoid process and concha.
   The auditory canal passes  from the concha inwards for about an
inch, or rather more.   It  inclines a  little forwards, and is  slightly
bowed, so  as to be higher near the middle than at either end.  Its
width does not equal  its height, and it is altogether narrower in the
middle.  The  membrana  tympani,  which  terminates it, is placed
obliquely, in consequence of the lower side of the meatus being longer
than the  upper.   The  canal consists of two  parts, a  cartilaginous
and fibrous one, and an osseous.   To form the  first, the cartilage  of
the concha and tragus is  prolonged inwards  as far as  the auditory
process of the temporal bone,  and  constitutes a  tube  imperfect  at
the upper and  back  part, where its deficiency is supplied by fibrous
membrane.   This  cartilage  is rendered still  further  movable  by
partial slits in a vertical  direction  (incisura Santorini).  Muscular
fibres are described by  some to exist in  the meatus, which, accord-
ing  to Haller,  become shortened by their contraction.    The osseous
part of the auditory canal consists in the foetus of  a ring of bone,  to
which  the  membrana tympani is attached (tympanic ring of  the tem-
poral bone).   In the  adult, it  is nearly three-quarters of an inrh
long, and gives the meatus the form  and direction already described.
   The  skin of the external ear is delicate, and well supplied with
vessels and nerves.   The  orifice of  the  meatus, besides being con-
cealed behind the tragus, is defended by hairs, and a close arrange-
ment of ceruminous glands, which  furnish an abundant secretion,
calculated to entangle particles of dust, or small insects, and to pre- 
446
INNERVATION.
vent  their entrance into the organ.   These  glands are principally
seated in the subcutaneous  tissue, where the cartilage  is deficient,
and do  not  extend into the osseous portion of the  canal.   The
cerumen  is an oily, very bitter substance,  of a  yellow colour, and
contains, in  addition to  fat, albumen, and colouring matter, a bitter
principle analogous to that of the  bile.   If not removed from time
to  time, it is liable  to  form  hard pellets,  which either impact the
passage, or  come  into contact with the  membrana  tympani, and  in
either case seriously interfere with the transmission  of sound  to the
internal  parts.   These concretions are partially soluble  in ether and
turpentine.
   The  Middle Ear, or  tympanic  cavity,  is a space filled with air,
communicating with the  pharynx by the Eustachian  tube, and inter-
posed between  the external  meatus  and the labyrinth.   It opens
behind  into the  mastoid cells, which  are also  filled  with air, and  it
is traversed by a chain of moveable bones, connecting the membrana
tympani  with the vestibule,  or  common  central  cavity of the  laby-
rinth.   The  tympanum  is of irregular shape, compressed  laterally,
and lined by a very delicate  ciliated  epithelium, prolonged  from the
pharynx.
   The external  wall  of  the  tympanum is formed by the membrana
tympani, and a  small extent of the surrounding bone.  The mem-
brane is nearly  oval, but wider above than  below, and as already
stated, placed in a slanting direction, so as to form an obtuse angle
with  the upper  wall, and an acute one of about 45° with  the floor
of the auditory canal.  It consists  of three laminae, an external, mid-
dle, and internal.   The  external is derived from the cuticular lining
of the canal,  and easily detaches itself with that structure after mace-
ration.   The middle  is strong and fibrous,  perhaps  analogous to the
dermal part of the  integument, and attached through the medium  of
a dense fibrous rim to the bone, which presents a distinct groove for
its  reception, except above.   The handle  of the malleus  is firmly
united to this layer of the membrane, in a vertical direction as far
down as the centre, and draws the  membrane  inwards along that
line, so that  its outer surface is  concave, its inner convex.  The
abundant small  vessels  supplying this part run along the handle  of
the malleus,  and  thence radiate more  or less directly towards the
border.   The fibrous tissue  is in  part  similarly  disposed, and thus
seems to have led Sir E. Home to  describe a radiating muscle in the
membrane, which  does  not  appear to exist.   Seen from  within, a
concentric arrangement  of the  fibres is  more obvious.   The inner
layer  is the  ciliated epithelial  lining of  the cavity, which  is easily
scrapedoff'for examination in the fresh state (see  p. 73).
  The internal wall of the tympanum (fig. 132) has two orifices  of
communication with the  internal ear;  the fenestra ovalis, a, leading
to the vestibule,  and the fenestra rotunda, b, opening into the cochlea.
Both theseare closed by  membrane which prevents the escape of the
fluid contained in these inner  chambers, and communicates vibrations
to it.   The fenestra ovalis is  likewise occupied  by the base of the
stapes, one of the chain of ossicles connecting it with the membrana 
THE INNER WALL OF  THE TYMPANUM.           447
tympani.   Between the fenestras is the promontory, c, corresponding
to the first turn of the cochlea, and  furrowed by two or three canals
for the nerves which form the anastomosis of Jacobson, n.   Behind
the fenestra^ ovalis is a  conical eminence, the pyramid, d, hollowed,
and  presenting a small  orifice at its summit, which is on a level with
the  middle  of the  vestibular fenestra.  The pyramid contains the
stapedius  muscle, the  tendon of  which  emerges at  its summit, and

                                Fig. 132.
  Diagram of the inner wall of the tympanum after maceration, the outer wall and ossicles being
 removed, a. Fenestra ovalis. 6. Fenestra rotunda, c. Promontory,  d. Pryramid, with the orifice
 at its apex. e. Projection of the aqueductus Fallopii.  f. Some of the mastoid cells communicating
 with the tympanum, g. Processus cochleariformis, bounding i, the  canal for the tensor tympani
 muscle: the anterior pyramid is broken off, if it existed, h. Commencement of the Eustachian tube.
 j. Jugular-fossa, immediately below the tympanum, k, k. Carotid canal, with the artery in outline,
 to show its course in relation to the tympanum and Eustachian tube.  I. Portio dura of the seventh
 pair of nerves, as it would be seen in the terminal part of the aqueduct of Fallopius. m. Chorda
 tympani, leaving the portio dura, and entering a short canal, which opens in the tympanum, at the
 base of the pyramid,  n. Grooves for the tympanic plexus.

 runs to the neck of  the stapes.   This  muscle  is supplied by a twig
 from the portio dura of the seventh  pair.   At the base of the pyramid
 is  an  aperture through which the chorda tympani, m,  enters the
 tympanum.   Thence this nerve passes forwards, between the handle
 of the malleus and the long  arm of the incus, and emerges through a
 canal close to the Glaserian fissure.   Above the  pyramid  an arched
 prominence, e, indicates the course of the aqueductus Fallopii,  close
 to the tympanum; and behind  this is the free communication with
 the mastoid cells, f
   The  anterior part of the  tympanum  presents  above  the  canal  for
 the tensor tympani muscle,  and below the orifice of the Eustachian
 tube.   The former,  i, is chiefly formed by a curled plate of  bone, the
processus cochleariformis, g, ending in a kind of perforated  summit,
 that some have termed, anterior pyramid.  This  is a little above the
 fenestra ovalis, and  gives passage  to  the tendon of the tensor  tym-
 pani, which becomes attached to  the short  process of the  malleus. 
448
INNERVATION.
The Eustachian tube, about one inch and a half in length, leads from
the tympanum downwards, forwards, and  inwards, to its orifice  in
the pharynx, which is seen as a slit with an elevated edge close be-
hind the inferior turbinated bone of the  nose (see fig. 106, t, p. 396).
By its straight, but inclined course, the passage of mucus from the
tympanum is facilitated.   Its upper  extremity for more than half an
inch is bony,  while in  the  rest of its extent it is cartilaginous.   It
dilates at  each  end, especially the lower, where the cartilage is thick-
ened and  everted.   It forms  a passage for  the air in and out of the
tympanum.   It exists in all animals in which a tympanum is found,
but in many, the tubes of opposite sides have a common outlet on the
pharynx.   External to the opening for the Eustachian  tube is the
opening for the anterior muscle of the malleus (Glaserian  fissure) and
that for the  escape of the chorda tympani.
   The ossicles  of the tympanum are three, the malleus, the incus, and
                           the stapes (fig. 133).  The malleus (ham-
                           mer) has a large extremity above, termed
                           the  head, m, bounded  by a constriction
                           or  neck, from  which  the handle (manu-
                           brium), h, passes down, imbedded in the
                           membrana tympani, as already described.
                           Its concavity directed outwards explains
                           the similar  inequality of  that membrane.
                           The short process is a slight conical pro-
                           jection from the  neck,  which  receives
                           the insertion of the tensor tympani mus-
                           cle: the slender process  (p.  gracilis), g,
                           also passes from  the neck, but forwards
                           and outwards, to enter the Glaserian fis-
                           sure.  On the back of the head and neck
                            an articulation is formed with the incus.
                            The incus (anvil), is  shaped  not unlike
                            a molar tooth.   It articulates with the
                            malleus by the anterior surface or summit
                            of its body, and has two processes, a short
                            and a long crus:  the former, sc, has a
                            backward  direction, and projects  into
the mastoid cells, the  latter, le, descends to a level with the  fenestra
ovalis,  bends  inwards,  and  is tipped  with  a lenticular process, to
which the head of the stapes is attached, a.  The stapes, or stirrup
bone, s, is almost  sufficiently described by its name.   Its  construction
is truly elegant.   It has a head, neck, two branches, and a base.  The
last fits into the fenestra ovalis, to  the margin of which it is attached,
by membrane,  so  as to enjoy  some freedom of motion.   Its neck re-
ceives the insertion of the stapedius muscle.   The chain of ossicles,
now described, stretches across  the tympanum  by no  means in a
straight line, and  its  parts  are permitted  to enjoy some  degree of
motion, not  merely by the double joint existing  between them, but
by the mode of their attachment at either end.
   These bones are moved by small muscles, two of which  are not
Fig. 133.
 Ossicles of the left ear articulated,
and seen from the outside and below.
in. Head of the malleus, below which
is the constriction, or neck.  g. Pro-
cessus gracilis, or long process, at the
root of which is the short process, h.
Manubrium, or handle, sc. Short crus ;
and le, long crus of the incus.  The
body of this bone is seen articulating
with the malleus, and its long crus,
through the  medium of the orbicular
process, here partly concealed, a, with
the stapes, s. Base of the stapes. Mag-
nified three diameters. From Arnold. 
THE INTERNAL EAR.
449
disputed.  These are the internal muscle of the malleus, and the sta-
pedius muscle.   Each of these muscles consists of striped fibres.
   The internal muscle of the malleus, or tensor tympani, occupies the
canal  above the osseous portion of the  Eustachian tube.  It is at-
tached in front to the under surface of the petrous bone, and to  the
cartilage of the Eustachian tube; it  proceeds backwards, and ends
in a tendon which turns abruptly outwards from the osseous canal in
which the muscle is lodged, and is inserted into the short process of
the malleus.  It draws  this part inwards, and thus heightens the ten-
sion of the membrana  tympani.  An anterior muscle of the malleus,
or laxator tympani muscle, is described by many anatomists  as passing
from the Glaserian  fissure to the processus gracilis.  The stapedius
muscle occupies  the conical  interior  of the pyramid ;  its surface is
aponeurotic, its interior  fleshy, and it terminates  in a  small  tendon
which emerges at the  apex of  the pyramid, and then passes to be
inserted  into the neck of the stapes.  In  contraction it would fix the
stapes by pulling its neck backwards.   It  probably compresses  the
contents of the  vestibule.
   Of the  Internal Ear, or Labyrinth.   This is the  potential  part of
the organ of hearing, and includes the  ultimate  distribution of the
nerve.   It  consists  of three  parts, the vestibule,  the semicircular
canals, and the cochlea, all of which, from their delicacy and minute-
ness of structure, demand careful examination.  They are a series of
cavities hidden in the hardest part of the petrous bone, communicating
on the outside with the  tympanum, by the fenestras ovalis and rotunda
already described, and on the  inside with the internal auditory canal,
which conveys the nerve to  them.   The very compact bone imme-
diately bounding these cavities,  considered apart from the less dense
bone which surrounds it, is termed the osseous labyrinth, in distinction
from a membranous labyrinth within.
   Of the Osseous Labyrinth.—The singularly complex shape of this
part of the organ makes it difficult to describe.  1.  The vestibule, or
common central cavity, placed immediately to the inner side of the
tympanum, is flattened from side to side, and about a fifth of an inch
in height, as well as from before backwards.   The semicircular canals
open into it  by five orifices behind, the cochlea  by a single one  in
front; on its outer wall is the fenestra ovalis, on  its  inner several
minute holes, including the macula cribrosa  for the entrance of a por-
tion of the auditory nerve from the internal auditory  meatus.   At the
hinder part of the inner  wall is the orifice of the aqueductus vestibuli,
a fine canal penetrating  the vestibule from the  posterior surface of the
petrous bone, and containing, as some describe, a tubular prolongation
of the lining membrane of the vestibule, ending  in  a  minute pouch
between two layers of the  dura mater, within  the cranial  cavity.
Breschet considers this  to be an,evidence of a continuity once exist-
ing between the  lining membrane of the cranium,  and that of  the
vestibule, and it is certain that  in most  fishes the vestibule is a pro-
cess of the cranial cavity, or separated  from it only by a membrani-
form septum.   Whatever other use the aqueduct of the vestibule may 
450                        INNERVATION.

serve, it seems, certainly, to convey small vessels to the internal ear.
The lower part of the inner wall presents a hemispherical depression
(fovea  hemispherica), and  immediately  above it, and  on  the upper
wall, another,  transversely oval and larger  (fovea semi-elliptica).
These are separated by a small pyramidal eminence.

                               Fig. 134.
  Osseous labyrinth of the left side.  o. Fenestra ovalis, leading into the cavity of the vestibule.
From this a bristle, t, is passed into v v, the vestibular scala of the cochlea, which is laid open in
part by the removal of the outer wall. r. Fenestra rotunda, seen almost in profile.  Through this a
bristle, t, is passed into the tympanic scala of the cochlea, 11, exposed by the removal of part of the
membranous portion of the lamina  spiralis. The three  semicircular canals are seen, with their
extremities entering the vestibule, and one end of each dilated into an ampulla. Magnified 3i di-
ameters.  Partly from  Scemmerring.

   2. The  semicircular  canals are  three in number, all opening at
both ends into the vestibule, so that there would be six orifices, were
not one of the orifices common to two of the canals.   The canals are
of unequal length, but all describe more  than half a  circle, and their
cavity is  not cylindrical, but slightly compressed on the  sides, and
about a  twentieth of an  inch in diameter.   Each  is dilated at one
end into  an ampulla, of more than twice  the diameter of the tube, and
at  the opposite  end  it opens out slightly on entering the vestibule.
Each  canal  lies  in  a  different plane, the direction of  which being
constant, should be  carefully  noticed in relation to their function.
The superior vertical canal is also anterior, and lies across the petrous
bone.  It forms about  two-thirds of a circle, and its extremities are
more divergent  than those of the others.   In the foetus the concavity
of  this canal is free, owing to a deficiency in the  substance of the
petrous bone, and its arch forms a  projection within  the cranium,
even in the adult.   The ampulla is on its outer extremity.   The in-
ferior vertical canal is also posterior, and  runs parallel to the posterior
surface of  the petrous bone, and  therefore at  right angles to the for-
mer.   The ampulla is at  its lower extremity, and its upper end joins 
THE COCHLEA.
451
the inner end of the former canal, to constitute a  common  canal  an
eighth of an inch long, rather wider than those which join to form it,
and opening behind and below.   The horizontal canal is also inferior,
and shorter than  either of the others;  its arch is directed  outwards
and backwards; its ampullar extremity is close to that of the superior
vertical canal.

                              Fig. 135.
 Interior of the osseous labyrinth. V. Vestibule,  a v. Aqueduct of the vestibule, o. Fovea semi-
elliptica. r. Fovea hemispherica. S. Semicircular canals,  s. Superior,  p. Posterior, i. Inferior.
a a a. The ampullar extremity of each.  C Cochlea,  ac. Aqueduct of the cochlea, sv. Osseous
zone of the lamina spiralis, above which is the scala vestibuli, communicating with the vestibule.
st. Scala tympani below the spiral lamina.  From Sffimmerring.

   3.  The cochlea is, in shape, very like a common snail-shell.  It lies
almost horizontally, its apex forwards and  outwards, its base marked
near the bottom of the internal meatus, by a depression exhibiting a
spiral arrangement of pores for the  reception of the cochlear division
of  the auditory nerve.  From  base to  apex extends the irregularly
conical axis, modiolus, or columella, which is perforated by numerous
branching  channels, ascending  from the pores just mentioned, and
distributing  the  nervous  filaments in  regular succession within the
spiral cochlear canal which winds around the axis.  This spiral canal
is  about  an  inch and a half in length, if measured  along its outer
wall, and diminishes gradually in  size from  the base to the summit
of the cochlea, where it ends in a cul-de-sac.   At its commencement
it is about one-tenth  of an inch in diameter, but at  its termination
scarcely half that size.  At its base it  diverges somewhat  from the
modiolus, towards the tympanum and vestibule, and presents three
openings.   Of these, one, free and oval, enters the vestibule; another
is  the fenestra rotunda, communicating with the  tympanum in the
dry bone, but filled up in  the recent state by a proper membrane, the
membrana tympani secundaria;  the  third is the minute  orifice of the
aqueductus cochlea, a funnel-shaped  canal leading to the jugular fossa, 
452
INNERVATION.
and supposed to transmit a small vein.   The  spiral canal  describes
about two turns and a half, of which the first, passing round the large
base of the modiolus, takes much the widest sweep, so as to encircle
most of the second turn.   The inner wall of this coiled canal,  as has
been shown by Ilg, forms the outer wall of the modiolus.
  The spiral canal of the cochlea is subdivided into two passages by
an osseo-membranous  lamina,  extended between its  modiolar  and
peripheral wall, and of course taking the same spiral direction  as the
canal itself.   This is the lamina spiralis, the fundamental element of
the cochlea, on which  the nervous tubules are spread out.  More
than half its breadth on the side of the modiolus is formed by a very
brittle  osseous  process from  the modiolus,  called  the osseous zone,
enclosing  minute channels continuous with those  of that  part,  and
transmitting the nerves;  its opposite or outer-portion is membranous
and muscular, and connects the outer thin edge of  the osseous zone
to the outer wall.  The osseous zone commences  gradually within
the vestibule, and enters the spiral canal  between the vestibular and
tympanic  openings of  the cochlea, forming,  with  the help of the
membranous extension,  a complete  septum  between  them.   The
passages, or scala, into which  the spiral lamina divides the  canal,
correspond,  therefore,  respectively to those  chambers; the upper,
towards the apex of  the  cochlea, scala vestibuli, the lower, towards
its base, scala tympani.   These scalse  are, on the whole, pretty equal
in size; the vestibular  scala is, however, the smaller at the base, the
tympanic, near the apex, of  the coil; and  the latter ceases  ere it
reaches the summit.  At the apex of  the cochlea the parts have  an
arrangement difficult  to describe,  though  easily  understood  when
seen.  The  axis, no longer hollow, and containing nerves, is reduced
to a delicate lamella at about half a turn from the dome-like summit,
or cupola, formed by the last part of the spiral canal.  This lamella,
which is the real apex of the modiolus, immediately expands, stretches
upwards, and  becomes more twisted on itself, so as to include part,
or all of the last half turn of the cochlear canal, being termed from its
appearance as viewed from below, the infundibulum, or funnel.   The
wide part of this imperfect  funnel is directed towards the cupola,
with which  it blends.   It is not open above, but  on the side,  and it
is, in fact, the outside of the last half turn of the  canal, projecting
into the turn below.
   The osseous zone of the spiral lamina ceases with the hollow mo-
diolus at the  slender  lamella  already mentioned,  terminating by a
small  projecting  hook (hamulus), the concave border of which is
free, and  directed towards the lamella, so as to leave an opening or
deficiency, the  helicotrema of Breschet, by which the scalae  tympani
and vestibuli  communicate.   The membranous  zone connects the
convex border of the  hook  to the  outer wall, and  is also continued
upwards beyond the point of the hook, presenting, however, towards
the infundibulum, like  the hook itself, a free concave  border, con-
tributing to  form the orifice of communication.
   Such being  the form of the osseous labyrinth, we may now pro-
ceed to consider the more delicate parts of  the organ, and the imrae- 
SPINAL LAMINA OF THE COCHLEA.
453
diate distribution of the auditory nerves.   We must premise that the
cavity of the  osseous labyrinth is  occupied  by a limpid  fluid, the
perilymph, so called  by De  Blainville, from  its surrounding, though
in the vestibule and  semicircular canals  only, a hollow membranous
apparatus, the  membranous labyrinth, which  latter itself contains a
similar fluid, the endolymph.
 Cochlea of a new-born infant, opened on the side towards the apex of the petrous bone.  It shows
the general arrangement of the two scalae, the lamina spiralis, and the distribution of the cochlear
nerve. At the apex is seen the modiolus expanding into the cupola, where the spiral canal termi-
nates in a cul-de-sac. The helicotrema is not visible in this view. From Arnold.

   Of the Structure of the Spiral Lamina of the Cochlea.—We shall
term the two surfaces of this lamina tympanic and vestibular, as they
regard respectively the  tympanic or  vestibular scala.   The osseous
portion  of the spiral  lamina  extends more than  half way from  the
modiolus  towards the  outer wrall, and  is  perforated, as already  de-
scribed, by a series of  plexiform canals for  the  transmission  of  the
cochlear nerves; these  canals,  taken as a  whole, lie  close  to  the
lower or tympanic surface, and open at or near  the  margin of this
zone.   The vestibular surface  of the osseous  zone presents in  about
the outer  fifth of its extent, a  remarkable covering, more resembling
the  texture of cartilage than  anything else, but having  a  peculiar
arrangement quite unlike any other with  which  we are acquainted.
Being uncertain respecting the office of this structure, we shall term
it the denticulate lamina (figs.  137,  and 138), from a beautiful series
of teeth,  forming its outer margin, which project free  into the ves-
tibular scala, and, in the first  coil, terminate almost on  a  level with
the margin of the osseous zone, but more within this margin towards
the  apex  of the cochlea.   They thus constitute a kind  of second
margin to the osseous zone, on the vestibular side of the true margin,
and  having  a groove beneath them,  which  runs  along  the whole
lamina  spiralis, in  the  vestibular scala, immediately above the true
margin of the osseous zone.   The  intervals between the teeth are to
be seen on their upper surface, on  their free edge, and also within
this  groove, so that the  teeth  are  wedge-shaped, and their  upper
and  under surfaces, traced from the free edge, recede.   The free
projecting part, or teeth of  the denticulate  lamina form less than  a
fourth of its entire breadth, and in  the  remainder of its  extent  it  ap- 
454
INNERVATION.
137.
pears to rest on the osseous zone; seen from above, after the osseous
zone has been rendered more transparent by weak hydrochloric acid
(fig. 138), rows of clear lines may be traced  from the teeth  at the
                                      convex edge, towards the op-
                                      posite or concave edge  of the
                                      lamina.   These  lines  appear
                                      to  be a  structure  resembling
                                      that  of  the teeth themselves,
                                      and  they  are  separated from
                                      one another  by rows of clear,
                                      highly   refracting   granules,
                                      which render the intervals very
                                      distinct.   These  intervals,  as
                                      seen  in the figure, are more or
                                      less  sinuous  and   irregularly
                                      branched.
                                        The denticulate lamina, thus
                                      placed  on  the vestibular sur-
                                      face  of the  osseous zone, is
                                      above, and  at  some distance
                                      from the plexus of the cochlear
                                      nerves, which lie near its tym-
                                      panic surface.  The vestibular
                                      surface  of the  osseous zone,
                                      including  the  denticulate la-
                                      mina, is convex, rising from
                                      the free series of teeth towards
                                      the modiolus.
                                        In the groove already men-
                                      tioned there is a series of elon-
gated  bodies, not unlike columnar epithelium, in which the  nuclei
are very faint.  These bodies are  thick and cubical  at one end, and
taper much towards the other.  They are united  in a row; and it is
possible they may have some analogy to the  club-shaped bodies of
Jacob's membrane.  We can assign them no use.
   Continuous with the thin margin of the osseous zone is the mem-
branous  zone.  This  is  a transparent glassy lamina,  having some
resemblance  to the elastic laminae of the cornea, and the capsule of
the lens.   A narrow belt of  it next the osseous zone is smooth, and
exhibits no  internal structure,  while in the rest  of its width it is
marked by a number of very minute straight lines, radiating outwards
from the side of the modiolus.  These lines are very delicate at their
commencement, become more strongly marked  in the middle, and
are again  fainter  ere they cease, which  they do at a curved  line on
the opposite side.   Beyond this the membranous zone is again clear,
and homogenous, and receives the insertion of the cochlearis muscle.
The inner clear belt of the membranous zone is little affected by acids.
It seems hard and brittle.  The  middle or  pectinate portion is more
flexible, and tears in the direction of the lines.   The outer clear belt
is swollen, and partially destroyed by the action of acetic acid.   Along
 A. Section of the cochlear canal, where the scalae
are equai. sv. Scala vestibuli.  st. Scala tympani.
o. Osseous zone of lamina spiralis,  d. Denticulate
lamina, m. Membranous zone.  c. Cochlearis mus-
cle,  r. Osseous rim of the groove of the cochlearis.
 B. Margin of osseous zone, more magnified,  sv.
Scala vestibuli.  st. Scala tympani.  g. Groove, be-
tween d, denticulate lamina, and m, membranous
zone springing from edge of the osseous zone. n.
Cochlear nerves and capillaries, distributed on the
tympanic surface of the osseous zone. 
THE COCHLEARIS MUSCLE.
455
the inner clear belt, and on its tympanic surface, runs a single some-
times branched vessel, which would be most correctly called a capa-
cious capillary, as it  resembles  the capillaries  in  the texture of its
wall, but exceeds them in size.   It is the  only vessel supplied to the
membranous zone, and seems to be thus regularly placed, that it may
not mar the  perfection of the part as a recipient and propagator of
sonorous vibrations.
Fig. 138.
Fig. 139.
oSPSsO
  Denticulate lamina of the os-
seous zone of the lamina spira-
lis, seen on the vestibular sur-
face, a. Free edge of the teeth,
which are separated by fissures
as far as the line 6.  The clear
tracts, with intervening rows of
globules, are seen at d.  e. Mar-
gin towards the axis of  the
cochlea. From  the sheep.—
Magnified 100 diameters.
"O
 Tympanic surface of a portion of the lamina spiralis of the
cat.  a. Termination of the cochlear nerves at the border of the
osseous zone, with capillaries ramifying over them.  b. Inner
clear belt of the membranous zone. c. Marginal capillary on
the tympanic surface,  d. Pectinate portion of the membranous
zone.  The half-detached fragment on the opposite edge shows
its mode of tearing, e. Outer clear belt of membranous zone,
torn from the cochlearis muscle. Magnified 300 diameters.
   Of the Cochlearis Muscle.—At its outer  or convex  margin, the
membranous zone is connected to the outer wall by a semi-transparent
structure.  This gelatinous looking tissue was observed by Breschet,
and is indeed very obvious on opening the cochlea;  but  we are not
aware of any one having hinted  at  what we  regard  to  be its real
nature.   The outer  wall of the  cochlear canal  presents a  groove,
ascending the entire coil, opposite  the osseous zone of the lamina
spiralis, and formed  principally by a  rim of bone, which, in section,
looks like a spur (fig. 137, r), projecting from the tympanic margin
of  the groove, the opposite margin  being very slightly or  not at  all
marked.   This  groove  diminishes in size towards the  apex of the
cochlea.   It gives attachment  to the  structure in  question, by means 
456
INNERVATION.
 of a firm dense film of tissue, having a fibrous character, and the fibres
 of which run lengthwise in the groove, and are intimately united to it,
 especially along the projecting rim.   From this cochlear ligament, the
                               cochlearis muscle passes  to the  mar-
                               gin of  the  membranous  zone, filling
                               the groove,  and  projecting into the
                               canal, so as to assist in  dividing the
                               tympanic  and  vestibular scalae  from
                               one another, and thus forming in fact
                               the most external, or the muscular zone
                               of the spiral lamina.  Thus the coch-
                               lear muscle is broad at its origin  from
                               the groove of bone, and  slopes above
                               and below to the thin margin in which
                               it terminates, so that its section is tri-
                               angular, and it presents three surfaces,
                               one towards  the groove of bone, and
                               one to each of the  scalae.  The sur-
                               face towards the vestibular scala is
                               much wider than  that  towards  the
                               tympanic  scala,  and  presents,  in a
                               band  running  parallel to,  and  at a
                               short distance from the margin of the
 membranous zone, a series of arched vertical pillars, with intervening
 recesses, much resembling the arrangement of the musculi pectinati
 of the heart (fig.  140, c).  These lead to and terminate in the outer
 clear belt of the membranous zone, which forms a kind of tendon to
 the muscle.   This entire arrangement  is almost sufficient of itself to
 determine the muscular nature of the structure.  If its fibres were
 of the striped variety, no doubt would remain; but its mass, evidently
 fibrous, is loaded  with  nuclei, and filled  with capillaries, following
 the direction of the fibres, and in  almost all respects it has the closest
 similarity to the ciliary muscle of the eye.   The  nuclei  diminish in
 number  as  the fibres  end in  the  tendinous part; and they are made
 much more evident by the addition of acetic acid.  The action of the
 muscle must be that of  making tense the membranous portion  of the
 lamina spiralis, and so perhaps of adjusting it to the modifications of
 sound.   As the ciliary muscle, though of  the unstriped  variety, ad-
justs the transparent  media of the eye to distinct vision at different
 distances under the guidance of the will,  so it is not impossible  that
 the cochlear muscle may have  a  voluntary adjusting power, though
 its precise mode of action as a part of an acoustic apparatus may still
 remain obscure.   On  the. whole,  however, we are more disposed to
 regard this very interesting structure as having a  preservative  office,
 as being placed there  to defend the  cochlear nerves  from  undue
 vibrations of sound, in  a way analogous to that in which the iris
 protects  the retina from excessive light.  These nerves are  acted on
 principally by  vibrations brought through  the  osseous  part  of the
 cochlea,  and it is probable that the arrangement of the scalae  is one
 designed to allow of protective movements of the lamina spiralis by
Fig. 140.
 Inner view of cochlearis muscle of the
sheep, a. Line of attachment of membra-
nous zone of lamina spiralis, of which a
portion, b, remains attached. The surface
below this line is in the scala tympani, the
surface above, in the scala vestibuli. c.
Projecting columns, with intervening re-
cesses, in the vestibular part of the coch-
learis muscle. 
THE COCHLEAR NERVES.
457
vessels
it, and
line of
Fig. 141.
muscular action, under a stimulus reflected from impressions on the
auditory nerve.
   The  capillaries  of the ciliary muscle are  derived from
meandering  over the  walls  of the scalae  before entering
those from above and  below do not  anastomose across the
attachment of the membranous zone, thus indicating that  the con-
tinuation of  this zone enters as a plane of tendon into the interior  of
the  muscle,  dividing it into two parts,  and receiving the  fibres  in
succession.
   The  scalae of the cochlea are lined with a nucleated membrane,  or
epithelium, which is very delicate and easily detached, usually more
easily seen in the vestibular than in  the tympanic scala,  and in many
animals containing scattered pigment.
   Of the Cochlear Nerves.—These enter from the internal  auditory
meatus through  the  spirally-arranged  orifices at
the base of the modiolus, and  turn  over in suc-
cession into  the  canals hollowed in the  osseous
zone of the  spiral  lamina, close  to  its tympanic
surface.  In  this distribution the nervous  bundles
subdivide and reunite  again and again,  forming
a  plexus  with elongated  meshes,   the  general
radiating arrangement  of  which can be readily
seen through the substance of the bone when it has
been steeped  in diluted hydrochloric acid (fig.
141). Towards the border of the osseous zone the
bundles of the plexus are smaller and more closely
set, so as at length almost to form a thin  uniform
layer of nervous tubules.  Beyond  the  border,
and  partially on  or in the inner transparent  belt
of the  membranous zone, these tubules  arrange
themselves more or less evidently into small sets,
which advance a short distance  and then termi-
nate much on the same  level.  These terminal
sets  of  tubules are cone-shaped, coming to a kind
of point ere they cease.   The white substance of
Schwann exists in them throughout, but is thrown
into varicosities and  broken with extreme facili-
ty, and they  are interspersed with nuclei, so that
it is very difficult to discover the precise dispo-
sition of the  individual tubules (fig. 139,  a).
They  seem  to  cease  one  after another, thus
causing the set to taper; and  at least it  appears
certain  that evidence of loopings, such as have
been described  by some,  is wanting.   In the cochlea of the bird,
however, we have seen at one end a plexiform  arrangement of nucle-
ated fibres ending in loops;  but this is a  peculiar structure.
   The  capillaries  of the osseous zone  are most abundant on the
tympanic scala in  connection with  the  nerves now  mentioned, and
form loops near the margin, with here  and there an inosculation with
the large  marginal capillary already  mentioned.
     30
 Plexiform arrangement
of  the cochlear nerves
seen in the basal coil of
the lamina spiralis, treated
with hydrochloric acid.
There are  no  ganglion
globules  in this plexus,
which consists of tubular
fibres. a.Twigofcochlear
nerve in the modiolus, its
fibres diverging and re-
uniting in b, a band in the
plexus taking a direction
parallel  to  the zones.
From this other twigs ra-
diate, and again and again
branch and unite as far as
the margin of the osseous
zone c, where they termi-
nate.  From the sheep.
Magnified 30 diam. 
458
INNERVATION.
   Of the Membranous Labyrinth (fig. 142).—This has the same gene-
ral shape  as the bony cavities in which  it lies, but is considerably
                                  smaller, so that the  perilymph in-
                                  tervenes in some  quantity, except
                                  where the nerves passing to it con-
                                  fine it in close contact  with the
                                  osseous wall.   Its vestibular por-
                                  tion consists of two sacs,  viz.: a
                                  principal one  of transversely oval
                                  figure  and  compressed  laterally,
                                  called  the  utriculus,  or  common
                                  sinus,  occupying  the  upper  and
                                  back part of the cavity, in  contact
                                  with the fovea  semi-elliptica, and
                                  beneath this  a  smaller and more
                                  globular one, the sacculus, lying in
                                  the fovea hemispherica, near the
                                  orifice of the vestibular scala of the
                                  cochlea,  and  probably  communi-
                                  cating with the utriculus.
                                     The  membranous  semicircular
                                  canals have the same names, shape,
                                  and  arrangement as  the  osseous
                                  canals which enclose them, but are
                                  only a third of the diameter of the
                                  latter.   As the osseous canals open
                                  into  the vestibule, so  the mem-
                                  branous  ones open at  both ends
                                  into  the  utriculus—there  being,
                                  however, a  constricted  neck be-
                                  tween this sac and  the ampullated
extremity of each canal.   The auditory nerve sends branches to the
utriculus, to the sacculus, and  to the ampulla of  each  membranous
canal.  These nerves  enter  the vestibule by the minute apertures
before  described, and  tie down, as  it were, both the utriculus and
sacculus  to the osseous  wall at those points, the membrane being
much thicker and more rigid where the nerves join it.  The branches
to the ampullae of the superior vertical and the horizontal semicircular
canals enter the vestibule with the  utricular nerve, and  then cross to
their destinations, while that to the ampulla of  the  posterior vertical
canal traverses the posterior wall  of the cavity,  and opens directly
into the ampulla.
   The wall of the membranous labyrinth is translucent, flexible, and
tough.   When withdrawn from  its bed and examined,  it appears to
present three  coats, an  outer,  middle, and internal.   The  outer is
loose, easily  detached, somewhat  flocculent, and contains  more or
less colouring  matter disposed  in  irregular cells, exactly resembling
those figured  at page 409, from the outer surface  of the choroid coat
of the eye.  We have not found  a true epithelium on this surface.
The middle  is the  proper coat, and seems more allied to cartilage
Fig. 142.
 Membranous labyrinth of the left side, with
its  nerves and  otoliths:—su. Superior semi-
circular canal, with the ampulla and its nerve
at one end, and  the other end joined by p, the
posterior canal, to form the tubulus communis.
i. Inferior, or horizontal canal, with the am-
pulla and its nerve at one end, and the other
entering the utriculus separately,  c. Powdery
otolith seen through the translucent wall of the
common sinus, or utriculus, with  the nerves
distributed to it.  s. Powdery otolith of the sac-
culus  seen with its nerve, in a similar way.
n. Cochlear division of the auditory nerve cut
off where it enters the cochlea, d. Portio dura
of the seventh pair leaving the auditory nerve,
or portio mollis, to enter the aqueduct of Fallo-
pius.  Magnified.  From Breschet. 
        MEMBRANOUS LABYRINTH.—VESTIBULAR NERVES.     459

than to any other tissue; its limits are well marked, it is transparent,
and exhibits  in  parts  a  longitudinal fibrillation:  treated with acetic
acid, it  presents numerous corpuscles or cell-nuclei.   Where  it is
thinnest it has a near resemblance to  the hyaloid membrane of the
eye.  The internal  coat  is composed of nucleated  particles closely
apposed and  but slightly adherent; the nuclei are often saucer-shaped,
and when seen edgeways, have the uncommon appearance of a  cres-
cent.   They  easily become detached, and fall into  the endolymph.
Minute  arteries  and veins,  derived  chiefly  from a branch of the
basilar accompanying the  auditory nerve, enter the vestibule from the
internal meatus, and ramify on the  exterior of the membranous laby-
rinth, apparently bathed  in the perilymph.  A beautiful network of
capillaries, forcibly reminding  the observer of that belonging to the
retina, is spread out on the outer surface and  in the  substance of the
proper  coat.  These  vessels  have the simple  homogeneous  wall,
interspersed  here  and there  with  cell-nuclei, that characterizes the
capillary channels in many other situations.  There is an abundant
network of capillaries in  the  interior  of the utriculus  and sacculus
about the  terminal  distribution  of the nerves,  which evinces the
activity of the function of these parts.
   The membranous labyrinth, or its simple representative the audi-
tory sac, contains, in all  animals, either  solid or pulverulent calca-
reous matter, in connection with  the termination of  the vestibular
nerves.   This has been called  by Breschet otolith, or ear-stone, when
solid, as in the  osseous fishes, and otoconia, or ear-powder, when in
the form  of  minute crystalline grains, as in mammalia, birds, and
reptiles,  but  the  former  term may  be  conveniently   employed to
designate  both  varieties.  In the mammalia, including man,  it is
found  accumulated in small  masses  about  the  termination of the
nerves, both   in the utriculus  and sacculus, and we have found it
also sparingly scattered in the cells lining the ampullae and  semicir-
cular canals.   In the vestibular sacs, it appears to be entangled in a
mesh of very delicate branched fibrous tissue, in  connection with the
wall, and it  is most probably held in place by cells within which,
according to  Krieger, (De Otolithis, Berol., 1840,)  its  particles are
deposited.  It has a regular arrangement, and is  not free to change
its place in the  endolymph.   Otoliths consist always of carbonate of
lime.
   Of the Vestibular Nerves.—In consequence of the thickness of the
wall of  the  membranous  labyrinth where the nerves enter,  and the
presence there of  the calcareous and fibrous matter,  it  is not easy to
ascertain with certainty the precise manner in which  the nerves ter-
minate.   In  the utricle and saccule, they appear  to spread out  from
one another as they enter, and then to pass, some to mingle with the
calcareous powder, others to  radiate for a small  extent on the inner
surface  of the wall  of the cavity, where  they come  into connection
with  a layer of dark and closely-set nucleated  cells,  and presently
lose their white substance.  We have seen a fibrous film on the  inner
surface  of these parts, which  we are disposed to  consider as formed,
like the inner surface of the retina, by the union of the axis-cylin- 
460
INNERVATION.
ders of the nerve-tubes, but confirmatory observations are required.
Those that traverse  the calcareous clusters  have appeared to us, in
the most lucid views we have succeeded  in obtaining, to terminate
                                    by  free,  pointed  extremities,
              Fig. 143.                without losing  their white sub-
                                    stance.  In  the  frog  this  has
                                    been evident enough.
                                       The  nervous twigs belonging
                                    to  the  semicircular  canals  do
                                    not seem to advance beyond the
                                    ampullae, in  which  they have a
                                    remarkable distribution,  enter-
                                    ing  them,  as  Steifensand  has
                                    well  shown, by a transverse or
                                    forked  groove on their concave
                                    side, and which reaches about a
                                    third round.   Within this, the
                                    nerve projects  so as  to  form  a
                                    sort of  transverse bulge  within
                                    the ampulla.  Their precise ter-
                                    mination can be best seen in the
osseous fishes, vand has been described by  Wagner to be  loop-like, as
will be apparent from the adjoined figure.  We believe we have seen

                              Fi?. 144.
 View of the nerves going to the membranous la-
byrinth :— a. Branch to the ampulla of one of the
semicircular canals. It is seen perforatingihe wall
and expanding transversely  within.  6. Semicir-
cular canal cut across.  From Steifensand.
    Termination of the nerve in the ampulla of a Ray, highly magnified.  (From Wagner.)

this mode of termination, though  certainly never  so  plainly as the
figure  given by this excellent  author would indicate;  and we may
add that we  have found free extremities to the nerve-tubes, as well
as loopings, in  the ampullae of the cod.  The difficulty in these cases
of ascertaining the exact truth, arises from  the curves formed by the
nerve-tubes in  proceeding  to their  destination, and which are liable
to be  mistaken for terminal loopings. 
AUDITORY NERVE.
461
   Of the Auditory Nerve.—The portio mollis of the seventh pair has
its origin from the medulla oblongata by two roots.   One  penetrates
to the central part of the medulla oblongata in the same way, and fol-
lowing the same direction, as the portio dura,  but passing to a much
greater depth into its substance.   The other winds round  the corpus
restiforme, not penetrating it, but simply adhering to its surface, until
it reaches  the floor of  the  fourth ventricle, where it  connects  itself
"with the  olivary columns, and in  many instances is  evidently con-
tinuous with the white striae on either side  of the calamus scriptorius,
which for that reason have been  very generally regarded  as fascicles
of origin of the portio mollis.
   The portio mollis, when  contrasted  with the other nerves of the
medulla  oblongata, is  remarkable  for its delicacy  of structure, a
character which  had attracted the attention of the older anatomists,
and  by reason  of which they had  given  the  nerve  the  appellation
" mollis."  It  has  but a very delicate neurilemma, and its fascicles
are loosely held  together; it seems strictly a  direct  prolongation  of
the white matter of the  brain.
   The portio mollis enters  the internal auditory  foramen, and  there
forms a connection with the  portio  dura, by means of  a few fascicles
of fibres  which constitute the " portio intermedia" of Wrisberg.   It
is difficult to say whether this consists of fibres proceeding from the
auditory  to the facial nerve,  or from the latter to the former.   It  is
most reasonable to  suppose that the muscular nerve (the facial) sends
some  filaments into the labyrinth  to  the  blood-vessels, and to the
muscular structure of that portion of the ear.
   At  the bottom  of the meatus, the  portio mollis divides into two
branches, one to the vestibule and  semicircular canals, the other  to
the cochlea.
   The vestibular nerve  divides into three branches:—the  largest  is
uppermost, and  penetrates  the depression which is immediately be-
hind the  orifice of the aqueduct of Fallopius to be distributed to the
utriculus, and to the ampullae of the superior vertical and the  hori-
zontal semicircular canal.  The second branch  of the vestibular nerve
is distributed to the sacculus, and  the third to the posterior vertical
semicircular canal.
   The cochlear  nerve penetrates  the funnel-shaped depression at the
bottom of the auditory canal, and  proceeds from it through the nu-
merous foramina, by which its wall is pierced, in a spiral manner,  to
the lamina spiralis of the cochlea.
   The mode of distribution of  these nerves has been already de-
scribed.
   The labyrinth receives nerves from no other  source  than the portio
mollis, unless we suppose the portio intermedia to consist of filaments
from the facial which accompany the ramifications of that  nerve into
that part of the ear.
   That the portio mollis is the nerve of hearing is abundantly proved
by the following arguments:—1.  The distribution  of the nerve  to
the internal ear, to which  no other nerve of  any importance is dis-
tributed.   2. Its softness of texture and cerebriform character dis- 
462
INNERVATION.
 tinguish it from ordinary nerves of sensation or motion.   3. Diseased
 states of it, or of parts immediately near to its origin, affect the sense
 of  hearing, whilst a paralytic state of the portio dura or  of the fifth
 does not affect the sense.
   Of the  Nervous Apparatus accessory to the  Organ of Hearing.—
 Besides the auditory nerve there are others which influence the audi-
 tory apparatus.  These are  branches of the portio  dura,  branches of
 the nerve of Jacobson, from the glosso-pharyngeal, and from the otic
 ganglion.
   These nerves  present a striking analogy with  those which are dis-
 tributed to the eye.
   The tympanum receives branches from the facial, and glosso-pha-
 ryngeal, and probably from the sympathetic.
   The facial, in its passage through the aqueduct of Fallopius, gives
 off the chorda tympani, which, however, seems to have no physiolo-
 gical connection with  the tympanum or its contents.  The stapedius
 muscle receives  a branch from the facial nerve.   The anastomosis of
 Jacobson results from the subdivision of the tympanic branch  of  the
 glosso-pharyngeal  nerve, which enters  the cavity of the  tympanum
 below, and passing over the  promontory, gives off branches  to  the
 membranes of the  fenestrae, and Eustachian  tube, and  to  the otic
 ganglion.
   A  branch is  described  by  Arnold  as proceeding from the otic
 ganglion to the tensor tympani muscle.
   The external  ear is supplied by the  facial nerve as  regards its
 muscular apparatus, and by the fifth pair  as regards its sentient sur-
 faces.
   The influence of the facial nerve upon  the muscular apparatus of
 the organ of hearing, whether tympanic or  labyrinthic, is similar to
 that of the third  nerve upon the muscles of the eyeball, or upon  the
 iris and ciliary muscle.   And it seems probable that while volition
 can  exercise  a  certain  influence upon  the muscular  apparatus of
 hearing, that  apparatus may likewise be  excited  to action through
 the physical stimulus of sound affecting  the auditory  nerve,  which
 reacting upon  the portio dura excites its fibres  to  a degree propor-
 tionate to the intensity of the sound; as the stimulus of light affecting
 the optic nerve reacts upon the iris.
   We shall now proceed to inquire into the office of each part of the
 complex organ of hearing.*

  * The following points respecting the laws of sound should be borne in mind in
considering the offices of the various parts of that complex acoustic apparatus, the
human ear.
  1. Any irregular impulse communicated to the air will produce a  noise,- a succes-
sion of impulses occurring at exactly equal intervals of time, and exactly similar in.
duration and intensity, constitutes a musical sound.
  2. The frequency of repetition necessary for the production of a continued sound
from single impulses is, probably, generally not less than sixteen times in a  second,
but Savart thinks  that some ears may distinguish a sound  resulting from only ten or
eight vibrations in a second.  On the other hand, sounds are audible which  consist
 of 24,000 vibrations  in a second.
  3. Sound may be  propagated or conducted by air, gases, liquids and solids, with
various degrees of rapidity. 
THE EXTERNAL EAR.
463
   It is necessary for the  reader  to  bear in mind that the organ  of
 hearing may be affected in two ways: first, through the  external  ear,
 and  secondly, through  the bones of the head.  Every person  must
 '?Z* u°t!i    the dlfference in ^e sound of the ticking of  a watch if
 it be held near the ear  but not in contact  with it,  and if  it be held
 between the teeth.   The waning note of the vibrating tuning-fork
 seems  revived when the stem of the fork is brought  in contact with
 the teeth or with any part  of the  head.   These  differences are due
 to  the difference of the medium through which  the sonorous undula-
 tions are made to affect  the auditory  nerve.  In the  former instance,
 hearing is excited  through  the external ear, when the watch  is held
 near that  part, and  through  the  bones of  the head,  when the watch
 is brought into contact  with  the  teeth.   And  in the example of the
 tuning-fork, the  sound  appears to revive when it is made to affect
 the nerve through  a medium  (the bones of the  head) which more
 readily vibrates in  unison with the  most  delicate  oscillations of the
 sounding body.
    1. Of the External Ear.—The external ear consists of  two parts,
 the auricle,  and  the  meatus  auditorius externus.   The complete  de-
 velopment of the former is found  only in mammalia,  in which class
 it  exists pretty generally;  with,  however, considerable diversity  of
 form, varying from what appears  to be little more  than a mere carti-
 laginous lamella  with a  few irregularities upon its surface, enjoying
 scarcely any motion, to an elongated funnel-shaped ear-trumpet, very
 moveable, and completely under the control of numerous  large mus-
  4. Sound travels through air at the  temperature of 62° Fahr.,  at the  rate of  1125
 feet in a second.
  5. Sound is incapable of transmission through a vacuum.
  6. The propagation of  sound is the  more effectively performed as the medium  of
 transmission is more dense.   Rarefied air, gases of  low density, and soft solids, are
 less perfect conductors of sound than much denser materials of the same kind.
  7. We distinguish in sounds, 1, the pitch,- 2, the intensity or loudness; 3, the Quality
 or timbre.                                                        i    a
  The pitch of the sound depends on the rapidity with which  the vibrations succeed
 each other, and any two sounds produced by  the same number of vibrations or im-
 pulses in the same time, are said to be in unison.
  The loudness or intensity depends upon the violence and extent of the primitive
 impulse.
  The quality is supposed by Herschel to depend  on the greater or  less abruptness
 of the impulses; or generally on the law which regulates the excursions of the mole-
 cules originally set in motion.
  8. The velocity with which sound travels  is, however, quite  independent of its
 intensity or of its tone; sounds of every pitch, and of every quality, travel with the
 same speed through the same medium, as is  proved by the fact, that distance does
 not  destroy the harmony of a rapid piece of music played by a band.
  9. Water propagates sound with much  greater velocity than air does. Colladon
 concludes, from numerous observations, that the velocity of sound in water, at 40°
 Fahr., was at the rate of 4708 feet in a second.
  10. According to Biot, cast-iron  propagates sound at the rate of 11,090 feet in a
 second.
  11. Sonorous undulations,  in passing  from one medium to another, always ex-
perience a partial reflection, and  when they encounier a fixed obstacle, they are
almost wholly reflected.   The reflection of sound occurs  according to the same law
which regulates the reflection of light,—namely, the angle of reflection is equal to the
angle of incidence.
  12. The phenomena of echoes result from the reflection of sound from any promi-
nent object. 
464
INNERVATION.
cles.   Man and the quadrumana are at one extremity of this scale;
the solipeds, the ruminants, and the bats at the other.
   That the auricle performs the office of an  acoustic  instrument to
collect and reinfoVce the sounds which fall upon it, cannot be doubted
in those cases  in which it is large  and fully developed, as in the
horse, ass, &c.   These  animals employ it  as we might expect  such
an instrument would be used ;  the open part is directed towards the
quarter whence the sound comes, and continues  so directed as  long
as the animal appears to listen.
   Savart's experiments  illustrate the  manner in which an instrument
like  the external ear may contribute to the propagation of  sound to
the internal ear.  When a thin  membrane is stretched  in a horizontal
direction over the mouth of a glass or other hollow vessel, it may be
made to vibrate by holding near it a glass thrown into vibration by
passing  a  violin bow across it.   The vibrations  of  the paper are
easily demonstrated  by the movements of  particles of fine sand, or
lycopodium powder strewed upon it.   The sand arranges itself into
certain very definite  figures, the shape of which is determined by the
position of the  lines of repose, or nodal  lines, over which  the  sand
accumulates.  These phenomena may be shown in  the membrana
tympani itself, by scattering a little sand upon it, the osseous meatus
having  been previously cut away.   When  the  vibrating  glass is
brought near to it, the movement of the particles of sand affords suffi-
cient  evidence of the vibration excited in  the tympanic membrane,
but owing to the slight  extent  of the  membrane it is impossible to
determine the existence of any nodal line.
   Savart imitated the tympanic membrane,  and the external auditory
apparatus by a  hollow cone of paste-board; across  the narrow ex-
tremity some thin paper was stretched.  When  the vibrating glass
was  brought near to the narrow end, movements of a slight  kind
were  excited in the paper, but when the  glass was brought  to the
wide  extremity  of  the cone, much more extensive movements were
excited in the paper;  although now the glass was much more distant
from the paper than previously.
   This result  might have been  due chiefly to one  of two causes,
namely, either  to the concentration of the  sonorous undulations by
the walls of the cone, or to the excitation of vibrations in the walls
of the tube, which would be propagated directly to the paper;  and
Savart showed  by the following  simple  experiment  that the latter
cause was obviously the most effective.  He prepared a second conical
tube open at both  ends, and  having placed the narrow end  of this
tube very near the paper on the former one, but not in contact with it,
he found that vibrations were excited  on  the paper by bringing the
vibrating glass near to the wide  end of the second  tube, but  that
these  vibrations were not  nearly so extensive as when the glass was
brought near to the wide extremity of the tube with which the paper
was connected.
   Hence Savart inferred that the external ear and meatus were parts
adapted to enter into vibrations in unison with those of the  air,  or of
any liquid or solid vibrating medium which might be brought in  con- 
OFFICE OF THE TYMPANUM.
465
 tact with the auricle; and he suggested that the latter part, in the
 human subject, by the variety of direction and inclination of its sur-
 faces, could always present to the air a certain number of parts whose
 direction is at  right angles with that of the  molecular movement of
 that fluid, and therefore in the most favourable circumstances for en-
 tering into vibration with it.
   We get a general notion  of the  value of the external part of the
 auditory apparatus in collecting and directing the sonorous undula-
 tions, from the assistance often derived  in  hearing  by placing the
 hand behind the external ear, so as to increase its concavity;  and by
 the dulness of hearing, which it  is said follows the loss of the auricle.
 Kerner states that the loss of the auricle is followed  by the greatest
 dulness of hearing in those  animals in which the osseous meatus is
 wanting.   In a cat from which the right ear was cut away close to
 the skull, after  the wound had  healed  without  any stoppage of the
 meatus, there was  a  remarkable disposition always to keep the head
 turned so as to be ready to receive  sounds with the left  ear, and this
 continued even after the left  tympanic membrane was perforated, the
 right remaining whole;  and when the left ear was stopped, (although
 the right tympanic membrane was sound, and the only injury on that
 side was the removal of the auricle,) a total deafness was manifested
 except to the loudest and clearest sounds.
   The Tympanum  and  its Contents.—We have  already stated  that
 Savart had demonstrated experimentally upon the membrana tympani
 itself, that that membrane can be thrown  into vibrations by undula-
 tions of the air excited by a sonorous body.   In a second experiment,
 the cavity of the tympanum was opened, so as to expose the ossicles
 of the ear and their muscles; and it was observed that when  the in-
 ternus mallei muscle acted and rendered the membrane tense, it was
 much more difficult to produce manifest movements in the  grains of
 sand;  thus affording much reason to suppose that the tensor tympani
 muscle is analogous in its use to the iris, and destined to protect the
 organ from too strong impressions.   These experiments  can  be best
 tried on the membrana tympani of the calf.
  In imitation of the mechanism by which the tension of the mem-
 brana  tympani is effected, and  with a view to
 determine  more decisively the  effects  produced        Fig-145.
 by variation of the tension of that membrane,  Sa-         ™
 yart constructed  a  conical tube (fig. 145), with
 its apex truncated and covered by a layer of very
 thin  paper, m, which was glued to the edge of
 the opening.  A little wooden lever, I, I, intro-
 duced  through an opening in the side of the tube,
 and resting on the lower margin  of  this opening,
 c, as a fulcrum, was used to vary the tension of the
 membrane, one of its extremities being applied
 to the under surface of the membrane.   By depressing the extremity
 of the lever external to the tube, the inner one is raised, and thus the
 membrane  stretched to  a greater or less degree, according  to the
force used;  on the other hand, by elevating the outer extremity, the
 
466
INNERVATION.
inner one is separated from the membrane, which is accordingly re-
stored to its original  tension.   This little lever is an imitation of the
handle of  the  malleus, which, under the influence of its  muscles,
causes the variation in the tension of  the  membrana tympani.   The
artificial tympanic membrane having been  then covered with a layer
of sand, it  was found, that, under the  influence of a vibrating glass,
used as in  the former experiments, a manifest difference was  pro-
duced in the movements of the grains  of sand, by increasing the ten-
sion of  the paper; the greater  the tension, the  less the height to
which  the  grains of sand were raised'; and these  movements were
most extensive when the lever was withdrawn from  contact, and  the
membrane  left to itself.
  From these  experiments Savart concludes that the membrana tym-
pani may be considered as a body thrown  into vibration by the air,
and always executing vibrations  equal in  number to those of  the
sonorous body which excites  the  oscillations of the air.   But what
is the condition of the ossicles of the tympanum whilst the membrane
is thus in vibration?   The result of the following experiment affords
a clue to the answer to this question.  To a membrane stretched over
a vessel, as in fig.  146, a  piece of wood, a, b, uniform in thickness,

        Fig. 146.                                Fig. 147.
is attached, so that the adherent part shall extend from the circum-
ference  to the centre of  the  membrane, while  the free portion  may
project beyond the circumference.  When a vibrating glass is brought
near this  membrane, very  regular figures are  produced, modified,
however, by the adhesion of the piece of wood, and the vibrations of
the membrane  are communicated to the wood, on which likewise
regular figures may be produced.   The more extensive the membrane,
the longer and  thicker may be  the piece of  wood  in  which it can
excite oscillations, and Savart states that, with membranes of a  con-
siderable diameter, he has produced regular  vibrations in rods of
glass of large dimensions.  The oscillations of the piece of wood are
much more distinct when the adherent portion  is thinned  down, as
in c, d, fig. 147, by which it becomes more completely identified  with
the membrane; the oscillations of this  latter are communicated di-
rectly to the thinned portion of  the wood, and thence propagated to
the thick portion, a: sand spread upon a will  exhibit active move-
ments, and will indicate very distinct nodal lines.   Hence it may be
inferred that  the  malleus participates in the oscillations of the  tym-
panic membrane; and these vibrations  must be propagated to the
incus and stapes, and thus to  the membrane of the fenestra ovalis.
The chain of ossicles then evidently performs the office of a conductor
 
SAVART'S EXPERIMENTS.
467
of oscillations from  the  membrana tympani to the membrane of the
fenestra ovalis; but the malleus likewise has the important function
under  the influence of its  muscles of regulating the  tension of the
tympanic membrane; and to allow of the changes in  the position of
this  bone necessary for that purpose, we find  it articulated with the
incus by a distinct diarthrodial joint, and  between this latter  bone
again and the stapes there exists another and  a similar  joint.   This
mobility then of the chain of bones, and the  muscular apparatus of
the malleus and stapes have obvious reference to the regulation of
the tension of the membrane of the  tympanum as well  as of that of
 he fenestra ovalis.
   We have already seen how the muscle of the malleus  regulates the
membrana tympani, increases its tension, and  thus limits the extent
of the excursions of its vibrations.  The contraction of the stapedius
muscle  causes the base of the stapes to compress the membrane of the
fenestra ovalis to a greater or  less extent,  so that the degree of ten-
sion of that membrane  depends  on the condition of  this muscle.
Compression exerted  upon the  membrane  of the fenestra ovalis ex-
tends to the perilymph, and through it is propagated to the membrane
of the fenestra rotunda, and in this way the same apparatus which
regulates the tension of the membrane of the fenestra ovalis performs
that office for that of the fenestra rotunda, and Savart  has devised an
apparatus  which  very prettily  illustrates the  manner in which this
may take place.  In a disc of  wood (a,
b, fig.  148)  of sufficient thickness,  he
hollows out two cavities, o and  r, which
communicate at their bottoms with each
other by a narrow canal (c) hollowed in
the wood, but not open  on its surface;
a thin  membrane is extended over each
of the cavities.   Thus, the air contained
in these cavities  may pass easily from
one  to the other, and may always maintain the  same degree of elastic
tension in both.   If a  vibrating glass be brought near the membrane
r, covered with a layer of  sand, it will  be  found to enter  freely into
vibration, as evinced by the active movements of the grains of sand.
If, now, pressure be made on o with the finger, r will become convex
in proportion as o is rendered concave by the pressure, and when in
this  convex state, the movements of  the sand  upon it will  be  much
less  considerable than before, presenting an effect precisely similar to
that produced on  the tympanic  membrane by an increase of tension.
Thus, the  extent of the excursions of the vibrations of the membrane
r, is limited by the pressure exerted upon  o, and as the membranes
of the two fenestra? are related to each other in an analogous manner,
we may argue that pressure upon the  membrane of the fenestra ovalis
will  occasion tension of that of  the fenestra rotunda, thereby limiting
the extent of the excursions of its vibrations.*

  * All these experiments have been frequently repeated  and exhibited by us, with
the same results as those stated in the text.
 
468
INNERVATION.
  Moreover it appears, upon reference to the anatomy of these parts,
that  the  only muscles which  have been  satisfactorily demonstrated
are tensors of the tympanum; and that at whichever extremity of the
chain of ossicles muscular effort  be  first exerted, a corresponding
effect will be produced at the  other; that when the stapedius muscle
acts, the  malleus is thrown into a position favourable to the tension
of the membrana tympani,  and, on the other hand, the contraction of
the  internus  mallei depresses  the stapes, and consequently increases
the tension of the membranes of the two fenestras.   The cessation of
muscular action restores all three membranes to  their original laxity,
nor does  it appear that they admit of any further  degree of relaxation
through the  influence of  any vital process.   The incus forms a bond
of union between  the two other bones, and  its  motions depend  en-
tirely upon theirs in consequence of its articulation with  both, while
from the  fixedness of its connection with the mastoid cells, as well as
from its  intermediate position and want of  muscular attachment, its
motions must obviously be  much more limited than those  of the other
bones.  Its use seems to be to complete the chain in such a manner,
that by reason of its double articulation with  the malleus on the  one
hand and the stapes on the other, the  tension of  the tympanic mem-
branes may be regulated without any sudden  or violent motion, which
could scarcely be avoided were the conductor between the membranes
of the tympanum and  fenestra  ovalis but one piece of bone.
  The mobility of the tympanic bones has, however, a further use, as
Muller suggests; namely, to favour the oscillations of the membrana
tympani, by allowing the approximation of the two extremities of the
chain of bones.  And this opinion is strengthened by  the facts of
comparative anatomy, for the ossicles  have moveable articulations in
the frog, as in man, although they have no muscles attached  to them.
  The addition of a cavity filled with air outside the labyrinth has a
twofold use.   First, to preserve uniformity of temperature in the air
immediately in contact with the fenestral membranes.   Were these
membranes situate on the exterior of the  head, and exposed to the
surrounding atmosphere, they would be constantly undergoing changes
in their elastic state, under the influence of atmospheric vicissitudes.
The air which accumulates in the tympanum and mastoid cells, finds
its way into them only through the Eustachian tubes, and as it  does
not readily change its position, it is well placed for maintaining a
temperature equal to  that of the body.  Secondly, the action of the
chain of  ossicles as conductors is materially enhanced by their being
completely surrounded by air.  The insulation of a  solid body by a
different  medium renders it a better propagator of sound ; for the sur-
rounding medium will obviate the  dispersion   of sound,  and  will
favour its retention in the solid conductor.
  It results from Savart's experiments, that  tension of the membrana
tympani  is unfavourable generally to the  propagation of sounds, es-
pecially of those of a low pitch.  By rendering the membrana tympani
tense in one's own person, the correctness of this statement may be
readily ascertained.   In  blowing the nose forcibly, air is forced  into
the tympanum, and its membrane is rendered convex and tense, and 
USE OF THE TYMPANUM.
469
every one must have experienced the temporary deafness which re-
mains  after such an effort.   The tympanic membrane may also be
rendered tense by forced inspiration, the nose and  mouth being kept
shut.   Under these circumstances the tympanic cavity is exhausted,
and the membrane rendered tense by the pressure of the external air.
  In descending in the diving bell,  the membrane of the tympanum
is rendered painfully tense by the increased pressure  of  the air, and
the want of counter pressure  from within.   This tension may be so
great as even  to cause rupture of the tympanic membrane  in  some
cases, but  it  may be obviated by acts of swallowing, during  which
the external air is driven into the tympana along the Eustachian tubes.
During the tense  state of the  membrane, hearing is  impaired; M.
Colladon found that the voices of his companions and of himself were
not so distinctly heard.
  Dr. Wollaston  performed  many experiments upon  the effects of
tension  of the  membrana tympani, and he found that  deafness to
grave  notes was always induced, which, as most ordinary sounds
are of a  low pitch, is tantamount to a  general  deafness.  Shrill
sounds, however, are best heard when the tympanic membrane is
tense.   Muller remarks, and we have  frequently made the same ob-
servation, that the dull rumbling sound  of carriages  passing over a
bridge, or  of the firing of cannon, or of the beating of drums at a
distance, ceases to be heard immediately on the membrana  tympani
becoming tense; while the treading of horses upon stone pavement,
the more shrill creaking of carriages, and the rattling of paper, may
be distinctly heard.
  The object of the  Eustachian tube  is chiefly to  allow the free in-
gress of air into the tympanic cavity, in order to provide for the due
vibration  of the membrana tympani and of the chain of bones.  It
also, by permitting a free egress of air, renders the tympanum a non-
reciprocating cavity, and  therefore obviates the production of echoes
in  it, which would materially interfere  with perfect  hearing.  The
importance of the Eustachian tube to the integrity of  hearing is well
known to all  practical  men, by the deafness which always accompa-
nies chronic or acute disease of the tonsils, or occlusion of the canal
of that tube from any other cause.
   The idea of Boerhaave, and of Bressa,  that sounds from without
which enter the mouth, or the sounds of one's own voice, were con-
ducted by the Eustachian tube to the  labyrinth, is disproved  by the
simple experiment of holding a sounding tuning-fork or a watch in
the open mouth, when it will be always found, if due care be taken to
avoid contact, that the  sounds proceeding from them are  not so well
heard as those from without, and the nearer they are  brought to the
Eustachian tube the less distinctly are  they heard.   Indeed it may be
always noticed that persons deaf from obstruction  of the Eustachian
tube'hear the sounds of their own voices well.
   Of the Labyrinth.—The essential part of the organ of hearing is
the vestibule.   This is sufficiently proved by the constancy  of this
part in the animal series, and  by its central  position in  the most com- 
470
INNERVATION.
    plex ears, so that it is in close relation  not only with the other parts
    of the  labyrinth, but also with the tympanum.
      Sound is conveyed to the labyrinth in a threefold manner: first, by
    the chain of  bones;  secondly, by the air in the  tympanic cavity; in
    both these instances the external air is engaged in the conduction;
    and thirdly, through the bones of the head.
      Muller has shown, by  a very interesting experiment, that, whilst
    the air in the tympanum conducts sound  to the cochlea through the
    fenestra  rotunda, the chain of bones forms a much better conductor
    of  it to  the vestibule through the fenestra ovalis.   He  imitated the
    structure of the tympanum by means of a glass cylinder, two inches
    and one-third in  diameter, and six inches long; to the neck of this
    he  fixed  a wooden tube, the diameter of whose bore was eight lines.
    The upper end of this tube was adapted to the mouth of the metal
    flute-pipe of an organ, one foot  in  length; its  lower extremity was
    covered  with a tense membrane of pig's bladder, which  represented
    the membrana tympani, the  tube itself corresponding to the  meatus
    externus, and the cavity of the glass  cylinder to the tympanum.  The
    lower  opening of the  glass  cylinder was closed by a thick piece of
    cork, in  which two holes were cut equidistant from the walls of the
    cylinder.  In these holes, which represented the fenestra, two wooden
    tubes were fitted, whose outer openings were covered with membrane.
    From the membrane of the upper tube to one of these membranes, a
    rod was  extended to  imitate the chain of tympanic bones extending
    between the membrane.
      The lower extremity of this apparatus  (that, namely, which was
    fitted with cork) was now  introduced into water, to imitate the con-
    nection between the tympanum and  the labyrinth in which sound is
    conducted from air to liquid.   Muller, having plugged his ears, could
    by  means of a sounding-rod applied in succession to the membrane
    of each of the artificial fenestra, ascertain the relative intensity of the
    sonorous vibrations communicated to the water through the two open-
    ings,  while another person sounded the' pipe.   He states that the
    difference was very striking.   The sound transmitted by the wooden
    rod to the opening which  represented the fenestra ovalis, was in a
    remarkable degree louder than that propagated through the air of the
    cavity to the membrane of the other  opening.
      The results of this experiment lead to the conclusion (which other
    circumstances confirm), that the vestibule is adapted to receive sounds
    from the tympanic membrane and  external ear,  while the cochlea is
    not easily affected in  this manner,  but rather,  as  its  structure and
    connections point out,  that it is  fitted to  receive vibrations through
*   the bones of the head.
      The direct continuity of the walls  and the septum (lamina spiralis)
    of  the cochlear canal,  with the  petrous bone, and the minute subdi-
    vision of the nerve in distinct canals in the osseous substance, render
    that portion of the labyrinth most readily affected by the vibrations
    excited in the cranial bones.   The cochlea may therefore be properly
    considered as that part of  the' labyrinth which is  more immediately
    affected by sounds communicated through  the bones of the head, as 
OF THE LABYRINTH.—THE OTOLITHS.
471
the vestibule is the part primarily affected by the sounds communi-
cated through the external ear.
   It may be easily shown by some experiments with the tuning-fork,
not only that the  cranial  bones do  conduct, but  also that sounds
inaudible, or imperfectly audible, through the meatus externus, may
be distinctly heard when the sounding  body is brought into contact
with a bone of the cranium or face.   When the tuning-fork is thrown
into vibration by striking it against any solid body, if held near the
external ear its vibrations are distinctly heard, but let the stem be
applied to  the teeth, or to the upper jaw, or to the parietal bone,
and the sound appears much louder;  or if the fork  be held near the
ear until the sound has almost died away, and then its stem be ap-
plied to the superior  maxilla, or to the  teeth, the sound seems to
revive, and  continues for a considerable period while the  stem is
kept in contact with the bone.
   The form of the cochlea probably has reference to  the  convenient
package within the smallest  compass of  the great number of nerve
fibres which proceed to it.
   The remarkable subdivision which the cochlear  nerve  undergoes,
admirably  adapts  it for the reception of vibrations communicated
through the cranial bones.  "The spiral lamina of the cochlea," says
Muller, "must be regarded as a surface upon which all the fibres of
the cochlear nerve are spread out, so as to  be nearly simultaneously
exposed to the impulse of the sonorous undulation, and simultaneously
thrown into the maximum state of  condensation, and again  into the
maximum state of rarefaction."  "This spreading  out of the nerve
fibres upon  the lamina spiralis, insures a more complete participation
of the fibres in the impulses communicated by the  solid  parts of the
cochlea."   Moreover, "the  intensity with which  sonorous  undula-
tions are communicated to a body, is proportionate to the extent of
 surface over which they can  act on  it.  Thus, when a sound is ex-
 cited in water, and  is conducted to  the stopped ear by  means of a
 rod, the intensity of the  sound  heard increases with the depth to
 which the  rod is immersed in the water, or with the extent in which
 it is in contact with the surface of the water."*
   The fluid in the scalae of the cochlea, with the helicotrema or orifice
 of communication, must facilitate the vibrations of the lamina spiralis,
 and we have already assigned to the cochlearis muscle a protective
 use to the  cochlear nerves.
   The Otoliths.—The  earthy particles, which, either as  pulverulent
 masses, or as hard porcelainous stones, are connected with the nerves
 of the  membranous labyrinth, must reinforce  the  sonorous undula-
tions, and communicate to the membranous labyrinth and its nerves
 vibratory impulses of greater intensity than the perilymph  alone could
 impart.   In illustration of this, Muller  mentions  that sonorous undu-
 lations in water are not perceived by the hand itself immersed  in the
 water, but  are felt distinctly through  the medium of a rod held  in the

   * Muller's Physiology, by Baly, vol. ii. p. 1294.  Dr. Young regarded the cochlea
 as a micrometer of sound. 
472
INNERVATION.
hand.  The experiment of Camper is also illustrative.   Fill a bladder
with water and  place a stone or some other hard  body in  it.   The
slightest  impulse communicated  to  the bladder disturbs the stone,
which consequently produces  a greater impression on  the  hand by
which the bladder is supported.
   The Semicircular Canals.—There is  nothing known of the function
of the semicircular canals.  Yet their almost constant existence, and
nearly constant number evince their physiological importance.  In
most cases of congenital deafness they are found defective.
   Their constancy in the higher animals of  number, and of position,
which is such that they correspond to the three dimensions of a cube,
its length, breadth, and depth, suggested  to Autenrieth and Kerner
the opinion that they are the parts concerned in conveying  a know-
ledge of  the direction of sounds, a view which  is also advocated by
Wheatstone.   The latter  philosopher  conceives that we distinguish
best the  direction of those  sounds which are sufficiently intense to
affect the bones of the head, and that  it is from  the vibrations which
are transmitted through these bones that our perception of the direc-
tion is obtained.   The  three  canals being situate  in  planes at  right
angles with each  other are affected by the sounds transmitted through
the bones of the head with  different degrees of intensity, according
to the  direction in which the sound  is transmitted; for instance, if
the sound be transmitted in the plane of any one canal, the nervous
matter in that canal will be more strongly acted on than that in either
of the other two;  or if  it  be  transmitted  in the plane intermediate
between the planes of this canal and  the adjacent one, the relative
intensity  with which  those two canals will  be  affected will depend
upon the direction of the intermediate plane.   The direction suggested
to the mind will correspond with the position of the canal upon which
the strongest impression has been made.
   There  are remarkable differences in  the range of the sense of hear-
ing in different individuals, analogous to the differences in the power
of vision  with  regard to  colours.  Some persons  are  insensible to
certain sounds, which are  familiar to other ears, as some are unable
to see particular colours.  The limits of audition in different indivi-
duals may partly depend on  the condition  of the auditory nerve, and
partly upon the size of the membrana tympani.  It is  probable that
animals with very large membranae tympani can hear  much graver
sounds than man.  The artificial  tension of  the membrana  tympani,
alluded  to at  a former page, is capable of inducing insensibility to
sounds of a  grave  character, as Dr. Wollaston has shown.   The
ordinary range of human hearing comprised between the lowest notes
of the organ, and the  highest known cry of insects, includes, according
to Wollaston, more than nine octaves, the whole of  which are dis-
tinctly perceptible by most ears.  Dr. Wollaston has, however, related
some cases in which  the range was much less, and  limited as regards
the perception of high notes; in one individual,  the sense of hearing
terminated at a  note four octaves above the middle e of the piano-
forte; this  note  he appeared  to  hear rather imperfectly, but the r
above it was inaudible, although his hearing in other respects was as 
THIRD PAIR OF NERVES.
473
perfect as that of ordinary ears; another case was that of a lady who
could never hear the chirping of the  field cricket;  and in a third
case the  limit was such  that  the  chirping of the  common  house-
sparrow could not  be heard.   Dr. Wollaston supposes that inability
to hear the piercing squeak of a bat is not very rare,  as he met with
several instances of persons not aware of such  a sound.
   Every one must be conscious that the sensation of sound frequently
lasts longer than the exciting  cause  of it, as  the sensation of light
does.  This has been  demonstrated experimentally  by Savart, who
found in his experiments  upon toothed wheels that  the removal of
one  tooth  did not  produce any  interruption of the sound.   Other
proof of this is  obtained from  the  noise which remains in the ears
after long travelling in a coach, or  in a train upon a railroad.  The
subjective phenomena  of hearing generally result from  some affec-
tion of the brain, or of that part of it in which the auditory nerve is
implanted.  The most common of them are tinnitus aurium, and the
buzzing or rushing noise in the ears, which is generally indicative of
a  deficiency rather  than a  redundancy of blood in the  brain;  or it
may be caused  by some disturbance of local nutrition of the brain
giving rise to an irregular development of nervous power.

  Upon the subjects discussed in this chapter, the reader may consult the works of
Scarpa and Soemmering; the excellent article on the organ of Hearing by Mr. Whar-
ton Jones in the Cyclop, of Anat.; Muller's elaborate chapter on Hearing in his Phy-
siology; Dr. Wollaston's paper on Sounds inaudible by  certain ears, Phil. Trans.,
1820; the article Hearing, Cyclop. Anat.; Dr. Elliotson's  Physiology, where the in-
genious views of Mr. Wheatstone are briefly stated; and a paper by the latter phi-
losopher in the Journal of the Royal Institution, for July,  1827.
                        CHAPTER  XIX.

ENCEPHALIC NERVES EXCLUSIVELY MOTOR  IN FUNCTION.--THE THIRD
   PAIR OF NERVES.--THE  FOURTH  PAIR.--THE  SIXTH  PAIR.--THE
   PORTIO DURA OF THE SEVENTH PAIR.--THE NINTH PAIR.

   The nerves which we shall consider  in this  chapter are purely
motor  in  their  function;   and,  on this  account, are  conveniently
classed together.  We shall see, however, that from their occasional
anastomosis with  sensitive  nerves, they  contain sentient  filaments
which  serve to inform the mind of the state of  the muscles  to which
their motor filaments are distributed.
   The  Third Pair  of Nerves, or Motores  Oculorum.—These nerves
are connected with the crura cerebri.   Each nerve emerges from the
corresponding crus, on the side of  the locus perforatus posticus, or
pons Tarini.
   When traced into  the  substance of the  crus, the  component fas-
ciculi of each nerve are seen to diverge from each other, and to sink
     31 
474
INNERVATION.
into the dark vesicular matter constituting the locus niger.   Here, no
doubt, the filaments  connect themselves with the vesicles of this
mass of gray matter.
  Each nerve proceeds  forwards and outwards, and passes through
a canal in that portion of the dura mater which forms the outer wall
of the cavernous sinus into the orbit through the spheno-orbital fora-
men, and just as it has reached this foramen  it  divides into a superior
and an inferior branch, the distribution of which is shown in the fol-
lowing table :
  .  0    .   v ■ •   ( 1. i.  To the levator palpebra; superioris.
  A. Superior division, j 2< fi>  To (he superiorHre^tus ocu&
                  f 1. b.  To the internal rectus.
                  j 2. b.  To the inferior rectus.
  B. Inferior division.-^ 3. b.  To the inferior oblique.
                  | 4. b.  To the ophthalmic ganglion, also called the short root
                  l_       of that ganglion.

  The anastomoses of  the  third nerve  take  place  entirely in that
stage  of  its course in which it lies in the outer wall of the cavernous
sinus.   They are with the ophthalmic division of the fifth  nerve, and
with  the  carotid branch  from the inferior  cervical  ganglion  of the
sympathetic;  and, as has been asserted by a few anatomists, with the
sixth  nerve.
  Function of the Third Nerve.—Proceeding according to the method
indicated at  page 303, vol. i., we deduce the function of this nerve
from its anatomy in  man, from its anatomy in  animals, from experi-
ments, and from pathological observation.
  From  its  anatomy in  man  we judge  this nerve to be a motor
nerve, for it  is distributed entirely to muscles.   These muscles are,
in addition to the elevator of the  upper eyelid, those upon which the
principal  movements of  the eyeball depend  ; indeed, all the muscles
of that organ, except the superior oblique  and  the  external rectus.
In addition to these there can be no doubt that the third nerve  sends
filaments to the  muscular  apparatus within  the eye by the short root
of the ophthalmic ganglion, which, after passing through that gan-
glion, escapes from it under the  form of ciliary nerves, which may
be traced to the ciliary muscle  and to the iris.   It is, therefore, the
principal motor nerve of the eyeball, regulating all the movements of
that organ, excepting those which depend on  the external rectus and
superior oblique muscles;  and it also probably excites the  movements
of the iris and  of the other  muscular fibres within the eye.   Upon
this latter point, however, anatomy speaks  less positively, from the
fact that other nerves are distributed to  the  iris besides those derived
from  the third.
   The distribution of the third  nerve, in the inferior animals, leads
to the same conclusion respecting its function, as that which we have
deduced from human anatomy.   In all the mammalia it is distributed
to  the same muscles of the eyeball as  in man, and to  the iris.   In
birds a similar arrangement exists,  and in some species of  this class
we observe a remarkable development of that branch which is dis-
tributed to the  iris  in  direct relation with  the  muscular activity of 
FUNCTION OF  THE THIRD NERVE.             475
 that structure.  In the falcons and eagles, according to Desmoulins,
 the third nerve is  absolutely as large as in  man, and this great  size
 is due  to the development of the branch which is distributed to^the
 iris and ciliary muscle.
   Experiments on  this nerve are  difficult  of execution, and  their
 results are therefore not free  from complication ;  but such  as  have
 been obtained  entirely confirm the view of its function which ana-
 tomy suggests.   These results, as derived from the experiments of
 Rumbold  and Fowler, of Mayo, Valentin and others, may be  sum-
 med  up as follows:
   The application of the galvanic current to the nerve causes a con-
 vulsive contraction of the principal muscles of the globe and of the
 iris.   The same effect is produced by mechanical irritation of the
 trunk of the nerve.
   Section of the trunk of the third  nerve  in rabbits or dogs, gives
 rise to  external  strabismus with paralysis of the upper  eyelid  (ptosis),
 and dilatation and immobility of the pupil.   The eyeball is given up
 to  the  influence of  the external rectus  and  of the  superior oblique
 muscles, the former of which, being the more powerful, determines
 its permanent position.
   The paralysis of the iris, after section of this nerve, is so complete
 that the most powerful light, directed  into  the eye, is incapable of
 exciting the  least contraction of the pupil. And Mayo's experiments
 demonstrate  that the fifth nerve, which is the only other, except, per-
 haps, the  sympathetic, connected with  the  iris, does  not  exert  any
 motor influence  upon that membrane.
   When the optic nerve is  irritated, the third remaining intact,  and
 retaining its connection with the brain,  the  pupil contracts.  This
 action  does not take place if the third nerve  have been previously
 cut.  The motor action of the third nerve may, therefore, be excited
 through the optic  nerve.   There  can be no  doubt, indeed, that  this
 is the ordinary method  by which  contraction of the pupil is produced
 during  life; the stimulus of light falling upon  the retina excites the
 optic nerve, and, through  it, that portion of the brain in which  the
 third  nerve is implanted.
   The  effects produced by pathological changes affecting the third
 nerve, or that part  of  the brain  with which  it is connected, are in
 exact accordance with the  results  derived from experiment.
   Paralysis of the levator palpebra superioris muscle, permanent
 squinting of the eyeball in the outward direction, and a dilated, mo-
 tionless pupil  are  the  unerring signs of a paralytic lesion affecting
 the third nerve either  at its  central extremity  or in some part of its
 course.
  The third nerve may, therefore, be stated to be  the nerve of mo-
 tion to the  elevator muscle of the  upper lid, and a principal nerve of
 motion  to the eyeball, and  to the  muscular apparatus within the eye.
 It is a nerve  of  great  importance to vision, not only from its influ-
 ence over  the  eyeball  itself, but also from its connection with  the
 muscular structures in the interior, on which the power of adjustment
probably depends. 
476
INNERVATION.
   Of the Fourth  Pair of  Nerves.—These, which were  called by
Willis ilnervi pathetici," are the smallest of the encephalic nerves.
Thiy are  also remarkable for the very long course which they take
from their origin to their point of exit from the cranium.
   The origin of the fourth nerve may be referred to the mesocephale,
from the superior  surface of which  it  emerges, in close connection
with the  testes,  or immediately behind  them.   Its true  origin is
doubtless from the olivary columns  as they extend upwards beneath
the quadrigeminal tubercles.
   The fourth nerve emerges from the cranium through a canal in the
dura mater, situate near the posterior clinoid process of the sphenoid
bone, external to that in which the third nerve is lodged.  It passes
along the outer wall of the cavernous sinus beneath the  third nerve,
and in entering the orbit it rises above that nerve, and lies immedi-
ately beneath  the  periosteum, attaching itself to the orbital surface
of the superior oblique muscle, into the  posterior  third of which it
penetrates.
   This is the  only muscle which the fourth  nerve  supplies, and  the
nerve appears to  be wholly lost in  it.  But as it passes through its
canal in the dura mater, it gives off  a branch, which, taking a retro-
grade course, passes into the tentorium cerebelli as far as the lateral
sinus, where it subdivides into two or three filaments.
   In its  course it forms but few connections,  and those apparently
not constant.  As it crosses the cavernous sinus it anastomoses with
the sympathetic, and, as it  enters the orbit, with the lachrymal.
   That this nerve is  the motor nerve to the superior oblique muscle
anatomy does not  allow us to  doubt, for the muscle  receives no
other.
   Experiments and pathological  observation have thrown no satis-
factory light upon  its function.
   In animals of great power of expression,  as in  apes, according to
Sir C. Bell, this nerve, as  well  as  the superior  oblique  muscle, is
large.
   Of the Sixth Pair of Nerves.—These nerves emerge from between
the fibres of the anterior pyramids immediately behind the posterior
margin of the Pons Varolii.   It is not improbable that the true origin
of each nerve is from  the  central part of the medulla oblongata, the
olivary columns, and that the nerves pass between  the fibres of the
pyramids without forming any real connection with them.
   The sixth nerve has a straight, but very short intracranial course;
it  penetrates the  dura mater,  and  passes over the outside of the
carotid artery, between it and the lining membrane of the cavernous
sinus, entering the orbit between the two origins of the  rectus ex-
ternus  muscle, to the ocular surface of which it is entirely distributed.
   As the sixth nerve is passing along the outer side of the internal
carotid artery, it forms a very celebrated  anastomosis with the sym-
pathetic, by means of  two large and distinct branches, and it some-
times anastomoses with the nasal branch of the fifth.
   Anatomy points to  the function of this nerve  as distinctly as  it
does to that of the fourth.   The sixth nerve ean have no other office 
THE FACIAL NERVE.
477
 than that of regulating the movements of the abductor muscle of the
 eye.   Experiment fully confirms this conclusion,  and a few cases
 have been  observed in which  internal strabismus was found to  ac-
 company compression of the nerve  by a tumor.
   Of the Facial Nerve.—(Portio dura of the seventh pair.)—This is
 one of the  most interesting and remarkable of the motor nerves.  Its
 close proximity to the auditory nerve led Willis to class it along with
 that nerve.  The former nerve is soft in its structure, and  its bundles
 loosely coherent; the latter is  more compact, and  surrounded by a
 neurilemma of  sufficient density to  give to it a power of resistance
 very superior to that of its neighbour.
   These two nerves lie in  a fossa situate on either side  of the medulla
 oblongata,  and  behind the posterior edge  of the pons, bounded on
 the  outside by a small lobule of the  cerebellum, called the flock by
 Reil, or the lobule of the vagus or of the auditory nerve;  the floor
 of this fossa is formed by the  restiform column.   The portio dura
 nerve,  which lies  inside  the portio mollis, penetrates the  restiform
 column, and through it  may be traced  to the central part of the me-
 dulla  oblongata, the olivary  columns,  where it  connects  itself with
 the vesicular matter.
   In examining the distribution of the facial nerve, it  will be found
 convenient  to  divide  it  into  three  stages,  and  to  enumerate its
 branches in each stage.
   The  first  stage is intracranial, from its origin to its exit  at  the
 internal auditory meatus.   In this stage  it forms a connection with
 the auditory nerve by the portio intermedia of Wrisberg, an  oblique
 branch of communication, which seems like a fasciculus  of fibres
 passing  off  from  the portio  dura,  and accompanying the  auditory
 nerve into the labyrinth.   This branch was described by Arnold and
 Goedechens as  a second root of the facial nerve, but inasmuch as it
 does not form a connection with the centre, distinct  from  that which
 the principal fibres of the nerve have with it, this view is not tenable.
 Regarding the  facial as a  motor nerve, this branch  may possibly be
 viewed, as conveying motor influence to the muscular apparatus of
 the cochlea, which we have discovered.
   The  second stage  is contained in the  aqueductus  Fallopii.  In its
 passage through this canal a gangliform swelling  is formed on  the
 nerve where it  is joined  by the Vidian which comes through  the
 hiatus Fallopii,  intumescentia genuformis.  A question arises  as to
 the nature of this swelling; is it a ganglion, or, is it  merely the result
 of the separation of the fibres of the  nerve  at this  situation?  We
 have failed  to  satisfy ourselves  by  microscopic examination  of  the
 existence of vesicular matter in it, but we have found a large  num-
 ber of gelatinous fibres in  it, as well as of tubular fibres.*
   At this swelling the facial forms a communication by means of  the
greater superficial petrosal  nerve with Meckel's ganglion, and  by  the
lesser superficial petrosal nerve, with  the otic ganglion; a third branch

  * Morgagni has  lately published an elaborate paper, in which he maintains the
ganglionic character of this swelling.—Annali Univ. di Medicina, 1815. 
478
INNERVATION.
less constant than these two, is distributed to vessels and dura mater
on the surface of the petrous bone.  As it lies in  the  aqueduct of
Fallopius, the facial nerve gives off the  following branches.  1. A
branch to the membrane of the  fenestra ovalis.  2. A twig to the
stapedius  muscle.   3.  The chorda tympani.  4.  An  anastomotic
twig with the auricular branch of the vagus nerve.
  The third stage commences at the stylomastoid  foramen ; here the
nerve passes obliquely through the  parotid gland, in the  substance of
which it  divides  into  its terminal branches.  Immediately on its
emergence from  the stylomastoid  foramen, it gives off:   1. The pos-
terior auricular,  or  auriculo-occipital, distributed to the small muscles
of the ear, and the  occipital muscle. 2. The stylohyoid branch to the
stylohyoid  muscle.   3.  The submastoid branch to  the digastric mus-
cle.   And lastly, it divides into two branches, the cervicofacial, dis-
tributed to the platysma, and to the  muscles of  the lower lip and
chin, and  the tmiporo-facial, which is  distributed  to the orbicular
muscle of the eyelids, the corrugator  supercilii, and the muscles of
the nose and upper lip.  The plexiform distribution of  these nerves
on the face  forms the well-known  pes anserinus.   The  facial nerve
anastomoses freely with the superficial  temporal, frontal, infra-orbital,
buccal and mental  branches of the fifth  pair, and with branches of
the cervical plexus.
  Function  of the Facial Nerve.—Referring to the anatomy of this
nerve, we find  it  distributed by the  vast majority of  its fibres to
muscles, and those  minute branches, respecting the  ultimate destina-
tion of which some doubt exists, may be, and  probably are, distri-
buted to muscular  fibres.  The  muscles which  are  supplied by the
facial nerve are chiefly those  upon which the aspect of the counte-
nance and the balance of the features depend.  The  power of closing
the eyelids depends on  this nerve, as it alone supplies the orbicularis
palpebrarum; and likewise that of  frowning, from its influence upon
the corrugator supercilii.   Anatomy indicates, therefore, that this
nerve is the  motor  nerve of the superficial  muscles of  the face and
ear, and of the deep-seated muscular fibres within the ear.
  This conclusion is abundantly confirmed by comparative anatomy.
For wherever the superficial  muscles of the face are well developed,
and the play of the features is active,  this nerve is  large.  In mon-
keys  it is especially so.   That extremely  mobile instrument,  the
elephant's trunk, is provided  with  a large branch  of the facial as its
motor nerve.  In birds, on  the  other hand,  it  is very  small, being
limited to the stylohyoid branch.
  Section of the nerve, at its emergence from the stylomastoid fora-
men, has  been followed by paralysis of the muscles of  the face, and
of the orbicularis palpebrarum, in   the hands of  all experimenters.
Formerly when  this nerve was supposed to  preside over the sensi-
bility of the  face, it was  thought to be  the seat of tic  douloureux,
and was upon several occasions  cut.  But this  operation yielded no
relief to the sufferings of the patient, and  only served to illustrate the
function of the nerve, since it was  always succeeded by paralysis of 
THE FACIAL NERVE.
479
the face  on that side, total  loss of control over  the  features, of the
power of frowning, and of closing the eyelids.
  The diseased states of the facial nerve illustrate its physiology in
the most interesting manner.  It may be paralyzed from the influence
of cold, benumbing its superficial fibres, or from the compression of
a tumour at the angle of the jaw, or from a carious state of the petrous
portion  of the  temporal bone.   From whatever  cause the paralytic
state arises, the effect is invariably the same;  the patient is unable to
close  his eyelids, and in some rare cases he has  not the power  even
of approximating them  to each other  in the least degree.   He cannot
move the ala nasi  or either lip on the affected  side, and if told to
purse up the mouth, as in whistling, he is unable to do it.  When
he  laughs, the  movement is all on  one side, and the angle of the
mouth on the  sound side  is drawn upwards  towards the  ear, whilst
that on the paralyzed side hangs below its ordinary level.  WTith so
much paralysis of the  superficial  muscles, the  deeper  seated  ones
which direct the masticatory movements of the  lower jaw, and are
supplied by the fifth nerve, remain unaffected, and the sensibility of
the face is unimpaired.
  When the paralytic affection  of this nerve has  been of  long stand-
ing, there is great  wasting of the muscles  on that side  of the  face,
and even  the buccinator,  which is supplied by the fifth nerve  also,
suffers to such  an  extent  that  it becomes  reduced to a mere  inert
membrane, and flaps to and  fro as the patient speaks, interfering to a
great  degree with the clearness of his articulation.
  That the facial  nerve in some degree influences the movements of
the soft palate, has been suggested by the  record of  cases in which
palsy  of the muscles on one side of  the  face has been accompanied
by  paralysis of the  corresponding half of the  velum.   That this
symptom sometimes accompanies  the other  signs of this form of
palsy, cannot be doubted;  but  the frequency of  its absence is  suffi-
cient to denote the trifling influence  of  the nerve upon the palatine
muscles.  Valentin irritated the greater superficial  petrosal  nerve,
which is the probable source of any nervous filaments from the facial
to the muscles  of the palate, but failed to excite  any movement of
those  muscles in fifteen experiments.
  Much  uncertainty exists likewise  as regards  the  function of the
chorda tympani.  Regarding it, as we do, as a branch of the portio
dura,  we think  it must exercise a motor influence  upon the parts to
which it is distributed,  of  which the  principal is  the duct of the sub-
maxillary gland.  But the curious relation which it bears to the mal-
leus and incus  denotes that it  may have something  to  do with the
mechanism of the  organ of hearing.
   It has been  made a question, how far  the facial nerve  possesses
any sensibility, and from whence it  derives  sensitive fibres.   That
irritation of it  causes  pain, has been sufficiently proved by various
experimenters,  and it  appears  that  the  sensibility is more marked
after the nerve  has  passed through the  parotid gland.  The sources
of the sensitive fibres  appear to be  clearly indicated by the various
anastomoses which the  facial nerve  forms in its several  stages—in 
480
INNERVATION.
the Fallopian  aqueduct with the vagus nerve, in  the face with  the
fifth nerve, and in the neck with spinal nerves ; the communications
with the fifth nerve being very numerous.  There  are, therefore, suf-
ficient means of communication with sensitive nerves to explain  the
sensibility of the facial without its being necessary to have  recourse
to the theory of Arnold, and to rank it with the double-rooted nerves.
   Of the Ninth or Hypoglossal Nerve.—The  origin of this  nerve is
from the side of the medulla oblongata  along  the  anterior margin of
the olivary body.  Ten or twelve fasciculi of fibres emerge here from
the central part of the medulla oblongata, and unite into two bundles,
which coalesce and emerge as one nerve  through the  anterior con-
dyloid foramen.
   The ninth nerve, on escaping from the anterior condyloid foramen,
passes outwards, and winds forwards around the pharynx, to the deep
surface  of  the tongue, being  closely related to  the  internal carotid
artery, and the jugular vein, and winding round  the external carotid,
in its  course to the upper and  anterior part of  the  neck.
   Immediately after its  emergence it  forms anastomoses with  the
vagus  nerve, the  superior cervical ganglion, and with the  cervical
plexus, and then it  gives  off,  1.  The descending  branch,  which
forms remarkable anastomotic arches with branches of the second
and third cervical nerves, either within or in  front of the sheath of
the common carotid artery and jugular vein.   From the convexity of
this arch or these arches, there pass branches to the sterno-hyoid, and
sterno-thyroid muscles, and to the anterior belly  of  the omo-hyoid.
2. It  gives nerves to the thyro-hyoid,  genio-hyoid, hyoglossus, and
styloglossus muscles.  3. On the inferior surface of the tongue it
breaks  up  into its terminal or glossal branches which pass  into  the
muscular structure of the tongue.
   As  the hypoglossal nerve crosses the hyoglossus  muscle  it forms
an anastomosis with the lingual branch  of the fifth pair.
   Function of the Ninth Nerve.—As this nerve  has no other con-
nection than with muscles we cannot regard it in any  other light than
as a motor nerve.  The muscles to which it is distributed are those
of the tongue, and as this is the principal nerve to these muscles,  we
may justly  regard  it as the motor  nerve of the  tongue.  The other
nerves of the tongue, the lingual branch of the fifth  and the glosso-
pharyngeal, are obviously traceable to the mucous membrane.
   In the lower mammalia the ninth nerve is distributed precisely as
in man, and it is proportional in size to the muscular activity of  the
tongue.
   Numerous experiments have been made on this nerve.   Section
of it on  one side  paralyzes  the  motor power of the  tongue  on  that
side.   And galvanic irritation of it throws the muscles on the same
side into convulsive action.
   Several instances have been observed of tumours compressing this
nerve, and causing paralysis  of the muscles  of the  tongue on  the
same  side.   The tongue participates  in  the hemiplegic  paralysis
which results from an apoplectic clot in  the brain,  or  other extensive
disease  of  that organ, along with  all those parts  whose nerves  are 
COMPOUND ENCEPHALIC NERVES.
481
implanted  in some part of the extended  centre of volition, and are
ordinarily  excited by a mental stimulus.   In such  cases the loss of
power in the tongue  is  usually  indicated by its deviation to the
paralyzed side in its protrusion, though occasionally the tip  is turned
towards the sound side.
   We may then conclude from human  and  comparative  anatomy,
from experiment and pathological states, that the ninth nerve is the
motor  nerve of the tongue.  Its  anastomoses with the vagus, and
with the fifth, make it  probable that it contains some sensitive fila-
ments, and this  is confirmed  by experiments  which show that some
sensibility  is possessed by the nerve,  and that  this is  greatest the
nearer we  approach the tongue.   But  that it has  no influence upon
taste or upon the common  sensibility of the organ, is proved by the
unimpaired state of  both those powers, after complete section of the
nerve.

  In addition to the principal systematic works on physiology, reference may be
made to Valentin, de Functionibus  Nerv. Cerebr.; the Papers of Sir C. Bell, col-
lected in an  octavo volume, 1844:; Mayo's papers in his Anat. and Physiol.  Com-
mentaries, and his Physiology; Longet sur le Systeme Nerveux.
                         CHAPTER XX.

 OF THE COMPOUND ENCEPHALIC NERVES.  THE FIFTH PAIR.  THE EIGHTH
                              PAIR.

  It is proposed  to  devote this chapter  to the examination of the
 physiological  history of those  encephalic  nerves which, from  their
 compound nature, combine the functions of sensitive  and motor
 nerves.  These are the fifth pair and the eighth pair.
  The fifth pair of nerves is one of the most interesting and exten-
 sively connected nerves in the body.  It presents a remarkable re-
 semblance to spinal  nerves  in its mode of origin, a fact which bears
 strongly on  the determination of its  functions.   The  first  point of
 resemblance  is  that  its origin is by two  roots, one large,  and the
 other small;  and secondly, its larger root  is involved in a ganglion,
 the  two roots being quite distinct until after the formation of the  gan-
 glion,  when the lesser  one  coalesces  with one of the nerves which
 springs from the ganglion, to form the inferior maxillary nerve.
  The two  roots are implanted in  the same column of  the  medulla
oblongata.   They remain, however, quite distinct in the substance of
the  medulla.   Penetrating the latter  at the crus cerebelli, between
the  transverse fibres of  the pons, each root may be traced through a
separate but nearly parallel course downwards to the olivary column,
where each forms its separate connection with the vesicular matter.
  The ganglion (ganglion  Gasserii) which is formed upon the larger 
482
INNERVATION.
root of the  fifth nerve is situate in the middle fossa of the  cranium
upon the upper surface of the petrous bone, and the middle lacerated
foramen, and behind the  great ala of the sphenoid.   It  is of a trian-
gular form,  its base curvilinear  and directed  forwards and outwards.
From  this base there proceed  three  nerves, the  ophthalmic  on the
inside, the superior maxillary in the middle,  and  the inferior  maxil-
lary on  the outside.   Of these  the first two consist exclusively of
fibres  derived  from the larger root and ganglion ;  the third,  the infe-
rior maxillary, is composed of fibres derived  from both roots.  This,
therefore, is the only portion  of the fifth  nerve which is strictly com-
pound, and it constitutes the  largest portion of the nerve.
   The distribution of the nerve may  be understood by reference to
the subjoined tabular  arrangement of  the  distribution of each of its
three divisions.

           TABULAR VIEW OF THE DISTRIBUTION OF THE FIFTH NERVE.

I. Ophthalmic—(anastomoses with sympathetic).
                 f 1. b. To lachrymal gland.
      T   h   alJ 2. &• To unite with temporo-malar branch of  supra-maxillary
           ^     ]       nerve.
                 ^3. b. To external canthus, eyelids, &c.
                CI. Supra-trochleator b, to  integuments of internal canthus, con-
    b. Frontal , <    junctiva, lids, &c.
                 ^2. Continued frontal nerve, or supra-orbital.
                 f 1. Lenticular b, to the ophthalmic ganglion.
                 I 2. Ciliary nerves,—two in number.
    c. Nasal   . ■{ 3. Nasal b, to the  mucous membrane and skin of  the  anterior
                     part of the nostril.
                 [4. Infra-trochleator, to the inner canthus and side of the nose.
II. Superior Maxillary—(three stages, cranial, spheno-maxillary, orbital).
    a. Temporo-malar b.—Anastomoses with the lachrymal, and is distributed to the
                        integument of the temporal  and malar region.
    b. Spheno-palatine b.—Two or three  in number,  which pass  to  the  spheno-
                        palatine ganglion.
    c. Post, superior dental b.—Two or three in number, going to the posterior teeth
                        of the upper jaw; one branch passing along the interior
                        of the antrum, and anastomosing with the anterior supe-
                        rior dental.
    d. Ant. superior dental b.—Supplies the anterior teeth of the upper jaw.
                      C"l  Palpebrals
    e. Facial     .   .  \ 2.  Labial   C^PPV^S the integuments  of those re-
                      h.  Nasal    5  S,ons'
III. Inferior Maxillary.
    a. Masseteric b.—To the masseter muscle.
    b. Deep temporal b.—Two in number, to the temporal  muscle.
    c. Buccal b.—Anastomoses with branches of the facial, and goes to the external
                  pterygoid and buccinator muscles, and to the mucous  membrane
                  of the mouth.
    d. Pterygoid b.—To the circumflexus palati and internal pterygoid muscle.
    e. Superficial temporal b.—Anastomoses with the facial, and is distributed to the
                  skin of the temporal region and external  ear.
                    ' By its mylohyoid branch  to  the  mylohyoid and digastric
                        muscles.
    /. Inferior dental b.-\ To the teeth, alveoli and gums of the lower jaw;
                     and by the mental branch to  the  integuments and mucous
                        membrane of the lower lip.
                     Is joined by the chorda tympani.
                     Connecting  filaments  to  the submaxillary  ganglion or
    g. Lingual b.   .  •{    plexus.
                     Anastomotic branches to the ninth nerve.
                    _ Branches to mucous membrane of the tongue. 
THE FIFTH NERVE.
483
  Function of the fifth nerve.—The determination of the  functions
of the roots of spinal nerves has afforded the clue to that of the func-
tions of the roots of the fifth nerve.  The analogy of the smaller root
of the fifth with the anterior spinal root, and of the larger one with
the posterior spinal root  has long been admitted by anatomists.—
Hence an analogy of function must be admitted, and the former must
be viewed as consisting of motor fibres, the latter of sensitive ones ;
and by tracing each  of the three great divisions of the nerve, we  may
determine  its function by its constitution, according as it derives its
fibres from either root or from  both.  The  ophthalmic and superior
maxillary are composed of fibres  derived exclusively from the larger
root; they are, therefore,  sensitive nerves.   The inferior  maxillary
consists of fibres derived from both roots, and consequently is both
motor and sensitive.  Sir C. Bell, in his original exposition of the
functions of this nerve, fell  into error from  having neglected to avail
himself of this method of analyzing the constitution of each of its
three divisions from which he would have  seen that it is the inferior
maxillary  alone  which derives its fibres from both roots, and which
perfectly resembles  a spinal  nerve in constitution.
  The distribution of the three divisions of the fifth nerve confirms
most amply the  view of its physiology suggested  by the anatomy of
its  origin.   The ophthalmic and  superior  maxillary are distributed
entirely to  sentient   surfaces, or anastomose with  motor  nerves (the
facial).   They supply the skin of the   forehead,  of the eyelids, the
conjunctiva, the eyeball, the mucous membrane  of the nostrils, the
integuments of the   face,  the upper lip, the nose, the  beard  on the
upper lip, the integument of the  ear, the temple, and the whiskers ;
they are the sensitive nerves to  these regions.   The inferior maxil-
lary has two distinct sets of  branches, the one by which the muscles
of mastication are supplied—the  other, which go to the integuments
of the lower lip  and chin, and the beard, and the mucous membrane
of the mouth and tongue.  This nerve is, therefore, the nerve of mas-
tication, and of sensation to  the surfaces above  named.
   Repeated experiments in the hands of various physiologists, none
of which, however,  were  more conclusive than those of Mayo, indi-
cate the same views of function.  Division of the ophthalmic or of
the superior  maxillary induced loss of sensibility without  muscular
paralysis, leaving only such  an impairment  of the  motor power as
destruction of the sensitive nerves invariably produces, by  impairing
the power of exact adjustment, for which a high degree of sensibility
is necessary.   But  when  the inferior maxillary nerve was cut,  then
both the power of mastication  was destroyed on the same side, and
the sensibility of  the lower part of the  face and tongue was lost.  If
the nerve  were  divided  in  the cranium, the whole side of the face
and forehead, with the eyeball  and nose, became insensible, and the
muscles of mastication were paralyzed.  Irritants  might then be ap-
plied to the eyeball, without exciting winking, or causing  pain, and
strong stimulants might be introduced into the nostrils without creating
the least irritation.   When the trunk of the nerve within the cranium
of an ass  was irritated, the jaws  closed with a snap from the excita- 
484
INNERVATION.
tion of the motor fibres, which are distributed to the muscles of mas-
tication.
  The conclusions which we draw from anatomy and from experi-
ment are confirmed by the histories of cases in which the fifth nerve
had  been  diseased.  In  such instances we  may observe the most
marked separation of the motor and sensitive power, when the larger
portion only or the two superior divisions of the nerve  are affected,
and we find  both motion  and sensation destroyed when the whole
trunk of the nerve is involved in the disease.  It  is not uncommon
in such  cases  to  find the eyeball totally insensible to every kind of
stimulus, the nose quite unexcitable  by the fumes of ammonia, or the
most  pungent  vapors, and  the  mucous  membrane of the mouth so
insensible to  the contact of foreign matters that a morsel  of food will
sometimes  remain between the gum and the  cheek until it has become
decomposed.   The insensibility of the eyeball exposes it to the per-
manent contact  of irritating particles of dust, &c, which excite  de-
structive inflammation of  its textures.   The whiskers may be pulled
forcibly  without sensation.   The muscles of mastication  become
wasted and inert, as shown by the distinct  depression in the regions
of the masseter and temporal muscles, but the superficial  muscles,
on  which  the  play of the features  depends,  preserve  their natural
condition.
  The fifth nerve may, therefore, be regarded as the motor nerve in
mastication, and the sensitive nerve  to that  great surface, both inter-
nal and external, which belongs to the face  and anterior part of  the
cranium.   From its great size, and the large  portion of  the  medulla
oblongata  with  which it  is  connected,  it  may excite  other  nerves
which are  implanted in that centre near to it.  Thus it may be an
excitor to the portio dura, as in winking—or to the respiratory nerves,
as in  dashing cold water in the face, or in sneezing.  Its lingual por-
tion distributed to the  mucous membrane of the  tongue is at once a
nerve of taste, touch, and common sensibility, and its connection with
the papillary structure of the red  parts of the lips constitutes it a pre-
eminently  sensitive nerve of touch in those regions.
  The study of the pathological  conditions of this nerve illustrates
its  physiology in a  highly interesting  manner.  In the  dentition of
children, whether primary or secondary, it  is always affected, more
or less:  and in excitable states of the nervous centres,  the irritation
of it consequent upon  the pressure  of the teeth often gives  rise to
convulsions, the brain and  spinal cord being irritated ; and we  can
often trace to  such irritation, whether  in infancy  or in childhood,
the foundation  of epileptic  seizures in  subsequent years.  Painful
affections  of the face (neuralgia) have their seat in this nerve ; tic-
douloureux, for example.   Many of  the instances of painful affection
of this nerve or of branches  of it, which come under our observation,
are well marked  examples of reflected  sensation, the primary irrita-
tion being conveyed to the  centre by the vagus or the  sympathetic
from the stomach or intestinal canal.  No one of these is so common
as the pain over the brow, which so  often follows derangement of
stomach digestion; and  which  may  frequently be  instantaneously 
         EIGHTH PAIR OF NERVES.—GLOSSOPHARYNGEAL.     485

removed by taking away the source of irritation, as by neutralizing .
free  acid in the  stomach.   Frequently also  the  branches of this
nerve, in greater or less number, on one or both sides, may, accord-
ing to the humoral view, form a focus of attraction for a morbific
matter generated in the blood, in persons exposed to the paludal
poison, or in  persons of rheumatic  or  gouty  constitution; in these
cases, as in most others of similar pathology, the neuralgia occurs in
paroxysms of  greater or less severity, each paroxysm being followed
by a period of convalescence, which lasts, it may be supposed, until
the morbid matter has been again accumulated in  quantity sufficient
to induce a high degree of  irritation of the nerves.
   Of the Eighth Pair of Nerves.—We must examine separately the
anatomy and  physiology of each  of the three nerves, which, taken
together, constitute the eighth pair;  and, first,
   Of the  Glossopharyngeal.—This  nerve  consists of several small
fascicles of fibres, which lie close together, and are implanted in the
upper part of the medulla oblongata behind the olivary body.  The
fibres penetrate  to the  centre  of  the medulla (the olivary columns),
where they connect themselves with a special  accumulation of vesi-
cular matter.
   The glossopharyngeal nerve escapes through a small foramen in the
dura  mater, at the anterior part  of the foramen  lacerum posterius.
Immediately after it has passed this foramen, a small ganglion, which
involves only  some of the fibres of the nerve, is formed upon it.   This
is the ganglion jugulare, discovered by Ehrenritter.  Beyond this,
 and lodged in a fossa in the  side  of the jugular foramen, is another
 ganglion which involves all the fibres of the nerve ; this is the gan-
glion petrosum, originally described  by Andersch.   After its escape
through the jugular foramen, the glossopharyngeal descends by the side
 of the pharynx, between the styloglossus and stylopharyngeus mus-
 cles, and in the region of the  tonsil  breaks up  into its  terminal
 branches.
   From the ganglion of Andersch, a nerve passes  off, and enters the
 cavity of the tympanum, occupying a groove upon the surface of the
 promontory beneath the lining membrane of the  tympanum.  This
 branch, lately called the branch of Jacobson,  although described  by
 Andersch  and Winslow, divides into  six  filaments, which  form the
 tympanic plexus  or anastomosis.   These filaments are as follows:—
 1.  To the membrane of the fenestra ovalis.  2. To that of the fenes-
tra rotunda.   3.  To the carotid plexus in the  carotid canal.   4.  To
 the mucous membrane  of the Eustachian tube.   5. An anastomotic
branch, which, passing through the upper wall of the tympanum, unites
 with the greater superficial petrosal nerve.   6.  An anastomotic branch
 to the otic ganglion called by Arnold the  lesser  superficial petrosal
 nerve.
   Near the petrosal ganglion the glossopharyngeal  nerve forms anas-
 tomoses with the facial and the par vagum.
   The following  are the terminal branches of the glossopharyngeal
 nerve.  1. A branch to the digastric and  stylopharyngeal  muscles.
 2.  Three  or four carotid filaments which descend  along the  internal 
486
INNERVATION.
carotid artery, and maybe traced as far as the bifurcation of the com-
mon carotid.  These nerves anastomose with others from the superior
cervical  ganglion, and form a  plexus round the carotid artery.  3.
Tonsillitic branches, which are numerous, and along with nerves from
the vagus and from the superior cervical ganglion of the sympathetic,
form  a plexus  beneath the mucous  membrane in the vicinity of the
tonsil, which is called the pharyngeal or  tonsillitic plexus.   Some of
the branches of this plexus are distinctly connected with the raucous
membrane, others with the muscular fibres of the pharynx.   4. Pha-
ryngeal branches, which are distributed to the mucous membrane of the
wall of the  pharynx.  5.  Lingual branches; these are given  to the
mucous membrane  at the base  and side of the tongue, and one may
usually be traced into the soft palate.
   From the  preceding  statement it appears that the  distribution of
the glossopharyngeal nerve is chiefly, if not exclusively, to sentient
surfaces.  Even  its tympanic  branch is connected with the  lining
membrane of that cavity and of the Eustachian tube.  But its princi-
pal branches are those on the pharynx and tongue, which latter region,
however, it  must not be forgotten, has another nerve distributed to its
mucous membrane.   Its digastric branch seems to be anastomotic with
a similar one from the facial.
   The mode of origin of this nerve affords but a feeble clue to the dis-
covery of its physiological import.  Muller and  others attach  some
value to the existence of the ganglion, involving only some of its fibres
shortly after their origin, and from the analogy with spinal nerves and
with the fifth, they infer that the glossopharyngeal must be a compound
nerve of double origin, containing both  motor and sensitive  fibres.
There is not, however, sufficiently certain evidence of the  existence
of two roots to this nerve to justify  us in founding upon it an  argu-
ment  respecting its  function.
   The most extensive series of experiments on this subject  are  those
of Dr. John  Reid,  and  they have very satisfactorily  developed the
proper functions of  the nerve.
   Section of the nerve, or irritation of it, always caused pain, and
hence it may be said to contain fibres of  common sensation.
   When the trunk  of the nerve was irritated  before giving  off its
pharyngeal  branches, extensive  muscular  movements of the  throat
and lower part of the face were produced.   It was found that these
movements were  equally produced, and to as  great an extent, if the
nerve had been cut a short way below its exit from  the cranium, and
the cranial end of it irritated.   Hence it was evident that the  move-
ments were  caused, not by the direct influence of the branches of the
glossopharyngeal upon the muscles, but by that of the cranial end of
the nerve upon the  medulla oblongata, whence the change was pro-
pagated to the muscles through the fibres of the vagus nerve and
through those of the facial, which emanate from the same part  of the
nervous centre.
   This view of the  mode in which the glossopharyngeal causes mus-
cular action  is confirmed by the result of experiments on it in animals
just dead.  When the nerve was irritated under those circumstances, 
THE GLOSSOPHARYNGEAL NERVE.
487
no movements could be excited, provided it was sufficiently insulated
from the pharyngeal branches  of the vagus.  Now, were  the fibres
of the glossopharyngeal motor, there  is no  doubt that  mechanical
irritation of them would have caused muscular contraction.
  Hence, the glossopharyngeal  is one of those sensitive nerves which
is capable of exciting  motion through its influence upon motor fibres
implanted immediately contiguous to it in the nervous centre.
  It appeared, however, that other fibres were capable of exciting the
movements of the pharynx, for when the trunk of  the nerve was cut
on both sides, the movements of deglutition continued.
  Dr. Reid's experiments showed that section of the lingual branches
of this nerve did  not destroy the power  of taste, and therefore that the
glossopharyngeal  cannot be regarded, according to the views  of Pa-
nizza, as the sole  nerve of that sense.   And this accords so complete-
ly with anatomy,  which shows that a part of the tongue, enjoying the
gustatory power,  is supplied by the fifth nerve and that only, and that
another part, also enjoying  the same power, is supplied  only by the
glossopharyngeal, that  no doubt can be entertained of the correctness
of the view which assigns gustatory power to this nerve as well as to
certain filaments of the fifth pair.  At a former page we have referred
to a case of paralysis of the  fifth nerve in  which,  while  taste was
altogether lost in the anterior  part of the tongue, it  continued at  its
posterior part; the fifth nerve which supplies the tongue in the former
situation being paralyzed,  whilst the glossopharyngeal, distributed  in
the latter region,  was free from  disease.  Two very interesting cases
confirmatory of the  same view have  since been  published  by Mr.
Dixon, in the Med. Chir. Trans., vol. xxviii.
  Disease,  limited to this nerve, is of extremely rare  occurrence.  In
one instance  that we have met with, in which its  neurilemma was
considerably thickened, there was not only total inability  to swallow,
but likewise the mucous membrane  of  the pharynx was quite  insen-
sible to stimuli, and that surface of  the fauces which, in  health, may
be excited  by the slightest touch of  a feather, admitted even of fric-
tion without  any uneasiness to the patient, or the least muscular
contraction.
  The functions of the glossopharyngeal  nerve are highly  worthy of
an  attentive study, in  reference to  the very  important question dis-
cussed at a former  page, as to the  existence of distinct spinal and
cerebral fibres.   We have in it an example of a nerve at once excitor
and sensitive; it  is a most marked instance of a nerve, not motor in
itself, but capable of exciting motion by its influence  on others.  Yet
no part of the surface to which it is distributed can be touched without
sensation being excited, and with it motion.   The stimulation even of
that portion of the tongue which receives filaments from it, is capable
of exciting the pharyngeal muscles to  contract, although the  action
is not so energetic as when the stimulus is applied to the isthmus
faucium.   In examining the fauces of patients,  the  practitioner has
frequent opportunity of observing the extraordinary sensibility of the
mucous  membrane, where the  glossopharyngeal nerve ramifies, and 
488
INNERVATION.
the remarkable rapidity with which the pharyngeal  muscles respond
to. the slightest stimulus applied to it.
   The following conclusions may be adopted  respecting the glosso-
pharyngeal nerve.
   1. It is the sensitive nerve of the mucous membrane of the fauces
and of the root of the tongue,  and in the latter situation it  ministers
to taste and touch as well  as to common sensibility ; and  being the
sensitive nerve of the fauces, it is probably concerned in the feeling
of nausea which maybe so readily excited by stimulating the mucous
membrane of this region.
   2. Such are its peripheral organization and  central connections,
that stimulation of any part of the  mucous membrane in  which it
ramifies, excites instantly to contraction  all the  faucial  muscles sup-
plied by the  vagus  and  the facial nerves, and the permanent irrita-
tion of its peripheral  ramifications,  as in cases of sore throat, will
affect other muscles  supplied  by  the  facial nerve likewise.   It is,
therefore, an  excitor  of the movements necessary  to pharyngeal  de-
glutition.
   Of the Vagus Nerve.—The par vagum or pneumogastric nerve is of
all the encephalic nerves the most extensively connected.
   This nerve emerges from the medulla oblongata  immediately be-
low the glossopharyngeal,  by  from  eight  to  ten  fasciculi  of  fibres
which  pass outwards to an opening in the dura mater, through which
it  escapes in  company with the spinal accessory.  The  line along
which  its fascicles emerge from the medulla is placed a little behind
the posterior  edge of the olivary body.   These fascicles penetrate the
olivary  columns, and are there  implanted in especial accumulation of
vesicular matter.
  A ganglion is formed  upon the vagus nerve immediately it enters
the canal of the dura mater. From  this gatiglion  some small nerves
come off".  Shortly after the  emergence of the vagus nerve from the
base of the skull, another gangliform enlargement is formed upon it,
which Arnold calls plexus gangliformis.  It is at the situation of this
enlargement that the  union between this nerve and  the internal branch
of the  spinal accessory takes place.
  At its upper part the vagus  forms numerous  anastomoses, at first
by nerves given off  from the ganglion.   These are,  a, with the gan-
glion petrosum of the glossopharyngeal, b, with the carotid branch of
the superior cervical  ganglion, c, with the facial nerve, through  the
branch called by Arnold  the auricular,  which is situate in the jugular
fossa outside  the vein, and is seen through its coats when that vessel
is laid  open.   It anastomoses likewise with the ninth nerve, with the
cervical plexus, and with the superior cervical ganglion, in a manner
sometimes very intimate.
  The following branches are given  off' by the vagus nerve.
  1. The Pharyngeal Branch.—This is believed by  some anatomists
to be derived  altogether from the spinal accessory  nerve, through its
anastomosis with the vagus.  It forms, along with the  glossopharyn-
geal, some cervical nerves and  sympathetic filaments, the pharyngeal
plexus,  and its branches seem to be distributed to  the muscles of the 
THE VAGUS NERVE.
489
pharynx.   Sometimes there are  two pharyngeal branches, a superior
and  inferior.
   2.  The Superior Laryngeal  Nerve, which  gives off' the  external
laryngeal nerve to the crico-thyroid muscle, and is itself distributed to
the mucous membrane of the larynx, and sends an anastomotic branch
to the inferior laryngeal  nerve.
   3.  Cervical Cardiac Branches.—These are at least two in number
on each side, and they pass down in front of the innominata on the right
and  of  the aortic arch on  the left, and contribute to form the small
plexus between the aorta  and pulmonary artery.
   4.  The Inferior Laryngeal Nerve.—This important nerve is distri-
buted to all the intrinsic muscles of the larynx, except the crico-thyroid.
The peculiarity  of its course has given it the name recurrent.  It has
interesting relations differing on the right and left side.  Arising on
the left side just in front of the  arch of the aorta, it winds round the
concavity of that vessel, and ascends between  the oesophagus and the
trachea to the lower edge of the inferior constrictor of the pharynx.
The  nerve  of the right side separates from the trunk just above the
subclavian artery, and  winds round it, ascending in  the neck  to a
similar destination.
   Both recurrent nerves  before their ultimate distribution  give off
filaments to  the  heart,  to the trachea, to the oesophagus, and  to the
inferior constrictor of the  pharynx.
   5.  Inferior or  Thoracic  Cardiac Branches, distributed  to  the peri-
cardium, and the cardiac plexus.
   6.  Anterior Pulmonary Branches, passing in  front of the bronchial
tube at the root of the lung, and penetrating the pulmonary substance,
along with the ramifications of the  bronchus, and of the pulmonary
artery.
   7.  Oesophageal Branches, which are very  numerous, and distributed
to the oesophagus, throughout its entire length.
   8.  Tracheal Branches, to the mucous membrane and muscular fibres
of the trachea.
   9.  Posterior Pulmonary Branches; these go  to form the posterior
pulmonary plexus, of  which there are a right  and a  left plexus,
which anastomose freely with each other, situate  behind the bifurca-
tion of the trachea.  The  ramifications of this' plexus follow chiefly
the course of the bronchial tubes,  being distributed  to their mucous
membrane and muscular fibres.
   After giving  off the  pulmonary branches,  the vagi nerves  pass
down along the  oesophagus, giving off branches to it, and passing
through the oesophageal opening of the diaphragm, are distributed  to
the stomach.  The left nerve passes in front  of the cardiac orifice,
sends some  filaments over the   splenic  cul-de-sac, and  follows the
course of the lesser  curvature;  some of its branches passing in the
lesser omentum to the  liver, whilst  the rest  are distributed  to the
coats of the stomach.   The right nerve passes  behind  the cardiac
orifice, and  after giving several branches to the  stomach, sinks into
the solar pjexus.
  This outline of the anatomical distribution of this extensively con-
     32 
490
INNERVATION.
nected nerve  is sufficient  to  show that it  is devoted  to  muscular
fibres as well  as to sentient surfaces, and that it must be regarded as
a compound nerve, sensitive as well as motor.   The existence of the
ganglion,  which  involves  all the fibres of the vagus  nerve, in the
canal of the dura  mater, has led to the opinion that  all its proper
fibres are sensitive, while those branches which go  to muscles are
derived from its large anastomosis with the spinal accessory.  Whe-
ther this view be correct or not, it is certain that a free communication
exists just below the basis cranii between  the vagus and the spinal
accessory nerves.
   The  branches  of this nerve, which anatomy shows  to be purely
motor,  are the  pharyngeal  and  the inferior laryngeal, whilst the
cardiac, oesophageal, pulmonary, and  gastric  branches  are  doubtless
of a mixed character, and the superior laryngeal is purely  sensitive,
with  the  exception of  those  of  its fibres which form the  external
laryngeal  nerve.
   The distribution of the vagus nerve in the  inferior mammalia cor-
responds very closely with that in man, and so far confirms the views
of function suggested by human  anatomy.  Its connection with the
sympathetic in some of the mammalia (the dog and cat, for instance),
is more intimate than in man, for the upper part of the cervical portion
of the sympathetic  is closely connected with it, so that they appear to
form but one nervous  trunk.   The general disposition of the nerve
in birds and reptiles does not materially differ from that in  man, and
it has an analogous arrangement  in fishes.
   The results of the numerous experiments of which this nerve has
been made the subject, accord in a striking  manner with  the con-
clusions deducible from anatomy.  Thus,  mechanical  and  galvanic
irritation of the pharyngeal branches has always produced contrac-
tions of  the pharynx: irritation  of the  superior laryngeal nerve
causes  contraction of the crico-thyroid muscle only,  whilst that of
the  inferior  laryngeal causes forcible contraction  of the laryngeal
muscles as well as of  the inferior constrictor of the pharynx.  In a
living  animal the slightest touch to the  mucous membrane of the
 glottis will cause  the instant closure of that  fissure, if the superior
laryngeal nerve  be uninjured, but if  that nerve be divided on both
 sides, the glottis may be irritated  with impunity.   It  is plain, then,
 that the inferior laryngeal is the  principal motor nerve  of the larynx,
 and that  the  superior laryngeal  is at once the  sensitive nerve, and
 the excitor of the motor action of the inferior laryngeal through the
 medulla oblongata.
   It is scarcely necessary to remark how untenable is the opinion ad-
 vocated by Majendie, that  an antagonism exsits between the superior
 and inferior laryngeal  nerves, the one acting upon  the  constrictors,
 the other upon the dilators  of the larynx.   The  superior  laryngeal
 nerve supplies, as we  have  seen, only one muscle, and the inferior,
 to which  he assigns the office of opening the glottis, supplies those
 muscles which are the principal agents in closing it.
    Impairment or  destruction of vocal power is  a  constant accom-
 paniment to injury or complete section of the  recurrent nerve. 
THE VAGUS NERVE.
491
   An interesting experiment of Dr. J. Reid illustrates the power of
 each laryngeal nerve respectively.   When the inferior laryngeals were
 cut, the superior remaining intact, a probe introduced into the glottis
 occasioned signs of pain and efforts to  cough, without any contraction
 of the glottis.  But when the superior  laryngeal nerves were cut, the
 recurrents being unimpaired, the probe could be introduced without
 exciting any irritation or effort whatever.
   This experiment demonstrates unequivocally, that the  spasmodic
 action induced  in  the larynx by the application of a stimulus to its
 mucous membrane, must be referred to the  class of physical nervous
 actions, and results from the influence  of the superior laryngeal upon
 the  inferior, through  the connection of their respective points of im-
 plantation in  the nervous centre.
   There can  be no doubt that the motions  of the oesophagus are re-
 gulated by the various oesophageal fibres given off from this nerve, in
 its course  through the thorax.  Irritation of its trunk has always pro-
 duced  contractions of the  oesophagus, as  testified by many experi-
 menters.   These contractions, Dr.  Reid states,  extended throughout
 the whole  tube  to  the cardia, where  they  became slow  and vermi-
 cular ; the oesophagus being shortened and diminished  in calibre at
 each application of the irritant.
   Distinct palsy of the oesophagus may be produced by section  of the
 vagus in the neck.   The following effects followed this  experiment
 by Dr. Reid on a rabbit, which had been kept fasting for sixteen hours
 previous to the experiment.   The  animal ate a quantity of parsley,
 amid considerable  dyspnoea  and  cough, with many efforts to vomit.
 It died in  five  hours.   The oesophagus was found  full of parsley
 throughout its entire extent down to the stomach, which was also filled,
 although not distended ;  and a good deal of the parsley had passed
 into  the trachea and bronchial tubes, and even into the minute air-cells
 of the lungs.
   The  appearances in this  experiment indicated complete paralysis
 of the oesophagus.  This tube was  filled by the  propulsive  power of
 the  pharynx,  which sent on  morsel after  morsel, until  the  whole
 stomach and  gullet were filled, the latter  being perfectly passive ;
 and  after  these  parts were  occupied, and  thus resisted  the further
 passage of the parsley, it found its  way more readily into the  larynx
 and trachea.
   It  m%y be inferred from  this and similar experiments that some-
 thing more than  an irritable  condition  of  the  muscular coat of the
 oesophagus is requisite in order to  insure its contraction when dis-
 tended by  food.
   The muscular fibres were  quite  uninjured,  and, therefore, ought
 to have acted, if the  stimulus  of distension were alone sufficient to
 excite their contraction.  The true cause of their  inaction was  the
 destruction of the nervous circle through which the sensitive nerves
 of the oesophngus  could excite its  motor  nerves.   This  portion of
the act of deglutition, therefore, is like that in the pharynx, a physical
 action, brought about by the impression of the food upon  the sentient
nerves of the oesophagus, which propagate their  change to the centre 
492
INNERVATION.
where the  motor fibres become excited.   It  cannot be said,  how-
ever, that the mind is unconscious of this part of the act of degluti-
tion, although it may be reasonably admitted that it has no  necessary
share in it.
  The results  of section  of  the  cardiac nerves  show that  these
nerves exert only a partial influence upon the heart:  the destruction
of them  affects  the actions of that organ only to a limited degree,
inasmuch as the heart receives nerves from the sympathetic as well
as from the vagus.
  Numerous  experiments  demonstrate  most unequivocally that this
nerve is  of vast importance to  the function of respiration.  Section
of one nerve produces no effect upon the respiratory organs, either
structural or  functional.    Dr.  Reid  made  careful  examinations to
ascertain if, after cutting out a large portion  of one nerve, the lung of
that side suffered any alteration in  its texture, but he could not detect
any.   But when both nerves have been divided above the giving off
of the pulmonary branches, the most severe dyspnoea  comes on, the
respirations are  generally much diminished in number, the animal
breathes just like an asthmatic ; after a short time the  lungs become
congested and cedematous, and  the  bronchial  tubes filled  with  a
frothy serous fluid.  When a piece has  been cut out of each nerve,
or  the cut ends of the  nerves are kept apart, the animals never
survive beyond three days, and during the whole of that period they
suffer severe dyspnoea.  If the cut ends of the nerves be kept in con-
tact, the  animals will live ten or twelve days.
  It may be inferred from Dr. Reid's  experiments, that section of
the vagi  nerves  does not destroy that peculiar feeling of distress
(besom de respirer), which is occasioned by the want of fresh air in
the lungs. He  proved that animals, in which the vagi nerves had
been cut, struggled violently, and  seemed to suffer greatly, when the
access of air to the lungs was cut off  by compressing the trachea.
  In such cases as that just described, the only channel through which
sensitive impressions could be conveyed from the lungs to the brain,
is the sympathetic system, and it is to the afferent power of the sym-
pathetic  nerves, and possibly  to  the  same power in  the cutaneous
ramifications of the fifth and of the spinal  nerves, that we must  attri-
bute the imperfect excitation  of the  respiratory act,  which,  under
these circumstances, takes place.
  The phenomena which  follow section of both vagi are  doubtless
to be  explained by the  imperfect manner  in which the  centre of
respiration is excited, after the  destruction of the influence of  these
nerves consequent on their section.  The movements, after the sec-
tion, are  partly of the voluntary kind, produced  by the sense of dis-
tress occasioned by the imperfect supply.  The asthmatic state which
also follows the section, may perhaps be in part caused by  the irrita-
tion of the central portion of the nerve, exciting the medfilla oblongata
and the extremities of the motor nerves  of respiration.
  Lastly, the office of the gastric branches of the vagi nerves, ap-
pears from Reid's  experiments to be  chiefly to control the move-
nt 
THE VAGUS NERVE.
493
ments of the muscular coat of the  stomach.  Mechanical  irritation
of these  nerves causes slow and vermicular contractions of this tunic.
Section of them may cause, in the first instance, vomiting and loath-
ing of food, and it may retard the digestive  process, but it does not
put an end to it.  For not only do animals, with  the vagi  cut, eat
food from day to day, but, if killed at  a sufficient period after diges-
tion, their lacteals are found filled with chyle ;  affording unequivocal
evidence of the persistence of  the digestive process.
   Nor does the section of these nerves destroy the secretion of the
gastric  fluid, for the matter vomited affords  evidence of its having
been  mingled with acid, and the fact of the formation of chyle proves
that stomach digestion must have taken place.  Muller and Dickhoff,
in their experiments upon section of the vagi in geese, found the fluid
secreted by the stomach distinctly acid.   In  Dr. Reid's experiments,
the ordinary mucous secretion of the stomach was found in  its  usual
quantity, and when  arsenic was  administered to  the animals, the
mucous secretion was quite as abundant as in others in which the vagi
nerves were not cut.
   The few  pathological facts  which  can be  collected  of diseased
states of the vagi nerves are confirmatory of  the conclusions  deduci-
ble from anatomy and experiment.  Several instances are  recorded
of loss of voice and dyspnoea, symptoms resembling those of chronic
laryngitis, caused  by the  compression  of the recurrent by an aneu-
rismal or other tumour.  The violent convulsive cough, which accom-
panies enlarged bronchial glands, is  probably due to the  irritation of
the pulmonary branches  of the vagi  nerves.    Hooping-cough  is
probably an affection of the vagi nerves  by a peculiar poison.  Dr.
Lay attributed the  phenomena  of laryngismus  stridulus  to  the  irri-
tation of enlarged  cervical glands,  affecting  the  recurrent nerves,
and there seems no doubt that, although the symptoms of this disease
occur more frequently as part of a peculiar exhausted state of system,
they may be, and are, produced sometimes by the  local  irritation  of
such gland.
   The diseases in which  this  nerve  is  involved  are chiefly those
which affect  its gastric and pulmonary  branches.    The sympathy
which all practitioners admit to  exist  between the digestive and respi-
ratory organs is explained by the anatomical  relations of this nerve.
Asthma is essentially an irritation of the centre  of respiration and of
this nerve; this disease almost  invariably begins by some deranged
state of digestion,  or by the introduction of some poisonous  material
from without; some  very subtle material  suspended in  the  air,  and
brought by inhalation into  contact with  the respiratory surface, for ex-
ample, the minute particles which pass off from powdered ipecacuanha,
or from hay.   Asthma and intermittent fever often  go together, be-
cause the marsh poison which  gives rise  to the one, may  likewise
excite the other.   Asthma, which has occurred  once, is easily repro-
duced by irregularities of  diet,  and consequent  disturbance of diges-
tion ;  and the frequent recurrence of the  asthmatic  paroxysm causes
the dilated state of  the air-passages and  air-cells  of the lungs, the
dilation of  the right cavities of the  heart, and  the  general displace- 
494
INNERVATION.
ment of that organ, which are invariably present in persons who have
long  been subject to this disease.  Vomiting may be excited by irri-
tation of the central or  the  peripheral extremity of this nerve.  In
disease at the base of the brain, vomiting is frequently an early symp-
tom,  being caused by irritation of the  central extremity of the vagus.
In sea-sickness the cerebral extremity  of the nerve is irritated by the
disturbance of the circulation in the cranium.  By introducing emetic
substances into the stomach, the  vomiting is produced  by the irrita-
tion of the peripheral extremity.
  Many of the actions in which the vagus nerve is concerned are of
the  physical kind.  Of these, oesophageal  deglutition is  the most
marked.   The closure of the glottis  upon the application  of any
stimulus to its mucous membrane, is  another example of  the  same
nature.   But in both these instances, and in all the movements with
which this nerve has to do, sensation  accompanies the  act.   In oeso-
phageal deglutition,  there is less  sensation than in the other move-
ments, but  it is, nevertheless, present, particularly in case of any
impediment being offered to the passage of the food.  With reference
to the movements of the glottis, it is interesting to remark, that whilst
the  will exercises a  minuteness of control over  them which is only
surpassed by the power which it has over those  of the  fingers, it is
only closure of the glottis which is caused by a physical stimulus.  The
obvious explanation  of this  is derived  from  the great preponderance
of the constrictor over the dilator muscles  of the glottis.
  On what  grounds Dr. M. Hall asserts that " the vagus  nerve is
certainly the least sentient of any in the class vertebrata,"* we are at
a loss to discover.   We do  not hesitate to affirm that every  act of an
excitor kind, in which it is concerned, is accompanied  by sensation,
which in some is exquisite, in others feeble.  Nor can we derive, either
from the anatomy or  physiology of this nerve, any confirmation to his
hypothesis of a special  series of excitor and motor nerves.   It is well
known that continued  stimulation  of  the  pharyngeal portion of the
glosso-pharyngeal nerve  upon  the fauces will produce  the feeling of
nausea, and even vomiting.   Nausea is a feeling, accompanied  by a
particular condition  of the muscular coat of the  oesophagus  and sto-
mach, preparatory to vomiting, and may be produced  by  a certain
degree or kind of stimulation of  any part  of the mucous membrane
from  the fauces to the stomach.   The vagus  as well   as the glosso-
pharyngeal, is the instrument of this sensation;  for the latter  nerve
has not sufficiently extensive connections to justify the supposition that
it is the sole agent.   And this may be cited as a most striking instance
of the sensitive endowment of the  vagus.
  The following conclusions may be  adopted  respecting this  nerve
and its branches.
  1.  That the vagus nerve  contains filaments both of  sensation  and
motion.
  2.  That its pharyngeal branches  are motor.

  * The whole passage is, " This nerve (the vagus) is certainly the least sentient, and
the most purely excitor, of any in the class vertebrata."— New Memoir on the Nervous
System, Adv. p. 9. 
THE SPINAL ACCESSORY NERVE.
495
  3. That its superior laryngeal branch is the sensitive nerve of the
larynx, containing a few motor filaments to the crico-thyroid.
  4. That the inferior laryngeal  is the principal motor nerve of the
larynx.
  5. That the cardiac branches exert  a slight influence on the move-
ments of the heart.
  6. That its pulmonary branches contain both motor and  sensitive
filaments, and exercise an  important  influence upon the respiratory
acts, for they cannot be  destroyed  without  retarding materially the
respirations, impeding the  passage  of the blood through the lungs,
and causing oedema of these organs.
  7. That its oesophageal branches are the  channel through which
the muscles of that tube  are excited, through the medulla oblongata,
to contract.
  8. That  the gastric branches influence  the  movements  of the
stomach, and probably in some degree the  secretions and the sensi-
bility of its  mucous  membrane ; but that  their integrity  is  by no
means essential to the  continuance  of the secretion, or to  complete
chyraification.
   Of the Spinal Accessory Nerve.—The term spinal is applied to this
nerve because of its extensive connection with the upper part of the
spinal  cord.  It  escapes  from  the cranium along with the  vagus
through a common opening in the  dura mater; but its roots  are im-
planted in  the  side  of the medulla  oblongata,  and of the cervical
region of the cord as low as to the  level of  the fifth or sixth cervical
nerve.   On examining the side of  the upper part of the spinal cord,
the fascicles of origin of this  nerve  are seen  emerging from it, in the
interval between  the ligamentum denticulatum and  posterior roots of
the spinal nerves.  The lowest fascicles are  those nearest to the pos-
terior roots  of  the lower cervical nerves.   By the  union of all the
fascicles the nerve is formed,  and it  enters the cranial cavity from that
of the spine through the foramen magnum.
   Sometimes some  of  the  upper roots of the spinal accessory nerve
coalesce with the posterior roots of the suboccipital  and the  second
and third cervical nerves.  This appears to be nothing more than a
junction of the fibres of  two  nerves which  emerge  from the nervous
centre in close proximity to each other.
   Very shortly after the escape of the  spinal  accessory nerve from the
foramen lacerum, it divides into an  internal  and an external  branch.
The former  coalesces with  the  vagus, where its second ganglion is
formed,  and, according  to some  physiologists, supplies  the motor
branches of that nerve;  the  latter passes outwards  and downwards,
through  the deeper fibres  of the sterno-mastoid muscle, to which it
gives some branches, and anastomoses with  branches  of the second
and third cervical nerves ;  and having crossed the triangular space in
the neck between the sterno-mastoid  and trapezius, it penetrates the
latter muscle at its deep surface, and is distributed in it, anastomosing
with other branches of the cervical plexus.
   We learn from the anatomy of this  nerve  that it supplies two great
muscles, which play an important part in effecting certain movements 
496
INNERVATION.
 of the head and shoulder, and, in a secondary manner, contribute to
 the actions of respiration, especially to those of a forced or extraordi-
 nary kind ; and likewise  that it forms  a junction with the vagus nerve
 by a branch which consists of a considerable number of fibres.
   There can be no doubt, from anatomy, that those fibres of the nerve
 which pass  to  the trapezius and sterno-mastoid  muscles, are princi-
 pally motor, for their main  distribution is to  these muscles;  and all
 experimenters agree in stating that, whenever stimulated, they excite
 these muscles  to contract.   Anatomy,  however, equally indicates
 that these muscles derive motor  power from branches of the  cervical
 plexus likewise.
   The office of the internal branch, which incorporates itself with the
 vagus nerve, is not so easily determined.   Scarpa, Arnold, Bischoff,
 Bendz, and  others, viewed it as contributing the  motor fibres to that
 nerve, bearing to it the same relation as the  anterior to the posterior
 root of a spinal nerve.
   An objection  to this view, although not an insuperable one,  is sug-
 gested by the origin of the nerve, which  seems more  in accordance
 with  that of the posterior roots of the spinal nerves than with their
 anterior  roots, and this is especially the case with the lower fascicles
 of origin which  emerge from the cord quite close to the posterior roots
 of the cervical  nerves.   The reply to this objection  is, that the ex-
 ternal branch of the  nerve is nevertheless distinctly  motor, and that
 therefore the internal may be so likewise.   Morganti  and Bernard
 affirm that the lower roots form the  external branch; if so, then the
 superior fascicles may be  those which contribute to form the  internal
 branch,  and, therefore, its function probably differs from that of the
 external branch.  We have  already alluded to the fact  that  a coali-
 tion is sometimes observed between the posterior roots of the first or
 second cervical  nerves, and the upper roots of the spinal accessory.
 The function of the  former  being  confessedly sensitive, it is highly
 probable that the  latter nerves, which are apt to coalesce with them,
 should perform  a similar office.
   To  determine this  question  by experiment  is extremely  difficult
 by reason of the small size of the internal branch and the great depth
 at which it is situate, which  render it almost impossible to expose
 the nerve without injuring the vagus itself.  Accordingly, we  find the
 recorded statements of physiologists regarding the results of such ex-
 periments, quite contradictory.   The  greatest  number of observers,
 and the most recent ones, give their evidence against the motor func-
 tion of the internal branch, at least against the doctrine of its yielding
 the motor fibres  of the vagus  nerve.   Most of them, however, agree
 in stating that a degree of hoarseness and feebleness of voice always
 followed the section of  the internal branch,  as  if some of the motor
 fibres of  the  laryngeal nerves were derived from it.  From  Midler's
 and Dr.  John Reid's experiments,  by irritation of the spinal  acces-
 sory nerve within  the  cranium, no  conclusive results were obtained
 favourable to the view which assigns motor power to the internal
 branch ;  on the  contrary,  these experiments rather tend to prove that
the vagus contains within  itself the motor fibres sufficient for the parts
it supplies.   These experimenters found that irritation of the trunk of 
THE SPINAL ACCESSORY NERVE.
497
 the vagus, before its junction with the spinal  accessory, caused con-
 tractions of the pharyngeal and laryngeal muscles, as  well  as of the
 fibres of the oesophagus.
   Respecting the external branch of the spinal  accessory nerve, it
 has been already stated that experiment confirms the results deducible
 from anatomy.   We know that the trapezius and sterno-mastoid mus-
 cles receive nerves from the cervical plexus as well as from the spinal
 accessory.   If the latter be  cut, these muscles  are  not paralyzed,
 although weakened, and continue to act in respiratory as well  as in
 voluntary movements,  contrary  to the views of  Sir  C. Bell, who
 regarded the spinal accessory nerves  as  special  nerves of respira-
 tion, whilst those  of  the cervical plexus were nerves of volition.
 There are, indeed, no  good grounds for coming to any other conclu-
 sion than that which  Dr. John Reid arrives at; namely, that the
 external branch of the  spinal accessory exactly resembles, in its func-
 tions, the branches of the cervical plexus with  which it  so  freely
 anastomoses.
   It may be fairly asked, however, why do the trapezii and sterno-
 mastoid muscles receive their  nerves from a driuble  source?   The
 most reasonable reply to  this is, that while  the branches of the cer-
 vical plexus serve to connect these muscles with the centres of voli-
 tion and sensation in the ordinary way, the  external  branch of the
 spinal accessory connects it in a more direct  manner with the centre
 of respiration.  Nevertheless,  this branch, although especially  im-
 planted in that centre, is capable  of obeying voluntary impulses, so
 long as the  medulla oblongata maintains its  normal relation to the
 centre of volition.
   Thus, on the whole,  we assign motor power to the external branch
 of the spinal accessory, but we see no good  reason to subscribe to
 the  opinion that its internal branch must be regarded  as the motor
 root of the vagus.  Indeed, we are  much more disposed,  for ana-
 tomical reasons, to regard the office of this branch as totally different.
 None of the views hitherto put forward respecting this nerve explain
 the object of its peculiar and most extensive connection with the  nerv-
 ous centre; a connection which, in  the  larger quadrupeds, is still
 more extensive than  in man.   Our view is as follows: the internal
 branch of  the spinal  accessory  consists  of  afferent  fibres, which,
 connected  with the sensitive surface  of the respiratory organs, pass
 towards  the centre in the trunk of  the  vagus, but  separate  from
 that nerve  to be implanted  in  a large  extent  of the respiratory cen-
 tre.   This mode  of implantation of the spinal  accessory nerve serves
 to bring  the sentient surface of  the lungs and air passages into im-
 mediate  relations with  the roots of all  those  nerves which animate
 the great muscles of respiration, the phrenic, the  external  thoracic,
the cervical plexus, and the motor fibres of the spinal  accessory and
 vagus nerves.
  Respecting the subjects  discussed  in this chapter, the  systematic  works  on
descriptive Anatomy and Physiology may be consulted ; also Sir C. Bell's  and
Mayo's works, and Dr. Reid's Essays  in the Edinb. Med. and Surg. Journal; Dr.
Marshall Hall's writings ; the Article " Par Vagum," in the Cyclopaedia of Anatomy
and Physiology. 
498
INNERVATION.
                         CHAPTER XXI.

      THE SYMPATHETIC NERVE.   ITS ANATOMY AND FUNCTIONS.

  Under the title of Sympathetic nerve is comprehended a great sub-
division of  the nervous system, which presents certain peculiarities
of structure and  of distribution, whereby it is  strikingly contrasted
with the strictly cerebro-spinal nerves.
  It consists of an uninterrupted chain of ganglia, extending on each
side of the  vertebral column, from  the first cervical vertebra down to
the coccyx, and  moreover extending  upwards  beside  the cranial
vertebra?, and occupying spaces between the bones of the cranium
and those of the face.
  The ganglia are on the whole rather less numerous than the verte-
brae :  in the dorsal region there is generally a ganglion for each ver-
tebra.   The continuity of the  chain is preserved  by cords of com-
munication  which pass from one to the other: sometimes two ganglia
are, as it were,  fused together; the  chains of opposite sides com-
municate with each other at various parts in the plexuses  of nerves
which originate  from  them, and, in front  of the coccyx,  through a
single  ganglion (ganglion impar),  which is situate  in  front of that
bone; whether they communicate  at  the cephalic  extremity, or not,
is uncertain.  Ribes has described a ganglion impar upon the  ante-
rior communicating artery of  the circle of Willis, similar to that  on
the coccyx, and.  other anatomists regard  the pituitary  body in  the
sella  Turcica  as  a  ganglion of this  description, a  common  point
of  union for the  right  and left  sympathetic chains  at their cranial
extremities.
  The sympathetic nerve has very much the same general arrangement in mamma-
lia and birds as in man.  In the former the cervical portion is closely associated with
the  vagus nerve by a sheath of areolar tissue, but without interchange of fibres, ex-
cepting at its  upper portion.  In birds the  cervical portion exists only in the canal
formed  by the foramina of the transverse processes of the vertebrae.  In the batra-
chian reptiles the sympathetic is disposed as in mammalia.  In the chelonian reptiles
its ganglia are few and the lateral cords small.  In serpents it appears  to want the
distinct ganglia which exist in other animals; it is, however, continued down  the
spine on  each side,  having frequent communications with the vagus.  Numerous
plexuses occur in its course.  In the larger osseous fishes the sympathetic is sufficient-
ly distinct, as  in the cod; it is also  present in the ray; in both, but especially the
latter, it is the abdominal portion which is chiefly developed.*  In the cyclostomatous
fishes the. sympathetic is said to be wholly deficient.

  For the sake of description, the sympathetic in the human body
may be divided into the following portions :  1. The  Cephalic. 2. The
Cervical.   3. The Dorsal.   4. The Lumbar.   5. The Sacral.
   In comparing  these several portions, we find that they have cer-
tain characters in common.   Each portion consists of its proper num-
ber of  ganglia, which seems  in some  degree influenced  by the num-

   * See Mr. Swan's  beautiful Plates of the Comp. Anat. of the Nervous System. 
THE SYMPATHETIC NERVE.
499
ber of vertebrae in that region of the spine to which it belongs.   The
ganglia  are  connected  by cords of communication, which  are  not
mere nerves, but are  true extensions of the  ganglia in  a cord-like
form ; so that each lateral chain might be described as a  continuous
ganglion,  with swellings  at  certain intervals.  From each portion
certain sets  of nerves may be  pretty  constantly traced:  these are,
omitting the cords of communication between the ganglia,  1.  Visceral
nerves, which generally accompany branches of neighbouring arteries
to  the viscera.  2. Arterial  nerves, apparently devoted  to  arteries
in the vicinity of the ganglia.   3. Nerves of communication with the
cerebral or spinal  nerves, which emerge  from the  cranium or spine
near  to the ganglia.
   The visceral and arterial branches have a remarkable tendency to
form  plexuses, generally very intricate, which entwine around  the
blood-vessels,  and, in the former case, are conducted by them to the
tissue of the viscera.
   The branches of communication  with  cerebral or spinal  nerves,
are among the most remarkable connected with this portion of the
nervous system.  We have  already (p.  205) described  certain of
them as consisting  very distinctly  of two portions  or bundles, one
composed  of tubular  fibres, the other almost exclusively of gelati-
nous  fibres.  These bundles have been very commonly described as
constituting the roots of origin of this nerve.*
   On tracing back the gray bundle, connected with one of the spinal
nerves, it is found that most of its  fibres go to  the  ganglion of the
posterior root of the nerve, some passing into the anterior root.   A
few of these  fibres may be found in each root; they are not, however,
traceable into the spinal cord, but seem to connect themselves  only
with the blood-vessels of that organ.   Such is probably the  anatomical
history of  the so called gray root of the sympathetic connected with
every spinal  nerve.   It may, therefore, be more  justly regarded  as a
nerve originating from the sympathetic  ganglion, which  by some of
its  fibres connects that ganglion to the  ganglion  on the posterior
spinal root, and by others is distributed  to the vessels of the  cord.
This is the conclusion which Mr. Beck's recent researches have  led
him to adopt, and the careful examination  of his very able  dissections
induces us to believe this to be  the correct view.
  The white root, or the bundle of tubular fibres, when traced to the
spinal nerve, appears like a branch of it, i. e. a series of fibres, sepa-
rating from it,  and passing to the sympathetic.   It  derives fibres in
nearly equal  numbers from the  anterior and the posterior root.  In
every instance  it may be seen, spreading  out upon  the adjacent sym-
pathetic ganglion, passing through its vesicular matter, and following
the course of  the trunk of the  sympathetic for a longer  or shorter
way, and then proceeding from it in connection with its  gelatinous
fibres chiefly to viscera.  Mr.  Beck informs us that he can, under the
microscope, distinctly trace the  continuity of these fibres through the

  * A good figure  of these roots is given in Wutzer's work, "De Corporis humani
gangliornm  fabrica atque usu."  Wutzer does not, however, distinguish them  as
white and gray.  Berlin, 1817. 
500
INNERVATION.
ganglion, and he is of opinion that they do not form any organic con-
nection (as some fibres in ganglia and other nervous centres undoubt-
edly do) with the vesicles of the ganglion, beyond that which might
result from passing between them.   These fibres, then, according to
this  statement, must  be regarded as a branch  of the  spinal nerve,
distributed, in connection with gelatinous fibres derived from the sym-
pathetic ganglion, to viscera and other parts.
   If this view of the  anatomical  relation  between  the  sympathetic
ganglia and the  cerebro-spinal  nerves be  correct, it seems evident
that the proper sympathetic  fibres must be  viewed  as a separate por-
tion of the nervous system, consisting entirely of gelatinous or nucle-
ated fibres which originate in the vesicular matter of the sympathetic
ganglia.  These fibres, however, are accompanied in their course by
tubular fibres, derived from the cerebro-spinal  nerves, which pass
over or through  the sympathetic ganglia without forming any intimate
connection with them, and which are distributed along with the gela-
tinous fibres to viscera and other parts.
   1. Of the Cephalic portion of the Sympathetic.—This portion of the
sympathetic consists of ganglia, which occupy different parts of the
head, and are connected with each other, and with the superior cervi-
cal ganglion.  They are four in number :—
   1. The ophthalmic  ganglion.  2. The spheno-palatine, or Meckel's
ganglion.  3. The otic ganglion,  discovered by  Arnold.  4. The
submaxillary ganglion.
   The  ophthalmic, or  lenticular, or  ciliary ganglion is  found  in  the
orbit, situate on the outer side of the optic nerve, a little way before
its entrance into the eye, enveloped in soft fat.   It is a small quad-
rangular ganglion, of a reddish colour, not unlike a pellet of fat, for
which  it may be very readily mistaken by an inexperienced dissector.
   Numerous nerves proceed from the anterior angles of this ganglion
to the  eyeball.  These are the  ciliary nerves,  which have been
already described, p.  423.
   The  ophthalmic  ganglion is  connected  with the third nerve, and
with the nasal branch of the  ophthalmic division of the fifth.   The
branch of communication with the third nerve is a short thick nerve
which  comes from the inferior branch of  that nerve: it is  called by
descriptive anatomists, the short root of the  ganglion.  From the nasal
nerve proceeds the long root, a long and very delicate  nerve, which
attaches itself to  the superior posterior angle of  the  ganglion.
   We have not  examined by the microscope the constitution of these
branches of connection with the third and nasal; but it is not unin-
teresting to notice that several anatomists have remarked, in reference
to them, that the place of each is occasionally supplied by two, which
may answer to  the two connecting nerves already noticed, in  the
dorsal  portion of the sympathetic.
   By means of  a third filament called by  some the middle root, this
ganglion  is brought into connection with the cavernous  or carotid
plexus from the  superior cervical ganglion.
   The  sphenopalatine ganglion is situate  in the  pterygo-maxillary
fossa;  it is a small,  somewhat triangular, ganglion connected with 
CERVICAL PORTION OF SYMPATHETIC.
501
 the infra-orbital nerve, at its crossing over the spheno-palatine fissure,
 to pass along the  floor of  the orbit.   This connection is effected by
 two or  three short  nerves  called  commonly  the  spheno-palatine
 branches of the infra-orbital nerve.
   From this ganglion proceed, first, palatine nerves, which are  three
 in number (anterior, middle,  and posterior), which pass through the
 posterior palatine  canal, to be distributed  to the mucous membrane
 of the hard and soft palate, and  also to the nasal mucous membrane.
 Secondly, nasal branches, described by Scarpa, which enter the nose
 through the spheno-palatine foramen, and  distribute  branches to the
 spongy bones, and to the septum.  One  of these, the  naso-palatine
 nerve, passes obliquely downwards and  forwards, along the septum,
 and enters a canal in  front of the foramen incisivum, through which
 it passes  to subdivide in the mucous membrane of the hard palate.
 Thirdly, the vidian nerve, which, coming off from the posterior part of
 the ganglion,  passes  through the vidian canal, and divides into  two
 branches, the superior, or  the great superficial petrosal  nerve, which
 enters the cranium, and under cover of the  dura mater, passes through
 the hiatus Fallopii, to unite itself with the geniculate swelling of the
 portio  dura;* and  the inferior, or carotid branch, which  enters the
 plexus around the carotid  artery, and thus forms the bond of union
 between the spheno-palatine and the superior cervical ganglion; this
 latter branch is much the larger. Arnold states that this ganglion is con-
 nected with the optic nerve,  and also with the ophthalmic ganglion.
   The Otic Ganglion.—This ganglion, discovered and  described by
 Arnold, lies at the  inner  and inferior  part of  the inferior maxillary
 division of the fifth nerve, just at its exit from the foramen ovale.  It
 is connected with  this nerve  by  two filaments, which Arnold consi-
 ders to be derived from the fibres of the lesser portion of the fifth nerve.
 Besides  branches  to the internal  pterygoid, and  the  tensor  palati
 muscles, it sends a filament into  the  cranium which  passes  through
 the hiatus Fallopii into the cavity of the tympanum, and there anas-
 tomoses with the tympanic  branch of the  glosso-pharyngeal.  This is
 the lesser superficial petrosal nerve, which Arnold regards as an ema-
 nation from the glosso-pharyngeal, and  as a root for the ganglion,
 analogous to the long root  of the  ophthalmic ganglion.   The precise
 connection of this ganglion with the sympathetic has not been clearly
 made out.   It contains numerous gelatinous as well as tubular fibres,
 and its vesicles are large and distinct.
  The Submaxillary  Ganglion.—This ganglion  is occasionally re-
 placed by a  plexus of nerves.  One or two fibres from the gustatory
 nerve constitute its roots, and its principal ramifications are distributed
 to the submaxillary gland.  It is connected with the superior cervical
 ganglion through the  cavernous plexus.
  2. Of the Cervical portion of the  Sympathetic.—This consists of
three ganglia on each side, the middle of which is by no means con-
stant.  The superior is the largest,  and extends  from within an inch

  * It is probably from this source that  this swelling receives the many gelatinous
fibres already described. 
502
INNERVATION.
of the inferior orifice of the carotid canal, to  the  third cervical  ver-
tebra, and  sometimes  as low  as the fourth or fifth.   It is connected
by large branches with the first, second, and  third  cervical nerves;
from its upper extremity there passes upwards into  the carotid canal
a branch which divides into two that  accompany the carotid artery,
dividing and  subdividing as  they ascend, so as to  form a plexus
around that artery, the cavernous or carotid plexus.   With this plexus
numerous communications take place :  there is  one with Meckel's
ganglion, another with the tympanic plexus; a branch to the ophthal-
mic ganglion, and one or two large ones to the sixth nerve, which
formerly were regarded as roots of the sympathetic  from that nerve;
also one or two filaments to the third pair, and small branches attach-
ing themselves to the ramifications of the carotid  artery within the
cranium.   Communications exist between the superior cervical gan-
glion, and the several portions of the eighth pair, and the ninth  pair
at their exit from the cranium.
   Inferiorly the  superior cervical ganglion is continued into a cord
of communication with  the middle, or, when that  is wanting, with
the inferior cervical  ganglion.
   The arterial and visceral branches of the superior cervical ganglion,
are, 1. The delicate  gray nerves to the internal carotid artery, (nervi
molles of Scarpa,) which, with branches from the glosso-pharyngeal
and vagus, form a plexus round  the  internal, external and common
carotid arteries.   2.  Pharyngeal branches, which,  with filaments from
the vagus and glosso-pharyngeal, form the pharyngeal plexus.  3.  La-
ryngeal branches accompanying the superior laryngeal branch of the
vagus.   4.  A cardiac nerve,  not always present, and very variable
in size, (the superior cardiac  nerve of Scarpa,) which, either united
with a similar nerve from the middle, or inferior cervical ganglion,
or alone, passes along the carotid artery  into the  chest, to contribute
to form the plexus of nerves belonging to the heart.
   The middle cervical ganglion is very inconstant; it is placed oppo-
site the fifth or sixth cervical vertebra, and besides  the branches of
continuation with the third, fourth, and fifth cervical nerves, it gives
off one visceral  branch, namely, the  middle  cardiac nerve, (nervus
cardiacus magnus of Scarpa,) which  is the largest of the three,  and
in default of  the ganglion, comes off from the intercommunicating
cord.   This nerve  has  a similar course  to  the  inferior  one; it is
often absent, and its place is  then supplied by filaments, which take
a similar course, but  are derived from  the superior nerve, or from
the vagus.
   The inferior cervical ganglion.—This  ganglion  is situate very  low
down in the neck, and  is very deep  seated ; it corresponds to the
transverse  process  of the last cervical  vertebra,  to the head of the
first rib, and is  closely connected with  the origin  of the vertebral
artery.   It is frequently fused with the first thoracic ganglion, and is
connected  above with the middle, or, in its absence, with the supe-
rior cervical ganglion.  It is connected with the fifth, sixth, and seventh
cervical nerves, and sometimes with the first dorsal.
   The arterial and visceral branches of this ganglion are,  1.  A nerve 
THORACIC PORTION OF  SYMPATHETIC.
503
which accompanies the vertebral artery into the canal formed by the
transverse processes of the  cervical vertebrae.  This nerve  forms a
plexus round the vertebral artery,  and  communicates with branches
of the five lowest  cervical  nerves.  There  is no satisfactory  evi-
dence that this nerve passes  up to the arteries of the brain.   It seems
chiefly a  nerve to the vertebral artery, but  doubtless also  contains
fibres from the cervical spinal nerves, which probably have  a differ-
ent destination.   2. The second branch of this ganglion is the third
or inferior cardiac nerve which passes  down, frequently in company
with  the middle  cardiac nerve,  to the plexus  on  the heart.   3.
Branches which encircle  the subclavian  artery, in the  first part of
its course.
   It is worthy of note that the most important visceral  branches of
the cervical portion  of the sympathetic, are destined to an organ, the
heart, which is situated in the thorax at a considerable distance from
their source.
   3.  The Thoracic portion of the  Sympathetic consists of a series of
ganglia, corresponding, or nearly so, in number to  that of the ver-
tebrae ; the  ganglia  lie  upon the heads of the ribs, and are mostly
small in size, and triangular in form.  The first thoracic ganglion  is
often fused with the last cervical.
   Besides the  branches  of  communication with the spinal  nerves,
there are arterial branches which pass to the aorta, and there are  also
branches which pass into the pulmonary plexus.
   But the most remarkable nerves which proceed from these  ganglia,
are the greater and the lesser splanchnic nerves.
   The great splanchnic nerve arises  by separate roots, probably from
 all the thoracic ganglia, more obviously from the fifth, sixth, seventh,
 eighth, and  ninth; these roots unite to form a round cord,  as large,
 if  not larger, than the trunk of the sympathetic.   This nerve passes
 alongside of the bodies  of  the vertebrae obliquely  downwards  and
 forwards, enters the abdomen  by piercing the diaphragm, and  ends
 in a large and complex ganglion placed by  the side, and in front  of
 the aorta, close  to the  origin  of the coeliac artery; this  is  the great
 semilunar ganglion*
    The lesser splanchnic  nerve takes its  rise by two roots  from the
 eleventh and twelfth, or from the  tenth and eleventh ganglia;  it
 passes down in a similar  course to the  larger nerve,  parallel  to, and
 behind it, pierces the diaphragm, and unites with the renal plexus  of
 nerves, and with the aortic plexus.

   * The composition of this nerve deserves particular attention as  illustrating the
 compound nature of the ramifications of the sympathetic.  It may  be regarded as
 the aggregate of a series of visceral nerves proceeding from the intercostal nerves,
 each of which, as it passes over the sympathetic ganglion immediately adjacent to the
 nerve from which it arises, becomes associated  with some gelatinous fibres.  Thus,
 while each intercostal nerve contributes certain tubular fibres, each thoracic ganglion
 contributes gelatinous fibres.  Sometimes these two sets of fibres are kept distinct,
 and the splanchnic nerve consists obviously of a white and a gray portion.  The gela-
 tinous fibres are considerably  more numerous at the lower than at the upper part of
 the splanchnic nerve, as pointed out by Mr. Beck, who very justly cites the fact as
 strongly confirmatory of the statement that these fibres arise from the ganglia.—Phil.
 Trans., 1846, p. 224 
504
INNERVATION.
   The striking analogy between these nerves and the cardiac nerves
 cannot fail to attract the  attention even of the  most superficial ob-
 server.   The latter nerves, distributed to an important organ in the
 thorax, have their rise in the  neck; and the splanchnic nerves, de-
 riving their origin from nearly all the thoracic  ganglia, are devoted
 to important viscera of the abdomen.
   Of the Lumbar and Sacral portions of the Sympathetic.—The chain
 may be followed  down  to the coccyx; the lumbar ganglia are small
 and irregular in number.  The continuity of the chain between the
 lumbar and dorsal segments, is maintained  sometimes by  a small in-
 tercommunicating cord, between the last dorsal and first lumbar gan-
 glion, which pierces the  diaphragm, sometimes by a branch of the
 greater or  lesser  splanchnic, which of course establishes the conti-
 nuity indirectly.  The branches  of  communication of these nerves
 with  the lumbar spinal  nerves, are sufficiently distinct, and some of
 them are of great length.  The gray branches are, according to Beck,
 larger than the corresponding  ones in the thorax.
   The  nerves which  come from the lumbar portion of the sympa-
 thetic are  destined  to the  aorta, and  to  the  lumbar  arteries; the
 greater  part of them form a plexus around the aorta, between the
 mesenteric arteries, from  which  proceed fibres to form the inferior
 mesenteric plexus, which follows the inferior mesenteric artery; below
 this artery the aorta is still embraced by a plexus (inferior aortic
plexus) which divides into the hypogastric plexuses, one on the right
 and the other on the left, which  supply the rectum and bladder, the
 organs  of  generation, and the accessory parts.   At the base of the
 coccyx, the sympathetic  of  the right side  anastomoses with that of
 the left by means of a branch passing on each side from the last sacral
 ganglion to a ganglion  in front of the  coccyx, which  is called the
ganglion impar.
   Of the Thoracic and Abdominal Plexuses.—So large a portion of the
 sympathetic is distributed to  viscera in the  thorax  and abdomen,
 that it may not improperly be designated  as the  visceral nerve; for
those organs, upon which  the great processes which contribute to the
 nutrition of the body so  much  depend, derive their nerves mainly
 from this source, and whatever cerebro-spinal fibres they receive, are
 distributed to them  in intimate association with the proper filaments
 of the sympathetic.
   The plexuses in the thorax which derive nerves from the  sympa-
thetic are the pulmonary plexus, and the cardiac plexus.
   The pulmonary plexus is chiefly formed by branches of  the vagus,
interlacing with  each  other from opposite  sides  along the  median
plane.  It  occupies two planes, one anterior to the bronchi constitut-
ing the anterior pulmonary plexus, the other posterior, which is much
 the more considerable, and lies behind the bronchi.   To these, but
 especially  to  the latter, nerves  pass off from  the higher thoracic
 ganglia.
   The cardiac plexus is almost wholly derived from the sympathetic,
only a few  of its fibres coming from the cardiac branches of the vagi.
It is very remarkable that all the  nerves which the sympathetic con- 
PLEXUSES OF THE SYMPATHETIC.
505
tributes to this plexus, are derived  from the cervical, and not from
the thoracic ganglia.   The plexus resulting  from the anastomoses of
these nerves, occupies an anterior and a posterior plane ; the  former
passing in front of the great arteries, and following the course of  the
anterior coronary artery, in  the anterior groove of the heart.  The
plexus entwines around this artery and its ramifications, and its fibres
are doubtless conducted by them to the muscular fibres of the heart.
The posterior plexus follows the course of the right coronary artery,
and of its branches, which lies in the posterior fissure of the heart.
A plexus  of fibres, occupying a position intermediate  to  these plex-
uses, lies  behind the arch of the aorta, above the right pulmonary, and
sends a considerable plexus of nerves to the auricles.  This plexus
was described by Haller, as the great cardiac plexus.
   Several small ganglia, or gangliola, are found in connection with
the nerves of the  heart.   Wrisberg described one just  above  the
arch of the  aorta, at  the junction  of anastomosing fibres  from  the
superior cardiac nerves.  A ganglion is also sometimes found in  the
plexus  in front of the auricles,  and Remak describes and  figures
several  small ganglia upon the subdivisions of the  anterior and pos-
terior cardiac plexuses, and in the  muscular substance of the heart.
Muller'1 s Archiv., 1844.
   The nervous plexuses in the abdomen are extremely complicated
and numerous.  They are principally derivedTfrom two  great gan-
glia, situate  on each  side of the caeliac axis, in front  of the aorta.
These ganglia are semilunar in shape, convex downwards and out-
wards;  they unite  below the  caeliac  axis;  and chiefly  from their
convex border, a vast radiation of plexiform nerves takes place, which
follow the course of, and entwine around the branches of the caeliac
axis, and  of other branches  of the  aorta.  To this  great  radiation
anatomists have given the name of solar plexus, and the conjoint semi-
lunar ganglia must be  looked upon as the great centre,—the  sun of
the abdominal sympathetic system.
   Plexuses  radiate from this source around the principal branches
of the aorta, and they are named after the arteries which they accom-
pany.   They are the diaphragmatic or phrenic; the supra-renal;  the
caliac;  which divides into the hepatic, gastric  and  splenic;  the supe-
rior mesenteric, from which proceed nerves, which, with  others from
the lumbar portion  of the sympathetic, form the inferior mesenteric
plexus;  and the renal plexuses, from which  chiefly are derived  the
spermatic  plexuses, destined to the  ovaries  in the female, and  the
testicles in the male.   Of these plexuses the following are deserving
a more particular notice:
   The gastric plexus accompanies the coronary artery of the stomach,
and passes along the lesser curvature of that organ.  With the gastric
branches  of the vagus it forms the principal  nervous supply to  the
stomach, which is completed  by  an off-shoot surrounding  the right
gastro-epiploic artery from the hepatic  plexus, and by other  nerves
from  the  same  plexus distributed  chiefly  to the  pylorus, and  by
branches from the  splenic plexus.
   The hepatic plexus follows the  hepatic  artery and the vena portse
     33 
506
INNERVATION.
into the substance of the liver; it is joined by a branch of the vagus ;
and it gives off nerves to the stomach, and  to the pancreas.
   The splenic plexus surrounds the splenic  artery, supplies the pan-
creas, and the left extremity  of the stomach, by entwining round the
the left gastro-epiploic artery, and by direct branches to the great cul-
de-sac of the stomach.   These  nerves then follow the  branches of
the splenic artery into the spleen.
   The superior mesenteric plexus supplies the greatest portion of the
intestinal  canal, entwining around the superior mesenteric artery and
its ramifications.  Connected with it  are some  ganglia of variable
size, called caliac or mesenteric ganglia.   From  these ganglia, and
from the upper part of the plexus, nerves are derived to the pancreas,
and to the duodenum.
   The branches of  this  plexus which pass between the laminae  of
the mesentery do not accompany the smaller branches of the arteries
so  closely as elsewhere.   They anastomose by  arches,  from which
small branches pass to the intestine.   The  precise mode of termi-
nation of  these  nerves in the tunics  of the  intestines has not been
ascertained.
   In the pelvis we find  a remarkably complicated plexiform arrange-
ment of  nerves  distributed  to the viscera  of  that cavity.   These
nerves are derived  from  the  hypogastric  and from the  inferior me-
senteric (p. 504),  and  receive many  fibres  from  the sacral  nerves,
which latter fibres are  principally distributed  to  the pelvic plexus, a
name given by Mr.  Beck to  an intricate anastomosis  of nerves and
small ganglia distributed  to  the rectum, bladder, and vagina.  This
plexus derives  its nerves from  the  lower part  of the  hypogastric
plexus, and from the branches of the  sacral plexus.
   A very important  peculiarity of all the plexuses, wherever found,
of the sympathetic nerve, consists in  the  presence of a quantity of
vesicular  matter in them,  deposited in  ganglia of very variable size,
sometimes extremely minute,  very rarely of great size, which are
found scattered amongst them.  These ganglia appear to give origin
to gelatinous fibres.  The plexuses, therefore, have the double office
of intermingling fibres from different sources, and of affording points
of origin  for new nerve fibres.
   Function of the Sympathetic Nerve.—In  considering the function
of this portion of  the nervous system, it is of the utmost importance
to pay close attention to the facts which the  anatomical analysis of it
discloses.
   These facts are, that  it contains a vast number of centres  to and
from which nerves proceed, and in which, it may be stated  almost
with certainly, gelatinous fibres originate: that in nearly every part
of it two kinds of fibres exist, the gelatinous and the tubular; that
the tubular are derived from  the cerebro-spinal centre, the gelatinous
from the sympathetic ganglia.
   Two questions are to be solved in reference to the sympathetic.
   1.  Is the sympathetic  a distinct and independent portion  of the
nervous system ? or is it merely an off-shoot from  the brain and spinal
cord, exhibiting certain peculiarities of arrangement? 
FUNCTION OF THE SYMPATHETIC.            507
  2. Do its fibres exhibit the same powers as those of cerebro-spinal
nerves? that is, are they sensitive and motor?
  I. No physiological question has  been more  amply discussed  of
late years than that of the relation of the sympathetic to the cerebro-
spinal centres.
  The view, which we regard as the correct one, rests entirely upon
the facts of anatomy already stated.   These facts lead us to consider
the sympathetic nerve a compound  nerve, consisting of gelatinous
fibres, which are derived from the vesicular  matter  of the ganglia,
and of tubular fibres,  proceeding from the spinal cord.  These fibres
are bound  together in the same sheath, and whatever be the proper
function of each, they bear  to  each  other a similar  relation  to that
which  the anterior and  posterior  roots  of spinal nerves do in the
compound  nerve.   Originating from different sources, and possess-
ing probably different endowments,  they travel  in company to  their
several destinations.
  We are aware that  some  physiologists of  high and  deserved re-
pute altogether deny that the gelatinous fibres, which  we have de-
scribed  as entering so largely into the constitution of the sympathetic,
are nervous.  They  regard them as an early  stage of fibrous  or
areolar tissue.  The following reasons appear to us quite decisive of
the nervous nature of these fibres.   1.  They may be distinctly traced
to the vesicular matter of ganglia;  it is immaterial  to the question
whether they  form their connection with the  sheaths or with the
vesicles  themselves,  for we are as  much at liberty  to regard the
nucleated envelope of the vesicles as a structure  essentially nervous
as the vesicles themselves.   Parts of the encephalon appear to consist
of little else than  nuclei.
  2. Throughout the  sympathetic system these fibres and the  tubular
fibres exist in the several nerves in different but determinate numbers.
Sometimes the two kinds are equal, sometimes one predominates over
the other;  sometimes  the nerves consist  solely of gelatinous fibres.
Now if these latter performed the office of a sheath or support to the
others, they would always be in due proportion to each other.  More-
over, the gelatihous fibres would be  always  outside, enveloping the
tubular, which is not  at all uniformly the case.
   3. Nucleated  fibres, very similar  to  the gelatinous  fibres of the
sympathetic, exist in parts where their nervous character is indubitable,
as in the olfactory filaments  (p. 397), and the  nerve in the axis of the
Pacinian corpuscle exhibits very much the  same  appearance,  save
that it is devoid of  nuclei.
  Adopting this view of the compound nature   of the  sympathetic,
it is obviously impossible to regard  it either as independent of the
cerebro-spinal centres, or wholly depending on  them.   It seems pro-
bable that it is independent of them  as  regards its gelatinous fibres,
but dependent on them as regards its tubular fibres.
   And  it may be stated  that  the views of anatomy which we hold
to be correct, justify us in  affirming that the   sympathetic exhibits
marked indications if not of independence, yet of great peculiarity,
in  its mode of distribution.  Clinging to  the coats of arteries, it 
508
INNERVATION.
follows them  for the most part in their  ramifications, and  attaches
itself to them somewhat as ivy does to a tree.   Yet of the mode of
termination of the  gelatinous fibres of the  sympathetic, and of the
nature of their relations with the elements of the tissues among which
they lie, nothing certain  is known ;  a fact attributable in a  great
degree  to their want of such  obviously distinctive characters as the
tubular fibres possess.  These latter, after leaving the blood-vessels,
are probably  distributed  either to sentient surfaces or to muscles in
the ordinary way.
   The  proper mode, then, of stating the reply to this question seems
to us to be:  that the sympathetic, taken as a whole, is  not in itself a
special and independent nervous system, but a portion of the nervous
system  peculiar  in  its composition, having, as  regards  some of its
constituent fibres,  a special  relation to   blood-vessels,  particularly
arteries, (and these are  the  fibres  which  are  independent of the
cerebro-spinal centres, having distinct centres of their own,) but being
by others of  its  fibres connected, as all  other nerves are, with the
cerebro-spinal centres.
   II. The second  question  affects the endowments  of the consti-
tuent fibres of the sympathetic.
   If we interrogate anatomy, we  learn that the  ramifications of this
nerve are distributed to muscles as well as to sentient surfaces.  The
heart, for instance,  derives its  principal  supply of nerves  from this
source.   The  intestinal  canal  between the stomach and the lowest
part of the colon receives no nerves  direct from  the  cerebro-spinal
system, and is therefore  dependent solely on the sympathetic, for
whatever of sensibility it enjoys,  or for such motor power as may be
usually called into action  by nervous influence.  We, therefore, must
infer from anatomy that the  sympathetic  contains  both sensitive and
motor fibres.
   Many experiments lead to  a similar conclusion.  Stimulation of
the cervical  ganglia excites the heart to  increased action;  and irri-
tation  of the  splanchnic  nerves causes increased  vermicular motion
•in the stomach and  intestinal  canal.   Muller proved a similar result
to ensue upon irritation  of  the caeliac ganglion.   He exposed the
intestines, and likewise  the caeliac ganglion  in a rabbit; he waited
until the increase  of peristaltic  action,  which  exposure to the  air
always produces, had subsided, and then he applied  potassa fusa to
the  ganglion, when immediately  the  peristaltic movements became
very vigorous.   There is less agreement  in  the  statements  of the
results  obtained by different  experimenters as to the sensibility of
these nerves, as  indeed  is very commonly the case, when the  ques-
tion is  respecting sensation;  but  the well known occurrence of pain
in parts supplied only by the  sympathetic, is  alone more conclusive
 as to the existence  of sensitive fibres  in that nerve, than the results
 of any experiment  on a  brute animal.  How exquisite are the suf-
 ferings of patients labouring under  colic, or  the  passage of a gall-
 stone,  or of  a renal calculus!
   It is plain, then,  that  the  sympathetic  nerve  contains both motor
 and sensitive fibres.  An appeal  to common experience shows us, 
FUNCTIONS OF THE SYMPATHETIC.
509
that  the  latter  cannot be very numerous,  as parts supplied by  the
sympathetic nerve are not, in  the healthy state, highly sensitive, and
pain is felt in them only under the influence of great irritation.  And
with regard to the motor fibres, it shows that they are not at all, or at
most to a very  trifling extent, under the influence of the will.   It is
true  that the will may be  brought to bear upon muscles  supplied by
the sympathetic, by directing  it simultaneously upon other distinctly
voluntary muscles.  This is well illustrated  in the case of the iris;
no effort, however great, if directed solely upon the  iris, will  cause
that  muscle to contract, but if the voluntary  influence cause a simul-
taneous  contraction of the internal rectus muscle of the  eye, con-
traction of the  pupil will take place upon each adduction of the eye-
ball.
   It is highly probable that  the increase in  force  and in  frequency
which takes place in  the heart's action, during active exercise, is to
be explained on the  same principle; and  that a strong  effort of the
will  directed to the  abdominal muscles,  may  excite  an  increased
peristaltic action of the intestines.
   Muscles  supplied by the sympathetic nerve, although  under ordi-
nary circumstances referable to  the category of involuntary muscles,
must not then be considered as absolutely and entirely removed from
the influence of the will.
   A very striking peculiarity, dependent in part probably upon the ana-
tomical  arrangements of the sympathetic, consists  in the rhythmical
nature of the movements of parts which derive their supply of nerves
from this source, of which the movements of the heart and the intesti-
nal canal afford  good examples.   And it  is an  important  feature of
these actions that they take  place even when the parts are discon-
nected from the main portion of the sympathetic  system.  It  is well
known that the heart's action  will go on for a considerable time after
it has been removed  from the  body ; and that  the peristaltic move-
ments of the intestines will continue under similar circumstances.
   This peculiarity seems to be referable to a double  cause; first, the
disposition  of the  muscular fibres  themselves, which is such  that a
contraction cannot take place at one part without affecting the adjacent
fibres, so that the contraction  of one set of fibres appears to stimulate
those  in their  immediate vicinity.  This  progressive contraction  is
well seen  in the intestines.   Secondly, the frequent occurrence  of
small ganglia,  not only among  the plexuses of the sympathetic, but
also, as in the  heart,  upon or  among the muscular fibres themselves.
These ganglia, it is reasonable  to suppose, are so  many little  maga-
zines of nervous force, which,  by their intimate  connection with the
muscular fibres  themselves,  render them  capable  of repeating their
action at intervals, after their disconnection from the main trunk of the
sympathetic .system.
   Much, however, in the peristaltic actions, is perhaps, due  to the
peculiar constitution  of the unstriped  muscular  fibre itself; a consti-
tution which gives it a slow and enduring, rather than a quick, ener-
getic, and  fleeting contraction.   The actions of the heart are inter-
mediate to those of the intestine and of voluntary muscle, and so are 
510
INNERVATION.
its muscular fibres, which, while they exhibit the striped  appearance
of voluntary muscle, are nevertheless devoid of the sarcolemma, and
interlace in a peculiar manner with each other.  The gelatinous nerve-
fibres exhibit the same apparent  inferiority of organization as the
unstriped muscular  fibre.   It is a remarkable  confirmation  of  these
views, that in the tench (Cyprinus tinea), according to Ed. Weber, in
whicji the muscular fibres of the alimentary canal are of the striped
kind, there is no peristaltic action of the intestines,  and  that the
application of a rapid succession of electrical shocks from a magneto-
electric rotation instrument causes that sudden  and quick contraction
which characterizes the striped muscular fibre.*
   An observation made by Pourfour du Petit,f many years ago, sug-
gested an office of the sympathetic, distinct from sensation or ordinary
motion, but apparently  not less important than either.   He found that
the division of the trunk  of the sympathetic  in  dogs, opposite the
third  or fourth cervical  vertebrae, was followed, with  remarkable
rapidity, by a disturbance  of the circulation in the eyeball; giving
rise to a swollen and apparently inflamed state of the conjunctiva, a
contracted state  of  the pupil,  a flattening of the cornea, and a re-
traction of the eyeball,  with protrusion of the fold of the conjunctiva,
known by the name of the haw, and  a flow of tears.   Dupuy found
similar effects resulting from the extirpation  of the superior cervical
ganglion in horses; and when the ganglia on both sides were removed,
there were superadded  to these more  local effects, a general emacia-
tion along with an anasarcous state of the limbs, and an eruption over
the whole cutaneous surface.
   Dr. J. Reid confirms these results of section of  one sympathetic
in the neck, as far as regards the eye, and  he agrees with  the  other
observers in  stating  that the injected state of the  conjunctiva fol-
lowed immediately after  the section.  In one case,  he  states that
the redness of the conjunctiva  took place  a few minutes after the
operation.
   It has been already stated, that section of the branches  of the fifth
nerve, which supply the eye, is followed by ulceration and other signs
of impaired nutrition in the eyeball.  But  these changes do not take
place for some  time after the section of the nerve; generally  many
days elapse :  and they are  attributable to  the  presence of irritating
particles, which, owing to the insensible state of the conjunctiva, are
suffered to remain in contact with  the surface of  the eye, giving rise
to inflammation and ulceration of its textures.  The effects of section
of the sympathetic are immediate; and are probably due to a change
produced in the  blood-vessels,  in  consequence of the withdrawal of
their accustomed nervous influence.
  The sympathetic thus appears to exercise a  threefold office: first,

  * By experiments with the  magneto-electric  instrument, E. Weber has given
additional illustration of the fact that the peristaltic contraction is characteristic of
the unstriped fibre, and  that the sudden  and quick contraction is peculiar  to the
striped fibre.   See his elaborate article " Mnskelbewegung" in Wagner's Handwiir-
terbuch, 1846, and our remarks at pp. 146,149, 150.
  f Histoire de l'Acad. Royal des Sciences, an 1727, &c.  Lettres concernant des
reflexions sur les decouvertes faites sur les yeux, 1732. 
FUNCTIONS OF THE SYMPATHETIC.
511
 that of a  sensitive nerve to the parts to which it is  distributed;
 secondly,  that of  a  motor nerve for certain muscular  parts ;  and,
 thirdly, that of a nerve to the blood-vessels.  It is  almost certain
 that blood-vessels enjoy  in  their  coats  a  power  of contractility-;
 and it  seems  highly  probable  that  these nerve-fibres  exercise an
 influence upon that  contractility.  Such an influence, it is evident,
 would  materially affect the  nutrition of parts  the  blood-vessels of
 which are subject  to  it;  and, as secretion is mainly  dependent on
 the normal nutrition  of glands, it is reasonable  to suppose that that
 function likewise would be  to  a certain extent controlled by these
 nerves.
   It remains to inquire the sources whence  these various classes of
 fibres in the sympathetic respectively derive  their powers.
   Looking to the anatomy of the  nerve, there can  be no doubt that
 some fibres are derived from the spinal  cord or medulla oblongata,
 and that others proceed from  the sympathetic ganglia.   The motor
 and sensitive  fibres,  and some  of those going to the other muscular
 parts, belong, no doubt, to the  former class; the  vascular, with the
 highest probability, to the  latter.
   Valentin's experiments  indicate that  the  roots  of the encephalic
 and spinal nerves exert considerable  influence  upon the movements
 of parts supplied by the sympathetic.  For instance, irritation of the
 roots of the first three or four cervical nerves, excites increased action
 of the heart; and that of the dorsal and lumbar spinal nerves stimu-
 lates the peristaltic action of the intestines  through the splanchnic
 nerves, and the abdominal plexuses.
   The effects of diseased states of the spinal cord also afford a sup-
 port, which is more to be relied upon than  the previous experiments,
 to the opinion that  the motor and  sensitive fibres of the sympathetic
 are implanted  in the  spinal cord.  When there has been extensive
 lesion of the cord, from injury or disease,  the intestinal canal is always
 affected to a degree proportional to the extent of the lesion ; and this
 affection shows itself in the torpor of the intestines, and the readiness
 with which they become distended by flatus, giving rise to the tym-
 panitic condition of abdomen, which so generally attends disease  or
 injury of the spinal cord.
   It had long been thought that the  sympathetic nerve plays an im-
 portant part in the sympathies of the body.  Our  improved knowledge
 of the anatomical distribution  of the nerves, and of their physiological
 anatomy, and of their  endowments, clearly shows that the phenomena
 of sympathy are  explicable by the known  laws  of action of the great
 nervous centres, and  that  the  sympathetic nerve  can take no more
 prominent  part in  it  than  any other  nerve ;  the extent to which it
 or any other  nerve  may be engaged  in the play of  such sympathies
 beino- proportioned directly to the extent of its  central as well  as its
peripheral connections.
  It would  be more  consistent, therefore, with  a scientific nomen-
clature to discard the  term Sympathetic as applied  to this nerve; the
old name Intercostal would, in some respects, be preferable.   There
is, however, great difficulty in finding a name which would adequately 
512
DIGESTION.
express  its constitution and offices, which may be  summed  up as
follows.
   1.  In its constitution it is compound, consisting  of tubular fibres
and of gelatinous fibres.
   2.  In its offices, it is a motor nerve to many of the internal viscera
of the body,  the  heart  and  the  intestinal canal especially;  it is also
a sensitive nerve to these parts; and it presides  over the  actions of
the blood-vessels of these as well as of other parts where it is dis-
tributed, as of the head and neck, and likewise of all the  principal
glands of the body.

  On the Sympathetic nerve, consult Cruveilhier, Anat. Descr.; Valentin, in Soemmer-
ring, Anat.; Longet,  Syst. Nerveux ; Lobstein, de nervi  sympath. fabrica, &c;  Val-
entin de function, nerv. cerebr. et  sympath.;  Mr. Beck, paper in the Phil. Trans, for
1846; Miiller's  Physiology; Bidder und Volkmann, die Selbstiindigkeitdes sympa-
thischen Nervensystems, Leipzig,  1842; Kolliker, die Selbstilndigkeit und Abhilngig-
keit des sympathischen Nervensystems, Zurich,  1844; Purkinje, in Miiller's Archiv.
for 1845, and translated in theLond.Med. Gazette, vol.xxxvi., has described nervous
ramifications which  he considers  to belong  to the sympathetic, in the  pia mater,
dura mater, serous membranes, and other parts.  Mr.  Rainey also describes (Med.,
Chir. Trans, vol. xxix.) the arachnoid and subarachnoid tissue as consisting almost
entirely of such nerves, a view which it is impossible  for us to adopt.  Much yet*
remains to be cleared up as regards the anatomical history of the sympathetic nerve
in particular parts.   Monographs upon the nerves of the heart, of the stomach, the
intestines, &c, are great desiderata, founded on  careful and  minute dissections, by
experienced anatomists, with the aid of the microscope.  Further researches are like-
wise required on its distribution to the extremities.
                         CHAPTER XXII.

GENERAL VIEW OF THE FUNCTION OF DIGESTION.--OF THE MINOR FUNC-
   TIONS WHICH  CONTRIBUTE TO  IT.--OF  FOOD.--ITS  QUALITY.—ITS
   QUANTITY.

   Having discusesd the  great animal functions of Locomotion and
Innervation, we now commence the consideration of those organic
functions which are more directly concerned  in maintaining the nu-
trition, and, consequently, the life of the individual.
   Of the nutritive processes, the function of Digestion is clearly the
most prominent  and most important, inasmuch as it  is that  through
which the animal is enabled to receive the aliment, and to prepare it
for being assimilated to, and appropriated by, the various  textures and
organs of the body.
   Under the  general  expression, "function of Digestion," must be
comprehended several minor processes, all tending to the same object,
namely, the reduction  of  the food for the nourishment of  the  body.
The number of these subordinate processes varies with the degree of
complication of the digestive function,  which is obviously influenced 
FUNCTION OF  DIGESTION.
513
 by the complicated nature of the animal's body, and by the part which
 it has to play  in the  economy of the world.
   Taking the digestive process, in its highest degree  of complexity
 in man and the mammalia, we find  that there is provision, first, for
 the prehension of the food ;  secondly, for its mechanical division and
 comminution (mastication), and for its admixture with a peculiar fluid
 (insalivation); thirdly, for the conveyance  of the  food into that por-
 tion  of the alimentary-canal in which its principal chemical changes
 are to take place (deglutition); fourthly, for the solution and reduction
 of the food  preparatory to its being brought into a condition  favour-
 able to absorption (chymification);  fifthly, for the separation of  a ma-
 terial which shall contain in  a condensed  form  the chief nutritive
 principles of  the  food, and which  is  easily absorbed into the  blood
 (chylification); and  lastly, for  the removal of such portions of the
 food as have not  been  absorbed into the  system  during its  passage
 along the alimentary canal (defacation).

  In examining the digestive process in the inferior classes of animals, various mo-
 difications are  found  lo take place in it, according  to peculiarities in  the  habits of
 the animals, or in the nature of their food; and  also according to the complexity of
 organization exhibited by them.
  In Mammalia, modifications occur in the masticatory process ; the vegetable feeder
 requiring a more complicated dental apparatus; the carnivora being provided with
 teeth of a simpler construction, but more fitted for seizing and lacerating  the prey.
 In others, again,  the teeth are adapted to feed  on  insects, the Insectivora; in others,
 the Rodentia, certain teeth are constructed for gnawing dry and resisting substances ;
 whilst in some of the whales, there are no teeth at all, strictly speaking, but only an
 apparatus which  will  allow of retaining the finer kinds of food in their passage into
 the mouth of the animal.  The other sub-processes of digestion are carried on very
 much upon the same plan as in the human subject, with only such variations as the
 habits of life of the animals may render necessary.  Thus, in a large tribe  of Mam-
 mals, the Ruminantia, the food is macerated in a complex stomach, prior to, as well
 as after, it has been subjected  to a more  complete mastication  than  is employed in
 any other animals.  In these, as well as in all vegetable feeders, the intestinal canal
 is very long and capacious, and  the ccecum  of great size.  In the  Carnivora  the
 stomach is simple, and the intestines short and narrow.
  In Birds there are no teeth; and mastication, properly so called, is effected in  the
 stomach, a portion of which (the gizzard) acquires a great increase  of muscular
 power, and is  lined by a dense cuticle, and thus  becomes a powerful organ  for
 triturating the food, the bird swallowing pieces of flint or other hard substances to
 aid the mechanical reduction.   Insalivation is but slightly developed, excepting in the
 woodpecker, where very  large  salivary glands pour out a  considerable quantity  of
 saliva to aid the bird in picking the dry bark and wood of trees.  In some birds, how-
 ever, a dilated portion of the oesophagus (the crop) gives lodgment to the food for a
 time, and pours out from its mucous membrane a  fluid which probably performs an
 office  similar to that of the saliva, and which at least  must serve to moisten the food
 before it passes further along the  digestive tube.  Chymification  and chylification
 are essentially the same as in Mammals; and there are likewise similar differences
 as regards the length and development of the intestinal lube  in  carnivorous and
 herbivorous birds.  In Reptiles the digestive process is, on the whole, simpler than in
 the preceding classes; but there are the same sub-processes, the  alimentary canal
 being  of a simple construction.  The dental apparatus varies according to  the mode
 of life of the reptile, (the  fangs of serpents having evident reference to the predatory
habits of that class of reptiles,) excepting  so  far as  the beak may be  regarded as a
substitute; and in some, as the chelonia, it is entirely absent.  In Fishes there are well
developed teeth of various forms, and often very numerous, with a simple stomach
and intestine, but no salivary apparatus.
  In the higher Invertebrata the  digestive process is carried on upon the same plan as
in the vertebrata.  In  the Cephalopods, there are powerful instruments of prehension
in the arms or tentacles which surround the animal's mouth and head.  These 
514
DIGESTION.
animals enjoy a certain power of mastication by teeth, and some of them have a
gizzard. All the Mollusca have a large liver; but other glandular organs connected
with the intestinal canal, and more or less subservient to digestion, namely, the
pancreas and  spleen, are absent.  The  stomach and inteslinal tube are very much
as in the vertebrata.  The articulata have also a digestive system like that in the
vertebrate classes, but the liver is small, and developed in the rudimentary form of
coecal tubes opening into the intestine.
  In the lower Invertebrata digestion  becomes  very simple.  The intestine  and
stomach become much reduced in size; and in some the  digestive  apparatus con-
sists only of a simple bag, as  in the fresh water polyps, having the same orifice of
entrance and exit; or, of a series of sacs or bags, with certain tubular appendages,
as in the Asterias, and in the Actinia; in these latter animals one  orifice answers
equally for the introduction of the food, and for the discharge  of the superfluous
matters. In Medusa, the oral aperture  leads to a capacious cavity or stomach,
from which certain canals carry the nutritious material into the different parts of the
body; these canals being probably analogous to the circulating systems of the higher
animals. In some polyps, the Bryozoa, as shown by Dr.  Arthur Farre, a portion
of the stomach exhibits  great  muscular power, and seems to perform the function
of a gizzard.
   We shall  find it convenient to examine the function of digestion by
tracing it through the various stages, as above enumerated, describing
the mechanism  of each of the subordinate processes,  and the change
which each  of  them is capable of  effecting in the food.
   Before  we enter upon  these  points, we must  make some remarks
upon the  nature and quantity of the food suitable for the  nourishment
of  man.
   It  has  been  already remarked  at a former page (p. 59), that no
food is suitable for the support of the human frame in a healthy state,
but that which  contains the great  staminal principles, which are the
chief  constituents of the  body.   And  the  same  remark applies with
equal force to the carnivorous, and probably to the herbivorous classes
of  animals.
   The food  of the lower animals varies to  a remarkable extent.   But
nearly, if not entirely, throughout the series, organized matter, either
vegetable  or animal, forms the proper nutrient  material.   It is pro-
bable that some of the lowest creatures enjoy the  power of assimi-
lating inorganic matter, and thus  become the instruments of making
the inorganic substances indirectly subservient to the nutrition of the
higher animals.
   The elements of nutrition for man, and the higher classes of ani-
mals, exist in the vegetable as well as in the animal kingdom.   But
some animals are so  constituted,  that, in a state of nature, they sub-
sist only on  the flesh  of other animals; while  others  live only upon
vegetable food.    Some carnivorous animals, however, may, in a state
of domestication, be  brought to  eat vegetable  food;  but it rarely, if
ever, happens  that the herbivora  can  be  taught to eat animal food.
Man is, by nature, a truly omnivorous  animal;  and a certain admix-
ture of animal  and vegetable  food  is known, by experience, to  be
that which is most conducive to his healthy nourishment.
   The classification  of food which  Dr.  Prout  has  adopted, appears
to us to be eminently practical—and on  that account  we recommend
it to the  attention of our readers.  As  water  enters so largely into
the constitution of the body, being essential to  the integrity and to
the vital action  of the solids, and as it forms the principal part of the 
CLASSIFICATION OF FOOD.
515
  blood, it is necessary that all animals should be supplied with liquid
  food in some shape.  Accordingly,  water,  either alone or holding
  important nutrient elements in suspension or solution, forms part of
  the food of all  animals—the aqueous group of alimentary materials
  of Prout.                                             J
    A large number of substances derived  from the vegetable kingdom,
  constitute the saccharine group of Dr. Prout.   These are character-
  ized by being composed of carbon, united to hydrogen and  oxygen,
  in the proportions in which these latter elements form water; the pro-
  portion  of the carbon varying from  30 to 50 per cent.   (See ProuVs
  papers in the Phil.  Trans.)   This group  comprehends sugars, starch,
  gums,  vinegar.    These  substances  are  contained  in vegetables  of
  various  kinds, sometimes forming their principal  constituent, and at
  other times combined with other nutrient principles.
    The oily or oleaginous group of alimentary  substances comprehends
  all those substances whose  composition  consists of defiant gas and
  water.   It includes  the various fats and oils, as well as alcohol.   It
  resembles in ultimate constitution the saccharine group ;  the propor-
  tion of carbon in the various substances  contained in it varying from
  60 to 80 per cent.                                         b
    A fourth group, the albuminous, is  made up of all those substances
  which  contain nitrogen—such as fibrine, gelatine, albumen, caseine,
  vegetable gluten.   All the  materials  which make  up this group are
  derived generally from the animal kingdom, with the exception of the
  last, which is contained in great abundance in wheat; similar, if not
  identical, principles exist  in vegetables.   Wheat, indeed, consists of
  two  substances—one  referable to the saccharine group, the  other to
  the albuminous, the former consisting of starch,  the latter of gluten.
  This fact was recognized  more than a  century ago (an. 1742) by Bec-
  caria, who assigned  the glutinous portion  to the nourishment of the
  nitrogenous tissues of the body.  (Dr. Thomson, Med. Chir. Trans.
  1846.)                                                         3
   In milk we find a natural combination of all the various substances
 employed for nutrition—and  it is a fact  of the highest  interest that
 this product of animal secretion, elaborated  for the nourishment of the
 young, should contain one or more substances for each of  the above-
 named  groups of alimentary materials.
   Thus, milk consists of water, sugar, oily  matters (butter), caseine ;
 and wheat, a substance of almost  universal application for food, ex-
 hibits an analogous union  of starch, the representative of the saccha-
 rine group—and of gluten, representing the albuminous.
   It must be borne in mind that the albuminous  aliments  are distin-
 guished from those of other groups by their containing nitrogen.  Food
 of this kind is especially fitted to be directly  assimilated  to  muscle,
 nerve, and the other  animal  tissues, into  the composition of which
 nitrogen enters largely.   These  aliments  contribute directly to the
 formation of the blood, from which the tissues attract  the  principles
 most proper for their nourishment.   '
  The non-nitrogenous aliments are obviously fitted  to nourish those
textures which do not contain nitrogen, as the fat; or to supply those 
516
DIGESTION.
secretions in which carbon abounds,  as  the bile.   Moreover,  they
furijish  those large supplies of carbon which, we  are warranted in
supposing, the  animal economy stands greatly in need of, not only
from the great amount of that element which is to be found in all the
tissues,  but also from the large excretion of carbonic acid which is
constantly taking place from the respiratory and  other surfaces of the
animal body.  The formation of carbonic acid in the economy by the
union of carbon and oxygen is, no doubt, the immediate cause of the
generation of animal heat, and thus the supply of carbon in the food
becomes of great  importance  to the maintenance of the proper tem-
perature of animals.
  From the natural subdivision of the food of man into two classes
—one, consisting of the  nitrogenized matters, well  adapted  by  their
constitution for the formation of blood, and the other, the non-nitro-
genized  substances, serving to supply a large amount of carbon —
Liebig proposes to name the former the  plastic elements of nutrition,
and the latter elements of respiration.
  To the first  term we see  no objection—but the use of any  term
which would imply that respiration must  be, as it were, fed directly
through the digestive process, appears to us  scarcely consistent with
the real facts of the case.  The respiratory process is partly a process
of supply, and partly one of depuration.   It  supplies oxygen, and it
assists in the removal of  effete matters in the  shape of carbonic acid.
The effete particles of the  tissues would probably supply sufficient
carbonic acid to effect the attraction of the required amount of oxygen
—but as the supply of oxygen has the ulterior object of generating a
due amount of heat, there will be required for this  purpose a larger
quantity of carbon than can be obtained merely from  the destructive
assimilation of the tissues (to use Dr. Prout's expression).   Hence,
for this  purpose, a special supply of carbonaceous  material must be
furnished to the  blood—and  this is derived  from  the  non-azotized
alimentary substances.   We prefer, then, the terms lately proposed
by Dr. R. D. Thomson, namely, calorifacient  for the  non-nitrogenized
substances, nutritive for the azotized matters.
  It  is  proper to notice  that  azotized  matters may be calorifacient,
inasmuch as they contain a  large quantity of carbon ;  and it is known
that large tribes of men  live on animal food  alone.   A large  number
of North American Indians, according to Cattlin, live almost exclu-
sively on the  flesh of the buffalo, the only non-azotized food which
they  obtain being the fat, belonging to it.
  In determining the nature of the diet  to be furnished, in  order to
preserve man  in  a healthy  state, care must be taken to provide for
the calorific as well as the nutrient function; and hence the admixture
of a certain quantity of non-azotized food is needed for the former
function. In the cold northern climates  the natives instinctively feed
on fat and oily food,  which contains  a large per centage of carbon;
while the natives of the  warm south feed on fruits, which, as Liebig
says, contain  no more than twelve per cent, of carbon.  Milk, the
food  of the young, in whom the production of heat ought to be most
active, contains, according to Dr. Thomson, two  parts of  calorifa- 
DIET.
517
cient for one of nutritive matter.   Eggs also contain nutritive matter
in a concentrated form, consisting chiefly of pure albumen, to which
a considerable quantity of calorifacient matter is added in the oleagi-
nous  yolk.   The  accumulation  of  these  substances, as  a natural
provision  for the nourishment of the young, whilst yet under the sole
guidance  of the purest instinct, or, as in the egg,  where the nutrient
matter is directly absorbed by the tissues of the embryo, affords  the
surest indication that a compound food, consisting of such  elements,
is necessary for  perfect nutrition  at this  period of life.   As age  ad-
vances, or the  generation  of animal  heat becomes less active,  the
quantity of  calorifacient food required is less,  and that of the  purely
nutrient food more.
   Experience  justifies the conclusion to which  our reasoning on
these points leads, namely, that in the temperate climates the  proper
nutrient materials for infancy and childhood are milk, saccharine and
amylaceous substances, the latter being  combined with gluten ; and
that to these must be added a certain amount of  gelatine, albumen,
and fibrine, when the growth of the child and  the more active play
of its  nervous  and  muscular systems call for a  further  supply of
nitrogenized food.   In adult life, azotized substances are needed, as
a principal portion of the diet, to supply the waste which mental and
bodily exertion  gives rise to.
   It must be confessed, however, that the views  which theory sug-
gests upon this subject are not such as would enable us with benefit,
or even  with safety, to determine the suitable diet for man.  We
learn much from instinct and more from  experience, which we could
never have gathered from a priori reasoning.   Thus the importance
of the  admixture  of vegetable with  animal food could never have
been determined without the aid of the experience afforded by the
melancholy instances of disease  generated by  the  privation  of the
former  kind of aliment.   Scurvy, as it  is  now well  known, is fre-
quently due to  the want of a proper supply of fresh vegetable  food ;
and it may be  quickly and effectually cured by supplying this want.
Again, it  cannot be  the deficiency of any of  the  staminal  principles
which gives rise to scurvy, because these exist in abundance  in the
animal food ; and scurvy, it must be remembered, will occur in the
midst of  plenty of this kind  of  food.   The  disease  is due  to  the
deficiency of some unknown material necessary to health, which the
vegetable kingdom alone can supply; and which, apparently, is most
readily obtained from citric acid, lemon or lime-juice, or vegetables
containing citric acid in good quantity, as the  potatoe.
   Nevertheless, the  results of investigations  as to the influence of
particular kinds of diet in modifying  nutrition, are strongly confirma-
tory of the  views expressed  above.  Diet may be insufficient, either
from its being given in too small quantity, or from its being defective
in some  principle, essential or incidental, necessary to the health of
the blood—that fluid, upon the healthy condition of which the proper
nourishment of the  body depends.  The effects  of a diet scanty in
quantity,  although  not objectionable in quality, are visible in the
general emaciation, the wasting of all the tissues,  and the consequent 
518
DIGESTION.
debility.   If dissolution be slow, the great non-nitrogenized material
of the body, fat, is employed to supply the animal  heat, as is strik-
ingly seen in hybernating animals.   Specific effects follow the absence
of certain elements of the food, even although the absolute quantity
of it  be  abundant.  If nitrogen be  deficient  in  quantity, or  alto-
gether absent, the  imperfect  nutrition shows  itself in the form  of
ulcerations of particular textures.  Those tissues suffer most in which
there is but little inherent activity  of nutrition, or  which are exposed
to the contact of vitiated secretions.  In Magendie's well-known ex-
periments of feeding dogs upon sugar and water, the  cornea  of the
eye ulcerated, and destruction of the organ ensued upon  the  conse-
quent evacuation of the humors.  Similar  cases now and then occur
in the human subject  from the supplies of nourishment being  inade-
quate.  Ulcers are  very apt to show themselves on the mucous mem-
brane of the alimentary canal; they will form in the mouth or in the
intestine.   These  signs  may be accompanied  with a  more  or less
scorbutic state, as  shown in spongy gums, subcutaneous ecchymoses,
&c, according to  the extent to which the blood  has suffered;  they
may occur, too, where there is abundance of fat, although wasting  of
muscles.  If the supply of non-nitrogenous food be large, fat will be
formed.  When Magendie fed  dogs exclusively  on fat, there were
ulceration of the cornea and wasting of muscle, but the tissues were
infiltrated with fat.  The case of the ill-fated Dr. Stark illustrated the
effects of the long continuance of a diet deficient in nitrogen.   This
physician, with ill-directed zeal, dieted himself for four months  chiefly
on non-azotized food, water, butter, oil, sugar, taking only bread in
small quantity, and meat or fish occasionally as azotized food.   In a
short time, well-marked scorbutic symptomsshowed themselves without
any diminution in  the  fat of his  body ; but subsequently diarrhoea,
the result of ulceration of the intestinal mucous membrane, came on,
and terminated his career.
   Of the Quantity of Food necessary for Health.—The proper quantity
of food necessary  for the  support of general  nutrition in a healthy
state  can only be  determined  by the results of observation and ex-
periment ;  and the best mode of gaining information on this point is
to consult the diet tables of various public institutions,  in which due
attention is  paid  to  the health of the inmates, or to ascertain the
allowances which are found sufficient for the army and  navy.   Each
seaman in the British  naval  service, is allowed  from 31 to  35i  ounces
of dry nutritious food daily, of which 26 ounces are vegetable and
the rest animal, the latter consisting of nine ounces  of salt meat  or
4h of fresh.   Sugar and cocoa are also given.   The soldier is allowed
a pound of bread  and three quarters of a pound  of meat.  In most
of the London hospitals, full diet, which is  given to convalescent
patients  who need a liberal diet,  consists  generally of half a pound
of meat, with from 12 to 14 ounces of bread,  half a pound of pota-
toes, a pint of milk, and sometimes beer or porter, a pint of the former
or half a pint  of the  latter.  The former dietary is destined for men
who  must  be  in  readiness  for the most active athletic  exercises, re-
quiring not only great muscular strength, but also considerable power 
DIET.
519
  of enduring fatigue.   The latter is intended to recruit the powers  of
  those who have been  suffering  from disease.   If, now, we compare
  with these a dietary which  has been found sufficient for the support
  of health  in  a  state of more  or less confinement, with a moderate
  amount of daily labour, we may fairly infer that the proper allowance
  lor persons not engaged in actual manual labour lies between  these
  extremes.   In the union workhouses of England, able-bodied men
  obtain about 25 ounces of solid food daily, of which the quantity of
  meat does  not  exceed 5 or  6 ounces.   In prisons it has been found
  necessary to give a certain amount of animal  food to prisoners who
  are subject to hard labour. Each of such prisoners, if confined for a
  term exceeding three months, and kept  at hard labour, has a  daily
  allowance  of about 36 ounces of food, of which meat constitutes only
  a very small portion, namely, about 16 ounces in the week, four ounces
  on each of four days in the week.   The prisoner has obviously the
  advantage  of  the poor man, whose only crime  is poverty.   But there
  is doubtless sufficient justification for this, in the fact that the labour of
  the prison, and the mental depression which long-continued restraint
  and confinement induce, render  a greater amount of nutriment neces-
  sary than the indigent would  require  who seek in  the workhouse  a
  shelter from absolute want.
    It is plain, then, that a  daily amount of food, varying in quantity
  between 35 and 25 ounces, is  sufficient to  maintain health; but of
  this a fourth or a fifth  ought to be animal food, especially when bodily
  exertion is  being used.   An  amount  greater than this is prejudicial
  as affording material  for  the formation  of  new compounds, which
  serve only as materies morbi that may contaminate various tissues or
  organs,  and impair their  physical  and  vital  properties.   A lesser
  quantity, on the  other  hand,  makes  a poor blood, weakens the co-
  hesive power of its elements as well as the attractive force of the tis-
  sues; and  thus, in  this latter  case, materies morbi may be generated
 from the decomposition or the imperfect composition of the elements
 of the blood, and the tissues will suffer partly from  not appropriating
 a sufficient quantity of the nutritious elements contained in the blood,
 and partly from  the inferior quality of those  elements themselves'
 which are probably also contaminated  by some  new compound.
   In proportion as our knowledge of pathology, or the intimate nature
 of disease, extends, we  become  better able to  treat disease  with ad-
 vantage on physiological principles; and  it must  be evident to all,
 who fairly consider the subject, that nothing is  more  important than
 to  determine the proper diet suitable to particular maladies.   We
 must not content ourselves merely with starving  or feeding a  diseased
 person ; but we must give him that kind of food (whether in large or
 small quantity) which his digestive organs  can most readily assimilate,
 and which will not serve as pabulum to the morbid matter which is
 apt to be generated in his system.  It  is  in diseases of the  kidneys
 and liver that the most manifest good is derived from a well  directed
 dietetic system.   In diabetes it has long been determined that a  diet
of animal food, with abstinence from sugar, and substances, such as
starch, capable of being converted into sugar, is productive of excel- 
520
DIGESTION.
lent results.  In diseases of the  liver, more is to be gained by close
attention to the quantity of the food than to the quality; at the same
time that it must be borne in mind that  a  nitrogenized diet  is more
suitable than one abounding in carbon, which would throw upon that
organ a work of elimination greater than it may be able to bear.   In
the rheumatic and gouty diatheses attention to diet is the  main re-
source to counteract the tendency to generate the morbid agents which
severally produce those states of constitution.
  When there is a tendency to the accumulation of fat, a nitrogenized
diet in regulated quantity is the most suitable  to obviate it.  When
more carbon  enters the system than is  required for the calorifacient
and respiratory functions, or for the nourishment of tissues, it will ac-
cumulate as fat: and it is only to be removed  by the free  admission
of oxygen to consume it, care being taken at the same time not to
favour further accumulation by the supply of too much food, especially
of the non-azotized kind.   The practice of trainers furnishes a useful
commentary on this point, and may be  imitated by many who suffer
from dyspepsia.  The following account  of the system pursued  in
training was  communicated to Sir John Sinclair by Mr. Jackson:—
  " The diet is simple—animal food alone ; and it is  recommended
to take very little salt and some vinegar with the food, which prevents
thirst, and  is  good  to promote leanness.  Vegetables are n.ever given,
as turnips, carrots, and potatoes; but bread is allowed, only it must
be stale.  They breakfast upon meat about eight o'clock, and dine at
two.   Suppers are not recommended, but they may take a biscuit and
a little cold meat  about  eight o'clock,  two hours before they go to
bed.  It is reckoned much against a man's wind to go to bed with a
full stomach, and  they in  general take  a walk after supper.   Some
people will have tea; but it is not recommended, nor is it strengthen-
ing, and no liquor  is  given  warm.  Full  and substantial  meals  are
given at breakfast and dinner ; beef and mutton are best.  It is con-
tended that there is more nourishment in the  lean of  meat than the
fat, which is fully proved by experiment, fat, being of a greasy nature,
causes bile, and palls the stomach: the lean of fat meat  is best. Veal
and lamb are never given,  nor  is pork.   The legs of fowls, being
sinewy, are much approved  of.  The yolk of a raw egg is reckoned
the best thing in a  morning, and is supposed to prevent bilious com-
plaints.  Beefsteaks are reckoned very  good,  and  rather underdone
than otherwise, as  all  meat in general is; and it is better to have the
meat broiled  than roasted or boiled, by which nutriment is lost.   No
fish whatever is allowed,  because it is reckoned watery, and not to
be compared  with  meat in  point of nutriment.   The fat of  meat is
never given, but the lean of the best meat.   No butter nor cheese on
any account; cheese is indigestible.   Meat must be dressed as plain
as possible without seasoning of any kind.  Men will live longer on
beef, without change,  than  on any other kind of animal food, but
mutton is reckoned most easily digested.  The meat must always be
fresh, and  never salted.   No quantity of  meat is fixed;  it depends
upon the constitution and appetite.  Little  men will eat as  much as
large men, and  very frequently more.  Pies and puddings are never 
HUNGER.
521
given, nor any kind of pastry;  as to hard  dumplings, people may as
well take earthenware into their stomachs."
  This  system, it must  be  remembered,  is  combined  with one of
active and even severe exercise.
  The periods  for  taking food, and the  quantity to be  taken, are
under the natural guidance of certain sensations, which we call Hun-
ger, Thirst,  and Satiety.
  Hunger.—The immediate cause of hunger cannot be explained.
It is probably a sensation dependent on a peculiar condition of the
mucous membrane  of the stomach, which certain states  of disease
may blunt or may increase to an inconvenient extent, as in diabetes.
The nerve which is instrumental  in this sensation  is  probably the
vagus nerve by its gastric branches, but there is no reason for deny-
ing to the sympathetic nerves, distributed to the stomach, some share
in  this  phenomenon.  The  experiments of  Brachet and Dr. John
Reid, relative to  the influence of the nerves on hunger, lead  to no
satisfactory  conclusion, because of the difficulty of  interpreting the
sensations of dumb animals, and the probability that  appetite would
be  destroyed or impaired after any serious  operation, even although
the injured  nerve had  nothing to do with the stomach.  The sensa-
tions caused by  extreme hunger  would indicate that  some further
change  was taking place in the  wall of  the stomach.  A peculiar
sense of sinking referable  to  the  gastric  region, general  faintness,
secretion of gas into the  stomach, and sometimes actual  pain, accom-
pany this state.
   When these  sensations are not relieved  by their appropriate stimu-
lus, food, the effects of fasting begin to show  themselves.  The body
now feeds upon  itself—in  other words, the process of destructive
assimilation is  the only source from whence the blood  derives its
materials of supply.   All the  tissues show  the  effects of impaired
nutrition in the  deficient manifestation of their vital  powers—the
animal  loses weight, and,  according  to Chossat, this loss is most
rapid the few days  immediately preceding  death.  The tissue which
wastes  most is fat,  and those which lose least are the osseous tissue
and the nervous.   There is also great loss  of heat; Chossat states
that the daily fall was half  a degree  of Fahrenheit;  but on the last
day it fell much more rapidly, reducing the temperature to 77°.  The
stomach is much contracted, and its mucous membrane thrown into
thick folds or ruga3.  The gall bladder is generally full  to distention,
the intestines  are contracted like  the stomach;  according to Collard
de Martigny, the lymphatics become  full in the first  ten days of fast-
ing, but afterwards their contents decrease considerably.  The respi-
ratory movements become  slow, and the pulse falls considerably in
frequency.  The urine becomes scanty, and all the  parenchymatous
oro-ans  are remarkable for their paleness. Furious delirium frequently
manifests itself, when  the loss of strength becomes considerable.  A
similar delirium sometimes  ensues where too rigid an abstinence has
been observed in the treatment of  disease.
   The period at which death occurs from protracted  abstinence
varies  greatly; young animals die  sooner than old ones.   Dogs live
     34 
522
DIGESTION.
from  twenty-five to thirty-six days.   In man, total privation is not
borne above a week.   By the  aid of a little drink, given  now and
then, life may be prolonged considerably, and instances are  recorded
where it continued for eighteen or nineteen  days, or even for thirty
days.   Dr. Willan sawr a gentleman who voluntarily abstained  from
everything but water,  flavored  with orange juice, for sixty days, and
then  died.   Medical men, however, should  exercise much  circum-
spection in cases of professed abstinence, numerous impostures hav-
ing been practised on  this subject.
   Thirst results from a peculiar state of the mucous membrane of the
digestive tube, but more especially of the mucous membrane of the
mouth and fauces, caused by the imperfect supply of liquid.   A sense
of clamminess in the  mouth, pharynx,  and even  down the oesopha-
gus, accompanies extreme thirst.   The thirst in  fevers is  probably
due to the  state of the blood  and the consequent change in the secre-
tions.  Injecting thin  fluids, as  water, into the  blood, relieves the
thirst of poisoned animals, as  found by Dupuytren and  Orfila.   In-
jecting liquids into the  stomach  relieves thirst,  as was  found  in  a
case  where the oesophagus had been wounded.

  On the subjects of this chapter the reader may be  referred to Dr. Prom's papers
and works—Dr. Paris on Diet—Dr. Pereira's work on the same subject—Dr. Stark's
works—Dr. Latham's account of the disease prevalent at  the Penitentiary, 1825—
Dr. Budd's lectures on diseases produced by insufficient nourishment, Med. Gazette
—Sir  John  Sinclair's Code of Health, in which many interesting;  tracts relating to
diet and regimen have been preserved—Tiedemann, Physiologie, Band, iii.—Liebig's
Animal Chemistry—Dr. K. D. Thomson on Food.
                         CHAPTER  XXIII.

OF DIGESTION.--PREPARATORY PROCESSES ;  VIZ. PREHENSION, MASTICA-
  TION, INSALIVATION, DEGLUTITION :  THE ANATOMY OF THE  ORGANS
  CONCERNED IN THESE PROCESSES.*

  In the present chapter we shall consider the preliminary stages in
the function of digestion, under which head may be included all those
which precede the entrance of the food into the stomach.

  *  In entering on a consideration of the alimentary processes, a few words may be
conveniently introduced regarding the general anatomy of the mucous system, a term
under which we include the skin, mucous membranes, and true glands, all of which
are  continuous with one another, and composed essentially of similar parts.  The
skin and the glands pertaining to it,  as well as several parts of the mucous mem-
branes, have been already minutely described in treating of the organs of sense. It
only remains, therefore, to speak of the great internal mucous tracts, with their asso-
ciated glands.
  The alimentary mucous membrane commences at the lips, and lines the passages
traversed by the food from  the mouth  to the anus.   The principal glands whose ducts
open upon it, are the mucous and salivary glands, the pancreas, and the liver. Be-
sides these, its thickness is made up, in  the stomach and small intestines, of an inli- 
OF  PREHENSION.—THE LIPS.
523
    Of Prehension, or the taking of food  into the mouth, little needs be
  said.   It is performed chiefly by the hand, that wonderful  instrument
  of man's lower instincts as well  as  of his higher attributes.   The  lips
  and cheeks, as well  as the  anterior teeth, and the  tongue, are also
  concerned  in this function.
    The lips  are endowed with great sensibility, derived  from the  su-
  perior and  inferior maxillary divisions of the fifth pair of nerves,  and
  are  covered with largely developed papillae of touch, which receive

  nite series of  tubular offsets, vertically arranged, pouring their contents on  its  free
  surface, and forming an involuted or compound membrane, or a diffused or membranous
  gland.  The  respiratory mucous  membrane  begins at the nostrils, sends processes to
  the olfactory, the optic, and the auditory organs, and lines the air-passages  to their
  terminations;  numerous mucous glands occur in this tract.  Lastly, the genito-uri-
  nary mucous membrane commences at  the genito-urinary orifices, lines  the excretory
  passages pertaining to both functions, and  is the essential constituent of the glands
  of both.  In the female, however, there is an exception in the case of the ovaries, as
  will be explained in a subsequent page.
   Penetrating into all the recesses of the mucous system, and forming its chiefbulk,
  we find nucleated particles, arranged as  a layer, and developed in succession,  in such
  a manner  that the old ones disappear, while others advance from below.  An epithe-
  lium is not peculiar to the mucous system, but is met with also on serous membranes,
  and on the walls of the blood and lymphatic vessels, as well  as elsewhere; but  ii is
  distinguished  here by its  external  position as regards other textures, so as to be ca-
 pable of passing from the body, or to be exposed to the contact of foreign substances.
 The particles  of this epithelium are very different in different parts, and may be di-
 vided into  scaly, columnar, glandular, and ciliated.   The scaly variety is seen on the
  skin, and in the alimentary tract as low as  the  stomach, as well as in the excretory
 parts of the genito-urinary tract. (See vol. i. pp. 404, 412, 437, &c.)  The columnar
 variety consists of rod-like  particles, placed endwise, generally bulged near the cen-
 tre by the nucleus, and narrowest at the point of attachment.  They are met  with in
 the air-passages, on  the intestinal villi, in the bile-ducts, and elsewhere.  The glandu-
 lar variety is bulky, its particles  rather  globular  than flat or long, and found in all the
 glands, the several secretions being essentially the contents or substance of the  par-
 ticles  set free.   The ciliated particles  are  columnar or sub-globular  in shape, but
 clothed on their free margin with cilia, as in the examples formerly figured, (vol. i,
 p. 62, and ante, p. 4.) They are  found chiefly in the respiratory tract, and in parts of
 the genital tract of the female.  The true scaly and glandular varieties of epithelium
 are never ciliated.  See Cyclop.  Anat.,  art. Mucous Membrane.
   The epithelium rests for the most part on  a layer of membrane, hence termed base-
 ment membrane, which, in the best-marked examples, is distinctly homogeneous  and
 transparent, but in some situations is  finely fibrous, and not easily separable from
 the areolar and other tissues which lie below it.   These two,  the epithelium and  the
 basement membrane, may be regarded as the constituents of a simple mucous mem-
 brane, although the latter cannot be everywhere traced, for example, in the interior of
 the hepatic lobules. The office of the  basement membrane seems to be in all cases
 to sustain  the  epithelium, and to shut in or cover over those tissues which may be
 regarded as internal to the elements of  the simple  mucous membrane.  Professor
 Goodsir considers that  the  basement membrane is covered with points, which he
 terms centres of nutrition, from which the development of the  particles of epithelium
 proceeds; but  we cannot  accede to this view; first, because the best examples of
 basement membrane display no such points  ; and, secondly, because such a  suppo-
 sition does  nothing to explain the successive growth of the particles.
  The tissues  which lie under the simple mucous membrane, as now sketched out,
 are areolar tissue, blood, and lymphatic  vessels, and nerves, and in some situations a
 peculiar papillary tissue.   These,  in their  several  forms  and proportions, greatly
 modify the  characters of the membrane, as it is presented to the naked eye, and con-
 tribute largely  to our common notions of the structure of the skin, mucous  mem-
 branes, and glands.  The  areolar  tissue forms  the cutis vera of the skin, (vol. i. p.
406.) and the corresponding part  of the  great mucous tracts;  while in  glands it  is
generally in much smaller quantity.  The blood-vessels and other textures are modi-
fied in various ways, as will be hereafter noticed in  detail. 
524
DIGESTION.
an abundant supply of blood from the coronary arteries.   Along their
margin  the skin becomes continuous with the mucous membrane of
the digestive  apparatus, which, within these parts, as well as over
the rest of the mouth, the pharynx  and oesophagus, as far as the sto-
mach, has an  epithelium of the scaly variety ; this  variety forming
the most essential  character of that subdivision of the digestive appa-
ratus  considered in this chapter.   The lips are moved  by about twenty
muscles, and  are  capable of grasping and retaining the food placed
within  them,  and  of aiding  in the subsequent motions  which it is
made to undergo  in  the mouth.   Their employment in articulation
will be  spoken of in another place.
  The lips and the tongue undergo a variety of modifications in the animal series,
with reference to the function of prehension; among these may be enumerated the
enlarged, pendulous, and very movable  lips of the ruminants and solipeds, and of
some monkeys.   Man uses his lips in suction, as do the young of all mammalia, at
the breast.  Among fishes, the cyclostomatous group (as the lamprey) have a suc-
tion power of a similar kind, their circular mouth being surrounded and supported
by a ring of cartilage, and furnished with appropriate muscles for producing adhe-
sion to surfaces to which it is applied.  In birds, the lips are modified so as to form
the bill, which is  always the prehensile organ in that class.

   The tongue is used by man and  animals in  suction, somewhat  as a
piston,  being  drawn within the  mouth  so as to exhaust the anterior
part of  that cavity, and allow fluids to enter by the atmospheric pres-
sure.    The canine and feline races employ the tongue to lap fluids;
the giraffe twines this organ around the leaves and branches of trees,
and detaches  them with force.   The ant-eaters have  a remarkably
long  tongue,  covered with a slimy secretion ;  this they protrude, and
upon it entrap their victims.  The cameleon among reptiles, and the
woodpecker among birds, have each a tongue  enormously developed
for the  purposes of prehension : to these many other striking exam-
ples might be added.
   The  cavity of the  mouth, in  which  mastication is conducted, is
bounded, first, by the palate or roof of the mouth, a  fixed and hard
surface formed  by parts of the  upper  maxillary  and palate  bones,
supporting a  dense fibrous structure, lined with closely adherent mu-
cous  membrane, and fitted to act as a resisting surface against which
the tongue may press  the food ;  and, secondly, by the  cheeks, lips,
and  tongue,   which,  in  reference to  the present function, may be
classed together  as  tactile  and muscular organs, designed to  handle
the food while subjected within the mouth to the  action of the teeth,
and then to forward it into the pharynx.   Projecting into the mouth,
above  and below, is an arched series of teeth, or grinding organs,
firmly fixed by roots into the alveoli of the upper and lower maxillary
bones.   Those  of the upper jaw are immovable, or only movable
with  the entire head ;  but those of the lower jaw  are capable of up-
ward, downward, backward, forward, and lateral motions, by means
of  the  muscles of mastication acting  on the  bone in which they are
implanted.  By these  motions of the lower teeth upon the upper, the
food  is  comminuted.    A more detailed description of some of the
organs  of mastication may now be given.
   The  cheeks form the  outer wall of that part of the  mouth which 
THE TONGUE.—THE TEETH.
525
lies outside the teeth.  Like the lips with which they are continuous,
they consist of a muscular stratum interposed between the  skin and
the mucous membrane of the mouth.   They admit of distention and
compression, and form pouches which receive portions of food escap-
ing outside the teeth during mastication, and from which it is continu-
ally returned  towards the inner cavity, to be submitted to the grinding
action.  This use of the cheek is well exemplified in cases of paralysis
of the buccinator muscle, in which the food  collects in the flaccid bag
to which this part is then reduced.
   The tongue is an  important agent of mastication, and  has been al-
ready spoken of as the seat of taste and of an exquisite sense of touch.
By virtue of the latter it receives accurate impressions of the tangible
qualities of the food, and of its situation in the  mouth ; and by its
great mobility it is constituted the main instrument by which the food
is moved within the mouth, so as to be effectually brought within the
range of the  masticating organs.  The tongue rests  upon the hyoid
arch, to which, and to the concavity of the lower jaw, it is fixed by4
the muscles.   It lies within the curve of the teeth, and is covered on
its free surface with  mucous  membrane, which has been before de-
scribed.  The muscular fibres which compose this organ intersect one
another in an intricate manner in its interior, but they all  appear  to
arrive ultimately at  its dorsal  surface,  and  to  be  there implanted, in
small sets or  bundles^into the  submucous  stratum of dense  areolar
tissue, a good  deal of fat being disseminated throughout, but espe-
cially in the intervals between the muscular  bundles at their insertion.
We refer to works  on descriptive anatomy  for the anatomy of these
muscles.  By their  action the  upper surface of  the  tongue may be
made convex or hollow, or may be  pressed forcibly  against  the roof
of the mouth ;  the tip of the  organ  may be protruded or  moved  in
any direction, and to any recess within the  cavity where food might
lodge, and the  whole organ may be lowered or drawn back.  These
several actions are so performed as  to exemplify, in  the  most perfect
manner, the concert which has  been already mentioned  to occur be-
tween many muscular and sensitive parts.
   Of the Teeth.—These, in the widest acceptation of the term, and
in reference to the whole animal  scale, are hard  organs situated on
the  inner surface of the digestive  tube, fitted for comminuting the
food previous to its  being acted on by the gastric juice. In the higher
classes they are of  an osseous nature  and  fixed to bone, though not
originally.   Among the invertebrata, the  echini  are  remarkable for
their calcareous oral teeth, five in number.   The mouth of the leech
is armed with  three  serrated teeth, worked  by muscles, which saw
their way into the skin.  In some insects the  gizzard is armed with
a very  complicated system of  horny teeth.  In  the  stomach of the
Crustacea is a cartilaginous framework, with projecting teeth, moved
by muscles, and capable of very powerful masticatory actions.  Among
the gasteropods, the bullae have three stomach teeth ; and  others, as
the Aplysia,  a great multitude,  of large size and of different forms.
   True  osseous teeth are found only in three classes of vertebrata,
viz., mammalia, reptiles, and  fishes.  Some of these, however, are 
526
DIGESTION.
without them,  as, among  mammalia, the American ant-eater, the
manis, the echidna, the proper whales ; among reptiles, the tortoises;
and  the sturgeon  among fishes.   The teeth of  fishes  are  fixed not
merely to the maxillary bones, but also to the palate and other bones,
bounding the mouth and throat, and they are often  extremely nume-
rous. The bills of tortoises and birds perform some of the functions of
teeth ; but in those of the latter class which  live on hard  vegetable
substances, the muscular gizzard, with  its hard cuticle, and by the
help of small angular stones which the instinct of the animals teaches
them to swallow with the food, performs the functions of a masticatory
apparatus.   Among the mammalia, the teeth are few in  number, and
limited to a single row in each jaw.
   Teeth may be classed  according to their shape and  the function
they have to perform.  Thus, the  following varieties may  be briefly
enumerated :—The cutting or gnawing teeth of the rabbit or beaver,
—the front teeth of man.  The conical teeth of fishes for seizing and
retaining prey—the canine  teeth  of the  lion and dog.   The hinder
teeth of the carnivora, with several sharp elevations for tearing.  The
more complex crushing  teeth of the insectivora,  and of the frugivor-
ous  monkeys.  Lastly,  the  true grinding teeth  of granivorous and
graminivorous animals.
   Of the Human  Teeth.—The teeth in the adult human subject are
thirty-two in  number, of which four  are  incisors, two  canines, four
bicuspids, and  six large molars, in each jaw.   Those of the upper
jaw  form the  larger arch, so as to overlap those  of the lower jaw in
front, and to overhang them somewhat at the sides, when the mouth
is closed.  Each tooth has a crown or body, projecting above the gum,
and aroot, buried in  the alveolus or socket; and the division between
these is marked on the surface by a somewhat constricted line, termed
the neck. Each tooth has also an internal cavity, containing a vascular
and  nervous pulp, and which is open only towards the root. Lastly,
each tooth consists mainly of a peculiar modification of osseous struc-
ture, termed dentine, or ivory, which is  coated over with calcareous
enamel on the crown, and with a thin  layer of true bone on the  root.
The  position and  shape of the several varieties  of the  human teeth
are as follows : —
   1. The incisors, or cutting teeth, are situated in front, (those of the
upper jaw being the  larger,) and present a single conical root of large
size, and a vertical crown,  bevelled behind  so  as to terminate  in a
sharp horizontal edge.   These teeth are fitted for cutting  the food.
In herbivorous animals  they crop  the herbage, in rodents they are
capable of gnawing even very hard  substances.
   2. The canine teeth come  next to, and  are larger than, the incisors,
especially the root, which sinks deeply into the jaw, and renders the
alveolar arch prominent by  its  size.  This root is conical, and the
crown more conical and less wedge-shaped than  that of the incisors,
being usually surmounted  with a  small pointed tubercle  or  cusp,
whence they are termed cuspidate.  In consequence of the small size
of the lower incisors, the lower canines are nearer together than the
upper, and fall  within them  when the mouth is closed.    These  teeth 
THE TEETH.
527
 in the canine, feline, and other carnivorous tribes, are largely deve-
 loped, and more decidedly formed for lacerating and tearing the flesh
 of prey.                                               &
    3. The bicuspids, ox false molars, are not so large as the canines,
 which they succeed, but their crown  presents  two pyramidal emi-
 nences, as their name  implies, and there is a tendency in  their  root
 to be double; this  part being marked  by a vertical  groove, and its
 apex, sometimes bifid, Leing perforated by two apertures  leading to
 the interior.                                                 D
    4. The true molars, or multicuspidate teeth, are placed most pos-
 teriorly, and  are  distinguished by their great size, the square form
 of their crown, surmounted by three, four, or five  cusps,  a  distinct
 neck, and  by their  shorter, but more  divided root, which presents
 from two  to  five  branches, the inner the  more divergent,  and each
 perforated  at its  apex.   The  hindermost of these  are the  wisdom
 teeth.    The  false,  and  especially the  true,  molars  are  admirably
 adapted for grinding and pounding the food, under the influence of
 those powerful muscles by which  the lower jaw is moved in a lateral
 direction while being forced against the upper.  Though the least
 simple of the human  teeth, these grinders are greatly surpassed in
 complexity of form and structure by the corresponding teeth of herbi-
 vorous animals, such as the ox, the horse,  and the elephant.
   "The internal structure of the  teeth, like  that of bone,  has been
 much illustrated by those modern microscopic investigations, which
 have introduced a  new era in the sciences  of anatomy and physi-
 ology. The researches on this subject, opened by Purkinje, Fraenkel,
 and Retzius,  and  subsequently pursued with more or less originality
 and extent  by Muller, Schwann, Tomes, Nasmytb, and especially by
 Professor Owen, have confirmed the  almost forgotten discoveries of
 Leeuwenhoek, and brought the whole subject of dental structure and
 development  into  clear and consistent  light.   We shall now give a
 short summary of the facts as they have appeared to  our own  minds,
 and refer, once for all, to the works quoted at the end  of the present
 chapter,  for information, as  to the  share each inquirer has had in the
 general and very satisfactory result.
   The three  constituent substances,  dentine  or  ivory, enamel, and
 tooth-bone  or crusta petrosa, are  found in  all the higher and more
 perfect forms  of teeth;  and their several conditions in the  range of
 animals  have been  greatly  instrumental in  leading  to  our present
 knowledge of them in  the  human teeth: our design,  however, will
 allow us to speak of their character in the latter  only, except in  the
 way of illustration.
   Taking a simple tooth  as an example, (fig.  149,) we find the great
 bulk to consist of  dentine, a term  used  by Mr. Owen to distinguish
 this  substance from  the rest, in preference  to that of ivory or tooth-
 substance.   The dentine gives  the general form, size, and  hardness
to  the tooth, both root and crown, and in its central part is the cavity
containing the papillary substance  or pulp, supplying the vessels and
nerves of the  organ.
  Dentine  is  manifestly a modification  of the-osseous tissue.   Like 
528
DIGESTION.
Fig. 149.
 bone, it  may  be seen  in favorable specimens  to present a finely
 granulated  ultimate  texture, and,  like bone,  it is perforated  by a
 series of minute  channels, opening on the one  hand on  a vascular
 surface, (that of the pulp-cavity, which corresponds with the Haver-
 sian  surface of bone: p. 110,) and on  the other  sparingly branch-
 ing, so as to permeate every portion of the tissue.   The peculiarity
 of  dentine  consists chiefly in  these internal  channels of nutrition;
 and,  as we have before  shown the Haversian  canals and systems
 of  lamellae  in  bone to be arranged in constant subservience to  me-
 chanical ends, so the  corresponding parts  in dentine, and  especially
                        those parts which answer to the lacunae and
                        canaliculi  of  bone, appear to derive  their
                        peculiar characters from the mechanical exi-
                        gences of the  case.   The tooth  having to
                        sustain rude pressure on its  crown, chiefly
                        in a  vertical direction, great density  and
                        compactness are  requisite  in its main  con-
                        stituent, and  its  internal  vascular  surface,
                        which is small in proportion to the mass of
                        dentine, is centrally placed, and receives its
                        vessels and nerves at the deepest point,  most
                        remote from injury.   As  the vascular  sur-
                        face is small, and therefore at a  great  dis-
                        tance from a large proportion of the tissue,
                        the interstitial channels of the dentine are
                        capacious, especially  towards the vascular
                        surface,  and comparatively direct in their
                        course from it; and, instead of commencing
                        minute as the canaliculi  of  bone do,  and
                        dilating  at  intervals,  after a  tortuous  and
                        irregular route,  into hollow chambers,  like
                        the lacunae of that texture, they are widest
                        at their commencement  in the pulp-cavity,
                        retain  throughout  the simple tubular  cha-
                        racter, and  are provided, for  the  most part,
                        with proper walls, so  that each tubule may
                        be regarded as a hollow  rod, the  stem of
 which is of a harder and  compacter nature  than the intertubular
 substance through which it runs.
  The direction taken by  the tubes is further interesting; for not only
 do  they radiate on  all sides from the vascular surface, as  being the
 conduits of  nutrition to the dentine, but they thus confer on  every  part
 of the tooth a greater  power of  resistance in an  inward direction  from
the surface  towards the centre,  a power increased by the  cylindrical
 shape of the pulp-cavity, and its tendency to an arched figure towards
the crown.   But  it would appear that the beauty of the mechanical
contrivance  does  not  stop even here, for it has been observed  that
the tubes in many parts are doubly waved, like the Italic/, and  that
 within these primary curves are comprised  very numerous  secondary
meanderings ; from which, as those of contiguous tubes have a lateral
 Vertical section of human in-
cisor, showing the general ar-
rangement  of its constituent
parts.  The dentine and pulp-
cavity, the enamel on the crown,
and the bone on the fang, are
seen.  a. Neck  of the  toolh.
Magnified 3 diameters. 
DENTINE.
529
correspondence, a certain elasticity, and a greater capacity of resisting
external force, must accrue.  The tubuli of the dentine now described,
branch a few times dichotomously, and the branches  retain for some
distance the diameter of the trunk, this multiplication of their num-
ber enabling them to occupy the spaces which would be left by the
radiation of unbranched tubes from a common centre.   The tubuli are
in some parts  about their own width asunder, in others they run in
                               Fig. 150.
 Sections of a human incisor, showing:—
 a.. Junction of dentine and enamel near the neck of the tooth, a. Tubes of the dentine, dividing
and ending on 6 b, the cupped surface on which the enamel rods vertically rest.  c. Free surface
of the enamel. The enamel rods are crossed by transverse lines and also by oblique dark lines.
 b. Bifurcation of the tubuli of the dentine, soon after their commencement on d', the surface of the
pulp cavity.
 c. Branching of the  tubuli of the fang, and their termination in the small irregular lacunae of the
"granular layer."
 In these longitudinal views of the tubuli, their cavities only, and not their walls, are visible.
 Magnified 300 diameters.

mutual contact; and their compact  proper wall is  about as  thick as
their cavity is  wide.   Except near the  pulp-cavity, they are, as it
were, hairy with filamentary canaliculi, which  diverge  on all sides,
and  form innumerable junctions with one another;  so that  the tubuli,
throughout  most of the  dentine, may be said  to  communicate with
each other independently of the pulp-cavity, into which they all open.
Towards  the outer surface of  the dentine, where it isincrusted on  the
crown with enamel and on the  root  with bone, the tubuli gradually
taper, and finally terminate in diminutive canals, which open, some into
small, irregular lacunae  (forming a layer on the root, termed by Mr.
Tomes the granular  layer), some into the lacunae of the osseous  in-
vestment of the fang, and others upon the surface on which  the ena-
mel  rests.   Occasionally the  tubuli are dilated  into true lacunae, or
form free arches of communication.
   The following facts illustrate the foregoing account of the structure
of dentine.  The granularity of the ultimate tissue may be best seen 
530
DIGESTION.
in specimens in course of development.   On the surface of the pulp-
cavity the orifices of the tubuli can  be seen;  and in transverse  sec-
                         tions of the  tubuli,* (fig. 151,) their proper
                         walls, the  width of their walls and  calibre,
                         and their distance apart, are all discernible.
                         In broken  fragments, especially if torn after
                         the tooth has been softened in acid, the tu-
                         bili  may be observed to stand out from the
                         surface, being broken off at different lengths,
                         as if their structure was distinct from  the
                         intertubular  tissue.   Their  hollowness is
                         proved  by the chasing of  bubbles along
                         them,  visible  under the microscope when
                         turpentine is added to  a  dry section, and
                         also by the  gas which may be  seen to be
                         disengaged  in  bubbles, chiefly  from their
                         interior, when  a section is similarly treated
                         with acid.   The latter experiment seems
                         also to show that the parietes of the tubuli
                         contain a  denser deposit of earthy matter,
                         and are consequently  harder and more re-
                         sisting than the  intertubular tissue.  We
                         do  not regard the tubuli  as filled up by
                         solid  contents,  but  as possessing a truly
                         hollow  bore, designed  to give  passage to
                         fluids.
   The enamel, investing the crown of the tooth, and forming that part
 which is exposed in the mouth to the contact of external substances,
 is harder and compacter than the dentine, and  of peculiar structure,
 although formed, as will be afterwards shown,  on the same general
 plan as the other portions of organized  bodies.  As its earthy con-
 stituents are in much larger proportion than in  the dentine, (for they
 make up 98 instead of 72 out of 100 parts, according to Berzelius,)
 the enamel  requires  much less  nutrient  change, and its  interstitial
 passages are very minute.
   The enamel (fig. 150, a, and fig. 152) consists of  a congeries of
 hexagonal rods, placed endwise  side  by side, so  as  to form a layer,
 of which the surfaces are formed by the ends of the rods, and the
 thickness is determined  by their length.   The deep surface  rests on
 the dentine, which presents a number of minute  depressions for the
 reception of the  deep ends of the vertical rods, a number of which
 rest in each ; and the superficial surface, though said to be at  first
 coated with a thin film of osseous tissue, is afterwards rendered bare
 by the earliest movements of attrition in masticating the food, and
 then  becomes the free surface of the  crown of  the  tooth.   The rods
 of enamel are about ? g^th of  an inch  in diameter, and they pursue
 a  more or less meandering course, which must augment their power

   * Mr. Topping, of York  Place, New  Road,  mounts these and  other objects very
 skilfully.
Fig. 151.
 Transverse sections of tubules
of dentine, showing their cavities,
walls, and the intertubular tissue.
 a. Ordinary distance apart.
 b. More crowded.
 c. Another view.
Human molar.—Magn. 400 diam. 
THE ALVEOLI.
531
Fig. 152.
 a. Vertical section of the enamel, showing  the
fibres, with their cross lines.
 b. Fibres of the enamel, seen endwise.
 Magnified 350 diameters. From Retzius.
 of resisting external force.  It is evident that their vertical position
 admirably adapts  them to sustain pressure, and withstand the effects
 of force directed upon the surface of the  tooth ; while, at the same
 time, the interstices or chinks  intervening between them, principally
 at  their angles of juxtaposition, are arranged  in  the  most suitable
 manner for permeation by the  fluids  derived from the subjacent den-
                                     tinal  tubuli.   These  tubuli,
                                     indeed, may be  seen to com-
                                     municate directly with the  in-
                                     terstitial passages  of the ena-
                                     mel.   The  enamel rods  are
                                     further marked, at pretty close
                                     and regular intervals, by cross
                                     lines, which, however, are  far
                                     from constant,  and of doubtful
                                     nature :  some suppose  them
                                     explained  by  the process  of
                                     development.    The  enamel
                                     rods are connected together by
                                     some  remnant  of the original
                                     organic matrix in which their
                                     earthy portion was at  first de-
                                     posited,  and which  is  repre-
 sented by the  dark lines or chinks which appear to  bound and isolate
 the rods.  As the rods are  placed  vertically on the surface  of the
 dentine*, which is not an even one, they are not everywhere parallel,
 or of equal length, but are truncated where they abut against each
 other over a hollow, and  in such parts are most liable to decay.  In
 many parts, however, near the dentine their vertical position  seems
 disordered; they are curiously contorted, and neighboring series of
 them are variously inclined, so as to  lean against one another, while
 the same rods nearer the surface  assume  an upright and parallel
 course.   The  enamel on a vertical section further shows dark  mark-
 ings running  obliquely across  the  fibres  (fig. 150, a),  and not well
 understood, and also larger cracksor fissures (fig. 149), often branched,
 running through a part or the whole of its thickness.   As Mr.  Owen
 has pointed out, the enamel is the least constant of the dental tissues,
 being absent in many fishes, in existing ophidian reptiles, and  in the
 edentate and many cetacean mammalia.
   The tooth-bone or  cement is disposed as a permanent thin layer of
 osseous  tissue  on the roots of the  teeth, and it also invests the enamel
 with a delicate film on the first  emergence of the  tooth from the gum.
 On the root it  is thickest towards the  apex, and  often lines the pulp-
cavity of the  dentine for7a little way in.  It contains sparingly the
lacunae  and canaliculi which  characterize  bone; and,  when  thick
enough, it  presents also the lamellae of that structure.  In general it
is  in  too small a quantity to require special Haversian canals; but
Mr. Tomes has shown, that, between  the roots of the  larger human
teeth, the tooth-bone is often in sufficient mass to be penetrated by a
true canal of that nature ;  and, in the teeth of many animals, the ce- 
532
DIGESTION.
ment  is as vascular as ordinary bone.   The canaliculi of the  tooth-
bone are, for the most part, directed from the lacunae towards the sur-
face, where the vessels  are  spread out, but a few communicate with
the peripheral branches of the tubuli of the dentine.   It  is through
this osseous investment of the roots that the teeth adhere so firmly to
the sockets in which they are implanted.
   The cavity of the teeth, containing the pulp, is in the fully formed
tooth the analogue of the Haversian canal of bone, by which the or-
gans of nutrition and sensation find access to the internal surface.
The blood-vessels of the pulp are branches of  the internal maxillary,
and the nerves of the fifth pair, and they are both extremely abundant,
in proportion to the extent of surface with which they  are in relation.
The capacious capillaries form numerous arches, and the nerves like-
wise end in loops, (p. 204,) which are best seen in the young tooth.
The white  substance of the nerve-fibres has seemed to us to be often
diminished or lost towards the convexity of the loops.
   The alveoli, or sockets in which the teeth  are set, are cavilies in
the border of the jaws, corresponding  in  shape and  direction to the
roots of the teeth, formed on the outer and the inner side by a firm,
compact plate of  bone,  which bounds  the  alveolar arch in front and
behind, and separated from  one another by septa of less compact ma-
terial.   The surface of these cavities is spongy, being perforated by
minute  vessels, which pass across to the surface of the roots of the
teeth, and which  there form a plexus in the substance  of a firm elastic
tissue, which is the  connecting  medium between  the socket and the
root, and is usually regarded as a periosteum.  Thus the surface of
the root is  supplied with blood, and the tooth is united to the jaw in
a way which allows it to yield very slightly under  pressure.
   The alveolar arch  is covered on the outside by the  gums, a dense,
elastic,  peculiar tissue, adapted to  sustain without  injury the forcible
contact  of the hard portions of food, to which its vicinity to the grind-
ing organs must expose it.
   The  development of  the teeth may  be described under two heads;
first, that of the elementary tissues of the tooth, the dentine, the ena-
mel, and  the true bone ; secondly, that of the dental  series, which
will include the order of appearance of the teeth of the temporary and
permanent sets.
   According to the most  recent investigations of  Arnold and Good-
sir, the  teeth are  developments from the mucous membrane covering
the dental arches, and not from the maxillary bones.  They, there-
fore, would seem  to correspond with the tegumentary appendages of
animals, such as horns,  nails, feathers, and not to be a portion of the
true osseous system,  or  endo-skeleton of the vertebrata.  The bills of
birds  are an obvious intermediate condition of the integument of the
jaws.
   The  teeth may be regarded  as  formed  in  the  following manner.
The first indication observed (according to the excellent observations
of Mr.  Goodsir, which  we have, in most particulars, had an  oppor-
tunity of verifying) is a  groove  at the border of the palate  in the
situation of the  future  teeth, which he  terms the primitive dental 
DEVELOPMENT OF THE TEETH.
533
groove, and which is apparent in the foetus of six weeks old.  At the
bottom of this  groove  there  appear certain  fine papillae, which in-
crease in size, and gradually assume the shape of the crowns of the
future teeth, having the edge  and cusps which are  eventually to dis-
tinguish  them.  As the papillae grow, the groove is converted into
follicles  for their reception, by the growth of septa  between its bor-
ders, that is, between the outer and inner alveolar processes, which
soon begin to be ossified within  the walls of the  groove.   Thus the
follicles become alveoli lined  by the periosteum of the jaw, such as it
is at this early period, and lodging a process of  the mucous  mem-
brane of the gum,  from the bottom of which springs up  the papilla
or germ of the future tooth.  The  summit of the papilla is at first
visible in the mouth of the follicle; but ere it has assumed the figure
of the  tooth, the margins of  the orifice enlarge and lap  over, and
finally meet and unite, so as  to form a  lid or operculum to the now
closed cavity.   Thus the epithelium of the lining  membrane of the
mouth may  be shown to form the lining of  the  follicle, and to be  re-
flected thence  over the surface of the papilla.
   Now, the tooth papilla must  be regarded  as homologous with,  or
answering to, the tactile and hair papillae of the skin, already described
 at a former page ;  and it would, therefore, be expected that its main
part would consist  of a peculiar  sub-mucous  tissue, covered by a ho-
mogeneous basement membrane, and surmounted by a tissue answer-
ing  to the epithelium ;  and this  seems  actually the  case.   The sub-
stance of the papilla is at first a congeries
of granular nuclei, dispersed  irregularly
through a firm homogeneous  sub-granu-
lar  matrix, or blastema,  in which ves-
 sels  and nerves are by  degrees deve-
loped.   This  is bounded by a  definite
 transparent membrane, on which rests  a
 reflection  of the  epithelium lining  the
 sac, modified  in structure, so as to pre-
 sent a series of columnar nucleated par-
 ticles, the matrix of the  future  enamel.
 It would appear that the lining and re-
 flected layers of the epithelium become
 blended  together,  and  constitute  but
 one, which  is more adherent to the sac
 than to the papilla, so that on  opening
 the  sac its wall generally seems  to be
 unattached to  the surface of the papilla,
 and the latter  to be limited by  what we
 have regarded as the basement  mem-
 brane. Or, it may be that the epithelium
 reflected over the  papilla  disappears,
 leaving only that which lines the sac.
   Between  the   columnar  epithelium
 thus lining the sac, and the surface  of
 the alveolar cavity, that is, apparently in the wall of the  sac itself, is
Fig. 153.
            oooooo
          00oO00°o°t
    ■r     noo°00Oo„
    B     °nOOOoOOo0
          0,00000c?
           °o ooo

 a.  Vertical section of the enamel-
pulp, with the columnar epithelium,
which is to become the enamel, a.
Pulp. b. Position of basement mem-
brane,  c. Columnar epithelium, some
particles being detached.
 b. Columnar epithelium seen end-
wise.
 From a human foetus of about five
months. Magnified 2U0 diam. 
534
DIGESTION.
now found  a  thick, semi-transparent, pulpy tissue, which has been
termed the enamel-pulp.   It presents towards the pulp of the tooth
(dentinal  pulp) a  series of elevations and depressions, precisely the
reverse of those of the dentinal pulp on which they rest, and answer-
ing mutually to these, with only the columnar epithelium intervening.
The structure of  this thick pulpy tissue is very beautiful and pecu-
liar, as is seen  in the annexed woodcut (fig. 153, a, a).   It consists
of a mesh of short fibres, meeting in numberless points, and at each
point of junction  a transparent clear nucleus is visible.
  It is  elastic, spongy, loaded with fluid  albumen,  but  destitute of
vessels, and it seems perfectly distinct  from that columnar structure
which appears to  be afterwards converted  into the enamel.
  In a vertical sectibn of these parts, the enamel-pulp is seen covered
with  columnar epithelium, the enamel-matrix  (fig 153, a,  c, b), on
the surface towards the dentinal  or tooth-pulp ; while, on the oppo-
site surface, the blood-vessels of the membrane lining the  alveolus
are seen  coming up to, and  forming loops immediately under, the
enamel-pulp, without penetrating it.  It is further remarkable, that
short tubes, filled with  glandular  epithelium, descend among these
vessels from the enamel-pulp, and  end by blind extremities.   How
these tubes, which are evidently  glandular, can discharge their con-
tents, it is difficult to understand, seeing they appear to open into the
substance of the enamel-pulp : but  their presence and precise situa-
tion we have  ascertained to  be as we  have described them  in  the
molar teeth of the nine months, human foetus.
  It is not impossible that the enamel-pulp  may perform the mechani-
cal  office of protecting the soft and  growing tooth from pressure di-
rected on the  gum, and of providing a space in which development
may advance without restraint.
  The next stage is  that of ossification, and the earthy matter is first
deposited in the homogeneous  membrane forming the  surface of the
dentinal pulp.   The most  prominent portions of the crown are the
first to harden; and  the ossification  proceeds inwards by the gradual
conversion of  the  pulp into  the  dentine, or ivory.   The  nucleated
particles of the pulp  nearest the ossifying surface are found arranging
themselves in  series  vertical to that surface; and it appears, that, in
order to form these  vertical series, they multiply by transverse divi-
sion, much as  those  of bone  cartilage are  found to do.  The earthy
matters are  then  deposited in the indistinct  cells  surrounding the
nuclei, so as to form the hard  and dense walls of the dentinal tubes,
as well as in the intercellular substance, so  as to form the intertubular
tissue of the perfect tooth.  The cells unite endwise, and their nuclei
elongate  and coalesce in a  manner to constitute the cavities of the
tubes, and so as often to retain indications  of this  mode of origin in
their permanent form.   In  all these  processes a striking similarity to
those noticed in the  ossification of ordinary bone is to be traced.  In
proportion as the ossification  proceeds inwards, so as  to occupy the
substance of the  dentinal  pulp, the vessels and  nerves which had
been developed in that structure  recede, and  finally come to occupy
the  cavity which remains in the interior of the tooth after its develop- 
DEVELOPMENT OF THE TEETH.
535
ment has been completed.   The chief vascularity of the pulp is uni-
formly found near the ossifying surface, whence it is evident that the
earthy materials are supplied from that source.  In the teeth of some
animals, in which the dentine  is penetrated by many subordinate off-
sets from the central cavity, containing blood-vessels, these passages
are left in the progress of development, just  as  has been above de-
scribed.
   It has been already said that the reflexion of the original mucous
membrane of the follicle on to the papilla takes place at a line corre-
sponding nearly to the neck  of the future tooth, and that the original
papilla answers to the crown or body of the tooth, and not to the root.
This latter is a subsequent formation, and is laid down gradually after
a certain amount of ossification has already taken place in the crown,
and after the enamel has been  calcified.   It is formed and ossified by
a process  precisely similar to that of the  dentine of the crown, only
a  more protracted  one, and during which the tooth is raised out of
its sac, and bursts the containing gum. The lengthening  of the fang
preceding its ossification resembles closely that occurring at the junc-
tion  of the  shaft with  the  epiphyses of the  long bones during their
development (p. 123).
   The calcification of the enamel commences on the surface of the
dentine, in contact with that primary osseous sheet formed from the
basement  membrane of the  dentinal pulp.  On this primary layer are
minute shallow cups, closely  aggregated,  answering to  the ends of
the enamel columns, and receiving them in a firmly cemented union,
as the consolidation  of the elementary cells  proceeds.  The enamel
columns at a very early stage  seem to consist only of a single series
of nucleated particles, intervening between the dentine and the ena-
mel-pulp; but subsequently others are added  on the  surface towards
the enamel-pulp.   Those of the new row arrange themselves endwise
on the others, which they resemble in all respects, so that the enamel
attains its proper thickness rather by the superposition of particle on
particle successively deposited, and by the subsequent calcification
of each in its turn,  than by  the development  of its parts by an inter-
stitial increase; and thus it appears to differ from the dentinal  pulp,
and to resemble the  epithelium, to which it is allied.
   It is from  that surface of the enamel-pulp which looks  towards the
tooth, that this  successive development of  new enamel columns pro-
ceeds ; as they form, this tissue  wastes; but it is not probable that
the pulp is converted into the columns, as the dentinal pulp  is  con-
verted into   dentine, because  the  anatomical characters of the pulp
are so dissimilar from those of  the columns.  When first calcified, the
enamel rods are loosely aggregated, and  easily separate from one an-
other under pressure ;  but  they  gradually become so firmly consoli-
dated by the advance of the calcifying process in their interstices, as
to make  the finished enamel  the most hard and indestructible of all
the products of organization.
   The development  of the layer containing the ordinary lacunae of
bone, and which, in the human teeth, covers the fang, and iscontinued
a  little way  within the cavity  of the root, does not seem to have been 
536
DIGESTION.
so accurately studied as that of the dentine and enamel.  But this is
the less important, as it is in all probability essentially similar to that
of bone, which is now pretty well understood.   There can  be little
doubt  that a membranous  matrix, probably like that of the cranial
bones, is laid down as  the fang is developed, in which the usual steps
of ossification proceed, the lacunae and their canaliculi being, in our
opinion, formed  from the corpuscles of the temporary matrix.   Mr.
Nasmyth has  described a  prolongation of this layer over the entire
crown of the tooth, outside the enamel.  To understand the formation
of such a layer,  we must suppose it laid down in a matrix continuous
with that which  invests the fang, passing over the crown between the
enamel-pulp and the wall of the sac inclusive of the lids.  The crusta
petrosa in the fissures between the enamel of the compound grinders
of herbivorous animals must certainly be formed in  this way.
   When  the  ossification  of the  dentine is so far advanced that the
tooth can sustain with  impunity the pressure to which it is  destined,
and when the enamel  is densely calcified, the eruptive stage occurs,
in which the tooth makes its way through the gum.  This is due to
the  same laws  of  development which govern the form and position
of other organs.  The gum over the sac is absorbed, and the  crown
of the tooth is  forced  upwards  against it, chiefly  by the increasing
size of the fang below.
   It may be stated, once for all, that, as the development of the teeth
proceeds, so does that of the alveoli, or the bony sockets in which
they are lodged  ; and that, by the time the  teeth break through the
gums, their walls  are  sufficiently strong, and embrace  the necks of
the  teeth with  firmness enough to  furnish a solid basis of support.
Their vascular canals are developed, and-especially those which con-
vey to  each tooth  its  interior supply of vessels and  nerves.   The
gums and alveoli are likewise provided with vessels which play their
part in the development and subsequent nutrition of the organs.  The
nerves of the teeth are derived from the second and third divisions
of the fifth pair.
   Of the First and Second Dentitions.—As teeth are required before
the jaw-bones have attained their full  growth, and yet are organs in-
capable of enlarging pari passu with those bones, the young child is
provided with a temporary set, commonly known as the milk-teeth,
adapted to the size and form of its alveolar arches, and to the nature
of the food  consumed in early life.   This set consists of twenty teeth
—four incisors,  two canines, and four  molars in each jaw.  They are
formed in the manner  already described:  the papillae of  the  anterior
molars appearing first—between the sixth and seventh week of fetal
existence, according to Mr. Goodsir—followed by those of the canines,
incisors, and  posterior molars, about the eighth,  ninth, and tenth
weeks respectively.    About the fourth month all these  are  in  their
saccular stage, the mouth of  the follicles  having closed ;  and there
then appear behind the opercula, or lids of the follicles, small  cres-
centic depressions of the mucous membrane, soon becoming closed
cavities, called  by the last-named author " cavities  of reserve, to fur-
nish delicate mucous membrane for the future formation of the pulps 
FIRST AND SECOND DENTITION.
537
and sacs of the ten anterior permanent teeth" in each jaw.  For two
or three weeks longer the primitive dental groove behind the posterior
milk molar is  furnishing the papilla of the first permanent true molar;
and, as this becomes gradually in its turn enclosed in a sac, a cavity
of mucous membrane is said, by Mr. Goodsir, to be left unobliterated
between its sac and the surface of the  gum, which is the " cavity of
reserve" from which the development, first of the second true molar,
and, secondly, of the third or wisdom tooth, is afterwards to proceed.
   The temporary teeth usually make their way through  the  gum as
follows, those of the lower jaw taking precedence:  the  four central
incisors about the seventh month after  birth ; the four lateral incisors
from the seventh to the tenth; the anterior molars from the twelfth to
the fourteenth; the  canines from the fourteenth to the twentieth ; and
the posterior molars from  the  eighteenth  to  the thirty-sixth  month.
This  whole  period is  called  that of  the  first  dentition,  and  is of
great importance to the child, from  the various sympathetic  morbid
states which universal experience attributes to the process of "cutting
the teeth ;" but it would be beside our purpose to dilate in this place
on so interesting and prolific a theme.  It may suffice to say, that, in
our opinion, the practice of lancing the gum over an  advancing tooth
is often unnecessarily and prematurely resorted  to, when  there  is no
evidence, from its tense or inflamed state, that  it is offering any  un-
due obstacle to the progress of the organ beneath.
   The ossification of the  permanent teeth  commences a little before
birth with that of the anterior molars, and  in the course  of the first,
second, and third years it proceeds gradually in the  incisors, the  ca-
nines, and bicuspids.  Their position in the jaw, meanwhile, has been
undergoing change.  The cavities of reserve, from which the devel-
opment of the ten  anterior permanent molars proceeds,  are, at first,
placed between the  milk sacs and the gum; but as the papillae are form-
ed, as already  explained, they recede behind, or to the inner side, and
also pass deeper in  the jaw, and ultimately  get beneath them, acquir-
ing by degrees their alveolar cavities,  and being closely and  some-
what irregularly packed.  As the anterior molar is developed, it soon
comes to  occupy the tuberosity of  the maxilla, and  the  base of  the
coronoid process in the  respective jaws, and, afterwards,  by  the
lengthening of the alveolar arch, descends into place on a level with
those before it.  As this  occurs,  the cavity  of reserve, situated over
it, furnishes the  papilla  and sac  for the second molar,  which soon
occupies the tuberosity or coronoid process, and  then  descends to
behind the anterior  one, a portion of the cavity of reserve being still
left to furnish the hindmost molar or wisdom  tooth  in the same man-
ner.   As these several teeth descend to the  alveolar  arch, the jaw is
proportionally lengthened by a suitable addition from behind ; so that
the circular arch, of which the alveoli at first  consisted, is altered into
an elliptical one.
  As the permanent teeth are  being prepared to penetrate  the  gum,
the bony partitions, which separate their sacs from those of the tem-
porary teeth, are absorbed ; the fangs  of the temporary teeth are re-
moved by a very singular  natural  process;  and the  permanent teeth
     35 
538
DIGESTION.
come to be placed directly under the now loose crowns of the tempo-
rary ones, which finally detach themselves and  allow the permanent
teeth to take their  places in the mouth.  While it is impossible not to
admire the evidence of design furnished by this exquisite process,  it
seems sufficient to  assign it physiologically to that general law which
determines the form and size of the several parts of organized beings.
It has  been supposed  that elongated productions of the cavities of
reserve, which  have been carried down from  the surface  with the
permanent tooth sacs, serve to re-direct them  lo  their proper places
as they rise through the gum.   But it may be asked what served
previously to carry down the pulps aright, and  to  form these guber-
nacula ?   It is  manifest that we must  ascend to a higher secondary
law, to which to refer these wonderful  phenomena of life.
  The periods of eruption of the permanent  teeth, though liable, like
those of the  milk teeth, to some variety, are, according to  Mr. Bell,
usually as follow :—the anterior- true molars at 6^ years of age, the
central incisors at  7, the lateral ones at 8, the  anterior and posterior
bicuspids  at  9 and  10, the canines from 11 to  12, the second true
molars from 12 to  13, and the  wisdom  teeth from 17  to 19.
  Of the Jaw-bones at different Ages.—The bones undergo some inte-
resting changes of form in connection  with  the growth and decay of
the teeth, which have been well explained by Hunter.  The alveolar
processes  in both jaws appear with the teeth, and disappear when no
longer needed  to  support and  enclose them.  In the foetus, before
the eruption of the teeth, the  upper gum is about on a line  with the
articulation of the jaw, the low?er, consequently, is nearly on the same
line, and the angle of the jaw very obtuse.  But as the teeth  pro-
trude, and increase  in number, the lower  jaw is separated from the
upper by the depth of  the alveoli and crowns of the teeth  of  both
jaws, the  body and  ascending ramus  are  both lengthened,  and the
angle approaches nearly to a right angle.  When  the  teeth are sub-
sequently  shed, the alveoli disappear,  and the lower jaw  has to be
much more elevated in order to touch the upper.  But as its body and
ramus cannot return to their  former dimensions, its anterior part  is
thrown a  good  deal beyond the upper in this action, and it is  only
the hinder portions in the situation  previously occupied by  the molar
teeth which come  into contact.
   Of the Articulation of the lower Jaw, and the Movements of Mastica-
tion.—A constant  relation subsists  in  animals between the nature  of
the food, the shape and structure of the teeth, and the articulations  of
the jaw ;  so that, as Cuvier demonstrated, one of these elements being
known, the others may be more or  less accurately inferred.  Thus,
the purely carnivorous animals have teeth fitted to seize and  lacerate
their food, and  the jaw is capable only of the simplest hinge motion.
In the herbivorous families, on the contrary, teeth of a complex kind
are provided for pounding and bruising the food, and the  joints are
so constructed as to allow of extensive sliding motions ; while in all
there is an inter-articular fibro-cartilage for  protection under the ex-
treme  pressure exerted.  The form of the  articulation in man, not
less than  the dental  series, denotes an intermediate condition, and 
THE SALIVA.
539
forms a strong physiological argument for the mixed diet, which gene-
ral custom and taste have decided to be natural to our species.   As
there are cutting, tearing, and grinding teeth, all in moderate propor-
tions, of similar height, and in an uninterrupted row, so the articula-
tion  of the jaw is intermediate between those of the animal and vege-
table feeder.   The  transverse condyle is  received into the glenoid
cavity, and in the slighter movements of mastication and articulation
does not  leave it;  but when the  grinding teeth  are  used, or  the
mouth is opened wide,  the condyle leaves the cavity, and slides for-
wards for nearly an  inch on the prominent root of the  zygoma.  In
the latter action the axis of motion is not in  the condyles, but a little
above the angle of the jaw, and the joint  is arthrodial.   A similar
advance of the condyles may occur with  the  mouth  nearly closed,
the lower incisors being then carried to a level with, or even beyond
the upper ones.  By the advance of one condyle a partial rotation is
effected, the centre of motion being in the other condyle ;  and  when
this  is performed alternately by both sides, together with an elevation
of the jaw, the lower  molars are moved laterally over the upper, so
as to powerfully grind any intervening substance.  The  temporal,
masseteric, and internal pterygoid muscles more or less directly close
the jaw.   The  hinder  fibres  of the temporal and masseter carry it
also  backwards, while the main part of the  masseter, and  especially
the internal pterygoid, advance it.   Both pterygoids carry  it to  the
opposite side,  chiefly by advancing its ramus, the  centre of motion
being then  in the  opposite joint.   The external  pterygoid neither
raises nor  depresses  it.  The depression of the  jaw in mastication
seems to be performed solely by the digastric ; and it may be conjec-
tured that  even this  muscle acts chiefly in  its anterior  belly, which,
unlike the posterior, is  supplied by the inferior maxillary nerve,  the
same which is distributed to the other muscles of mastication.
   Of Insalivation.—The salivary organs  consist  of glands opening
into  the mouth and  pharynx, and furnishing a peculiar fluid which is
there mixed with the food and carried  down with  it to the  stomach.
The  principal  are the parotid, submaxillary, and  sublingual ; and to
these may be added a multitude of small detached glands  of similar
structure,  and  probably yielding  a  similar fluid,  scattered  under the
mucous membrane of the lips, cheeks, soft palate, and parts of the
pharynx.   The  duodenal glands, comprising the pancreas and  the
glands of  Brunner,  which  have much in common with the  salivary
glands,  will be described at a subsequent page.
  The salivary glands need not here be severally described.   The
parotid  is remarkable for its proximity to the temporo-maxillary ar-
ticulation, and  some have attributed its greater activity during mas-
tication  to the pressure to which it is supposed to be then subjected ;
but besides that the fact of pressure may be doubted, so mechani-
cal an hypothesis seems quite superfluous, since the nervous sympa-
thies which so evidently stimulate or control other secretions, as the
tears are  quite sufficient to explain this.   The  parotids pour their
secretions into that compartment of  the  mouth which is outside the 
540
DIGESTION.
teeth, while the ducts of the submaxillary and sublingual glands open
under the tip of the tongue within the alveolar arches.
  The salivary glands consist of  a single excretory duct, continuous
with the mucous membrane,  branching again and again towards the
gland, so as to subdivide  it into a multitude of lobes and lobules in-
vested with subdivisions of a common areolar or fibrous capsule, and
reducible ultimately to follicles of a highly delicate basement  mem-
brane, lined by glandular epithelium, and provided on their exterior
with a network of anastomosing capillaries.   Some anatomists con-
sider that the ultimate follicles of these glands, in which the secretion
is elaborated,  are at  first closed sacs, in  which the epithelium  grows
and is multiplied,  and which discharge themselves at stated intervals
into the  extremities of the duct.  Knowing how difficult it is to  deter-
mine the positive  truth on this question,  we shall merely say that we
are disposed to regard the secreting follicles as permanently open to
the duct, and their secretory epithelium as a continuation of that  which
lines the duct.
  Salivary glands exist in all the vertebrata except fishes.
  The mere sight, or even the idea, of food to a hungry man, excites
the salivary secretion—"  makes the  mouth water;" and during mas-
tication it is poured very abundantly into the mouth, especially at the
commencement of a meal, or if the food  taken is of a savoury quality.
Ordinarily, between meals and at night,  these glands hardly pour out
any secretion ; but there can be little  doubt that in these intervals of
comparative repose of their blood-vessels, the epithelium of the folli-
cles is undergoing those processes of growth  and  change which pre-
cede the actual formation  of the salivary fluid ; and the same may be
said of many  other glands which have an apparently intermittent ac-
tion.  The  quantity of saliva furnished  in a given  time in a state of
health has been variously  computed.  Mitscherlich collected between
two and three ounces from the parotid duct in the course of twenty-
four hours, and nearly fourteen from  the whole of the  salivary organs;
and his  estimate appears worthy  of being relied on.
   The saliva  is a slightly viscid transparent fluid, depositing  a little
flocculent sediment on standing, which consists principally  of the
scaly epithelium of the mouth, and  of other smaller nucleated cells,
which seem to come  from the salivary glands or ducts.   Its viscidity
is increased by mixture with the  mucus  of the mouth.  According to
Dr. Wright, its specific gravity is, on an average,  about 1007-9.  It
is usually alkaline, especially during  a  meal, but often neutral, and
sometimes slightly acid.  Less than two parts in a hundred are organic
or  saline matters, the rest is water.  The organic matters are (besides
the nucleated cells) ptyalin or salivin,fat, (often visible as oil-globules
in the microscope,) and extractive matter, with a trace of  albumen;
the inorganic  constituents are alkaline  lactates, chlorides of sodium
 and potassium, phosphate of lime, some free soda, with sulpho-cyanide
 of  potassium, and perhaps others.  The last named product gives a
red tinge with a  persalt  of  iron, and seems peculiar to the  saliva.
 With regard to the nature and properties of what has  been  termed
 ptyalin, chemists  appear to be by no means agreed, or even whether 
DEGLUTITION.
541
it be at all  peculiar to this secretion.   Dr. Wright, who has paid a
great deal of attention to the saliva, describes it as a yellowish-white,
adhesive, and  nearly solid  matter, having  alone  the  characteristic
odour of saliva, soluble in ether, alcohol, and essential oils, but more
sparingly so in  water; as unaffected by most  of the  agents which coa-
gulate albumen, but as abundantly precipitated  by  subacetate of lead
and  nitrate of silver.   Dr. Franz Simon, on the contrary, describes
ptyalin as insoluble in alcohol and ether; and he adds, "Our know-
ledge of this  substance is by no  means accurate ; and there  is no
doubt that  all the animal fluids yield an  extract to  water,  which
strongly  resembles,  if it be  not altogether  identical  with ptyalin."
Animal Chemistry, translated by Geo. E. Day, (London, 1845,) p. 24.
Dr.  Miller has published a  recent analysis  of the saliva.  Cyclop.
Anat., art.  Organic Analysis, p. 812.
   An obvious use  of the saliva is to aid in reducing  the food to a
pultaceous form, in which it  is more  easily  swallowed.  During the
movements of mastication, it is intimately  mingled with the whole
mass, and  may thus very probably mechanically  enable the gastric
juice to  penetrate more quickly to every part on its  arrival  in the
stomach.  But general experience  attributes the  ill-effects of rapid
eating or bolting of  the food, to the saliva being swallowed in insuf-
ficient quantity, as well as to imperfect  mastication ; and it is a ques-
tion of some interest, to ascertain whether this fluid has  any digestive
powers,  at all allied to those of the gastric juice.  The experiments
of Leuchs have proved that it has the power of  converting starch into
sugar, a  change  similar to  that which occurs  in  the  stomach; and
Spallanzani observed that aliments  enclosed in perforated tubes, and
introduced into the stomachs of living animals, were earlier digested,
when previously  mixed with saliva, than with  water.
   Dr. Wright injected  saliva into the blood-vessels  of  dogs, and
found  the  animals  dying  in a few days or weeks,  with  symptoms
much resembling those of hydrophobia.  In other instances, where
he employed white of egg, isinglass,  and mucus,  no such  effects en-
sued.  Lancet, 1844.   Br. and For.  Med. Rev., Jan. 1847.
   Of Deglutition.—The parts concerned in this  act are the mouth,
the  pharynx, and the  oesophagus, the two  latter of which remain
to be considered.
   The pharynx, as usually described, consists of all that cavity lined
with mucous  membrane which is situated  in front  of the cervical
vertebrae, behind the nose, mouth  and larynx, below the base of the
skull, and above the oesophagus.   This cavity, however, as we shall
show, comprises two parts  entirely  distinct  from one another:  an
upper, with its walls never in contact, lined with ciliated epithelium
and containing air, which we shall term the respiratory compartment,
being in fact strictly a portion of the air-passages ; and a lower, dilat-
able and contractile, lined with scaly epithelium,  and giving passage
to the food from the mouth to the oesophagus, which  we shall term
the  alimentary compartment, as it is a portion of the alimentary tube. 
542
DIGESTION.
 The air-passages are interrupted between the upper compartment and
 the  glottis, and in this interval  the air has to traverse the lower or
 alimentary compartment  in its  course from the nose  to the lungs.
 The alimentary and respiratory tubes  may thus be  said to intersect
 each other in this common cavity, a fact of leading importance to the
 understanding  of the  anatomical  arrangement of these parts.   Not
 to speak of the laws of development to which this free communica-
 tion of the two great tracts ministering to  the nutrient function  may
 be  referrible, (a communication still freer previous to the fusion of
 the sides  of the  palate at an early stage of fcetal existence,) it  may
 be sufficient to allude to the great end answered by it, viz. the bring-
 ing the whole apparatus of the mouth into  connection with the lungs
 for articulation and speech, and  to the subordinate  object of much
 heightening the  sense of  taste  during  mastication,  by allowing the
 odour  of the  food to  ascend from the mouth and  pharynx to the ol-
 factory region through  the  posterior nares.   (See p. 388.)
   From the hinder border of the hard palate passes the soft palate,
 a fold  of mucous membrane enclosing  mucous glands,  a fibrous sub-
 stratum, and several muscles by which it is capable of  various motions.
 This terminates below  by a free border, with the uvula in the centre;
 and  from this border on each side descend  the two pillars  of the soft
 palate: the posterior downwards and backwards, enclosing and mark-
 ing  the course of the palato-pharyngeal muscle, and  dividing the
 alimentary compartment  before  alluded  to from the respiratory one
 above; the anterior downwards and forwards, containing the much-
 smaller palato-glossus  muscle, and dividing the same compartment
 from the mouth.   Thus, this alimentary tract of the  pharynx may be
 said to have its upper part  included within the diverging pillars of the
 soft palate, with the tonsils projecting into it, and to  have  its summit
 formed by  the lower edge with the uvula, the posterior or  upper  sur-
 face of the soft palate pertaining  to the respiratory tract, and the an-
 terior or lower to the mouth.   The mucous membrane of the pharynx
 seen between  the soft  palate  and tongue on opening the  mouth lies
 above  the posterior pillars, and consequently belongs to the  respira-
 tory compartment; and we have on several occasions had  interesting
 proof of this in those cases of  chronic syphilis attended with  a  dry
 state of the pharyngeal membrane, and in which this  part has remain-
 ed dry after the patient has been made  to swallow  water.
  The alimentary compartment of the pharynx has four orifices, all
 capable of closure ; one towards the mouth, bounded by the lower
 edge and anterior pillars of the palate,  by the base of the tongue and
 os hyoides ; another towards the oesophagus, at the lower border of
 the cricoid  cartilage: these two are alimentary.  The  third  opening
 is towards the upper compartment, and is bounded by  the lower border
 of the  palate with the uvula, and by the posterior  pillars with a por-
 tion of the posterior wall ;  the fourth is towards the lungs, and formed
 by the   upper  part  of the  larynx  defended  by the epiglottis; these
two  are respiratory.  The shape  of the alimentary  compartment is
very irregular, and capable  of great alteration by  the movements
partly of the  os hyoides  and tongue with  the larynx, and partly of 
DEGLUTITION.
543
 the constrictor muscles forming its back and sides.  Much lax areolar
 tissue, containing no fat, surrounds it, and allows of these movements
 on the contiguous parts.   As it is impossible in the compass of this
 work to include a special description of the muscles  and other con-
 stituents of the pharynx, we must suppose the reader to have already
 made himself acquainted with them  from the ordinary sources.
   The soft palate contains a thick layer of glands  under its mucous
 membrane, in front of its  muscles; and great numbers are situated
 about the  upper orifice of the  larynx and on the  general surface of
 the pharynx.  The  tonsils  are  large and somewhat peculiar glands
 projecting between the arches of the palate.   They open  by several
 distinct orifices, which lead  into  cells, around  which the secretory
 structure is arranged.   They are very vascular organs, and  evidently
 placed where they are to lubricate the food in its  passage  from the
 mouth.  It is not, however, known  with accuracy  what is the nature
 or composition of the secretion they  furnish ; but it  is,  probably,
 little besides simple mucus. That it is not identical with the saliva may
 be inferred from the difference in structure of the glands, and from
 the tonsils being liable to inflammation and suppuration, as  well as to
 strumous enlargement,  while the salivary glands are seldom or never
 affected in the same way.
   The food when  sufficiently comminuted  and mingled with  saliva
 in the  mouth, and  collected in the hollow of the  tongue, is thrown
 into the alimentary pharynx by the  tongue being pressed upwards
 against the roof of  the  mouth—this  movement beginning at the  tip,
 and ending near the base.   The division of the pharynx which is to
 receive it is dilated as the food enters, by the advance and  elevation
 of the  larynx, and  by  the yielding  of its sides and posterior wall,
 while  the communication with the respiratory compartment  above is
 effectually closed by the  coming together of the posterior pillars of
 the fauces,  by the  contraction  of the palato-pharyngeal  and  upper
 constrictor muscles.  The base of the tongue is now  forced backwards
 and  upwards, so that  the pellet is  pressed between it and the  soft
 palate with its posterior pillars now in contact, and  is thereby carried
 downwards  and  backwards into that portion of the  cavity which  lies
 behind the  larynx.   It crosses over the glottis without entering it,
 because while the larynx is advanced the base of the tongue presses
 back the epiglottis, and so covers the orifice;  this  movement of the
 epiglottis being assisted by the small  aryteno-epiglottidean  muscular
 fibres,  and by the very course of the food itself; but it is abundantly
 proved, that even without an epiglottis the glottis would for the most
 part  be so closed  by sudden spasm of its constrictors, as to prevent
 any alimentary matters  from  falling  into the  larynx.   In the act of
 vomiting, where the matters pass in the contrary direction, it is proba-
 ble that the glottis is partly protected by the backward position of the
tongue and epiglottis and partly by this conservative  contraction of the
arytenoid muscles in answer to the mechanical stimulus of the food on
the mucous membrane in the vicinity.  The pellet of food having arrived
near the oesophagus, is  projected into it by the contraction of the 
544
DIGESTION.
middle and inferior constrictors, the upper portion of that canal being
dilated by  its entrance.
  It might be imagined that a process which may thus be  artificially
divided into consecutive stages, and which combine so many elabo-
rate and harmonized actions, would occupy something more than a
single  second in its performance.  It is, however, quite momentary.
The movements  cannot be  performed separately  by any voluntary
control;  the  food once  willingly thrown by the tongue beyond the
isthmus of the fauces cannot be recalled, but  is necessarily carried
forward to the stomach—a beneficent provision, in which the physical
supersede in a  great degree the mental nervous actions, to ensure the
integrity of the vital function of respiration.   On  the action of the
nerves, however, we need  add nothing to what  has been already
stated (see 296, 306, 307, 487  and 488).
  The oesophagus is a tube  continuous with the  pharynx, fitted to
convey the food past the organs of respiration and circulation in the
thorax to the stomach below the diaphragm.   It  first lies upon the
vertebrae and inclines slightly to the left, but afterwards, in its course
through  the posterior mediastinum, it  advances in front of the de-
scending aorta, and  occupies the  median line.  It is surrounded in
its whole length by a lax areolar tissue, which permits its  dilatation
and contraction during  the passage of the  food.  It has a strong
muscular coat composed of two layers, an outer, of longitudinal
fibres,  which commence from the cricoid cartilage; and an inner, of
circular fibres: both these spread out upon the stomach, and become
much thinner  on that organ.   The fibres of both layers are of the
striped  kind  in the upper part and for a variable way down, some
being often traceable as low as the diaphragm.  In the middle region,
unstriped fibres are  mingled with the others ; and in the lower part
they are  either  the chief or only constituent.  It has  also  a mucous
lining, continuous with that of the pharynx and stomach, but different
from both, being covered with a thicker and more opaque epithelium,
resembling cuticle,  and thrown,  when empty, into  longitudinal folds
by the help of  an abundant areolar tissue between the coats.  Among
the creases, chiefly  in the lower third, are scattered mucous glands,
which open on the surface, and  serve to lubricate the canal during
the passage of food.  The cuticular lining of the oesophagus  is changed
abruptly  at the cardiac orifice of the stomach into the glandular lining
of the  latter  organ.  Thus  the oesophagus is organized as a simple
conduit.   It has considerable muscular  power, and a  comparatively
thick and insensible lining membrane.
  On receiving the morsel forced into its upper orifice by the last act
of pharyngeal  deglutition,  the  oesophagus is mechanically dilated,
and its lining membrane stimulated by the contact.  The  result is a
contraction of  its  muscular coat upon  the pellet, which is thereby
carried forwards into the succeeding portions, in which the like ac-
tions are induced, until  it has traversed  the entire canal.  This series
of actions  is rapid and  quite  involuntary,  but an obscure sensation
attends  it,  which is capable of being  heightened  to  uneasiness or
pain if any obstruction be met with, or if the descending  morsel  be 
THE STOMACH.
545
too hot.   It has been already stated that the contractions are due  to
a central stimulus on the muscular nerves, derived from the pressure
of the food on those of the lining membrane (see p. 490).  It has,
been pointed out by Muller that rapid and slight peristaltic descend-
ing contractions occur in the oesophagus independent of the passage
of food.   These are probably such  as occur in the  intestines and
uterus, without the accustomed stimulus and as a mere  consequence
of their contractility.  In vomiting, the oesophagus has an  inverted
action, the  muscular coat  forcing up the  food  thrown  into it from
below.   In ruminating  animals, this inverted  peristaltic motion  is
capable of being accomplished by the will, and a similar power exists
in some individuals among mankind, of which we have witnessed
more than one striking example.
  On passing a rapid series of electrical shocks down the oesophagus
of a dog just killed, the upper three-fourths of the tube  are thrown
into continued or tetanic contraction, while the lower fourth takes on
a peristaltic or vermicular contraction ; thus demonstrating the situa-
tion  of the change  from the  striped to the unstriped fibres of the
muscular coat, according to the recent test of Weber.
  On the subject of the teeth the student may conveniently refer to the works of
Leeuwenhoek, John Hunter, Thomas Bell;  Tomes, Med. Gaz.  1839-46; Owen,
Odontography; Nasmyth on the Teeth; Miiller's Physiology, by Baly; Goodsir, Ed.
Med. and Surg. Journal, vol.51.  On insalivation, he may consult Dr. Wright's works,
which are of great interest and  value.  On deglutition, Dzondi's observations,  in
Muller, by Baly; a paper by Mr. Fergusson, in Med. Chir.Trans., vol. xxviii. p. 280;
and the Cyclop. Anat., art. (Esophagus, by Dr. Johnson.
                        CHAPTER XXIV.

 DIGESTION CONTINUED.--THE STOMACH.--ITS COATS, PARTICULARLY THE
   MUCOUS  COAT.--STOMACH CELLS  AND  TUBES.--PYLORIC TUBES.--
   MOVEMENTS OF THE STOMACH.--THE GASTRIC JUICE, ITS NATURE AND
   PROPERTIES.--PEPSINE.--STOMACH DIGESTION.

   The  alimentary canal below the diaphragm  is naturally  divided
 into the stomach, the small intestine, and the large intestine, all of
 which are lined by mucous membrane, have  like the oesophagus, a
 double  muscular coat, and  are, besides, invested with a serous mem-
 brane, the  peritoneum, which facilitates the  motions by which  the
 contained matters are propelled from end to end.
   The  stomach, of which  we have first  to  speak, is an elongated
 curved  pouch,  very dilatable  and  contractile, fitted  to receive  the
food  from  the oesophagus, to retain it while acted on by the gastric
 fluid  secreted from the lining membrane, and then to transmit it to
the duodenum  or first part  of the small intestine.   It is expanded
into an  ample cul-de-sac at its left extremity, and becomes gradually
narrower towards the pylorus, where it joins the duodenum.   A cir- 
546
DIGESTION.
cular constriction  is  often apparent  three or  four inches from  the
pylorus,  partially  dividing the  pyloric region from the rest  of  the
cavity.   It has an anterior and posterior surface, which become  re-
spectively rather upper and lower during repletion of the organ (owing
to its change of bulk, and its being fixed at its two orifices), and an
upper and lower curvature, called also lesser  and greater, which un-
dergo a corresponding alteration, becoming rather posterior and an-
terior.  The peritoneum invests  both  surfaces, and passes from them
to the liver (forming the gastro-hepatic omentum), to the  spleen
(forming the  gastro-splenic  omentum), and  to the transverse colon
(forming first the anterior and then  the posterior  layers of the great
omentum).  This  peculiar arrangement of the  serous membrane is
probably intended  to  allow of the extreme changes of  bulk to which
this organ is liable.   The muscular fibres of the stomach are continu-
ous with those of  the oesophagus ;  but, in consequence of its irregu-
lar shape and  its bulging from the cardia towards the  left hypochon-
driurn and the umbilical  region, these fibres are not regularly longitu-
dinal and circular  as in the oesophagus, and as in the intestines. The
outer or longitudinal set  may be best traced along the lesser curvature
and  near the  pylorus; and those  beneath cross  them either at right
angles or obliquely, according to their situation.  Towards the lesser
extremity the  fibres of both layers are much thicker, and  particulary
so at the pylorus  itself,  where they form a circular constriction pro-
jecting the lining membrane,  and capable  of acting  as a sphincter
muscle.  They are of the unstriped variety.
   The mucous membrane of the stomach is thick and soft, and thrown
into  numerous irregular folds by the contraction of the muscular coat,
except in the distended state of the organ.  To be  capable of this
folding, it is separated from the  muscular wall  by a very lax areolar
tissue, containing  no fat, but  filled with the vessels belonging to the
mucous  membrane, and  also containing  nerves.  This is the coat
wrongly  styled nervous by the older writers.
   The stomach is  freely  supplied with blood  by the three divisions
of the cosliac  axis, the coronary, hepatic, and splenic.   The branches
of the arteries reach it  along its  borders, soon  pierce  its muscular
tunic, and form plexuses in the sub-mucous areolar tissue, where they
break up into  numberless finer  ramifications, which  penetrate  the
mucous coat.   The veins accompany the arteries in their distribution
and discharge themselves into the vena portae.   Both orders of vessels
are very  tortuous,  and their contiguous branches  everywhere anasto-
mose freely, so  as to distribute the  sanguineous supplies  equally
during the changing volume of the organ.  The nerves of" the stomach
are derived from  the pneumogastrics and  from the  coeliac plexus.
They advance from the lesser curvature over both surfaces, and after
supplying the  muscular walls, enter the areolar layer under the secre-
ting  lining  membrane.
   The mucous membrane of  the stomach  demands and will well re-
pay an attentive study.   It is of that variety which has been termed
compound mucous  membrane,  i. e. its thickness is made up of  an  in-
finite multitude of tubular involutions of the simple membrane, with 
THE STOMACH.
547
  intermediate vascular, and other tissues sent up into it from  below.
  The simple membrane consists  of basement  membrane  and  epithe-
  lium, both of which are found throughout.  The vessels are uniformly
  on the deep  surface of the basement membrane, and the epithelium
  on  its opposite surface.  The  compound mucous membrane of the
  stomach is thinnest  near the oesophagus, and is usually of a pinker
  colour in  the middle  region, and paler towards the pylorus.
     Over the whole surface of the membrane as seen on laying open
  the organ, and stretching it so as to obliterate the larger folds,  there
  are  visible,  even  with the naked eye, but still better with a lens, a
  multitude of cavities of  very irregular shape, and about 5^tn °f an
  inch in diameter, more or less (fig. 154, a).   These cells are  not the
  result of creasings  of the membrane, and  they do not disappear when
  it is stretched.  They are usually filled with
  mucus, which requires to be removed.  Over
  the greater part of  the stomach they extend
  in depth only about ^th or £th of the thick-
  ness  of the  membrane,  but they are larger
  and  deeper near the pylorus.   In  the ridges
  between them runs a plexus of vessels larger
  than  ordinary capillaries (fig. 155 a, d), and
  which often retains  its blood after death, so
  as to map out the cells in a beautiful manner.
  This plexus is supplied by vessels sent up
  from below, and may  be very easily injected
  artificially.
     The epithelium  which lines these stomach
  cells and covers the ridges  between  them is
  of  the  columnar  variety (fig.  154 b) ;  the
  particles are shorter than in some other parts :
  one  end is free while the other is directed to-
  wards the  basement  membrane;  and they
  contain each a clear  pellucid nucleus near
  their deeper end.   They  seem  to lie in a
  double series, the deeper being in  course  of
  development while the more superficial is in
  course of  decay.  It has appeared to us that
  each particle when arrived at maturity has,
  besides the nucleus, granular contents enclos-
  ed, and that at a subsequent period the gran-
  ular contents escape at the free  extremity by
  a dehiscence or opening of  the  wall at that
  part,  leaving the  transparent husk with its
  nucleus subsisting  for  some  time  longer.
  The clear structureless  mucus which is al-
  most  always found occupying the cells and
  covering the surface of the membrane seems
  to be the  altered contents of these particles
  after  their escape, for the uniform existence
*  of a minute  cavity in the  centre  of it, where it fills the cells,  show
   Fig. 154.



mmf$
&**- -?ess?#P m -#. Jim
afc
_^'*:?
toQP
XY
O

 a. Inner surface of the sto-
mach, showing; the eel Is alter the
mucus has  been washed out.
Magnified 25 diameters.
 b. Columnar epithelium of the
inner surface and cells of the
stomach :—(i Free ends of the
epithelial particles, seen  on
looking down upon the mem-
brane b.  Nuclei visible at a
deeper level  c  The free ends
seen obliquely,  d. Deep or at-
tached ends of the same.  The
oval nuclei  are  seen near the
deeper ends.
 From the dog.  Magnified 300
diameters.
 
548
DIGESTION.
that it has oozed  out  from  every part of their wall, so  as gradually
to fill them up (see fig. 155, a).

          Fig- 155.                                Fig. 156.
  Vertical section of a stomach cell, with its tubes :
a in the middle region, b in the pyloric regt'on.  a a,
Orifices of the cells on the inner surface of the sto-
mach, b b. Different depths at which the columnar epi-
thelium is exchanged for glandular,  c. Pyloric tube,
or prolonged stomach cell.  d. Pyloric tubes, termi-
nating variously, and lined to their extremities with
sub-columnar epithelium.
  From the dog, after twelve hours' fasting.  Magni-
fied 200 diameters.
  a. Horizontal section of a stomach
 cell, a little way within its orifice.
 o. Basement membrane. 6. Colum-
 nar epithelium  All but the centre
 of the cavity of the cell is occupied
 by transparent mucus, which seems
 to have oozed from the open extrem-
 ities of the epithelial particles  c.
 Fibrous matrix  surrounding and
 supporting the basement membrane.
 d. Small blood-vessel.
  b. Horizontal section of a set of
 stomach tubes proceeding  from a
 single cell.  The letters refer to cor-
 responding parts. The epithelium is
 glandular;  the nuclei very delicate ;
 the cavity of the tubes very small,
 and in some cases not visible.
  From the dog. after twelve hours'
 fasting. Magnified 200 diameters.


   It has been  said that the  cells  are so  shallow as to dip into the

 compound  membrane  only about |th  of its  thickness.   The rest of

 its thickness, except near the pylorus,  is made up  of minute tubular

 offsets from the bottom of  the cells, which may be termed the stomach

 tubes, (fig.  155, b;  and  fig.  156,)  and  which  pass  vertically, two,

 three, or four from  each  cell,  afterwards subdividing again and again,

and  becoming more or less tortuous, till they terminate by blind ex-

tremities on a  dense tough  layer  of  areolar tissue continuous with

that  laxer  stratum  which  separates the mucous  from  the  muscular
 coat.

   The  stomach  tubes  have a basement  membrane, and  contain an

 epithelium altogether different from that which has been just described.

Its particles are of  the glandular variety, are  rounded in shape, with-

out obvious  walls ;  their contents are darkly granular, often mixed

with oil  globules, and their nucleus is less distinct.   The tubes are 
THE STOMACH.
549
 so  narrow that the particles seem to fill them, and obliterate their
 cavity, except near their orifices, where  they empty themselves into
 the cells.  Towards  their blind extremities they often  seem to be
 simply a series or pile of epithelial particles; and this has led some
 anatomists to deny that they are  tubes.   The existence, however, of
 a basement membrane convinces us that they are to be regarded truly
 as tubes, permanently laid down in the tissue of the stomach, for the
 origination and discharge of the materials of their peculiar epithelial
 particles on its inner surface.   The tubes proceed in sets, correspond-
 ing to the cells  into which they  open;  those  of each set being en-
 closed in a common envelope of nucleated tissue, like the matrix of
 the kidney and some  other glands.  This firm investing structure is
 attached on the one hand to the dense layer on  which the compound
 membrane rests,  and  on  the other to the ridges between the  cells;
 and it sends delicate processes between the individual tubules of each
 set, and  between their branchings, so as to  sustain every portion in
 its  proper place.  Between the sets of tubules the larger vessels  run
 up  to the  ridges between the cells, and every tubule is invested with
 capillaries, which take for the most part an upward direction, and are
 cut across with the tubules in a transverse section of the latter, (fig.
 155, b, d.)   We  have met with no tubular nerve fibres in the mucous
 membrane of the stomach; but it is highly probable that nucleated
 nerve fibres run among the tubes, though their want of characteristic
 features renders it difficult to positively assert their presence.
  The description now given will  hold good for the whole  lining of
 the stomach, except near the  pylorus.   Here, in many of the lower
 animals which we have examined,—for  example, in the dog, and, it
 may with  probability be inferred, in man also,—a  change occurs in
 a very gradual manner,  but  evidently of an important kind.   The
 membrane is  of a paler tint, and its cells seem not to terminate at
 once in the true stomach  tubes already described, but are prolonged
 into much wider cylindrical tubes,  lined with the same columnar epi-
 thelium, and  descending  nearly or  altogether to  the deeper surface of
 the compound membrane.  For the most part, these prolongations of
 the cells—or, as we shall term them pyloric tubes—end at length in
 very short  and diminutive true  stomach tubes  (fig. 156, b); but we
 have likewise found them terminating in  either  flask-shaped  or  un-
 dilated  extremities, lined throughout with the  sub-columnar variety
 of epithelium, (fig. 156, d.)  Thus  in these animals a marked distinc-
 tion exists between the mucous membrane of the pyloric compartment
 and that of the rest  of the organ, a distinction which must  undoubt-
 edly have an important physiological meaning ; and we have suspected
 that the digestive power of the two parts must differ;  that the  office
 of the pyloric tubes resembles that of the  stomach cells generally,
 and is different from that of the true stomach tubes; that perhaps the
acid product  of the stomach may be furnished by one rather than by
the  other.  We confess,  however,  that we have been unable, on  the
one hand, to  obtain human stomachs sufficiently fresh  and healthy to
test the fact of the anatomical distinctness of  the two regions in man,
or,  on the other, to ascertain the value of the conjectures just alluded 
550
DIGESTION.
to as applied to animals in which the twofold structure is sufficiently
certain.
   It is necessary to examine the changes that occur in the stomach
upon the introduction of food in it.  These changes are threefold:—
1st, as regards its  muscular coat; 2d, as regards its mucous mem-
brane; and, 3d, with respect to the nature and properties of the se-
cretion which is derived from that membrane.
   1. Movements of the  Stomach.—On exposing the  stomach  of a
living animal, or  of one recently killed  while  digestion is going on,
we find that it firmly embraces its contents, and that both orifices are
closed, so as to prevent the escape of the food.  This is particularly
the case as regards the pyloric  orifice in the first period of  digestion.
The contraction of the circular muscle which surrounds  the pylorus
is so strong, that, even after the stomach has been separated from the
intestines, its  contents do not escape for some time.
   This  contraction is due to  the stimulus of the food ;  and, when
the aliment is difficult of digestion, the muscular coat  is proportion-
ably stimulated.
   The movements of the stomach are very different in its cardiac and
in its pyloric portions.  In the cardiac, two-thirds the movements are
very slow and scarcely perceptible, and seem to consist in  little more
than a firm and steady contraction upon the contents, the  muscular
coat thus slowly pushing on the food towards the pyloric portion, and
adapting itself to the diminished size of the organ.  In the  pyloric
portion they resemble closely the peristaltic movements of the intesti-
nal canal, which indeed appear, as it were, to start from the junction
of this portion of  the stomach  with its  cardiac portion.   Under the
influence of the magneto-electric apparatus this mode of contraction
of the pyloric fibres  maybe  well shown  in dpgs or cats just dead,
and the contrast with the  action of the cardiac fibres may be strikingly
displayed.
   We had lately an opportunity of observing the peristaltic character
of the movement of the pyloric portion  of the stomach  during life,
in a woman  in  whom  that organ  was so  enormously enlarged  as to
occupy nearly the  entire abdominal cavity,  the intestines being pushed
into the pelvis, and the arch  of the colon lying behind the stomach.
The patient was so emaciated, and the abdominal parietes so attenu-
ated, that the action of the  viscus could be distinctly seen through
them; and it  appeared to resemble precisely the vermicular action of
the intestines, for which, indeed, it was taken, as the nature  of the case
could not be distinctly recognized during life.
   When the action of the stomach is energetic, a constriction is pro-
duced, by which the  pyloric  third is separated  from the cardiac por-
tion, thus giving rise  to the  hour-glass  contraction, which  continues
for some time after death  if  the animals have been killed at the mo-
ment of its occurrence.   The  same condition  may be produced by
the magneto-electric apparatus.   This constriction  has been  noticed
by all observers in dogs and  cats, and may be  now and then seen in
the human stomach.  In some animals such a  division between the 
         CHANGES IN THE GASTRIC MUCOUS MEMBRANE.       551

 two portions of the stomach exist in the natural conformation  of the
 organ.
   The muscular action of the stomach in man and the mammalia seems
 merely  to push on the food into the intestine, and not to subject it to
 any trituration or mechanical reduction, according to  the views of
 the physiologists of the early part of the last century.  Reaumur, and
 after him Spallanzani, introduced  into the stomachs of dogs and cats
 perforated tubes, made some of brittle and others of flexible materials.
 These were found quite  unaltered by the action  of the stomach, al-
 though  the portions  of  food contained  in  them were  softened and
 digested.
   2. Changes in the mucous membrane of the Stomach.—The gastric
 mucous membrane of the stomach of  an animal killed during stomach
 digestion exhibits a faintish red and swollen appearance, due evidently
 to an increased afflux of blood,  excited by the stimulus  of the food.
 In  the  dog this redness is limited in  a very marked manner to the
 splenic  two-thirds, the pyloric third presenting a  white  colour and a
 wrinkled  appearance,  from the  existence of numerous  minute folds
 upon it, which stretching does not obliterate.   At the same time the
 whole surface of the membrane is covered by a layer of mucus, which
 varies in its thickness and in its viscidity.
   It may be inferred from Beaumont's observations, that similar phe-
 nomena are met with in the human stomach.  Beaumont found that,
 immediately on the introduction of food into the stomach, the vessels
 of the mucous membrane became  more injected,  much,  no doubt, as
 those of the conjunctiva  of the eye would  become filled on the ap-
 plication of a  foreign body;  and that its colour became deeper, being
 changed from a  pale  pink  to a deep red.   A pure, colourless, and
 slightly  viscid fluid, with distinct acid reaction, was then observed to
 distil from  the surface of the membrane, and  to  collect  in drops at
 various  points of it, trickling down the wall of the  stomach until it
 mingled with the food.   The exudation of this fluid was always ex-
 cited by the contact of any foreign substance ; even so smooth  a sub-
 stance as the bulb of a thermometer invariably excited it on its intro-
 duction, and even when  it had been  previously ascertained that  the
 stomach was empty, and  exhibited no reaction.
  During fasting Mr. Beaumont observed no evidence of the  exist-
 ence of such a fluid as this, the  sole contents of  the stomach  being
 then  only  a  little  viscid  mucus,  occasionally slightly acidulated.
 Beaumont describes this fluid as  being clear, transparent, inodorous,
 saltish, and resembling in taste thin mucilaginous water slightly acid-
 ulated with muriatic acid.  It is, he states, readily diffusible in water,
 wine, or spirits, and effervesces slightly with alkaline carbonates.  It
 coagulates  albumen, and  is powerfully antiseptic,  checking putrefac-
 tion  in  meat.  When pure  it will keep for many months;  but if
 diluted  with  saliva, it becomes foetid in a few days.  According to
 the analysis of Professor Dunglison  it contained free muriatic  and
 acetic acids, phosphates and muriates of potass, soda,  magnesia, and
lime.
  Beaumont's observations were made during a period extending be- 
552
DIGESTION.
tween May, 1825, and March, 1833.   Various  observations and ex-
periments, commencing from a date long antecedent to this, had led
to a  very  generally received opinion  among physiologists  that the
mucous membrane of the stomach was the seat of a special secretion,
which had a great share in affecting the changes which the  food un-
dergoes in the stomach.
   Reaumur was the first to offer satisfactory proof of the  secretion
of a solvent fluid for the purposes of digestion by the walls of the
stomach.   He obtained some of this fluid  by making animals  swal-
low sponges, which he could draw out of their  stomachs by a  string
attached; and thus he  was enabled to institute  experiments  on arti-
ficial  digestion, so as to show that alimentary substances  out of the
body  could be altered by  this fluid in the same  manner as they are
changed in the  stomach.   He  likewise introduced  food  into the
stomachs of animals in perforated tubes, whereby they were  defended
from the pressure of the walls of the stomach, but could  imbibe its
fluids.  His experiments disproved  the favourite theory of the day,
which ascribed all changes of the food in stomach digestion to the
influence of trituration upon it by the action of  the muscular coat of
the stomach : they showed  that the trituration in the gizzard of birds
was  no more  than mastication by teeth in other animals, and that
digestion was accomplished in birds of  prey, dogs, &c, and  probably
in man, by the  action of a fluid  which exerted  a solvent  influence
upon  the  food.   Mem. de  VAcad. des  Sciences, an.  1752,  pp. 705-
752.
   Spallanzani  likewise illustrated this  subject  by numerous experi-
ments upon vertebrate animals of all  classes, and  even upon himself.
Following the  plan of Reaumur, he obtained  the gastric juice by
means of  sponges, and he introduced food into the stomachs of ani-
mals enclosed  in perforated tubes and balls.   His essay on  the sub-
ject  of digestion is one of the most interesting  dissertations  in the
literature of physiology, and is full of facts  proving the secretion of
a fluid capable of reducing and dissolving alimentary substances.
   Stevens availed himself  of a rare  opportunity of investigating the
effects produced on food in the human  stomach.   A  hussar  had ac-
customed himself at the early age of seven to swallow stones and
other hard bodies;  and, having continued the practice during twenty
years, what had originated  in idle amusement was now resorted to
as a regular profession, to supply the necessaries of life.  When Dr.
Stevens first saw  him,  his stomach was so  distended, apparently by
the considerable weight to  which it was repeatedly exposed, that he
could swallow several stones at once, which were not only felt  in the
stomach, but might be heard by the bystanders  moving against each
other  when the hypogastric  region was struck.
  Dr. Stevens made this man swallow perforated silver  balls, con-
taining sometimes raw  animal food, sometimes vegetable substances;
in general, raw animal substances suffered less than those which were
roasted  or boiled; roasted  or  boiled  animal substances which had
been mechanically divided  were most completely acted on;  the sub- 
SOLUTION OF THE STOMACH AFTER DEATH.        553
stances contained in balls with large holes were more completely
acted on  than those contained in balls with  minute holes ; and,
lastly, the various vegetable grains, as wheat, rye, barley, oats, and
peas, were least of all altered, having only become moistened and
swollen, while bone underwent no change.
  Dr. Stevens also  introduced  leeches and earthworms in his per-
forated spheres, and found that even these animals, though intro-
duced living, were dissolved as  inanimate matters.*
  John Hunter made some  observations which furnished an inter-
esting proof of  the  existence of a solvent gastric fluid.  He was
struck with  the condition of the stomach in two cases of sudden and
violent death.  A man had his  skull fractured by a single  blow of
a poker; just before the accident he was in perfect health, and had
taken a hearty supper.  Upon  opening  the abdomen, he found that
the stomach, though it still contained a  good deal, was dissolved at
its great  end, and a  considerable part of its contents lay loose in
the general cavity  of the  belly ;  a circumstance, he adds, which
puzzled him very much.   The  second instance was in a man who
died at St. George's Hospital a few hours  after receiving a blow on
his head  which fractured his skull.  In both these cases the solution
was at the splenic end of the stomach ;  the edges of the opening
and the mucous membrane  for  some distance  within were half dis-
solved, "very much," says Hunter,  "like that kind of digestion
which fleshy  parts undergo when half  digested in a living sto-
mach, or when acted  upon by a caustic  alkali, viz., pulpy, tender,
ragged."
  " In these cases," Mr. Hunter adds, " the contents of the stomach
are generally found  loose in the cavity of the abdomen about the
spleen and diaphragm ;  and in many subjects  the influence of this
digestive power extends much farther than  through the stomach.  I
have often found, that, after the stomach had  been dissolved at the
usual place, its contents, let loose, had come into contact with the
spleen and diaphragm, had dissolved  the diaphragm quite through,
and  had partly affected  the adjacent side of the spleen ;  so that
what had been contained in the. stomach was found in the cavity of
the thorax, and had even affected the lungs to  a small degree."
  " There are very few dead  bodies in which the  stomach  at its
great end is not in some degree digested ; and one who is  acquainted
with dissection can easily trace these gradations.   To be sensible of
this  effect, nothing more is necessary than to compare  the  inner
surface of the great end of the stomach with  any other part  of it?
inner surface : the  sound  portions will appear  soft, spongy, and
granulated,  and without distinct bloodvessels, opaque and  thick ;
while the others will appear  smooth, thin, and  more transparent,
and the vessels will  be seen ramifying  in  its substance ;  and upon
squeezing the blood which they contain from the larger branches to

      * De Alimentorum Goncoctione, Edinb. 1777 (in Sraellie's Thes. Mel).
       36 
554
DIGESTION.
the smaller, it will be found to pass out at the digested ends of the
vessels, and to appear like drops on the inner surface."*
   Hunter remarked that solution of the stomach is very commonly
found  in fishes, which almost always die a violent  death, and fre-
quently during digestion.f
   Dr.  Carswell investigated this subject, and obtained results con-
firmatory of the views of John Hunter.   He killed rabbits and dogs
during the digestive process, allowing them to lie for various periods
after death.   If examined four hours after death,  he found that the
solution had affected the mucous, submucous, and muscular tunics ;
when six hours had  elapsed, the peritoneal coat was found softened,
in addition to the others; the stomach was consequently perforated,
and the food passed through the opening and came in contact with
the liver, spleen, diaphragm, and intestines,  one or all of which ex-
hibited the same kind  of softening as that found in the stomach, at
those places where the digested food touched the parts.  In another
series of experiments, where  the animals were  suffered to lie for a
still longer period after  being  killed, perforation of the diaphragm
or oesophagus had taken place, and  the liquid part of  the food had
flowed into the cavity  of the chest, causing digestion and softening
of the pleura and of the lungs.J
   3.  The Gastric Juice.—From these various sources we derive the
most ample evidence of the existence of a fluid secreted by the walls
of the stomach during digestion, capable of  exerting  a reducing or
solvent influence  upon food.  This  fluid is  the  gastric juice—the
succus gastricus.
   It is of great importance to a correct theory of  digestion to de-
termine  the precise composition  of this fluid.   Dr. Prout, in this
country, in  1823, two years prior to the commencement of  Beau-
mont's experiments, had determined  the existence  of  an acid fluid
secreted during digestion, and had  analyzed it in the rabbit,  hare,
horse,  calf,  and dog.  And he announced, as the result of his ana-
lyses, " that free or at least unsaturated muriatic acid, in no  small
quantity, exists in the stomach of those animals during the digestive
process."  And in later publications, Dr. Prout has reasserted this
statement.
   The weight which is so deservedly attached to the opinion of this
eminent philosopher has, no doubt, had great influence in determin-
ing the prevalent opinion in this country in favour of the  view which
attributes the acidity  of the gastric fluid to the existence of free
muriatic acid in it.  The source of the acid,  it is generally believed,
is the chloride  of sodium of the blood, which at  the  mucous  mem-
brane  of the  stomach contributes muriatic or  hydrochloric acid  to
the gastric juice, leaving free soda  to be carried to the liver by the
veins of the stomach.

  * Hunter's Animal Economy, Owen's edition, p. 119.
  | Spallanzani confirmed Hunter's statements.
  j Ed. Med. and Surg. Journal, vol. xxxiv. p. 262.  See also an excellent delinea-
tion of this post-mortem  condition, by Dr. Carswell, in his " Illustrations of the Ele-
mentary Forms of Disease," art. Softening. 
THE GASTRIC JUICE.
555
  Experiment, however, shows that muriatic acid has little  or  no
solvent power on the food, and that  the reducing action of the gas-
tric fluid cannot be attributed to  it-alone.  Albumen or meat sub-
jected to the action of water acidulated with muriatic acid, and kept
for some  hours at a temperature of 100°, undergoes no change
of any importance :  neither  substance  exhibits any softening  or
tendency  to putrefaction or decomposition of  any kind.  Similar
experiments with acetic acid  or with phosphoric acid  lead to like
results.
   It is plain,  then, that the solvent powers of the gastric fluid are
not due simply to the acid which it contains, whatever that may be,
and that we must look for some other ingredient in it, which, either
alone or in  combination with acid, can exercise these powers.  The
clue to this was given by Eberle, who  adopted the expedient of
adding to water acidulated with muriatic acid a  small piece of the
mucous membrane of the stomach.   By this means he succeeded in
obtaining a digestive fluid which reduced animal  substances as per-
fectly as the gastric juice itself.
   This discovery was of the last  importance to  the formation of a
correct theory of stomach digestion, and to exact  views of the nature
of the gastric juice.  It was soon followed up by numerous experi-
ments in Germany, by Schwann and Mliller, and by Purkinje  and
Pappenheim.   The general  result of these  experiments  was, that
the addition  of a  portion of gastric  mucous membrane from the
true secreting  stomach  to an  acidulated water produced  a perfect
digestive fluid;  but that  no other mucous membrane would answer
this purpose.   The following changes take place on macerating meat
and albumen  in a digestive fluid:  The meat is   broken down to a
complete pulp; and if the digestion have been continued sufficiently
long, it is dissolved.    The  albumen is likewise equally softened.
The early changes which take place in  a cubic piece of solid white
of egg, macerated in the digestive fluid, are  very characteristic.
Its edges become of a  pearly hue, semi-transparent, almost fluid,
breaking down under the slightest touch of the  finger ; and, after
longer digestion, the solid matters are completely dissolved.
   The solvent power  of a digestive fluid made with the mucous
membrane of tho  stomach is  strikingly displayed if the  results  of
the digestion of meat and albumen  with it be compared with those
obtained  by digesting  pieces  of  the same substances  either with
simply acidulated  water — muriatic,  acetic,  or  phosphoric acid
being used—or with an infusion of mucous membrane without acid.
Simple acidulated fluids produce little or no change in  meat and
albumen  in the course  of twelve or twenty-four hours ;  and such
change as is produced presents a marked contrast to that caused by
the infusion  of mucous membrane  with  acid.    No acid,  however,
appears  to cause more  change than the  phosphoric.   When the
infusion of  mucous membrane is used without acid, rapid putrescence
is produced.  A similar effect results, although  with less intensity,
from  the use of too little  acid ; and, if  alkali be added, the putre-
faction becomes still more rapid and intense. 
556                       DIGESTION.
   In these experiments, it is of great importance to pay close atten-
tion to the temperature.   It should be within the range of from 90°
to 110°, the higher temperature increasing the energy of the diges-
tive action.   If it reach  the point at which albumen  is coagulated,
all solvent change ceases, and the meat or albumen becomes hard-
ened.  In a low temperature,  likewise, there is  no change ;  the
digestive fluid under such circumstances serving merely to prevent
decomposition.
   The antiseptic power of an acid infusion of gastric mucous mem-
brane is one of its most remarkable properties; and in this  respect
it resembles the gastric fluid itself, which, according to all observers,
is remarkably antiseptic, being capable of checking the further pro-
gress of putrefaction in meat in which that process had already
begun.   This power  seems  principally due to the acid, the neu-
tralization of which destroys it;  and if an infusion  of mucous mem-
brane to which enough acid  had not  been added become putrescent,
its further decomposition may be checked by the addition  of more
acid.  We have kept  the artificial digestive  fluid for many months
in a bottle with a common cork without its undergoing any change.
   The gastric fluid possesses the property of causing the coagulation
of the caseine of  milk ;  an  artificial digestive fluid made from the
mucous membrane of  the  true stomach of ruminants possesses the
same power, even  if its  acid be  neutralized by potass.  This fact
has been long known to the makers of cheese ; and the dried mucous
membrane of the fourth stomach  of  the calf  has been used, under
the name of rennet, for the purpose of coagulating that principle in
milk.  That it possesses this power independently of any acid which
it may  contain, was first pointed  out by Berzelius.  Some have
affirmed that this  power belongs only to the  mucous membrane of
the stomach of sucking animals.
   A fluid of such digestive power as that above described cannot be
made from any mucous membrane but that  of the stomach.  The
mucous  membrane of the bladder, of the  greatest portion of the
intestinal canal, is quite insufficient for this purpose ; but that of the
duodenum appears to exert some solvent influence.
   The Organic Principle of the Gastric Juice.—All these facts show
that the gastric  mucous membrane contains  some  material, which,
when dissolved or  diffused in acidulated water, exercises  a  power
not to be  distinguished from that of the gastric juice itself.  Can
this material be isolated ?   There is  no doubt that we can  obtain
from the mucous membrane  of the digestive  stomach of animals, an
organic substance, which exhibits reactions  in close analogy with
those of albumen,  and  which exercises a solvent or catalytic influ-
ence upon various  azotized substances; to this substance Schwann
and Muller  gave the name pepsine.*
   Valentin  very justly remarks that the organic combinations upon
which the solvent power of the gastric fluid depends, share the same
fate with other contact substances, namely, that they cannot be ob-
* Also called gasterase, by French writers. 
THE GASTRIC JUICE.
557
tained in perfect  purity, nor can their  precise relative proportions
be determined with  exactness.  Pepsine, therefore,  he adds, can
only be regarded  as an hypothetical or conventional name for an un-
known mass which may be separated  by alcohol, or by lead and al-
cohol in combination with other bodies.  Nor do the reagents indi-
cate any definite character—they only afford conjectural information.
To view it as a kind of diastase, whilst it does not remove our diffi-
culty, nevertheless denotes the power of the unknown substance in
a more precise and definite manner.
  An artificial digestive fluid may be  made in the following manner.
Let  a piece of the mucous  membrane of the stomach of a pig be
macerated in distilled water for twelve hours at the temperature of
98°  or 100° ;  afterwards, add  dilute muriatic acid to the fluid until
it redissolves the  precipitate which is at first thrown down ; the fluid
thus formed will  be  found to possess  full digestive powers, and all
the properties of the gastric fluid.  It  is, in fact, an acidulated so-
lution of pepsine in water.   The pepsine may be  precipitated from
this  solution by  some of the  reagents  which  coagulate albumen.
Bichloride of mercury will do this, and render the  fluid inert.   Al-
cohol and water at the boiling  temperature produce the same effect;
the precipitate, however, thrown down by alcohol, is capable of being
redissolved in water, and then, with  acid, will produce a digestive
fluid.  Tannin also precipitates it.  It is evident, therefore, that the
digestive fluid contains a principle  capable of affording distinct re-
actions.   The solvents of this principle are water and dilute muria-
tic or acetic acids.
  The power which the  digestive fluid has of coagulating  caseine,
independently  of its acid,  denotes that it holds  in solution  some
special agent derived from the  mucous membrane of the stomach.
 - Alcohol added  to a fresh infusion  of mucous membrane  throws
down a white flocculent precipitate,  which may be collected  on a
filter, and when  dried  will  produce  a gray compact mass.   This,
when redissolved in water, will  exhibit digestive powers, and these
powers are greatest when it is united with acetic and muriatic acids.
We  obtain in this way the nearest approach to  the isolation of pep-
sine.
   The Acid of the  Gastric Juice.—Of the existence of an organic
principle, a secondary organic  compound, the product of the secre-
tory action of the mucous membrane  of the  stomach, no doubt can
be entertained ; but we can speak  with less certainty of the nature
of the acid which exists along with it in the  gastric fluid of the
stomach, inasmuch as recent observers  have thrown a  doubt upon
the correctness of Prout's opinion.   The following  are  the most re-
cent opinions put forward on this subject.
  Blondlot affirms that the  acidity  of the gastric juice is due not to
the presence of a free acid, but to the existence of biphosphate of
lime  as  one of  its  ingredients.   To this,  however, Melsens and
Dumas raise the  objection  that carbonate of lime, or Iceland  spar,
placed in gastric juice for some hours,  becomes corroded and suffers a
very notable diminution of weight, which can arise solely from the pres- 
558
DIGESTION.
 ence of a free acid.   MM.  Bernard  and Barreswil likewise  state
 some strong objections to the views of M.  Blondlot in a paper pub-
 lished in 1844.  They show that M. Blondlot failed to obtain effer-
 vescence by adding carbonate  of lime to gastric  juice, because he
 employed a  too much diluted fluid;  on  concentrating  the gastric
 juice a  little,  the  effect  was readily produced.  Admitting that a
 free acid is present, they deny  that it  is hydrochloric  acid, because
 that acid exists in  the gastric fluid only in the state of chloride.  If
 a minute quantity  of oxalic acid be  added to the gastric juice, a  pre-
 cipitation is occasioned by the formation of insoluble oxalate of lime,
 whilst  an equal quantity of the same reagent,  added  to distilled
 water containing  a  two-thousandth part  of  hydrochloric acid, to
 which chloride of  lime  had been added, produced  no such  effect.
 The lime of the gastric juice unites with  the oxalic  acid;  but  that
 acid will not displace lime from  its connection with hydrochloric acid.
 Nor is the acid of  the gastric juice  free acetic acid ;  the most deli-
 cate tests failed to detect it.   MM. Bernard  .and  Barreswil infer
 that there is in the gastric fluid a minute proportion of phosphoric acid,
 which,  however, is not the only free acid.  The lactic acid, accord-
 ing to these observers, is the principal acid of the gastric juice, be-
 cause the behaviour of a fluid acidulated with that acid corresponds
 very exactly under chemical examination with that  of the gastric
 juice.   Thus the distillation of water acidulated with lactic  acid
 exhibits exactly the same stages as  that of the gastric fluid—first,
 there passes over only pure  water, in the  next  stage  an acid liquid,
■ in which salts  of silver do not throw down a precipitate, and there
 remains a strongly acid fluid effervescing  with carbonates; in this,
 remaining  liquid  hydrochloric acid may be detected, if a minute
 quantity of  chloride of sodium had been added to the fluid previous
 to distillation.
    The  acid of the gastric juice produces salts of zinc, lime, baryta,
 and copper, similar to those formed by lactic acid ; and MM. Ber-
 nard and Barreswil affirm that  it readily decomposes the  chlorides
 in concentrated solutions.   Hence  it is that  hydrochloric  acid
 passes over in  the last products of the  distillation  of the gastric
 juice.
    These authors also state that the  nature of the food  appears to ex-
 ercise no influence upon  the nature of the acid, and that they have
 always found free  lactic  acid, whether after an exclusive  vegetable
 or animal regimen continued for many days, or after a prolonged
 very sparing diet.
    Dr.  R. D.  Thompson, of Glasgow,  in a paper published in 1845,
 also  disproves the opinion  of  Blondlot by experiment, and comes
 to the conclusion that the free  acid of the stomach,  in the digestion
 of vegetable matter at least, of all the  known acids corresponds  only
 with the lactic.
    Lehmann attributes the acidity  of  the  gastric fluid to both free
 hydrochloric and lactic acids.   He obtained  the former from the
 stomach of a  diabetic  patient, to  whom  he  had administered an
 ipecacuanha  emetic ; and the latter  from the  stomach  of a  cat, 
THE GASTRIC JUICE.
559
  from which he was able to procure distinct crystals of lactate of zinc.
  In subsequent researches, Lehmann confirmed this conclusion respect-
  ing the nature of  the acid of the gastric fluid.
   _ Liebig lends his sanction to this doctrine, and especially to  the
  view put forward  by Bernard and  Barreswil, that  both lactic and
  phosphoric acids exist in  this fluid  free, while there is no reason  to
  deny the existence of an acid phosphate  likewise.  The  opinion
  that free lactic acid exists  in the gastric fluid is not new.   It was
  put forward by Chevreul  many years ago, and afterwards by Leuret
  and  Lassaigne.  In 1823 our distinguished friend, Dr.  Graves, of
  Dublin^ published  analyses of the fluid of  the stomach from two  pa-
  tients, in which he found  free lactic acid  in abundance.  Notwith-
  standing what has  been done on this subject, it must be  confessed
  that the  full truth has scarcely yet been arrived at.  We have yet
  to learn whether the constitution of the gastric juice  is constant—
  whether the same acids or acidifying agents  are present in all ani-
  mals, and under all conditions of feeding and food ; and we have
 also  to ascertain whether  any and  what changes may be  produced
 by disease in the chemical characters of the gastric fluid.  The  in-
 quiry taken up on  a large scale among  the  lower animals, and ex-
 tended to man, in health and  disease, would, no  doubt, yield  most
 valuable and interesting results.
   The digestive principle  does not seem  to be secreted in  equal
 quantity  or of equal power at all parts of the stomach.  Meat and
 albumen, digested with mucous membrane from the cardia, is  by  no
 means so much acted  upon as if  digested with  mucous membrane
 from  the pylorus or from the central part of the stomach.  In the pig,
 there is a large patch  of  the  membrane of a reddish hue, and  of
 considerable thickness, forming that portion of the mucous membrane
 which corresponds to the middle of the great curvature  of the sto-
 mach;  this, we find, exercises a more energetic action upon meat  or
 albumen than any other part.
   It  is highly interesting  to  notice that the mucus which accumu-
 lates  upon the  surface  of the mucous membrane of the stomach has
 a digesting power  corresponding to that of the portion of mucous
 membrane from which  it has been taken.  This we have determined
 by our own experiments.
   Nature of the Digesting Power  of the  Gastric Juice.—Havino-
 stated the leading facts which observation and experiment  have de-
 veloped respecting  the act of digestion  in the stomach, it remains
 to inquire what is  the real nature of the digesting  power of the
 gastric fluid.
   Two questions present themselves for consideration: is the digest-
 ing power of the stomach  a true solvent power, producing simply
 a solution of the matters submitted  to its action, without  effecting
 any change in their chemical constitution? or  does the digestive fluid
exercise a catalytic  action on the substances submitted to it, where-
by it effects a chemical decomposition of them, similar to that pro-
duced in  barley by diastase,  whereby  the starch of  the  grain  is 
560
DIGESTION.
converted into sugar, or like the action of yeast upon sugar, whereby
the latter is decomposed into carbonic acid and alcohol?
  To decide these questions, it is  necessary to examine the exact
nature of the changes  produced in  the food by stomach digestion.
  Milk.—If milk be introduced into the stomach, its caseine is first
coagulated  and afterwards apparently dissolved.   The solidified
caseine seems gradually to melt down  and becomes absorbed.   In
overfed infants, milk-curd  appears  in  the stools in  considerable
quantity,  the child having received so much milk that its stomach
is  unable to digest  the caseine precipitated from it.  When, how-
ever, the quantity of milk is in just proportion to the digestive
power of  the stomach, all the  curd is digested, and therefore none
is found in the  stools.
  Albumen.—White of egg (ovalbumen), if swallowed raw, is imme-
diately coagulated by  the gastric juice and then dissolved.  Tiede-
mann and Gmelin found that,  after three  hours' sojourn in the sto-
mach of a dog, albumen was dissolved, forming  " a yellowish mucous
liquor," which  coagulated readily by heat.
   Coagulated albumen becomes softened down and dissolved in the
fluids of  the stomach, from which  it may again  be precipitated  by
heat or nitric acid.
   In experiments with the artificial digestive fluid, we find that if
the  fluid  in which albumen had been  digested be carefully filtered
and subjected to heat  and nitric acid, a copious precipitate of albu-
men will take place.
   Meat is softened, gelatinized, and dissolved, and albumen may be
precipitated by heat, nitric acid, or ferrocyanate of potass from the
liquids obtained from the stomach.
   Vegetable Substances.—In all the experiments upon animals of the
carnivorous  kind (cats, dogs), bread, potatoes, and  other vegetable
substances underwent change much  more slowly than animal matters,
and they  became  softened by  admixture with  the fluids of the  sto-
mach and appeared partially dissolved.
   Boiled starch, in Tiedemann  and  Gmelin's experiments, underwent
solution, and then did not exhibit its characteristic blue colour with
iodine.  In a dog, killed five hours after a meal of boiled starch, the
contents of the stomach  underwent no change of colour with iodine,
but appeared charged  with  sugar and with a kind of gum of starch
{dextrine).   In  another dog,  similarly fed, and killed three hours
afterwards, the starch which was dissolved did not react in the usual
manner with iodine, but some portions not  yet dissolved  did exhibit
the  characteristic reactions.   It would seem that  immediately the
starch becomes dissolved by the gastric fluid it loses its characteristic
property of forming the blue iodide of  starch.*
   In the  artificial digestion of starch, with  the mucous  membrane of
the human stomach, we have not succeeded in producing any change
in the starch: it still evinced its usual reaction with the iodine test.

  * Tiedemann and Gmelin, Recherches sur la Digestion, par Jourdain, t. i. p. 340. 
RATE OF STOMACH DIGESTION.              561
We have, however, found that starch digested for some time in  this
way evolved a peculiar sour smell like that of cheese.
  Bouchardat  and  Sandras report, respecting  the  influence of
stomach digestion upon starch, and upon amylaceous elements, differ-
ently from Tiedemann and Gmelin.   They state that they have been
unable to obtain any evidence of the conversion of starch into sugar;
that neither by fermentation, nor by the polarizing  apparatus of M.
Biot, have they succeeded in procuring  any indication of  the exist-
ence  of sugar  in  the digested substances;  and they were  equally
unsuccessful  in  detecting the formation of  dextrine.   Lactic  acid,
howrever,  appeared to them to be formed in much larger quantity
after a  meal of starch than after one of fibrine or of gluten.   These
observers likewise  state as  the result of their experiments,  that in
the human subject, and in  the carnivora, feculent substances are
digested with extreme slowness, and not at all unless the integument
of the starch-grain have been ruptured  by boiling.
  Fatty or oily  substances,  as suet, fat, oil, butter, or wax, undergo
no change in the stomach, according to Bouchardat  and Sandras,
after  the  lapse of  some hours, and may be found in that organ un-
changed,  in the midst of other  matters upon which  the stomach
exercises  a solvent action.
  This  we have observed in our own experiments; and on perusing
the MS.  notes  of the results of various experiments made thirty
years ago by Sir B. C. Brodie, and with great  kindness  placed at
our disposal by  him, we  find the following statement:  "When dogs
were fed on lard, the lard passed into the small intestine unchanged."
  It would seem Jo be the most reasonable conclusion which we can
deduce  from  the preceding statements, that, in man and the  car-
nivora,  the fluid secreted by the stomach  during digestion simply
dissolves animal and vegetable substances of the azotized kind, with-
out altering their  chemical constitution, leaving amylaceous, oily,
saccharine, and  the allied substances but little or not at  all acted
upon.
  The Chyme.—The mass that is contained in the stomach  after
digestion has been  going on for four or five hours, and which is com-
monly known by the name of chyme, consists of aliments  dissolved,
or softened and prepared for solution or other change by the gastric
juice.   As they are mostly of the same  kind, this mass  presents a
homogeneous appearance, except when substances are present which
either require a  longer sojourn in the stomach or are only  digestible
by some lower portion of the intestinal tube.
  Rate of Stomach Digestion.—The process of stomach digestion is
a slow one.  In the  artificial digestions  above referred to, it took
from eight to twelve hours to produce any marked effect upon the
pieces of meat and albumen submitted to the action of the digestive
fluid.  This, however, is much longer than the natural process.  Ac-
cording to Dr.  Beaumont's researches  upon Alexis St. Martin, it
took three or four  hours before the stomach became empty after a
meal  consisting chiefly of azotized food—and his tables show that
the mean  time  required for the  digestion of the principal animal 
562                        DIGESTION.
substances in common use, such as butcher's meat, fowl, game, was
from two hours and three-quarters to four hours.
  In experiments on  dogs, it has been found by most experimenters
that no great advance in the solution of the contents of the stomach
is made under from  two to four  hours.   Gosse, who possessed the
power  of disgorging the contents of his stomach by previously swal-
lowing a quantity of  air, found that no change had taken  place in
the food after it had remained half an hour in the stomach: after the
lapse of an hour he found the food much  softened—but not reduced
in weight: while, after two hours,  it was not  only much softened but
considerably reduced in quantity, so that he could not return from
his  stomach more than half what he had taken.*
  Purkinje and  Pappenheim found, in their  experiments upon arti-
ficial digestion, that,  by gently shaking the tubes in which the pro-
cess of digestion was going on, it became  accelerated.  This accords
with what daily  experience  points out to  us,  namely, that agreeable
and lively conversation during a meal, or gentle exercise after one,
invariably promotes the primary stages of digestion.
  Violent exercise after meals retards digestion, most probably by
preventing the constant action of the gastric fluid upon the  pieces of
food in it—the  movements of the body causing frequent change of
place in the morsels  of food.
  The use of alcoholic stimulants also retards digestion, by coagu-
lating  the pepsine, and thereby interfering with its action.  Were
it not that wine  and spirits  are rapidly absorbed, the introduction of
them  into the stomach in any quantity would be a complete  bar to
the solution of the food, as  the pepsine would be precipitated from
solution as quickly as it was secreted by the  stomach.
  Absorption by the Stomach.—An important question,  to which as
yet we can give  no certain reply,  is as to  what becomes of  the food
after it has been  duly dissolved by the fluids  of the stomach.  When
we  find how completely albuminous and fibrinous substances are dis-
solved  by digestion in the natural  or artificial gastric fluid, it cannot
be doubted that  they are in a state fit for  absorption while yet in the
stomach, nor can there be any good reason to deny that a consider-
able quantity must  be absorbed without  passing  further on in the
alimentary canal.  The great rapidity with which liquids of a simple
and limpid kind,  or the aqueous solutions of certain salts, as  iodide
of potassium, the alkaline carbonates, &c, find their way  into the
blood,  denotes that this must take  place very quickly after they have
been swallowed,  and that the bloodvessels of the stomach  must be
the principal channel through which  they effect their entrance into
the circulating system, and  it scarcely admits of doubt that the dis-
solved  aliments are removed through the  same  channels.f
  The  venous  blood of the  stomach passes  to the vena portae.
Hence, matters absorbed by the sanguiferous system of the  stomach

  *  QSuvres de Spallanzani, par Senebier, t. ii.
  |  We have detected iodine in the saliva and urine  in twenty minutes after a solution
of a few grains of iodide of potassium in a large quantity of water had been swallowed. 
VOMITING.
563
pass by a very direct  route  to  the  liver, and probably excite that
gland  to  increased secretion for the  purpose of digestion  in  the
small intestine.
   The gastric fluid dissolves perfectly only the fibrinous and albumi-
nous animal substances, and probably also  the glutinous or azotized
portion of vegetable food; we must suppose, therefore, that it is only
these portions of the solid aliments which are absorbed by the sto-
mach.  Drinks, as water and various other liquids, fermented  or not,
are, doubtless, likewise in great part absorbed  in the same way.
All other kinds of food, and such remaining portions of the azotized
or liquid aliments as have  escaped absorption by the stomach, after
having undergone to a certain  extent maceration in it, are pushed
onwards into other parts of the  digestive tube, there to undergo fur-
ther changes to fit them for being absorbed.
   Eructation and Vomiting.—As there can be no doubt that  the
movements  of the stomach  are capable of  pushing on  the food to-
wards the intestinal canal, it appears prima facie extremely proba-
ble that the same muscular force may cause it to evacuate its contents
through the oesophagus, if there be any obstacle to their downward
passage, too strong to  be  overcome.*  The muscular  coat  of the
stomach, pressing by its passive contraction upon its contents, will
cause them  to pass in that direction which offers the least resistance.
Now, in a state of health,  the food,  in  order to  return  by the oeso-
phagus, must not only overcome the passive contraction of the mus-
cular coat of that tube, but it must also  ascend against gravity.
Moreover, the action of the fibres of the  splenic extremity of the
stomach favours the passage of the food toward the pylorus.  Hence,
not only is there least  resistance at the pylorus, but there is likewise
a vis a tergo, which favours the  propulsion of the food in that direc-
tion.
   When, however, air  accumulates at the cardia  in such quantity as
to distend that portion of  the stomach, it opens  the oesophagus by
its expansile force, and from its  lightness rushes up the oesophagus,
carrying with it sometimes liquid or solid food.   When air is gene-
rated in large quantity and with great rapidity,  it is wonderful how
much may escape in this way, and large quantities of food may be
discharged from the stomach at the same  time, solely by the con-
vective force of the large bubbles of air ascending from it.  This is
eructation—it seems due solely  to the presence of a large quantity
of air in the stomach.
   Vomiting is an act of a  more complex character than eructation;
by it  solids and liquids may be expelled from the stomach through
the oesophagus, even contrary to gravity.   We must assume that a
necessary condition for the production of the act of vomiting is the
existence of obstruction at or near the pyloric portion of the stomach,
which prevents or opposes the passage of the gastric contents in that

  * The old and still prevalent notion of an inversion in the  action of the stomacli is
most probably erroneous. The inversion is only apparent, not real. See an able paper
by Dr. Brinton on this subject.—Lond. Med. Gazette, 1849. 
564
DIGESTION.
direction.  Probably the whole of the pyloric third of the stomach
is strongly contracted under the circumstances which ordinarily give
rise to vomiting; and the contents of the viscus having been accumu-
lated  in its cardiac two-thirds,  are thus brought into more immediate
and direct communication with the oesophagus.  The pylorus being
closed against them, the stomach contents are forced through the
oesophagus, not  only by the muscular contraction of the stomach
itself, but also by that of the abdominal muscles and the diaphragm.*
  It is probable that where a very complete obstruction exists at or
near the pylorus, as in cases of hernia and other mechanical obstacles,
the act of vomiting partakes much of the nature of an overflow, and
requires  no more than the action of the muscular coat of the stomach
itself.  The  slight effort  which accompanies  the  discharge  of the
stomach's contents in cases of this description, denotes  this.  But
when vomiting is  caused  by an emetic, or is the  result of sea-sick-
ness,  or of nervous irritation, as in stimulation of the fauces, or in
brain  disease, an  active and  almost  convulsive contraction of the
diaphragm and  abdominal  muscles  accompanies  it,  and,  no doubt,
constitutes the principal expelling force.   These  muscles, by their
simultaneous forcible contraction, form two plane surfaces, one pass-
ing downwards  and backwards, the  other nearly vertically down-
wards, which are approximated very closely to each other, and com-
pressing  the stomach between them, cause the forcible ejection of its
contents  in that direction, which offers least or no resistance, namely,
through  the oesophagus.
  The act of  vomiting  is ushered  in  by a deep inspiration, during
which the diaphragm is firmly  contracted.  Just at this moment the
abdominal muscles contract forcibly and almost convulsively.  Thus
an effort at expiration,  in which, doubtless, other muscles take part,
besides those of the abdominal walls, quickly  succeeds the act of in-
spiration.  But  the diaphragm does not become relaxed as  in ordi-
nary  expiratory efforts, because the  air  is only very partially and
slowly expelled..   For,  at the same time that  the abdominal muscles
and the diaphragm are  thrown  into contraction, those of the glottis
are exerted to a like convulsive action, and maintain a partially closed
state  of the glottis which resists the expulsion of  air from the lungs
and keeps  them in a certain state of distension until the effort of
vomiting is over, when  the diaphragm relaxes and complete expira-
tion  takes place.   That  there cannot be complete closure of the
glottis in the effort of vomiting, is shown by the fact that that act is
very frequently  accompanied by a loud explosive noise, which must
be formed in an open, although a resisting glottis.
  Dr. Anderson  has shown by direct experiment that when  dogs
vomit under the influence of tartar emetic, the diaphragm is forcibly
contracted.  He introduced  his finger into the abdomen, and found
that during each  effort of  vomiting the  diaphragm  became tense

  * The power of returning portions of the food at will (rumination), which some men
have acquired, is effected by a strong voluntary contraction of the pyloric muscle, and
by expulsive efforts operating directly on the cardia portion of the stomach, which can
thus expel  its contents only in the upward direction. 
VOMITING.
565
and rigid, and descended towards the abdomen.  And this he found
took place even when the trachea had been previously opened; whence
we  may- infer that the force of the expiratory muscles  is spent
chiefly upon the stomach.*
  A warm controversy took place in the last century, and was re-
vived in the present,  with reference to the share which the stomach
itself takes in the act of vomiting.   Many high names in physiology
took  part in this discussion, some maintaining, among whom was
John Hunter, and subsequently, Magendie,  that the  stomach was
perfectly passive, and that the abdominal muscles and the diaphragm
were  the sole agents of expulsion; while  others, as Haller, Rudolphi,
&c, allowed  that the contractions of these muscles  only assist  the
expulsive efforts of the stomach, which, in some instances, may act
independently of the surrounding muscles.  Maingault affirmed that
he had seen vomiting occur after the division of the  diaphragm and
the abdominal muscles, and Rudolphi made the same assertion.  And
the Committee of the French Academy  appointed to investigate the
question, admitted that it needed only a very slight external pres-
sure to produce  vomiting, and that distinct contractions of the mus-
cular coat of the stomach were seen during the act in the neighbour-
hood  of the pylorus.   The question is one which cannot be  decided
by cruel experiments, unless  it can be  shown in several  instances
that vomiting can take  place under conditions which render the ab-
dominal muscles and  diaphragm  incapable of  acting;  such evidence
would unequivocally demonstrate the activity of the stomach.f  But
the opposite  experiments, such  as the  non-occurrence  of vomiting
when the abdominal  muscles and diaphragm  have been paralyzed,
or its occurrence when an inert bag, as a pig's bladder, has been
substituted for the stomach, the external muscles being  intact (as in
Magendie's noted but most cruel experiment), lead to no conclusion,
for,  in  the  one case, the  violence done so  impairs the conditions
necessary for the act (both nervous and muscular) that it cannot be
expected to take place ; and in the other, the substitution of the inert
bag, and the section of the oesophagus, are favourable to the escape
of fluids from the former and through the latter, under  the slightest
pressure.
   The nervous changes which take place in the  act of vomiting are
of the most interesting  kind.  It must be borne in mind that  this
act may take  place—1,  from the introduction of certain substances
into the stomach, some  of which, as bile, mustard, common salt, not
becoming absorbed, must act simply by the impression they make on
the mucous membrane ;  2, by the introduction of emetics, as tartar
emetic, into the blood, or by the presence of  certain morbid poisons

  * See Anderson, Lond. and Edin. Monthly Journal, 1844. In this paper, Dr. Ander-
son has given a complete refutation of Dr. Marshall Hall's supposition that the dia-
phragm is inactive in vomiting.
  + M. L'Epione records, in the Bulletin de l'Academie de Medecine, a case in point.
A man's abdomen was torn open by a horn, and the stomach wholly protruded.  For
half an hour it was seen  repeatedly and forcibly contracting  itself, till, by its own
efforts, it expelled all its contents except the gases.—See Paget's Report for 1845. 
566
DIGESTION.
in that fluid;  3, by mental emotion, as  that excited by the sight of
a disgusting object; 4, by irritation at the base of the brain. Vomit-
ing may be caused, therefore, either  by the direct application of a
stimulus to the gastric surface, or by the disturbance of some part of
the brain through the presence of particular substances in the blood,
that is, by causes operating from  periphery to centre, or by causes
acting directly on the centre itself.   Either the disturbing cause,
as tartar emetic in the blood, affects the medulla oblongata, in which
are implanted the vagi nerves ; or some of the fibres of these nerves
propagate to  the centre the effects of the peripheral irritation at the
gastric mucous membrane.  When the medulla oblongata is thrown
into excitement by any of the causes above mentioned, certain motor
nerves implanted  in it are stimulated to action,  and the abdominal
muscles, the diaphragm,  and the  muscles  of the  larynx as well as
the muscular fibres of the stomach and  oesophagus, are thrown into
that combined action which is essential to the production of active
vomiting.
   When vomiting is the  result of a peripheral stimulation, it affords
a remarkable example of a reflex or  physical  nervous action of the
most complex kind, in which, from the excitation of a few sentient
nerves,  the  nervous force is made to radiate  upon several muscles
and to excite to simultaneous and combined action some which usu-
ally antagonize each other, and are, therefore,  never, excepting in
this act, in the same condition at the same time.  We allude to the
abdominal muscles and  the  diaphragm ; the  former  as  muscles of
expiration being the habitual antagonists of the  latter, which is the
great muscle of inspiration.   In short, the excitation of the nervous
centre, which is sufficient to cause vomiting, gives rise to a forcible
act of respiration, in which the  act  of expiration is  so  powerfully
opposed by  the contracted state of the constrictors  of  the larynx,
the  diaphragm also remaining in strong contraction,  that the main
force of the expiratory muscles i^ directed to  compress the stomach
against the latter muscle.

   On the subjects of this chapter, see the various works on Anatomy, and the principal
systems of Physiology previously referred to : GEuvres de Spallanzani; Tiedemann et
Gmelin sur la Digestion; Hunter's Animal GEconomy, by Owen; Eberle, Physiologie
der Verdauung, 1834; Simon's Chemistry, by Day; Dumas, Traite de Chimie, torn.
viii. (1846); Beaumont on Digestion; Blondlot sur la Digestion ;  Dr. Kirkes's excel-
lent  Manual of Physiology; Bouchardat and Sandras, Cdinptes  Rendus for 1844;
Bernard and Barreswil, Comptes Rendus, 1844; Dr. R. D. Thompson. Lond. Med. Gaz.
1845. 
THE INTESTINAL CANAL.
567
                       CHAPTER  XXV.

OF INTESTINAL DIGESTION.--ANATOMY OF  THE INTESTINAL CANAL IN
  MAN  AND VERTEBRATA.—THE MUCOUS  MEMBRANE  OF THE INTES-
  TINE.--ITS  FOLDS AND VILLI.—ITS GLANDS.—DIGESTION IN THE
  SMALL INTESTINE.—FLUIDS POURED INTO THE SMALL INTESTINE.—
  THE PANCREATIC FLUID.—THE BILE.—THEIR INFLUENCE.—DIGES-
  TION  IN THE LARGE INTESTINE.—DEFECATION.

  Anatomy of the Intestinal Canal.—The  intestinal  canal com-
mences  at the pylorus and  terminates at  the anus.   It  exhibits  a
very obvious subdivision into  two portions :  a narrower  and much
longer portion, disposed in numerous coils or  convolutions,  which is
called the small intestine (intestinum tenue) ; and a much wider but
shorter portion, the large intestine (intestinum crassum).  The length
of the whole intestinal canal in the adult is between thirty and forty
feet, or about six times that of the body: the small intestine forms
five-sixths of this.
  There is a very distinct natural demarcation  between these two
portions of the intestinal  canal; the large intestine  commences by
a dilated cul-de-sac, which communicates  on  its inner side with the
small intestine.   This portion, which is the widest part of the large
intestine,  is lodged in the right  iliac fossa; it constitutes the com-
mencement or the head of the colon, and as it forms a blind  extrem-
ity  or cul-de-sac  beyond  the  junction of the small  intestine  with
it, it is named caput csecum coli, or  commonly caecum.  Connected
with it is a remarkable appendix, which proceeds from its inner and
posterior part, and hangs down into  the pelvis in  a slightly curved
form, which gives it the appearance  of a  worm (lumbricus),  and re-
ceiving support from a small fold of  peritoneum.   This is called the
appendix  cseci vermiformis.   It is a  small process from the caecum,
hollow, cylindrical, in  size  rather larger  than a  goose-quill, about
three inches long, and  ending in a blind extremity which lies free in
the  pelvis, but^ having a free communication with  the  caecum where
it is attached to that intestine.  The large intestine commencing at
this part ascends  from  the right iliac fossa, through the right lumbar
region, as high as the concave surface of the liver ;  this forms the
right or ascending colon;  at the liver it turns to the left and passes,
in an arched form, across the abdomen from  the right  to  the  left
hypochondrium, thus forming  the transverse colon, or  the arch of the
colon ;  it then  turns downward, passes  through the left lumbar re-
gion to the left iliac fossa ;  this portion, which is straight, or nearly
so, is the  left or descending colon.   In the left iliac fossa the intes-
tine becomes somewhat curved, and is rather loosely attached to the
wall of  the pelvis ; its curve  resembles the letter S  ; this  portion,
terminates in  the  pelvis, and is named  the  sigmoid flexure of the 
568                        DIGESTION.
colon; lastly, this becomes  continuous with  the  pelvic  or terminal
portion of the intestine, which, although far from being  straight, is
designated intestinum rectum, or commonly the rectum.   This opens
externally at the  anus, its mucous membrane becoming continuous
with the skin at that orifice.
  The small intestine is arranged in many convolutions, and, with
the exception of its upper portion, the duodenum, it is quite loose in
the cavity of the abdomen, and even  in that of the pelvis, occupying
the  central part  of those  cavities.   The large intestine or colon
embraces it on the right, above, and  on the left.   Three portions of
the  small  intestine have  always been  recognized  by anatomists,
which,  although   not distinguished  by any well-marked external
boundaries, exhibit in their mucous membrane features (to be pointed
out  hereafter) which form their most appropriate means of distinc-
tion.  The upper portion is sufficiently distinct from the rest by its
dilated form, its horseshoe  curve, and by being  closely fixed to the
spine,  in the greatest part of its extent,  by peritoneum.  This is the
duodenum : it forms about the first twelve inches of the small intes-
tine.
  The middle portion of the small intestine is ihe*jejunum, and the
terminal portion is the ileum.   These have no external mark to dis-
tinguish the one  from  the  other.  The jejunum is wider  than the
ileum,  and its coats are  thicker ; the intestine tapers as it approaches
the caecum.
  The whole intestinal  tube is more  or  less  completely7  covered by
the serous membrane of the abdomen, the peritoneum.  The duode-
num above and the rectum below are least covered by it; the rest is
almost entirely enveloped, a small portion being left uncovered where
the bloodvessels enter the intestine, and where the peritoneum passes
to the  abdominal wall.   Each portion of intestine is  attached to the
abdominal wall by a process of peritoneum, the  duodenum and the
rectum very closely, the rest more or less  loosely.   The process of
peritoneum  which connects the small intestine  to the  spine is the
mesentery,  and each portion of the  large intestine is  connected  to
the corresponding region of the abdominal wall by a process of peri-
toneum, which  is  designated  by prefixing the word  meso (psao; me-
dius) to the name  of the particular portion of intestine: thus meso-
csecum is the process which connects the caecum to  the iliac fossa ;
mesocolon,  right, transverse, left, is that which belongs respectively
to the  three portions of the colon ; and the  mesorectum connects the
rectum to the concavity of  the sacrum.
  Attached to the colon are small processes of peritoneum, contain-
ing fat, and called appendices epiploicse, from their  resemblance to
the epiploon, or great omentum, which descends from the great curva-
ture of the stomach  and from  the transverse colon, like a curtain, in
front of the small intestine.

  77te Intestinal Canal in Vertebrata.—The intestinal canal  is disposed in  the four
vertebrate classes much on the same plan as in the human subject:—
  in Fishes, the intestinal canal exhibits for the most part a very simple conformation.
In many fishes it passes quite straight, or very nearly so, through the body: when it 
THE INTESTINAL CANAL IN  VERTEBRATA.           569
 does exhibit convolutions they are few and short, and rarely to any great extent.   A
 pyloric valve is generally present, separating the intestine from the stomach; imme-
 diately succeeding to this valve, the intestine generally experiences a dilatation, whence
 it  gradually contracts to its terminal portion,  which again becomes dilated.  This
 portion corresponds to the large intestine, and commonly a valvular fold of the mucous
 membrane is present at its union with the preceding portion; it terminates in a cloaca
 common to it with the genital and urinary organs.   In some fishes, however, no dila-
 tation  is found, nor any external distinction between the stomach and intestine, and
 the canal  from the oesophagus to the anus is of  uniform caliber.   Immediately below
 the pyloris we very commonly find a series of tubular prolongations from the intestine,
 terminating in blind extremities.   These constitute the appendices pylorica, or pyloric
 follicles, which most comparative anatomists consider to supply the place of a paren-
 chymatous pancreas.   These appendices vary considerably in both  number and size.
 In pleuronectes flesus there are only two very short ones, placed  opposite each other  at
 different sides of the intestine ;* in ammodytes tobianus there is only one ; in Blennius and
 Gasterosteus there are only two, so small that Wagner compares  them to the follicles
 of the  proventriculus of birds;  there are from ten to thirty in many species  of Clupea
 and Salmo, and in  the genera Gadus and Scomber (the common mackerel, for example),
 there are  as many as two hundred, f  On the  other hand, they are  entirely absent
 in  many fishes. _ Again, in  some they are simple, in  others they become subdivided  or
 branched  at their blind extremities, and  in others still these branches  undergo subdi-
 vision,  and the resemblance to the glandular formation is enhanced by the fact that
 these branchings are connected by means of cellular membrane and bloodvessels.
   In Reptiles, the intestinal canal differs from that in fishes chiefly in  having under-
 gone a slight increase of development.   The divfsion into large and small intestine is
 distinct throughout the class, and often  an ileo-caecal valve is present.   In Ophidia,
 the small intestine presents numerous short convolutions at acute angles;  the large
 intestine ends in a cloaca.   The intestinal canal is longest in  the Chelonia, and next
 to  them  in the  Crocodiles.  In the Chelonia,  the  line  of  distinction between the
 large and  small intestine is not so distinct as in  the rest, and the muscular coat is
 remarkable for its  great thickness.  The tortoises have a short, wide, and cylindrical
 caecum, which is continuous without interruption with the large intestine: they have
 also a circular ileo-caecal valve. J   The great thickness of the muscular coat, and the
 almost  total obliteration of  the canal during its contracted state, constitute one of the
 most striking peculiarities of the intestine in Chelonian reptiles.  In  Batrachia, the
 difference  between  large and small intestine is very distinct, being chiefly indicated by
 difference  of caliber, and in frogs  a circular ileo-caecal valve;  in the  toad, however,
 there is a small caecum, without an ileo-caecal valve.  In most of the Saurian reptiles there
 is a caecum, according to Meckel, and generally  an ileo-caecal valve:  in the  Crocodile
 the valve is present but the caecum absent.
   In Birds, the intestinal canal, although longer than either in fishes or reptiles, yet
 retains  considerable simplicity of form.  It presents much variety in length and in the
 number of its convolutions,  according to the food and habits of  the bird.   The duode-
 num, which immediately follows the gizzard, has  always the form of a long fold, which
 contains the pancreas in it.   The small intestine, more or less folded in different orders,
 terminates in  a short  and somewhat wide  large intestine, at the commencement  of
 which are  two caeca, one on each side of the intestine.  These caeca vary considerably
 in length from almost simple papillae form offsets, as in the Soland goose, \ to  processes
 three feet  in length, as in the grouse.   It sometimes occurs that  there is only one
 caecum.  The large intestine is short and straight, and is continued from the termina-
 tion of  the small intestine, without fold, to the cloaca.  There  is connected with the
 small intestine an appendage,  the remains of the duct of communication between the
 yolk-bag and intestine in the chick.  In some  birds  this appendage, which  is said to
 be devoid of a muscular tunic, is as large or larger than the caeca.
  So much diversity exists in the form, length, and arrangement of the intestinal canal
 in the different orders of Mammalia, that it will be necessary briefly to state its pecu-
 liarities in  each order.
  In Carnivora, we find examples in which the intestinal canal is remarkably short in
 relation to  the length of the body.  The small intestine has but few and simple con-
volutions;  it opens into  a short caecum (convoluted, however, in the dogs), which
 scarcely differs in width from the  rest of the large intestine.   The proportion in the
length of the intestinal canal to that of the body varies from,  according  to Meckel, five

           * Figured in Carus's Anat. Comp. pi. ix. Fig. 20.
           t R. Wagner, Vergleichend. Anatom.
           % Meckel.                   %  Sir E. Home's Comp. Anat. pi.  civ.
         37 
570
DIGESTION.
to one, as in the cats and dogs; to eight to one, and nine to one, as in the hyena and
bear; or to fifteen to one, as ascertained by Meckel, in Phoca  vitalina.  The large in-
testine is shorter and wider than the small; it is cylindrical in form, not sacculated, as
in man and many others.
   In Insectivora, the intestinal canal is short, and without caecum, the diameter being
pretty uniform throughout.  In Sorex, according to Meckel, its length is to that of the
body as three to one, in the hedgehog as six to one; in a mole examined by ourselves,
which measured from snout to tail seven inches, the intestinal canal, from pylorus to
anus, measured four feet three inches.
   In the Cheiroptera, a very marked distinction exists in the form of the intestinal canal
between the frugivorous  and insectivorous genera.  In the former, as in Pteropus, it
presents numerous coils, and is in length seven times that  of the body—the caecum is
absent.   In the latter, the canal is extremely short, bearing to the length of the body
the proportion of  two or  three to one  as in Vespertilio noctula.   Much variety exists
as regards both the form and length of  the intestinal canal in  the Edentata.  The dis-
tinction between large and small intestine is not evident in many of the genera.   In the
Manis and Bradypus there is no trace of a caecum ;  on the other hand, the two-toed
ant-eater  (Myrmecophaga didactyld) has, according to Daubenton and Meckel, two small
and narrow caecal  appendages resembling those  of birds, situated at the confines of
the two portions of the intestine; the orifices of these caeca are so small that the fecal
matter cannot find its way into them.  Mr. Owen has preserved, in the Hunterian col-
lection, a specimen  from the weazel-headed armadillo  (Dasypus mustelinus), of two
similar caeca between which the ileum terminates.   The terminal aperture of this in-
testine is  of a slit-like  form, and from its position between  the caeca it admits of being
effectually closed by the lateral pressure of the contents of the caeca.*
   Great length and wide caliber are the characteristics  of  the intestinal canal in Ru-
minants, Solipeds, and Pachydermata.  In the  sheep, which belongs  to the ruminant
order, the intestine is in length thirty times that of the body, and in the horse, accord-
ing to a measurement made by us,  the  intestinal  canal was  eighty-seven and a half
feet in length.  There are numerous convolutions of the small intestines in each of these
orders, and a large  capacious caecum, from which the wide  and convoluted colon is
continued.   In Ruminants, neither the caecum nor the colon is sacculated  by longitud-
inal bands, whilst both the Solipeds and Pachydermata exhibit the sacculated character in
a very marked degree, and the bands of longitudinal muscular  fibres are very highly
developed, extending from the blind extremity of the caecum to the rectum.  There
is no ileo-caecal valve,  properly so called, in these orders, but the passage from  the
ileum to the caecum  (a foot and a half long in the  horse) is very much contracted, and
its inner membrane thrown into six or eight thick longitudinal folds, which are closely
applied to each other and keep the canal closed.   The caecum in each of the orders
is very capacious;  in the Ruminants, the capacity of this portion of intestine some-
what exceeds that of the  fourth stomach, according to Meckel.  In the Solipeds, the
caecum is still more  capacious.   Meckel  asserts  that it is capable of containing
more than three times as much liquid as the stomach.   In Pachydermata, the caecum
is shorter and wider than in the other orders; it is, according to  Meckel, less capacious
than the stomach.f
   The Rodentia have,  in general, a very long  and convoluted intestinal  canal.  The
small intestine has a mesentery of  considerable length ; its caliber is small and pretty
uniform throughout, being however largest superiorly.  In most of the Rodent genera
the caecum is of very great size, and in some it occupies a large portion  of the abdo-
minal cavity;, in the omnivorous rodents, however, as the rat,  the caecum is  of small
dimensions.  The whole large intestine  is cellulated, the cells being formed by longi-
tudinal fibres and circular constricting  ones.
   In the  genus Myoxus (dormouse), the caecum is entirely absent, the only exception,
according to Meckel, to the presence of this cavity in the  rodent order.
   In the Marmpiate animals, the distinction between large and small intestine is clearly
marked by the presence of a caecum.  The small intestine is long,  and  in some very
wide; the caecum is of moderate length and width, its capacity being much below that
 of the stomach.
   The chief peculiarity of the intestinal canal, in the Monotremata, is  to be found at its
 inferior extremity, where a cloaca exists common  to the rectum with the  urino-genital
 organs.   A small caecum separates the long and small intestine.

   * Catalogue ofthe Hunterian Museum, vol. i. pp. 219, 729, A.
   t See Sir E. Home's plates of the cseca of several mammiferous animals,  plates cxiii. et
 seq. vol. ii. 
THE INTESTINAL CANAL IN VERTEBRATA.           571
   The Cetaceous mammalia have an intestinal canal of considerable length.  The length
 of the canal in the zoophagous  cetacea is to  that of the body as eleven or twelve to
 one. (Meckel.)  According to Cuvier, the proper whales have no division between large
 and small intestine, and consequently no caecum.  This is the case in the porpoise.   In
 the Balcena Rostrata, however, according to Hunter, and in all the Balcence, according
 to Cuvier, a small caecum, not unlike that of carnivora, exists.   In  the herbivorous
 cetacea, the intestinal canal is of proportionally greater length  than in the zoophagous
 cetacea.  In the dugong, according to Meckel, its length exceeds forty times, and in
 the lamantin of  Kamtschatka, twenty times that of the body.
   The Quadrwnana.   The length of the intestinal canal in this large order of Mammi-
 fers presents very remarkable variety, which is the more curious as the nature of the
 food is, with few exceptions, similar in the various genera.  The proportion of the
 length of the intestinal canal to that of the body is in some as eight  to one, whilst in
 others it is only as three to one.*  The division into two portions is effected in the
 same manner as in the human subject, and the general arrangement of both small and
 large intestine is very similar to those of man.   A caecum exists in all the genera, but
 presents considerable variety as to length; an increased length  of this portion of intes-
 tine along with  a larger development of the splenic extremity of the stomach being
 employed in some cases to compensate for a deficiency in the length  of the intestinal
 canal. _  The orangs and gibbons have the peculiarity, which they alone possess in com-
 mon with man, of a process from the caecum, some  inches in length,  denominated the
 vermiform appendix.
   From the preceding brief review of the anatomical characters of the intestinal canal
 in the vertebrate classes, we gather, that this portioti of the digestive tube diminishes
 in complexity as we descend from mammalia to fishes; that a short and simple intestinal
 canal is generally coexistent with a diet of animal food;  and, on the other hand, that
 a diet of vegetable food, or a conjoint animal and vegetable diet requires greater length
 and greater complexity in the form and structure of the intestines.  In estimating the
 length of the intestinal canal we must not confine our examination to a mere external
 measurement, as we should thereby be led to a very erroneous conclusion.  Deficiency
 in length, as measured on the exterior of the intestine, may be supplied by increased
 width—by a more highly-developed state of the villi of the mucous  membrane—by
 numerous folds of that membrane; and the energy of the action of the mucous mem-
 brane on the contents of the intestine, may be augmented by the greater number and
 size of the glands which pour out their secretions on its surface.   It may further be
 observed, that as the several portions, whether of small or large intestine, have very
 definite characters as  regards the mucous  membrane, we can readily determine the
 relative length and development of each portion, and thus deduce its proper degree  of
 importance  in intestinal digestion.  But upon these points it is much to be regretted
 that we  are greatly in want of precise information;  we are persuaded that nothing
 would tend more to the correct determination of the office performed  by each portion
 of the intestinal canal  than a series of careful  observations with special reference to
 anatomical characters on the intestines of  a great number of animals.
   Much importance is  attached by Physiologists, and apparently with good reason, to
 the size and form of the caecum.  It is  difficult, however, and  in the  present state of
 our  knowledge impossible  to determine the law which influences its development.
 Nevertheless, it may be stated that there appears to be a direct relation between this
 development of the intestine and the  hardness of digestion of  the food: in some in-
 stances we find that a large caecum compensates for a less capacious stomach, as in the
 Solipeds, and in these cases there exists even a striking similarity in the forms of those
 two organs.   A large caecum, then, belongs to the herbivorous classes, as a large sto-
 mach does, and a small caecum would, on the other hand, indicate a diet of animal food.
 Anatomy would seem to point to the conclusion that the function of the caecum is not
 dissimilar to that of the stomach, and that in it  substances hard of digestion are sub-
jected a second time to  a reducing action resembling  that of the stomach.  Perhaps
 the anomaly which we have noticed in the dormouse, in the absence of a caecum, may
 be explained on the supposition that this accessory digestive cavity was rendered un-
 necessary in consequence of the existence of the glandular pouch at the cardiac orifice
 of the stomach in that animal.


   The subdivision of the intestinal canal, in  man, into the  small and
large intestine, by the difference in caliber of those two portions of

         * Vide a table in Meckel's Anat. Comp. (French ed.) torn. viii. p. 778. 
572
DIGESTION.
that tube,  as well  as  by the existence of  an ileo-csecal valve, has
already been described.   There are other characteristics, however,
of  anatomical  constitution which  likewise  sufficiently distinguish
them.   The whole  of the intestinal  tube  is  composed of  certain
tunics, which, enumerated from  within  outwards, are as follows: 1,
the mucous membrane;  2, the  submucous  tissue;  3, the  muscular
coat; 4, the serous coat, which is connected to the  tunic last named
by  a thin layer of very delicate areolar tissue.   Of these tunics, the
mucous membrane,  the muscular coat, and the serous coat, exhibit,
on the whole, very  distinctive characters in the two divisions of the
intestine.
  The mucous membrane continuous with  that of the stomach ex-
hibits  very characteristic features  in  the  different portions of the
intestine.  We shall reserve the  description of it  until we  have
spoken of  the other tunics.
  The submucous tunic is a layer of very fine areolar tissue, which
connects the mucous to the  muscular  coat;  it is entirely devoid of
fat, and  presents the  same characters  throughout the whole intes-
tinal canal.  Placed immediately underneath the mucous membrane,
it constitutes  the medium, through which the various  sanguiferous
and other vessels and  the nerves pass to that membrane.
  The muscular coat of the small intestine consists of two layers or
planes, which differ from each other  as  regards  the direction of
their fibres.  The external plane is composed of longitudinal fibres,
continuous superiorly with the  longitudinal fibres  of the  stomach;
they form  a continuous tunic surrounding the intestine, and extend-
ing from the  pylorus  to the caecum.   C. B.  Albinus* states that
they exist  only as a band a finger-breadth broad, and corresponding
to the concave border of the intestine, along which the mesentery is
attached, and to  this he attributes the concavity which the inflated
intestine presents towards the mesentery.   We have  no doubt, how-
ever, that the longitudinal fibres form a continuous tunic around the
intestine, though they are strongest along the line  of attachment of
the mesentery, and are  very apparent in  that situation, at times
when they are indistinct elsewhere.   The  circular fibres  are much
more distinct than the longitudinal; the direction of which they cut
at right angles.  They surround the intestine in a circular manner,
not spirally, as some anatomists have asserted.
   The muscular  tunic of the large intestine is likewise disposed in
two layers of fibres.   The  external, however, does not, as in the
small  intestine, form  a uniform  layer round the intestine, but is
developed chiefly in  three bands, about half an  inch wide, with a
few intervening  longitudinal fibres.  These bands commence at the
root of the vermiform appendix of the caecum, and  extend in this
form to  the rectum, where they become expanded, and form a  con-
tinuous tunic over  the whole intestine.   The longitudinal bands are
shorter than the intestine ; the effect of this is, to produce a puck-

  * Specimen Anatomicum exhibens novam tenuium Hominis  Intestinorum Descrip-
tionem.  Lugd. Bat. 1724. 
THE INTESTINAL MUCOUS MEMBRANE.
573
ering of all its coats at  certain intervals  throughout the  whole
length of the colon.  At these  points the colon appears  to be con-
stricted, as  by a shorter bundle of  circular fibres, and its mucous
membrane  projects  into  the  interior, forming  large folds.   These
folds  separate sacculated portions of the intestine, which are the
cells of the  colon,  and the convex bulgings seen on the exterior of
the inflated large intestine are the walls of these cells.   The circu-
lar fibres are arranged in the  same manner as in the small intestine,
being spread uniformly over the surface of the intestine.
   Of the Mucous  Membrane of the  Intestinal Canal.—The intesti-
nal mucous membrane so far resembles that of  the stomach, that it
is of  the compound  variety (see ante, p.  546);  and its thickness is
caused by the involution of multitudes of tubes, which  terminate in
blind closed extremities, and rest vertically upon the submucous tis-
sue.   Most of the tubes remain undivided from their open to their
closed extremities, some are bifurcated towards  the blind extremity.
Each tube  has a separate orifice on the free surface of the mucous
membrane,  except in the upper part of the  duodenum, and  in the
csecum, where they open by sets of three or more  on the floors  of
shallcuv cells, as in the stomach.  These tubes are commonly called
Lieberkuhn's follicles ; but they were first described by Brunn, or
Brunner, who has given a good delineation of them ; and their real
nature was  not known to Lieberkiihn, who regarded them as muscles.
   In examining thin vertical sections of the mucous membrane from
any part of the intestine, we see
these  tubes closely set  parallel
to each other; they are straight,
and,  excepting that  here and
there one is bifurcated, they ex-
hibit no irregularity or  bulging
of their walls, and are pretty
uniform in  diameter throughout
their length (Fig. 157).  All the
elements of  the  mucous  mem-
brane contribute to their forma-
tion ;  the  basement-membrane,
the epithelium, and the submu-
cous tissue, which  is sparingly
interposed between  them.
   The epithelium is columnar or
subcolumnar; the cells  are dis-
posed in a single layer, with one
end adherent to  the basement-
membrane.   The  cast-off parti-
cles  often fill each  tube as mu-^
cus, which  escapes at the orifice, on the  free surface of  the mucous
membrane.   These tubes are shorter in the large than in the small
intestine ;  and as  the  thickness of the mucous membrane is de-
 pendent on their length, we find it less  thick in the former than in
 Section of the mucous membrane of the small
intestine in the dog. showiug Liebcrkuliu's follicles
and villi.
 a. Villi.  6. Lieberkuhn's  follicles, c. Other
coats of the intestine. 
574
DIGESTION.
the latter intestine.   The mucous membrane is  thickest where the
tubes are most developed, namely, in the jejunum.
   Lieberkuhn's follicles are doubtless secreting agents, resembling
                           in that respect the tubes of the stomach.
                           Probably their office,  in reference to the
                           intestinal contents, is the same  through-
                           out  the whole  intestinal tube, as  they
                           present everywhere so much uniformity
                           of  arrangement  and structure, and as
                           each  portion  of  the  intestine  possesses
                           other and peculiar glands.   As  yet, how-
                           ever, nothing is known  respecting the
                           nature of the mucus which is secreted by
                           them.
                             By the  infinite  multitude of minute
                           and microscopic  involutions which form
                           Lieberkuhn's follicles, the extent of sur-
                           face  of  the mucous  membrane is  enor-
                           mously increased.  It is still further en-
                           larged by the existence  of various  folds
                           and  processes,  which project  into the
                           cavity of the intestine ;  these  we  shall
                           now proceed to describe.
                              Of the  Valvuloe  Conniventes,  Folds,
                           and  Villi.—The  mucous  membrane of
                           the  small  intestine  exhibits  numerous
                           folds, which,  small, irregular, and resem-
                           bling the  rugae of the  stomach  in the
                           superior third of the duodenum, assume
a much more definite form, and are much more highly developed in
the remaining portions of the  small intestine, but especially in the
jejunum.
   The  irregular  foldings of the upper portion of the duodenum
very soon  exhibit the  tendency to assume  a transverse  direction
with  reference to  the axis of the intestine.  In  the middle and
inferior portions of  the  duodenum  we find  numerous transverse
plaitings or folds, from one-eighth to a quarter of an inch  in depth.
These are simple folds of  the compound mucous membrane, including
a process of the submucous  areolar tissue : they are  called valvulce
conniventes, from  their valvular form, and  from their  movements
under  water resembling  the  flapping  of valves, or  the winking
motion of the eyelids.   Each fold passes  round the intestine for
about  three-fourths  or five-sixths  of its  circumference, gradually
diminishing  in depth  towards  each extremity, but sometimes bifur-
cating  and coalescing  by one  or  both subdivisions,  with  the  fold
above  and below.   In the lowest part of the duodenum, and  in the
jejunum, the valvulse conniventes acquire their highest development.
Here  they lie very close  together, and  many of them  pass  nearly
round the intestine ; they are  deeper,  also,  here  than elsewhere,
Fig. 158.
 A. Transverse section of Lieberkuhn's
tubes or follicles, showing the basement-
membrane and subcolumnar epithelium
of their walls, with the areolar tissue
which connects the tubes, a. Basement-
membrane and epithelium, constituting
the wall  of the tube.  6. Cavity or
lumen of the tube.  Magnified 200 dia-
meters.
 b. A single Lieberkuhn's tube, highly
magnified. A happy accidental section
in the oblique direction has served to
display very distinctly the form and
mode of packing of the epithelial parti-
cles, the cavity of the tube, and the
mosaic pavement of its exterior, a.
Basement-membrane, c. Internal sur-
face of the wall of the tube.  Magnified
200 diameters. 
               THE INTESTINAL MUCOUS MEMBRANE.           575

 being sometimes half or three-fourths of an inch in depth.  In the
 ileum they gradually diminish  in length and in depth, frequently
 not  passing round more  than one-half the circumference  of the
 intestine, and measuring not  more than one-fourth or one-eighth of
 an inch in depth;  and in the lowest  part of the ileum they almost
 entirely disappear.
 ^  It is remarkable  that these folds  are peculiar to the human sub-
 ject.  No other animal, so far as we know, exhibits any arrange-
 ment of transverse folds of the intestinal mucous membrane resem-
 bling them.
   The folds of  mucous membrane  in the  large intestine are the
 partitions between  the  cells  of the colon; they exhibit much uni-
 formity of shape, although they vary very much  in size ; they are
 least developed in the sigmoid flexure.
   At the junction of the ileum with the caecum, there are two  folds
 which bound the  slit-like aperture of communication between the
 small and the large intestine.   These are the  segments of the ileo-
 caecal valve.   The aperture is a simple slit, which passes nearly hori-
 zontally from before  backwards, and is bounded on all  sides by
 mucous membrane.   Its lower border is formed by the free edge of
 a deep  semilunar  fold of mucous  membrane, inclosing submucous
 tissue, and  a few  circular muscular  fibres; and another fold,  of
 much less depth, but of  similar shape  and constitution, form its
 upper lip.  This latter fold has a more horizontal  direction than the
 former, which is nearly vertical.  The folds coalesce in front of and
 behind the aperture, and form small bands, called frsena, and which
 follow for a short distance the course and direction of  the segments
 of the valve.  The free margins of these two segments come in ap-
 position in the distended state of the caecum, and close the aperture,
 or at least diminish  and  constrict it  so much as, in general, to pre-
 vent the reflux of any but liquid or much-subdivided matters into the
 small intestine.
   In the rectum, there  are  folds of  various sizes and  directions,
 which are most  numerous in the empty state of the gut, and are
 effaced  by its distension.  The late  Mr.  Houston, of Dublin, has
 described certain permanent  folds, or  valves, of  semilunar shape,
 which he demonstrated  by moderately distending the rectum  with
 alcohol, which, at the same time, hardens its tunics,  and thus dis-
 plays their condition in the state of repletion.  Three is the average
 number; but sometimes  a  fourth is found, and at other  times  only
 two are present.  The largest and most constant valve is situated
 opposite the base of the bladder, about three inches from  the anus.
 The fold next in  frequency is placed at the upper end of the rectum ;
 and the third  occupies a position midway between these.   When a
 fourth is present, it  is situated about  one inch above the anus.   In
 the empty state  of  the  intestine, these folds overlap each  other,
 as Mr.  Houston remarks,  so  effectually as to require considerable
manoeuvring to  conduct  a  bougie or the finger along  the cavity of
the intestine.   Their  use  seems to  be "to  support the weight of 
576
DIGESTION.
 fecal  matter, and prevent its urging towards the  anus, where its
 presence always excites a sensation demanding its discharge."*
   Of the  Villi.—Villi are minute processes  of  the mucous mem-
 brane of the small intestine, to which they are exclusively  confined
 (Fig. 159).   They project from the free surface of the mucous mem-
 brane into the cavity of the intestines, and seem  admirably adapted
 to become implanted, like  so many little roots, in  any semifluid or
 fluid material which  may fill the bowel.   Villi are first  found in the
 duodenum, where they appear to  develop themselves as elongations
 of the partitions between the cells  into  which Lieberkuhn's tubes
 open.   In the lower half of the duodenum, and the rest of the small
 intestines, they are very numerous, and give to the surface of the
 mucous membrane an appearance  like that produced by the pile of
 velvet.   They are continued down  to the  ileo-caecal aperture,  and
 cease  abruptly at its  margin, covering  the  surface of the valve-
 segments next the ileum, but being wanting on the caecal surface.
  A good view of the shape, arrangement,  and number of  the villi
 may be obtained by examining a piece of villous  mucous membrane
fixed under water.  In man, the villi are conical in shape, somewhat
flattened, and measure in length from apex to base from the l-60th
to the l-45th of an inch.   They vary much in shape and size in the
lower  animals : in the dog, cat, and lion they are long and almost
                                          filiform;  in  the sheep
                                          and   rabbit   they   are
                                          small,  flattened,  and  co-
                                          nical ;   in  the   turkey
                                          they are large and lamel-
                                          liform.  Most fishes and
                                          reptiles  are  devoid   of
                                          villi.
                                            In  structure,  a villus
                                         resembles  an   everted
                                         Lieberkuhn's  follicle;—
                                         theNsame  elements exist
                                         in both; basement-mem-
                                         brane,  epithelium, sub-
                                         basement   tissue,  which
                                         occupies, along with ves-
                                         sels and perhaps  nerves,
                                         the interior of the villus.
                                         The  difference between
                                         the  two  structures  is,
                                         that the epithelium is in
                                         the  interior  of the  fol-
                                         licle and  on the exterior
                                         of the villus.
                                            A single layer  of the
                                         columnar epithelium co-
 A. Villi of duodenum of dog, two hours after death, showing
the substance of the villus retracted from the epithelial in-
vestment, like a finger from a glove. The process of digestion
was not going on at the time of the dog's death, as  there was
do food in the stomach nor chyle in the lacteals. Magnified 80
diameters.
 b. From the same part, and same dog, showing the epithe-
lium corrugated, being attached and free at intervals.  Magni-
fied 80 diameters.
* Dub. Hosp. Rep. vol. v. p. 163. 
THE VILLI.                          577
., '.■ .'V >
F'  V /r,J 1
-3
 vers each villus (Fig 159).   The particles adhere by their sharp ex-
 tremities  to the  basement-membrane, and  their  bases, packed to-
 gether, present on the surface an appearance of a pavement.
   The basement-membrane is readily seen when  the epithelial layer
 falls off, which it is apt
 to  do  during  the diges-
 tive  process (Fig.  160).
 It  is a single layer of
 homogeneous membrane,
 beneath which, or in the
 cavity of the  villus, are
 seen,  in  well - injected
 specimens,  the bloodves-
 sels of  the  villus.
   Each villus is provided
 with a plexus  of  capilla-
 ries.   A single artery en-
 ters  its base,  and, pass-
 ing  up  its  centre, forth-
 with  breaks  up  into  a
 capillary  plexus,  which
 is seen at  all points of
 the surface  of the villus,
 immediately beneath the
 basement - membrane. —
From this arise at  vari-
 ous  points small veins, which pass  out of  the villus in one or more
 trunks (Fig. 162).
  The  cavity of  the villus also contains one  or  more small  lacteals,
in which originates  the proper lacteal plexus of the intestine.   The
villi are seen white with chyle, during the absorption of  that fluid,
and the chyle  may be fixed in them by coagulation, if the membrane

                                Fig. 161.
         A.                      B.
 a. From the same part of another dog, fed 2J^ hours before
death, showing the columnar epithelium stripped off, and the
cellular substance of the villus covered merely by basement-
membrane. Magnified 200 diameters, a. Basement-membrane,
slightly raised, b.  Cellular substance of the villus, disposed
somewhat in columns.
 B. From the same part and same dog, showing villus de-
nuded of epithelium, and the basement-membrane raised in a
bulla by the endosmosis of water, in which it was immersed.
Magnified  200 diameters,  a. Basement-membrane,  b. Cellu-
lar substance of the villus.
  Capillary plexus of the villi of the human small intestine, as seen on the surface, after a successful
injection, magnified 50 diam. 
578                         DIGESTION.
is  promptly immersed in alcohol.  Respecting the manner in which
these vessels are disposed in the villus, however, nothing certain is
known.  Some  have described a network of these vessels  extending
to the extremity of the villus.   The investigation is one of the most
difficult in minute anatomy, and is highly important as bearing upon
the mechanism of the absorption of chyle.
   Nothing whatever is known of the relation of the nerves to the
villi.   The tissue which occupies the cavity of the villus,  and which
supports the capillary plexus, and whatever other vessels may exist
in it, is a soft, imperfectly formed areolar tissue,  containing nuclei
and granules, and resembling somewhat the tissue contained in the
gustatory papillae of the  tongue.   That portion  of it which corre-
sponds to the free extremity of the villus differs  from the rest; it
exhibits a vesicular  structure, and resembles  very minute fat vesi-
cles, filled by  some  transparent fluid.   The tissue  which occupies
the  remainder  of the villus seems  to  consist chiefly of nuclei or
granules,  some  of  which  present an indistinct  arrangement in
columns, which are parallel  to  the  axis of the villus.  During the
process of chylification it appears to  be the  seat of some very re-
markable changes connected with the absorption of chyle.
   The function of the villi  appears -evidently to be connected with
absorption, and  specially with the absorption of chyle.   This view
                                    rests    upon    the    following
                                    grounds :   First, that the  villi
                                    exist only in the small  intes-
                                    tine, where the most active ab-
                                    sorption  of  digested matters
                                    evidently goes  on;  and   that
                                    they are most highly developed
                                    and most numerous in that  part
                                    of the  small intestine where
                                    chyle is first formed.  Secondly,
                                    that during the process of  chy-
                                    lification the villi   are turgid
                                    with  blood, and obviously pre-
                                    sent all the appearance of being
                                    the seat of  some  active  vital
                                    process; they are enlarged and
                                    opaque,  apparently  from   a
                                    change  in  the intravillous tis-
                                    sue, and probably also from the
                                    introduction  of some new  mat-
                                    ter into them.  In animals that
                                    have been kept fasting for  some
                                    time  prior  to death, the villi
 look small, and as if shrunken within their epithelial sheaths, which,
 in some  instances, adapt themselves  to the diminished  size  of the
 inclosed  villi,  by becoming  thrown  into  folds  (Fig.  162).   But
 during the digestive process the villi are large and full; the nuclei
 of their  proper tissue are very distinct; the  basement-membrane  is
Fig. 162.
 Vertical section of the coats of the small intestine
of a dog, showing only the commencing portions of
the portal vein and the capillaries.  The injection has
been thrown into the portal vein, but has not pene-
trated to the arteries, a. Vessels of the villi.  6. Those
of Lieberkuhn's tubes, c. Those of the muscular coat. 
THE INTESTINAL GLANDS.
579
Fig. 163.
:'•¥!:
   «tif§s
          J A
           w
          i0

        A.
 A. Epithelium detached, and free in the cavity of
the duodenum, taken, immediately after death, from
a dog fed 2!4 hours before. Ea£h cell is filled with ap-
parently fatty matter, partly granular and partly in
globules. Magnified 600 diameters.
 B. The same, suffered to stay an hour or two under
the microscope, showing the fatty material aggregated
into larger globules, the rest of the cell-structure hav-
ing become indistinct.
B.
here  and  there bulged  by them on the surface, especially towards
the  free  extremities, and the  peculiar vesicular structure at the
apices of the villi is compressed,
or  otherwise  concealed  from
view  or  altered in  character
(Fig. 160). Lastly, the  epithe-
lium seems to adhere much less
closely to  the villi during chyli-
fication than  during fasting;
and  the  epithelial  particles
themselves appear to undergo
some change during this pro-
cess.    This latter change is re-
presented in the  annexed cut
(Fig. 163);  the epithelial par-
ticles appear larger,  their con-
tents  more  distinct,  and con-
sisting of minute fatty  grains
as well as of some small globules.
   Of  the  Glands of the Intestine.—These are, in addition to the
Lieberkuhn's tubes  or  follicles already  described,  and which are
themselves secreting  organs : 1. Brunner's, or the duodenal glands;
2. The solitary glands ;  3. Peyer's glands, or glandulae aggregates.
   Brunner's glands belong properly to the duodenum.   They were
discovered and  described by
J. C. Brunn in 1686.   We find               Fig- 164.
them in the submucous areolar
tissue,  disposed as a more  or
less   thick  layer of whitish
grains,  immediately  beneath
the mucous  membrane.   They
may be compared to the ele-
mentary  grains of  a salivary
gland  spread  out  on  an  ex-
panded surface instead of being
collected  into a  mass.    Near
the  pylorus  they   are  most
numerous,  and   most  closely
set and largest; towards the  termination of the duodenum  they
become much fewer,  smaller, and scattered; and nothing resembling
them is found in any other portion of the intestine.   They are much
more developed in the Herbivora than  the Carnivora ;^ in man, they
are large  and numerous, generally  speaking, but exhibit a good deal
of variety in different subjects, and, in the very old,  they appear to
have wasted and shrunk.
  In  point  of  structure, Brunner's glands resemble precisely the
pancreas.   Their ultimate elements are bunches of vesicles which
contain globular  epithelium,  and  from  which  ducts  arise which
coalesce  and form  larger ducts,  through which the  secretion
 Vertical section of the mucous membrane of the
duodenum in the horse, slightly magnified, showing
v, villi, 6, c, mucous membrane and submucous tissue.
g. Brunner's glands cut vertically, and a little spread
out, showing their lobulated structure.
IS 
580
DIGESTION.
Fie. 165.
 A solitary gland from the
small intestine of the human
subject, magnified.— After
Boehm.
poured into the duodenum.   The exact relation of these ducts to
the tubes of Lieberkuhn is not known.
  Brunner's  glands, no doubt, secrete a  fluid similar, perhaps, in
nature, to the pancreatic fluid, which exercises an  influence  on that
portion of the digestive process which takes place in the duodenum.
Their restriction  to  the upper  portion  of the intestine, and their
mode of arrangement  in an  expanded  form  beneath the  mucous
membrane, establish for them an analogy with the buccal  glands,
which are similarly disposed  beneath the  mucous membrane of the
mouth, and which bear to the salivary glands the same relation as
the duodenal glands do to the pancreas.
                       These  glands, restricted as they are  to the
                    upper portion of the intestine, give a character
                    to  it  of  a  physiological kind,  and  therefore
                    more  definite than   any external  boundary.
                    Accordingly, while the duodenum may properly
                    give its  name to these glands, so the presence
                    and extent of them should denote that  portion
                    of intestine which  may be called duodenum,
                    and define  its limits.
                       The solitary glands are found  in all parts of
                    the intestine,  but  are most  numerous   in the
                   jejunum, in  the  caecum, in  the vermiform
                    appendix, and in the rest of the large intestine.
When filled with  their secretion they are like small grains, about
                                as large  as those of  mustard-seed,
                                placed beneath the  mucous mem-
                                brane  in  the  submucous  tissue,
                                which  cannot in  those situations
                                be inflated; they may be  readily
                                seen by  holding up the intestine
                                against  the  light.   When  empty
                                and collapsed, they are not easily
                                discovered,  and  therefore  are fre-
                                quently overlooked.
                                  One of these glands is a simple
                                vesicle, or sacculus,  of membrane,
                                shaped like an India-rubber bottle,
                                with  a  narrow  extremity  corre-
                                sponding to the  surface  of the
                                mucous membrane, and a rounded
                                obtuse  base, imbedded   in the
                                submucous   tissue.    Its   precise
                                relation  to  the  elements  of the
                                mucous  membrane  cannot be  ex-
                                actly determined; its wall  seems
                                to be  formed of a  structure dis-
                                tinct from the basement  layer  of
                                 that membrane.  It projects among
                                 Lieberkuhn's tubes, and,  in the
Fig. 166.
 A patch of Peyer's glands of the adult human
subject, from the lowest part of the ileum.—After
Boehm. 
THE INTESTINAL GLANDS.                  581
small intestine, is concealed and covered by the villi of the mucous
membrane.  Within  it  is  contained  a  variable  quantity of nuclei
and granular particles, which, in the present state of our knowledge,
must be viewed as a secretion.   How  this  secretion  is discharged is
a matter of uncertainty, as no orifice has as yet been clearly demon-
strated ; hence some anatomists regard these glands as closed vesicles,
which burst when distended to a certain point.

                               Fig. 167.
  Vertical section through a patch of Peyer's glands in the dog.  a. Villi, b. Tubes of Lieberktihn with the
apices of Peyer's glands,  c. Submucous tissue with the glands of Peyer imbedded in it. d. Muscular
and peritoneal coats, e. Apex of one of Peyer's glands projecting among the tubes of Lieberktihn.  The
glands are seen laid open by the section. Magnified about 20 diameters.

   Peyer's  Glands.*—These  may be  regarded  as  aggregations of
solitary glands, forming circular  or oval patches situated on the free
border of the intestine (Fig. 167).   They belong particularly to the
ileum, and  ought to be regarded  as  forming a  special anatomico-
physiological feature of that portion of the intestine, and  as indica-
tive of its proper limits.   We find in  man as many as from  seven-
teen to twenty-two patches, but with great variety both  as to number
and size.   The patches are smallest towards the jejunum, and increase
considerably in size towards  the caecum, so  that some quite near
the latter  intestine  measure from  two to  four inches in their long
diameter.
   Each of the small glands, the  aggregate of which constitutes the
patch  of Peyer, is placed in a  depression and surrounded by a groove
resembling that which surrounds the papillae vallatae of the tongue ;

  * The glands, so long known by this title, may be called " Grew's glands," with as
much justice.   They were discovered in several  animals  by our countryman, Dr. Ne-
hemiah Grew, who also  delineated them  with great accuracy, and described them in
his lectures to the Royal Society, in the year 1676, before Peyer's book was published
(1677). Dr. Grew's descriptions and delineations may be found in an essay appended
to his catalogue of the museum of the Royal Society, of which he was Curator, entitled
" The Comparative Anatomy of the Stomach and  Guts begun."  See the advertisement
prefixed to this work. 
532
DIGESTION.
some being inclosed by a circle of the orifices of large tubes of Lie-
berkiihn.  It  seems to be in every respect similar, as regards its
intimate structure, to  the solitary glands,  and probably discharges
its secretion by a similar mechanism.   The arrangement and  struc-
ture of these glands are well seen in a vertical section, as represent-
ed by Fig. 167.
  Peyer's glands are well developed in the Carnivora, more so than
in Herbivora, and  they commence  very high  up in the intestine,
whence it would appear that the  shortness  of the  small  intestine
which distinguishes the former animals is due to the  imperfect deve-
lopment of the duodenum and of the jejunum.
  The office of these  glands is  involved in great obscurity; most
probably it is connected with the further reduction of the alimentary
matters as they pass through the intestine.   But we  are unable to
form any conjecture as to the causes which determine the peculiar
shape or position of the glands, or as to the  nature of their secretion.
They are larger  and more developed during  the digestive process
than during fasting, a fact which  denotes that  the former is  the
period of their greatest activity of function.   It is not impossible
that the peculiar  odour of the  feces, which  is in a great measure
characteristic in particular classes of animals, may be due to a  secre-
tion by these glands.
  In typhus or typhoid fever, these and the solitary glands are  prone
to become inflamed and to ulcerate.  The poisonous  matter  which
generates the fever is apt to fix on these glands;  or they may be
the special channel for its elimination, and in the  process they suffer
irritation.  In phthisis, these same glands are very liable to become
the seat of the tubercular deposit, and also of an  ulcerative process,
whence results the diarrhoea which proves so troublesome an accom-
paniment of that disease.*
  In Asiatic cholera, all these glands become greatly enlarged from
the accumulation of  a large quantity  of  granular matter in  the
vesicles.
  Brunner's  glands exhibit a remarkable immunity  from disease,
and in this, as in other respects, they resemble the pancreas.

  In concluding the account of the anatomy of the  intestinal tube,
the following summary of the special characters  of each portion of
it will  serve  to indicate more clearly what we  have alluded to
above—that the physiological anatomy  of the  mucous membrane
affords  the best basis for its subdivision into portions, each of which,
no  doubt, exercises its special function in the  digestive process :—
  In  the duodenum, the mucous membrane  exhibits:  1, cells  and
tubes like pyloric cells, gradually passing into straight Lieberkuhn's
tubes,  which exist throughout the rest of the gut; 2, villi commenc-
ing in the upper part by the elongation of the  septa between the cells,

  * Some excellent remarks on the structure of the solitary and Peyer's  glands may
be found in a paper by Dr. Handheld Jones,  "On  the Intestinal Mucous Membrane."
—Lond. Med. Gazette, 1848. 
INTESTINAL DIGESTION.
583
the villi becoming extremely numerous and crowded together in the
inferior two-thirds ; 3, in the lowest third a few  solitary glands ;  4,
Brunner's glands, very numerous in the upper part, gradually dimin-
ishing in size and number below;  5, valvulae conniventes, well de-
veloped in the inferior half.
  The orifice by  which the biliary and pancreatic ducts open  into
the intestine, is placed where  Brunner's glands have either become
very few or have ceased.   In most of  the Carnivora which we have
examined, these ducts open below the region of Brunner's glands ;
the point at which they pour their contents into the bowels has there-
fore no constant relation to the duodenum, if, as it is convenient to
do, we may make the presence  of  these  glands the characteristic
mark of that portion of the intestine.
  In the jejunum, the mucous  membrane is characterized  by,  1,
Lieberkuhn's follicles and villi  well developed ;  2,  valvulae  conni-
ventes,  larger  and  more  complete  than elsewhere;  3,  solitary
glands.
  The ileum exhibits : 1,  Lieberkuhn's follicles and villi  well deve-
loped down  to the ileo-caecal valve ; 2, valvulae conniventes, which
gradually diminish towards the termination of the ileum, and disap-
pear ;  3, solitary glands;  4,  aggregate glands, or Peyer's  patches,
which are small at the upper part of the ileum, but greatly increase
in size at its lowest portion.
  The mucous membrane  of the caecum and of the whole large in-
testine is  distinguished by the  complete absence of villi;  by the
presence of Lieberkuhn's  follicles  and of solitary glands  of large
size, which are numerous in the vermiform appendix, as well as in
the caecum itself; and  by the folds which form the partitions be-
tween the cells of the colon,  as well as by the valvular folds of the
rectum.

  Movements of the Intestines.—The  substances which enter the
intestinal canal from the stomach are moved onwards by means of
what is called the peristaltic,  or the vermicular action of its muscu-
lar coat.
   This action of the intestines is very conspicuous in animals opened
immediately after death ; under these circumstances it is probably
in an exaggerated state, owing  to  the stimulus created  by the en-
trance of  cold  air  into the  abdomen.  It may be  displayed  in a
highly active state by subjecting the  intestinal  canal of an animal
just dead to the  influence  of  the magneto-electric machine, by the
successive shocks of which this action becomes greatly increased in
intensity and rapidity, though not altered in character.
  In dogs and cats, in which  we have most frequently observed the
peristaltic action, it seems to  commence at the pyloric third of the
stomach, whence  successive waves of contraction and relaxation (the
former  being instantly  succeeded by the latter) are propagated
throughout  the entire length of the small and large intestines.  The
advance of  the waves is always downwards.  In examining a por-
tion of intestine  at the moment of  its contraction, we perceive a di- 
584
DIGESTION.
latation above it as well as below it;  the  latter being  produced  by
the protrusion into it of the contents of the now contracted portion
of intestine ;  the former, by the relaxation of a previously contract-
ed portion.   The rapid succession of these contractions and relax-
ations give to the movements of the  intestines the appearance of
the writhings of a  worm, whence they are  distinguished by ihe ap-
pellation vermicular.  Sometimes we have  opportunities of observ-
ing these movements during life in man, in  cases of extreme attenu-
ation of the abdominal  parietes ; or in cases  where, from  some
great obstruction in the course of the alimentary canal, the  peri-
staltic action is  very much increased  in intensity above the seat of
the obstruction;  or in wounds of the abdomen; or during surgical
operations.
   There are certain facts which justify the supposition that this ver-
micular action has a proper rate of  speed  in  each individual, and
that substances introduced into  the  highest  part of the  intestinal
canal take a certain time, varying in each particular case, to traverse
it.  For example, the act of defecation will,  if allowed or encour-
aged, take place with the utmost regularity every twelve or twenty-
four hours, and the quantity discharged will  exhibit  but little va-
riation,  the quantity and quality of the food  remaining  the same;
and indigestible substances taken with the food, seeds,  husks, skins,
&c, will at certain intervals  appear in the feces, having traversed
the whole canal.   There is no act of the animal economy more strik-
ingly under the influence of habit,  i.  e., under the control of physi-
cal causes, without  mental  interference, than this of  defecation ;
nor, on  the other  hand, is there any act  which may be more  com-
pletely  deranged by its being baulked, through the resistance which
the will can oppose to it.  The intestinal  movements are partly due
to the  influence  of the stimulus of  distension upon  the muscular
tunic, and partly to the reflex action  of the ganglia of the intestinal
portion  of the sympathetic, stimulated by the  contact of the  intes-
tinal contents with the mucous membrane.  Direct irritation of the
solar plexus, or of the semilunar ganglia, produces a marked increase
in the movements of the intestines (  Vide p. 508).
   When obstruction exists at a certain  point of the bowels they
become dilated above that point, and  when the  dilatation has  at-
tained a certain  amount their contents are found to flow back into
the stomach, and are ejected by vomiting.  This is commonly sup-
posed to be due to an inverted  direction of the action of the muscu-
lar tunic of the intestines (antiperistaltic  action).   But Dr. Brinton
has very ably shown that there  is no antiperistalsis  of the bowels
under these circumstances, any more than of  the stomach in vomit-
ing,  and that the altered course of the fluids is due simply to their re-
flux along the axis of the intestine from the seat of obstruction.   The
muscular  coat of the bowels acting in the downward direction, and
with force proportionate  to the obstacle, propels the fluids to a  point
where they encounter insuperable resistance, and whence they must
take the course which affords least or no obstacle.  Thus, a back-
ward current is established in that part of the fluid least influenced 
INTESTINAL DIGESTION.
585
Fie. 168.
by the walls of the intestine, that, namely, which occupies  its axis,
or, in Dr. Brinton's words, "an axial reversed current is developed,
which returns matters from the neighbourhood of the strangulation to
some higher point in the canal."   When fluid returns along the sides
of a syringe with a piston not water-tight, we have a somewhat ana-
logous phenomenon, and we may imitate the reversed movement of
the intestinal fluids by trying to push water through  an obstructed
syringe, the piston of which is perforated in the cen-
tre, as illustrated by the annexed wood-cut (Fig. 168).*
   The contents of the intestine are moved on, portion
by portion, much as in oesophageal deglutition.   And,
in their  progress, they are mingled with fluids poured
out from the intestinal mucous membrane.
   Changes in the Mucous  Membrane during Intestinal
Digestion.—During  intestinal  digestion,  the mucous
membrane exhibits an increased  nutrient  activity, as
evinced  by a greater afflux of blood, and by free secre-
tion, as  well as absorption;  in  connection  with  which
last function it exhibits peculiar changes,  which must
be specially noticed.   It is red, moist, and covered with
a more  or less abundant mucus, &c.
   The most remarkable change  which takes place in
the mucous  membrane  of the  intestinal  canal  is ob-
served in that  portion  of it  which is  covered by villi;
that is, throughout the small intestine, especially below
the point  of entrance of the  hepatic and pancreatic
ducts.   The villi are the  agents of a peculiar process
of absorption; and the changes which take place in them
at this period appear to have  immediate  reference to
the part which they perform in this function.   They
become  enlarged and turgid, partly  owing  to an in-
creased  afflux  of blood to them, and partly in conse-
quence  of a change  which  takes place in the intra-
villous tissue,  whereby  the component   nuclei  and
granules acquire an increase of  size, and some of them
arrange  themselves in lines passing from the free ex-
tremity to the base of each villus (Fig. 160, a).   These
lines appear  to proceed from an accumulation of  small
cells formed  at the free extremity of  the villus within
its cavity (Fig. 160, b b):  they are quite opaque, and
their  structure is,  therefore,   impenetrable to  high
powers in the microscope; they coalesce at the base of each villus,
beyond which we have not succeeded in tracing them.f
  At this period an  abundant quantity of loose  epithelium  is  in
contact with  the mucous membrane, and surrounds the villi;  and the
Diagram to illus-
trate the forma-
tion of  a  back-
ward axial cur-
rent in  pushing
water   through
an obstructed sy-
ringe with a pis-
ton perforated in
the centre.
  * Contributions to the Physiology of the Intestinal Canal, loc. cit., a highly ingeni-
ous and interesting paper.
  f The phenomena  here described were observed in dogs and cats fed in the ordi-
nary way upon meat, milk, &c.
       38 
586
DIGESTION.
sheaths of  the latter seem to adhere very loosely to them, and may
be much more readily detached than when the digestive  process is
not going on.
  Mingled with the abundant mucus of the intestine, we find at this
period very numerous white flocculi of a soft, loose, curdy material,
the whiteness of which is conspicuous in the midst of other matters,
which are more or less coloured from intermixture with bile.  And,
at the  same time, the plexus  of lacteal vessels, which  is formed
beneath the mucous membrane, and  from which the larger lacteal
vessels  proceed  through the mesentery to the mesenteric glands, is
filled with a white fluid of the exact colour and appearance of milk,
commonly called the chyle.
  The  display of the  lacteal vessels filled with Avhite chyle, at this
period,  is one of the most interesting sights among the many wonder-
ful  objects which engage the observation and  the  attention of the
anatomist.
  The white flocculent matter is most abundant in the  duodenum
and jejunum, and there the villi are most numerous; thence, likewise,
proceed the greatest number of lacteal vessels.  Lower  down in the
small intestine the flocculi gradually become  less and less  numerous,
and ultimately disappear, the  contents of the intestine consisting of
a more  or less fluid mass, apparently homogeneous, and coloured by
bile.  At the same time the  villi become  fewer and  smaller, the
number of lacteal vessels diminishes, and the glandular  apparatus
of the intestinal mucous membrane is more developed and distinct.
  The  occurrence  of the flocculent matter,  in that part of the in-
testine  where the  absorbing organs and the  chyliferous vessels are
most numerous,  denotes  that  it must be regarded as  constituting.
the nascent condition of that fluid which at this period fills  the lacteal
vessels  and  gives them their white colour—the chyle.   It appears
like a precipitate from the general mass  of the intestinal contents,
and many distinguished physiologists have regarded it in  that light,
and have attributed its precipitation to the  addition of the biliary
and pancreatic fluids to the chymous  mass  which  has  been pushed
on from the stomach into the intestines.
  This flocculent matter consists of a multitude of minute molecules
apparently of a  fatty nature (as they disappear under the action of
ether),  mingled with larger oil-globules, and also of numbers of parti-
cles of columnar epithelium,  containing  within  them several  fatty
molecules of large size, readily distinguished by their highly refrac-
tive power.   The contrast between the epithelial particles obtained
from this flocculent matter, and those of the intestine of an animal
that had fasted for some time before death, is very striking, and in-
dicates that they undergo a change during chylification,  either con-
nected  with the  absorbing process or with the transformation of the
alimentary substances.   (Fig.  103.)
   Of the peculiar mechanism by which this nascent chyle is intro-
duced into the lacteal vessels, and of the nature of the changes which
it undergoes in them to form perfect chyle, we can form no adequate
idea in the present state of our knowledge.   We do know, however, 
           CHANGES OF FOOD IN THE SMALL INTESTINE.        587

that the material before its entrance into the vessels is very different
from what  it becomes after its introduction; and that in its advance
towards the centre of the absorbent  system it undergoes  further
changes, all of which tend to assimilate  it more nearly to the blood
itself.
   Of the Chyle.—If,  as seems most correct, we apply the  term chyle
to the fluid contained in the lacteal vessels during and shortly after
digestion, we  must make  the distinction between  white  chyle and
transparent chyle.   The white chyle is a milk-like fluid,  homogene-
ous in appearance, which,  on being withdrawn from  the lacteals and
allowed to  stand, separates, as blood would do, into serum  and a clot.
This clot consists of fibrine, which  entangles, by its coagulation, cer-
tain particles  proper to the chyle.  These are chyle-corpuscles or
globules, in every respect similar to lymph-corpuscles, and an infinite
multitude of particles of extreme minuteness, to which Mr. Gulliver
has given the  name of molecular base of the chyle.   These particles
consist of fatty matter in a state of extreme subdivision.
   During fasting, and also during the digestion of food Avholly devoid of
fat, the fluid contained in the  lacteals  is  perfectly  transparent and
colourless, and not to be distinguished  from the lymph of the lym-
phatics.   In this fluid there is no molecular base, while all the other
elements of the chyle  are  present.  Hence there can be no doubt
that the white colour of the chyle is due to the presence  of  the mo-
lecular base.
   The chyle may exhibit various degrees of milkiness, according to
the quantity of the molecular  base.  The white chyle, therefore, is
chyle with molecular base in greater or less quantity; the transparent
chyle is devoid of molecular base.  Both kinds  of chyle consist of a
liquor chyli, essentially the same as the  liquor sanguinis,  holding
suspended in it  chyle-globules in the transparent chyle,  and in the
white chyle-globules, fat-globules',  and molecular base.*
   It would seem to follow, from observing the changes  which the
food undergoes  in the  small intestine, that the immediate  office of
that portion of the intestinal canal is to form this chyle;   and it ap-
pears probable that the secretions poured into the small intestine
from the glands, especially the liver, pancreas, and the  glands of
Brunner, which communicate with it, exercise  a chemical influence
upon the  alimentary matters whereby this material  is formed.  We
shall see further  on that this view  receives strong support from the
results of experiments and observations respecting  the functions of
the pancreas and liver.
   Changes of the Food in the Small Intestine.—It remains now to in-
quire whether all the digestible food which passes from the stomach
undergoes  the change into chyle, or whether certain parts of it  only
are simply dissolved and pass by absorption directly into  the portal
blood, as in the stomach, whilst other parts are converted  into chyle,
and enter  a different part of  the circulation  through  the lacteal
vessels.  In other  words, is it necessary that  all food, prior to its
* See the Chapter on Absorption. 
588
DIGESTION.
appropriation by the  blood as nutriment, should pass through the
condition of chyle?
   As it  has been shown that the stomach can absorb  certain fluids
and dissolved solids, through the absorbing power of its bloodvessels,
there can be no good reason for denying  the same power to the in-
testines, which have a vascular system precisely of the  same  kind
as  that  of  the stomach.   Now the substances which the stomach
completely  dissolves and absorbs, are the  azotized aliments : it seems
not unreasonable to conclude that such portions of these aliments as
have escaped absorption by the stomach,  may undergo a  similar so-
lution in the intestines, and   be   absorbed  by their bloodvessels
without  passing through the state of chyle.
   But to answer this  question  accurately we must  determine pre-
cisely the changes which each kind of food undergoes in the intestine.
   Bouchardat and  Sandras have obtained from  their experiments
results which indicate that fibrine does not undergo the change into
white chyle.  They fed animals with fibrine, coloured with saffron or
cochineal, and were unable to detect any trace of the colouring mat-
ter in the chyle.  They found, likewise, that the contents  of the lac-
.teal vessels  of animals kept fasting differed in no respect from that of
animals  fed on fibrine.   These experiments, therefore, render it highly
improbable  that  fibrine contributes  to the formation of white chyle,
and Tiedemann  and Gmelin had long since found that the quantity
of  fibrine contained in the lymph and  chyle, after a long fast, is
not less  than that  which is  found  there  after digestion.   Bouchar-
dat and  Sandras obtained the same results in their  experiments on
animals  fed on albumen, caseine, or gluten, as on animals fed with
fibrine;  these  substances, therefore, must likewise be excluded  from
the list of those which are capable of forming  chyle.   Hence the
whole class  of neutral azotized substances, admitting of solution by
pepsin, may be absorbed without passing  into the state of chyle.
   Neither does it  appear to be necessary for the  appropriation of
amylaceous aliments  that  they should pass into  the condition of
chyle.   These substances  are but little digested in  the stomach,
and undergo their  principal changes  in the small intestines.   Here
the pancreatic fluid exercises  a similar influence upon them to that
which the neutral azotized 'matters experience from the gastric juice.
Bouchardat and Sandras found that a few drops of pancreatic fluid,
added to some boiled starch,  and kept at the temperature of  from
95° to 101°, dissolved  it in a short time, the liquid  became trans-
parent, and all trace of starch disappeared.   The same effect is pro-
duced if a piece  of the pancreas be used instead of the  pancreatic
fluid.*

  * Dextrine  is a substance having some of the properties of gum, and obtained from
starch by  the action of heat, diastase, or dilute acids.  It is soluble in water, and ex-
ists in almost every part of plants. When starch is boiled in water for some time, an
abundance of  dextrine is produced.  If the action of diastase or of the  acids be con-
tinued too long, or  if the  quantity of either be too large, grape-sugar is produced.
Hence dextrine may be regarded as the first stage in the transformation of  starch
into suger.  The formula  for dextrine is C12,  H'°, O'0.—See  Mulder's Chemistry  of
Animal and Vegetable Physiology, by Johnston, p, 224. 
INTESTINAL DIGESTION.
589
  The starch in  these  experiments is  converted  into dextrine,  or
into  sugar, in which state it is  soluble, and  thus admits of direct
absorption into the bloodvessels, or the sugar undergoes a further
change into lactic acid,  and in this condition passes into  the circu-
lation.  It appears that the  presence of a free alkali is as neces-
sary for these changes, as that of acid is needed for the solution of
the neutral azotized substances.  If the pancreatic fluid be acidu-
lated, it  ceases to  act  on starch, but, according to Bernard and
Barreswil,  acquires  the power of dissolving  albumen,  fibrine,  &c.
We do not, however, find that alkalized pepsin  is capable of dis-
solving amylaceous matters.
  Bouchardat and  Sandras  have  examined  the  changes which
starchy substances undergo in the stomach and intestines in  dogs.
Man and carnivora are  unable to digest raw starch in the stomach
or intestines.  Raw potato-starch introduced in  a muslin bag into
the stomach through a fistulous opening in the walls of the stomach,
and withdrawn after a sojourn of twenty-four  hours in  that viscus,
showed no sign of any  change; nor did the gastric juice out of the
body, the mixture having been kept  at a high temperature for the
same time, exert  any influence upon the starch grains.   When dogs
were made to swallow raw starch, the grains were afterwards found
intact in  every part of the  intestinal  canal.  Babbits  and  gran-
ivorous birds, however,  were  found to possess the power of digesting
raw starch, although more slowly than  that which had been cooked.
But this power was found to reside mainly in  the upper  part of the
small intestine, and as the grains of starch became gradually fewer
as the food descended in the  intestinal canal, it seems reasonable to
believe that  each succeeding portion  exercises a  certain  digestive
power over them.   In birds, the digestive power of  the small intestine
was  greater  than in rabbits, the lower part of the intestine in the
former exhibiting no traces of the starch grains. In the upper part of
the small  intestine  sugar  and dextrine were found, and the lower
the contents  had  passed down, the more did all traces of starch dis-
appear.
   Boiled starch is  more readily  digested by all animals than raw ;
to the carnivora and to man, cooking is essential to its perfect di-
gestion.   The same changes take place in it  as in  the  raw starch,
i. e.,  it seems to  undergo  conversion into  sugar,  dextrine,  and
lactic acid.  This  change, however, is very slow  and gradual, and
although it occurs chiefly in the  upper  portion of  the intestine, it is
found taking place throughout the whole  canal.   The rapid forma-
tion of sugar in the intestinal canal leads to a proportionally rapid
absorption of it,  and to the elimination of it by the kidneys.   It is
apparently to guard against this, to protect the kidneys against the
irritating  influence of this substance, that the change of the  starch
into sugar and dextrine goes on with  great slowness  throughout the
whole intestinal canal.
   Our own  experiments  have yielded results similar  to those  of
Bouchardat and  Sandras, and confirm their conclusion, that neither
azotized matters nor amylaceous substances  contribute to form the 
590                        DIGESTION.
true white  chyle.  At least it  may be  aflirmed that when  animals
are fed on such food, carefully  freed from all oily or fatty matters,
the  fluid which is found in the  lacteal vessels is perfectly trans-
parent, and in all respects identical Avith that which  is found  in
them after a  long fast.   We select  the following  experiments  in
illustration of this statement:—
  Exp. 1.—A cat was fed  on  horse-flesh, carefully freed from fat,
on the 7th of  July, 1848.   On the two subsequent days it  was fed
on the whites  of eggs, freed from yelk: and on the 10th, it  was fed
on the whites  of five  eggs, at nine o'clock A. M.  At half-past one
P. M., on  the same  day, it was  killed.   The  thoracic  duct was
filled by a perfectly limpid chyle,  which exhibited no molecular
base, a  few chyle-corpuscles, and a few blood-corpuscles.   The
lacteals were with difficulty visible in consequence of the transpa-
rency of the  fluid by which they were filled.   The  stomach and
duodenum  contained  pieces of softened albumen, as well as a con-
siderable quantity of a soft homogeneous jelly-like mass.  In the
latter intestine the villi  were covered with  epithelium, and did not
exhibit  any appearance to indicate that they were  the seat  of an
active process of absorption.
  Exp. 2.—A small healthy terrier was fed  at nine A. M. with half
a pound of wheaten bread, having  previously fasted twenty-four
hours; it was killed at one o'clock on the same  day.  The thoracic
duct was filled with  a clear fluid, which, when collected on  a slip
of glass, exhibited a  faintly reddish hue.  Under  the microscope it
was found  to  exhibit numerous red blood-corpuscles, with  a  much
small number of white corpuscles,  but more than the usual pro-
portion  for blood.   No  molecules were perceptible.   The  fluid,
when collected  in a watch-glass, coagulated in two  minutes into
a firm clot.   A  small quantity  of  softened bread  was found  in
the stomach, and a  still  smaller  quantity of the  same bread very
much softened,  liquid, diffused, and coloured by bile, was found  in
the  duodenum.   In  both, the contents  were acid.  The villi were
covered with epithelium,  which adhered firmly to them, without any
great opacity of their interior, or other  indication  of activity  of
function.   On  chemical  examination, by   our friend Mr. Lionel
Beale, junior, a highly  competent  analyst, the contents of the
stomach were  found  to consist of a small quantity of  sugar, with  a
good deal of starch;  while in the  duodenum, sugar existed  in great
abundance, and the starch only in very minute quantity.
  Exp. 3.—A similar dog to  the preceding was fed  at the same
time with two ounces and a half of horse-flesh, and the same quan-
tity of beef suet; it was killed four hours and  a half after having
been fed.  The whole lacteal  system was  distended with a white
milky chyle, which, under  the  microscope, showed a large quantity
of  molecular  matter,  as  well  as  red and  white blood-corpuscles.
The contents  of the  intestine  were more or less acid throughout,
and abundantly coloured by bile.  There were very numerous white
flocculi, most  conspicuous in the duodenum,  and becoming gradually
less numerous to within an inch or two of the  caecum, where they 
INTESTINAL DIGESTION.
591
 ceased.  These flocculi consisted of an abundance of granular matter
 with  columnar  epithelium, having  the free ends of the particles
 filled with minute oil-globules, while  the  neighbouring  epithelium
 contained  no oily matter.  The villi  were mostly stripped of their
 epithelial  sheaths, or held  them  very loosely;  the intra-villous
 structure was opaque, and the vesicular structure beneath the  base-
 ment-membrane at their free extremities was very  distinct.
   It  was  evident in  these experiments that the  marked contrast
 between the  state of the  contents of the lacteals, and the condition
 of the villi, was connected with the presence or absence of fat in the
 food, and that so  long as the food was purely albuminous or fibrin-
 ous, or mainly amylaceous, the chyle was  transparent, and the villi
 apparently inactive ; but that the addition of fat to the food called
 the villi into activity, and filled the lacteals with an abundant milky
 chyle.
   Are we  to infer then that the lacteals absorb fatty matters  only,
 and that the villi are altogether inactive, save when fatty or oily
 substances are to  be absorbed ?  We apprehend that  such an infer-
 ence is not justifiable ; it may, however, be  concluded that the villi
 and the lacteals are  capable of  absorbing all  substances which the
 bloodvessels  absorb, and by a simple process ;  but  that the  absorp-
 tion of fatty matters devolves upon them  only, and  is a more com-
 plex process, involving considerable  changes in their tissue.
   And upon similar grounds we may conclude that while albuminous
 and fibrinous aliments contribute to  the formation of chyle, they do
 not necessarily undergo the change into chyle in order to be ab-
 sorbed.  But fatty matters appear to admit of absorption in no  other
 way, except by a  reduction to the  state of molecular base of the
 white chyle.
   These observations and  experiments denote sufficiently clearly
 that two channels  exist for the transmission of the nutritious  mat-
 ters from the intestines  to the blood;  one through the lacteals, by
 the villi; the other directly through the walls of  the bloodvessels
 themselves.  Matters taking the latter route must  pass through the
 liver, and would be subjected  to the influence of that gland before
 they reach the inferior vena cava and the right auricle, while  those
 passing through the former channel must permeate a totally distinct
 system  of vessels,  namely, the lacteal system, to be conveyed to the
superior vena cava and to the right auricle, where, having mingled
with the blood coming from the liver,  both  are transmitted by the
right ventricle to the lungs.
  And  it would seem that the object of the two modes of absorption
at the  intestine, and of the two  paths  of transmission from the in-
testine to the centre of the circulation, is  to keep  separate,  up to a
certain  point, two kinds of material  resulting from the digestion of
the food.  And probably the reason why one kind  of product  is re-
served to pass through the intricate  capillary plexuses of the vascu-
lar system of the liver, to the exclusion of the other, is because it
contains material  out of  which the liver may elaborate bile ; whilst 
592
DIGESTION.
the other  material is transmitted through a less complicated series
of channels more directly to the lungs.

   Of the Offices of the Pancreas and Liver in Digestion.—The pre-
sence of two such great  glands as the pancreas and the liver exist-
ing in a large portion of the animal kingdom at the  upper part of
the intestinal canal, and pouring their secreted fluid into it, obviously
denotes a  connection  between the fluids secreted by these  glands,
and  the changes which  the food undergoes in this part of the in-
testine.
   As the function of the pancreas has been determined with greater
accuracy than that of the liver, it will be more convenient to con-
sider it first.
   Function  of the  Pancreas in Digestion.—The presence of  the
pancreas is constant, at least, in the vertebrate classes.
   It is present in all the  mammalia—it is, perhaps, better developed
in carnivora than herbivora; in all it is in intimate relation with the
upper part of the small intestine into which it pours its secretion by
one or two ducts.   In some, as in  man, the pancreatic duct and the
common choledoch duct open into the duodenum at the same place ;
in others they open at some distance from each other (as much as
sixteen or seventeen inches in the rabbit) but in all they open into
the same portion of the intestinal canal;  and the pancreatic duct,
always  below the biliary duct,  when  they do not open  together.
Some doubt  exists  as  regards its  presence  in fishes.   In rays and
sharks, a  solid gland exists, corresponding to the pancreas; and in
osseous fishes a similar gland has recently been discovered by  Stan-
nius,  Avhich  appears to be its analogue.*
   The secretion of the pancreas has some resemblance to saliva. It
has been lately studied with great care by  M. Bernard, from whose
clear and admirable memoir the following account of it is derived.
   The pancreatic fluid maybe procured most readily and in greatest
quantity at the commencement of the digestive  process.   Bernard
obtained it from the dog  in the following manner : the  animal having
been  well fed, after a fast of some hours, an incision  was made into
the abdomen below the margin of the ribs sufficiently large to enable
the operator to draw out the duodenum, and with it a portion of
the pancreas.   The larger of the two pancreatic ducts was now
rapidly isolated, and opened with fine scissors, and into this opening
a  silver tube was introduced and fixed in the duct by a ligature.
The intestine and pancreas were replaced, and the wound in the ab-
domen closed by suture,  the free extremity of the tube being allowed
to project through it.   To the silver tube was now attached a small
caoutchouc bag, perfectly exhausted of air, and to the opposite end
of this another similar tube was fixed.  The pancreatic fluid flowed
freely through the  first  tube into the caoutchouc bag, and accumu-
lated there;  and as much as two drachms and a quarter were col-
* Muller's Archiv., 1849. 
FUNCTION OF THE PANCREAS.
593
lected in five hours and a half.  The fluid flowed from the tube freely
drop by drop.
  When this operation Avas  performed at the commencement of di-
gestion, Bernard obtained, between  half-past seven A. M. and five
P. M., four drachms  and one third of the fluid, making an average of
nearly half a drachm an hour.
  On  the  following  day, when  signs of inflammation had  shown
themselves in the wound,  more than four drachms of the fluid  were
obtained in one hour and  a quarter.   The quantity of the secretion
was considerably increased, but its quality was altered—its consist-
ence being much diminished, and its  physiological properties mate-
rially changed.
  When the  experiment was performed on an animal in which the
digestive process Avas fully established, the quantity of fluid obtained
was  much  less than at the earlier period, but its quality much the
same.   During abstinence, only a very small quantity of the pancrea-
tic juice could be obtained at the time of the operation; but the fol-
loAving day, when the wound became inflamed, a  fluid much altered
in quality flowed out very freely.
  If the operation were sloAvly performed, so as to expose the intestine
long to the action of the air,  and to  irritate it and the  gland, the
quantity and quality of the  secretion Avere much altered.
  As the characters of the pancreatic fluid vary so readily with the
circumstances attending the operation of obtaining it, Bernard de-
scribes two  kinds of fluid,  the first  being the normal, or that ob-
tained under the best  conditions,  the second, the  morbid, or that
obtained after inflammation has commenced in the Avound  and in the
pancreas.
  The  normal  pancreatic fluid is a colourless, limpid fluid, viscid
and gluey, flowing slowly by large  pearly or  syrupy drops, and be-
coming frothy on agitation.   It  has  no characteristic odour—it has
a slightly saltish taste resembling that of  the serum  of  the blood.
Bernard has always  found it alkaline in reaction—never either acid
or neutral.   It coagulates  by heat as completely as Avhite of egg,
becoming completely solid,  and  not leaving  a drop of fluid.  The
mineral  acids, likewise, cause  it  to  coagulate, as also  the  metallic
salts, alcohol, and pyroxylic spirit.   It is  not coagulated bydilute
acetic, lactic, or  hydrochloric  acids.  Alkalies cause no  precipitate
in it, but redissolve  that  thrown  doAvn by heat, acids, or alcohol.
  This constituent of the pancreatic fluid,  which is coagulable by
heat, &c, although  apparently identical with albumen,  is not so:
it differs from albumen in the following point.  When the coagulum
obtained from the pancreatic fluid by alcohol is dried,  it can be re-
dissolved completely and  readily in Avater,  and it gives to the Avater
the peculiar viscidity of the pancreatic juice, and likeAvise its physio-
logical properties, whilst albumen treated in the same way, undergoes
scarcely any appreciable  solution in water.
  At  a high temperature the pancreatic  juice rapidly  changes, is
decomposed, and loses  its property of coagulating by heat. _  At a
low temperature it may be  preserved for many days—Avhen its vis- 
594
DIGESTION.
cidity increases and it becomes of the consistence of a weak jelly.
Bernard has examined  the pancreatic juice in rabbits, horses, and
birds, and has found it in all to exhibit the same essential character
as in dogs.
   We have  already stated that the pancreatic fluid, or a piece of the
pancreas itself, is capable of promoting the transformation of starch
into sugar, and therefore of promoting the digestion of  amylaceous
matters.  But that  this poAver does  not belong exclusively to the
pancreatic fluid is evident from the fact that other  fluids or animal
substances are capable of producing similar  transformations.  Ber-
nard has shoAvn by  direct experiment  that the pancreatic fluid pos-
sesses  the  peculiar property, which  is not enjoyed by any other
animal fluid, of modifying in a special manner or digesting all the
neutral fatty matters Avhich are met Avith in food.
   Thus  by  mixing  fresh  pancreatic  juice,  possessing the  normal
characters above described of viscidity and alkalinity, Avith olive oil,
and shaking the fluids Avell together, a perfect emulsion is formed,
and a liquid similar to milk or chyle is the result.   A similar  effect
is produced  by the  admixture of pancreatic  juice and fresh butter,
or  of mutton suet,  or hog's  lard, care being taken to  expose the
mixture in a sand-bath to a temperature of from 95° to 100° Fahr.,
so as to melt the butter and  suet,  and aftenvards to  shake the mix-
ture well.
   So  perfect is the  emulsion formed by means of the action of the
normal  pancreatic fluid upon fatty matters, that the mixture, if left
from fifteen to eighteen hours at a temperature of from 95° to 100°,
continues to exhibit the  same colour and appearance, nor does any
separation take place between  the fatty matter  and the pancreatic
fluid.   It appears, nevertheless, that the fat is not simply divided,
and made into an emulsion, but that  it has undergone  a chemical
change into glycerine, and a fatty  acid; the fluid, which immediately
after the admixture Avas  distinctly alkaline, becomes,  after remaining
five or six hours, as  distinctly acid.   In the  tube  in which butter
had been submitted  to the action of  the pancreatic juice,  butyric
acid was easily recognized at a distance by its characteristic odour.
   We find that on rubbing up a piece  of quite recent pancreas taken
from  an animal killed during  the  digestive process,  Avith   fat or
lard, and a  little water at a temperature of 95° or 100°, a very per-
fect white emulsion is quickly formed.
   Bernard instituted experiments  to ascertain  Avhether other animal
fluids possessed this power over oily or fatty matter.   The fluids tried
Avere bile, saliva, gastric juice,  serum of blood,  and cerebro-spinal
fluid,  but none of them Avere found to  cause  any permanent  change,
either mechanical or chemical, in  the substances submitted to their
influence.
   It also appears, from  Bernard's experiments, and this is  a point
Avhi.ch may throw some light on certain forms of dyspepsia, that in
order that the pancreatic fluid should exercise its perfect action, it
must  be  strictly normal.  Bernard found that what  he calls the
abnormal fluid, namely,  that  which exhibits no  viscidity, Avhich is 
FUNCTION OF THE PANCREAS.              595
 watery and does not coagulate by heat, has no effect upon fatty sub-
 stances.
    To  complete  the proof of  the  special action of  the pancreatic
 fluid in the digestion of fatty matters, Bernard states that he has tied
 in the  dog the two pancreatic ducts, of which the smaller opens quite
 close to the  choledoch duct, and the larger about three quarters of
 an inch lower down.  Under  such circumstances fat passes through
 the small  intestine unaltered, and the lacteals are filled with limpid
 chyle totally devoid of the white colour.
    The influence of the pancreatic fluid in  the formation of the white
 chyle,  by  its action upon fatty  food, is  beautifully illustrated  by
 Bernard, in a very simple experiment upon the rabbit, which we have
 repeated with results precisely corresponding with those obtained by
 him.   The rabbit is selected for this observation, because, while the
 choledoch  duct  opens into the duodenum just  below the  pylorus,
 the pancreatic duct opens as  much  as sixteen  or seventeen inches
 lower down,  so  that all  that  length of intestine receives bile only.
 A small quantity of melted hog's lard Avas injected into the stomach
 (the  animal having been kept without food for twenty-four hours
 previously), after which it was left to eat freely of parsley and carrots.
 After five or six hours it was killed.  Between the openings of the
 two ducts  the lacteals contained a  clear limpid  fluid;  but below the
 pancreatic duct  the lacteals Avere turgid  with a rich Avhite creamy
 chyle.
   In confirmation of these results of experiments, it may be stated
 that patients  labouring under disease of the pancreas invariably suf-
 fer from extreme emaciation, and many cases are recorded in Avhich
 fat appeared  unaltered in the stools—apparently in  consequence of
 malignant  disease of the pancreas.  Cases of this kind are recorded
 by Elliotson,  Bright, and others.
   From the preceding facts,  so well collected by the industry and
 acuteness of Bernard, it seems to us that we must conclude that the
 principal function of the pancreatic fluid is to digest fatty matters,
 that is, to  reduce them  to a state  Avhich  will admit of their ready
 absorption by the lacteals.   This power is  mainly due to the  organic
 principle resembling albumen which is  held in solution in the  pan-
 creatic  fluid.
   An objection to this view arises from the fact that some animals
 have no fat, or oily matter, in their food, as, for example, many vege-
 table feeders.    This objection, however,  may  be thus met,  that
 nearly all vegetable substances contain a certain proportion  of oily
 matter, hoAvever  small—and,  moreover,  the pancreatic fluid might
 serve to digest the fatty matters of the bile  which, by absorption into
 the lacteals, are readily carried to the lungs for combustion.
   But that the digestion of fat food is not the  only office of the pan-
creas in digestion, is sufficiently proved by the experiments of Bou-
chardat and Sandras, already referred to, which point out the import-
ant share it takes in the  digestion of amylaceous matters.
   We may therefore conclude  that  the pancreas secretes a fluid  of
which the office is—first,  and specially, to  digest fatty and oily ele- 
596
DIGESTION.
 ments; and, secondly, to convert starch into sugar, and thus to pro-
 mote the digestion and absorption of amylaceous food.

   The Function of the Liver.—The liver is the largest gland in the
 body.  It is_ remarkable not  only for its complex structure, which
 will be described  in the chapter on Secretion, but also for its pecu-
 liar double circulation.  It is supplied with blood from  tAvo sources,
 namely,  from the hepatic artery, Avhich carries  red blood to it, and
 is distributed mainly to the coats of  the ducts—and from the vena
 portae, a A'ein in structure, but  an artery in its  mode of branching,
 which conveys  a  large  quantity of dark  blood, derived from  the
 veins of the stomach, the  intestines, the pancreas, and the  spleen,
 and which ramifies throughout every part of the liver, passino- into
 a dense capillary plexus, whence it is  taken up by the hepatic veins,
 and carried to the right side of the heart.   By this arrangement all
 matters absorbed into the bloodfrom the gastro-intestinal surface must
 pass through the liver, a point  of  anatomy which indicates that  the
 material added  to the blood by absorption from the stomach and in-
 testines, in some  Avay contributes to  support  the  function  of this
 gland.
   We may justly assume that  the bile is secreted from the blood of
 the vena portse, because of the great size of that vessel and the vast
 extent of the capillary plexus, which it supplies, more especially as
 the  small  size of the  hepatic  artery compared with the  great bulk
 of the gland, and  the trifling  degree  to  Avhich it can contribute  to
 the formation of the capillary plexus of the organ, clearly disqualify
 it for contributing to the secreting process.
   The bile, as a separated product, first  shows itself in the minute
 canals or ducts  which originate in  the substance  of the  liver, and
 which, by  frequent successive junctions, form two  large ducts, each
 somewhat  larger than a crow-quill, which emerge at the transverse
 fissure of the liver, the  one  from  its  right, the other from its left
 lobe.  These two ducts pass for a short distance downwards and in-
 wards, enveloped by Glisson's capsule, along with the trunks of the
 hepatic artery and portal vein,  and with the hepatic plexus of nerves
 and^ several large lymphatics, Avith some  lymphatic glands.   About
 an inch below their emergence they unite at  an  acute angle, and
 form a single duct a little larger than either ; this is the hepatic duct,
 which soon unites with a short duct proceeding from the  gall-blad-
 der, the cystic duct.  The union of these two ducts forms the ductus
 communis  choledochus, between two  and  three inches in  length,
 which  passes behind the two  upper  thirds of the  duodenum, and
 opens, along with the pancreatic duct,  into that intestine, in or close
 to the angle of junction  of its middle  and inferior third.
   The gall-bladder is a pyriform bag,  placed in a depression on the
inferior surface  of the right lobe of the liver, and serving as a reser-
voir  for the accumulation of the bile when its flow into the intestine
is interrupted or retarded.   We infer, at least, that this is its prin-
cipal use, because it is always found full after a long fast, and empty
when digestion  is going on.   Blondlot tied the common bile-duct of 
THE BILE.                        597
a dog, and established a fistulous communication  between the gall-
bladder and the external integument; thus the bile, Avhich ought to
descend into the intestine, would Aoav out at this opening.  He states
that while the animal was fasting sometimes not a drop of bile would
escape at the orifice, even for some hours; but in  about ten minutes
after  the introduction of food into the stomach, the bile Avould begin
to flow freely, and  continue to do so as long as digestion Avas going
on.*   The process of digestion in the duodenum  appears to favour
the flow of the bile into the intestine, either by the stimulus of the
food  in contact with  the  mucous membrane, acting by  reflection
upon  the muscular coat of the gall-bladder, and causing it to contract
and expel its  contents, or, by altering its position, so as to favour
the descent of the  bile, or by changing the condition of the orifice
of the duct, which in the empty  state of the  bowel would be closed
by the contraction of the  intestinal circular fibres.  Indeed, it  is
probable that all these causes Avould be brought  into operation  by
the duodenum  becoming filled Avith food, and  the digestive process
being set up in it.
   That the gall-bladder is not  an essential  part of  the  excretory
apparatus of the liver is shown by the fact that it is not universally
present  even  in the  highest  classes of  animals.   This  reservoir is
found in the animal series  first in fishes; but it is absent from many
genera of that class.  It exists  pretty constantly in reptiles and
birds, being occasionally Avanting in the latter, and in mammalia it
is absent from many of the   genera.  We do  not know the precise
laAV which regulates its  presence or absence, but it seems  that the
length of time for which animals are  accustomed  to fast has  prob-
ably  a good deal of influence.   Thus, in the herbivora, which  eat
often, and at short intervals, and whose digestion is slow, the gall-
bladder is frequently absent; and in the carnivora, which eat at long
intervals, it is almost constantly present.  But  there are many of
the  herbivora in Avhich it is present, as  in  the  ox, the sheep, the
goat, &c.  In the first giraffe examined in this country by Professor
Owen there Avas no gall-bladder; in the second two Avere found.f
   Quantity of Bile secreted.—Various attempts have been made to
estimate  the quantity of bile secreted by  the  liver in a given time ;
but,  in truth, Ave  have no   satisfactory  knoAvledge on  this point.
Blondlot, by the experiment  upon a dog detailed  above, was able to
collect the bile that flowed out  at the  external orifice, which must
have been all that was secreted.   The  quantity thus obtained from
one of his dogs amounted in twenty-four hours,  on the  average, to
twelve drachms and  a half.   Assuming, then, with Haller, that the
liver of  a man secretes four  or five times as much bile as that of a
dog,  Ave may conclude that  the  average  quantity poured into  the
human intestine in tAventy-four hours, is from six to eight ounces.
 Haller, himself, however, had formed a much larger estimate than
 this, namely, seventeen to twenty-four ounces.

                  "- Essai sur les fonctions du Foie, p. G2.
                 ■j- Art. "Liver," Cyclop. Anat. and Phys. 
598
DIGESTION.
   The Physical  and  Chemical Properties of Bile.—The bile is a
thick,  ropy fluid,  of a  greenish-yellow  colour, a bitter taste, and a
peculiar nauseous smell, Avith  a specific gravity of 1020  to  1030.
It has an antiseptic power, and not only itself  resists putrefaction
for a  considerable period, but prevents substances  Avith  Avhich it
mixes  from putrefying.   The  excessive  fetor of the  feces in  some
cases  of jaundice from  complete obstruction, and,  perhaps, also in
cholera, is probably due to the absence of the  antiseptic  influence
of the  bile.   The  reaction of the bile, according to Gorup-Besanez is,
when  first secreted, neutral;  but subsequently  it becomes slightly
acid, and ultimately alkaline.   The  Avell-knoAvn cleansing properties
of ox-gall are due to the  presence of alkali in  it, in considerable
quantity.
   According  to the  analysis  of Berzelius, which seems to be the
most trustworthy, and Avith Avhich that recently made by Mulder*
accords very closely, bile consists of Avater holding mucus in suspen-
sion, and  in solution certain salts, with a peculiar complex substance
called  by  Berzelius Bilin ; also fat, and a special colouring matter.
The folloAving is Berzelius's table of the analysis of ox-gall.
    Water       ...........904.4
    Bilin (with fat and colouring matter)......80.0
    Mucus............03.0
    Salts............12.6

                                                         1000.0
   According to Berzelius's view of the composition of bile, its essen-
tial and most  important constituent is the Bilin, a  substance Avhich
has  a   remarkable tendency,  under certain  circumstances, to be
metamorphosed into  taurine,  hydrochlorate of  ammonia,  and into
two resinous  acids, which  he  has named fellinic acid and cholinie
acid.
   Bilin is inodorous, and has a peculiar sweetish-bitter taste, most
perceptible at the base of the tongue and fauces.   This sweetness is
attributed by Berzelius to the admixture  of  some glycerine, Avhich
may be derived from the  fatty matters  of the bile.  It  dissolves
readily in water and in alcohol, but not in ether.  It is neutral, and
forms  soluble  combinations with acids and bases.
   The  substances above  named may  be  obtained from  bilin by
digesting  it in dilute hydrochloric acid.   The fellinic and cholinie
acids are  insoluble, the others  are soluble in water.
   Taurine is  a crystalline substance, consisting of colourless six-
sided prisms.   It  dissolves  in about sixteen times its Aveight of water
at 60°, and is more soluble at  a  higher temperature.  It contains
sulphur, according to  Redtenbacher.f   Its  composition is  repre-
sented  by the formula C4N2H406S2.   The fellinic and cholinie acids
resemble each  other very much in their external properties.   They
are little or not at all soluble in water, but are readily dissolved by
alcohol; the fellinic acid is readily  dissolved by ether, the cholinie

  * Untersuchungen uber die Galle, &c.  Frankfort, IS<7.
  ■j- Annalen der Chemie und Pharmacic von Liebig und AVohler, Feb., 1846. 
THE BILE.
599
 only slightly.   They form nearly similar compounds with the alka-
 lies,  earthy and metallic oxides ; but their salts of baryta  differ;
 the fellmate of baryta  being soluble  in  alcohol, the cholinate of
 baryta  insoluble.   The  product  called  by Berzelius dyslysin, is
 obtained by boiling these acids for a long time in hydrochloric acid.
 It is dissolved with difficulty in  boiling alcohol, and on cooling pre-
 cipitates an earthy powder.   Fellinic and cholinie acids have  the
 property of combining and forming acid  compounds with undecom-
 posed bilin ; these have  been named by Berzelius, bili-fellinic and
 bih-eholinic acids.
   According to Berzelius and Mulder, bilin begins to undergo these
 changes in the  gall-bladder of the living animal;  and it is, probably,
 this  proneness  to change on the part of its  principal constituent
 Avhich makes the analysis of bile so difficult, and gives rise to so much
 diversity of opinion among chemists.
   The fat of bile exists  partly in combination with soda, as oleate
 and margarate of soda, and principally as a peculiar substance found
 only in  bile and in the nervous matter,  namely, cholesterine.  This
 is separable from  the  other constituents of the bile by agitation in
 ether, which dissolves it ; from this solution it crystallizes in plates.
 It exhibits, when pure, the white crystalline lamellated structure of
 spermaceti,  from which  it differs,  however, in requiring a much
 higher temperature for its fusion,  namely 278°, and in not forming
 a soap with potash.   Its formula is C37H320.   Cholesterine  is the
 principal constituent of the gall-stones most commonly met with  in
 the biliary passages.
   The colouring-matter  of bile {cholepyrrhin, Berzelius)  is one  of
 its most  interesting constituents.   It varies in different animals, and
 perhaps  in the same  animal at  different times, according to the
 state of  health.   Like bilin it decomposes very readily,  and there-
 fore cannot be obtained pure; but it has been procured for analysis
 from the  gall-bladder, where it is sometimes deposited as a yellow
 substance  mixed with  mucus.  It is very sparingly soluble in most
 fluids; scarcely at all in  water, and very little in alcohol.  Its best
 solvent is a solution of soda or potass.  Such a solution,  containing
 the colouring matter of bile, becomes green  on exposure  to the ah°
 and on the  addition  of  an acid precipitates green flocculi, which
 possess all the properties of chlorophyll, the green colouring-matter
 of plants.   To, this precipitate Berzelius has given the name biliver-
 din.   The most remarkable  property of the colouring-matter  of
 bile is the play of colours Avhich  it is capable of producing  under
 the influence of a mineral acid, especially nitric  acid.   A little  of
 this acid, added to bile, or to  a fluid in which its colouring-matter is
 dissolved, as it often is, in urine, will change the colour  into blue,
green, violet, red, and  ultimately  brown, in  a  few seconds.   It  is
highly probable, as some  chemists affirm, that there exists a great
analogy between the colouring-matter of  the bile and  that  of the
blood: as there is also, most likely, betAvecn  these colouring princi-
ples and those of  nervous substance, skin, and hair.
  In addition to these constituents bile contains mucus in consider 
600
DIGESTION.
able quantity, to which probably is due its  peculiar viscidity.   It is
derived chiefly from the numerous mucous follicles in the bile-ducts,
and from  the mucous  membrane of the gall-bladder, and perhaps
also from  the debris  of the  hepatic cells after they have burst and
yielded up their  contents.  According to Berzelius, the mucus may
be separated by filtering the bile, Avhen a considerable portion of it
remains on the filter, and if  the bile Avhich  has  passed through be
subsequently subjected to  the action of alcohol, the remaining mucus
will  separate;  or it may be precipitated by the addition of acetic
acid.  It  is to  the  presence of this  mucus  in  bile that  Berze-
lius attributes the  metamorphic tendency  of bilin; and  he  affirms
that if fresh bile be deprived of its mucus, the bilin will continue un-
changed for a considerable time.
  Among  the  saline constituents of the bile Berzelius enumerates
the  following:  oleate, margarate, and  stearate  of  soda, with chlo-
ride of sodium, sulphate,  phosphate, and lactate of soda, and phos-
phate of lime.
  Such is the  view of the  constitution of bile put forward  by the
celebrated Berzelius,  and sanctioned  by  Mulder.   Berzelius re-
marks that the views which regard bile as a solution of soap, are so
far correct, as it contains a small quantity of soap dissolved in it.
  The most recent analysis of bile is that by Strecker, made under
the direction of Liebig, Avho denies the accuracy of Berzelius's vieAv,
adopting rather that of Demarcay, Dumas, Liebig, and others, that
bile is a solution of a salt of soda with  an  organic substance of an
acid nature, which is not a single acid, but a mixture  of a nitroge-
nous acid  free  from sulphur (cholic  acid), with a second acid, con-
taining both sulphur and  nitrogen (choleic acid).
   Use of the Bile, and Function of the Liver.—From the anatomy
of the biliary organs, as well as from  the  chemistry of the bile, we
learn that, before the venous blood of the  intestinal canal and the
spleen is allowed to reach the right  side of  the heart, a fluid very
rich in carbon  is eliminated from it, and poured into the duodenum.
The following questions suggest  themselves  respecting the  uses of
this fluid;  viz. :  is the bile simply an  excrement, like the urine? or
is it an excrement  Avhich  also serves some ulterior  purpose, such as
aiding the solution or digestion of the food in the boAvels ?
  The doctrine that the  secretion of bile  by the  liver, is merely a
mode of eliminating carbon from the system,  is strongly opposed by
the fact that in all the vertebrate classes the bile, instead of being
carried out of  the system by the most  direct  channel, as the urine
is, is made to pass  through nearly the whole intestinal canal, and to
mingle freely with its contents.  Moreover, the point at which it
enters the bowel always bears a pretty  definite  relation  to  that at
Avhich the pancreatic fluid is poured  into it.   Either these fluids
enter the boAvel together  through a common  opening,  as in man, or
the bile is poured in above, never below, the point of opening of the
pancreatic duct.
  These are capital facts, which must be  accounted for by an ade-
quate  theory of the  uses of the bile.   They indicate  that  the bile 
USE OF THE BILE.
601
has some use in promoting the changes of the food in the intestines,
or in contributing to the general process of nutrition in some other
way.  It is well known that an obstacle to the free admission of the
bile  into the intestinal canal is always followed by a greater or less
derangement of digestion, and by more or less emaciation.   But, as
these consequences might arise not so much from the want of a due
admixture  of bile with the food Avhich  is undergoing digestion, as
from the accumulation  of the elements  of the bile  in  the blood,
which must derange  all  the  functions  more  or less,  Professor
Schwann, of Louvain, tried  some experiments which  had for their
object to stop  the  flow of  bile into the bowel, and  at the same
time to provide for its excretion.  He tied the common bile-duct in
dogs, having first established an orifice of  communication between
the gall-bladder and the skin, through which the  bile  flowed out of
the  body as soon  as  it  was  secreted,  instead of passing into the
bowel.   It is plain that if the bile were merely excretory, such an
operation should produce no injurious effect upon the animal, as still
excretion was amply provided for.*
   Schwann found that of eighteen dogs operated  upon in this way
two only survived, and  in these the divided  bile-duct Avas found re-
established, and the bile had  resumed  its usual  channel.   Of the
remaining sixteen, ten died of the immediate effects of the operation,
and  the remaining  six lingered on for some  time, and  ultimately
died, without exhibiting any other cause  for  the fatal termination
excepting the absence of bile in  the intestinal canal.  These six
died at periods  varying  from  seven  days (in  a young dog)  to two
months and a half,  the average being two or three weeks after the
operation.   During  this time  they exhibited indications of a very
enfeebled nutrition,  emaciation, muscular weakness, unsteadiness of
gait, falling off of the hairs ;  symptoms which became more  deve-
loped the longer the dog survived the operation.   The emaciation,
indicated by a  deficiency of weight,  began  generally  on the  third
day from the operation.   When the dogs licked the bile as  it floAved
out of the fistulous  opening, and thus introduced it  into the stomach,
the digestion in that viscus was not impeded, nor were  the results
of the operation otherwise embarrassed, showing that it was capable
of being digested by the stomach.
  Blondlot  makes  an objection to  Schwann's experiments, that,
from  his mode of operating, the external opening is  apt  to close,
and thus the excretion of the bile is impeded and the nature of the
secretion altered.   He adopted a different operation, and provided
for the free discharge of bile  by inserting a canula  in the  wound.
A dog, treated  in this way, lived three months ; at first  he became
very thin, and lost strength ; but he recovered his  strength, but did
not completely gain his condition.  It appears, from a private com-
munication made by Schwann to Frerich,f that that  distinguished

  * Experiences pour constater si la Bile joue dans l'Economie Animale un Hole
essentiel pour la Vie.—Mem. de VAcad. Roy. de Bruxelles, an. 1844.
  + Art. Verdauung, AVagner's Handworterbuch.  This author Ftatcs that Nasse
operated on a dog in a similar way, and that the animal lived nearly six months.
       39 
602
DIGESTION.
Professor was  induced, by these  objections of  Blondlot, to repeat
his experiments, which he did to the number of thirty, and he took
the precaution of keeping a canula in the wound.  The animals
died as before,  but one lived a year, another four months ; immedi-
ately after the  operation they lost weight, but after a time the ema-
ciation  ceased, and  the dogs recovered, but  never  reached  their
weight previous to the operation.
   The results of  these  experiments denote that the bile cannot be
exclusively an  excretion, and, taken along  with  the facts already
referred  to, make strongly against this  doctrine.  But as the excre-
ments of all or nearly all animals, and  also the meconium, or the
feculent  matter found in the boAvels of the foetus in utero, contain
in certain proportion the elements of the bile, we are bound to infer
that a portion  of the bile  is throAvn out of  the system, along with
the refuse or undigested parts of the food.   And that only a portion
of it, and that a  small  one, is thus excreted seems evident, because
the quantity of bile  contained in the feces bears a very trifling pro-
portion to the amount secreted.   Thus, Berzelius found only 9  parts
bile in 1000 parts of fresh  human feces ;  if we take the average
quantity of  the  feces  expelled in  the day to be five ounces, this
would yield about twenty-one grains of dried bile, equivalent to 210
grains of fresh bile  ; but the lowest estimate of  the quantity daily
secreted by the liver is between six  and eight ounces, which exceeds
that of the feces  discharged.
   If, then, it be  admitted  that  only a  certain portion of the bile is
excrementitious,  it remains to inquire what  becomes of the remain-
der, and what  purpose it may serve ?
   Liebig suggests that it is absorbed from the intestine, and carried
into the circulation, where,  by  chemical union with the oxygen in-
troduced in respiration, it  forms carbonic acid, and  generates heat.
The liver, according to this  view, secretes from the venous  blood a
material, Avhich,  on  reabsorption, serves as food for the calorifacient
process.  It is not  likely that  this absorption takes place by the
veins, for if  so, we  should  find the secreted material carried back
again through the very same vascular  channels  from which  but a
short time previously it had been secreted; an arrangement which
has no parallel in the animal economy.   It is more probable, assum-
ing this view  to be correct, that the portion of the bile absorbed is
taken up by the lacteals ;  and if so, we should  have an  additional
indication that only a part of the bile re-enters  the circulation, for
if  the colouring  matter were absorbed by the lacteals it would be
readily detected  in the chyle.
   There are some striking facts which denote a connection between
the office of the liver and the calorifacient and  respiratory function.
 Thus, in the boa, although the liver is large, and no doubt secretes bile
freely, the excrements contain no trace of bile.   In this case, there-
fore, it must undergo complete  decomposition in  the intestine, or be
 entirely absorbed.   In carnivorous  animals, whose respiratory func-
 tion is very active, little or no bile is found in the excrements ; while
in those of  the herbivora,  which lead less active  lives,  and whose 
USE OF THE BILE.
603
food is more combustible in its nature, the  elements of the bile are
present in considerable quantity.
  According to this view, the bile would be in part excrementitious
and carried off in the feces; and in part recrementitious, inasmuch
as by its absoption into the blood it serves  to feed a process highly
important to general nutrition, namely, that of animal heat.  Still,
there seem strong grounds for supposing that it must serve yet
another purpose ; else why should the intestinal blood charged with
some of the combustible materials derived by absorption  from the
digested food  be subjected  to the action of the  liver  in  order to
yield a complex fluid, which is poured into the intestinal canal.   In
truth, we can  find no  explanation of  this remarkable  course of the
intestinal venous blood, nor of the situation at which the  secreted
fluid, the bile,  is discharged from the liver, but in the hypothesis
that the bile has some  function to perform in the intestinal  canal.
   This leads us to inquire whether the bile has any power of reducing
certain  elements of food which have been only partially or not at
all dissolved in the stomach.
   We  have as yet no satisfactory observations which lead to any
positive conclusion upon this point.  A series of careful experiments
as to the influence of bile upon  alimentary matters is much needed.
Hunefeld's experiments* on this subject tend to establish the gene-
ral fact that fibrinous  and  albuminous  matters  do seem to be dis-
solved under its influence at a  temperature equal, or nearly so, to
that of the blood.
   The connection of a gall-bladder with the  liver in  most animals
in which the bile accumulates until  intestinal digestion begins, evi-
dently associates the use of the bile with that process.
   Sir Benjamin Brodie advocated the doctrine that  the bile preci-
pitated the white chyle from the  chyme, and was  necessary to the
formation of  the former.   He  tied  the common choledoch duct in
young cats so as to prevent the passage of  bile into  the intestine;
and he found  that under these circumstances white chyle was not
formed, the lacteals being filled with a material apparently identical
with lymph.f   Tiedemann and  Gmelin  experimented  on dogs, and,
although they affirm that chyle was formed in the intestine (the
accuracy of which  statement must not  be completely relied upon
in default  of  microscopical  examination), yet they admit that the
contents of the lacteals in the dog  operated on  consisted of " a
transparent liquid, not white," while  in the dog not operated on it
was white.
  By our own  experiments we have ascertained that the formation
of white chyle took place, notwithstanding the closure of the com-
mon bile-duct,  provided the animal took a sufficient quantity of fatty
matter in its food.  When this was not attended to, white chyle was
not obviously formed.   But the  most remarkable effects of the liga-
ture of the common duct were the emaciation, loss  or capriciousness

               * Quoted in Valentin, Physiologie, b. i. p. 349.
               f Quarterly Journal of Science and the Arts, 1823. 
604
DIGESTION.
of appetite, and the general debility which immediately ensued upon
it.  Hence, although we  do not subscribe to the doctrine that the
presence of bile in the small intestines is essential to the formation
of white chyle, we readily believe that its exclusion from the bowels
retards and impairs digestion.
   When the biliary duct is obstructed, and the bile does  not pass
through its ordinary channels, the organs which suffer most disturb-
ance in their functions are the kidneys; as if, when the liver fails in
its action,  these organs took on the work of eliminating  a certain
portion of  the bile.   They secrete urine  loaded with the colouring-
matter  of  the  bile; and, at the same time, lithic acid, or  lithate of
ammonia, or purpurate of ammonia (muroxid), is formed in consider-
able quantity.   In  cases  of jaundice from  obstruction, so  long as
plenty of bile, or its colouring principle, appears in  the urine, and
a  normal  quantity  of  urine is  secreted, no very serious  symptoms
arise;  but as soon as the kidneys fail, then indications  of poisoning
either  by bile or urea, or  both, arise, and the patients die in a coma-
tose state.
   It is worthy of remark that  the hepatic cells contain more or less
of oily fat: and that under some circumstances this fat accumulates
in them to a great extent, so as  to occasion enormous  enlargement
of that organ.   And in some fishes the liver is naturally, at certain
periods, loaded Avith it.  It is a point of great interest to determine,
whether this fat simply accumulates in the hepatic cells, as it does in
other tissues, or whether  it may not  be regarded as a part of the
secretion of the liver;  in  other words, can it be a part of  the office
of the  liver to recombine  certain elements of the  absorbed  food, and
to form fat, which, on being discharged into the  intestinal canal, is
absorbed by the villi ?*
   In connection with  this subject we  may refer here  to a remark-
able fact lately brought  to light by Bernard, which denotes that
chemical changes take place in the blood while it is passing through
the liver, whereby a material is generated in it which had not been
introduced in the food.
   Bernard has found that  sugar is developed in the hepatic capil-
laries,  even when it is not present in the intestines, or in any of the
tributary veins of the vena portae.   A dog, which had been fed some
hours previously on substances destitute of starch and sugar, was
quickly killed,  the  abdominal  cavity was immediately  opened, and
ligatures  were  placed  on  the  mesenteric, splenic,  and pancreatic
veins, and  on the  trunk  of the vena  portse.  Blood collected from
each of these sources,  on  the  distal side of the  ligature, proved on
examination destitute  of  sugar in all, except the vena portae, in
which it was readily detected.    Sugar was also  found in the tissue
of the  liver itself.   If, then, sugar exists in the vena portae, but not
in its tributary veins,  how does it get to the former  ?  As it exists

  * It is true that the fatty matter of the bile is not free; but it may be  supposed to
form its combinations after it has been discharged from the hepatic cells,  and while it
is passing through the ducts of the liver. 
USE OF THE BILE.
605
in the tissue  of the liver, it is evident that it passes to the vena
portae by the  reflux which, in  the  absence of valves  in  the  portal
system, may take place after death.   Hence it is reasonable to infer
that sugar is formed in the hepatic capillaries, and carried by the
hepatic veins to the right side of  the  heart, in the blood of  which
Bernard states  that sugar is constantly present, whatever food the
animal may have been fed on,  and  even after a long fast.
   The evidence of the presence of sugar in the liver  is obtained in
the following manner:  a  portion of the liver is  beaten in a mortar,
and then  boiled in a small quantity  of water, and  filtered.  The
filtered liquid possesses all the properties of a saccharine fluid ;  it
becomes  darker on being boiled with liquor potassse, and the addition
of the tartrate of potass  and copper  causes a precipitation of the
brown oxide of copper.   Yeast added to it  at a certain temperature
causes fermentation; and alcohol may be obtained from the fermented
fluid by distillation.
   There can be no doubt, then, that  sugar is formed in the capil-
laries of the liver independently of the food; it  is equally certain
that fat is separated at  the same point, for it appears in the hepatic
cells; this, too, is doubtless the result of chemical changes in the
hepatic circulation, independent of the food, because we find good
grounds  for concluding that the fat  of the food, emulsified by the
pancreatic fluid, is absorbed by the villi, and does not  reach the
liver.
   Thus are formed in the laboratory of the liver these two products
—fat and sugar, very nearly allied in  chemical constitution.   The
former is carried into the intestine  with the bile, and there absorbed,
with the  fat of the food, by the  villi.   The latter is carried by the
hepatic veins to the right  side of the heart, and thence to  the lungs ;
and  both appear to be formed by the  liver, whether they have ex-
isted in the food or not.
   What, then,  it may be  asked, can be the object of the formation
of these  products by the liver?  If it be  to feed the calorifacient
process, then the additional question arises, why should each pass to
the right side of the heart by a different route?
   It seems to us that there is in these  arrangements distinct indica-
tion of a provision for the  slow  and gradual transmission to the lungs
of these carbonaceous elements; in  order to guard against the blood
in these organs becoming  surcharged by them so as to  interfere with
the due introduction of  oxygen.
   It seems necessary for  health  that the blood should be supplied,
on the one hand,  duly, but gradually, with carbonaceous matters,
such as sugar  and fat, and, on the  other hand, with oxygen ;  when
the former elements are deficient,  fever is the result, the elements
of the tissues are consumed by the  devouring element, oxygen ; and
hence it is that we often see such striking  results from the gradual
introduction of alcohol,  or other  carbonaceous matters, into the
system;  but  when the latter  element is  deficient, the great vital
changes of the blood are  delayed,  or suspended, and  death rapidly
ensues.  And  in  the various  diseased states of the body there are 
606
DIGESTION.
infinite shades  of  difference, as regards the supply,or the defect of
these great elements ;  either too much carbon or too much oxygen ;
or the one is normal in amount, while the other is deficient.  A com-
mon result of the too  ready assimilation of carbonaceous matters,
or the too rapid formation of them, is the deposition of fat in various
parts of the body, sometimes to the augmentation of its bulk by an
increased development of the  adipose tissue, at others, to the pro-
duction of various abnormal deposits, containing more or less  fat, as
atheroma.
   In conclusion, the following propositions will  serve to  exhibit at
a glance  all that we may, in the present state  of our  knowledge,
affirm respecting the function of the liver:—
   1. That it secretes a highly complex fluid, which  is poured into
the intestinal canal, and there undergoes decomposition.   Its colour-
ing-matter (cholepyrrhin, or biliverdin) is carried off in  the  excre-
ments, and may possibly  assist in  stimulating the  action  of the
intestine.  Its  fat is in great  part, at least, absorbed by the villi.
So much of its fat as is not  thus acte,d upon  contributes  to form
the  feces.    Its salts,  also, are probably carried off in  the  feces.
Other of its  elements  contribute to  the  digestiAre process, by pro-
moting the solution in  the bowels of some kinds of food which have
escaped the solvent action of the gastric fluid.   What these elements
are,  and  Avhat kinds of food they serve to dissolve, we have  yet ac-
curately  to determine ; it seems certain, hoAvever, that it exercises
no solvent power over fatty or oily matters, and probable, that  it
acts upon azotized matters.
   2. The liver forms  sugar and  fat  by chemical  processes  in  its
circulation, independently of any direct  or immediate  supplies of
these substances in the aliments.
   3. The liver is  a great emunctory ;  it  eliminates carbonaceous
matters,  some directly, as the colouring-matter  of the bile, which is
at once thrown out in  the feces ; others indirectly, as fat and sugar,
which, passing to  other parts  of the  circulation, are more  or less
acted on by oxygen and eliminated as carbonic  acid and water.
   4. The  liver contributes largely to the  maintenance  of general
nutrition; first, by aiding in the solution of  certain aliments  in the
intestinal canal, and secondly, by furnishing food to the calorifacient
process.
   Before we leave this subject, we must refer to  the  remarkable
observations of Weber,  confirmed by Kolliker, respecting the  ex-
tensive generation  of  blood-corpuscles in the liver of the embryo,
which have led the former physiologist to form the opinion that "not
only is the liver an organ for secreting bile, but that in it a material
is separated and accumulated from  the  blood,  out of which  blood-
corpuscles are formed, which are taken, off by the bloodvessels, while
from the residuum the bile is formed, which is conveyed away by the
biliary ducts."
   During the latter days of  incubation of  the  hen's egg, the liver
assumes  a completely yellow  colour, instead of the  reddish-brown
which it  had previously.  This is connected with the rapid  absorp- 
USE OF THE BILE.
607
 tion of the yelk, probably by the bloodvessels of the yelk-sac, which
 carry it to the liver, where it finds  its way from the bloodvessels into
 the fine gall-ducts, which at this time  are full of particles exactly
 the same as the yelk-globules.  These  particles are not carried into
 the intestine  along the biliary passages, but  undergo a change  by
 which,  on the one hand, blood-corpuscles are formed and pass into
 the bloodvessels, and, on the other hand, bile is generated and carried
 off by the ducts.
   "Y\ eber states that he has observed a similar phenomenon in the
 liver of the frog in the spring of the year, when  the sexual organs
 are highly developed, and when the  lymphatic system is in a highly
 active state.  The liver undergoes a change of colour from reddish-
 brown  to greenish-yellow.   It is  covered with dark pigment-cells,
 and contains numerous opaque masses, which probably consist of the
 colouring-matter of the  bile, which  may  have accumulated during
 the winter, but  which now undergo gradual solution and pass off in
 the bile.   The peculiar colour which characterizes the liver at this
 time, in the frog, is resident, as with the chick, neither in the blood-
 vessels nor in the hepatic cells, but  in the minute ramifications of
 the gall-ducts, which are filled with  numerous small globules  con-
 taining fatty particles.   These undergo the same metamorphoses as
 those of the chick into blood-corpuscles.
   This highly interesting subject requires further investigation—to
 ascertain whether similar  phenomena may  be  noticed in other
 animals, as in intra-uterine life in  Mammalia—or  in hybernating
 animals—or whether, indeed, they may not be  constantly occurring
 in adult animals, although with less activity than  in the young.
   The question  occurs to us, may the liver be a source of supply of
 blood-corpuscles, or may it contribute to the production of haematine
 in adult life ?   It has often  struck us  that this question  might  be
 answered in the affirmative,  while observing cases in which the  pro-
 cess of the formation of  blood seemed  greatly perverted,  where  no
 organic disease could be  detected beyond some degree of enlarge-
 ment of the liver.   Patients  suffering  in  this way are  pale, as if
 from loss  of blood, although no such loss had been  experienced;
 their nutrition is enfeebled,  digestion impaired, and there is slight
 yellowness of the complexion, as in cases of hepatic disease, and
 after  death no lesion is discoverable,  but slight enlargement  of the
 liver.*
   We  have already remarked  that the venous blood of the  spleen
 passes along with that from the stomach and  intestines through the
 liver.  Recent researches of Kolliker and Ecker offer some expla-
 nation of  this fact, and  at the same time of the relation  betAveen
 hsematine and the colouring matter of bile, as well as between the
office of the liver and the generation of the red particles of the blood.
It would appear from these researches, which will  be detailed when
we come  to treat of  the  spleen,  that the  red blood-corpuscles
undergo decay in the  red substance of the  spleen, giving up their

  * Kolliker uber die Blutkorperchen der Menschlichen Embryo und die  Entwick-
elung der Blutkorperchen der Saugethieren. 
608
DIGESTION.
heematinc in an altered form to the portal blood, from which it may
not improbably, as Kolliker conjectures, pass into  the  bile-cells to
form, and to be  eliminated as  the biliary colouring matter;  and,
perhaps, also to  contribute to supply heematine  to new blood-cells
developed in the liver.*
   Of Digestion in the Large Intestine.—The contents of the large
intestine, which constitute the feces, properly so called, differ much
from  those of the small intestine.  Generally, and in the  normal
state, they are  more solid, more  homogeneous, exhibiting  a certain
form, which is determined by the size and  shape of the cells of the
colon.  These  characters  are more marked  the further  the feces
have advanced in the colon.
   The changes, upon which depends the difference of character of
the contents of the large  and  small intestine, commence  in  the
caecum.  Many facts lead to the opinion that the intestinal contents
undergo  some further digestion in  the caecum, analogous  to that of
the stomach.  Schulz affirms that an acid fluid  is secreted by the
mucous membrane of the caecum,  which is more distinct in herbivora
than in carnivora;  Bernard and Blondlot state  that the acidity of
this fluid is due to the presence of lactic acid.f  In dogs, we have
found that litmus applied to the  surface of the csecal mucous mem-
brane became  reddened in some,  but not in others;  a  difference
probably depending upon some peculiarity in the food or the time of
digestion.   The remarkable  development of the  caecum in some
animals as compared with others, denotes that it must exercise some
special function.   In herbivora, its size is especially large; in carni-
vora, it is small.  Moreover, the  mucous  membrane of the caecum
resembles in structure  that of  the stomach, and  is supplied  with
glands like the solitary glands, which pour out an abundant secretion.
   No material change takes place in the feces as they pass through
the large intestine, excepting such as is  produced by the absorption
of  fluid  from  them by the mucous  membrane.   Thus  the feces
become drier the longer they remain in the bowels.
   Defecation.—The contents of the large  intestine  are  pushed
onwards by a vermicular action, essentially the same as that of the
small intestine.   Propelled thus in successive portions, they accumu-
late in the rectum, whence  they are prevented from escaping by the
contraction of  the sphincter.   The act of 'expulsion  of  the feces
from the rectum, the  act  of defecation,  is effected partly by the
contraction of  the muscular fibres  of the rectum, excited by the
stimulus of  distension, and partly by the contraction of the abdomi-
nal muscles and of the diaphragm, which, by reducing the size of the
abdominal cavity, and compressing the intestinal canal at all points,
greatly assists the detrusive efforts of the rectum itself.
   Within certain limits the act of defecation is  favoured by the
bulk  of  the intestinal contents.   When the  rectum is moderately
distended, and  its inner surface sufficiently lubricated by mucus,
defecation is effected Avith but little aid from the abdominal muscles,
and mainly by the expulsive force of the rectum, which is sufficiently

  * Cycl.  Anat. and Phys.; art. Spleen.        f Gazette Med. de Paris, 1844. 
THE FECES.
609
strong to overcome the passive contraction of the sphincter.  If the
contents of the rectum  be too bulky, they occasion over-distension
of the gut, and diminish its contractility.  Under such circumstances
immense accumulations may take place;  and, as small portions may
continue from time to time to be expelled, under the influence of the
abdominal muscles, the practitioner may thus be deceived as to the
real nature of  the case.    On the other hand, when the feces do not
accumulate in  the rectum in sufficient quantity to distend the rec-
tum, the  act of defecation is rendered  difficult  by  the  imperfect
actions  of the  rectum itself, and great efforts  are  required on the
part of the abdominal muscles, which often cause the protrusion of
portions of the mucous  membrane  near the  anus.  Under  these
circumstances  it is  that  enemata  act  so favourably, by giving the
gut its  natural stimulus, that of distension.   The action of the ab-
dominal muscles in defecation is  chiefly voluntary, but partly reflex.
If the rectum  be the seat of irritation, as in dysentery, the  reflex
action is  much increased, and the repeated strainings which  occur
during the act  of defecation in this disease are, in a great  measure,
thus caused.
   The ordinary expulsive actions of the rectum  are due  simply to
the stimulus of distension acting upon the circular muscular fibres.
When the mucous membrane is irritated, as under the influence of a
purgative, or in diseased  states, the action of  the rectum takes on
the character of a reflex act, excited by the  contact of the  feces
with the irritable mucous membrane.
   The quantity of the feces  is determined  partly by the  quantity
and  quality of the food,  partly by the  quantity of the secretions
poured into the canal-.  If the food exceed much what the aliment-
ary canal can reduce and  absorb, the quantity  of feces  will be con-
siderable.  Vegetable food produces a greater amount of feces than
animal,  because the former is eaten  in  greater  quantity  than the
latter, and because it contains much that is incapable of  reduction
in the stomach  or bowels.   The feces of carnivora are always  abso-
lutely and relatively smaller in  quantity than  those of  herbivora.
And those tribes  of mankind who feed chiefly  on vegetable food
make large quantities of feces.
  The ordinary quantity of feces passed daily  by men in  health, is
about five or six ounces; so that, if we assume  thirty-five  ounces as
about the  average quantity of food taken in tAventy-four  hours, it
may be  inferred that  at least thirty ounces are appropriated to the
various purposes of the economy.
  Berzelius's analysis of feces gives the following result:—
Water
Matters soluble in water: Bile  .
                    Albumen
                    Extractive
                    Salts .
Insoluble residue of the food
Insoluble matters derived from the intestinal canal, as mucus,
  biliary resin, fat, and a peculiar animal matter    .    .   14.0
73.3
0.91
0.9 I    g -
2.7 j    5-7
1.2J
   .   7.0
100.0 
610
DIGESTION.
  The ashes of human feces yield, according to Berzelius and Ender-
lin, chloride of sodium, sulphate of soda, tribasic phosphate of soda,
phosphate and sulphate of lime, phosphate of magnesia, phosphate
of iron, and silica.   The  nature and  quantity of these salts,  how-
ever,  vary with the quality of the food.
  A remarkable  property of the feces  is their peculiar odour.  Upon
what  this depends has not  yet been satisfactorily ascertained.  It
seems very doubtful that it can depend on any decomposition of the
bile ;  for under certain circumstances, when bile is  deficient or ab-
sent,  the fetid  odor of  the discharges from the bowels  becomes
greatly increased, as  in  jaundice  from  obstruction,  and Asiatic
cholera.   It is not improbable  that some of the intestinal glands
may secrete a peculiar  odoriferous principle, which may be  modified
by the bile.  Peyer's glands may perform this office ;  and this idea
derives support  from  the fact  that in  certain cases  where these
glands are  diseased,  as in fever and phthisis, the  fetor of the  feces
is increased considerably.
   Certain gases  are generated  in the  course of the intestinal canal.
These are partly set free  during the changes which  the alimentary
matters  undergo in  the intestine ;  and partly they are products of
secretion from the mucous  membrane.   They  consist of  carbonic
acid,  hydrogen, carburetted and  sometimes sulphuretted  hydrogen,
and nitrogen.  A  certain quantity of these gases seems,  by its dis-
tending  action, to favour the  vermicular  movement of the bowels,
and so to  promote the passage of their contents.   Within certain
limits, therefore, the formation of gases in the bowels may be pre-
sumed to  favour health ; but  it is well known that under the  in-
fluence of emotion, or of irritation, or  of certain kinds of food, gases
are generated in  the  stomach, as  well  as in the intestines, to  an
enormous  extent.  Tympanites shows itself in  hysteria  under the
influence of strong emotion ; and sometimes a few minutes will suf-
fice  to generate  a quantity of gas sufficient  to distend the whole
canal.  Also, in fever, the formation of gases in the intestines is a
prominent symptom, giving rise to that state of meteorism which is
known to be an unfavourable sign in that  disease.

  On  the  subjects discussed in this chapter,  the reader is referred to  the  list of
writers at the end of the last chapter, and  to those quoted in the foot-notes ;  also to
the following:  Berzelius,  art. Galle, in Wagner's Handworterbuch; Bernard, du Sue
Pancreatique, &c, Arch.  Gen. de Med. 1849;  Bernard, de l'origine du  sucre dans
I'economie animale, i\rch. Gen.  de Med. 1848, and translated in  Ranking's Abstract
for 1849.  French's art. Verdauung, in Wagner's Handworterbuch, a most able essay,
which did not reach us until this  chapter had  been some time in type; Bouchardat
and Sandras, Comptes  Rendus,  1845;  Dr. Allen Thompson's paper on the Intestinal
Glands, in Goodsir's Annals  of Anatomy and Physiology.  Part i. 1850. 
ABSORPTION.
611
                        CHAPTER XXVI.

OF ABSORPTION.—EXAMPLES.—ANATOMY  AND  DISTRIBUTION OF  THE
  ABSORBENT VESSELS AND GLANDS.—ORIGIN OF THE ABSORBENTS.—
  PROOFS OF ABSORPTION.—CONTENTS OF THE ABSORBENTS.—ANALYSIS
  OF CHYLE AND LYMPH.—THEIR  QUANTITY.—MECHANISM  OF  THE
  ABSORBENT PROCESS.--THE INFLUENCE OF THE QUALITIES OF  THE
  FLUIDS.—OF THE POROUS  SOLIDS.—OF PRESSURE.—OF MOTION OF
  THE FLUID WITHIN THE  VESSELS.—CONCLUDING OBSERVATIONS ON
  THE FUNCTION OF THE ABSORBENTS.

  The function  of absorption is universal in organized bodies, as
they all  live and grow by  absorbingi suitable material from without
and making it  a part  of  themselves.   All  the  tissues are more or
less porous, and capable  of absorbing fluids brought into contact
with them.   The cuticle of the hands soaked in water become soft
and SAVollen from  the imbibition of that fluid, and if a soluble salt
be added to the water, this salt  may, ere long,  be  detected in dis-
tant  parts  of the  body by its appropriate tests; showing that the
foreign substance  has penetrated  within the cuticle  so as to reach
vessels capable of  diffusing it throughout the frame.*  In the same
way soluble substances taken into the mouth, and brought into contact
with the alimentary mucous membrane, are rapidly  absorbed,  either
immediately, or after having been first changed and adapted for ab-
sorption by the processes described in the preceding chapters.    In a
similar way gases or fluids effused or injected into the cavities or inter-
stices of the body may be gradually taken up and removed, as we see in
cases of emphysema,  of ecchymosis, of dropsy, of inflammatory pro-
ducts, &c.   An absorption of the tissues themselves is also constantly
going on, as a necessary part  of their nutrition—the old materials
being taken away when no  longer suited for the purposes of life.
When the effete  matters of the tissues are thrown off from the sur-
face of the  body,  or from glands  which are,  in fact, a portion of
that  surface, they are said to be secreted; when they re-enter the
circulation for a time they may be rightly said to be  absorbed.  In
certain cases, entire  organs Avaste Avhen the term of their  usefulness
has expired, e. g.,  the mammary and spermatic  glands, and all the

  * Mr. Erichsen took advantage of  a case of extroversion of  the bladder to  expe-
riment on the  rapidity of absorption under different circumstances, as  indicated by
the presence in the urine of the absorbed substances.  The following are some of his
results. Priissiate of potass taken into the stomach, after a fast  of eleven hours, may
be apparent in the  urine in one minute ;  but if immediately  after a meal, not till
thirty-nine minutes.  Vegetable infusions required more time for passage through the
system.  Galls, uva ursi, madder, rhubarb, logwood, &c, passed  in from sixteen to
thirty-six minutes, according to the time  after a meal.  Citrates and  tartrates  of
potass and soda rendered the urine alkaline in from thirty-six to forty-eight minutes.
When the feet  were immersed in a pail of water containing three ounces of acetate of
potass in solution, the  urine  became alkaline in sixty-seven minutes; but no  effect
seemed to be produced  when a solution of citrate, tartrate, or prussiate of potass was
employed (see Med. Gazette, June, 1845). 
612
ABSORPTION.
organs, even the bones, tend to atrophy in advancing life.  Again,
periodical absorption of the materials of certain organs occurs,  as
in the testes of birds and other animals after the annual season of
impregnation, but perhaps the  most remarkable example of absorp-
tion belonging to this head, is that of the fat which is stored up in
large quantities in the bodies of hybernating animals, and gradually
disappears during the winter  torpor, probably to  furnish materials
for the generation of warmth.
   These general observations will suffice to  show the importance
of the subject of absorption.   We  are led to it, at the present stage,
by having to consider the  mode in which  the materials introduced
into the alimentary cavities are conveyed thence to  mingle  with
and form part of the common mass of the circulating fluid.  But
we may conveniently treat of the  process in  general in the present
chapter.
   The coats of the intestine are found to contain two sets of vessels,
one through Avhich blood circulates, from arteries to veins through
the capillary network, the  other containing a  milky or transparent
fluid, chyle  or lymph, which  finally reaches  the  blood.   Both  of
these kinds  of vessels are the agents of  absorption, and both proba-
bly'share in receiving the  alimentary matters through the mucous
lining of the canal, but in the  present chapter the structure of the
latter will be chiefly considered, and that of  the  bloodvessels de-
ferred.   Together with the lacteals, the lymphatics will be also de-
scribed.
   The lacteals and lymphatics together form  one system of vessels,
which  takes its rise in  the midst of  various organs of the body,
and conveys a fluid into  the  veins near their termination  in the
heart.   The lacteals constitute that portion  of this great  system
which originates  in  the digestive mucous  membrane, and they are
undoubtedly concerned in the absorption of  a part at  least of the
nutrient matters of the  food—their contents (chyle) after a  meal
being  of a milky  appearance—whence  their  name,  vasa  lactea,
given to them in 1622 by their discoverer, Asellius.  The lymphatics
(and the lacteals during fasting) contain a pellucid fluid—the lymph.
   The lacteals originate in the mucous  membrane of the intestines,
especially in the villi, and form a  network with close meshes in the
submucous areolar tissue.   There are also more superficial ones be-
tween  the peritoneum and muscular coat, which take  a more longi-
tudinal course, and join the others on  the mesentery.   They then
pass in great numbers betAveen the layers of the mesentery towards
its root, anastomosing with one another and traversing  glandular
organs, the mesenteric glands, in  their  way to the right side of the
aorta,  Avhere they all finally discharge themselves into an  elongated
pouch common to them and to the lymphatics of the parts below—
termed the  receptacuhtm chyli.   From  this the thoracic  duct leads
upwards to  the left  subclavian vein.
   The receptaculum is usually from an  inch  to an inch and a half
in length, and from  a quarter to three-eighths  of an inch in diameter.
The thoracic duct,  Avhich  is  continued upwards from it, lies  in the 
THE ABSORBENT VESSELS.
613
 chest between the aorta and vena azygos, then inclines behind the
 arch of  the aorta to the left side, and  empties itself into the upper
 and back part of the left subclavian vein close to the internal jugular
 vein, its  orifice being  defended by two valves.   The thoracic duct
 is about an eighth  of an inch  or more wide, becomes more narrow
 up to the sixth dorsal vertebra, and again dilates opposite the third.
 It  frequently divides into branches which  reunite—and sometimes
 opens into the subclavian vein by two or even three separate trunks.
   The lymphatic vessels of the  upper  and  lower  extremities form
 two sets, a deep  one accompanying the deep  bloodvessels, and a
 superficial one running in the deeper layer of the superficial fascia.
 These sets anastomose and pass in common to the trunk by the groin
 and axilla, where numerous glands occur upon them.  (1) Those of
 the lower extremities, after passing under Poupart's ligament, follow
 the great bloodvessels,  are joined by others from the pelvis, loins,
 and abdominal walls and  viscera, and  open into the receptaculum
 chyli by from four  to six large trunks.   Very numerous glands suc-
 ceed each other in  their course, forming an irregular chain.  The
 thoracic duct  is joined by lymphatics from the left side of the walls
 of  the  chest, and  from the heart and left lung,  on all of which
 many glands_  occur; and  as it empties itself into  the  great vein,
 the lymphatics  of  the  left upper  extremity, and  left side of the
 head and neck come  to meet it.   (2) The lymphatics of the right
 side of the chest, of the right arm, and of the right side of the neck
 and head, crowd towards  the junction of the right subclavian and
 jugular veins, and open into  the  former,  usually by a large  but
 short trunk.   The  number of lymphatic glands in  the whole body
 may be estimated at from two to three hundred, or even more.
   In general,  but especially in  the limbs, the lymphatic vessels form
 many trunks of equal diameter,  taking the same direction, and join-
 ing, and again dividing irregularly, without altering their size.   In
 all  this they differ remarkably from the  ordinary arrangement of the
 sanguiferous vessels.
   The absorbent Vessels differ from the  bloodvessels  in the delicacy
 and semitransparency of their  coats, which allow the nature of the
 contents to be seen through them ;  the  white colour of the chyle in
 the lacteals or mercury artificially thrown in, is at once visible from
 the outside.  When the vessels are filled we observe many constric-
 tions, depending on the existence of valves ill the interior, so placed
 as to prevent a retrograde flow of the chyle or lymph.  These valves
 are closer together  in some parts than in others.  In general, they
 are further apart in the narrower vessels, but in the thoracic duct,
 the largest of all,  they are unfrequent.  They are usually closest
 set  in vessels  of medium size, i. e.,  in those of from TT3 to T7g  of
 an  inch  diameter, but they are  not so  near to one another in the
lymphatics of  the upper extremities,  and the head  and neck, as in
those of the lower  limbs.  Besides occurring in succession in the
course of the vessels, they are almost always found at the origin or
termination of branches, and also where the lymphatics empty them-
selves into the veins. 
614                         ABSORPTION.
 A. Longitudinal wavy fibres on the inner surface of
the contractile transverse fibres of the thoracic duct of
the horse—Magnified 80 diameters.
 B. Stratum of nucleated epithelial cells lining the
lymphatic vessels.—From a large lymphatic on the
trachea of a horse.—Magnified 320 diameters.


               Fig. 170.'
   The absorbent vessels have a proper coat, an  outer investment of
areolar tissue, and an  inner lining of epithelium.   (1) The proper
coat is formed chiefly of circular fibres, relatively most abundant in
                                        the smaller vessels, analogous
               Fig-169-                  to the contractile tissue of the
        b               A             bloodvessels,  and a  modifica-
                                        tion of the  unstriped muscle,
                                        containing  elongated  nuclei.
                                        On  the inner side  of the cir-
                                        cular fibres  are longitudinal
                                        fibres, more  resembling white
                                        fibrous  tissue (Fig.  169, A).
                                        (2)  The  fibres of the  areolar
                                        coat have an  irregular  course,
                                        and blend  with the neighbour-
                                        ing tissues.   This coat  allows
                                        of   slight  movements  of the
                                        vessel, and contains the blood-
                                        vessels which ramify in con-
                                        siderable   abundance on  the
                                        proper coat.   (3) The  epithe-
                                        lial lining consists  of a single
                                        layer  of  extremely  delicate
                                        nucleated  particles,  first no-
                                        ticed by  Henle.    They are
                                        usually  spindle-shaped,  and
                                        fitted sideways  to  each other
                                        (Fig. 169, B).
                                          The valves (Fig.  170, C) are
                                        formed by a process of fibrous
                                        membrane  standing off  into
                                        the  vessel,  probably with a
                                        covering  of  the   epithelium.
                                        They are mostly in pairs, of a
                                        crescentic  shape, the  convex
                                        edge attached,  the  concave
                                        free, and when  in  action con-
                                        stitute a  perfect barrier, the
                                        wall of the vessels  immediate-
                                        ly  above  them being bulged
                                        into a sinus,  so  as  to give the
                                        canal  a  beaded  appearance
                                        when  distended.  Mr.  Lane
                                        has observed that some of the
                                        valves are single and circular,
                                        with  a  central perforation,
                                        and therefore  incomplete—
                                        while  others  are unequal  in
                                        size.
 A. One of the inguinal lymphatic glands injected
with mercury, a. Afferent lymphatic vessel from the
lower extremity,  b. Efferent vessel.  Others are also
seen.
 1$. One of the superficial lymphatic trunks of the
thigh.
 C One of the femoral lymphatic trunks laid open
longitudinally to display the valves within it.  c. Sinus
between the valve and the wall of the vessel,  d.  Sur-
face of one valve, directed towards the opposite, e.
Semicircular attached margin of the  valve.—After
Mascagni. 
STRUCTURE OF THE ABSORBENTS.
615
   Contractility of the Absorbent Vessels.—This depends on the con-
tractile tissue of their proper coat.   The  property may be demon-
strated by mechanically irritating a large vessel, such as the tho-
racic duct, in an animal just killed—it undergoes slow contraction.
The absorbent vessels  continue to propel their contents, even when
the current from the primary networks is arrested  by pressure, and
this they seem to  do by their  vital contractility.  As the contents
advance  the  vessels diminish in  diameter.   It is  usual to find the
lymphatics empty and collapse some time after death.
   The lymphatic glands are, for the most  part, flattish oval bodies,
of firm consistence and light  colour,  situated in  the course of the
lymphatic and lacteal  vessels, these vessels being styled afferent as
they enter the gland,  and efferent as they leave  it.. The glands
vary from  the size of a millet-seed to  that  of an almond.  They
usually lie loosely in the areolar texture, well protected from injury
ty their mobility, and if near the surface of the body, by the dispo-
sition of the  neighbouring bones or muscles.   They have a firm but
delicate proper capsule, which is  continuous with  the outer coat of
the vessels, and which sends processes  inwards upon the bloodvessels
and lymphatics which penetrate the glands.
   The general structure of these glands has long been known, being
well displayed by mercurial  injections (Fig.  170, A).  This metal,
when  thrown into  an  afferent vessel, shows  that this divides into
minute branches, most of which spread out  over  the  gland before
entering it, and that the efferent vessels have a similar arrangement
on the opposite side.   The  mercury readily fills the entire gland,
and escapes by the  efferent vessels.  The surface of the gland, when
occupied by mercury, exhibits either a very close plexus of tortuous
minute vessels, or else a congeries of apparent cells; and while there
has been  no  doubt of  the continuity of the  internal tracts of the
gland with both the afferent and  efferent  vessels, the  question has
been  discussed, whether these  tracts  are simply convolutions  of
tubes,  or cellular lateral offsets from  channels traversing the gland
in a more direct course.  Both of these views may possibly  be true
in different cases,  or  probably the convoluted vessels  of the gland
may be themselves dilated at intervals into  cells which,  from their
mode of package, may simulate detached cavities, as in the well-
known arrangement of the vesiculse seminales.  In confirmation of
this last view it may be observed, that the tracts  of the gland are
usually more  capacious than  the  ramifications of the afferent and
efferent vessels which immediately communicate with them.
   A more  important question concerns the  changes in the tissues
forming the walls of the afferent vessels on their entrance into the
gland, and this has been ably illustrated by Professor Goodsir.  He
describes the  outer areolar coat as passing to form the capsule of the
gland, and the proper coat to  become extremely thin, especially in
the deeper parts  of the gland.   The  epithelium, however,  becomes
thicker and more opaque, so as often no longer to transmit the light
under the microscope, and by the  action of  acetic acid very nume-
rous nuclei are disclosed in  it.  He describes the elongated nuclei 
616
ABSORPTION.
in the  substance  of the (proper) membrane on which  this modified
glandular epithelium rests, and appears to consider that the  epithe-
lium is in constant decay and renovation, being shed as a secretion
into the cavity of the ducts,  to  mingle with and modify the passing
lymph.*
   From the examinations we have made of the recent glands of the
loAver mammalia,  we are  disposed to  agree in most particulars with
this  description.   The very delicate  simple layer of  transparent
nucleated cells lining the lymphatic  vessel ere it enters the gland,
becomes in the gland a very  thick and rather opaque granular mass
loaded with  nuclei, in the   debris of which are  apparent a great
abundance of nucleated cells of different sizes, many of them pre-
cisely resembling the white or colourless lymph-corpuscles presently
to be described.  We lean strongly to  the opinion  that these cor-
puscles are set free to a  large  amount, though, perhaps, not exclu-
sively, from  the surface of the intra-glandular  passages.   The
structure of the lymphatic glands offers many difficulties to the ana-
tomist, and  there can be little  doubt that further research would
discover peculiarities as yet undetected.
   The lymphatic glands are  well supplied with blood.   The arteries
and veins derived from neighbouring  sources subdivide  together on
the surface, and penetrate between the ducts, carrying in with them
for some distance a sheath  derived from the  capsule.   The capil-
lary network  is probably spread out on the exterior of the ducts,
i.  e.  in the interstices of  the plexus which these form  in the gland;
but it cannot be said that the exact relation of the bloodvessels to
the abundant granular matter of the  ducts has been as yet unequi-
vocally demonstrated.  The  capillaries are very fine, their meshes
large, and they anastomose throughout.
   In injections of the ducts  of the glands, the mercury is found to
find  its way very readily into the veins, but not  into the arteries;
and it  has  been concluded by Fohmann, that this indicates a natu-
ral communication between these sets of vessels in  the glands.  This
view is certainly rendered plausible  by the proved termination of
the lymphatics in the veins of the  neck, and by the  fact which
appears to be established by the observations  of  Fohmann, Lauth,
and Panizza, that in birds,  as well  as in reptiles and fishes, there
are communications with the  small  veins at  many points  of  the
pelvis  and abdomen.  Nevertheless, the evidence  for  such  a com-
munication in  the  lymphatic glands  is  very unsatisfactory.  The
more probable  explanation of the  fact  above  noticed seems to be,
that the brittle texture  of the interior of the  glands readily gives
way before  mercury, and that  then  the  minute veins, which are
more numerous than the  arteries and  less resisting, are the first to
receive the extravasated metal.
   Origin of the Lymphatics.—We have before spoken of the origin of
the lacteals in the villi of the small intestines.   The  lymphatics in
other regions have been usually considered to arise in  the substance
* Anatomical and Pathological Observations. 
ORIGIN OF THE LYMPHATICS.
617
of the  skin and mucous membranes, and  on the surface of  the
viscera by a plexus  of somewhat variable character.   In  the  skin
and  elsewhere  the  meshes  are very close  and small, while  on the
lungs they are much more open and the vessels larger.  The surface
of the liver and spleen is overrun  with a network of  lymphatics of
remarkable luxuriance.  So far as mercurial injection can inform us,
these plexuses are the commencement of the lymphatic system;  but
we have been recently made acquainted with a system of lymphatic
vessels discovered by Kolliker in the  tail of the larvae of batrachian

                             Fig. 171.
 Part of a ramification of a lymphatic of the under part of the tail of a tadpole, a. Simple membrane,
forming the wall of the vessel. 6. Prolongation or process of this membrane,  c, d. Patty granules
attached to the inner surface of the membrane, and surrounding the nuclei,  e. A closed extremity of
the vessel. /. Branched cell, just united to a corresponding extremity,  g. Branched cell, on the point
of coalescing with a capillary lymphatic vessel already formed.—Magnified 400 diameters. After Kolliker.
 reptiles, which renders it probable  that a still finer series exists in
 the higher animals and in man, than those comparatively large ones
 which compose the plexuses just mentioned.  Kolliker observed these
 vessels during life, and satisfied himself of their continuity with the
 neighbouring lymphatic trunks.   He found them  about the same
 size but less numerous than the blood-capillaries, and composed of a
 simple, very delicate membranous wall, projecting into small pointed
 processes, here and  there, and  containing a  few flattened  nuclei.
 The pointed processes  may belong  only to  their rudimentary and
 not to their  completely developed condition.  He states that they
 ramify in an arborescent manner, without anastomosing, and  end  by
 free closed extremities.   They have no  valves, and  remain of the
 same  width during life, but after death  exhibit the  same contrac-
 tility, though not of  so active a kind, as the capillaries,  by lessening
uniformly  in diameter  during a certain  time.   He was  able  to
 detect the  movement of their transparent contents by that  of the
granules and lymph-corpuscles, which, in rare instances, they were
observed to contain,  and found it to be continuous, and very slow,
almost twelve times  as slow as that  of  the  blood in  the capillaries.
He found the mode of development of these primary lymphatics  to
       40 
618
ABSORPTION.
resemble closely that  of the capillaries, i. e., it takes place by the
outgrowth and subsequent  coalescence and tubulation of processes
from contiguous nucleated cells.
   Kolliker's observations on the relations of these minute lymphat-
ics with the capillaries are interesting.   He found  that when  the
current of blood was regular, there AYas no appearance of communi-
cation between the two orders of vessels, but that when the circula-
tion was excited  and tumultuous, owing  to  the confinement of  the
tadpole under glass, during the observation under a high magnifying
power,  red blood-corpuscles  escaped more or less readily from the
bloodvessels into the contiguous lymphatics ;  and in several instances
he was able to detect  actual  communications between lymphatics of
the  finest kind and the  network of capillary bloodvessels.  After
careful inquiry, however, he concludes that  these junctions are due
to rupture, or, perhaps, in some cases, to  a primitive abnormal form-
ation.   He further noticed  a  reflux of  blood into the  lymphatics
through the orifices by which their trunks open into the larger veins.
This retrograde current was almost always observed when the respi-
ration was impeded by want of water, and the veins were consequently
gorged, or when a ligature was placed round  the head.  In the latter
case, the whole lymphatic tree was  often fully and  beautifully in-
jected with blood.

  A lymphatic system exists in all the vertebrata, but the glands are wanting in
fishes and reptiles, and are very few in birds, being found only in the neck.  In fishes
and reptiles, however, there  occur large and intricate lymphatic plexuses, chiefly
without valves, accompanying and sometimes completely surrounding the bloodvessels
in a luxuriance quite superior  to anything found in the higher classes.  Moreover,
there exists  in the course  of the  lymphatic trunks in these  animals  and in birds,
pouches furnished with valves and muscular walls, which contract rhythmically and
urge on the lymph towards the veins.   These lymphatic hearts are, in birds at least,
formed of the striped fibre, according to the observation of Stannius ; and we owe to
Volkmann the interesting fact that, in frogs, their contraction may be excited by the
direct influence of portions of the spinal marrow.*

   Do  the  Lacteal and  Lymphatic   Vessels  absorb ?—From  the
account now given,,it  is clear that the structure and arrangement of
the lymphatic  vessels  fit them only for  the conveyance of fluid in
one  direction, viz., from the various  tissues  in which they originate
to the great veins, and  thence to the  heart.  Hence there can be
no doubt, that, whatever other function they may  subserve, they
are  designed  to carry fluid into the  blood either from the exterior
of the body, as in the case of  the digestive mucous  membrane and
the  skin, or from the interstices of the various  textures, where it
may have  been derived either directly  from  the circulating mass, or
indirectly  from the waste of the textures themselves.   It was till
lately  assumed too  exclusively that  this  system of vessels was the
sole agent in  such absorption, and hence  the  name of absorbent
system, as  applied  to  it, and the view which allowed the bloodves-
sels no share in the absorbent function.
   To prove that  the  lacteals  absorb chyle, it is only necessary to
* Paget's Report, 1844-5, p. 27. 
                PROOFS OF LYMPHATIC ABSORPTION.           619

 examine them in a  fasting and  in a  recently fed  animal.   In the
 former their contents are transparent, in the latter they are milky,
 and the  opaque fluid can be shown, by simple means, to move on in
 the  course  indicated by the  valves.   That the lymphatics absorb
is perhaps best  shown by the phenomena of disease.  The syphilitic
 poison is frequently carried from the primary sore  along the lymph-
 atics,  and exciting  inflammation in  this route may  occasion de-
 posits of lymph or pus either on the  penis  or in the groin, and
 the matter of abscesses so formed is  capable of imparting the disease
 to other individuals, thus proA'ing the multiplication, and  probably
 also the real transport of  the virus along these channels.   The in-
 flammation of the lymphatic trunks and glands, so  often observed to
 ensue upon accidental wounds, either  poisoned or not,  especially in
 debilitated subjects, seems  due to an  actual propagation of morbid
 materials in  the current of  the lymph, exciting inflammation in suc-
 cessive parts as it  comes  into contact with them; and the severe
 constitutional disturbance usually attendant on this state of lymphatic
 inflammation is attributable, with a high degree of probability, to a
 discharge of some such  morbid fluid  contaminating the lymph into
 the bloodvessels, so  as to mingle with the general  circulating mass
 of  blood.  Wagner mentions  that the axillary glands of  a subject
 brought for dissection were found of  an intense red colour from the
 deposition of cinnabar in their texture,  while on the arm was a red
 tattooed figure of old date,  which had evidently furnished the mate-
 rial.*
   That the  bloodvessels also absorb,  however, is rendered certain,
 not  merely by considering  that  their  structure and  physical con-
 ditions  furnish  every element requisite  for this  function, but by
 experiments  of  a conclusive nature.   Panizza  poisoned  a horse, by
 confining hydrocyanic acid in a loop of intestine, Avhich was sepa-
 rated from the  body excepting by one artery and  vein which main-
 tained the circulation in it.  As long as the vein was compressed
 the animal escaped,  but when the pressure was remitted the poison
 took effect; and, in blood drawn from the vein, the acid was detected.
   Contents of the Absorbents.—The lymphatics (and  the lacteals when
 digestion is not going on) contain a nearly colourless and transparent
 fluid, termed  lymph, in which are included a number of colourless
 nucleated cells  of globular shape (lymph-corpuscles,  colourless cor-
puscles), analogous to, and  even  identical with, the colourless cor-
puscles of the blood.   The lacteals,  during  the digestion of fatty
matters, always contain another element, which gives a milky hue to
the chyle, viz. a finely granular matter, termed, by Mr. Gulliver, the
molecular base.
   Lymph  and chyle, when withdrawn  from their vessels, sponta-
neously coagulate into a slightly coherent jelly in the course of  a
few minutes.  This  property  depends on the presence  of fibrine in
a fluid form, as  in the blood, and varies with the  point from which
the  lymph is drawn, as well  as  with the activity of the  nutritive
* Physiology, by Willis, p. 440. 
620
ABSORPTION.
vigour in the animal at the  time.   The clot at first entangles the
floating  particles, and if the  fibrine have sufficient energy, it under-
goes some degree of  subsequent contraction, by which a  loose mesh
is separated from the fluid part, as the crassamentum from the serum
of the blood.   Most of the  corpuscles  usually remain in the clot,
though some escape and remain with the fluid element.    The coagu-
lability of the lymph appears to bear  a  close relation to that of the
blood in the same animal.
   Lymph.—The liquid portion, liquor lymphae, is supposed by some
to be simply albuminous in the primary network, and to acquire its
fibrine on its passage onwards through  the vessels and glands towards
the veins.   The fibrine is  found in increasing quantity towards the
main trunks, though never in so large a proportion as in the liquor
sanguinis.   The same kind  of saline matters are  also met with in
the liquor  lymphae  as in the  liquor sanguinis, together with a trace
of fatty substance and some  iron.
   The lymph-corpuscles are very scanty  in the primary network  and
                                branches (as already noticed  in the
                                observations of Kolliker), and they
                                increase  in number, and  perhaps in
                                size, towards the trunks,  especially
                                as they pass the glands.    They pre-
                                sent themselves under some varieties;
                                in one, and this is the most usual, the
                                nucleus  is concealed by a granular
                                matter; in another this granular mat-
                                ter  appears in process of  removal or
                                deliquescence, so that the nucleus is
                                visible;  or,  again,  the  interval be-
                                tween  the nucleus and the cell-wall
                                may be quite clear, and the granular
                                matter wanting.  These  corpuscles
                                are  called, by Mr. W. Jones, respect-
                                ively the granule cell and the nucle-
                                ated cell in the uncoloured stage,  and
                                he further points out that there are
                                in the lymph other nucleated  cells
                                approximating in colour to the red-
                                corpuscles of the blood,  and which
                                he regards as in progress  to  become
                                red  blood-corpuscles, by losing their
                                cell-wall, and becoming reduced to
                                a simple nucleus.*
                                  Besides these true corpuscles of the
lymph, it is very common to find in it  red blood-corpuscles.  These,
it  is probable, have  been accidentally introduced into the  lymphatic
vessel during the dissection employed  to lay it open.
   Chyle.—The liquor chyli contains more  albumen and more fat

  * Philosophical Transactions, 1846, p. 82, and the next chapter, on the Blood.
Fig. 172.
  Fluid from a mesenteric gland of a rabbit,
when white chyle was present in the lacteals.
a. Molecular base, b, c, d, &c. Various or-
ganic corpuscles,  b. Appearance of the ma-
jority of corpuscles. The contained granules
are most numerous and coarse in the largest
ones, but almost entirely disappear under the
action of acetic acid, which thereby discloses
an appearance of one or two nuclei.  The
majority of the corpuscles are either large or
small, and but few of intermediate size. d.
Exhibits the effect of acetic acid in rendering
the corpuscles more clear and their nuclei
more  distinct,  e. Large lymph-corpuscle,
showing well the granulated border, f. Large
corpuscle, apparently inclosing three smaller
ones, each of which has the granulated cha-
racter. This  appearance of inclosed cells is
not common.—Magnified 300 diameters. 
                  CONTENTS OF THE ABSORBENTS.             621

 than the liquor lymphse.   It has been noticed that the lacteals near
 the  intestine contain little or  no fibrine;  their contents do  not ac-
 quire  the  power of spontaneously coagulating till we approach the
 main trunks.   Even in the receptaculum chyli and the thoracic duct,
 where the chyle  is commingled with the  lymph from distant parts,
 the  clot formed is still much softer than that of blood.
   The corpuscles of the chyle are the same as those of  lymph.   In
 addition^ however, we have in most instances the molecular base.
 This varies with  the amount of fatty matter in the food.  It gives
 the  chyle that  milky colour Avhich  was shoAvn by  Tiedemann  and
 Gmelin to have a close correspondence Avith the fat  of the  food.  It
 has  been noticed to be generally absent or very deficient in birds; it
 is less abundant  in herbivorous  animals than in carnivorous.  If a
 dog be fed  on  food from which fat  is carefully excluded, the chyle
 is not milky, but whey-like or  transparent.
   Sir Benjamin  Brodie,  in 1816, fed a cat on jelly, and  a  dog on
 isinglass jelly:  the  animals  were  killed after two hours.    The
 stomachs were  found nearly empty, the duodena  filled with a mix-
 ture apparently of chyle  and jelly; the lacteals and thoracic ducts
 contained  transparent chyle, which coagulated spontaneously.  He
 likewise fed  a dog on lard, after a  fast of thirty-six hours,  and in
 three hours killed the animal.  Some lard was found in the stomach,
 some fluid of albuminous character in the duodenum, the same tinged
 with bile  in the ileum,  and  in  the  thoracic  duct perfect milky
 chyle.*
   The molecular  base i3 present in the lacteals from the very com-
 mencement, even from the villi of the intestines.   It seems  to con-
 sist  of almost infinitely small particles (Fig. 172, a) of oleaginous or
 fatty matter, thrown into  this  form  by contact with the pancreatic
 secretion, as so well proved by Bernard.   The particles  do not look
 like  oil under the microscope—their outline is not definite  or sharp,
 and  from  this circumstance, as well  as  from  their extreme minute-
 ness, it is not easy to assign them an exact size.  In fact, they vary
 somewhat.   Mr.  Gulliver  makes their  diameter g^o^ of  an inch.
 Thus the white colour of the chyle does not depend on precisely the
 same cause as  that of the milk, for  the  latter exhibits under the
microscope myriads of true oil-globules of,different sizes.  A few
oil-globules are commonly  found in the  chyle, but they are  probably
extraneous.
   Dr. G.  0. Rees gives the following  analysis of the contents of
the thoracic duct of a criminal, Avho had taken two ounces  of bread
and  four ounces of meat on the preceding  evening, and two cups of
tea and a piece of toast an hour before he was executed, and whose
body was  examined  one hour  and a quarter after death.   Nearly
six drachms were obtained, of a milky hue, with a slight tinge of
buff.f

  * "Selections from Notes of Physiological Experiments," by Sir B. C. Brodie Bart.,
MS. pp. 39, 40, 41.
  f Phil. Trans. 1842, p. 82. 
622
ABSORPTION.
A\Tater     .....
Albumen, with traces of fibrine
Aqueous extractive ....
Alcoholic extractive, or osmazome .
Alkaline chloride, carbonate,  and sulphate, with
  of alkaline phosphate, and oxide of iron .
Fatty matters      ....
 90.48
  7.08
  0.56
  0.52
  0.44
  0.92

100.00
The following is  his analysis of the  lymph  and  chyle  of the
ass:
	Lymph.	Chyle.
Water .	. 96.536	90.237
Albumen	. 1.200	3.516
Fibrine	. 0.120	0.370
Extractive	. 1.559	1.565
Fatty matter .	. a trace	3.601
Salts .	. 0.585	0.711
100.000
100.000
  These latter may probably be  taken as fair samples of the con-
stitution of the  lymph and chyle.  Much variety, however, will of
course exist in  specimens, derived from different animals, and at
different periods of digestion.   The chief distinctions between lymph
and blood, are:  1st, the absence of the red particles in the former,
and, 2d, the  smaller  proportion  of albumen and fibrine.    Chyle
differs from blood in  the  same points, and, moreover, in its large
proportion of fat, which  may rise, according to  Nasse, as  high as
15 in 1000.   Chyle differs from lymph in containing more albumen,
and much more  fat.
   Quantity of Chyle and Lymph.—That the chyle enters the blood
very rapidly along the lacteals during digestion is obvious on open-
ing the body  of an animal.   It is easy to collect  from the  thoracic
duct of a small dog, in the course of a few minutes, as much as will
fill a watch-glass.   If absorption is actively going  on at the moment,
a ligature on  the duct will often  be followed by a rupture  of some
vessel  below by the onward pressure of the current.   So the lymph,
in some  instances, has been collected in considerable quantity in a
short space of time.   Geiger, from an open lymphatic on the foot of
a horse, collected from three to five pounds of lymph daily.   Bidder
has performed some experiments  on cats, from which he estimates
that a quantity of. lymph and chyle, together equal to one-sixth the
weight of  the body, or the whole weight of the  blood,  enters  the
circulation every twenty-four hours.   But it must be  borne  in mind
that this does not all form new supply, the lymph being, probably,
in large measure derived from that liquor sanguinis which has escaped
from  the capillaries  into  the interstices of the  tissues,  and which
cannot re-enter  the capillaries in  a direct manner.
  Mechanism of Absorption.—In  considering this part of  the  sub-
ject, the following points  should be remembered:—
  1. The process of absorption in living bodies implies imbibition by their tissues and
subsequent transmission of the imbibed fluid by the vascular channels to distant parts.
Med. Gazette, Jan. 1841. 
MECHANISM OF ABSORPTION.
623
  2. As regards imbibition, it is a phenomenon of a purely physico-chemical nature,
and occurs in inorganic as well as organic bodies, and in organic bodies both when
dead and living.  It depends mainly on the force of adhesion between a fluid and a
porous solid,_ by which the fluid is drawn into the interstitial passages of the solid.
  3. The fluid chiefly concerned in  this process in all animal and vegetable bodies is
water, which, as already stated, has a close affinity for their tissues,  and forms an
essential ingredient of them, without which they for the  most part lose their vital
and physical properties.
  4. The various other substances which are imbibed in living bodies are taken up in
a state of aqueous solution, such as gases,  albumen, fibrine, salts, &c.
  5. Where the fluid is rendered complex by holding in solution various  substances
which have different degrees of the force of heterogeneous adhesion for each other,
for the water they are dissolved in and for the porous solid, the phenomena of  their
transmission are also complex: various preferences, if we may so express it, exist;
one ingredient penetrates rather than another, and  the results depend very much on
the chemical qualities of the elements concerned.
  6. The laws relating to the mixture of different fluids also exert an important in-
fluence on the phenomenon.

  Referring to a former  page (p.  67) for  a brief notice of  the  phe-
nomena of  endosmose and exosmose, as observed by Dutrochet, we
may conveniently proceed with the  consideration of the  mechanism
of absorption in the living body under the following heads :—
  Absorption as influenced by the Qualities of the Fluids.—It was
shown by  Chevreul, that an animal  tissue imbibed very  different
amounts of different fluids  with which it  was brought into contact
after  it had been dried.   Thus the cornea took up water, brine,  and
oil, in the  proportions  of 461, 370, and 9; and Liebig, in experi-
ments with the dried bladder of the ox and pig,  has found that "of
all liquids,  pure water is taken up  in the largest quantity;  that the
absorptive power for solution of  salt diminishes in a certain ratio as
the proportion of  salt increases; and  that a mixture of alcohol and
water is taken up more abundantly the less alcohol it contains."*
  The mixture of two dissimilar fluids through a membrane is much
influenced by their respective attractions  for the  membrane.  Thus,
as water has a stronger affinity  for  the  membrane than  brine or
alcohol, it permeates it  more readily and arrives in greater  quantity
in a given time on the  opposite surface than either of those fluids.
Hence  more  water  comes  through  to mix with the  alcohol, than
alcohol to mix with  the  water, and an accumulation of the mixed
fluids consequently takes place  on the side of the alcohol; for the
alcohol, or  the Avater, having once traversed  the thickness of  the
membrane,  comes into contact with the opposite fluid, and  becomes
diffused  through  it  in obedience to known laws.   The same is  true
in regard to various substances miscible with water or dissolved in it.
  Within the bloodvessels and the  lymphatics is a fluid considerably
denser than water, and having less affinity for the walls than water.
Hence, if water be applied  to the  surface of the body or taken into
the stomach, it readily  enters the  circulation, particularly in the lat-
ter case, where it is brought into much closer contact with the blood-
vessels.   If a quart of warm water be injected into a torpid colon,
half an hour will  almost  suffice  to convey it into the  bloodvessels,

  * Researches on the Motion of the Juices in the Animal Body.  Translated by
Wm. Gregory, M. D.   London: 1848.  P.  9. 
624
ABSORPTION.
and thence through the kidneys into the bladder.   If, however, the
injected water hold a considerable quantity of common salt in solu-
tion, it will be absorbed more slowly; while, if the solution be a con-
centrated one, the fluid portion of the blood  will pass out of the
vessels to mix with  the  saline  solution.  The  action  of  many
medicines taken by the mouth, particularly of saline  purgatives, is
in some measure explained by these laws.
   It is interesting to notice that albumen passes less readily through
an animal membrane than gelatine, gum,  or sugar.   Thus alcohol,
ether,  oil, albumen,  gum,  and  sugar  would  disappear  from  the
stomach  in very different intervals of time.
   Absorption as influenced by the Porous Solid.—An extensive
and accurate series of experiments has  been recently  performed by
MM.  Matteucci and Cima, in which they investigated the influence
of different kinds of animal membranes, and of various arrangements
of them, on  the transmission of various fluids.  They employed—
1. The skin of the frog, the torpedo, and  the  eel; 2. The mucous
lining  of the stomach of the lamb, cat,  and dog, and of the gizzard
of  the fowl; and, 3. The mucous lining of the bladder of the ox
and pig.   The  following are the general conclusions  derived  from
these experiments, in the words of their translator :—
   " 1st.  The membrane interposed between the two liquids is very
actively  concerned, according  to  its nature, in  the  intensity  and
direction of the endosmotic current.
   "2ndly. There  is,  in  general, for  each membrane,  a certain
position in which endosmose is most intense; and the cases are very
rare in which, with fresh membrane, endosmose takes place equally,
whatever be the  relative position of  the membrane to the  two
liquids.
   " 3rdly. The  direction  which is  most favourable to endosmose
through skins, is usually from  the internal to the external surface,
with the  exception of the skin of the frog, in which endosmose, in
the single case of water and alcohol, is  promoted from the external
to the internal surface.
   " 4thly. The direction favourable to  endosmose through stomachs
and urinary bladders varies with different  liquids much more  than
through skins.
   " 5thly. The  phenomenon of endosmose is intimately connected
with the  physiological (natural or healthy) condition of the  mem-
branes.
   " 6thly. With membranes, dried or altered by putrefaction, either
we do  not observe the usual  difference  arising  from the  position of
their surfaces, or endosmose no longer takes place."*
   With the mucous lining of the stomach of the lamb  (whether the
paunch or the true digestive stomach is not mentioned) these trust-
worthy experimenters  found that water passed through  towards a
solution of sugar in greater quantity when the water was at first

  * Lectures on the Physical Phenomena of Living Beings.   By  Carlo Matteu,cci.
Translated under the superintendence of Dr. Pereira.  Am. Ed. p. 71. 
MECHANISM OF ABSORPTION.
625
 placed on that side  of the membrane which is naturally turned to-
 wards the  interior of the cavity of the  stomach, than when it was  .
 placed on the opposite side;  the  proportions being about as six to
 five.  On  the  contrary, when  solution of white of egg was used,
 water passed more readily, when placed in contact with the attached
 or submucous surface than when in contact with the free  or epithe-
 lial surface.   It passed also towards the albumen in only half the
 quantity that it did to  the sugar.   Again, with a solution of gum,
 the endosmose was very feeble, whichever way the membrane  was
 turned—and seemed to follow no rule.
   These facts show  the influence exerted by the structure or chemi-
 cal properties of the membrane in this process, but we are still very
 much in the dark as to the intimate cause of the influence thus
 operating.
   They are sufficient, however, to indicate the  extremely  important
 principle in physiology, that the chemical and structural properties
 of the tissues exert a great influence on all those processes in which
 the molecular motion of fluids is concerned.
   The thickness or  thinness of the membrane also much affects the
 result, and that for an obvious mechanical reason.  If the transmis-
 sion of fluids is so rapidly carried on out of  the body, through the
 entire thickness of compound and dense membranes, how much more
 expeditious must it be in the living tissues, Avhere the external fluid
 has in general but one or two very attenuated films of membrane to
 traverse in order to  arrive within the  capillary bloodvessels.
   Absorption as influenced by Pressure.—The influence of pressure
 on  the  passage of  fluids through  membranes is  illustrated  by a
 common  filter, or  by tying  a membrane over one end  of a  vessel
 containing  fluid, to which a syringe capable of applying various de-
 grees  of pressure is adapted.  In the latter  case, the rapidity of
 transmission will be  found,  caeteris paribus, to depend on the degree
 of pressure employed, and  after  a  certain time the transmission
 will be accelerated by the enlargement of the pores of the membrane.
 In this way pressure may be used as a test of the relative transmis-
 sibility of different fluids through membranes  of various thickness
 and quality; and  Liebig has found that  "through ox-bladder,  jfa
 of an  inch  thick, water flows under  a pressure  of twelve inches of
 mercury; that a saturated solution of sea salt requires from eighteen
 to twenty inches;  and that marrow oil only flows out under a pres-
 sure of thirty-four inches of mercury.
  " When  the  membrane used is the peritoneum of the ox,  -^\^
 of an  inch in thickness, water is  forced  through it by eight to ten
inches, brine by twelve to sixteen inches, oil by twenty-two to twenty-
four inches, and alcohol by thirty-six to  forty inches  of mercury;"
and hence  it appears, as this  eminent writer  remarks, that " the
power of a liquid  to filter  through an animal  membrane bears no
relation to  the mobility of its particles; for under a pressure which
causes water, brine,  or oil to pass through, the  far more mobile al-
cohol  does  not pass."
  As  pressure promotes the transmission of fluid through a mem- 
626
ABSORPTION.
  brane  in  one direction, so it tends to interrupt the  passage of the
• other fluid in the opposite direction—or, to apply this to  the blood-
  vessels of the living body, if they are distended by an  over-great
  quantity of blood,  so that this fluid reacts upon their inner surface,
  as in the  case of plethora, fluids  enter them with  difficulty from
  without — whereas,  if  their  bulk is  diminished by  venesection,
  absorption is comparatively rapid.  This conclusion was established
  by Magendie on good grounds,  and it has some illustrations and
  valuable applications in practice.
    Absorption as influenced by motion of the Fluid within the Vessels.
  —Fluid may be raised out of a reservoir against gravity, by direct-
  ing a stream along a membranous canal, which lies immersed in the
  stagnant fluid.   The outer fluid  enters the canal by endosmose, and
  is carried away with a speed proportioned to the velocity of the cur-
  rent.   If the fluid in motion is so  compressed as  to  exert  much
  lateral pressure on the wall of the tube, it will  rather itself pass out-
  wards, so as  to mingle with the fluid at rest, than receive and carry
  off the  latter.   If the fluid in  motion is also the more dense, or
  otherwise, that towards  which the external fluid would Aoav if both
  were  stagnant, then  its motion  accelerates  the endosmose by con-
  stantly bringing  on fresh  fluid of the original density, so that the
  first rate of transmission is maintained.*
    It will be scarcely necessary to state in detail the particular  bear-
  ing which the preceding considerations have on the question of the
  mechanism of the absorbent process in the living body.   It is,  how-
  ever,  very evident  that  they leave  us  with  little  more than  some
  general indications of the lines in which further investigation may be
  pursued with advantage.
    Applying  them  to the mechanical arrangements provided in the
  living  animal for this function, it is plain that they have a nearer
  reference  to  the  capillary bloodvessels  than to the lymphatics.  In
  both  we have a simple membrane  of  extreme thinness,  through
  which the absorbed fluid has to pass, and in doing so it must neces-
  sarily obey those laws Avhich form the proper subject of experimental
  physico-chemical inquiry.   But  in the bloodvessels, the fluid on the
  side  toAvards  which  absorption  tends, is already in motion  by a
  mechanical force, the heart's  action, and the absorption is accompa-
  nied with  a contrary current of  exosmose;  whereas in  the  lympha-
  tics, the internal fluid appears to have no motion but what is demred
  from the same force on which  the endosmose depends, and we have
  no evidence of any outgoing current.   In these respects the absorb-

   * In a valuable paper by our friend, Dr. Robinson, of Newcastle (Med. Gazette,
  1844), many experiments and arguments are given to show that absorption goes on
  rather on the venous side of the capillary network, and in the small veins, than on
  the arterial side.  He considers the motion of the blood to be an influential cause of
  absorption, by diminishing its pressure  outwards on the vascular walls, and thus
  allowing the external pressure (that of the atmosphere and of the surrounding tissues)
  to predominate.   There can hardly be a doubt that the rapidity of absorption would
  be influenced by the rate of movement  of the blood as well as by other mechanical
  conditions. 
FUNCTION OF THE ABSORBENTS.             627
ents resemble, more nearly than the  capillaries, the spongioles and
absorbent vessels of plants.
  Function of the Absorbents.—A few words may be  added on the
use of the  absorbents  in the  economy.  The chyliferous  vessels
probably have the same office for the intestinal tissues as the lympha-
tics in other  parts ; but besides  this, they  are largely developed,
and specially adapted by their mode of origin on the mucous surface,
to take up a portion, at least, of the food, after it has been rendered
capable of absorption by the action of the pancreatic secretion.  This
portion appears  to be pre-eminently  the fatty or oily,  which, as far
as experiments and  observation have yet determined,  is almost ex-
clusively absorbed  by the lacteals.   It  is chiefly in containing so
much more fat that chyle differs from lymph.
  The lymphatics cannot yet be said  to have  their office at all defini-
tively ascertained, yet it is  not difficult to assign them a part with
some degree of probability.  It appears that they form an interlace-
ment  among the capillaries in  the interstices  of most of the organs
and tissues  of the  body, and contain a fluid  not  disimilar in  kind
from the liquor sanguinis, though  more dilute.  They cannot be en-
gaged in  distributing new material to the organism, because their
structure adapts them only for  removing fluid from the tissues, and
pouring it into the bloodvessels, and because the current within them
is unequivocally in that one direction.  Thus the  fluid they contain
must enter them from the interstices of the tissues, having been ulti-
mately derived either directly from the capillaries, or indirectly from
them through  the tissues.  It seems not  improbable that  the liquor
sanguinis  effused through the capillary walls for the nutrition of the
tissues, may have its superfluous parts removed through the lympha-
tics, as it would, perhaps, be more readily received  into  these new
channels than into the same from which it had just been poured.  It
is a question quite undetermined, Avhether the effete materials of the
tissues are returned to the circulation in  any large measure through
the lymphatics, or  whether  they  are principally restored to it  by
directly entering the capillaries, in exchange for that outgoing cur-
rent of renovating plasma which serves to supply the waste in nutri-
tion.  The carbonic acid at least,  if indeed that product be  formed
among the  tissues,  outside  the capillaries,  and not in the blood,
seems to  enter the capillaries in a  direct  manner through their wall,
since  it  is  found in greater quantity in venous than in arterial
blood.
  The absorbent system, with  its glands, may be regarded in yet
another light,  viz., as a great internal glandular or secreting system,
the ducts  of which open  not on the surface of the body, but into the
vascular  system.  It is  conceived that  the   inner surface  of  the
lymphatics,  and especially of the  lymphatic glands, serves to elabo-
rate and separate from the blood contained in the vessels distributed
on their walls a secretion which is set free into their interior, and is
transmitted ultimately to the current of circulating blood through
the efferent vessels of the glands, which may be thus  looked upon
as excretory  ducts.  Some physiologists attach much importance 
628
THE BLOOD.
to the alleged increase in the  quantity of fibrine  contained in the
lymph as it traverses the absorbent  system,  and conclude  that this
is due to the  elaborating agency of the epithelial element of  the
absorbent  tracts on the  albumen of the lymph.  We  owe to  Dr.
Carpenter a very interesting  hypothesis on the  influence, in this
respect,  of the colourless corpuscles, which he imagines to exert this
catalytic action on the albumen in which they float.   This idea  will
be best considered in the Chapter on the Blood.

  On the subjects of the foregoing chapter, in addition to  the systematic works on
Physiology before referred to,  the student may consult Mr. Lane's  article "Lym-
phatic System," in the Cyclopaedia  of Anatomy and Physiology; Matteucci's
"Lectures on the Physical Phenomena of Living Beings," translated by Pereira ; and
the valuable "Reports" by M. Paget, in the British and Foreign Medical Review.
We would also refer to  a recent work by Liebig, on the motion of the juices  of the
animal body, ably translated by Dr. Gregory, from which we have derived much as-
sistance.
                       CHAPTER XXVII.

THE BLOOD.—ITS QUALITIES.—ITS PHYSICAL ANALYSIS.—THE LIQUOB
  SANGUINIS.—THE BLOOD-PARTICLES.—THE QUANTITY OF  BLOOD IN
  THE BODY.—THE PHENOMENON  OF COAGULATION.—THE  CONSTITU-
  ENTS OF THE BLOOD.—ANATOMY OF THE BLOOD-CORPUSCLES.—THEIR
  MODE OF ORIGIN.—THEIR FUNCTION.—THE CHEMICAL ANALYSIS OF
  THE BLOOD.—CHANGES PRODUCED  IN  THE BLOOD BY VENESECTION
  —AND BY DISEASE.

  The blood is a fluid, which  is ahvays circulating in numberless
canals among the various tissues  and organs of the body; it is the
source whence those  tissues and  organs draw their  nutriment, and
from which the glands  derive  the materials for  their several secre-
tions.   The  lymph and the chyle are poured into  it  as tributary
streams;  the former conveying to  it, in solution, materials yielded
up  by the wear  and  tear of the  tissues, and also derived from
without; the latter bringing to it new matter formed by the digestive
process.
  The blood is  a thick  fluid, apparently homogeneous, of  high
specific gravity (1041—1082, Simon), and of a red colour, in all
the vertebrate and most of the invertebrate  classes, but  exhibiting
differences of colour, according to circumstances to be noticed here-
after.—A  saltish taste, and  a peculiar heavy odour, must also be
reckoned   among  its characters.   If allowed to  rest  in a cup, or
other vessel,  it  exhibits  a remarkable  spontaneous analysis.  In
the course of from ten  minutes to a half an hour it separates into a
solid  portion (the  crassamentum) and  a fluid portion (the serum).
The latter, if carefully decanted off, will  be found to be a clear
straw-coloured fluid,  the  menstruum of that great variety of mate- 
THE CONSTITUTION OF THE BLOOD.
629
 rials which is held in solution or suspension in the blood.   Albumen
 in large quantity, salts, and  various organic  matters, are dissolved
 in it; oily matters  are suspended  in it;  and prior to coagulation
 fibrine isheld in solution, and  coloured and  other  particles are dif-
 fused in infinite multitudes throughout it.
   An artificial physical analysis of the  blood, first  suggested by
 Muller,  shows  satisfactorily  the  true  relation of its  various con-
 stituents.  ^ If the blood of an animal whose coloured particles are
 of  large  size,  as  the common frog, be  passed  through filtering
 paper, its liquid portion passes through, leaving the coloured parti-
 cles upon  the filter; thus analyzing the  blood  into two  parts—the
 liquor sanguinis and the blood particles.  The former,  by the spon-
 taneous coagulation of the fibrine, quickly separates into  serum and
 fibrine, which  in  this instance is  colourless, but  in the ordinary
 coagulation it is more or  less coloured by the red particles, which
 become entangled by the coagulating  fibrine.   Another mode of
 effecting a similar analysis is that suggested  by Dr. A.  Buchanan of
 GlasgOAV: it consists in mixing fresh-drawn blood with six or eight
 times its bulk of serum, and filtering through blotting-paper: coagu-
 lation is retarded  by the admixture with serum, and a great  part of
 the diluted liquor sanguinis  passes through the filter, and  subse-
 quently coagulates.   By microscopical analysis of the blood,  we find
 that, besides the  red particles, it contains others  which  are devoid
 of colouring matter—namely, the colourless corpuscles.
   The constitution of the blood is expressed by the following table:—
                          {corpuscles ; red and colourless.
                          ,.         .  .     .  ,.   „ f fibrine.
                          hquor sanguinis, consisting of <

   That the blood has the same essential characters in  both the ver-
 tebrate and invertebrate classes,  has  been shown  by Mr. Wharton
 Jones's researches, who finds the  coloured and colourless  corpuscles
 in the blood of all animals, presenting, however, sufficiently distinct-
 ive features.
   In man and the mammalia there  are  two  kinds  of blood, distin-
 guished  by difference  of  hue, the  scarlet, arterial blood, obtained
 from the left side of the heart, and from the arteries; and the black,
 or dark red, venous  blood,  obtained from the right  side of the heart,
 and from the systemic veins.  We shall consider, further on, the
 special characters  of each kind, and the cause of their  differences.
  The temperature of the blood  ranges between  100° and  105°.
 Its reaction is slightly alkaline, so that a drachm of blood will satu-
 rate rather more than a drop of vinegar.
  The consideration  of the  natural  history  of  the human blood
 involves the determination of the following points:—
  First, the quantity of blood in the body.
  Secondly, the phenomenon of coagulation, and the circumstances
 which promote or retard it.
  Thirdly, the physical analysis of  the blood, and the characters of
its constituents.
  Fourthly, the chemical analysis of the blood. 
630                       THE BLOOD.
  I. Of the Quantity of Blood in the Body.—It is almost impossible
to obtain sufficiently accurate data upon which to found a calculation
of the total quantity  of the blood Avhich  circulates in the vascular
system.  The various estimates which have been formed have been
guesses, based on trials by bleeding animals to  death, and compar-
ing the weight of the blood drawn with that of  the animal's body:
also, on ascertaining, in various cases  of hemorrhage, or of venesec-
tion, the quantity of blood which had been lost in a  brief period,
without destruction to life.
  Harvey estimated  the  weight  of the blood as one-twentieth of
that of the body, and Haller at one-fifth.   According to the former
estimate, a man  of one hundred and fifty pounds' weight would have
only about seven and a half pounds of blood, whilst the latter would
assign him thirty pounds.
  Valentin devised an ingenious method of estimating the quantity
of the blood.  He first ascertains the amount of solid constituents
in a certain quantity of blood, withdrawn by venesection; this is
replaced by a certain quantity of distilled water, and then he ascer-
tains the amount of solid  constituents in a quantity of the  now
diluted blood equal to that which had  been first withdrawn.  From
the data thus obtained he calculates the whole quantity of the fluid,
which  admits of such a change in  its specific  gravity, by the  sub-
stitution of a certain quantity of distilled water for the quantity of
the fluid itself previously withdrawn.   The problem is, to determine
the quantity of  fluid of specific gravity B, which, on removing from
it say  six ounces, and replacing those six  ounces by a certain quan-
tity of distilled  water, becomes  reduced  to the specific  gravity j3.
Having by this method determined the quantity of the blood in dogs,
he deduces the quantity of blood in the human body by comparing
the weight of men with that of dogs.   And  thus he assigns about
thirty-two pounds for a man between  thirty and forty  years of age,
and twenty-eight pounds for the female.*
  On the whole, we have no right to infer that the quantity of blood
in the  human body exceeds thirty pounds; and, for  practical  pur-
poses,  we shall do well to form a much lower estimate  of it, and to
learn from thence how important it is to avoid being prodigal in the
removal  of a  fluid, so essential to the phenomena of life—and to
beware of subjecting patients  to those excessive losses of blood,
which, experience teaches us, too often inflict upon the general nu-
trition of the body a shock so severe, that it is more or less seriously
affected by it ever after.
  II.  The Phenomena of Coagulation.—We have already described
the separation of the blood into serum and crassamentum.  In this
consists the phenomenon of coagulation.  In  a few minutes after
blood has been allowed to rest in a vessel, its surface  assumes the
appearance of a jelly, on  which, after a little  more time, drops of
serum  appear to ooze out here and there;  these drops multiply and
coalesce, so as to cover the jelly-like surface with a layer of serum,
* Valentin, Physiol. 
COAGULATION OF THE BLOOD.
631
which  increases so much in quantity, as coagulation advances, that
the clot is at last found  covered  and more or less completely sur-
rounded by serum.
 _ The crassamentum, or clot, is a solid mass,  varying  much in con-
sistence:  sometimes soft  and tremulous, like  jelly; at other times
firm and tough almost  as leather.  If a section  of it be made, it
will  be found in most  instances  coloured throughout, but always
most deeply  so at  its lower half or third, the  heavy red particles
gravitating to the lowest part; that portion which is exposed to the
air  having always a scarlet tint.   The surface of  the clot is always
slightly concave; sometimes it is remarkably so, and  exhibits the
appearance of a hollow  cup, and on these occasions the upper layers
of the clot generally consist  of fibrine  only, which is  of a whitish
yellow or buff  colour, with an intermixture of colourless  corpuscles
entangled in  its meshes.  Hence blood which  presents these appear-
ances is  said to be "cupped  and  buffed."   The phenomenon is due
to the  more complete subsidence of the blood-particles as the clot is
being formed, so that its upper layers are left  quite free from colour-
ing-matter.  The clot, when this state is present,  is generally small,
tough, and well contracted, and it  floats in a large quantity of serum.
  The period required for the completion of coagulation varies very
much : it commences in about two minutes after the blood has been
collected in a vessel, and is rarely completed for half an hour after-
wards, but more  frequently the clot is  not perfectly formed in less
than one or two hours.  After it has been formed,  it will continue to
contract for many hours, and to press out the serum, Avhich will thus
increase  in quantity while the bulk of the clot undergoes diminution.
   Coagulation  appears to take place more rapidly under the influ-
ence of a high temperature, 114°  to 120°, according to Hewson ; it
is also favoured by spreading  out  the blood on a  flat  surface; and,
within certain limits, by an increase in the fluid parts of  the blood.
  On the other hand coagulation is retarded by the addition of  alka-
lies, and some of their salts, as sulphate of soda, nitrate of soda,  car-
bonate of soda, chloride of sodium, also  carbonate of potass,  nitrate
of potass, and  nitrate of  lime.  A strong  solution of any of these
salts, added to fresh-drawn blood, will delay  or stop its coagulation
according to the strength and quantity of the solution.
  Authors affirm that the blood will not coagulate in  the bodies of
animals killed by blows  on the epigastrium, or  after having been long
hunted, or by electricity  or lightning.   It will not coagulate after
asphyxia by carbonic acid, as in the following cases, recorded by
Mr. Gulliver:  A man, setat.  thirty-five, and three children,  were
suffocated in  a burning house, their bodies being untouched by the
fire ; in all of them the blood was fluid, forty-eight hours after death,
in the  heart and great vessels, and did not coagulate after its remo-
val out of the body.
   The coagulation  of the blood appears to  be retarded by its contact
with living surfaces.  Thackrah's  experiments showed that blood con-
fined between  two ligatures  in living vessels, remained fluid for a
considerable  time,  from  five  to   sixty  minutes;  F. Simon  affirms 
632
THE BLOOD.
that it will  retain its fluidity for three  hours; and experiments of
the same kind by Hewson, lead to the conclusion that the coagulation
is  retarded  under similar circumstances.  Fluids withdrawn from
serous cavities, as in ascites or  hydrocele, often exhibit a coagulum
of considerable size, which does not form till some minutes after their
removal, showing that the fibrine  must have  been prevented from
coagulating so long as it remained in the  living cavity.
   The addition of bile retards or prevents coagulation, probably by
the mechanical obstacle which it affords to the cohesion of  the par-
ticles of fibrine.   According to John Hunter, the addition of a solu-
tion of opium to the blood retards its coagulation.
   It is needless  to waste time in inquiring into the cause of coagu-
lation.   That the phenomenon belongs only to one of the constituents
of the blood is proved,  unequivocally, by the fact  that if that ma-
terial, the fibrine, be removed by whipping  blood  with a bunch of
twigs, as it  flows from a vein, coagulation will not take place  in the
fluid which  remains.  The fibrine has accumulated in  a  coagulated
state round the twigs, and the fluid received  into the vessel  consists
only of serum and red particles.  The coagulation of the fibrine of
the blood is one of those ultimate facts in physiology Avhich  we must
be content to observe and to describe, but of the cause of which we
are likely to remain ignorant.
   The buffing and cupping of the blood has long attracted the  notice
of observers, and is regarded by many practical men as an indication
of a state of inflammation in some part of the body at the time of
the abstraction of the blood.  The immediate cause  of this pheno-
menon is explained with the highest  probability, as follows, by Dr.
Babington:—
   " The blood,  consisting  of liquor  sanguinis  and insoluble  red
particles, preserves its fluidity long enough  to  permit the  red par-
ticles, which are of  greater  specific gravity, to subside through it.
At length,  the  liquor sanguinis separates  by  a  general  coagula-
tion into two parts,  and this phenomenon  takes  place  uniformly
throughout  the liquor.  That part of it through which the  red par-
ticles had time to fall, furnishes a pure fibrine  or buffed crust, while
that portion into  which the red particles had descended furnishes
the coloured clot."   The following experiment, made  by the same
ingenious observer, illustrates the truth of the  explanation given by
him.   " Take two similar tall jars or phials,  each capable of holding
about four  or five ounces, and  let one  of  them be half-filled with
olive oil; draw the blood of a healthy subject  into  each.   That
which flows through the oil  will be found to have a layer of  liquor
sanguinis on its surface, which will form  a buffed  crust, while there
will be none upon that which  is  received  in equal quantity, and
in other respects  under the same circumstances, into the  empty
jar.  *
   According to  the observations  of Nasse, and of Mr. Wharton
Jones, the red particles of blood which is disposed to become  buffed
* Med.-Chir. Trans., and Cyclop. Anat., art Blood 
             THE PHYSICAL ANALYSIS OF THE BLOOD.          633

and cupped, exhibit a remarkable tendency to cohere in the form of
rolls,  like piles of coin, and this probably facilitates their precipita-
tion to the lowest part of the coagulating mass.
   The circumstances which  favour the formation of the buffy coat
may be  any or  all of  the following: 1. Slowness  of  coagulation;
2. Increased Aveight of red corpuscles ; 3.  Diminished specific grav-
ity of serum,  Avhich obA'iously would have a corresponding effect
to the preceding; 4. A great diminution in the  proportionate quan-
tity of the red corpuscles, or an increase in that  of fibrine, and of
colourless  corpuscles.  The  occurrence  of the  cupped and buffed
blood, after great hemorrhage, or in cases  of anaemia, is very pro-
bably in a great  degree  due to  the disproportion between the red
particles and the fibrine.
   Although  the  phenomenon of  cupping and buffing frequently
occurs in that state Avhich is  called inflammatory, it  is not so exclu-
sively confined to it as to justify practitioners  in regarding it, as is
too often done, as a proof of the existence  of inflammation, suffi-
cient  of  itself to warrant or  call for further depletory measures.
   III. The'Physical Analysis of the Blood.—By physical  analysis
we find in the blood the following parts ; viz. the serum ; the fibrine
held in  solution in  the serum prior to coagulation ; the red  cor-
puscles  and the colourless corpuscles,  both of which float in the
liquor sanguinis.
   The serum is a straw-coloured fluid, of  sp. gr. 1025 to  1030.—
When heated to 165° it becomes  nearly solid, proving that  it holds
in solution a  very large  quantity of albumen, as much as seven or
eight parts per cent.  In twelve ounces of serum there would, there-
fore, be nearly one ounce of albumen, equal to the white of one egg.
But this is not  the  only ingredient Avhich we find  dissolved in the
serum.   It is an alkaline fluid, and its alkalinity is chiefly due to
the presence of free soda, and of carbonate of soda.  Besides these
it contains chloride of sodium, phosphate of lime  and of magnesia,
and probably lactate of soda.
   The serum also contains a  small quantity of fatty matter in which
can be  detected the crystallizable  as well as the oily  portion.   In
health, the proportion of this  does not  exceed half a  part in 1000
parts, so that a pint of serum will contain about five grains of fatty
matter;  but  in some cases it exists in so large a proportion as to
render the serum milky.  This occurs not only in certain forms of
disease, but likewise, according to Drs. Buchanan and R. D. Thom-
son,*  very shortly after the ingestion of food of an oily or amylace-
ous nature.
   Whatever  other elements  may exist in the blood, as serving to
furnish materials for the various  secretions, are held in suspension
or solution by the Avater of the  serum.   Thus, urea is sometimes
found in it, and the recent observation of Bernard, referred to at p.
604, shows that it constantly contains  sugar; when the liver  acts
imperfectly, some of  the elements of bile are found in it.

                    * Med. Gaz. vol. xxxvi. p.  972.
       41 
634                        THE BLOOD.
  It is as yet uncertain whether the existence of even minute quanti-
ties of some of these substances in the blood, such as urea and the
biliary matters, is consistent with health.  It is not improbable that
they may be constantly being  developed by  the  chemical changes
which  are unceasingly going on in that fluid, but that they become
attracted from it as  quickly as  they are formed in it, and do not
accumulate in  it in any quantity which admits of  being easily de-
tected.   According  to Dr.  Thomson, sugar  may be always easily
detected in the blood, shortly after a meal containing starch.*
  The Fibrine.—We have  already explained the manner in-which
fibrine may be obtained from  the blood.   One thousand  parts of
healthy blood contain tAvo or three of fibrine.   A  pint of blood Avill
therefore yield about  twenty-nine grains  of fibrine, adopting the
highest estimate.
  Pure fibrine, or, to speak more exactly, fibrine separated from the
red corpuscles, for  it  cannot  be completely separated  from the
colourless  corpuscles,  has  a remarkable tendency to assume the
fibrous form.   A drop of  the  colourless liquor sanguinis, which is
found  on the surface of blood, about to form a bufl'y coat, exhibits,
when coagulated, an intricate  interlacement of minute  fibres.—
Here  and there  a colorless cell is  entangled in  it, appearing as a
centre, whence pass numerous radiations of minute  fibres.   Dr. W.
Addison, who believes that the fibrine is contained within the colour-
less corpuscles, considers the bursting of a  large number of these,
and the  consequent liberation  of their inclosed fibrine, as the first
step in the process of coagulation, Avhich explains the entanglement
of them  in the fibrillating fibrine.   The process may be best  seen,
as this excellent observer recommends, by examining a drop of the
colourless liquor sanguinis  from blood, about to form a buffy coat,
and allowed to  coagulate upon  a slip of glass.f
  The Bed Corpuscles.—It is to the multitude of coloured particles
which  float in  the liquor sanguinis, under the name of " the red
corpuscles," that the blood  owes its colour.  To examine these, it
is only necessary to place a drop of  blood in the field of the micro-
scope, taking care to  dilute  it  with a fluid, similar  or  nearly  so in
specific gravity to the  serum;  a solution  of sugar or of salt in
water,  answers this purpose completely.  So numerous and so crowd-
ed together are  the corpuscles in a drop of  blood, that it Avould be
difficult to obtain a complete view of any one of them without this
precaution.
  In  the human blood, the coloured corpuscle is  a circular double
concave  lens; from being  concave  on each  surface, its margin is
thick  and rounded, and its  thickness is less in its centre  than at
any other  part (Fig.  173).  Its  size varies considerably; in the
same  drop of blood there are  corpuscles of  all sizes Avithin a range
of from  i^-q to as'oo of an inch  in diameter,  the aA'erage  being
from the 3 g^o t0 3 jou-  With a good microscope, and a magnifying
power  of 200 diameters, the characters of  the blood-corpuscles may
be most  clearly seen, and Avhen the instrument is perfectly adjusted,

  * Loc.  cit.       f Dr. W. Addison's second series of Exp. Researches, 1843. 
THE BLOOD-CORPUSCLES.
635
the double concave surface may be unequivocally demonstrated.   If
the corpuscles are floated in water, they become biconvex; if in a
fluid denser than serum, as in a strong saline or saccharine solution,
they shrink, put on  a  shrivelled  aspect, and become granulated on

Fig. 174.
ahQg
C^3
  Red corpuscles from human blood, a. Viewed      Red corpuscles of the ox, magnified 400 diame-
 on the surface,  c. Ariewed in profile,  b. An    ters.  a. in their natural state,  a. Profile view.
 aggregation of the corpuscles in a roll.—Magni-    b. ATiewed on the surface, c. A corpuscle altered
 fied 400 diameters.                        in shape,  b. Corpuscles altered by a menstruum of
                                     bigh density.

 their surface (Fig. 174, b) ; this shrivelled appearance may again be
 got rid  of by diluting  the  menstruum  and  reducing  its  specific
 gravity to the lowest point.
   It has been aflirmed, by Mulder  and  others, that the blood-cor-
 puscles of venous blood are  biconvex—those of arterial being bicon-
 cave—and they attribute the  difference of colour of  these two kinds
 of blood  to  the different mode in which  the light is reflected from
 the concave  and the convex surfaces of their respective corpuscles.
 With reference to this doctrine, we have only to state  that we have
 carefully examined two portions of the same  blood after they had
 been agitated in  oxygen  and carbonic acid gas, and thus been ren-
 dered  respectively scarlet and purple, but  that  we have failed to
 detect  any  well-marked  difference  in  shape  between  the  blood-
 corpuscles of the tAvo  specimens.
   The blood-particles have  a remarkable tendency  to aggregate in
 rolls like pieces  of coin (Fig.  173,  6): this tendency, as  has been
 already remarked, is  said by some to  be greatly increased in blood
 which forms a buffy coat in its coagulation.

  The red blood-corpuscle of Mammals resembles in shape and structure  that of
 man (Fig. 174): there is much diversity of size in the various orders ; it is  smallest
 in the ruminants, and the  smallest known is that of the Napu musk-deer, which is
 reported by Mr. Gulliver not to exceed 1-12,000 of an inch in diameter.  The corpuscles
 of the goat are very small,  1-0300—1-7045 of an inch in diameter.  The largest cor-
 puscles in Mammalia are found in the elephant; they measure, according to Gulliver,
 1-2745 of an inch in diameter.  The Camelidas offer a remarkable exception to  the
 circular  form of the blood-corpuscle of Mammalia.  In these animals it is oval, as
 first  pointed out by Mr. Gulliver,  with a long diameter of from 1-3100 to 1-3550 of
 an inch, and a short diameter of 1-5800 to 1-0444; in all other respects, however, these
 corpuscles agree with those of other mammals.
  In Birds, the corpuscles are oval in shape ; they have a very distinct nucleus,
 which is much smaller than the corpuscle itself.   The long diameter of the blood-cor-
 puscle of Birds ranges between 1-1500 and 1-2000 of an inch, and the short diameter
from 1-3000 to 1-4000 of an inch.  (Figs. 175, 181, 183.)
  In Reptiles, the red corpuscles are of  an oval  shape,  with a distinct and large
nucleus (Fig. 176).  The long diameter of the corpuscle has a range of from 1-420 to 
636
THE  BLOOD.
1-1400 of an inch, the short diameter ranging between 1-700 to 1-2600 of an inch.—
Among these are to be found the largest known blood-corpuscles, as those of the pro-
teus and of the syren.

              Fig. 175.                                   Fig. 176.
  Red corpuscles of pigeon's blood, magnified      Blood-corpuscles of the common frog. Magnified
400  diameters.   A. Red  particles unaltered,    400 diameters.  A. In serum, a. Fully developed
with two  or  three colourless  particles,  b.    corpuscle,  b. Nucleus  with pule  cell-wall  and
Treated with acetic acid, which  develops the    clear contents,  c. Colourless corpuscle. B. Treat-
cell-wall and nucleus more clearly.              ed with acetic acid.
  In Fishes, the red  corpuscle is oval in most of the genera, and possesses a distinct
nucleus (Fig. 177, b).  In  the  lowest  cartilaginous fishes, as the lamprey and  the
myxine, however, it returns to the circular and biconcave form of the Mammalian red
corpuscle (Fig.  177, a).  This remarkable fact  was first pointed out by Professor R.
Wagner.   Mr. AVharton Jones has shown that it contains a nucleus, which cannot be
detected in the red corpuscles of Mammalia.

               Fig.  177.                              Fig. 178.
  Red corpuscle of fishes,  a. Lamprey.       Rlood-oorpu<cles of  the crab.  a. Granule  cells.  B.
6. Skate.—After AVharton Jones.          Nucleated cells.—After Wharton Joues.

  In the Invertebrate classes, corpuscles exist which are in close analogy with those
of the Vertebrata, but differ from them in several  particulars (Fig. 178).  They are
nucleated  cells, some of which contain within them numerous granules which conceal
the nucleus ; some of these corpuscles, according  to  Mr. AVharton Jones, are, upon
their  first  removal from the body, of an elongated oval form, and others  spindle-
shaped.   Their size  does not exceed  ] -2O0() of an inch in their  long diameter, nor
1-3000 in the short.   In most of the classes the particles do not exhibit any indica-
tions  of colour,  although they contain some  of the  ingredients  of hematine; in a
few, however, slight traces of colour are present.*

   Of  the Structure of the  Red  Corpuscle.—The  structure  of the
red  corpuscle  of  most of  the  Vertebrata  may be  readily demon-
strated in the blood of Reptilia—that of the frog,  for instance.—
It  is distinctly a  nucleated cell—consisting  of a delicate cell mem-
brane, within  Avhich  is a  granular nucleus,  Avhich may be rendered
more distinctly granular by acetic  acid (Fig. 176,  b).  The nucleus
is globular and much smaller than the cell, and the interval between

  * Mr. Wharton Jones's papers in the Phil.  Trans, for 1840, " On  the blood-cor-
puscle  considered in its different phases of development in  the animal  series," con-
tain an account  of a careful examination of these particles, and may be referred to
with advantage by all who are engaged in the study of this most interesting subject. 
THE COLOURLESS CORPUSCLES.              637
  the inner surface  of the latter and the outer surface of the former
  is nl ed by fluid winch holds the colouring matter in  solution.   Cor-
  puscles of this kind floated in pure water become distended by the
  endosmosis of it,  burst, and give exit  to  their nuclei,  while  the
  shreds ot the cell-membrane  are scattered in the fluid.
    It cannot be shown satisfactorily that the biconcave circular cor-
  puscle of human blood  and  of that of mammalia  is of  the same
  structure  as  this,  because it  cannot be demonstrated to consist of
  eel  and nucleus.   If it be as the blood-corpuscles of birds, reptiles,
  and nshes undoubtedly are,  a nucleated cell, the  obscurity of its
  nucleus  is probably due to one of two causes; either it is so large
  as  accurately to fill the cell, leaving  no space  between  the outer
  surtace oi the one  and the inner surface of the other, or it is so ex-
  tremely■ minute as completely to elude our means of observation.
  #  Mr. \V barton Jones supposes that the mammalian  red  corpuscle
  is a nucleus, the cell  of which had existed only in the earlier stages
  ot development.  Kolliker, on the other hand, affirms that the nu-
  cleus disappears while the  cell-wall is  persistent.  All  that  micro-
  scopic examination with the highest powers and the best instruments
  shows respecting the  structure of  this corpuscle is that it consists of
  a  delicate membrane, inclosing a semifluid material, impregnated
  with the proper colouring matter of the blood; and that this struc-
  ture may truly be  assigned to it is amply proved by the change of
  form which _ it undergoes  by the  endosmosis of  pure Avater, Avhich
  will  cause it  to  burst  and evacuate its contents,  consisting of
  nothing more than some  minute  granules, none of which  can be
  compared to  a nucleus.   So far  as microscopic analysis  would
 enable  us to  decide this question,  we should be disposed to declare
 in favor  of Mr. Jones's view ; but it seems greatly opposed by two
 facts ;_  first, that in  the corpuscle  of  the lower vertebrata,  the
 colouringmatter is  contained between the nucleus and the  cell-wall,
 whereas in the mammalian  corpuscle  it would be contained in the
 nucleus ;  and,  secondly, that this peculiarity of structure is limited
 to  one  class of vertebrate animals.  It receives support,  however,
 from observing the several steps of  the development, for  the cor-
 puscle exhibits a stage in which  a  nucleus is visible (the stage of
 coloured nucleated cell,) (Fig.  179,  d,) and this nucleus, in  the very
 large corpuscle of the elephant, and likewise in the very small cor-
 puscle of the goat, exhibits a strict correspondence in size  with  the
 perfectly formed blood-corpuscle.   But here, again, Ave  notice  the
 difficulty above referred to, that in this stage of nucleated  cell, the
 colour is  found between  the  cell and the nucleus.  It seems to us
 that  further research is  required,  in order to determine the exact
 homology of the mammalian red corpuscle.
   The Colourless Corpuscles.—These particles are found in  all
 kinds of blood.   They are spherical bodies, destitute of colour ;
 their structure is that of nucleated cells, the cell-membrane being
extremely  delicate;  both the  cell-membrane and the  nucleus  and
nucleolus  are  rendered distinct  by the  action of dilute acetic acid,
which dissolves some granules which are contained in the cell.—
These granules are external to  the nucleus.   When they are 
638
THE BLOOD.
Fig. 179.
  Phases of the  human blood-cor-
puscle (after AVharton Jones),  a and
b. Granule-cells in the coarsely and
finely granular state,  c and d. Nu-
cleated cells, c without colour, d with
colour,  e. Free cellseform nucleus or
perfect red corpuscle.
numerous and large the nucleus is concealed  by them.   Corpuscles
of this kind, denominated granule-cells by Mr. W. Jones (Fig. 179,
                           a, b), are  viewed by him  as  constituting
                           an earlier  stage than those in which  the
                           nucleus and nucleolus  are distinct, which
                           he calls nucleated  cells (Fig.  179, c, d).
                           In size, the  colourless corpuscles slightly
                           surpass the red  corpuscles in mammalia,
                           but not in the  other  vertebrata.  They
                           are essentially the same as the nucleated
                           particles found in lymph and in chyle.—
                           In examining the capillary circulation in
                           the transparent parts of  some animals,
                           as the  web  of the  frog's foot, they may
                           be seen sparingly  at  the  margin of the
                           current of red  corpuscles, either station-
                           ary and adherent to the wall of the blood-
                           vessels, or slowly moving  forward in the
                           layer of liquor sanguinis which is in con-
tact with the wall, and  which  is thus shown to  be comparatively
motionless.
  The  colourless  corpuscles are  much feAver in number than the
coloured ; it is said that they exist in the  proportion of one  colour-
less  to fifty coloured, but that in inflammatory states of the blood,
the former are much more numerous, being as one in  twelve.   After
great  loss  of blood, the proportion  of the colourless  corpuscles is
considerably increased.

  A very important inquiry is  to determine—1.  The  histological
                                       relation of these particles  to
                                       each other; and,  2.  The part
                                       which they take  respectively
                                       in the vital phenomena of the
                                       blood.
                                          With regard  to  the first
                                       point, physiologists are divid-
                                       ed  in opinion  as to whether
                                       they may  be regarded as dis-
                                       tinct and independent par-
                                       ticles, performing each their
                                       special  functions, or whether
                                       the  one, namely, the  colour-
                                       less corpuscle, may be viewed
                                       as an early or embryo condi-
                                       tion of  the red corpuscle.
                                          The  weight of argument
                                       seems to  favour  the conclu-
                                       sion that  the  colourless cor-
                                       puscles are to be  regarded  as
                                       an  early stage of the coloured
Fig. 180.
A.
  Corpuscles from the bloodvena of the cava hepatica
of the embryo chick on the twentieth day of incubation.
A. Red blood-corpuscles altered by water,  b.  Blood-cor-
puscles coherent and modified in shape by cohesion,  c.
a. Large  spherical cells containing highly  refracting
granules  (fatty). 6. The same represented only in out-
line, to show their shape, c. Fully formed red corpus-
cles.—Magnified 200 diameters. 
                   THE COLOURLESS CORPUSCLES.               639

corpuscles,  which are in the adult  or perfect state.   In the earliest
periods of  foetal  life, the blood-corpuscles,  as  is shown by the re-
searches of Vogt, Kolliker, and Cramer, originate, in the same way
as the elements of the  tissues, from nucleated  cells,  which are the
same in point of constitution as  the colourless corpuscles; with this
exception, that they contain betAveen the nucleus and  the cell a con-
siderable  number of granules,  which are  largest  at  the  earliest
periods of embryonic life.  At later periods similar nucleated  cells
are  generated  in the  liver, as first
pointed out by Weber, and  in the             Fig.  181.
mesenteric  and  lymphatic  glands,        "**          *
and from these sources supplied to       Jl          /K.
the  blood.   In this  fluid they un-       1§%^';   %qP  ^
dergo a transformation into the com-        „.• /??i;--£s   gt  ..:,  ^
pletely formed blood-corpuscles, by       /i';':'-:-fS   J|y ffi\}
the remoAral of  the granules, the in-     a/ ^>   ^ @  * <r^?h__*'
creased development of the nucleus,             §       ^
and the  generation  of  colouring   GraQuleS; ^^^ and red blood.cor.
matter, excepting in the  mammifer-  puscles from the embryo chick at the twen-
             ■ti        i  •       tieth day of incubation,  a a.  Granules,
OUS    COrpUSCle,   WflOSe    Ultimate  some being enveloped by a faint cell-wall, and
„i______„„„_ j.„ _.___• 4. •  it, „  „„„.   granule-cells with coarse granules,  b b. Red
Change Seems tO COnSlSt in the COm-  Dlood-corpuscles.-Magnified 200 diameters.
plete absorption of the nucleus, ac-
cording to Kolliker, or the removal of the wall of the  cell, accord-
ing to Wharton Jones.
  Now, as  there can be no doubt  that, in the  adult, the lymphatic
and chyliferous systems  afford a  source for the constant develop-
ment of particles  identical with the colourless corpuscles, and  as
such corpuscles are always  found  in considerable proportion in the
blood  (being more  numerous under circumstances  unfavourable  to
normal changes, as  in  inflammations), it seems very reasonable  to
infer that similar transformations  of colourless into coloured par-

               Fig. 182.                    Fig. 183.
•>W H'

      a. Granules of which the cell-        Nucleated cell (a), red corpuscles (6), and
     wall is not visible, b. Granule-       panules from the chick on the 20th day of
     cells and red corpuscles.—Mag-       incubation.—Magnified 200 diameters.
     nified 200 diameters.

tides are going on in the adult as in the embryo, and that the  lym-
phatic and lacteal  systems must be at least one, and that a fertile
source, from  which red corpuscles are being continually supplied to
the blood. 
640                        THE BLOOD.
  If, however, we reject  this view of the relation of the colourless
to the coloured corpuscles, then Ave must regard them as independ-
ent particles, each having its special function;  and it devolves upon
the advo'cates of  this view to suggest the office, and to explain the
mode of origin and decay of each.
  Function of the Bed  Corpuscles.—It is clear that the red cor-
puscles must  perform some very important office in the life  of the
blood, because of their  great numbers, their  constancy, and the
serious consequences to the general nutrition and  the vital  actions
of the body, which ensue upon any considerable diminution  in the
quantity of them.  But we have no definite knowledge on this  sub-
ject, and  all that can  be  suggested is, as yet, of a speculative and
hypothetical nature.
  Liebig  adopted the  highly ingenious notion that the red  cor-
puscles are carriers of oxygen, and that by their colouring matter
they are  peculiarly adapted  for attracting  that principle.   The
property of attracting  oxygen is due to the iron, which forms six
per cent,  of the hematine contained in the red corpuscle.  In venous
blood, according  to Liebig, the iron is in the state of  carbonate of
the protoxide of iron ; this,  as  the  blood passes through the  ca-
pillaries of the lungs, or becomes otherwise exposed to the action of
the air, is by the absorption of oxygen converted into the hydrated
peroxide  of iron, the  state in which that metal  exists in arterial
blood.  And  at  the  same  time it  gives off " for every volume of
oxygen necessary for  the change from protoxide to peroxide, four
volumes of carbonic  acid."  As the arterial blood  passes through
the capillaries  of the system,  the peroxide of iron yields oxygen to
certain constituents of the body, which is employed in producing
the  change of matter, and in oxidizing neAvly-formed substances in
the blood, Avhile in their return towards the heart, the red particles
Avhich had lost their oxygen " combine with carbonic acid, producing
venous blood ; and Avhen they reach the  lungs an exchange takes
place between  this carbonic acid and the oxygen of the atmosphere."
  This doctrine  of Liebig assigns the use  of the  colouring matter,
or of  the  contents of the blood-corpuscle, rather than of the cor-
puscle itself;  it  is, indeed, highly reasonable to  suppose that  the
hematine  has an important  connection with  the attraction of
oxygen into the  system, or  to speak  more  generally,  with  the
changes which take  place  in the blood in  respiration.   The differ-
ence of colour, being the prominent feature of distinction between
arterial and venous blood, is strongly indicative of this ;  and also the
fact now demonstrated by Mr.  Wharton Jones,  that the blood of
the invertebrata contains  a certain degree of  colour,  or at any rate,
even where no colour can be distinguished, according to Professor
Graham's  analysis, " a sensible  quantity of iron, perhaps as much
as red corpuscles."
  Liebig, however, does not explain why the hematine is invariably
contained in a multitude of nucleated cells.   The consideration of
this point seems to us to  afford the clue to determine the real func-
tion of the red particles. 
DR. CARPENTER'S HYPOTHESIS.
641
   The true office of the red blood-corpuscles would, probably, be
most correctly described as that of forming or secreting the hema-
tine, which  in the greatest part of the animal kingdom is coloured,
but which even, though colourless, appears to contain iron.  These
particles are  floating gland-cells, as  Henle  suggested some  years
ago ; they are in all essential points of structure  like the secreting
cells of true glands, and there is no reason  Avhy, free and floating
in a liquid like  the  liquor  sanguinis, they may not exercise upon
materials dissolved in that fluid an influence analogous to that ex-
ercised by the elementary particles of the liver, or the kidney, or
the pancreas  upon  the blood.  The matter secreted by  the blood-
cells is the hematine, Avhich  term Ave would here use to  signify not
merely the colouring matter, but  the  entire contents of  the blood-
corpuscle, of  which iron is an important if not an essential  ingredi-
ent, and which is coloured in the  vertebrata  and in some of  the
invertebrata.  It is this hematine which plays an important part in
the attraction of oxygen, and  Avhich by its  colouring matter also
exercises some important influence on the whole economy; for there
seems  no other source from whence can be derived all that pigment
which  is diffused throughout various  textures, such as muscle, the
nervous centres, the skin and its appendages, the eye, &c, but that
which  is  formed in such great quantity in the blood.
   Office  of  the  Colourless Corpuscles.—If these particles do  not
constitute an early stage of development of the coloured corpuscles,
it is- clear that  they must  be  viewed as performing some special
function  in the blood,  independently of  the latter.  R. Wagner
viewed them  as  identical with chyle  and  lymph  corpuscles, and
assuming that in the  invertebrata no  coloured particles  existed,
he  regarded the blood in such animals  as  identical Avith chyle or
lymph  ; as, in fact, the latter fluid not yet elaborated into blood.—
In the  blood of vertebrata, therefore, he would view these particles
as chyle  or lymph globules not yet transformed into blood particles.
  But  Dr. Carpenter has put forward a more elaborate hypothesis
respecting the office of  the  white corpuscles.  This able physiolo-
gist regards  these particles as the  agents in the development of
fibrine  in the blood, or in the conversion of albumen or other ma-
terials  of that fluid into that "plastic" compound.  This substance
certainly first appears in the chyle and lymph, where these particles
are found  in great numbers floating in an  albuminous fluid.   Nor
does it appear in the chyle until after that fluid has passed  through
the mesenteric glands,  which furnish  these  particles in large num-
bers.
  Dr.  Carpenter regards the appearance of these colourless cor-
puscles or cells in the blood as a phenomenon in close analogy Avith
the development of cells in the albumen of the seed in the vegetable
kingdom, and in the yolk of  the eggs of oviparous  animals; and he
supposes that  the office of these cells is to convert crude alimentary
materials into proximate principles, Avhich again, through the agency
of cells,  may  be converted into, or may afford the materials for the 
642
THE BLOOD.
peculiar compounds which form the characteristic ingredients of the
secretions, or may pass into organized tissue.*
   Of  the Development and Decay of the Blood- Corpuscles. — It
seems to us that the view  which Mr. Wharton Jones takes respect-
ing  the development of the blood-corpuscles, already described at
pp. 637, 638, affords the most simple and correct explanation of the
origin and  development of these  particles.   According  to it, the
lacteal and  lymphatic  systems may be  regarded as  the source
whence fresh supplies of blood-corpuscles are being continually fur-
nished to the blood at all periods of life.   In the early embryo, as
well as in the adult, the process of  the formation  of the blood-cor-
puscle would be the same ; that is, the development of a nucleated
cell, which undergoes transformation into  the coloured particle;  the
steps of the process being  successively granule cell, nucleated cell,
and coloured particle (Fig. 179).  This view would lead us to regard
the  system of lymphatic  and  mesenteric glands as the seat of an
unceasing  generation of new particles, which undergo their later
stages of transformation  in the blood.   And it  is well worthy the
attention of pathologists,  as  affording an  explanation of the great
influence which (as  we learn from experience) this extensive system
of glandular bodies exercises upon general nutrition.
   Prior to the formation of this glandular system and the develop-
ment  of the  lymph and chyle  corpuscles, the blood-particles  are
derived as nucleated cells from the cells of the germinal membrane,
but  they undergo essentially the same changes as  in the more ad-
vanced periods of life.  In mammalian embryos they are described
" as of  large size,  spherical or oval, pellucid and colourless, nu-
cleated, and full of minute granules."  Mr. Paget, whose description
we folloAV, confirms the observation made  by Kolliker, Fahrner, and
others, of the occasional occurrence of " a process of multiplication
by bi-partition of the nucleus, each of which, either by appropriat-
ing half the cell, or by developing a cell around itself, becomes the
central nucleus of a new cell, differing  from  the parent cell from
which  it escapes  in little except in being smaller and more gener-
ally  circular, "f
   Of the manner  in  which the blood-corpuscles decay we really
know nothing—no more than of  the mode of decay of the elements
of the tissues.   The notion held for a time, by some physiologists,
that the existing particles gave birth to new ones by a gemmiparous
or fissiparous generation, has no foundation in careful observation.
And it is most probable that, as Mr. Paget  remarks, " new corpuscles
never appear to be produced from  the germs of old ones; when a
corpuscle is past its perfection, it degenerates and probably liquefies."
"The  changes of such degeneration," adds this excellent observer,
" have not been clearly seen in mammalian corpuscles ; but they are

  * Dr. Carpenter's remarks on this subject deserve the attentive perusal and con-
sideration of physiologists.—See  Principles of Human Physiology, \\ 153-lo'J, fourth
Am. Ed.
  ■j- Kifkes's Handbook of Physiology, Am. Ed. p. 63, Fig. 12. 
THE CHEMICAL ANALYSIS OF THE BLOOD.         643
probably nearly similar to what occur in those of fish  and reptiles;
in which the old and degenerate corpuscles appear perfectly white
and  pellucid (not shaded or  granular, like the lymph-corpuscles),
smaller than they were, and in some  instances  cracked, or  as  if
eroded.  The  nuclei appear  to degenerate with the cells, but be-
cause of their  darker and harder  outlines, remain  longer distinct,
and often look  like free nuclei,  unless the dim cell-wall  round them
be carefully searched for.  But in this process, no germ for a neAV
corpuscle issues from the transient  cell.   Every new corpuscle forms
itself in and from the materials of the  lymph and  chyle, and  is
perfected in the  blood, and  the blood is maintained by constant
repetitions of this process."*
   Kolliker  has lately put forward the remarkable opinion that the
spleen is the seat of a process of destruction or dissolution of the
blood-corpuscles.  We  shall examine this view farther on, Avhen we
come to describe the structure of the spleen.f
   IV. The Chemical Analysis of the Blood.—The  blood is a fluid
of the greatest complexity,  as must be expected, if  we regard  it
as containing the material for the nutrition of all the tissues, as well
as for all the secretions. Thus,  in addition to the water which forms
four-fifths of it, and  without  which no transfer of materials could
take  place  from it to  other parts, it contains  albumen  for the al-
buminous tissues; fibrine for the fibrinous ; salts which are found  in
the various secretions; colouring'matter,  which, more or less modi-
fied, is found in the nervous matter, the skin, the eye, the bile, the
urine, the  cerumen; and fatty  matters identical Avith those which
are found in fat.
   The researches of the last few  years, in which  Lecanu,  Andral
and  Gavarret,  Rees,  Becquerel and Rodier, Christison,  Miller, and
others have taken a conspicuous part, have  determined, with a very
near agreement, the relative proportions in which the  various stami-
nal principles exist in healthy blood.
   The following method may  be adopted  for this kind of quantita-
tive analysis.J   Let the blood flow  at four different periods and  in
equal quantities  into two vessels;  the first and third into  the first
vessel; the second and fourth into the second ; the weight of each
should be taken.
   From one portion the fibrine  may be  separated  by whipping,  or
by shaking up the blood in a bottle containing small pieces of lead ;
the residue  will consist of the serum and  red particles.  The weight
of this, deducted from that of the whole  portion of blood, will give
the Aveight of the fibrine.
   The second portion may be set aside to coagulate spontaneously;
when this process is completed, the crassamentum must be taken out,
and, after the serum  has completely drained away from  it, it should
be weighed.  The weight of the fibrine, as obtained by the first ex-
periment, being deducted from that of the entire clot, will give  that

  * Loc. cit. p. 67.              f  Art. Spleen,  Cyclop.  Anat. and Phys.
  t For a more elaborate and exact method of analysis, see Mr. J.  E. Bowman's
" Handbook of Medical Chemistry,"  Am.'Ed. p. 160. 
644
THE BLOOD.
of the coloured corpuscles.  The amount of albumen may be obtained
by precipitating it from the serum, and Aveighing it after filtration.
  The general results of  this method of analysis may be thus stated
roughly.  In one hundred parts of blood, about seventy-eight parts
are fluid  and twenty-two parts  solid material ;  and  of  the  last,
the albumen constitutes  rather less than seven  parts, the fibrine
one-fourth of  a part, and the red particles rather  more than four-
teen parts.
  The following table gives a summary of the analysis  of the blood
of healthy individuals of both sexes, by Becquerel and Rodier, who
are among the most recent analysts.
  Composition of  one thousand parts of blood in men,  derived from
eleven analyses.
Water
Red particles
Albumen
Fibrine
Extractive matters and free salts
Fatty matters
Mean.      Maximum.   Minimum.
 779       760        800
 141.1      152        131
  69.-4       73         62
   2.2        3.5       1.5
   6.8        8         5
   1.6        3.255      1
  Composition of one thousand parts of blood in women, derived
from eight analyses.
ATater
Red particles
Albumen   .      .     ,
Fibrine
Extractive matters and free salts
Fatty matters
Mean.     Maximum.   Minimum.
791.1       773        813
127.2       137.5      113
 70.5        75.5      65
  2.2         2.5       1.8
  7.1         8.5       6.2
  1.62        2.86      1
   Composition of the  Red Particles, and of the Hematine.—The
large proportion which the  coloured particles form of the solids of the
blood, entitles them to the most attentive consideration of physiolo-
gists ; they are more than  fifty times the quantity of the fibrine, and
nearly double as much as the albumen.
   The red  corpuscles consist, according  to most chemists, of two
elementary substances, globuline and hematine; the former is nearly
allied to if  not identical with albumen, and forms the solid part of
the blood-corpuscle, its  cell-Avail, and  nucleus, when it exists ; the
latter is the colouring  material, or blood-pigment.
   The folloAving process is recommended by Figuier  for the separa-
tion of the hematine from the globuline.
   Defibrinated blood  should be  mixed with at  least four times its
bulk of a saturated solution of  sulphate of soda ; the mixture  must
then be throAvn on afilter; the fluid and some corpuscles pass through,
leaving the mass of coloured particles on the  filter.    This  must
next be  boiled in  alcohol, slightly acidulated Avith sulphuric acid;
the  hematine will be thus  dissolved, the  colourless  globuline,  in
combination Avith some of the sulphuric  acid,  remaining undissolved.
   The next  step  in this  process  is, to add to  the hot  solution of
hematine enough carbonate  of ammonia  to remove the  sulphuric
acid; the fluid must  then be  filtered, to  remove the sulphate of
ammonia thus formed, and the liquor must be exposed for evapora- 
MORBID BLOOD.
645
tion ;  when, by this means, it is reduced one-twelfth of its bulk, it
will be found to deposit hematine as a dark or black powder.
  This  hematine  is insoluble in water,  alcohol,  or  ether,  unless
mixed Avith some alkali, which  renders it readily soluble;  when
burned, it yields a considerable quantity of iron.
 ^ Mulder's ultimate analysis gives  the following  as  its composi-
tion :—
              Carbon     .      .     .      .      65.84
              Hydrogen   .      .     .      .      5.37
              Nitrogen    ....      10.40
              Oxygen    ....      11.75
              Iron       ....      66.5

  Much difference of opinion exists among chemists as to the state
in which iron exists  in the blood.   We have already referred to the
opinion of  Liebig, who affirms that  in venous blood it is  in the
state  of protoxide, while in arterial blood it is in that  of peroxide;
and that the change of colour, from the dark red  of  the former to
the bright  scarlet of the latter, is due to the conversion of the pro-
toxide of iron into peroxide  by the  absorption  of  fresh  oxygen  at
the lungs.   Mulder supposes that it exists in the metallic  state  as
a  simple  ingredient, as essential to  the  colour as its oxygen, its
hydrogen,  its  carbon, or its nitrogen.  Scherer's  experience, how-
ever,  would go to show that iron  is not essential to  the colour of
the blood.   He treated the red particles Avith sulphuric  acid, so as to
remove their  iron, and  found that  their colour still remained.—
Hence he infers that iron is not essential to  the colour.
   The value of the administration of  iron in the treatment of cases
of  anemia  after loss of blood, is  well known and highly appreciated
by  practitioners ; it remains to be determined in Avhat way it  con-
tributes so poAverfully,  as it unquestionably does, to the restoration
of the blood to its  normal  state.   The fact that it does exercise a
powerful influence evidently  indicates its importance  as an  ingre-
dient in the hematine.   And it may be remarked that iron, even
if not -essential to its  colour, may nevertheless be  an essential in-
gredient of a normal hematine.
  Difference of Arterial and Venous  Blood.—The prominent differ-
ence  betAveen  blood drawn from the arteries  and that from the
veins, is to be found in the bright scarlet colour of  the former, and
the dark  red,  almost black,  of the latter.   To  which may be added
some  difference of temperature, that  of arterial being one  or tAvo
degrees higher than venous; perhaps also some  difference as to den-
sity, but upon  this point observers are very far  from being agreed;
and also as to the proportions of solid constituents;  but on this sub-
ject, likeAvise, the reports of analyists are contradictory  and  highly
unsatisfactory.
   The  blood  of the vena  porta is  said by F. Simon to coagulate
more sloAvly and less  perfectly than ordinary venous blood;  it con-
tains less fibrine and much more fat.
   Influence of Venesection  and of Disease upon  the  Blood.—The
influence of venesection and of some morbid states upon the rela- 
646
THE BLOOD.
tive quantities of these constituents of the blood deserves to be well
impressed upon practitioners.
  Venesection, or the  loss  of blood by any means,  reduces the
amount of the red particles chiefly, and the more so in proportion to
its frequency; the serum is diminished in density, and  the quantity
of the albumen and the fat is slightly reduced ;  that of fibrine is
not affected, nor are the extractive salts.
  The following cases from Dr. Christison illustrate the influence of
venesection upon the blood.
  The first is  that  of  a  middle-aged woman, who had been previ-
ously repeatedly bled for palpitations of the heart.   The analysis of
her blood gave the following result:—
               Fibrine        ...       2
               Solids of serum ...       76
               Red particles    ...       57
               AVater         ...      863
  In the second case there had been frequent bleedings after rheu-
matism :—
               Fibrine        ...       4
               Solids of serum ...       93
               Red particles    ...       57
               AVater         ...      844

  This latter case shows how impotent is  venesection, even when
carried to a great extent,  over the reduction of fibrine, the material
that  forms those new deposits of organizable matter  or  plastic
lymph, which in inflammations of internal organs, such as the lungs
and heart, so much interfere with  their normal action.
  The following experiment, also, illustrates  the effect of venesec-
tion upon the blood,  first, when the animal was well fed at the time
when the bleedings  were being practised ;  and, secondly, when it
was starved betAveen the operations.
  A large dog was  fed  upon two pounds of meat, and a quart of
milk a day,  and  six ounces  of blood were draAvn on each  of four
successive days from his jugular vein.   The blood was analyzed by
our friend, Mr. Lionel Beale, Jun., who obtained the results shown
in the following table :—
No. of Bleedings.	First.	Second.	Third.	Fourth.
AVater	783.79	810.89	815.18	813.04
Fibrine	2.42	4.72	4.34	3.99
Solids of serum	70.94	70.85	69.92	76.01
Blood-corpuscles	142.85	113.54	110.58	106.95
	1000.00	1000.00	1000.02	1000.00
Density of serum	1025.8	1024.8	1023.5	1023.6
  Here, notwithstanding the liberal allowance of food, the red par-
ticles suffered a considerable diminution.
  The dog was  now  allowed to recover, and was well fed for three
weeks, and at the end of that time his blood Avas analyzed ; he was
then starved  for four days,  being allowed nothing but water, and on
each of these four days was bled.   The  following table gives the
result of these analyses. 
MORBID BLOOD.
647
Xo. op Bleedings.	First.	Second.	Third.	.Fourth.	Fifth.
Water	802.71	804.40	805.44	838.30	849.81
Fibrine .	2.28	1.91	3.95	5.26	5.13
Solids of serum	74.13	72.61	71.46	68.46	71.62
Blood-corpuscles	120.88 Dog fed.	121.08	119.15	87.98	74.21
			Dog	starved.	
   Th the  latter experiments we notice a diminution of the red par-
ticles  to an  extent even more marked than in the former ;  and it
may also  be  observed that even  after a lapse of three weeks, with
good feeding, the red particles  had not  recovered  their  original
amount.
   With reference to  the estimate  of the quantity of fibrine, it  is
right  to observe, that, both in these  and all other  analyses, it  is
liable to an important source of fallacy, which arises from  the im-
possibility of forming a  separate  estimate of the  quantity of the
colourless corpuscles which adhere to the fibrine, and must necessarily
increase its apparent quantity.
   The  modifications which disease produces in the relative quanti-
ties of the blood-constituents, are chiefly referable  to  an increase
(real or apparent) in the  quantity of fibrine,  or a diminution of that
element, or of the blood-corpuscles ; or, lastly, to such an alteration
in  the quality of the fibrine (its  quantity being  unaltered) that  its
coagulating power is materially interfered with.
   In diseases of an  inflammatory  type, in  which  there is  active
fever  of a sthenic character, with proneness to effusion of  plastic
lymph, or  to the  formation of thick  laudable pus, fibrine is said  to
be  increased in quantity to as much as five or six parts in one thou-
sand of blood ; it is  also said that there is an increase in the colour-
less corpuscles, and at first a  slight increase in  the coloured corpuscles,
though these latter afterwards undergo a diminution, which is the more
marked  in proportion to the extent of depletory measures employed.
In  no diseases are these changes in the blood more conspicuous than
in  rheumatic fever, pneumonia,  and  pleurisy.   The  cupping and
buffino- of  the blood  is very marked, and the most exquisite examples
of  that interesting phenomenon may be obtained  from patients
labouring  under  these  maladies.  Sufficient allowance, however, does
not seem  to  have been  made by observers  generally for the  ex-
tent to which the apparent  increase of fibrine may be explained by
the increase of the colourless corpuscles.*

  * Zimmerman, and more recently Mr. John Simon, in  his valuable lectures  on
Pathology (Lancet, 1850, and since republished in 8vo.),  have advocated the doctrine,
novel indeed, but most worthy of attention, that the fibrine^f the blood must be re-
garded not as an ingredient prepared for the nourishment of certain tissues, and
ready to be appropriated by them, but as " among those elements which hnve arisen in
the  blood from its own decay,  or have reverted to it from the waste of the tissues."
Mr. Simon has been  led to adopt this opinion chiefly from observing the unaltered
or even increased quantity of the fibrine under bleeding, starvation, anamia, and
other states of exhaustion  and  increased  waste, and also from the fact that in these
respects  the fibrine is in direct contrast with  the red particles which are  rapidly
reduced by these means.  This view is also favoured by the fact noticed  by Andral and
O-ivarret  that an improvement in the breed of an animal tended always (catcri:* pari-
bus} to increase the  proportion of the red particles, but to diminish that of the fibrine.
The small quantity of fibrine in foetal blood, the absence of fibrine from the egg, the
chyme, and the smaller quantity of it in the blood of  carnivora  (which feed on  it) 
648
THE BLOOD.
  Diminution  of the quantity of fibrine, accompanied  with a de-
crease in the red particles, occurs chiefly in fevers arising from the
presence  of a poison  in the  system.  None show  these  changes
more than  those fevers which are caused  by the paludal poison—
namely, intermittent fevers.   In rheumatic fever, and in acute gen-
eral gout, there is  a remarkable tendency  to the diminution of the
coloring  matter of the  blood, even Avhen  these diseases have been
treated in  the  mildest  manner.  It Avould  seem as  if the materies
morbi acted as a blight upon the red corpuscles, and prevented their
development in the  normal proportions.
  In some cases—especially those connected with enlarged liver and
spleen—the diminution in the  coloured particles is accompanied by
a remarkable  increase  in the  number of the colourless particles.—
Some cases of this  condition of blood have lately been collected by
Professor J. H. Bennett, who proposes for it the name Leueocythemia
(xtvxos, tvhite ; xv*o$, a cell; oX^a, blood).*
  The  fatty matters of the  blood  are  sometimes   increased  in
quantity  apparently from  non-elimination.  Under  these  circum-
stances the serum  becomes quite  milky, an appearance Avhich  is
quite characteristic of this state  of blood,  and may  be removed by
ether.  We have already alluded  (p. 633) to  the milkiness Avhich
folloAvs the ingestion of fatty food, but Avhich cannot  be regarded as
abnormal.
  There  is a condition of blood to  which F. Simon  has given the
name spaneemia (otavo;, poor), and Avhich  is popularly called poor
blood.  This is  characterized  by changes in the quality rather than
in  the  quantity of the  blood-constituents,  and especially, perhaps,
in  the quality of the fibrine.  When  the  blood is in  this state,
hemorrhages are of frequent  occurrence, OAving probably to the im-
perfect manner in Avhich the coats of the bloodvessels are nourished.
Purpura  and scurvy are well-knoAvn diseases, of which the prominent
feature consists in this poorness of blood.   In the former malady,
we  have found the blood-corpuscles shrivelled, and even disintegrat-
ed ;f but it is difficult to determine whether this was due to a defect
in  their  mode of generation  and  development,  or  to a diminished
specific gravity  of the serum favourable to  its endosmose by them.

  On  the subject of the blood, reference is made to the works on Physiology already
quoted;  Hewson's works, by Gulliver (Sydin. Soc.); J. Hunter on the Blooil, &c;
Mr. Gulliver's numerous and valuable observations in the Appendix to the English
edition of  Gerber's Anatomy, and in his notes to  Hewson's works; Simon's Animal
Chemistry,  by'Day (Sydem. Soc.) ; AVharton Jones, On the  Blood-corpuscle consider-
ed in its different Phases of  Development  in the Animal Series, Phil Trans. 1846;
Kolliker, iiber die Blut-Korperchen eines menschlichea Embryo und die Entwickelung
der  Blut-Korperchen bei Saugethieren; Nasse, iiber das Blut; Sharpey and Quain's
Anatomy;  Dr. Miller's  article on Organic Analysis in the Cyclop, of Anat.; Andral,
Essai d'Hematologic Pathologique; Becquerel and Rodier, Recherches sur la Composi-
tion du Sang, &c, 1844  : Dr. Owen Rees on the Blood and Urine;  Mr. J. E. Bowman's
Practical Handbook of Medical Chemistry; Mr. John Simon's Lectures on General
Pathology,  1850.
than in that of the herbivora, are additional facts adduced by Mr. Simon in support
of this view.
  * Monthly Journal of Med. Science, Edinb. Jan. 1851.         f See a case. 
OF THE BLOODVESSELS.
649
                      CHAPTER XXVIII.

THE CIRCULATION  OF THE BLOOD. —THE  SANGUIFEROUS  SYSTEM.—
   ARTERIES.--VEINS.—CAPILLARIES.—THE  HEART,  IN THE LOAVER
   ANIMALS, IN  MAN.—PHENOMENA OF ITS ACTION. — COURSE OF THE
   CIRCULATION IN  MAN.—FORCES  BY AVHICH  THE  CIRCULATION IS
   CARRIED ON IN THE ARTERIES, CAPILLARIES,  AND VEINS.

   It is difficult to comprehend how it escaped  detection for  so long
a time that the complex fluid, the properties of Avhich  were  consid-
ered in the  last chapter,  is perpetually  in motion.  Physiologists
were not insensible of the importance of the  blood to the  general
nutrition of the body; but of its relation  to the elements  of  the  va-
rious tissues, they  seem  to have formed no adequate idea.
   The  discovery of  the  circulation of the  blood by  our immortal
Harvey, and  first  taught  by him  in  1619, was, perhaps, the  most
perfect physiological induction from Avell-ascertained anatomical
facts ever  made.   A careful  study of the anatomy of  the veins and
of their valves, and also of the  heart and  its valves,  and the com-
parison of the possible relation which  these  mechanical contrivances
in the  one, might bear to  those  in the other, led to the  inevitable
inference  that the fluid contained in these vessels and in the heart,
not only moved, but also moved in a certain and uniform  direction.
   The agents of the circulation of the blood, are the  heart and  the
bloodvessels; the latter being a series  of  tubes of various sizes and
structure, and of various vital endowments  ;  the former  a  sort of
living forcing-pump in free communication Avith this system of tubes,
which, by its unceasing action, keeps the  blood in continual motion.
   We shall first examine the structure and vital endoAvments  of each
of these agents of the  circulation, and  then  inquire  into the part
which, each plays in maintaining the circulation of the blood.
   Of the Bloodvessels.—The  bloodvessels  are  of three kinds, Arte-
ries, Veins, and Capillaries.
   The arteries  are the  vessels  which convey the blood  from   the
heart.   The  etymology  of the term (ojjp, *wtJ), shows that it  was
adopted at a period when  nothing  was known  as to  the real nature
of the contents of  these tubes during life.  The fact  that so large
a proportion  of  the arterial system  is  empty after death,  led to  the
opinion, which prevailed to the time of Ilerophilus, that it contained
vital spirits, or  air  [spiritus,  or rtvtvpa), during life, and the arteries
Were Called itvivfia.Tt.xa ayysta.*
   Arteries are cylindrical tubes, whose Avails are formed  mainly by
a high elastic  material, Avhereby the cylindrical form  is  preserved

  * This idea respecting the office of the arteries is thus expressed by Cicero. " Spiri-
tus ex pulmone in cor recipitur et per arterias distribuitur, sanguis  per venas."—De
Nat. Deor. L. ii.
       42 
650
THE CIRCULATION OF THE BLOOD.
and the collapse  of the  tube is prevented.  For the  same  reason
when an artery is cut across, its mouth is patulous, and remains so.
  The Avails of  arteries consist of three different textures: first,
the external tunic, composed of areolar tissue,  and commonly called
the cellular coat; secondly, the middle coat,  or fibrous tunic ; and
thirdly, the epithelial tunic.
  The external tunic is that through the medium of which the artery
is connected with neighbouring structures, and it also forms a  nidus
for  the support  of the  nutrient bloodvessels  of the  arterial Avail.
These minute vessels, named vasa vasorum, are derived from neigh-
bouring arteries; they ramify freely in the external tunic, and send
minute branches  to a certain depth in  the wall of the artery.  In a
well-injected subject, they may be seen  filled Avith injection on all
the larger arteries, and  Avhen great vascular congestion has accom-
panied or preceded death,  these vessels participate in the  general
plethora, and may be  seen distended Avith blood on the aorta and its
larger branches.
  In  some of the large arteries, a  few pellets  of fat may be found
in the outer layers of the external tunic,  which consist of very loose
areolar tissue; the inner layers of this tunic are, however, very con-
densed, and adapt themselves closely to the  middle coat of the ar-
tery to which they  adhere intimately,  probably by reason  of  the
continuity of  some of their fibres  with those  of the middle tunic.
The same elements are found in the external coat of arteries, as in
areolar tissue elsewhere, namely, the white and yellow fibrous tissue,
but the former predominates in quantity  so much that in some situ-
ations it seems to be  the sole constituent of the tunic.
  The extensibility,  toughness, and poAver of  resistance which this
tunic enjoys, by reason of the  large quantity of Avhite fibrous tissue
which it contains, adapt it admirably as  the external  investment of
the arterial tube.  It serves to give mechanical support to the other
tunics, and  being the medium in which the nutrient bloodvessels  are
distributed, it  contributes to a  certain  extent  to  their  nutrition.
Hence there is no other tunic, the loss  of which an  artery suffers
from so much ; in diseased  or  injured states of the other coats, it
preserves the integrity of the  tube, and prevents any serious inter-
ruptions to  the circulation;  the Avail  of many  aneurisms consists in
great part of this tunic ; and, on the application of a ligature, while
the inner and  middle coats give way under the pressure, this tunic
resists and preserves its continuity for a time.
   Of the Middle, or Fibrous Coat.—This tunic constitutes the prin-
cipal  portion of the arterial wall.  It is in greatest part  composed
of yellow elastic  fibrous tissue  ; but it likewise contains some white
fibrous tissue, and also some of the unstriped muscular  fibre.
  When a large  artery,  as the human aorta, or the aorta of a horse
or ox, is cut either longitudinally or transversely, two very distinct
portions may be  observed on examining the surface of the section
Avith the naked eye.  These are, an  internal  portion, quite  yellow
in colour, and constituting not  more than a tenth or a twelfth of the 
THE MIDDLE COAT OF ARTERIES.
651
and an external portion of a grayish-
Fig. 184.
 Finely fibrous layer of the longitudinal fibrous tunic of
the aorta of the horse.—Magnified 200 diameters.
Fig. 185.
 thickness of the Avhole tunic
 yellow colour.
   The internal portion, which we shall call the longitudinal fibrous
 tunic is composed  of longitudinal  fibres of yellow fibrous tissue,
 disposed in two planes, form-
 ing an internal and an exter-
 nal  layer.   The   internal
 layer is in intimate contact
 with  the  epithelium,  and
 consists of fine, pale, some-
 what  flat, not  branching
 fibres, imbedded in a hyaline
 membrane,  which peels  off
 readily  in the length of the
 vessel, and  when separated
 from  connection with the adjacent layer assumes a  coiled form, as
 shown in Fig. 184.   These  fibres are not altered in any degree  by
 the action of acetic  acid.   The external layer is composed of fibres
 of elastic tissue, which also take a longitudinal direction, but are
 much coarser, and branch freely, form-
 ing a very intricate interlacement (Fig.
 185).
   The external grayish-yellow portion
 of the fibrous  coat  of  arteries forms
 nine-tenths  or eleven-twelfths of  the
 thickness of the wall of the artery, and
 may  be distinguished from the internal
 portion  by  the  name of  the circular
 fibrous tunic.   It consists entirely  of
 transverse  fibres, which surround the  artery at  right  angles  to  its
 long  axis.  These fibres separate readily Avhen pulled  in the trans-
 verse direction.  They form a series
 of concentric layers,  in number pro-
 portioned  to the thickness of the
 artery, composed of coarse  yellow
 fibres Avhich branch  and interlace
 freely.
   Upon fine transverse  sections of
 the middle coat of one of the large
 arteries  of man,  or  of the  ox, Ave
may observe the peculiar  arrange-
ment  of  these  branching  fibres
which gives rise to the tendency of
this coat to split into lamellae. Cer-
tain large fibres or  rods of  yellow
elastic tissue are disposed in succes-
sive concentric  circles Avhich  pass transversely, and  sometimes ob-
liquely round the artery.  (Figs. 187,  189, 190.)   These branch  in
a penniform manner  (hence we  propose to call them  the penniform
fibres), and interlace Avith those on  the same plane as  well as with
 Coarsely fibrous layer of the longitudi-
nal fibrous tunic of the aorta of the horse.
—Magnified 200 diameters.
 A portion of the circular fibrous tunic of the
aorta of the horse, to show the reticulation
formed by the interlacement of its fibres.—
Magnified 200 diameters. 
652
THE CIRCULATION OF THE BLOOD.
those on an inner  and  outer plane.   The branches again subdivide,
                and form by their frequent anastomoses that intricate
                interlacement which  is  represented  in  Fig.  187.
Fig. 188.
Fijj. 187.
^fj, ^a^ ^3 ,JJj;, 'rP-

                 Section of the aorta of the ox, showing the arrangement of the two layers of the
                longitudinal fibrous tunic and of the circular fibrous tunic.—Magnified 250 dia-
                meters, a. The epithelial tunic, b. The internal layer of the longitudinal fibrous
                tunic, c. The external coarse layer of the same.  d. A small portion of the circu-
                lar fibrous tunic.  Most of the fibres are cut across, but a few, which take an ob-
                lique course, are seen in their whole  length, and their penniform branching is
                slightly indicated.

                This disposition  of the  fibres may  be  particularly
                well seen  on thin sections made from the  dried aorta
                of the ox, and afterwards moistened Avith  acetic acid.
                It is also sufficiently obvious in the aorta of the human
                subject, but  the  fibres  are  all  very much  smaller,
                nearly one-half the size of those of  the ox, and  the
                penniform subdivision is  not  so distinct.
                   Muscular Fibres.—Interposed between the layers
                of penniform fibres we find  some of the  wavy  white
                fibrous tissue also  arranged in a circular form,  and
                intermingled with  this are some transverse  fibres of
                unstriped muscle, with  oval nuclei, whose long axes
                are  at  right angles to the arterial canal (Fig. 191).
                These do not seem to form any single  uniform layer,
                but  are disposed  probably on different  planes (some-
                what like the fibres of the dartos in the areolar  tissue
                of the scrotum) among the fibres of the circular fibrous
  A section of the whole thickness of the artery, to show the relative extent of the portions of its walla
shown in the preceding figure.—Magnified 40 diameters.
  a. The coarsely fibrous portion of the longitudinal fibrous tunic. 6. The longitudinal fibrous tunic and
a portion of the circular fibrous tunic, c. The entire thickness of the artery.
J 
EPITHELIAL LAYER.
653
coat, and follow the same direction.   They are  best developed in
arteries of the  middle  and  smaller size, and may be most easily
Fig. 189.
^-^^
 A portion of the circular fibrous coat, showing the penniforfh branching of the large rods of elastic
fibrous tissue, each large rod giving origin to multitudes of small interlacing fibres.—Magnified 200
diameters.

separated from the  fibrous tissue in arteries which ITave undergone
slight decomposition.  They are  then seen to  consist of long fusi-
form fibres of much delicacy, with a minute nucleus in most of them.
In the mass, they have the appearance, represented in Fig. 191,

                              Fig. 190.
Fig. 191.
  A single bar or penniform fibre from the circular fibrous tunic of the aorta of the ox, the small fibres
having been broken off.—Magnified 400 diameters.
                                              t
  The external layers of the circular fibrous coat become gradually
more and more like the ordinary yellow elastic tissue,  the penniform
and the muscular fibres cease, and the true yellow elastic branching
fibre becomes  continuous with that which is found
in sparing quantity in the external coat.
  Epithelial Layer.—The interior of the arteries is
covered by a single layer of  delicate oval epithelial
particles, which separate very soon after  death, and
must, therefore, be sought for  in quite recent  sub-
jects.   They may be best seen by scraping the inner
surface of the  artery.   The long  axis of  each  of
these  particles  is parallel  to that  of the  vessel.
They are pointed, or,  as it were, drawn out at their
extremities;  and, according to Henle, they are some-
times  elongated into fusiform fibres.   They are re-
markable for the large  size  and the distinctness of
their nuclei which  are often visible when the  cell-
wall cannot be  detected.   The particles seem  to rest
immediately upon  the innermost layer  of the longi-   uns*riPedf ^"^j
tudinal fibrous tunic,  Avhich  bears the  relation of a  aorta of the horse.—
basement-membrane to them ; in this, when detached,  tersf" e
 
654
THE CIRCULATION OF THE BLOOD.
minute apertures appear  constituting the fenestrated  membrane  of
Henle.   It is possible, as suggested by Henle, that this membrane
arises from the transformation of the epithelium, which is ever draw-
ing the materials of its formation and nutrition from the blood con-
tained in the artery.   Thus, it is not improbable that the innermost
layers of  the arterial wall, at least, are nourished  from the blood
flowing through the artery, and not from the blood of the vasa vaso-
rum, which do  not  seem to  penetrate  to them.   And  this view is
supported by observing  that  these  innermost layers of the artery,
i. e. the longitudinal fibrous tunic, are the seat of the atheromatous
deposits which are so common in peculiar  diatheses, or at an ad-
vanced period of life; these deposits being  doubtless derived from
the blood which traverses the artery.

                                             Fig. 193.
&

 Epithelial particles from the
aorta of an ox.—Magnified 400
diameters.
 Particles of epithelium and nuclei from the
aorta of ahorse; some of the former exhibit
the elongated character.—Mag. 200 diameters.
  From the preceding description, it would appear that the following
tunics may be enumerated as constituting the wall of an artery pro-
ceeding from without inwards.
  First, the external coat, consisting of areolar tissue.
  Second, the circular fibrous coat, consisting of a series of lamellae,
composed of yellow elastic fibrous tissue, the most external of which
are intermingled with white fibrous tissue and with circular muscular
fibres.
  Third, the longitudinal fibrous layer, which consists of two layers,
a finely fibrous,  and a coarsely fibrous.
  And lastly, a layer of epithelium.
  The internal  layer of longitudinal fibres—which  is the same as
that described by Henle under the name of fenestrated membrane—
constitutes, along with the epithelium, the  internal tunic so long
recognized by anatomists.
  The elastic reaction of arteries  is evidently resident in the middle
fibrous coat,  and in the  same tunic the contractile power of the
artery resides.   The existence  of these two forces in the arterial 
COATS OF ARTERIES.
655
 wall, the one of simple elastic reaction, the other of a slow muscular
 contraction, is shown  by  the  well-known  experiments  of John
 Hunter.  A piece taken from each of the large arteries of a horse,
 bled to death,  was laid open and extended on a  flat surface without
 stretching; it was then measured, and afterwards subjected to strong
 tension; it was then measured again ; on the  removal  of the stretch-
 ing force, it failed to recover itself to its first dimensions by a notable
 difference.   When an animal has been bled to  death, the arteries
 are in their greatest  state of contraction, the quantity of blood cir-
 culating in  them being reduced to a minimum.   This state of con-
 traction, Hunter  assumed to be the  result of muscular force,  and
 with good reason, as, after  stretching, the artery did not contract
 to its previous dimensions.   The stretching  destroyed the muscular
 force, leaving  whatever contraction would take place on the removal
 of the stretching,  to be effected by the elastic force.   Thus a piece
 of the aorta of a horse, when slit up and opened on a plane surface,
 measured five  inches and a half;  on being stretched, it lengthened
 to ten inches  and a half;  the stretching power being removed, it
 contracted again six inches,  " which," says Hunter, " Ave must sup-
 pose to be the middle state of the vessel."*   These powers inherent
 in the arterial wall, of yielding under a distending force, and react-
 ing upon its contents with a force equal to that of the primitive  dis-
 turbing one, and also that of muscular  contraction, exercise an im-
 portant  influence  in  promoting or directing  the circulation of  the
 blood through  the arterial system.
  The elastic  element of the arterial  tunic is ahvays developed in
 the direct ratio of the size of the artery; and the muscular element,
 although perhaps not bearing an  inverse proportion to the size of
 the artery, yet becomes more prominent and distinct as the elastic
 tissue  diminishes  in coarseness and in strength.  Thus it is'in  the
 smaller  arteries that we notice the  most perfect arrangement of
 muscular fibres, and in these the fibrous tissue is reduced to its in-
 ternal longitudinal fibrous layer, the  external circular fibres having
 disappeared.
  Bloodvessels  and nerves  are freely  distributed to  the arterial
 tunics.   To the former, allusion has already been made in describ-
 ing their external tunic.  We have no  evidence that these blood-
 vessels penetrate  further than to  a slight depth into  the  fibrous
 tunic.   It is probable, therefore, that they are destined to nourish
 the external tunic, and a portion  (chiefly the muscular element) of
 the fibrous   tunic, leaving  the remainder of the arterial wall to
imbibe its nutrition directly from the blood  itself.   The general
arrangement of the nerves  on the outer coat of arteries  has been
already  described  (vol. i. p. 223, and vol.  ii.  chap.  xx.).   The
plexuses formed are chiefly  conducted by the arteries to parts  be-
yond ; but they also furnish filaments  penetrating to the muscular
fibres, and bringing these into relation with the nervous system.
  The arterial  system may be described as taking its  starting-point
from the heart, by the attachment  to that organ of ea»ch of the two
* Hunter on the Blood, Inflammation, &c, 4to. ed. p. 124, ct seq. 
656
THE CIRCULATION OF THE BLOOD.
great vessels (the aorta and the* pulmonary artery) which form the
main trunks of their respective systems.  The middle coat of each
of these vessels is inserted into or adherent to the concavity of three
festoons composed of rounded cords of white fibrous tissue.   To the
central portion of the convexity of each of these the muscular fibre
of the heart adheres closely in the case of the pulmonary artery ;
but in that of the aorta, one  festoon and the  half  of another gives
attachment to muscular fibre, whilst the other half of  this festoon,
and  a third  are attached to a part of the fibrous^zone,  which forms
the base of the inner lip of the mitral valve.   Along the line of these
festoons the lining membrane of the heart, becoming continuous with
that  of  the  arteries,  forms  three  semilunar curtains, which are
strengthened by processes of fibrous  tissue continuous with the
festoons.  These folds  constitute the valves  of  these  vessels,  the
only ones of the arterial  system.   We shall recur  to these by and

   Arteries convey the blood to the various parts  of the body by the
subdivision of their trunks and the giving off of branch-vessels at vari-
ous points.  The branches for the most part come off at an acute angle
with the continued trunk, so that  the neAv stream of blood does not
experience any  great diversion  from  the direction of its  parent
stream.   In a feAV instances, hoAvever, this arrangement is not ob-
served, as in some of  the intercostal  and  lumbar arteries, which
form nearly a right angle with the aorta from which they originate.
   Anastomoses of Arteries.—The manner in which different  arterial
trunks communicate with  each other indirectly,  is  one of the most
interesting  points in the  anatomy  of the arterial system.  This
anastomosis of arteries often affords the means  of supplying the
nutrient fluid to a limb after its principal artery has been obliterated,
small collateral  channels enlarging more or less for the reception of
a greater supply of blood than they  were wont to convey.    Hence
the study of the intercommunicating  vessels has had great influence
upon the  surgical treatment of aneurisms and Avounds of arteries.
   One of the most simple of these anastomoses is found in the union
of tAVO arteries,  originating from  different trunks,  to form  one—as
the vertebral arteries unite to form the basilar ; another kind is, Avhen
two  vessels from the same or different trunks form by their union an
arch from the convexity of which others come  off, which form similar
reunions and arches, giving off smaller branches which take a similar
course, and  the  arrangement continues to be repeated until the
resulting  branches are reduced to a very small size, Avhen they pass
into the capillary system.   This mode of frequent subdivision and
anastomosis is seen in the arteries which convey blood to the intestine
—the mesenteric arteries.   A third form is where two neighbouring
arteries communicate by a distinct vessel, which  passes from  one to
the  other.  By  such vessels the remarkable anastomosis at the base
of the brain, the circle of Willis,  is  formed.   The  anterior  cerebral
arteries passing upwards and forwards are united by a cross branch,
the anterior communicating artery,  and the  carotid artery  on each
side is united to the posterior  cerebral artery by a branch Avhich 
ANASTOMOSES OF ARTERIES.               657
passes from before backAvards—namely, the posterior communicating
artery.  By this free communication  of the  arteries  in front with
those  behind, and of those on the right with  those on the left, the
brain is protected against loss of blood, if any of the main channels
of its supply should be stopped.
   The most common form of anastomosis is found in the limbs.   Two
principal  channels  convey blood to a  limb, as in the forearm, the
radial and ulnar arteries.   The branches  of these arteries communi-
cate at various points, especially in the vicinity  of the joints, and thus,
if any impediment occurs in  either,  the  other enlarges, conveys an
increased quantity of blood, and  even  the obstructed  trunk beyond
the  point  of obstruction  receives  a supply  by the  anastomosing
branches.   Or the single main artery of a limb, the femoral, or the
brachial, by its branches communicates with arteries which, originat-
ing  from  different  sources, pass  into  another portion of the limb.
Thus,  in the thigh, the circumflex branches of the profunda anasto-
mose with  branches which  descend from the gluteal, sciatic,  and ob-
turator arteries, which are branches of  the internal iliac.   Hence
an obstruction in the femoral, high up, or even in the external iliac,
will  not deprive the limb of its due  supply of  blood, for the  arteries
just  named will convey blood  to the branches  of the femoral, which
arise below.   This  anastomosis  may compensate for an obstruction
in the  internal iliac near its origin, and by a reflux of blood from the
femoral through the profunda arteries  supply  the lower part of that
artery.  In the treatment of wounded  arteries, the surgeon must
always make allowance for the anastomoses in the neighbourhood of
the wound.  It rarely happens that a  single ligature on the cardiac
side  of the wound is sufficient to guard  against' secondary hemor-
rhage ; the anastomotic branches which arise  from the main  artery
above  the  wound supplying  the  vessel or its  subdivisions beloAV, so
that  the blood finds its  way by a reflex course to the  distal part of
the  trunk  of the artery, and to the  wound.  This is very apt to
occur in  wounds of the brachial artery  at the  bend of the elboAv.
The  only and the obvious method of guarding against such an effect
of arterial anastomosis, is to  apply a ligature to two  points of  the
artery, viz., below the wound, as well as above it.
   The supply of blood to various segments of  the body through  dif-
ferent  channels, and the free communication of these channels with
each other, must be  regarded as  one  of  the most beautiful  of  the
various mechanical contrivances in  the  human  body.   By such an
arrangement a considerable security is obtained against the failure
of the nutrition of the limb by the stoppage of one of its channels.
And modern  surgery is largely indebted  to it for  one of its most
brilliant triumphs.
   The passage of the  blood into  a  limb  or  organ through  various
channels serves to distribute it more equally,  and to relieve the  ele-
mentary constituents of the limb or  organ from the impetus Avhich
the entrance into it of a single large column  of blood  would  occa-
sion.   This provision is especially secured for  the brain by the sub-
division of the four great streams of blood Avhich enter the cranium 
658
THE CIRCULATION OF THE BLOOD.
 into several minor ones at the base of that  organ, which again un-
 dergo extreme subdivision before they penetrate the nervousTmatter.
 In animals that hold their heads low, the subdivision of the carotid
 and of the vertebral arteries is very remarkable, and gives rise to
 the formation of the different kinds of rete mirabile.  The most re-
 markable instance of the  subdivision  of arteries, prior to the pene-
 tration of the tissue they are destined  to  nourish, is that described
 by Sir A. Carlisle, in the  Sloth, which seems to  be connected with
 the extraordinary  poAver  enjoyed by those  animals  of sustaining
 muscular action for a lengthened period.
   The anastomosis of the  smaller arterial ramifications are also of
 great  importance in many  of the organs and tissues, especially under
 the skin and mucous membranes.  Here a membranous  expansion
 is supplied by a great number of distinct twigs which form a plexus
 everyAvhere continuous, and which again gives rise to other smaller
 plexuses before the ultimate capillariesNare given off.   To this  form
 of  anastomosis of the smaller arteries may perhaps be ascribed the
 tendency of some inflammations of membranous parts to be propa-
 gated  rapidly  along an  extensive  surface,  as  in  erysipelas.   In
 some organs, as the kidney, the arterial twigs have no anastomosis
 whatever.
   Of the Veins.—The veins  carry the blood back to the heart from
 the various tissues and organs.   As the arteries  divide  and subdi-
 vide, the veins follow a contrary course.  They commence from the
 capillary plexuses of the tissues and  organs by minute radicle ves-
 sels, which by their junction form larger ones, and these again unite
 to form still larger ones; and so by the fusion of the  smaller veins
 larger trunks  are produced, until at length the  venous blood, from
 all  parts of the body, is returned to the heart by two great venous
 trunks, the superior and the inferior venae cavae.
  Veins are much  more  numerous,  and  for the most part more
 capacious than arteries.  In  the extremities and the trunk they are
 arranged upon two  planes, a superficial  plane and  a  deep-seated
 one;  the latter accompanying the deep-seated arteries, the former
 being immediately subjacent to the skin.   The superficial veins are
 more numerous and present greater variety, both  as to  number and
 arrrangement, than the  deep veins.   Their  smaller  radicles anas-
 tomose in the same manner as has been just described in the arteries.
  A distended vein has a cylindrical form, which, however, in some
is interrupted here  and there by a knotted  appearance, caused by
its enlargement at the situation  of its  various sets of valves.  The
coats of veins are essentially the same as those  of arteries, but are
less developed.   Proceeding from without inwards, we find, first, an
external tunic, composed  of a thin layer of areolar tissue,  answering
in structure, position, and function to the external coat of arteries.
Secondly, Ave find a fibrous tunic of which the outer portion consists
of circular fibres; the inner portion of longitudinal fibres both coarse
and fine.  The circular fibres are but  slightly developed; they are
of the  same nature as those in arteries and in the larger veins, and
exhibit somewhat of the  penniform disposition, which we have de- 
CAPILLARY VESSELS.
659
 scribed in the fibres of the arterial  circular tunic.   With them are
 mingled unstriped muscular  fibres in less quantity but of precisely
 the same form and character as those in arteries.  In the veins near
 the  heart, these  circular fibres are replaced by similarly disposed
 muscular fibres of the striped kind, continuous with and resembling
 those of the auricles.*
   The longitudinal fibres are well developed, consisting of the outer
 coarse  layer,  which, in  the large  veins,  as  the cava  ascendens,
 are arranged in the form of large  bundles, parallel to the long axis
 of the vessel, and the internal layer or fenestrated membrane, which
 in every respect corresponds to the internal longitudinal fibrous layer
 of arteries.   Upon this is placed the  epithelium, Avhich is precisely
 the same as that  of  arteries.
   The  imperfect  development in veins of  a  tunic  possessing much
 elastic power,  like the circular fibrous coat of  arteries, explains the
 readiness Avith which these vessels  collapse, and the  general thin-
 ness  of the fibrous  and areolar tunics accounts for  the diaphanous
 character of the venous wall.
   In a large portion of the venous system peculiar processes, called
 valves,  are found  projecting into the interior of the vessel at various
 points.   These processes are semilunar, attached by  their convex
 border to the wall of the vein, and free at their concave border, which
 is a little thickened.   They are disposed in pairs in immediate juxta-
 position—sometimes there are three placed  together.  They  are
 most numerous in the  superficial or  subcutaneous veins ;  and  are
 more so in the veins of the lower half of the body than in those of
 the upper.   The  smallest veins are  destitute of valves; as also are
 the largest, as the cavee.  The pulmonary veins, those of the liver,
 and all the veins  which contribute to the hepatic portal system, the
 splenic  and mesenteric veins, want valves.  The renal veins are also
 devoid of them.
   The tissue of which these valves are composed  is the same as the
 longitudinal  fibrous coat of the vein, covered  by a layer of epithe-
 lium ; the  valves  cannot be properly described as reduplications of
 the inner membrane  of the veins, they are processes of it.f
   Of the Capillaries.—The system of vessels which is intermediate
 to the veins and arteries, is called by the name  capillary, from the
minuteness  of their  size.   The finest arteries, and the finest veins
likewise, receive this appellation.  But the true capillary system is
 distinguished by a speciality of arrangement  and an uniformity of
size, proper to each tissue or organ.
  The capillary vessels may be examined in injected specimens, or
in recent transparent tissues, as in the pia mater, or in living trans-
 parent tissues, as  the web of the frog's  foot, the mesentery  or dis-

  * Rauschel states that these fibres can be traced in the superior cava, as far as the
clavicle, and in the inferior as far as the diaphragm, and in the pulmonary veins as
far as the first subdivision of each.
  + We have great pleasure in referring to an excellent article on the anatomy of veins,
in the 42<1 part of the  Cyclopaedia of Anatomy and Physiology, by Dr.  S. J. Salter. 
660             THE CIRCULATION OF THE BLOOD.
tended urinary bladder of the frog, the tail of  the  newt, the gill of
the tadpole, the tail or fins of fishes.
  The diameter of the capillaries varies in different textures  from
the yq'go  °f an inch> to 4?4o"o> according to the measurements of
Weber.
  The finest capillaries are  found in the brain (Fig.  195, a) and in
the retina; those of muscles, especially the cross branches which in-
tersect the fibres, are likewise very fine.  Among the largest are
those of the lung and liver.
  The capillaries form  a network in each tissue  or organ, which
                     derives its nourishment  directly from them,
       Fig. 194.        and they exhibit an arrangement adapted to
      .^r^c-*~        the disposition of its proximate elements.  In
   ^'-J^x2\^'yr     ^e tissues which  assume  a  fibrous  form, as
  ^^V^vOSk2^   muscle,- nerve,  fibrous tissue, the capillaries
 rP^^^sV1!   are disPosed in lines parallel to the fibres, and
 ^?££^></^.-'oD  these  parallel vessels are  united at variable
 ^-C^^^w^ ^s^   intervals by  cross  branches,  Avhich pass at
  V^^TV>f V^rT    right  angles  to  the fibres.  (See Figs.  47,
   ^iH^O^'vr''     ^5, ^"^ "^^' an<^ 194.)   In  compound or in-
       •^v            voluted mucous membranes,  the capillaries
  Arrangement of the capii-  form  a plexus  with more or  less circular
larics on the mucous  mem-     .      i • 1           i •  p       l
brane of the larjre intestine in  meshes, which correspond in  form and  size to
fied5hoTameteUrfct~Magni"  the arrangement of the membrane—good ex-
                     amples of  this are  found in the mucous mem-
brane of the stomach and of the intestines (Fig. 194).  When the
elements of  the mucous membrane are prolonged into processes,
forming villi or papillae, each villus or  papilla is found to possess its
plexus or  system  of  minute capillary vessels  (Figs.  161 and 162).
In  the simple  mucous membranes, and in serous  membranes, the
plexus of  capillaries placed in the  submucous  or subserous areolar
tissue exhibits large and irregular meshes.
  In the compound tissues  the capillaries  have no  direct relation
to the ultimate anatomical  elements—that is  to say, these minute
vessels do  not ramify among the ultimate particles  of the tissues.
  It is with  their proximate elements  they  connect themselves.
Thus in muscle the vessels lie between the fibres, and are  separated
from the sarcous particles by the sarcolemma;  in nerve, in the  same
way, they are separated from the  nervous matter by the  tubular
membrane ;  and in the vesicular matter they play around the vesicles
and do not penetrate them.   In most of the mucous membranes, the
basement-membrane is  placed between them  and the epithelium,
their nidus being the sub-basement tissue.   So, also, with the serous
membranes.  In bone, the finest vessels are very remote from  a large
portion of  the  constituent   osseous particles ; ramifying through
Haversian canals, they come in contact only with the osseous parti-
cles of those layers which  immediately invest  each canal; or with
the periosteal or medullary layers.  Vessels  do not penetrate  arti-
cular cartilage at all, which must therefore draw its nourishment
from the \Tessels of neighbouring tissues. 
CAPILLARY VESSELS.
661
  The  finest capillaries, such as  may be most easily examined in
connection  with the  pia mater of the brain, appear to consist of a

                               Fig. 195.
 A. A capillary vessel from the vesicular matter of the human brain, a. Homogeneous wall.  b. Nu-
cleus of the wall. c. Ked blood-corpuscle.
 B, C Different appearances of small arteries and veins of the human pia mater, a, a. Homogeneous mem-
brane. 6, 6. Circular fibres, c, c. Oval nuclei of the internal epithelium, hereabout to cease,  d, d. Trans-
verse indications of the circular fibres.
 D. Capillary artery from the mesentery of a rabbit.—Magnified 200 diameters.

homogeneous tissue, interrupted at  short intervals by nuclei which
adhere to,  or are imbedded  in the wall of the vessel.  (Fig. 195, A.)
These nuclei are  mostly oval—sometimes  nearly circular;, most of
them have their  long  axes  directed parallel to the course of the
vessel, but some are placed  transversely.   In some of  these   fine
capillaries, very faint  indications of  a circular  striation  may be
seen.
   In some larger A^essels, which perhaps may with more propriety
be regarded as  capillary arteries, rather  than as  true capillaries, a
distinct  arrangement of  circular fibres may be seen.   These fibres
are  flat, uniform in  diameter, devoid of  nuclei, and in all respects,
but this, resemble the unstriped  muscular fibres.
   It had  long  been a  question  among  physiologists,  Avhether the
capillaries, had proper walls distinct from the  tissues to which  they
supplied blood.   The microscope has  settled  this  question in the
affirmative, for most of  the tissues  and  organs of the body ; but it
may still be doubted Avhether the finest capillaries of the  liver  have
walls distinct from  those cubical masses of epithelium Avhich  they
permeate.
   Although it  is  the rule that an intermediate  system  of vessels
exists between the arteries  and veins, we  find two remarkable excep-
tions to  it.  One is  in the  erectile tissue of the penis; the other in 
662
THE CIRCULATION  OF THE BLOOD.
the uterine circulation.   In both these  instances, the  arteries com-
municate directly with the veins.  In the penis, the ramifications of
the arteries pour their blood into the cells of the corpora cavernosa;
in the  uterus the small curling arteries of Hunter  open directly into
large  venous sinuses, Avhich in the  gravid uterus form an  intimate
relation of contact Avith the villous processes of the placenta.   These
points  will be fully described in the  chapter  on Generation.
   It  is not improbable  that  further  research may detect  a  direct
communication  between  arteries and  veins,  even  in  tissues,  the
greatest part  of which  is furnished with a true capillary plexus.
In the cancellated structure of bone,  and the diploe of the cranial
bones,  it  seems highly probable that  the arteries communicate im-
mediately with the veins  at many points.   Mr. Paget*  describes a
direct  communication between  the arteries and veins of the wing of
the bat, without any intermediate capillary plexus.f
   Of the Heart.—This hollow muscular organ, which, like a forcing-
pump,  drives the blood throughout the vascular system, varies in its
constitution, according to  the  complexity of the circulation, from a
simple muscular tube, such as the  dorsal vessel  of insects, to the
complex double heart of man,  with its four cavities and its beautiful
apparatus of  valves.

  The dorsal vessel of insects is the most simple condition of the heart.  It consists
of a muscular tube provided with certain valves, disposed like those of veins;  these,
by affording an obstacle to the flow of the blood in one direction, determine the course in
which it is propelled by the contraction of the muscular wall, namely, towards the head.
It is situated along the middle of  the back, whence its name.  At the points which
correspond to the situation of the internal valves, it exhibits distinct constrictions,
which in some insects are so marked, that the vessel appears to consist of "a series
of slightly conical segments, partially sheathed one upon the other."  (Owen.)  The
  * Lectures on Inflammation.
  | The communication between arteries and veins by capillaries was not known
to Harvey.   In his time, and for a long period afterwards, anatomists supposed the
blood to pass into the parenchyma of the tissues,  whence it was received or withdrawn
by the veins.  Malpighi (about 1687), by microscopic examination, first demonstrated
the intermediate  capillary  system in the lungs and urinary bladder of the  frog.
Leuwenhoek afterwards (1729) pursued  this investigation, and has given some good
illustrations of the capillaries examined in transparent parts during life.
  Dr. Hales, in this country, many years later (1769), gave a very accurate descrip-
tion of these vessels, and denied altogether the  idea of the intervention of a paren-
chyma, or, in his own words, of "glandular cavities."  See his Hcemastalicks, p. 146,
§ 9, vol. ii.   AV. Cowper, the distinguished myotomist, also made observations on the
capillaries of the  transparent parts of warm-blooded animals, as the mesentery of a
dog, and the omentum  of a cat.   Haller threw great light upon the subject, and by
his facts and arguments, settled the question as to the direct continuity of arteries
and veins.   Subsequently (1745), Lieberkiihn advanced our knowledge of  the capil-
laries by his numerous  injections, most of which  are still extant at Vienna.  In  more
recent times, the distinguished Prochaska seems  to have been the first.to form a just
appreciation of the extent of the capillaries, and of their exact relations to the elements
of the tissues.  His description of the disposition of these vessels,  based upon the ex-
amination of Lieberkuhn's and his own  injections, can scarcely be surpassed in the
present day.   See the 9th chapter (de vasis saguin. capillar.) of his Disquisitio Anat.-
Phys. Organismi Corporis Hum. ejusque Processus Vitalis. Vienna, 1812.  Bichat,
indeed  (1801), had  erected  these vessels into a system intermediate to that of the
arteries and of the veins, but no anatomist who compares the descriptions of the two
writers  will  hesitate to give to the former the  merit of a more intimate practical know-
 edge of the anatomy of these vessels. 
THE  HUMAN HEART.
663
 blood is propelled to the head through a tubular prolongation  of the dorsal vessel,
 which corresponds to the aorta;  this divides into numerous branches, which soon lose
 JS!  T*tm ■    f^  ' °r ditfused sinuses,  which occupy the spaces  between the
 tpnrt n  i   *m8e« ;/rT theSe Sinuses' as from veins' the blood is returned to the
 „v, ''? enter" tha*tube at several points, at its posterior or caudal extremity, as
 t ni\tl nf\TT  a^rtZQS Which are found on each side of tlie dorsal vessel, near the
 points of attachment of the valves.
 ri'l^o8^^' .the,heart is "kewise of a very simple form.  In  some of the lower
 r]^  n  .1  ls,slmP]f ,a,muscu ar vesse1' as in ^sects; in the higher animals of this
 class, as in crabs and lobsters, it forms a distinct muscular cavity* or ventricle, giving

 ZHif^'i    P1CrCed ^ SeVei'al Ven°US °rifices  through which the blood is
 pouied  fiom the  large venous sinuses which receive it on its return from the body.
 It is situated, as in insects, beneath the enlargement of the back

 1  i° rnef+,°11USC-°U^Cla-88eS thG heart StiU retainS «reat simpHcity of structure.  In the
 lowest of these, as Tunicata, it is still a muscular vessel, propelling the blood through
 arenes which ramify on the respiratory organ, whence it is  taken  up by veins, and
 returned to the heart   In the  compound Ascidians,  we meet with the remarkable
 phenomenon of the oscillation of the currents of the circulation, under the influence of
 a change m the direction of the peristaltic contractions of the heart
   In the Acephalous mollusks, we first observe the subdivision  of the heart into two
 compartments,  or cavities;  an auricle which  receives the blood from the veins and
 transnu  s it to a fusiform ventricle which drives it to the various parts of the body   In
 one of the most highly organized of the Acephalous mollusks,  Venus  chione, Professor
 Owen describes two auricles, which receive the blood from the veins of the gills  and
 transmit it to the single  fusiform ventricle, which is perforated by the rectum- and in
 the genus Area, the ventricle is divided into two cavities,  having the rectum in the inter-
 space.   An artery is continued from each extremity of the ventricle, which distributes
 the oxygenated blood over the viscera, the muscular  system, and the mantle   The
 heart ot the Gasteropoda, likewise, consists of a single ventricle, which propels the blood
 to the viscera and the muscular system of the body, and receives  it from the branchiae
 by one, and sometimes by two, auricles.
   In the Cephalopoda, the most highly organized mollusks, the  general  plan of the
 heart is the same  as in the Gasteropoda.  The venous blood is  received from all parts
 of the body by great venous sinuses,  which also take up the blood from the gills- the«e
 veins communicate with the heart, which consists of a single cavity, whence arise the'
 two mam arteries of the  body, called the superior and inferior aorta.
   In Fishes, the heart consists of two cavities; one, large, loose, and thin-walled
 which receives the venous blood—the auricle; the second,  thick  and  fleshy—the  ven-
 tricle, whence an artery springs, the first portion of which,  dilated and surrounded by
 thick muscular fibres, constitutes  what is called the aortic bulb.
   In the Batrachian reptiles there are  two auricles, one which receives the blood from
 the veins of the body—the systemic auricle ; the other, which receives it from the luno-s
 the pulmonic auricle.   Both auricles communicate with  a single ventricle, whence the
 blood is  propelled throughout the body, as well as to  the lungs.   In s'erpents, the
 heart presents a similar structure; but in the Python the ventricle is divided by an
 imperfect  septum into two chambers, one  of  which communicates  with the aorta,
 the  other with  the  pulmonary • artery.    In the Saurian reptiles,  likewise,  there
 are two auricles, and a ventricle, which latter is subdivided into two or more cavities,
 communicating with each other, and  with certain arteries which spring from them—
 excepting in the American  alligator (Crocodilus lucius), in which the existence  of a
 perfect septum creates two distinct ventricles.
  In Birds and Mammals, the heart exhibits its highest development,  consisting, as it
 does, of two auricles and  two ventricles, separated by a complete septum; each auricle
 communicating with its proper ventricle,  and each ventricle giving rise to an arterial
 trunk.


   The  human  heart, in the adult subject,  occupies  an oblique posi-
 tion in  the thorax.   Its apex is directed  downwards,  forwards, and
 to the left side, and in the  quiescent state corresponds  to the inter-
 val  between  the  fifth  and  sixth ribs.   Its  base corresponds  to the
interval between the third or  fourth, and the  eighth  dorsal vertebrse,
from  which  it is separated by the parts contained  in the  posterior 
664
THE CIRCULATION OF THE BLOOD.
mediastinum.   The  base of the heart corresponds in front to the
sternum, at about the level of the cartilage of the third rib.
  The weight  of the human heart in the adult is  about 11 ounces
for the male, and 9 ounces for the  female (John  Reid).
  The two great arteries, the aorta and pulmonary arteries, spring
from the base of the heart in front.  Posteriorly, the  base is formed
by the auricles.
  Both the anterior and the posterior surfaces of the heart are divided
into two, by means of a groove which corresponds to the anterior
and posterior margins  of the septum of  the  ventricles, and which
passes from base to apex.  The  anterior groove contains the left
coronary artery and  vein ;  the posterior, the  right coronary artery
and vein.   These are accompanied by nerves.   A transverse groove
of considerable depth separates the auricles  from the ventricles; it
contains the coronary vein.  All  the grooves contain a greater or
less quantity of fat, which  envelops  the vessels and  nerves lodged
in them.
  Of the four  cavities of the human  heart, a ventricle and auricle
are on each side of the  median groove.  The ventricles  are  cone-
shaped cavities, their apices being  directed toAvards the apex of the
heart, their bases corresponding to the auricles.   The left ventricle
forms the apex of the heart.   When  the right  ventricle is dilated,
its Avail extends to, and  contributes to form, the apex.  Each ven-
tricle, when laid open, exhibits  two distinct  parts;  one, which  com-
municates Avith the auricle by a large and free aperture, called the
auriculo-ventricular orifice, through which the blood passes from the
auricle  into the ventricle; the other, called  the  infundibulum, a
funnel-shaped channel, which leads to the artery, and through Avhich
the blood is propelled into it from the cavity of the ventricle.
   The  Valves of the .Heart.—The auriculo-ventricular  orifice  on
each side is guarded by certain valves  Avhich, when  not in  action,
lie in the ventricle.   The valve of  the left side consists of two trian-
gular curtains,  from the  free margin and  part  of the  ventricular
surface of which tendinous chords (chordae tendinese) pass to various
points of the wall of the ventricle.   The bases of these curtains are
attached along a fibrous zone, Avhich separates the auricle from the
ventricle.   This valve  is  known by the name of the mitral valve,
and the orifice is called the mitral  orifice ; the larger  curtain is that
which  separates the infundibulum from the body of the ventricle.
The valve at the right auriculo-ventricular orifice, consists of three
portion?, each  having a pointed free extremity extending  into the
ventricle, and connected to its wall by tendinous'cords.  Hence this
is called the tricuspid valve.  The  base of each.segment corresponds
to the fibrous  zone which  intervenes  between the  auricle and ven-
tricle.   Of  the three curtains, of which the  tricuspid  valve consists,
the largest is anterior, and the next in size corresponds to the in-
fundibulum  of the ventricle.
  At each of  the arterial orifices  of the ventricles there are three
valves of semilunar  form (Fig. 199), which  effectually close the
mouth of the artery against the regurgitation of blood into the ven- 
CAVITIES AND VALVES OF THE HEART.          665
tricle.   Each of these valves has a convex border  attached  along
the fibrous zone, which connects  the artery to  the  infundibulum of
the ventricle ; and a free concave border divided by a small round
body of fibrous tissue {corpus Arantii) into two equal portions.  As
the blood flows from  the ventricle, these  valves lie up  against the
wall of the artery ; but immediately the blood  regurgitates  towards
the ventricle, they are pushed by it  in towards the mouth of the
artery; and  their free margins, as well as a considerable portion of
their ventricular surfaces coming into close apposition, an effectual
barrier is formed against the return of the blood.   The semilunar
valves of  the aorta are  essentially the same  in all points  of form
and structure as those of the  pulmonary  artery; but those of the
aorta are the stronger.
   The inner  surface of the  wall  of the central cavity of each ven-
tricle is marked by very  numerous fleshy columns (carneee columnae)
which project from it in  relief.  There are three orders of them ;
first, the simple column in relief,  which adheres throughout its whole
length to the wall of  the ventricle;  secondly, the column, attached
at each extremity, but free  in the interval, so  that a probe  or other
instrument may be passed beneath its middle part;  and thirdly, the
column attached at one extremity to  the  wall  of the- ventricle, and
projecting into its cavity by the other; these last are  distinguished
from  the  others by the  name of musculi papillares ; the chordae
tendinese  spring from their free extremities, and are inserted into
the mitral and tricuspid  Aralves, and one or tAvo into the wall of the
ventricle.  The infundibular portion of the ventricle  is  perfectly
smooth on its inner surface, and  quite free from columnae carneae.
   The auricles are thin-walled  muscular bags, of irregular someAvhat
cuboidal shape.   Each communicates by a wide orifice, with its cor-
responding ventricle,  and is  separated from its fellow by a thin fleshy
septum, which, at  its middle, is  so thin as to be translucent.   At
this situation an  orifice  existed during intra-uterine life, through
which  a communication took place between the auricles (foramen
ovale, or Botalli).   Each auricle has two distinct portions; the sinus
venosus, which forms  by  far the greater portion of the bag, and the
proper auricle,  or auricular appendage, which  appears like an off-
shoot from the  former, somewhat in the shape of a dog's ear, pro-
jecting forwards on each side  of the aorta and pulmonary artery.
The veins  pour their blood into the  sinus venosus;  the auricular
appendage receives no bloodvessels, but its cavity communicates with
that of the sinus venosus.   The right auricle receives the two great
veins  of the  system, and  the great  venous trunk of the heart, the
coronary vein.  The superior vena cava opens into  the upper angle
of the right  auricle, passing downwards and forwards ; the inferior
cava opens into its  lower angle, passing  upwards, backAvards, and
inwards.   The coronary vein opens between the mouth of  the infe-
rior cava  and the auriculo-ventricular orifice.
   On laying open the right  auricle, by an incision extending between
the two vense cavse, an intricate  arrangement of muscular  bundles,
called musculi pectinati,  may be seen on its outer Avail.   These fleshy
       43 
666
THE CIRCULATION OF THE BLOOD.
columns interlace freely with each other.   On the septum a depres-
sion exists about its middle, called the fossa ovalis, nearly surrounded
by a thick fleshy ring called  the  annulus ovalis.   This marks the
situation  of the orifice already alluded  to, which existed  during
intra-uterine life—the foramen ovale.
  To  the  left of the orifice of the  inferior vena cava, there is a val-
vular  process which is another remnant of a mechanism adapted to
the circulation through the heart in  intra-uterine life.  This  is the
Eustachian  valve.  It is  a process  of the inner  membrane of the
auricle, of semilunar  shape, which projects between  the vena cava
and the auriculo-\*entricular orifice, and in the foetus served to direct
the ascending current of  blood through the foramen ovale into the
left auricle.   The  orifice of the coronary vein is guarded by a small
valve  called the valve of Thebesius.  Several small orifices are seen
scattered  over the  inner surface of the  right auricle, called foramina
Thebesii; some of these are the  openings of small veins from the
wall of the  auricle ;  others merely  lead  into depressions between
the muscular fibres of the auricular  wall.
  Four veins pour their blood into  the left auricle ;  these  are the
right  and left pulmonary veins, two  on each  side.   The left veins
open quite close  to  each  other.   The left auricle is placed in the
concavity of the aorta, and has lying in front of it the roots of both
the aorta  and the pulmonary artery.
  The inner surface of the left auricle is  perfectly smooth, covered
with an opaque lining membrane, which appears somewhat thicker
than  that of the  right side.  There  is  no appearance of musculi
pectinati in the left sinus venosus;  a  few, however, exist on the inner
wall of the auricular  appendage.   Here and there  some orifices are
seen,  leading to depressions in the Avail of  the sinus venosus.  On
the left side of the septum, between the auricles, we  observe  traces
of the valve-like portions of the septum, which formed the immediate
boundary of the foramen ovale during  foetal life.
  Of the Pericardium and Endocardium.—The heart  is inclosed
in a fibrous bag, the fibrous pericardium,  which is  closely adherent
beloAV, to  the central  tendon of the diaphragm, and above, becomes
continuous with the external  tunic of  areolar tissue, which  invests
each of the large arterial and venous trunks that connect themselves
with the heart.  This bag serves to fix the position  of the  heart,
and to prevent any sudden or extensive displacement, which  might
interfere with its proper  action.   It consists almost  exclusively of
white fibrous tissue.
  AVithin this fibrous bag is  a serous membrane, the serous pericar-
dium, which resembles in all points of arrangement and  structure
the other membranes of its  class.  One portion  of it invests the
internal surface of the fibrous pericardium, while the other  covers
the heart, the line of reflection passing over the great vessels at the
base of the heart.
  The cavities of the heart are lined by  the  endocardium, a mem-
brane continuous with and closely similar to the lining membrane of
arteries and veins.   It consists of a  layer of epithelium placed on a 
STRUCTURE OF THE VALVES OF THE HEART.       667
stratum of fine fibres which exhibit minute  wavings.   The  epithe-
lium appears to be extremely delicate, but the same in all its cha-
racters  as that  of the  bloodvessels.  It is so delicate, that to be
seen satisfactorily it must be examined in animals just killed.  We
Fig. 196.                           Fig. 197.
,bJ'(7>,

^is'

      Epithelium from the left auricle of the horse           Epithelium from the left
    (magnified 200 diams.), showing the two forms          ventricle  of the  horse.
    of particles, the round and the pointed.               —Magnified 200 diams.

 observe  two forms of  epithelial  particles,  one soft, rounded, and
 globular, the other somewhat compressed, and drawn out at opposite
 poles into  pointed or fibre-like processes (Fig. 196).  It is  difficult
 to determine the precise relative position of  these two forms of epi-
 thelium, but it seems probable that the pointed processes are the more
 deeply seated, and are in immediate contact with the subjacent fibrous
 layer, which here  corresponds to the  basement-membrane beneath
 the epithelium of serous and mucous membranes.
   The endocardium of the left auricle, and of the septum and auri-
 cular appendage of the right auricle, is thicker and denser than that
 in other parts of the heart.   This is due to an increased development
 of the fibrous layer beneath the epithelium, especially of its yellow
 element.   The  precise  meaning of the greater thickness of endo-
 cardium in these parts of the heart is  far from obvious.
   Of the Structure of the  Valves of the Heart.—The valves of the
 heart are formed by processes of fibrous tissue covered by epithelium.
 Between the auricle and ventricle, as  well as at the mouths of the
 aorta and the pulmonary artery, there are remarkable developments
 of fibrous  tissue.  Interposed between each auricle  and ventricle
 there is a fibrous zone, or ring, to which the muscular fibres of the
 auricle adhere on the  one hand,
 and  those  of the ventricle   on                FlS- 198-
the other.   The fibrous tissue is    .___^---^is^-^^^^^^r^^^s^.
prolonged  inwards towards  the          °  ,  ^ ^^^^-^-^h
cavity of each ventricle, so as to
form three CUrtainS On the right    A portion of the aortic semilunar valve in the
 . ,   ,, .     • ,    i  \    j ,         dog.  a. Surface of the valve.  6. Nuclei  of the
Side (triCUSpid Valve), and tWO On   epithelium seen on its margin.
the left (the mitral valve).  These
curtains are continuous Avith the chordae tendinae, which appear to be
inserted into them at their  margins, and at  various distances from
them  on the surface  next to the ventricle, but not at all on that
which corresponds to the auricle.   They are covered on both surfaces 
668              THE CIRCULATION OF THE BLOOD.
 Diagram of the semilunar valves of the aorta (after Mor-
gagni).  a. Corpus Arantii on the free border,  b. Attached
border,  c. Orifices of the coronary arteries.
by epithelium, which likewise extends over each of the chordae ten-
dineae.   The fibrous  tissue at the  orifice of the pulmonary artery,
                                         as well as at that  of the
                FiS- 199-                  aorta, consists of fibrous
                                         cords  arranged as  three
                                         festoons continuous  with
                                         one another, the convexity
                                         of  each  being  directed
                                         towards the muscular tis-
                                         sue  of the infundibulum
                                         of the ventricle,  and its
                                         concavity  to  the artery.
                                         On  the right  side,  the
                                         muscular fibres of the in-
                                         fundibulum  adhere  to  a
small portion  of the  centre of the convexity of each of these fes-
toons, and  the circular fibrous  coat  of the  artery seems closely
attached to the whole extent of the concavity.   On the left side, the
fibrous festoons are connected partly with the muscular fibres of the
ventricle, and partly with the base of the inner curtain of the mitral
valve.  The process  of fibrous tissue  extends  from each  festoon
towards the mouth of the artery, forming a loose semilunar curtain,
which is  the basis of  the valve.   Each of these  curtains presents  a
convex attached border, and  a concave  free border, interrupted at
its middle, or  bisected so as to form  two  concave borders, by a slight
thickening of the fibrous tissue, which forms a small spherical body
called the corpus Arantii; it also  has  a  convex surface directed
                                  towards the ventricle, and a con-
                200.               cave surface directed towards the
                                  artery.   The  bundles  of  fibres
                                  which constitute this fibrous basis
                                  of each valve are  disposed in fes-
                                  toons, some parallel to the fibrous
                                  festoon of the attached border;
                                  others, and the greatest number,
                                  parallel  to  the smaller  concave
borders on  each side of the corpus Arantii.   The fibres nearest the
attached border of the valve are considerably more  developed than
those near its free margin.   Indeed, for a  space of  about three or
four lines from the edge of the valve, the fibrous tissue  is extremely
thin, and almost transparent.   It is at this part of their ventricular
surface that the valves come in contact when they close the arterial
orifices,  forming a mutual  support  to each other, and leaving the
main stress of the backward pressure of the column of blood in the
artery, to be  borne by that portion of each valve which intervenes
between this and its  attached border.   Hence the greater thickness
of the fibrous basis in this situation.   It is  worthy of notice, that
the tissue of  the endocardium is nearly, if  not completely, identical
with the inner longitudinal fibrous  tunic of arteries ; a fact  which
 Fibrous tissue of a semilunar valve beneath the
endocardium. 
MUSCLE OF THE HEART.                 669
 explains the close similarity between the diseased states of the arte-
 rial tissue, and those of the endocardium and the heart's valves.
   Mechanism of the Valves.—The valves are closed  by the mere
 hydraulic pressure of the  blood.   When the blood  accumulates in
 the ventricles, it pushes up the auriculo-ventricular  valves towards
 the auricle until  their  several portions  come in  contact  with each
 other, and close the orifice.  But the simple contact of the curtains
 of these valves with  each  other, would  not prevent regurgitation ;
 for the same hydraulic  pressure which brings them in contact would
 push them into the auricle, were it not  that their margins are con-
 nected with the walls of the ventricle and the musculi papillares, by
 means  of the chordae tendineae.   When the ventricle  contracts, it
 draws firmly by means  of the chordae tendineae upon the valves, and
 not only keeps them closed, but causes them to exercise a considera-
 ble pressure on the blood, which promotes  its onward flow into  the
 artery.
   Thus,  by the attachment of the chordae tendineae to the  several
 curtains of the valves,  not only  is regurgitation of the blood  op-
 posed, but every part of the  surface of each  curtain  is made to
 press upon the blood, with a force equal to that  of the contraction
 of the ventricle,  and to aid in propelling it  through the  artery.
 Should,  however, any imperfection of the valve exist, as by  the  im-
 perfect apposition of its several portions, a chink remains between
 their margins, and regurgitation takes place to a degree proportionate
 to the size of the chink.
   The semilunar  or arterial valves are  closed in their turn by the
 pressure of the blood from the artery, backwards, towards the heart.
 The blood forcibly driven back by the elastic reaction of the arterial
 walls, slips between the wall of the  artery and  the  valves,  at  the
 sinuses of Valsalva, and throws the latter inAvards, causing them to
 meet and close the arterial  aperture,  thereby preventing regurgita-
 tion into the ventricle.   Thus  the force by which the arterial valves
 are closed, being  the  elastic reaction of the arterial walls; excited
 by the expulsive force of the ventricle, bears a constant ratio to the
 contractile power  of the wall of the heart, and, therefore, the  degree
 of tension of the  semilunar valves, and the sound which it develops
 (the second sound of the heart), enables us to form an  estimate of
 the expulsive force of the ventricle, which  is often of  great value
 in practice.
   Of the Muscular Tissue  of the Heart.—The heart  is composed
 of muscular fibres of very various sizes.  In all  essential  points of
 structure, these fibres  resemble very closely the  striped  fibres  of
the external muscles, differing  from  them,  however, in  the extreme
tenuity of the  sarcolemma.  They interlace  with each  other  in  an
intricate manner,  and  assume opposite directions on different planes,
thus forming a  complicated  interlacement  of  fibres,  Avhich adds
greatly to the power of resistance possessed by  the organ.  By this
interlacement the  fibres  of the heart  adhere to each  other, for  be-
tween them there  is little or none of that areolar  tissue  Avhich exists
in considerable quantity in the  external muscles, and  unites their 
670
THE CIRCULATION OF THE BLOOD.
fibres and fascicles together.  This  interlacement takes place irre-
spective of any subdivision  of the fibres.  Nevertheless, it has  re-
cently been noticed by Kolliker and  other good observers, that a true
anastomosis does take place between  adjacent fibres by the branching
of each fibre, and the fusion of neighbouring branches.  A somewhat
similar  branching and anastomosis  of the  ultimate  muscular fibre
has been observed at the  surface of  the tongue, an  organ of which
the muscular structure is  not unlike  that of the heart.
   The complicated disposition of the fibres of the heart on different
planes has, no doubt, the object of strengthening the walls of its
cavities, and  insuring a uniformity and synchronousness in the con-
traction of all its fibres.   This arrangement  belongs  particularly to
the ventricles, where such a mode of action is most needed.   It may
be best demonstrated  on hearts which have been subjected  to long
boiling.   By this process  the fibre is hardened, and may be  readily
torn in the  direction of its  course, and  thus,  by a little  careful
manipulation, the  connection of the fibres and bundles of fibres may
be unravelled.
   The ventricles  are covered  by a  thin layer of fibres common to
both.  These may be traced, apparently emerging  from the  apex,
and spreading out over the anterior  as well as the posterior  surface
of the heart.   At the apex, these fibres pass in to form a connection
with the fibres which form the innermost layer of the wall of each
ventricle ; from the same  point these superficial fibres pass obliquely,
those of the  posterior surface from right to left;  those of the ante-
rior surface rather in the  direction from left to right.   At the trans-
verse fissure, they sink in to attach  themselves to the fibrous  zone,
which separates auricles from ventricles.  According to some anato-
mists (Reid and others), many of the superficial fibres  do not pass
beyond  the anterior  longitudinal fissure, but sink into and  become
incorporated  with those of the septum.
   If the fibres of the apex be traced inwards, they are found to
penetrate so as to form  the innermost  layers  of the walls of the
ventricle, contributing likewise to form the  carneae columnae, and
becoming attached to the  fibrous  structures of the ventricle,  both to
the chordae tendineae, and the auriculo-ventricular zone.  Some of
these fibres serve to connect opposite walls of the heart: thus, the
deep layer of fibres of the posterior  wall of the heart receives fibres
from the superficial layer  of the anterior  wall, and reciprocally the
superficial layer of the posterior wall contributes to  the deep layer
of the anterior.  But others of the  superficial fibres  are continuous
with the deep fibres of the same  wall.  These are the fibres  which,
in passing from the superficial to the deep portion of the wall, make
a remarkable turn in figure  of 8, of which the lower  portion is very
small, as described and figured long ago by Lower.
   Between the superficial and the deep or reflected  portion  of  the
ventricular fibres, are some which have been described as the proper
fibres of the  ventricles ; these pass  round each ventricle in a circu-
lar direction, some obliquely, some at right  angles to its axis ; they
form a sort of hollow cylinder for each ventricle, which is attached 
NERVES OF THE HEART.
671
 above to the fibrous zone of the auricles, and is open below towards
 the apex.   On  the  right  side, a smaller  number  of circular  fibres
 embrace the infundibular  portion of the ventricle, attaching them-
 selves to the fibrous festoons of  the pulmonary artery.
   Of the  Muscular Fibres of the Auricles.—In  the auricles, Ave
 find  a common and a  proper set  of fibres.   The  former  may be
 traced along the anterior  surface of both  auricles, embracing them
 like a belt, but  not extending  round to the posterior surface.   The
 latter are  arranged in several circular or spiral bands, some of which
 spring from the auriculo-ventricular zone, and return to it again,
 and envelop the  auricle before  and behind, passing sometimes  at
 right angles to  it, sometimes obliquely;  others pass round the auricle
 in a  horizontal  direction, and parallel to the auriculo-ventricular
 zone.^  Each of the venous orifices of the auricles is surrounded by
 a series of circular fibres (sphincter-like) which are continued, as
 already referred to, to a considerable distance  along the trunks of
 the veins,  retaining in this latter situation just the same character
 as at the auricle itself.   This is a good  situation  for  seeing  the
 branching and anastomosis of the fibres.
   Nutrition of the Heart.—The heart is nourished by blood derived
 from the aorta.  Its arteries, the  right and left coronary arteries,
 are the first branches which spring from the aorta.  They leave that
 vessel just beyond the margins of the semilunar valves.  The right
 passes along the circular groove between the auricles and ventricles,
 and sends  a branch  down  the posterior median groove to the apex ;
 the left passes along the  anterior median groove, anastomosing  at
 the apex with the latter branches.   Corresponding with the  small
 size and the oblique direction of the heart's fibres, are  an extreme
 closeness and an eA'erywhere oblique sloping of the capillary network.
 From this, venous radicles are formed  at  various points, and  unite
 into large  veins, which are found in the grooves of the heart accom-
 panying the arteries ;  these veins  terminate  in the coronary vein,
 which is lodged in  the  right portion  of  the  circular groove, and
 opens into  the right auricle, close to the orifice  of  the inferior vena
 cava.
  Nerves.—The nerves of the heart are derived from the  cardiac
 branches of the pneumogastric  nerve, and from the sympathetic.
 These nerves form by their frequent anastomosis a plexus called the
 cardiac plexus.   It is situated upon the aorta and pulmonary artery,
just as they have issued  from their respective ventricles, and is com-
 monly described as consisting of two  portions—the superficial cardiac
plexus, AA'hich corresponds  to the concavity of the arch of the aorta,
 and lies in front of the right  branch of the pulmonary artery; and
 the deep cardiac plexus,  Avhich is much the larger portion, and lies
 behind the arch of the aorta, between it and the bifurcation of the
 trachea.   To the formation of these plexuses, branches derived from
 the vagus  and the sympathetic on both sides contribute.
  The greatest part of the nerves which emanate from these plexuses
 entwine round and accompany the  right and left coronary arteries,
 forming the anterior and posterior coronary plexuses.  From these, 
672
THE CIRCULATION OF THE BLOOD.
nerves pass to the auricles  and ventricles, but chiefly to the latter.
A ganglion, described first by Wrisberg, and  called after him  gan-
glion cardiacum Wrisbergii, is generally found in front of the left
auricle, and behind the aorta.  Scarpa has also described gangliform
enlargements  of the nerves on the anterior surface of the ventricles,
to one of which, situated on the anterior surface of the horse's heart,
half-way doAvn  the  anterior groove, he  refers under the name of
" cardiaci  sinistri  ganglion  insigne."*   It  is  probable,  however,
that none of these latter enlargements are truly ganglionic in  their
nature.
   Remak describes numerous  microscopic ganglia on the nerves of
the heart of the calf.  We have  seen some of these small ganglia
upon the surface of the auricles in the calf's heart, although we have
not succeeded in detecting them on the surface of the ventricles, nor
in the substance of the septum, as delineated by Remak.   We can
vouch for the  truly ganglionic nature of  those which we have seen
from the unequivocal existence of  vesicular matter in them.f
   Some elaborate dissections of the nerves of the heart have lately
been made by Dr. Robert Lee, J from which it appears that  the heart
is more largely  supplied with  nerves  than had  been hitherto sup-
posed, and that  a larger number go directly to the muscular  struc-
ture of the heart, independently of the arteries, than had  been
admitted by previous anatomists.  Upon these nerves numerous
gangliform enlargements may  be seen, which Dr. Lee figures as of
great size upon  the nerves  of  the  posterior surface of the heifer's
heart.
   Our own dissections§ enable us  to  confirm the general  accuracy
of Dr. Lee's delineations, although we have not  discovered so many
nor such large nerves  as he depicts.   We have likewise  seen nume-
rous swellings on these nerves, Avhich again we have failed to  find,
either in such numbers, or of the same size as those  represented in
Dr.  Lee's plates.
   The nerves  are composed altogether of gelatinous fibres, and the
swellings do not contain vesicular matter ;  and, therefore, do not
partake  of the  nature of  ganglia.   As  filaments  invariably pass
from theseK swellings  into the muscular  structure of the  heart, Ave
Avould regard them as  resulting from that loosening of the consti-
tuent fibres of nerve trunks, which invariably takes place just before
branches are given oft' from them.
   Of the Action of the Heart.—The  action of the heart is remark-
able for its rhythmical character.  Each of its cavities exhibits  a
succession of contractions and dilatations, following each other with
the most perfect rhythm.   Cavities  of the same kind  contract or
dilate simultaneously;  but the  ventricles are in contraction or systole
Avhen the auricles are  in dilatation or  diastole, and vice versa.  Fol-

  * Scarpa, Tabular Anatomicge.  Ticin. 1794.   Tab. vii. fig. 1.
  •j- Remak, Ncurologischen Erlauterungen. Muller's Archiv. 1844.  Tafel xii.
  % Phil. Trans. 1849.
  | We take this opportunity of acknowledging the valuable assistance of our friend
and pupil Mr. Samuel Martyn in these dissections. 
MOTIONS AND SOUNDS OF THE HEART.
673
lowing the course of  the circulation through the heart, the auricles
having been filled from the veins which open into them, contract and
expel their  blood into the ventricles, which, in their turn, contract
to drive the blood into the arteries.  When the ventricles  contract,
the heart experiences a peculiar tilting movement, by which its apex
is raised from the level of the sixth rib to the space between the fifth
and sixth, and at the same time  it is rubbed more or  less forcibly
against the wall  of the chest.  The wall of the ventricles is firmly
contracted at every point, and rendered hard and tense ; and, there-
fore, in its movement it communicates a considerable vibration to the
Avail of the chest, giving  rise to  what is called the impulse.   This
impulse is caused altogether by the  systole of the ventricles, and
the consequent movement  of the  heart;  it is always  directly pro-
portionate to the size  of  the ventricles,  or to  the extent of  their
surface in contact with  the wall of the thorax, and to the  vigour of
their contractions.  According to Valentin's experiments, the tilting
movement of the heart  will take place even when the apex has been
cut off, denoting  that that phenomenon cannot be due to any recoil
consequent  upon  the  resistance to the passage of the blood through
the great vessels, and that its true cause is the  contraction of the
fibres of the ventricle.
   Certain sounds accompany the heart's action, the accurate inter-
pretation  of which has  shed a  flood of light  upon the diagnosis of
diseases of  that organ.   On placing the ear over the region of the
heart in a healthy individual, the  following phenomena may be per-
ceived; first, a heavy, somewhat prolonged sound, which is synchron-
ous with the impulse, and is  best heard over the heart's apex ; this
is the systolic or first sound; secondly, a short clicking sound imme-
diately succeeding this ; it is synchronous with (but not caused by)
the diastole of  the ventricles, and is called the diastolic, or second
sound ;  it is best  heard over the base of the heart near the root of
the aorta.   After this the  heart seems  to  pause, as it were to  take
rest, and then follows the first  sound again,  followed  instantly by
the second sound, and then the  pause.   The  duration of the first
sound is about double that of the  second, while that of the second
is equal  to  the pause.   Thus, if  the whole  period  of the heart's
action be  divided into four parts, the first tAvo would be occupied by
the first sound, the third by the second sound, and the fourth by the
pause.
  Numerous experiments  and observations have  been made  with
reference  to the question of  the 'signification of these sounds.   We
must here content ourselves  with  stating the  conclusions which we
think may be safely drawn from them.  The first sound is  composed
mainly of the muscular sound, generated by the contraction of the
ventricles, strengthened by that  due to the sudden tension of the
auriculo-ventricular valves over the blood contained in the ventricles,
this tension  being effected by the contraction of the  carneae  columns,
Avhich is synchronous with that of the rest of the  ventricular  wall.
To these causes of sound may be  added  the impulse of the  heart 
674
THE CIRCULATION OF THE BLOOD.
 against the wall of the chest, and, perhaps, also the collision of the
 blood against the orifices of the great vessels.
    The second sound  is due to the sudden tension of the semilunar
 valves of the two great vessels, by the recoil of the columns of blood
 injected into them by their respective ventricles.   An experiment,
 originally suggested by the late Dr. Hope, and repeated by several
 observers, proves this unequivocally.   If in an animal Avhose respi-
 ration is maintained by artificial insufflation, the heart's action being
 thereby prolonged, a hook be introduced into the aorta so as to hold
 back one of its valves, and leave a passage for the regurgitation of
 a portion of the blood after each systole of the ventricle, a  bellows
 sound  becomes  generated, which  usurps the  place of the clicking
 second sound.  But the moment the  valve is allowed to  resume  its
 play,  the natural click returns.
   That this is the  correct interpretation of the sounds of the heart,
 is farther proved by the observation of the influence of various mor-
 bid states of that organ upon them.  Thus the  first sound is modified
 by whatever increases or weakens the intensity of the ventricular
 systole, of the impulse, and of the tension of the auriculo-ventricular
 valves ; and when  the latter takes place imperfectly, by reason of
 the insufficiency of  the valves to close the orifices, the first sound is
 accompanied (not replaced) by a bellows-sound  due to the regurgita-
 tion of blood from ventricle to  auricle.   Again, should one or more
 of the semilunar valves be so injured or altered  as to prevent the
 complete closure of the arterial orifice, at the time of the diastole,
 the second sound  is  replaced  by a  belloAvs-sound, just  as  in  the
 experiment above detailed.
   The regular succession of the two sounds and the pause, bearing
 to each other the  relative  duration already mentioned, constitutes
 the  rhythm of the  heart.*   Sometimes the pause lasts  for a much
 longer period than  a fourth of the  whole,  for as long or longer than
 would suffice for the development of the  other two sounds.   Under
 these circumstances the heart is said to intermit,  and its  rhythm is
 interrupted.
   At every systole of the heart an impulse is felt in all the large
 arteries of the body, which is synchronous with the contraction  of
 the ventricles, or so nearly  that the difference  is inappreciable, ex-
 cept in very distant arteries, as those  of the  tarsus.  This  impulse
 in the  arteries constitutes  the pulse—which will be fully described
 by and by, and which, from its general accordance with the heart's
 action,  affords the readiest means of judging of the heart's rhythm,
 and  counting the frequency of its action.
   When the rhythm of the heart is regular, this succession of first
 and  second sound (systole and diastole) and pause  may be heard a
 certain number of times in a minute in each individual, and by a series
 of observations, the scale may be formed  showing the average fre-
 quency of the heart's action at different periods of life in man.  This is
shown in the following table, which is that formed  by our able friend
Some observers admit the existence of a short pause after the first sound. 
ACTION OF THE HEART.                  675
and colleague, Dr. Guy, from a comparison  of numerous  observa-
tions.*
TABLE OF THE AA'ERAGE FREQUENCY  OF THE HEART'S ACTION, AND OF THE PULSE
                       AT DIFFERENT AGES.
      At birth..........140
Infancy
Childhood
Youth
Adult age
Old age
Decrepitude
1'20
100
 HO
 75
 70
 7o-£
  In general, the frequency of  the heart's action  and of the  pulse
in the  female exceeds that  of the male, after  the  seventh year ; if
the average pulse of the adult male be stated at 70, that of the adult
female may be put doAvn at 80.
  The heart's action is seldom less frequent than 45 or 50 in health;
Heberden has counted  it as low as 42, 30, and even 26, in healthy
males ; and Fordyce counted it in one  case 26 in  an old man, and
in another 20.  In cases of chronic disease of  the brain it falls very
low.  We have ourselves counted it  as  low as 16  in  one of  these
cases for months together.
  According to the researches of Drs. Knox and Guy, the frequency
of the heart's action (and  the  consequent frequency of the pulse)
varies  at different periods of the day.   It  is most  frequent in the
morning, and becomes gradually slower  as the day advances.   The
diminution is most marked at night.f
  Posture exercises a remarkable influence on  the  frequency of the
heart's action.  The law is, that the frequency is the greatest in the
erect position, next to that in the sitting, and least in the  horizontal
posture.   The following table has been framed by Dr. Guy from the
results of sixty-six observations  in the male, and twenty-seven in the
female.

   TABLE OF THE FREQUENCY OF THE HEART'S ACTION IN DIFFERENT POSTURES.
                                                   Differences.
                                                   10, 5, 15
                                                   7, 4, 11

  These observations denote the curious fact that posture influences
the frequency of the pulse less  in the female than  in the male; and
from another series of more numerous observations, Dr. Guy deduces
that the effect of  change of posture on the frequency of the heart's
action in the male is more than twice as great as in the female.
  The cause of this  difference in the frequency of the pulse in dif-
ferent  postures resides  probably in the effort employed to maintain
the muscular contractions necessary to  support the erect or sitting
postures.   But careful experiments  are still  Avanting  to ascertain
Avhether  a simple difference of  posture, without muscular exertion,

  *  Art. Pulse, Cycl. Anat. and Phys.
  ■j-  See Graves's Dub. Hosp. Kep. vol. vi., and Dr. Guy's art. Pulse, Cyclo. Anat.
and Phys.
	Standing.	Sitting.	Lying.
Males	81	71	GG
Females	91	84	80
 
676
THE CIRCULATION OF THE BLOOD.
would develop a change in the frequency of the pulse.  Those as yet
done  by the revolving board, seem to have had reference only to the
exertion of muscular force in the production of the change of posture,
and not to that  required for the  continued effort  to  maintain the
attitude.
   The  Course  of the Circulation in the Adult.—Taking  the left
ventricle as the starting-point  for the circulation, we may describe
the blood as pursuing the following course.   By  the  left ventricle
it is driven through the aorta into every  artery of  the body save the
pulmonary ; and having passed through the capillary system it enters
the venous radicles, and from them it passes to the venous trunks ;
it is at length returned by two great trunks, the superior and inferior
venae cavae, to the right  auricle of the heart.   This portion of the
circulation, from  its traversing the whole system, except the  lungs,
and from its occupying by far the largest part of the body, is called
the systemic or greater circulation.  The venous blood, brought  by
the great venous  trunks to the  right auricle, is  expelled by that
cavity into  the  right ventricle, which drives it by the  pulmonary
artery through the lungs to the  pulmonary veins,  through which  it
passes to the left  auricle, and so on to the  left ventricle.  This portion
of the  circulation, traversing  only the  lungs, and  connecting the
right ventricle and left auricle, forms the lesser  or pulmonic circula-
tion.
   Of the Portal Circulation.—In general, the  arterial blood passes
through a single system of capillaries and veins before it is returned
to the auricle.  But there are two remarkable exceptions to this—one
in the portal circulation of  the liver, the other in  the  kidneys.  In
both these cases,  the  blood  passes  through two subsystems of capil-
laries after it leaves the arteries.   Thus,  as regards the hepatic cir-
culation, the blood conveyed to the intestines by the arteries, passes
through the intestinal capillaries into the intestinal veins, whence  it
passes to the trunk of the vena portae, Avhich again transmits it to
the hepatic  capillaries, and thence  to  the hepatic veins, through
which it reaches the heart.   A portion of the  circulation, of  which
the chief vessel is formed like a vein, and distributes its blood like
an artery, is called a portal  circulation.   A  similar  circulation  is
found in the kidneys.  The afferent  arteries  end in the Malpighian
tufts, whence the blood  is taken up by the efferent veins,  which
quickly break up like  arteries into another capillary plexus surround-
ing the uriniferous tubes, and this plexus  gives origin to the radicles
of the renal or emulgent veins.
   The hepatic portal circulation, however, has several points of com-
munication with the systemic veins, or the  inferior vena cava; and
thus it happens, when from disease of the  liver a considerable portion
of the portal system  of  that organ is obstructed or obliterated, that
a part of the blood from the intestinal canal finds its way into tribu-
tary veins of the  cava, and returns by that route to the right side
of the heart.  The points of  communication are between the  veins
of the cava (left renal) and of the  intestines,  especially the  colon
and the duodenum, and betAveen  the inferior mesenteric  and the 
FCETAL CIRCULATION.
677
hemorrhoidal veins, a fact which explains the frequent occurrence of
hemorrhoids in  obstructions of the liver;  also between superficial
branches of the portal veins of the liver, and the phrenic  veins, as
pointed out by Kiernan.
  Bernard states that immediately after the portal vein has entered
the liver, and sometimes  before, a certain  number of branches  are
given off from it, which, entering the liver, some superficially, others
more deeply, form  communications with the vena cava.
   Of the Foetal Circulation.—In  the foetus in utero, the course of
the circulation is greatly modified, by reason of the inaction of the
lungs as aerating organs, and the  consequent imperfect attraction of
the blood to them.   During  intra-uterine  life, the aeration of the
foetal blood is  effected by the placenta, a highly vascular  organ, in
which the foetal blood is brought  into  a very close relation to the
maternal blood as it circulates through the wall of the uterus.  The
placenta, therefore, is in effect the lung of the  foetus,  and bears a
corresponding relation to its circulation.
   A large portion of the foetal  blood  is  carried to  the  placenta
through the umbilical arteries, which are continuations of the trunks
of the internal iliac  arteries escaping from the  body of the foetus
through the umbilicus.  From the placenta the blood is  returned to
the foetus by the umbilical vein, which is bound up with the  umbilical
arteries in the umbilical cord, and enters the body  of  the foetus at
the navel.   From this point the umbilical vein passes upwards  and
to the right  side under the liver, in its longitudinal fissure, and at
its transverse fissure it joins the  sinus of the vena porta, through
which most of its blood is distributed to the liver.    One large branch,
however, follows the course of the original trunk in the  posterior
part of the longitudinal fissure, and opens into  the  inferior vena cava
just before that vessel  communicates with the  heart.   This vessel is
the  ductus venosus—a continuation of the trunk of the  umbilical
vein—through which some of the  blood returning from the placenta,
passes directly to the inferior vena cava, and to  the right  auricle of
the  heart,  without  traversing the  liver.
   The blood thus received from the inferior vena cava  (being that
from the body below  the diaphragm), and  also  from the  placenta,
does not pass into  the  right ventricle.  A very interesting piece  of
mechanism obstructs its  passage  in that direction, and favours its
flow across the right auricle through the foramen ovale, now freely
open in the septum, into the left  auricle.   This is  the Eustachian
valve, which is situated between the inferior vena  cava and the right
auriculo-ventricular opening, and being connected with the anterior
and inferior part of the annulus ovalis, it brings the  foramen  ovale
into very close connection with the inferior vena  cava, and forms an
imperfect  septum  towards the auriculo-ventricular  opening,  quite
sufficient,  however, to impede the flow of blood in the downward
 direction.                                                      ,
   Arrived in the left  auricle, the blood is transmitted thence to the
 left  ventricle, and from this latter  cavity through  the arch of the
 aorta to the head, neck, and upper extremities, whence it is returned 
678
THE CIRCULATION OF THE BLOOD.
by the venae innominatae and by the superior vena  cava to the right
auricle, which transmits it to the right ventricle.   This latter ven-
tricle propels  it into the  trunk of the pulmonary  artery, Avhich, in
the foetus, divides into  three  vessels, not into tAvo, as in the adult.
These are the two pulmonary arteries which separate from the trunk
at right angles, one for each lung; and between them, following the
direction of the parent trunk, a large vessel, nearly as  large  as the
pulmonary artery itself, which forms  a direct anastomosis with the
aorta, just beloAV its arch.  This  is the ductus arteriosus, through
which the blood is transmitted directly from  the  right ventricle to
the commencement of the abdominal  aorta.

   Of the  Forces by which the Blood is circulated.—The principal
force by Avhich the blood is moved throughout the  vascular system,
and returned to the heart, is that which is generated by the contrac-
tion of the left ventricle,  or what is commonly called the  vis a tergo
of the heart.
   The force with which the heart propels the blood into the arterial
system has been  variously estimated.  Valentin considers that the
left ventricle exerts a force equal to one-fiftieth of the weight of the
body; and, taking the muscular power of the right ventricle to be
half that of the left, he would estimate the power of the latter at
one-hundredth part of the weight of  the body.  This would  give a
force of upwards of three pounds for the left ventricle  for  a man
Aveighing eleven stone, and half of that for the right.
  Now Hales  had long ago (1769) shown that, under the pressure of
a column of water nine feet and  a half in height, fluid  might  be
made to pass from the carotid artery to the jugular vein through the
capillary system.  And it is well  known  to  anatomists that, when
the vessels are free from coagulated blood  or other mechanical ob-
struction,  thin fluids may  be transmitted by a very slight  force from
the arteries to the veins.
   Dr. Sharpey's experiments* indicate the  exact  amount  of force
necessary for  this purpose.   A syringe with  a haemadynamometer,
to show the amount of pressure used, Avas  adapted to  the  thoracic
aorta of a dog just killed, the abdominal aorta having been previously
tied immediately above the renal arteries, and the inferior vena cava
opened just as it passes through the diaphragm.  Fresh defibrinated
bullock's blood was  injected with  a  pressure of  three and  a half
inches of mercury, and passed  through the  double  capillary system
of the intestines  and the  liver  out of the  veins with a full stream.
When the pressure was increased to  five inches, the blood spirted
from the vein  in a full jet.  When the aorta was not tied above the
renal arteries, the same pressure sufficed to drive the blood through
the vessels of the lower  extremities, and  it was  made to traverse
the capillary system of the lungs, by a pressure of from  one and  a
half to  two inches of mercury, so as to flow freely through the pul-
monary veins.  Allowing  one pound for every two inches of mercury,

          * See Williams's Elements of Medicine, 3d Am. Ed. p. 154. 
THE CIRCULATION IN THE ARTERIES.
679
it would thus appear that a pressure of two pounds was sufficient to
complete the circulation through the two abdominal capillary systems
—and of  one pound for the pulmonary circulation.
  Unless, then, we assume that there are  obstacles to the flow of
blood  through the vascular system,  which, during life, are much
greater than those after death, it must be  granted  that the  heart's
force, which in man does not probably exceed three  pounds,  is suffi-
cient to drive the blood throughout the three systems of bloodvessels,
and  to maintain the current of  the circulation ;  and that this  force
alone is capable of producing all the grand phenomena of the circu-
lation.
  It remains, then, to  inquire whether the  vis a tergo of the  heart
is the sole force by Avhich the  circulation is maintained,  or whether
we must not seek  for the operation of other forces in order to ex-
plain its phenomena.   To determine these points Ave must investigate
the phenomena of the circulation in each of the systems  of blood-
vessels, and first in the arteries.
  Phenomena of the Circulation in the Arteries.—By each contrac-
tion  of the left ventricle  a certain quantity of blood is pumped into
the arterial system, which is already full.   Were the arteries and
other bloodvessels a series of rigid and inelastic  tubes, there wfauld
necessarily ensue  upon this a  discharge  of blood, corresponding in
quantity and rapidity, from the opposite extremity of the system.
It is plain,  however, from the  slow  rate of the  venous  circulation,
and  the less capacity of the auricles as compared with the ventricles,
that this does not  take place in the vascular system; nor, considering
the great  extent of surface Avhich the blood has to travel over in the
capillaries, and the consequent friction it has to encounter, can it be
expected  that  a  quantity of blood  should be  discharged  into the
capillaries equal to that which the heart injects into the arteries.
  Room is obtained for each fresh quantity of  blood (beyond that
which can be simultaneously expelled from the opposite extremity of
the  vascular system), by the  dilatation of the  arteries under the
force of the heart.  The eminently extensible and  elastic  character
of the arterial walls thus gives a peculiar feature to the  arterial cir-
culation, and is turned to good account  in  maintaining the  flow in
that  system of bloodvessels.   In yielding under the force of the
heart the arteries become dilated at each systole, to the extent, ac-
cording to the experiment of Poiseuille upon the carotid of a horse,
of one twenty-third of its diameter, or of one twenty-second, in a
similar trial by Valentin  on the carotid of a dog;  but which must
vary in different arteries  and at different times with the  force of the
heart, and  the  extensibility  of the arterial wall.   Poiseuille's ob-
servation, however, pointed out unequivocally the fact (previously
doubted),  that the arteries are dilated  at each systole of the  heart.*
  This dilatation  of the arteries calls into play a force which in some
degree replaces the heart's force.  The elastic arterial wall, stretched

  *  See the account  of Poiseuille's experiment, and a figure  of his instrument in
Magendie's Journal, torn, ix., and also in Valentin's Physiologie, Bd. 1. p. 44J. 
680             THE  CIRCULATION OF THE BLOOD.
by the contraction of the heart, reacts with a power  which approxi-
mates more closely to that by which it was dilated according as the
arterial tissue  is more or less elastic.  The  arteries are thus made
to contract upon their  contained blood, and to drive  it onwards or
from the heart, and backwards  or to  the heart.   Its course, in the
latter direction, is speedily  checked  by  the  sudden  and  forcible
closure of the  aortic valves under the pressure of the regurgitating
current.   Therefore,  the great mass of the blood rushes onwards
towards the capillary system—propelled first by the heart's impulse,
and,  secondly,  by the elastic reaction of the arterial walls.
   This elastic  reaction of the parietes of the arteries does not come
into play until the heart has ceased to contract and begun to dilate.
It is, therefore, synchronous with the diastole of  the heart, and cor-
responds with it in duration;  so that, while the ventricle is inactive,
the blood in the arteries is  still being pressed upon by the reacting
arterial walls.   Thus the blood is ever moving onwards throughout
the arterial system, during the diastole, as Avell  as during the systole
of  the heart;  and the jerking impulses  communicated to it by the
successive contractions of the ventricle, are gradually converted into
that continuous uniform forward movement, which is observed under
ordinary circumstances in  the   ultimate  arterial ramifications, the
capillaries, and the veins.
   An analogous application of the reacting force of an elastic agent
to convert a jerking  movement  into a continuous  stream is found in
the mechanism  of the  fire-engine, and  of the  organ.  In the one,
Avater, in the other, air, is forced into a chamber in which air already
exists.  This air undergoes compression  by the sudden introduction
of  a new quantity of water or air. '  Its elasticity causes  it to react,
and thus to supply an  expulsive force during the  subsidence of the
action of the piston in the one case, and of the bellows in the  other.*
   The heart, by its propulsion of blood into the arterial system, not
only dilates the arteries, but elongates them likewise.   This is gene-
rally better seen than their dilatation, but it is most apparent in
arteries which are curved.   Under the influence of the heart's systole
the curves are  distinctly  altered, so as to  form segments of larger

  * This explanation of the influence  of the  elastic reaction of the arterial wall in
promoting a continuous stream, and  converting the jerking current of  the blood in
the large arteries into a uniform one in the small  ones, is  very commonly attributed
by modern writers, to AVeber.  English  physiologists ought not to have overlooked
John Hunter's remarks (on the  Blood,  &c. 4to ed. p. 12H), nor Sir C. Bell's observa-
tions in his Animal Mechanics, p. 44.   But the following passage from Hales will
show that that able observer held much the same views long prior to either of those
last named.  * *  * " The blood in the arteries," he says,  "being forcibly propelled
forward, with an accelerated impetus, thereby dilates the canal of the arteries, which
begin again to contract at  the instant the systole ceases ; by which curious artifice of
nature, the blood is carred on in  the finer capillaries, with an almost even tenor of
velocity, in the same manner as the spouting water of some fire-engines is contrived
to flow with a more even velocity, notwithstanding the alternate systoles and diastoles
of the rising and falling embolus, or force; and this, by the means of a large inverted
globe,  wherein the compressed air alternately dilating or contracting, in conformity to
the workings to and fro of the embolus, and thereby impelling the water more equally
than the embolus alone would do, pushes it out in a more nearly equal spout."—Ilwrna-
staticks, p. 22, \ 26. 
THE CIRCULATION IN THE ARTERIES.
681
circles,  a  motion is communicated to the artery, and  a change of
place results; and  straight arteries, Avhich are more or  less confined
by the  superjacent parts, become  slightly curved under  the  same
force.   Thus, in the course of time, the arteries, especially those of
parts to which by reason of a more active nutrition in them there is
a considerable afflux of blood, assume a tortuous form, as may be
seen in  the temporal and radial arteries of old persons, and. in the
spermatic artery of the bull.
   The Pulse.—When the finger is applied to an artery during life,
it  is  felt  to beat  or  pulsate  in correspondence  with  the systolic
actions  of the heart, so  that the number of pulsations  in the artery
corresponds  exactly with the number of beats of the heart, and,
if  an occasional interruption  in the heart's  action takes place, or
what is called  an  intermission, there will be at the  same time a
failure in the beats in the artery.
   This  phenomenon is called  the pulse.  From their  contiguity to
the heart, it is always present in arteries; but it may occur in  veins
under circumstances to be explained hereafter.  It is due to the same
cause which occasions  the blood to Aoav per saltum, or by successive
jets, from a diArided artery.  That cause arises out of the manner in
which blood is pumped into the arterial  system by successive  jerks.
Each jet of blood creates a wave Avhich moves along the whole arte-
rial system.   The same  phenomenon  may be observed, if water be
injected by successive jerks into  a narroAV channel already full or
nearly full, and  open on the surface.  Each fresh jet will create on
the surface of the water in the channel a Avave, which may be followed
to its most distant  extremity.   This  Avave, even in a rigid tube, if
sufficiently forcible, Avould communicate to the wall of the tube a thrill
or vibration indicating the course which the wave takes.   But  in an
elastic tube which yields under the injecting force, the  phenomenon
is  more distinctly perceived as the tube dilates under  the pressure
of the advancing wave.
   It is  important to notice that the phenomenon of the pulse in arte-
ries is due solely to the wave  excited by each successive injection of
blood into the arterial system from the heart.   The Avails  of the ar-
teries have nothing to do with the causation of the pulse, but may
render it more or less distinct according as they are  more or less
yielding.
   The  character or quality of the pulse will depend primarily and
essentially upon the force of the heart—secondly, upon  the integrity
of the mechanism by which that force is directed so as to drive the
blood into the arteries—thirdly, upon the quantity of  blood in the
vascular system—and, fourthly, upon the condition of the arterial
wall,  according  as  it  is  apt to oppose or to yield before the wave
caused by the heart's action.   By reference to these points, we may
explain  the various conditions of the pulse observed  in practice.
Thus a  weak heart, or a  contracted arterial aperture, or a small sup-
ply of blood, will each equally produce  a small pulse;  while  a cer-
tain poAver of heart, and  an  open unimpeded state of  the arterial
aperture,  with  a full  supply  of blood,  are  quite necessary to the 
682
THE CIRCULATION OF THE BLOOD.
formation of a large round  pulse.  But the qualities of softness or
fulness, of hardness or wiryness, of compressibility, of  incompressi-
bility, all which are familiar to the tactus expertus of the practical
man, are determined by the yielding or the resisting condition of the
arterial wall.
   Contractility of Arteries.—Arteries possess a poAver of contraction
in virtue of the large  quantity of elastic material which enters into
the constitution of their wall; but this  is a contraction which may
occur in a dead as well as in a living artery, and which simply serves
to restore to its medium dimensions an artery previously distended
or stretched.  They have, hoAvever, also  a power of active contractil-
ity, which ceases with life, which is  capable of being called into play
not only by distension, but by other appropriate stimuli, and which
can diminish the size of the vessels far beyond what their mere elas-
ticity could effect, and even against the influence of the elastic force.
This contractile poAver is due to the presence of unstriped muscular
fibres in the arterial wall.   The demonstration of these fibres in the
walls of arteries by the microscope leaves no more doubt of the exist-
ence of a muscular contractile force  in them than of its existence in
the oesophagus or the intestine.   Experiment anticipated anatomical
research in pointing out  that arteries  contract  as tubes  do Avhose
walls contain muscle, and  it also indicated the peculiar manner in
which the muscular fibres of arteries act.   Under the influence of a
stimulus even of  so slight a nature as exposure to the air, an artery
may be  observed to  contract very gradually, and to become very
much diminished in size.  Thus, in one of Hunter's experiments, the
posterior tibial artery  of a dog was  laid bare ; it was observed, in a
short time, to be  so much contracted, "as almost to  prevent the
blood  from  passing through it, and when divided the  blood only
oozed out from the orifice."*
   Mechanical stimulation, applied to a living artery,  such as gentle
friction with the point of  a  scalpel  or needle, excites in its Avail a
slow and gradual contraction at the  point  stimulated, so that it
appears  constricted at that point.   We have, by stimulating  an
artery in this  Avay, at  several points at some distance from each
other, produced quite a moniliform appearance of it, causing a series
of constrictions separated  by portions in which the  size  of  the
artery was little altered.   Verschuir was among the first to observe
the effects of mechanical stimulation  upon arteries, and he  has
recorded the results of his observations in his Inaugural Dissertation
De Arteriarum et  Vena rum vi irritabili, published in 1766; and
numerous experiments of a  similar kind Avere performed  in this
country  by our friend, Dr.,  now Sir  Charles  Hastings, which  are
detailed  in his treatise on Inflammation of the Mucous Membrane
of the Lungs, published in 1820.
   The galvanic stimulus is  also capable of producing contractions
in arteries, but it requires to be repeatedly renewed before the effect
is manifest.   The most striking results from the application of this
* Hunter on the Blood, &c. 4to. ed. p. 114. 
THE CONTRACTILITY OF ARTERIES.
683
kind of stimulus, were obtained by the Webers, in their experiments
with the  rotatory  magneto-electric instrument.  The  shocks  were
applied to the small mesenteric arteries of frogs, and a diminution
of their diameter  to one-third was produced, in from four to ten
seconds ; and the contraction increased under the continuance of the
stimulus, until  the caliber of the vessel  became from three  to six
times smaller than at first, so  that only a single roAV of blood-cor-
puscles could pass through it; at length the vessel became completely
closed,  and the circulation through it stopped.
  From the  combined evidence of anatomy and experiments, then,
it can no longer be doubted that arteries possess an inherent  con-
tractility, in virtue of the presence of unstriped muscular fibres in
their tunics.   It  remains to  inquire, in  what manner this  power
influences the  circulation in the  arterial  system.   Does it help to
propel the blood?   This question may be  answered  in the negative.
The manner in which arterial trunks  taper towards their distal
extremities, renders it mechanically impossible  that the contraction
of circular muscular  fibres  around them would drive the blood on-
wards unless some valvular apparatus checked its passage backwards
or tOAvards  the heart.  It is by reason of the existence of such an
apparatus  at the  mouth of the aorta that  the elastic coat of the
arteries by its  reaction propels the blood.  But the muscular  coat
would not  contract simultaneously at  all points as  the elastic  coat
does.  It would, as in the oesophagus and intestines, act in successive
portions—and  the  artery would, as in those tubes, be almost or al-
together obliterated at the point of contraction.   It is easy, however,
to shoAV that no such vermicular action  takes place in the arteries,
nor can it occur in tubes which, like them, are always  and at all
points filled.
  It seems most probable that  the contractile power of the arteries
exercises a regulating influence upon the flow of blood through them.
Its influence in this  respect has long been  recognized by practical
men, under the name of tone  or tonic power.   It  restrains Avithin
due bounds the distension of the arteries, limits the quantity of blood
in each  artery, adapts the  size of the artery to the volume of its
contents, and offers a certain amount of opposition or antagonism to
the force of the heart.
  It is  owing to the  resistance afforded by  this contractile poA\-er
of arteries to the passage of  fluid into them, that the anatomist Avill
fail to  inject a tissue completely, if  he attempt it too soon after
death.   The well  known experiment of John Hunter, on  the  pla-
centa, shows how  long the  contractile  power  will  remain  in  the
arteries of a part  after its  separation  from the system,  or after
death.   In  a woman delivered on Thursday, the navel-string  Avas
separated from the foetus in the  usual way, by tying the cord in
two places, and dividing it between them—thus the blood was re-
tained  in  the  vessels of the  cord and placenta.   On the Friday
morning, a ligature was placed an inch  below the  lowest of those
ligatures,  and that  inch was cut off.  The blood immediately gushed
out, and, on Avatching the cut ends of the vessels, Hunter observed 
684             THE CIRCULATION OF THE BLOOD.
the arteries contracting with the whole of their elastic poAver, Avhich
took place immediately.  The next morning (Saturday), on examin-
ing the mouths of these arteries, they were found quite closed up, so
that in twenty-four hours the muscular coat had contracted to such
a degree as to close up the area of the artery.  On Saturday morning
the experiment of Friday was repeated with  another inch  of  the
cord, with precisely the same results, but after its  repetition on  the
Sunday, it was found on the Monday that the mouths of the arteries
remained open, their muscular coat having by that time lost its con-
tractility.*
   The difference in  the results obtained by Hales, as regards  the
velocity with which certain  fluids passed through the bloodvessels,
is referable to the contractile power of the arteries.   Thus, while
warm water, injected into the  bloodvessel of a dog's boAvels, passed
in fifty-two seconds, the same quantity of common brandy took sixty-
eight  seconds;  cold  water  (fourteen degrees above  freezing) Avas
eighty  seconds longer  in passing  than the same quantity of Avarm
water just before.  A strong decoction of bark took much longer to
pass  through the vessels than the same quantity of Avarm water.
Sixteen pots, of equally Avarm decoction of bark, were successively
poured in, the first of which passed in seventy-two seconds;  the
sixteenth, "as the vessels grew more and  more contracted by  the
styptic quality of the decoction," was 224 seconds  in passing, f
   This contractile power in  the walls of arteries (their tone or pas-
sive contraction) is capable of  modifying considerably the character
of the pulse.   When it is feeble, the artery offers  but slight resist-
ance to the entrance of the  blood, and it therefore yields more com-
pletely under the force of the heart.   Hence, fulness of pulse and
feebleness of muscular  power of tone in the wall of the artery,  are
apt to  go together.    On  the other hand,  an exalted  muscular
power  or tone in the wall of the artery, by contracting the arterial
tube, and resisting the flow of blood,  would  cause a small, hard,
and  even a wiry pulse; or a similar effect  might be produced by
an irritating fluid, as a diseased blood, passing through  the artery.
Again, failure of the  tonic property of the  arterial wall causes a
compressible pulse;  an excited or  well-developed  tonic power,  will
case an incompressible pulse.
   Of the Force  of the Heart.—The blood  encounters  considerable
obstacles to its passage through the vascular system, which  tend to
bring it to a state of rest.   The friction against the inner surface of
the vessels, and the resistance of  the elastic and muscular elements
of their walls to  distension,  must be overcome by  any force capable
 of keeping up a continual renewal of the supply of blood to the several
 organs.  Moreover, a  certain rate of movement must be maintained
in the  blood's current.  The attainment of these objects is clearly

   * Hunter, loc. cit. p. 116.  The muscular fibres of the arteries of a part recently
dead pass into the state of rigor mortis, like that of other muscles, which will last a
 certain time; the proper period for  anatomical injections is either before the  rigor
mortis has come on, or after it has ceased.
   f Hsemastaticks, p. 124, et seq. 
THE FORCE OF THE HEART.
685
provided for, in the main, by the action of the heart, and that living
pump  is doubtless endowed with energies sufficient to drive into
the bloodvessels renewed supplies of blood, with a force and a velo-
city exactly adapted to overcome such natural obstacles as the action
of the vascular system must naturally create.
   To estimate the force of the heart, we must ascertain the pressure
which the blood  exercises on the walls of the bloodvessels during
life, and we must measure the rate at which it  flows through them.
   A fluid flowing  through a tube exerts a  double force, one in the
direction of  the  long axis of the tube, the force of the  stream, of
which the velocity gives a measure,  and another,  which is the pres-
sure of the fluid against the wall of the containing tube or the lateral
pressure.  This latter force is always proportionate to the resistances
which the fluid has to encounter to  its flow.   The longer the tube,
through which  the fluid passes, the rougher its walls, the  narrower
the opening  through Avhich it escapes;  and the more glutinous the
fluid, the greater the lateral pressure.*
   A tube fixed into the walls of the  tube through which the fluid
flows, and at right angles to it, affords a simple means of measuring
the lateral pressure, by the height to which the fluid will rise in it.
By equally simple means we may measure both forces, if the measuring
tube be prolonged into the other tube Avith its orifice opposite to the
stream.   The height  which the column of fluid will attain in a tube
so  arranged, will indicate the  altitude from  which  it  must  have
fallen, to acquire the  velocity and force  with  which it streams
through the main tube.
   Pitot, a  distinguished French engineer, who  lived  about  the
middle of the last century, employed a tube  of this kind for mea-
suring the velocity of the stream in rivers.   The tube was bent  at
a right angle, into  two unequal branches, and the smaller or  hori-
zontal branch was immersed in the  stream with  its mouth opposed
to it.   The height  of the  column sustained in the tube afforded a
measure of the force and  velocity of the stream, that height being
such as the water must have fallen  from, in order to have acquired
the same velocity. •
   Hales adopted a similar method  to measure the pressure of the
blood in the arteries.   He  inserted into  the left  crural artery of a
mare, a brass pipe, whose bore was one-sixth of an inch in diameter;
and to that,  by means  of another brass pipe,  he  fixed a glass tube
of nearly the same diameter, which was nine feet  in length.   When
the blood was allowed to flow  into this tube it rose in it to a height
eight  feet three  inches above the  level of  the left ventricle of the
heart.   After  considerable loss of blood, however, the  poAver  of
maintaining  a column of this height ceased, and the blood rose, after
the successive bleedings to seven, six, five, four, and at length, to two
feet four inches.
   In a second experiment, exactly the same, excepting that it was
made  on a horse of more vigour than the  subject of the previous one,

   * See Volkmann, die Haemodynamik nach Versuchen.   Cap. i. Leipzig, 1850. 
686
THE CIRCULATION OF THE BLOOD.
the blood rose to nine feet eight inches, and fell subsequently, after
successive bleedings, in the same manner as in the first experiment.
A third experiment made upon a mare, consisted in fixing the brass
pipe into the carotid artery toAvards the heart, and to that the Avind-
pipe of a goose, on account of its  pliancy, and to the other end of
that a glass tube, twelve feet  nine  inches long.   The blood  rose in
the tube to nine feet six inches, and behaved, in all respects, much
in the same way as  in  the former  experiments.   And  afterwards,
Hales experimented in the  same way on the sheep, the deer, the dog,
with results essentially similar, but varying Avith the size and general
poAver of the animal.
  Hales estimated the force of the  left ventricle of the heart at the
moment of its systole, by multiplying  the area of  its inner  surface
into the height of the column of blood in the tube which it Avas capa-
ble of sustaining, calculating also  the absolute weight of the quantity
of blood which formed that column. From these data he concluded
that the contraction of the left  ventricle of the  horse's heart was
capable of sustaining  a Aveight of 113  lbs., that of the sheep 36.56
lbs., that of the dog  33.61 lbs., Avhen the animal weighed 52 lbs.,
and 19.8 and 11.1 lbs. in dogs Aveighing respectively twenty-four and
eighteen pounds.
  Poiseuille improved upon the method of Hales's  experiments, and
obviated some  objections  to  them.   He employed  an  instrument
which he called the haemadynamometer. (Fig. 201.)  This consisted
of a glass tube bent so as to form a horizontal (B") and two perpen-
dicular (BB') portions.   The horizontal portion  is  capable of being
adapted by means of  brass tubes of various size to arteries or veins,
hoAvever different in caliber.  The tube is attached to a board (AA'),
on which a scale is marked.  To use it, mercury is  poured into the
perpendicular branches  of the  tube,  and will,  of course, stand  at
the same height  in each Avhen the  instrument  is  kept in the per-
pendicular.
  In order to prevent the coagulation  of the blood, which, by caus-
ing it to adhere to the sides of the tube, Avould complicate the  experi-
ment (a point not provided against in Hales's experiments), a quantity
of a strong solution of carbonate of soda is poured into the horizontal
branch, and will therefore  rest upon the  column of mercury in the
nearest vertical branch.
  The instrument is now adapted by means of  a pipe provided with
a stopcock (F) to the  artery in which the blood is to be  measured.
On opening  the stopcock the blood rushes into the horizontal tube,
mingles Avith the alkaline solution, and pushes doAvn the mercury, in
the vertical tube B', that in the tube B rising to the same  extent  as
the first is depressed.  The rise and fall of the mercury in each ver-
tical branch can be measured on scales placed behind them,  and  as
the rise and fall are equal, the double of either Avill give  the height
of a column of mercury which the  force  of the  stream  of blood is
able to maintain.  By causing the  blood  to press upon a column of
mercury, Poiseuille got rid of the  necessity of having a very long
tube as used by Hales. 
                     THE FORCE OF THE HEART.                 687

  Hales inferred, from his observations on the lower animals, and a
comparison of the measurements of their arteries with those of man,

                               Fig. 201.
 Poisp.uilWs hmmadynamometer as slightly modified by Volkmann : AA' the board to which the bent glass
tube (BB'B") is attached.  CC'C" a tin tube which is fixed through a cork (D) air-tight to the horizontal
branch of the glass tube. E an opening with a stopcock in this tube.  F a conical tube which may be
introduced into an artery or vein.  This is provided with a stopcock which serves to regulate the admis-
sion of the blood into the tube of the hsemadynamometer.  G II G' an arm of wood connected with the
board which serves to support the tin tube, and so protect the horizontal branch of the glass tube.
that the force of the heart in the  human subject is capable of sus-
taining in  a tube fixed in  the carotid artery a column of blood 7^
feet high,  and  calculating the surface of  the left ventricle at 15
square inches, he concludes that, when it first begins to contract, the
ventricle supports a pressure of 51.5 lbs. of blood.   And Poiseuille
assigns 4 lbs. 4 oz.  as  indicating the force Avhich the  left ventricle
exerts at the moment of its contraction in propelling the blood into
the aorta.
   Volkmann combats the grounds upon which Poiseuille's calculation
was formed; and assigns the heart's poAver as equivalent to the force
which sets  the stream of blood in motion, and gives it its proper ve-
locity, and also  to that which enables it to overcome the obstacles it
has to encounter.   This latter power is determined by the pressure
in the artery, which  is found in the mean, in the  carotid artery of
mammals, to be capable of  supporting  a column  of mercury of 200
millimetres, or about 7 inches; or a column of blood of 2700  milli- 
688
THE CIRCULATION OF THE BLOOD.
metres (mercury being 13.5  times heavier than blood); whilst the
former  force, taking  the actual velocity of the blood in the  com-
mencement of the aorta at 400, and in the carotid at 300, would be
represented by a column of blood a little more than 8 millimetres in
height.   Thus it would appear that  the force of the heart may be
expressed by  the following formula:—
                        H = 8.2 + 2700 millim.

or that  it is capable of supporting a column  of blood nearly 9 feet
in height, which is equivalent  to a column of  mercury of about  8
inches.*
   That the heart's force is  extended to the whole arterial  system,
and must therefore  be highly instrumental in  maintaining the circu-
lation through it, is shown by the fact that  a considerable pressure is
exerted in  the various arteries,  which can be measured by the hsema-
dynamometer, or by other instruments. Poiseuille  had affirmed that
the pressure in all the arteries was the same, a column of mercury
of the same height  being supported by the blood's pressure in  all.f
This doctrine, however, is at variance with every obvious hydrody-
namic fact, as also Avith the  results of other observations, of which
those of Volkmann seem the most trustAvorthy.   Volkmann shows
that a fluid flowing through a system of tubes has  to  encounter at
the point of its  entrance  into  it the  sum of the  resistances which
oppose it throughout the entire  area, and these resistances  determine
the amount of pressure needed  for its propulsion.   Applying this to
the arteries, it is plain that in  them the blood has to encounter the
resistances  in the capillaries, in the  small arteries, in  the  middle-
sized arteries, and in the arterial trunks—a fact, Avhich, by assigning
to the resistance in  each  of these  regions the symbols x, y, z,  w, x
representing  that in  the arterial  trunks, and the  other letters that
in each of the remaining segments of  the  system, may be thus ex-
pressed, P (being the  pressure  in the commencement of the arterial
tree) = x + y + z + to, whence it is plain that the amount of pres-
sure cannot be the same in all parts of the arterial system, but dimi-
nishes steadily as the artery  is  more distant from the heart.
   Spengler's  experiments so far disprove the accuracy of Poiseuille's
statement as to shoAV that the pressure of the blood differs consider-
ably in  different arteries; but in the greater number of his observa-
tions the pressure appeared to be greater in the arteries more distant
from the heart, some showing a  difference of 36 millimetres in favour
of the more  distant artery;  but in one of the instances quoted by
Volkmann from  Spengler, there was a difference of 16.6 millimetres
in favour of the carotid artery  as compared with the maxillary.

  * See the remarks on this subject in  the  late Dr. Young's Croonian Lecture on the
Functions of the Heart and Arteries.   Phil. Transl. 1809, and republished  in his
Introduction to Med.  Literature, 1823,  p. 607, et seq.
  f As an example, the pressure in the carotid of a dog, distant 208 millim. from the
heart, and that in the humeral artery  303 millim. distant, support a column of mer-
cury of 179.04 millimetres.  Whence Poiseuille infers that a particle of  blood in the
carotid, distant from  the heart 208 millim., moves with the same force  as a particle
in the numeral artery, which has a distance of 303 millim. 
INFLUENCE OF RESPIRATION.
689
   But Volkmann's very numerous observations, made with more per-
 fect instruments than those used by Spengler, show a marked differ-
 ence of pressure in the near and in the distant arteries. Thus, eight
 observations on the carotid,  and a branch of the femoral artery of a
 large dog, gave  a  mean of 7.2 millimetres (0.27 inch) in favour of
 the  carotid.  And ten observations  on the carotid  and metatarsal
 arteries of  a calf yielded  a mean of 27 millimetres (1.05 inch) in
 favour of the carotid;  and twelve observations on the  same arteries
 of another  calf gave a mean of 19.5 millimetres also  in favour of
 the carotid.  Volkmann has also shown that, in  the same artery, a
 notably greater pressure exists  in the part near  the heart, than in
 that more remote from it,  Avhich is, of course, the more conspicuous,
 as the distance  betAveen the tAvo points measured is greater.
   Influence of  Systole and Diastole.—Hales had observed, in  his
 experiments with a simple glass tube, that a rise and fall took place
 in the column of blood to a variable extent at and after each pulse.
 This observation has been confirmed  by Ludwig,  and also by Volk-
 mann.  The rise corresponds to the  heart's systole, the fall to  the
 diastole.  This  affords, in  the greatest part of the arterial  system,
 the clearest proof of the extension of the heart's influence through-
 out it.  And Poiseuille showed that the pulsations of the heart could
 be counted  by noticing the adA'ance of the blood in pulses along  the
 capillaries,  and, under certain circumstances, even along  the  small
 veins.
   Influence of Respiration.—That respiration exercises an influence
 upon the circulation has been likeAvise noticed by several observers.
 Hales had referred to this; he had noticed hoAV the straining efforts
 of the animals  which Avere made  the subjects of his  experiments,
 were followed by a rise of  the column of blood in the tube, and how
 the same effect  followed deep  sighing.  And  Poiseuille found that
 during expiration the height of  the  column of  mercury Avas much
 increased, but that it fell in inspiration.   In forced  and deep inspi-
 rations the force of the heart becomes so much  diminished  in some
 cases that no pulse, or at most a very feeble  one, can be felt at  the
 wrist: on the other hand, in forcible expirations the  pressure of  the
 blood in the arteries  becomes double  its normal  amount.  This has
 been  farther confirmed by Ludwig and Volkmann.  The fact  is  of
 practical interest, and  affords  good  reasons  why the  practitioner
 should caution those whose arteries are Aveakened  by  a diseased state
 of their tunics, against strong efforts,  or against any action likely to
 disturb the  quiet and freedom of the  breathing.
   The heart's force is materially weakened, as Blake's experiments
 sIioav, by the introduction  into  the circulation of poisonous agents
 of a sedative nature.   And there  is every reason to believe that the
 existence of particular  animal poisons in  the blood, as the typhus
poison, that of scarlet fever, of erysipelas, &c, is capable of depress-
 ing the heart and Aveakening the circulation.
  Thus, then, as far as regards the poAvers  by which the blood is
 moved in the arteries, it may be stated that the circulation is main-
 tained in them by the force of the heart;  replaced and propagated 
690
THE CIRCULATION OF THE BLOOD.
throughout the system by the elastic reaction of the arterial tunics,
and to a certain extent restrained or modified by the muscular con-
traction of the same tunic, which likewise serves  very accurately to
adapt the size of the arteries to the quantity of blood contained in
them.
   On, the  Velocity with which the Blood moves  in  the Arteries.—
The calculations  of  Hales and others on this subject, led to ideas
respecting the velocity of the blood, which appear to be extravagant.
Thus Hales inferred the velocity  of the blood at the commencement
of the  aorta in man, to be at the  rate of 735 feet in a second !  The
data upon Avhich  these calculations were  founded are uncertain and
unsatisfactory, such  as the measurement of  the area of the aorta at
its origin, and the capacity of the ventricle and the quantity of blood
expelled by each systole.
   Volkmann has lately devised an instrument for the direct admea-
surement  of the  rate of the blood's movement  in the arteries.   He
calls it the  haemodromometer.  It consists of  a glass tube, contain-
ing water, 52 inches long, bent into the form of a hair-pin, Avhich is
substituted for a  segment  of the bloodvessel, in which it is required
to measure the  velocity  of the  blood's stream.   The  column of
blood which comes from the heart pushes the column of water before
it,  Avithout any  great mixture  of the  two  fluids taking place,
and in passing through a determined  space it takes  a measurable
time, Avhence  it may be calculated hoAV  far the  blood mo\'es  in  a
second.
   The following description  will explain the instrument and the
mode of using it.  At A  (Fig. 202) is a metal tube, an inch and a
half in length ; the ends  of this (a, a') are  conical,  and fit into two
corresponding conical tubes (k, kr), made like the pipes of an inject-
ing syringe, so that they can be  readily fitted into an artery.  A
stopcock (bf) commands the channel of this  tube, not only at a' but
also, by two cogged  wheels, at a.  The mechanism of this arrange-
ment may be  readily understood, by reference  to the adjoining sec-
tions of this portion  of the instrument  and B and C, and the vieAV of
its other surface  at D (r, r' D).   At h,  h' are tAvo short  tubes, also
of metal,  which are fitted  into the horizontal tube below the stopcock,
and so that their channels (as shown at C) may  communicate with,
and be exactly equal to, that of the horizontal  tube.  The stopcock
(b') commands this communication likeAvise.  These short tubes (h, h')
fit exactly upon the bent glass tube (p,p), and complete the communi-
cation between its channel, and that of the horizontal tube at its ex-
tremities.   When the  stopcock is turned so as to open the channel
of the  horizontal tube throughout, as  at B, all communication with
the glass  tube is  cut off; on the other hand, when the communication
Avith the glass tube is opened, as at C, the channel-of the horizontal
tube is stopped, and fluid  entering at a', would have to pass through
h', and to traverse both limbs of the glass tube (p, p) emerging at a.
For the protection  of the instrument in using it, the glass tube  is'
attached  to a board, to which is fixed a scale marked in metal.
   In order, then, to use the instrument, a large artery is freely ex- 
THE H^MODROMOMETER.
691
posed for not less than  three  inches, and, after due precaution has
been taken to counteract hemorrhage, it is divided by cutting out a
piece; the conical  pipes (k, k') are then  fixed into the open  ends
of the artery, one being  directed towards the heart, the other to-
wards  the capillaries.   They must be fixed far  enough apart to
admit of the introduction  of the  horizontal tube (A) betAveen them,
without altering the usual direction of the arterial stream.  When this
tube  is fitted to the conical pipes, then the bent glass tube,  pre-
viously  filled with water, must be fixed  to it by means of the short
tubes (h, h', C), the stopcock being so turned as to shut off all com-
munication Avith the glass tube.   As soon as the instrument has been
properly fixed in the artery, the blood  is allowed to Aoav into the
glass tube.  It may  be  now seen to traverse the  glass  tube Avith a
velocity very nearly the same as it  has in the artery, and in doing
so it pushes the Avater before it into the peripheral bloodvessels, with 
692
THE CIRCULATION OF THE BLOOD.
(according to Volkmannn) only a very slight admixture between the
two fluids.
  By trials  made with his  hjemodromometer, Volkmann found, in
the case  of seven  dogs,  that the blood floAved  in  their  carotids
with  a velocity  ranging between  205  and  357 millimetres in a
second ;  in  that  of horses,  306  to 234; in the metatarsal  artery
of the horse, 56, and in  the maxillary artery of the  same animal
99;  in the carotid of a calf,  431.    The average  velocity in the
carotids of mammals is stated by Volkmann to be  300* millimetres
in a second.
  It results, likewise, from  these observations, that  the velocity of
the blood in the large arteries,  and also  in the  large  veins, is con-
siderably greater than in the capillaries ; that the velocity in arteries
is not uniform, but is suddenly increased at  each systole of the heart,
and that the blood moves most  quickly in the arteries nearest the
heart.  It appears, also, that the blood's velocity is  materially les-
sened by loss of blood, and that increased rate of pulse,  Avhich always
follows considerable losses of blood, is no indication of  a more rapid
blood-current, but,  on the contrary, often accompanies  a retardation
of it.   The  velocity of the  blood-current is influenced not so much
by  the rate  of action of the  heart, as  by the intensity of its systole,
and the quantity of blood which it expels at each contraction.
   Much was formerly said respecting the disposition of the arterial
tree, being  such that the  combined  areas of the branches of an
artery exceeded  that of the trunk, and that with each  succeeding
series of subdivisions, the blood Aoavs into an increased area.  Haller
(torn.  i.  p.  77) ascribes the  first  observation of  this  kind to an
Englishman named Cole.f  It is repeated by Keill, Hales, and many
others, among  them John Hunter and Sir C. Bell.  The general
effect of such an arrangement  would obviously  be to  diminish the
rate of movement of .the blood as it Aoavs  from trunks to branches.
But the  careful measurements of Mr. Fernaby  and  of Mr.  Paget,
render it necessary to modify the general proposition  to some extent.
   Mr. FernabyJ compared the areas  of trunks and branches in the
only sound  way, namely,  according to the geometrical  law, that the
areas of circles are as the squares of their diameters.  Estimated
thus, he found  that the excess of the combined areas  of the  branches
over  those  of  the  trunks Avas very trifling, and, in some instances,
scarcely appreciable;  and Mr.  Paget, while confirming the general
statement of Mr. Fernaby, discovered a remarkable exception in the
case of the common iliac arteries, whose  combined  areas were dis-
tinctly less  than that  of the aorta above the point of  bifurcation—
and the  combined areas of the external and internal iliacs  were less
than  that of the common; but those  of the branches of the external
iliac exceeded  notably the area of their parent trunk.§
   Volkmann states that, in general, the arterial capacity is increased

  * Tolerably close approximations to the value of these measurements in English
inches, may be obtained by dividing each number by 25.
  -J- De Secretiohe animali. Oxon. 1674.
  % Lond. Med. Gaz. 1839.                     § Lond. Med. Gaz. 1842. 
THE CIRCULATION IN THE CAPILLARIES.          693
in area  by the division into branches.  But he instances a remark-
able exception in  the case of the external and internal  carotids of
the horse, whose combined areas are smaller than that of the trunk.
He remarks, likewise, that the  first divisions of the larger  arterial
trunks (aorta  and pulmonary artery) experienced very little increase
of area; but that, as subdivision goes on, the increase becomes much
more marked.  And it is especially so near the capillaries, Avhere the
combined areas of some small branches nearly double  that of their
parent.  This  is particularly interesting, as denoting the coincidence
of physical conformation Avith the result of direct observation, on the
velocity of the blood, which show that it is near the capillaries that the
most decided diminution takes place in the rate of the blood's motion.

   Of the Circulation in the Capillaries.—The manner in which the
blood flows through the capillaries is easily made the subject of direct
observation by examining  the transparent parts of  certain animals,
as the wings  of bats, the mesenteries of small animals as the mouse,
the  Aveb of  the frog's foot, the  lung of the frog, or of the newt, &c.
   In watching the circulation in the web  of the frog's foot under the
microscope, wTith  a  magnifying power of about 200 diameters, the
following points will attract  observation ; first, it will be seen that
the  stream is continuous, that is, it rushes with a  considerable velo-
city, which is uniform when not affected by any extraneous influence;
the  course and rate  of the stream are indicated  by blood-particles
which are carried along in it,  and which seem to chase  each other
through the various channels  and among the little islands of the solid
particles of the tissue Avhich the blood is destined to nourish.  These
particles most frequently pass in a single row, Avith a variable inter-
val  between them;  sometimes,  however,  they seem to rush in pairs,
 or in threes,  according to the size of the  capillary channels through
 which they Aoav.  Secondly, it will be noticed that the greatest velo-
 city of  the stream  is in its centre, a fact Avhich comports with what
 is observed in rivers and other channels through which water Aoavs,
 while towards the circumference  the  stream becomes much  sloAver,
 so that the layer of fluid which is in immediate contact with the  ca-
 pillary wall is almost or completely still.  The particles are carried
 along in the centre or rapid part of the stream, and but occasionally
 a solitary particle seems attracted toAvards the circumference.  This
 is most frequently a colourless corpuscle, so that  sometimes several
 colourless corpuscles are seen at intervals in contact with the wall of
 the capillary, as if  draAvn to it by some special attractive force, or
 moving much more slowly around the central mass  of red particles.
 The sudden  change from a rapid to a slow movement, or to perfect
 stillness, Avhen one  of these particles is  thus drawn from the centre
 to the circumference of the stream, serves to display, in a very satis-
 factory manner, the peculiar feature of  this portion of the contents
 of the capillary, Avhich, from its apparent stillness and from the pau-
 city of blood-particles in it, has been called the still layer of the liquor
 sanguinis.  The existence of this still layer is doubtless a purely phy-
 sical phenomenon, identical with that which is known to take place 
694
THE CIRCULATION OF THE BLOOD.
when fluids pass through inorganic capillary tubes, in which the cir-
cumferential layer seems to adhere or to be attracted to the wall  of
the tube, and it  Avould clearly favour  the  transmission of nutrient
or other, material dissolved in the liquor sanguinis, through the wall
of the vessel, in obedience to a force of attraction between the blood
and the tissue. This still layer forms but a small portion of the Avhole
capillary stream—perhaps about one-eighth or one-tenth its breadth;
it is greater when the circulation is sloAver;  it is also  broader, and
therefore more visible, when a vessel makes a bend.  The application
of cold to the capillaries increases  the breadth of this  layer, whilst
heat produces an  opposite change.
   The capillary vessels dilate or contract, under  particular circum-
stances.   Their dilatation is  passive, and due either to an increased
pressure of the blood into them, or to their distension under the same
pressure  in  consequence of  diminished tone of their  Avail.  Their
contraction  is  caused either by an inherent  contractile  power  in
them, or by the diminution of their contents in consequence of the
contraction of the capillary arteries, in Avhich latter case diminished
pressure  permits  them to contract, in virtue of the elasticity of their
walls.  This latter would be  the more probable view, in default  of
any proved existence of a muscular structure in the walls of the true
capillaries, but there is  no good reason Avhy the nuclei observed  in
them should not be regarded as belonging to muscular tissue here in
a membranous rather than a fibrous form.
   The rate at  Avhich  the  blood moves in  the capillary circulation
has been made the subject  of direct observation by  various phy-
siologists.   It  is  slower than  in the  smallest veins, and  still more
so than in the smallest  arteries.  Hales had stated the rate of the
circulation in the  capillaries of the muscles  of a  frog to be an inch
in a minute and a half, and  in the pulmonary capillaries five times
that velocity.  Subsequent observers,  Weber, Valentin, and Volk-
mann, give a somewhat greater velocity; Weber and Valentin make
it  about an inch and three quarters in a minute, and Volkmann found
it  about the same in cold-blooded animals, but twice  as much in the
capillaries of the mesentery of a  young dog.  These  estimates are
probably rather below  the real rate of motion of the blood in the
capillaries, if we allow for the degree of pressure and  constraint to
which they must  be subjected in making the observations.
   Of the Forces  which maintain  the  Capillary  Circulation.—The
principal force by which the circulation is supported in the capillary
system, is the vis a tergo of  the heart.  We have already adduced
sufficient evidence to prove that that force is capable of driving the
blood throughout the  whole  circulating system.   The following facts
may be stated in  proof  of this doctrine.
   1.  The pressure of the blood may be measured in  the veins, in
the same way as in the  arteries, and this varies Avith the force of the
heart.  If, then,  the heart's  force extends to the veins it must do so
through the capillaries.
   2.  The capillary and venous circulation  in any segment of  the
body, is greatly influenced by the circulation in the  main artery of 
THE CAPILLARY CIRCULATION.
695
   that segment.  Thus, Magendie found the circulation much retarded
   in the femoral vein by stoppage of that in the corresponding artery;
   and by  the hgemadynamometer it may be shown that the force of the
   blood in the A'.eins diminishes or increases with that in the correspond-
   ing artery under certain circumstances.
      3.  In Fishes, the whole blood ejected from the heart passes, from
   the bulbus aortae, through the branchial capillaries, before  it enters
   the systemic vessel;  thus illustrating how the heart's force may be
   propagated through  a complex  netAvork  of  minute capillaries,  to
,   both arteries and veins, as well as to the system of capillaries which
   intervenes between them.
      4.  In debilitated animals, it is  evident, from the jerking move-
   ment of the blood in the  capillaries, corresponding  Avith the action
   of the  heart, that  the impulse of that  organ is extended to these
   vessels, unbroken by the elastic reaction of the muscular contraction
   of the  arteries.  This may be well seen in Avatching the circulation
   in the frog's web, or in the tale of the tadpole.
      Thus, there can be no doubt that the heart's force is not only fully
   adequate to, but  is  the principal agent in, the maintenance of the
   capillary circulation.  When this force fails,  the circulation in the
   capillaries suffer as much as,  if not more than, that in any other
   portion of the vascular system ; and the  sluggish transmission of the
   blood through  the capillaries, such as we often find when the heart
   is simply weakened, occasions congestions, particularly of dependent
   parts, and then, by the filtration of the  serous portion of the blood
   through the parietes of the vessels, oedema and anasarca.
      But  however readily we may concede that the heart's  action is
   the principal force, it must be confessed there are certain phenome-
   na which do not admit of satisfactory explanation, on the supposition
   that it is the only one employed in the maintenance of the capillary
   circulation; and  it seems more reasonable to assume the influence
   and exercise of  some other force  superadded to this, in  order to
   explain  various phenomena  which take place in, or which are de-
   pendent on, the circulation through the capillaries.
     The  more remarkable  of these  phenomena are  blushing, or, in
   more general terms, the influence of mental emotion upon the capil-
   lary circulation;  the influence of local irritation, whether accidental
   or morbid; and the effects of asphyxia.
     It seems  highly probable that in the ordinary molecular changes
   which take place  in the nutrition of the tissues, a force is generated,
   which, in its normal state, must promote, by an attractive influence,
   the flow of blood through  the capillaries.   The cessation of such a
   force would operate unfavourably to the flow of blood through the
   capillary system, whilst its existence in greater power at one point
   than at  another, would cause a greater afflux of blood in the former
   than in  the latter direction.
     The best  illustration of the  exercise of this force, which, for the
   sake of  breA'ity, may be designated the capillary force,* is found in

     * The name Capillary force, which was given by Dr. Carpenter, must be taken as 
696
THE CIRCULATION OF THE BLOOD.
the circulation of the sap in plants.  It is exercised in two situations
—at the roots and in the leaves—constituting in the one a vis a tergo,
and in the other a vis a fronte.  At the roots, a rapid imbibition of
fluid takes place with such  energy, that it pushes before it the fluid
above ; thus, if the  stem  of a vine, in which the sap is rising, be  cut
across, "a bladder tied  over it, will, after  a short time, be burst by
the fluid  accumulated  beneath it; or if a bent  tube, containing a
column of mercury,  be  affixed to it, the mercury will be raised to  the
height of forty inches  or more.   And that a force of attraction is
exercised at the leaves, may be shown by placing the loAver end of   •
the upper division of the cut vine  in water, Avhen an active absorp-
tion and  circulation of water will take place as  long as the vital
changes in the leaves go on; but  if the vine be taken  into a dark
room, so as to check these  vital changes, the absorption  and circula-
tion will likeAvise cease.  So also the elaborated sap or latex, which,
from its containing the elements for the nutrition  and for the various
secretions of the plant may be  likened to the arterial blood of ani-
mals, circulates through a complex system of  anastomosing vessels
(like the capillaries  of  animals), in the  under surface of the leaA^es
and in  the bark, and  Avill  ascend towards the stem,  even  against
gravity, in a dependent branch.  The circulation of these fluids takes
place with the greatest activity in growing parts,  in which nutrient
and chemical changes are going on most actively.
  Professor Draper, of New York,* has given a definite expression
to the nature of the forces which operate  in  the production of the
circulation of the sap in plants, and in that of the blood in animals.
The laws of endosmose and  exosmose resolve themselves into the
following dogma: " That if tAVO liquids communicate  with one an-
other in a capillary tube, or in a porous or parenchymatous structure,
and have for that tube or structure different chemical affinities, move-
ment will ensue; that liquid, Avhich has the most energetic affinity,
will move with  the greatest velocity, and  may even drive the other
liquid entirely before it."
  In  plants, the rise of the ascending sap from the ground, results
from the attractive force of the spongioles.   These appropriate cer-
tain elements contained in  the  fluid, and  exercise a more energetic
attraction on a new  supply, which pushes the former before it.  Thus
the sap ascends to the  leaves, pushed on by successive new portions
attracted to the spongioles.   At the  leaves, a neAv force of a similar
kind,  but due  to the action of light, draws  it on, and  causes it  to
push before it the newly formed latex or elaborated  sap, the Aoav of
which is promoted  by  its  affinity for the vegetable  tissues which it
permeates.
  In  the systemic   circulation of animals, the arterial blood has a
great affinity for the tissues to Avhich  it is  brought by the capillary
system.  This force of attraction draws on the blood from the arte-

merely denoting that the  force is exerted at the capillaries, whether it be exercised by
their walls or by a mutual action between the blood within and the  tissues outside
them.
  *  On the Forces which produce  the Organization of Plants.   1845. 
THE CAPILLARY CIRCULATION.
697
rial side of that system, with a power Avhich  helps to propel on the
deoxygenized blood into the venous radicles.  In the pulmonary cir-
culation, venous blood is conveyed to the air-cells by the pulmonary
arteries.   This  kind of blood has  a great affinity  for the oxygen
which is being continually brought  to those cells by the movements
of respiration.   It is therefore forcibly attracted to the air-cell^, and,
being charged with oxygen, is pushed on by the succeeding portions
of venous blood, which the same force is constantly attracting.
   It is  by the  influence  of  an attractive force,  such  as Professor
Draper describes, that we can best  explain  the continuance  of  a
complex circulation in many of the lower animals in which no central
organ of impulsion exists, as in some of the  Polypifera, and of the
Articulata.   In the  sponge,  the remarkable currents of  water which
flow through the various  channels  that  penetrate its substance, are
maintained without any special propelling organ whatever.  And the
beautiful cyclosis in  Chara and Valisneria affords a striking instance
of a circulation  without a vis a tergo.
   In the vascular area of the  egg, a circulation exists before a pro-
pelling  organ.   And  in  the acardiac fcetus  a similar circulation
exists, although in general it  has  such a  connection with a second
perfect fcetus that the heart  of the latter may influence the circula-
tion of the  former.   But that a foetus  may grow to a  considerable
size, and have  its various tissues well developed without any con-
nection with the twin foetus,  by means exclusively of a circulation of
its own, of which a heart forms no portion, or upon which it can ex-
ercise but a very remote influence, is shown by the case put on record
by the late Dr.  Houston.*   No doubt the same law which influences
the movement of fluids in vegetable tissues would be in operation in
such cases.
   Now, with reference to the phenomena in the circulation of the blood
in man above referred to, it  may be asked:  Is the assumption  of the
exercise  of a capillary force necessary  for explaining them ?  Can
blushing, and other  local determinations  of blood, be accounted for,
if we admit a vis a tergo as the  sole force of the circulation ?  In
order to  explain the  accumulation  of blood, in the cheeks, for in-
stance, under the influence of mental emotion, the advocates of the
latter doctrine  suppose the  capillaries muscular, and affirm that  a
relaxed state of the  walls of  the capillary arteries, and  perhaps also
of the  capillaries themselves, is  produced by the nervous change
which mental emotion excites.  Such  an  explanation  is perfectly
admissible in this particular  case, and it seems  highly probable that
in the relaxed state of the capillary vessels of the  face, their walls
yield under the pressure of the  heart more than those of neighbouring
vessels, Avhich do not come  so completely  within the range of the
centre of emotion.   And in  many persons,  emotion  causes the blood
to desert  the cheeks, which  in consequence become pale.   In such
cases the change in the nervous centre must excite an opposite, that
is, a contracted  state of the capillaries of the cheeks.
45
* Dublin Medical Journal, vol. viii. 
698
THE CIRCULATION OF THE BLOOD.
  But the accumulations  of blood which are caused by local irrita-
tions, do not admit of satisfactory  explanation  by mere changes in
the capillaries of the affected part.
  For example, a  particle  of  dust  is  thrown into the eye, and  as
long as it is in contact with the conjunctiva, its  capillary vessels  are
turgid Avith blood.   Is this  due to a relaxed state of the capillaries
caused by the presence of an irritating agent ?   The analogy of  the
influence of mechanical stimulation  upon other vessels  would lead us
to infer that  the  irritation  of  a  particle of  dust in contact with  the
conjunctiva would cause the capillary vessels to  contract, and a con-
tracted state of  these  vessels  would oppose rather than favour  the
accumulation of blood  in them.   It seems much more reasonable to
suppose that  the  irritation caused by the  foreign particle, increases
the attractive force which the tissue naturally exercises on the blood;
and this would give us a clue to explain the  two  kinds  of congestion
long recognized by practical men, the  passive and the  active form.
The former is owing simply to  a relaxed flaccid state of the parietes
of the bloodvessels, which permits them to receive a greater quantity
of blood from the heart, and to a minus state of the capillary force, the
other to a plus condition of that force,—in A'irtue of which  the  tissue
attracts a greater quantity  of blood.  To  this latter form of conges-
tion pathologists  give the name of inflammation.  Its phenomena, as
observed under the microscope, are  such as a vis d  tergo alone could
not develop.   For not only are. there  dilatations  of  the vessels of
the inflamed  part, and a great  afflux of blood towards a certain point
or points in it, but the blood-corpuscles seem to rush thither, as if
forcibly attracted  towards  each other, and also to  some common
focus.  And  the rapid and copious process of exudation, and  the
formation of  pus-cells, which are so  apt to  follow an attack  of inflam-
mation, afford farther strong indication of augmented vital  force in
the inflamed  part.*
  So also in  growing tissues, and in organs which enlarge at particu-
lar times, or  under certain circumstances, the increased flow of blood
to the part is a phenomenon in close analogy with the  increased flow
of sap to a bud;  and is due, not to  a vis d tergo, or to a relaxed state
of bloodvessels, but to a  demand from the tissue for more blood, an
attractive force,  by which the direction is  regulated,  and the quan-
tity also.   The annual renewal of the antlers of the stag, the enlarge-
ment of the  testes of  birds at  particular seasons, that  of the breasts
of women during  pregnancy  and  after parturition, all these cases
afford instances in which a demand for  blood is created at some point
of the  periphery,  and a greater flow is  established  to the organs
there placed  than previously took place to them.
  We can afford no satisfactory explanation of the localization of
certain changes in  the capillary circulation, unless  on  the hypothesis
that the constituent elements of the affected parts  are primarily dis-
eased, and that their demand for blood is, in consequence, increased

  * The theory of inflammation is extremely well  discussed in Mr. J. Simon's Lec-
tures on Pathology, Lect. IV.  See also Mr.  Pagefs Lectures on Inflammation. 
THE CAPILLARY CIRCULATION.
699
or diminished, and the flow of blood  regulated accordingly.  Thus
the  development of  gout in  a joint  takes  place often with  such
rapidity that it appears to the  patient  to be  sudden;  the train of
phenomena  being in such cases,  first, a  change in the tissues, so
gradual as to be unperceived, then, an increased flow of blood, to such
an extent as to cause the heat, the throbbing, and pain which cha-
racterize such affections.   Again, certain  poisons, which seem  as  it
were to spend their force, in great part at least, on the skin, do not
cause a change in the whole capillary circulation so much as in points
of it, here and there, determining an increased flow of blood to this
point and that, and leaving  the intervening  parts  unaffected.   The
well-ascertained fact, ubi  stimulus, ibi fluxus,  cannot be so well ex-
plained on the hypothesis that the  stimulus creates a relaxation  of
the  tunics of the capillaries of the  part,  because that is opposed  to
analogy, as on the supposition that under the operation of the stimulus
the demand  for blood in the tissues  is augmented,  and the capillary
force becomes exalted in  the  part, in virtue of which  a greater flow
of blood is determined to it.
   The phenomena of asphyxia show that a stoppage of the circula-
tion  may take place at  the  capillaries,   notwithstanding  the  con-
tinuance of the heart's action.   When the access of air to the lungs
is excluded,  the circulation ceases at the   pulmonary capillaries, and
on examination  after death the left auricle and ventricle are found
quite empty, and  the right cavities of the heart gorged with blood.
The repletion of the  latter cavities, and the emptiness of the former,
indicate the position at  which the obstruction  to the circulation
took place.    Instantly the air is  readmitted to the lungs,  the blood
assumes a bright red colour and  the  circulation goes on, indicating
that the changes  which  take  place between the  air and the blood,
must generate a force which exercises an  important influence on the
capillary circulation,  and  without which the heart's force is insufficient
to propel the blood through the pulmonary vessels.  Dr. John Reid*
argues, as we think with  justice, from the instantaneousness of the
restoration of the  circulation on the readmission of air, that its stop-
page must be due to the  cessation  of the respiratory changes, and
not  to a contracted state  of the capillary arteries as suggested by Mr.
Erichsen, because the relaxation of those arteries, like  their contrac-
tion, is a slow process,  requiring tAvo or three minutes to accomplish
it.t

   * John Tieid, on the Cessation of the Vital Changes in Asphyxia. Phys. Researches,
Edinb. 1848.
  +  Our friend and colleague,  Dr. Geo. Johnson, has discovered a very interesting
point, connected with the  minute vessels  of the kidney in cases of chronic nephritis
with shrinking of the organ, which furnishes an additional instance of retardation or
stoppage of the circulation at  the capillaries, despite the continuance of the heart's
action.  Dr. Johnson shows  that, under the influence of defective secretion, the renal
circulation is greatly retarded  in the intertubular capillaries, and that the Mulpighian
capillaries are  consequently subjected to a greatly increased pressure and distension,
giving rise to an escape of serum, or of blood, when a. rupture of one or  more of the
minute vessels  has occurred.  When such  a state of  vessels has been of long duration,
as in chronic inflammation of the kidneys, Dr. Johnson finds the capillary arteries much
thickened, by reason of hypertrophy of their circular and longitudinal fibres, and a thick- 
700
THE CIRCULATION OF THE BLOOD.
  On the whole, we are disposed to the following conclusion respect-
ing the  capillary circulation, namely,  that  it is maintained by  the
vis  a tergo  of the heart; but it is regulated and modified  partly by
the elasticity of the walls of the capillary bloodvessels, partly also by
their  contractility, which is greatly influenced by changes  in  the
nervous  system, but chiefly by the operation of a force, developed by
those chemical and physical changes, which take place betAveen the
blood and the tissues,  and  in which the phenomena of nutrition es-
sentially consist.   For the due exercise of this force, a normal consti-
tution  of both the blood and the tissues is the most important condi-
tion.

   Of the Circulation in the Veins.—The blood moves in the veins in
a continuous stream, a fact sufficiently apparent to all  who  have
watched its escape from  a vein after venesection, and  as  is likewise
apparent in  examining  the circulation in  minute veins  under the
microscope.   The velocity of the  Arenous current is considerably  less
than that of the arterial, but greater than that of the capillaries, and,
as Volkmann has shown, it increases  in the veins which are nearest
to the heart.
  That the vis a tergo of the heart is sufficient to maintain the circula-
tion in the veins, is abundantly proved by all those facts which have been
already  recited Avith reference to its influence on the capillary circula-
tion.   Of these, the most important are the  experiments of Magendie
already  referred to (p. 695), and the fact that in states of debility a
distinct  venous pulse  is  formed  synchronous  with  the heart,  and
evidently resulting from the extension of the heart's impulse through
the capillaries.  Such a pulse (which may be  called the systolic venous
pulse) is in rare instances observable in the human subject in  states
of great prostration of strength, but has been most frequently noticed
in observations on the circulation of cold-blooded  animals.
   Pulsations synchronous with  the heart's  beats may be not uncom-
monly noticed in  the  human subject, which it is  important that the
observer should not confound with those resulting from the extension
of the heart's impulse, as  above  referred to.   These  may be  called
the regurgitant, and the communicated venous pulse.   The former
is caused by  the regurgitation which takes place from the right auricle
into the large venous trunks  connected  with it  at  every systole of
that cavity.  In a state  of health, the regurgitation is so  small  that
its  influence  extends only to the larger veins—but when the right

ened and opaque state of the walls of the Malpighian capillaries;  while the intertubu-
lar  capillaries and veins remain unaltered, save in a diminution of their number, some
having become wasted and obliterated in consequence of the arrested action of the secret-
ing cells.  These observations show an obvious connection between the activity of the
organic changes connected with the act of secretion and that of the capillary  circula-
tion, and, indeed, an interdependence between the movement of the blood and the
secretory function of the gland;  but the hypertrophy of the muscular fibres of the
capillary arteries seems rather to indicate that, in these extreme capillary arteries,
some propulsive power (vis  a tergo) may be exercised  by their muscular fibres in pro-
moting the flow through the capillary system.—See Dr. Johnson's Paper on Albumi-
nous Urine and Dropsy, in the 33d vol. of Med.-Chir. Trans. 
THE VENOUS CIRCULATION.
701
cavities of the heart are  dilated, a  much larger quantity of blood is
regurgitated and a  distinct venous  pulse is visible in the superficial
jugular veins, and sometimes in all the superficial veins which are
distributed over the neck and upper part of the chest.  The  com-
municated venous pulse  results simply from the  proximity of some
large artery, which  in its pulsations communicates to the vein a move-
ment of a similar nature.
   Hales and Poiseuille estimated the force of the current of blood in
the  veins; the former  by the introduction of tubes into the large
veins, as in  his experiments upon arteries; the latter by the hsema-
dynamometer; and  their observations have lately been repeated by
Valentin  and Mogk.   Hales found that the blood rose to four feet
two inches above  the  level of the heart, in  a tube inserted towards
the  head into  the jugular vein of  a  mare, the  blood rising several
inches Avhen the animal strained, but subsiding again when he became
quiet; hence it is plain that the force  of the heart, competent as it'is
to maintain a column of  such a height, must be amply  sufficient to
return  the blood to the  heart.  Valentin and  Mogk's  observations
show that the force  of the blood in the veins of dogs is equal to one-
eleventh or one-tAvelfth of that in the  corresponding arteries.
   The venous circulation is influenced a good deal by the respiratory
movements,  A\*hich  tend  partly to promote, partly to retard  it.
These effects are produced most plainly by the forced movements of
respiration.   Thus a deep inspiration, by enlarging the capacity of
the chest, generates a tendency to a vacuum, which, under the pressure
of the  surrounding  atmosphere, is  filled chiefly by the  rush of air
into  the  trachea, and  through it  to the lungs, but  partly by the
afflux of the blood, which must be principally venous, since  the semi-
lunar valves would oppose any reflux in both the great arteries.   Sir
David Barry illustrated the influence  of inspiration in favouring the
centripetal  flow of  blood.  He  introduced one end of  a bent glass
tube into the jugular vein of a horse, the vein being tied above the
point at Avhich the tube was inserted; the other end of the tube Avas
immersed in a coloured fluid.  At each  inspiration the fluid rose in
the tube, being draAvn towards the chest, whilst  during  expiration it
sank or remained stationary.
   Forced expiratory efforts, on the other hand,  retard the venous
circulation, as may be  well illustrated by holding  the  breath  for a
few seconds, or straining strongly,  Avhen the veins, especially those
of the neck  and chest, will swell up and become distended; but as
soon as the  breathing is restored, they return  immediately to  their
former size.  Hence it is that persons subject to frequent disturb-
ances of the respiratory actions, as in asthma or  dyspnoea of any
kind, exhibit, after  a time, more or less enlargement of the venous
system.
   Disturbances in  the  respiratory actions seem to affect the circula-
tion  and especially that  in the veins, more extensively in another
way, namely, through  the pulmonary  capillaries.  The  imperfect
respiratory changes, consequent upon the disturbed breathing, retard
the floAV of blood  through the capillary plexus, which undergoes, by 
702
THE CIRCULATION OF THE BLOOD.
the dilatation  and rupture of the air-cells, considerable stretching
and widening of its meshes, and even becomes obliterated in parts.
These changes also create additional obstacles  to the pulmonary cir-
culation, Avhich impede the Aoav from the right ventricle, and increase
the backward pressure of the blood on the Avails of that cavity, causing
it to become dilated and hypertrophied.  It is in this way that are
produced the hypertrophy and dilatation of the right cavities of the
heart, Avhich, to a greater or less extent, are invariable consequents
of frequent attacks of asthma or bronchitis.
   The influence of the respiratory movements upon the venous circu-
lation is shoAvn in the clearest manner by the use of the Inemadynamo-
meter, as in the experiments of Poiseuille, Magendie, Ludwig, Va-
lentin, and Mogk, the column of mercury rising in expiration, and
falling in inspiration ; and these experiments likeAvise prove that this
influence is only felt in the large  veins near the chest, and not in the
more distant ones.   The influence of expiration in retarding is much
more poAverful than that of  inspiration  in promoting the venous cir-
culation ; for the same physical condition of the chest which exists at
the commencement  of  inspiration, and  which favours  the rush of
blood to it, tends rather to delay the  escape of blood through the
arteries, and the heart's action is thereby much weakened and  often
depressed.                     t
   Muscular movements likeAvise  favour the venous circulation, as is
well shown in the operation of venesection, Avhen the patient is made
to move his fingers freely, the flow of blood from  the vein  being
thereby immediately increased.   It is the action of the valves Avhich
determines the centripetal flow of the blood in the veins under mus-
cular pressure;  for, as the  contracting muscles simply compress the
veiny, the blood would be driven either or both ways ; but the valves
affording a direct impediment to the centrifugal flow, it is forced to
take the opposite course. This is obviously one of the ways in which
exercise favours the circulation and promotes the general health.
   It has been supposed that the contraction of the auricles by par-
tially emptying those cavities, calls into play an elastic force in their
walls, which favours the rush of blood  into them, and that thus  a
certain suction power of the auricle may be enumerated among the
forces which aid the venous circulation.   The idea is illustrated by
exhausting  an India-rubber bag, to which a glass  tube  is  attached,
and then immersing the open extremity of  the latter in a vessel of
water, Avhen the Avater will  pass freely into  it under the  influence of
the atmospheric pressure on the water.   The principal fact in favour
of this view is  the experiment of Wedemeyer, which is thus detailed
by Muller:  " Wedemeyer  and  Guenther  having tied the jugular
vein of a horse, made  an opening into  it between the  ligature and
the heart, and introduced a catheter, to which a bent glass tube had
been cemented.  The longer descending branch of the tube (tAVO feet
in length) was  placed  in  a glass  filled with  water.   At  first, the
inspirations and the contractions  of the  heart Avere nearly simul-
taneous, and of  the same frequency—namely, thirty in a  minute—
and the coloured water  rose suddenly two or more inches in the tube 
SUCTION POWER OF THE AURICLE.
703
at the  moment of each inspiration and pulsation of the heart, and
sank again each time to its former level.  The inspirations gradually
became  tAvice as frequent as the pulsations of the heart, and Wede-
meyer  and Guenther now observed, for a long period, that the rise
of fluid did not take place at  each inspiration, but at every beat of
the heart, and, consequently,  simultaneously with  each dilatation of
the  auricle.   This experiment,"  adds Muller, "seems  to  prove be-
yond doubt  that the heart exerts a power of suction."   It is  most
probable, however, that this power is extremely small, and  that  it
does no more than counteract the  obstructive  influence which would
otherwise arise from  the regurgitation Avhich takes  place into the
large venous trunks from  the  auricles at each systole.
   The  veins  possess a certain tonic influence similar to that of arte-
ries, by which they can adapt  themselves to the varying quantity of
their contained blood.   This  is,  doubtless, due to the  presence of
muscular fibres in the tunics of veins  already described;  the poAver
of these fibres to alter the caliber of the vein is clearly demonstrable
by the  influence of galvanism,* which causes  an appreciable diminu-
tion in  the size of the vessel at the point of transit of the current.f
   The  floAV of blood in the veins, then, it may be concluded, is main-
tained  chiefly by that same force  through which it is driven through
the  arteries  and capillaries, aided by the sort  of suction in the cen-
tripetal direction Avhich is caused by inspiration and by the diastole
of the  auricles, and promoted likewise by the contraction  of the
various muscles, among or through which the  veins pass,  and by the
position and  mechanism of the valves.
   It is proper to  observe  that the venous circulation being moved
by less  force than the  arterial (the  heart's  power  having already
very much expended itself on the  arteries and capillaries), is  more
influenced  by  gravity—either  favourably  or otherwise—than the
arterial.  Hence, in dependent positions, as in the  loAver extremities,
when the blood has to ascend against gravity, the veins are apt to
swell, and to acquire a permanent dilatation and thickening of their
coats from the retardation of the current in them.  It is important

  *  See  Kolliker's experiments—Siebold and Kolliker's Journal.
  f AVhile these pages were passing through the press (Feb. 1852), Mr. AVharton
Jones announced, in a paper read to  the Royal Society, the discovery that the veins
of the bat's wings contract and dilate rhythmically, and that, they are provided with
valves, some of which completely, others only partially, oppose  regurgitation of blood.
The rhythmical contractions and dilatations are constantly going on, and that at the
rate  of ten contractions in the minute.  During contraction, the flow of blood in the
vein  is accelerated, and on the cessation of the contraction the flow is  checked, with
a tendency to regurgitation.   But this check is usually only momentary; already,
even while the vein is  in the act of again becoming dilated, the onward flow recom-
mences  and goes on,  though  with  comparative slowness, until the vein contracts
again.   It is the heart's action which maintains the onward flow of blood during the
dilatation of the vein,  whilst it is the contraction of the vein coming in aid of the
heart's action, which causes the acceleration.  Mr. Jones states that he has not been
able  to  observe unequivocal  evidence of tonic contractility in veins, as Kolliker's
experiments indicate; he likewise affirms, in opposition to a statement of Mr. Paget,
quoted at p. 602, that nowhere do the arteries and veins of the bat's wing communi-
cate, the  only communication being the usual one through the medium of capillaries.—
Proceedings of the Royal Society, Feb. 1852. 
704
THE CIRCULATION OF THE BLOOD.
that this fact should be kept in view by the practitioner in the treat-
ment of Araricose Areins,  and of anasarcous states of the limbs.
   We have seen that the blood moves in the arteries with considerable
velocity, and likewise Avith great, although much diminished, rapidity
in the capillaries;  its rate  of motion increasing  again in the veins,
especially in those  nearest the heart.  It may be inferred from these
facts, that any given particle  may complete the round of the circula-
tion in  an  exceedingly brief period.   It is an  important problem—
especially with reference to the time in Avhich poisonous substances
introduced into the blood  may produce their effect—to determine in
what space  of time a substance introduced into one part of the circu-
lation may reach the most distant part; or how soon, for instance, a
substance inserted  into the right jugular vein may, after traversing
the right heart, the pulmonary circulation, the left  heart, the  systemic
arteries, return to  the systemic veins, and be found in the left jugular
Arein.
   In the present  state of  our knowledge no exact solution of this
problem can be given.  But a very close approximation to the truth
may be obtained—first by calculation, secondly by experiment.   By
calculation, we can determine in Avhat space of time the whole blood
of the  body may  circulate through the heart.   The  data  for this
problem are, the weight of the whole quantity of blood in the body,
the quantity of blood expelled at each systole from the left ventricle,
and the number of systolic actions  in a minute, or, more exactly,  the
duration of a pulse.  It is  plain that, if the  left ventricle  contract
seventy times in  a  minute, and  at each contraction expel five ounces
of blood,  according to  Valentin, or six ounces  (400th part  of  the
Aveight  of  the body), according to Volkmann, a  quantity  of blood
equal to that of the whole body will in that space of time pass through
the  heart.  It may,  then,  be  assumed  from  calculation,   that  the
circulation  may be completed in a period of  time, which,  in round
numbers, may be expressed as one minute.*
   Hering Avas the first to experiment on this subject, his object being
to ascertain how  soon a substance easily recognized (as ferrocyanide
of potassium), Avhen introduced into one  part of the circulation  as
the right jugular vein, could be detected in a distant part of the circu-
lation as the  left jugular.  Hering found that this substance Avould

  * Arolkmann's formula is t = z _ where t is the required mean time of the com-
                            y
pletion of the circulation, x is the whole quantity of the blood,  y the quantity expelled
at each systole, and z the mean duration of a pulse.   AVhence, taking the mean quan-
tity of x at 30 lbs., and of y at 6.2 ounces, the duration of a pulse being 0.85  of a
second, we get t = 0.85------= 67.5 seconds.  And as, according to Valentin, the
                     188
whole quantity of blood is equal to about l-5th the weight of the body, and as from
A'olkmann's researches  the quantity expelled at each  systole of the ventricle is ¥^5th
of the weight  of the body, calling this weight p, then x = _ p and y =___ p,  and

t  = z —£_, therefore t =80 z; whence it appears that the time  of the  circulation
      P
is directly as the duration of a pulse, and inversely as its frequency. 
RAPID EFFECTS OF POISONS.
705
pass from the right to the left jugular veins in from twenty to thirty
seconds ;  and from the jugular vein to the great saphena  in tAventy
seconds;  from  the jugular  vein to  the masseteric artery in  from
fifteen to  thirty  seconds.    Results  quite  confirmatory have  been
obtained from  like experiments by Poiseuille,  and also by Blake.
The  former found that ferrocyanide of potassium, with acetate of
ammonia, or nitrate of potash,  passed from one jugular vein to the
other in from eighteen to twenty-four seconds;  but that the addition
of  alcohol  retarded the rate of transit  to from forty to  forty-five
seconds.   Blake found that nitrate of baryta passed from the jugular
vein of a horse  to the opposite carotid artery in from fifteen to tAventy
seconds.   He found also that the poisonous influence of strychnia on
the nervous system, showed  itself  in tAvelve seconds after injection
into the jugular vein;  in a fowl, in  six seconds  and' a half; and in a
rabbit in four seconds and a  half.*
   The results  obtained from calculation, as regards the rate of the
circulation,  are  less  conclusive  than  those  by experiments ;  for the
obvious reason  that we have only the approximative value of  the two
principal quantities Avhich enter into the calculation, namely, that of
the mass of blood in the body, and that expelled at  each  systole.
But the results of the  two modes of inquiry are sufficiently  near to
each other to denote that the round of  the circulation is completed
by any given portion of blood in a  marvellously brief period, Avhich,
in  man, probably, rather  falls  below than  exceeds a  minute.   We
need not, therefore, have recourse to any other hypothesis to  explain
the rapid effects of certain poisons, than  that they enter the blood,
and Avith it  are  whirled with immense velocity through the substance
of the most  vital organs.

  * Hering in Tiedemann and Treviranus Zeitschrift fur Physiol, b. iii. Poiseuille's
Ann. des Sc. Nat. 1843.  Blake, Edin.  Med. and Surg. Journal, 1841.  See also on
this subject Volkmann's 10th chapter.
   On the subjects discussed in the preceding chapter, the reader is referred to the
various systematic works on Physiology, to the supplement lately published by Valen-
tin, and to Dr. Allen Thompson's very comprehensive article, Circulation, in the Cyclo-
paedia of Anatomy and Physiology.   On the anatomy and physiology  of the  heart,
Kurschner's article in AVagner's Handworterbuch, and Dr. Jno. Reid's  article in the
Cyclop, of Anat. may be consulted; and as regards its motions and sounds, we refer
to the reports of the Committee of the British Association, collected in  the Appendix
of Dr. C. J. Williams's work on Diseases of the Lungs, to Dr. Blakiston's admirable work
on Diseases of the Chest, to Dr. AValshe on Diseases of the Heart and Lungs, and Dr.
Herbert Davies on the same subject;  and on the physics of the circulation, to Hales's
Statical Essays, vol. ii.;  to Dr. Young's Croonian Lecture on the Functions of the
Heart and Arteries, Phil. Trans. 180'.), and Medical Literature, p. 605;  Poiseuille sur
la Force du Cceur Aortique, in Magendie's Journal, vol. viii., and his essay, Recherches
sur l'Ecoulement  des liquides consid^re" dans les Capillaires Vivans, in the Journ. des
Sc. Nat. 1843; to the Essays of  Ludwig, Spengler, and Mogk, in Miiller's Archiv;
Magendie, Lecons sur les Ph6nomenes Physiques de la vie, and especially to the very
able work of Volkmann, Die  Haemodynamik nach Versuchen,  Leipzig, 1850,  which
we only received when these  pages were in type.  The following works may also be
mentioned as containing interesting matter relating  to the  circulation in general:
Dr. Graves's  Clinical Lectures, lect.  i. on  the Circulation; Dr. Todd's  three Clinical
Lectures on the Pulse, Lond.  Med. Gaz. 1851; Draper, on the Forces which produce
the Organization of Plants, New York, 1845; Prof. Jno. Reid's essay on Asphyxia, in
his Physiological and Pathological  Researches, ed. 1848. 
706                        RESPIRATION.
                        CHAPTER  XXIX.

ON RESPIRATION.—COMPARATIVE ANATOMY OF THE RESPIRATORY OR-
  GANS.--ANATOMY OF THE HUMAN LUNGS.--TRACHEA.—BRONCHI.—
  BRONCHIA.—ULTIMATE  PULMONARY TISSUE.—MOVEMENTS  OF RE-
  SPIRATION.—FREQUENCY OF RESPIRATIONS, AND RATIO TOTHE PULSE.
  —AERIAL CAPACITY OF THE LUNGS, AND AMOUNT OF AIR BREATHED.
  —CHANGES  IN  THE  RESPIRED  AIR,  CARBONIC  ACID  EXHALED—
  OXYGEN INHALED.--CHANGES IN THE BLOOD.—NATURE OF THE RE-
  SPIRATORY PROCESS.

  Respiration is that function by  which an  interchange of gases
takes place between  the interior of an organized being and  the  ex-
ternal medium;  and in the animal  kingdom oxygen is the gas re-
ceived, and carbonic acid the gas  given out.  Every part of the sur-
face to Avhich  the outer medium  (whether  air or  water) has access
may be considered to share in respiration; but in all, except some of
the loAvest animals, special organs are provided in which the inter-
change can be more  readily  effected.    These organs  in all  cases
consist of a membranous surface,  adapted for contact with the sur-
rounding medium, and capable  of exposing the fluids of the body in
an especial manner  to the action of the air.   The interchange of the
gases  through this respiratory membrane  is  essentially  a purely
physico-chemical  phenomenon,  and  must be studied as such.   The
very great variety  of structures  with which different  animals are
furnished  for  this function, merely  present us with modifications of
the  elementary   conditions  whereby its activity and  extent  are
governed in the several instances.  The contact of air with the blood
may be influenced (1) by atmospheric concentration or  dilution.   In
water-breathing animals, the air breathed is that- held in  solution in
the water, and is  of course in  very small quantity.  The density or
rarity of the air,  according to  temperature  and barometric pressure,
may perhaps affect  the activity of respiration  in air-breathers.  (2)
The extent of  the respiratory surface; (3) the thickness  of the  tissue
between the air and the blood, and (4)  the more  or  less complete
manner in Avhich  the general mass  of the blood is brought from the
tissues to the respiratory surface—all these exert much influence on
the activity of respiration.

  Comparative Anatomy.—In Entozoa, polyps, and medusae,  no  special respiratory
organ exists.  In star-fishes and sea-urchins,  among the echinodermata, the sea-water
gains access to cavities among  the viscera,  and  is renewed continually by  special
organs, principally cilia.  The holothuria has an internal system of arborescent tubes
opening from the cloaca, receiving water, and, according to Tiedemann, serving for
respiration; its branches end in vesicles.  In annelida, there are sometimes tufted
branchiae, or gills, as in the  arenicola, or  sand-worm; sometimes sacs opening sepa-
rately,  as in lumbrici and leeches. . The  Crustacea have branchiae attached cither to
the feet or abdominal surface.  Of the arachnida, some, as the scorpion, have  pulmo- 
ORGANS OF RESPIRATION  IN MAN.
707
nary sacs, or lungs, with parallel  lamellae, situated on the abdomen in from one to
four pairs, and each opening by a separate stigma;  others have a system of ramified
internal air-tubes, termed tracheae, or spiral vessels (from a spiral thread in their wall);
and some both tracheae and pulmonary sacs.  The myriapoda and all the insecta have
tracheae.  These penetrate the internal organs to their remotest parts, anastomosing
freely, and open at several points on the surface.  Insects which breathe in water, as
well as many aquatic larvae, have branchiae which first separate air from the water,
and then transmit it  along the tracheae.  The respiration by tracheae is probably a
very perfect one, the blood and tissues being  aerated throughout the body, at every
spot in which they are being deteriorated.
  Among Jlollusca, some have branchiae, or  gills, as the cephalopods, the concliifera,
and some gasteropods.   Other gasteropods have a pulmonary sac, or lung, e. g. the
common snail.  This sac opens and shuts so as to change the air,  and on its surface
the venous blood is distributed ere it reaches the heart.
  Fishes present the greatest  development of  gills.   There are four branchial arches,
bearing vascular plates with lateral offsets.   Matteucci estimates  the surface of the
gills  of the common ray  to measure 2,250 square inches.  All the blood is driven by
the heart, through the gills, to the aorta, and  thus comes into close proximity to the
water in  contact with the branchial surface.   The capillary network has  close and
regular meshes.
  Reptiles have a rudimentary form of lung, combined in many instances with  gills,
during a part or the whole of life, e. g. in the  frog, the gills exist only in the tadpole
state; in the proteus, they remain through  life.  The pulmonary sacs of reptiles are
more or less cellulated on their inner surface,  and receive  a portion only of the venous
blood in each circuit.
  In Birds and Mammalia respiration is much more active, being performed by means
of large and highly-divided lungs, placed within a bony framework, capable of re-
ceiving and rapidly renewing the  air in large quantities, and giving passage to the
whole blood of the body on its way from the veins to the  arteries.  In Birds, there is
a series of openings from the pulmonary air-tubes, by which the air gains access to
passages and spaces among the other organs  and tissues, rendering the body specifi-
cally lighter, and, perhaps, in some degree, aiding respiration.  Farther varieties in
the structure of the lungs, modifying their respiratory power, will be alluded to  when
the human lungs have been described.


   Organs of Respiration in Man.—The lungs, placed in the  thoracic
cavity, receive  air by  the nasal passages and trachea, and venous
blood from the right side of the heart  to transmit it  to  the left. They
form  a double organ,  with a single  common air-tube, the  trachea,
and a single common pulmonary artery, supplying the venous blood.
These vessels branch first  into  a right and left, and then into many
subordinate ramifications up to the ultimate air-cells and capillaries.
Four veins  carry off the aerated blood to  the  left side of the heart.
Being penetrated by the air, the lungs are the lightest organs in the
body.   In the fcetus, before breathing, they are  small,  and transmit
only so much blood as  is requisite for their OAvn growth;  but when
the air enters their volume augments, their absolute weight increases
in  consequence of  the greater afflux of  blood,  Avhile their  specific
gravity diminishes.   Krause  estimates  the average absolute weight
of the lungs in men to be three pounds  and a  half, in women  two
pounds and three-quarters, and the left to be  smaller than the right
by one-tenth.  The weight, as compared with that of the whole body,
is as one to forty or fifty.
   In shape, the lungs are adapted to that of the cavity in which  they
are lodged; their apices rise into  the neck, their bases rest on the
diaphragm, between them lies the heart Avith the great vessels. They
are invested by a serous covering, the pleura,  Avhich, after lining the
thoracic walls, is reflected over them  at their  root, and dips  into 
708
RESPIRATION.
those fissures, which serve to  subdivide them imperfectly, the right
into two, the left into three, lobes.
   The trachea descends in the middle line from the larynx (which is
a complicated development of it for the protection of the orifice  of
the respiratory organ, and for  the  production of sound, and which
will be afterwards described), as far as  opposite the second or third
dorsal vertebra, being straight, sub-cylindrical, flat behind, and about
three-quarters of an inch Avide.  It is held permanently open by from
sixteen to twenty cartilaginous  rings,  flattened in the direction  of
the wall in Avhich  they are imbedded, and deficient behind  to  an
extent of one-third.  Of these,  the highest is the  thickest, and the
loAvest is adapted by its shape to the bifurcation of the trachea into
the tAvo bronchi.  The free ends of these cartilages  are sometimes
forked, and  contiguous  ones are now and then joined.   They are
immediately invested with  perichondrium, a dense, Avhite, fibrous,
inelastic membrane, and  are connected by a continuation of it ex-
tending betAveen their borders and ends.   This inelastic membrane,
by its toughness, resists undue extension in the longitudinal direction.
   Looking on the trachea behind, we observe  the  space betAveen the
ends of the cartilages covered  with  irregularly interwoven fibres,  in
the course of which we haATe discovered unstriped  muscular fibres  to
occur, especially about the bifurcation.   In this  fibrous layer are
recesses for the tracheal glands, and on dissecting it off these glands are
exposed, together Avith a thin  sheet of  transverse unstriped fibres,
completing, as  it  Avere,  the circle of  the  cartilaginous rings, and
knoAvn as the trachealis muscle.   The  fibres of this are  attached a
little Avay from the extremities of the cartilages on their inner surface,
and in  contraction  must serve  to approximate them,  and thus   to
narroAv the canal.  In the horse, they are inserted three-fourths  of
an  inch  from the extremities,  which almost or quite overlap.   In
birds, they are composed  of striped fibres.
   The cartilages,  their  interspaces,  and  the  trachealis muscle are
lined by  a thin layer of longitudinal, elastic, anastomosing fibres, uni-
formly spread out except over the trachealis muscle, where they are
gathered up into longitudinal bands, sometimes one-twelfth of an inch
thick,  very visible  through the mucous  membrane.  These take a
serpentine course doAvn the bronchi, and preserve their anastomosing
character.   The trachea OAves its elasticity in the longitudinal direc-
tion to the fibres now described.
   The mucous  lining of  the trachea, the  essential part of the duct,
to which the above are  accessory, is continuous  through the glottis
with that  of the pharynx, and  physiologically Avith the respiratory
compartment  of that cavity, and with the nasal passages (see ante
p. 522).   It is covered with ciliated  epithelium, and the direction  of
the movement is probably upwards toAvards the glottis.   The tracheal
glands are productions  of this membrane, and  appear as a layer  of
reddish,  distinct granules, behind the trachealis  muscle,  each one
being furnished with a separate duct, traversing first the muscle and
then  the  layer  of longitudinal  elastic  fibres, to open  on the inner
surface of the tube.   These glands appear to be tubular, not follicu- 
THE HUMAN LUNGS.
709
lar, and are thus related rather to the sudoriferous  than to the sali-
vary system.   They probably furnish much  of the halitus of  the
breath and may determine its odour.
  Of the bronchi or primary subdivisions  of  the trachea, the  right
is the shorter, wider, and  more horizontal; the  left longer  to pass
under the aortic arch.  Their walls resemble those of the  trachea
with slight  modifications.  At the root of the lung, each breaks up
into branches corresponding  to the lobes (lobal bronchia), and  these
again into secondary, tertiary, and terminal bronchia, the last named
being from one-fortieth to  one-sixtieth of an inch in diameter.   The
terminal bronchia pass to portions of the pulmonary substance more
or less distinctly mapped out by areolar  tissue, and termed lobules.
   Coats of the Bronchia.—All these become gradually thinner as
they  approach the  air-cells.   The  cartilaginous pieces, Avhich  are
irregular in shape and position in the lobal bronchia, become reduced
to mere flakes,  and finally cease  in those' of  one-sixth  or one-tenth
of an inch in diameter (Fig. 204).   The last  are seen mostly where
branchings  occur.   The  muscular  fibres  of the
trachea are continued down even to the terminal      FiS- 203-
bronchia,  but instead  of filling up only the gap in     —*f^s^l§l§|
the cartilaginous framework, they form  a uniform     ^0S^:.
layer encircling  the canal,  but excessively  thin.     Blll§fi|;
The fibres  are  here  arranged   in  anastomosing      Sp^fSPS
bundles (Fig. 203).  Within the muscular layer is      ^^^^^^
that of the longitudinal elastic fibres, here disposed     J&?^
as an even layer, and  representing the  submucous   /V>5V"~     j
areolar  tissue.    The  ciliated epithelium  and the   vf^
basement-membrane  of the  mucous  tissue  both
descend into the terminal bronchia. _ On the ex-  w^St
terior of the bronchia is some areolar tissue separat-  trans^erse  plexiform
                    .       .              . r      arrangement  of  the
mg them from the neighbouring masses of air-cells,  muscular layer, and its
   ,     ■ ■  -i   •, -i  , i      ,  •     •   i    i        disposition at the orifice
and associated with the arteries, veins, lymphatics,  of a branch.  Erom a
and nerves belonging to  the bronchial wall.         Kto^y-~Magnt
   The bronchial arteries are usually two, coming
from the aorta, but irregular.  They supply the coats of the bronchia,
and have corresponding veins.  Their  capillaries anastomose with
those of the pulmonary  artery where the  terminal bronchia become
lobular  passages.   The  distribution  and actions of the pulmonary
nerves have been already discussed (pp. 498-506).
   Ultimate Pulmonary Tissue—Lobules.—In  some  parts of  the
exterior of  the  lungs, particularly near the  borders, and in  some
animals throughout, may be  noticed  a sort of mapping out of the
pulmonary  substance  into small  polyhedral  masses  separated by
areolar  tissue,  and having a very irregular  shape.   These  are the
lobules of the lungs.   They  can only be made out in  certain situ-
ations, even by dissection, for it does  not appear that  the  whole
human lung is  thus subdivided by areolar septa.   Nevertheless, it
seems certain that each  terminal twig of the bronchus is in  relation
with only its own proper set of air-cells, and that such sets of cells
do not communicate except through the medium of the bronchia.   In 
710
respiration.
Fig. 204.
ife
this sense lobules exist everywhere, even when not isolated by areolar
tissue, and in this sense we shall use the term,  as  conveniently de-
                    signating that series of air-cells, associated by
                    dependence on a single terminal  air-tube.   We
                    shall afterwards show how much difference exists
                    in the isolation of the lobules of the  liver even in
                    allied animals, and how  unimportant this variety
                    appears to be.
                      The superficial lobules derive a  covering on
                    one aspect  from the pleura, but are  separated
                    from  it  by rather dense areolar tissue, which
                    may be  dissected off  without  rupturing  the  air-
                    cells.    If  the  interstices  between  contiguous
                    superficial lobules be explored by the  knife, the
                    terminal bronchia are found Tit the bottom of the
                    fissures", each  going to a single lobule, and besides
                    these are seen branches of the pulmonary artery
                    and vein, not  running  in company, nor  limiting
                    themselves  to a single  lobule, but common to
                    contiguous lobules ; so that  the air-spaces of one
                    lobule do not  communicate with those of another
                    across the  interstices, but  the bloodvessels do.
                    On the  exterior of a  lobule we observe bubbles of
                    air of various sizes in its tissue, and if the bron-
                    chial tubes be injected, the lobule  is  distended,
                    and its  exterior presents a number of bulgings
                    knoAvn  as the air-cells, about Avhich  much con-
                    troversy has existed.   Their shape  seems irregu-
                    larly polyhedral,  like  the  lobules themselves.
                    The angles where three or more of "these cells
                    meet, are the points  at  which the terminal twigs
                    of  the  pulmonary  artery   and vein  penetrate
                    among  the  cells, after meandering  more or less
                    over the  surface of  the  lobule.  In their course
                    in the interior of the lobule, these twigs generally
                    run separately in the lines of junction of three or
                    more cell-walls, branching as they run, and break-
                    ing up  into their capillaries on either hand.
                       As the superficial lobules  are truncated where
                    they form the surface of the lung, so the cells are
 truncated where they form the surface of the lobule.   This is most
 decidedly the case where the lobules are well defined,  and  admit of
 separation;  but where contiguous lobules are not isolated by areolar
 tissue (as in most parts of the interior of the lungs, and in the lungs
 of the smaller mammalia), their superficial  cells have  their inequal-
 ities mutually adapted  to  each other, and even their  walls  fused
 together,  so that  the  lobules would not remain  distinct, were it not
 that their air-cells do not communicate across the interval.
    To convey  a  correct, and at the  same  time  a simple, idea of the
 constitution of the pulmonary lobules, we  must regard each  as an
 Small  bronchial tube
laid open, showing the ar-
rangement of the last car-
tilaginous flakes. The tube
has been cut across above,
at the point where it pene-
trates the substance of the
lung, and below where it
has a diameter of about 1-
12th of  an inch.  The
elastic and muscular fibres
are not represented, but
both were so delicate as to
allow the adjacent air-cells
to be seen  through the
bronchial wall.   Ciliary
epithelium was traced in
the finest tube that could
be opened by scissors, viz.
of 140th inch diameter.
From a healthy man set.
twenty-five.  Natural size. 
THE HUMAN LUNGS.
711
elementary lung, perfect in itself as an arrangement of a respiratory
membrane adapted to the aeration of the blood.  First, the terminal
bronchial tube pertaining to each  lobule, loses its  epithelium and
muscular tunic at about one-eighth of an inch distant from the last
air-cell to which it leads, and is thus reduced  to basement tissue and
yellow elastic fibres, which become  blended into a single  coat, the
only membrane composing the tubes beyond, and the air-cells.  The
terminal bronchial tube, thus simplified, ramifies within the  lobule,
and its branches may be conveniently distinguished from the bronchial
tubes under the name of lobular passages.*   The lobular  passages
are wider  than the terminal bronchia,  and  are remarkable (being
honeycombed on  their interior) for  presenting a series of sacculi or
cells on their  wall.  These are the pulmonary air-cells.   They form
a number of bulgings of  the wall, and are separated from one another
by septa projecting inwards from the wall toward the axis of the pas-
sage (Fig. 206).  They each open separately into the lobular  passages,
and do not communicate with each other except through the  passages.
The terminations of the  several lobular passages are air-cells  coming
up to  the  surface of the lobule, but some of the  air-cells placed
laterally on the passages also contribute to form the surface of the
lobule.   The  air-cells thus surround and terminate  each lobular pas-
sage—and the lobule  consists of a number of lobular passages, as-
sociated by their dependence on a single terminal bronchial  tube, and
each clothed  as it were, on  its sides  and at  its end, with  a  honey-
comb of air-cells, with orifices open towards the cavity of the  passages.
Contiguous  cells of the same  passage are separated by a simple septum
or  process of the wall,  while the contiguous cells of neighbouring
passages are  separated  by a septum, likewise simple, formed by the
union of the  walls of  each.  Where the septa spring from the wall
of the passage, or in the angles  where neighbouring cells unite, the
wall is strengthened by a greater thickness of elastic tissue, which
often has the  form of arching bands of considerable strength in these
situations,  as  well as  around the  orifices  of the  cells.   Thus  the
lobular passages  and the air-cells  are  formed  of one tissue,  and
perform the same function.   They are a series of branched  cellulated
air-passages,  not  lined  with epithelium,  or  coated with  muscular
tissue, but highly extensible and elastic, of much  larger  aggregate
capacity than the terminal bronchia which lead to them, and resem-
bling closely, in general conformation, the reptilian lung.   Indeed,
an admirable notion of the essential arrangement of the lobules of the
mammalian lung may be derived from an examination of the terminal
parts of the  sacculated bronchia of the  lung of the turtle.   The
lobular passages are wider than the terminal bronchia of which they
are the  continuations,  and  than the cells which pullulate on  their
walls.   They also branch again and again in order to spread from
the terminal bronchial tube on every hand throughout the Avhole area
of the lobule; and  as their ramifications observe no certain order or
course, it  happens  that sections carried  through the lobules are
* Dr. W. Addison, Phil. Trans. 1840. 
712
RESPIRATION.
rarely found to follow any single passage far, so as  to display, in a
happy manner its mode of distribution.   Sometimes, hoAvever, this
is better seen than at others.
  [M. Rossignol has recently given  an elaborate description of the
pulmonary structure.   He insists particularly on the ultimate bron-
chial  ramifications being in  shape  like an inverted funnel, and he
terms  them  the  infundibula.   The cells, forming a honeycomb on
their interior, he calls the alveoli (Figs. 205 and 206).  Emphysema,

                              Fig. 205.
 Thin slice from the pleural surface of a cat's lung, considerably magnified. At the thin edge, bed,
alveoli are seen. In the centre (as a), where the slice is thicker, alveoli are seen on the walls of infundi
bula.—From Rossignol.

according to this author, seems to consist in a distension of the pas-
sages and cells, and a  breaking down and  obliteration of the septa,
first between the cells of the same passage  and then betAveen  neigh-
boring passages, and even betAveen contiguous lobules.
  The  diameter of the lobular  passages is from  ■—  to $r  of an
                        inch; and that of the cells from 3i0 to 3^
        Fig. 206.         of an inch according  to our measurements.
                        In  a  preparation of  the  lung  of the  calf,
                        given  us by  our friend Professor  Retzius,
                                        An;  and Dr.   W.  Addison
2<J0'
to
5(53
of an  inch.—
                        they measure g  <j,
                        makes them from
                        Ed.]
                           The  skeleton  of  the  lobule  is  thus an
                        elastic  membrane elaborately arranged,  so
                        that the  air  may be  brought into  contact
                        with it  for the most part on both its surfaces.
                        Over this membrane the Avhole venous blood
                        of the body is made  to course in a continual
stream, so as to  be submitted to the  action  of the air.
   Vascular Element.—The pulmonary artery, conveying the venous
blood to the lungs, is about as large  as  the  aorta, and  is furnished
with a triple valve at its origin from the right ventricle of the heart.
It soon diA'ides into a right  and left branch, which enter the lungs at
their  root,  and ramify  as far as the lobules,  in  company with  the
 Bronchial termination  in the
lung of the dog. a. Tube (lobular
passage) branching towards the
infundibula. b. One of the infun-
dibula.  c.  Septa projecting in-
wards on the infundibular wall
and formiug the alveoli, or cells.
—From Rossignol. 
THE HUMAN LUNGS.
713
bronchia.  Arrived at the lobules, the small branches of the pulmonary
artery do not enter in company with the lobular passages, but dis-
tribute themselves over the lobules in the interlobular fissures, pene-
trating at various points between the air-cells, and  occupying tubular
channels in the angles where three or more  cells meet. _  These chan-
nels are formed of the same yellow elastic tissue which constitutes
the lobular passages and  air-cells, and their  wall blends with the
proper coat of  the  terminal twigs of  the  pulmonary  artery  which
occupy them.  The capillaries of the lobule are given  off both from
the twigs which meander over the lobule and from those which pene-
trate it,  and they form a  network which covers  the walls of all the
cells of the lobule,  as well as of the lobular passages, anastomosing
with  some  twigs of the bronchial arteries where  the passages are
continuous  Avith  the terminal  bronchia.   This netAVork empties  its
blood into venules which lie first in intercellular channels similar but
intermediate to those which  lodge the arterial terminations; and
these venules collecting the now aerated blood from the interior and
also from the surface of the lobules, converge to larger veins which
lie in the interlobular spaces and tend towards the root of the. lungs,
but for the most part by  a route  distinct from  that of the arteries
and bronchia.   Thus the general mass of the lung may be regarded
as containing two series  of  ramified  canals, one transmitting the
bronchia (with their vessels and nerves) and the  pulmonary arteries,
the  other the  pulmonary veins.   This interesting fact  was well
described  by Dr. Addison, of Guy's  Hospital, in  a  paper  in the
Medico-Chirurgical Transactions in 1840.   At the root of the lungs
four pulmonary veins result, which forthwith discharge their torrent
of arterialized blood into the left auricle of the heart.
   The cause of the separate course of the pulmonary arteries and
veins is to be found in the opposite position of their radicles, in re-
gard to the capillary network  of the  lobules, it being a convenient
arrangement for the terminal arterial and venous twigs to hold alter-
nate positions among  the capillary network, so  that each arterial
twig disperses its  blood  in all directions, and  each venous  radicle
collects it from  all sides.  An obvious analogy exists  in  respect  of
the course of the vessels and ducts between the liver and lungs, the
bile-ducts answering to the air-passages, the hepatic artery  to the
bronchial  arteries,  the vena porta to  the pulmonary artery, the
hepatic  vein to  the pulmonary vein.   The nerves  and lymphatics
pass in both cases with the ducts.
   The capillary network of the lungs lies on and in the walls  of the
air-cells and lobular  passages.   These walls are  for  the most part
much too  thin to inclose the capillaries between two layers of their
substance,  and  therefore  the capillaries project fairly into the air-
cells,  by a great part of their  circumference, being adherent to the
wall by a narrow line only.  The capillary wall is thus exposed and
bare in  contact with  the air  of the cell, and nothing besides the
delicate membrane  of the capillary intervenes between the air and
the blood.   A capillary frequently passes through  an aperture in the
       46 
714
RESPIRATION.
cell-wall, so as to project first  into  one  cell, and further  on into a
contiguous  one, but never becomes altogether free from the wall. In
passing, its A\Tall is blended with that of the cell.   The nuclei seen
in the capillary walls elsewhere are very  conspicuous in those of  the
lungs.     \
   The best way of proving the arrangement of the capillaries is by
injecting a  lung with size by  the  pulmonary artery till the  blood-
vessels and the air-cells are both filled, the  latter by transudation,
and then slicing it when cold.   The capillary wall is  then  seen to
be uncovered by any tissue, just  as  is usual in the Malpighian tufts
of the kidney.   The diameter of the capillaries is about  yg1^ of an
inch, which  is large, and the  blood therefore  passes freely.   The
meshes of the network  are not  much wider than the vessels them-
selves.
   Mr. Rainey says that, on the surface  of the  lung, the  capillary

                              Fig. 207.
 View of a thin section of the lung of a cat, which had been injected by the pulmonary artery with
gelatine, so as to fill bloodvessels and air-cells, and had been sliced when cold,  a a a. Air-cells and lobu-
lar passage in section.  6 6. Their wall in section,  c. Their wall in face. d. Extremely faint nucleus in
the same,  e e. Capillaries, h. Nucleus in wall of capiUary.  n. Small pulmonary artery or vein with
simple wall. Magnified 250 diameters.

network extends over a space corresponding to not more  than ten or
twelve cells, i. e.  over from one-thirtieth to one-twentieth of an inch,
and if the rate of the blood be taken at  an inch and three-quarters
per minute, according to the estimate of Valentin, drawn from ob-
servation of the frog's foot, the blood would be somewhere about one
second and a half in contact with the air at each circuit.  But pro-
bably  in the higher animals its transit  is more rapid.
   We may here refer to some very interesting observations on the 
ANATOMY OF THE LUNG.
715
arrangement of the capillaries and terminal air-passages, lately made
by Mr. Rainey.   This careful and  accurate anatomist was the first
to insist on the fact that, in mammalia and birds at least, the capil-
laries are, as we have above noticed, bare ; exposed on their exterior
to the air, not covered by any membrane, either mucous or  serous,
or by any epithelium ;  and that by this arrangement the most  perfect
aeration of the blood which traverses them is provided for. The air
and the  blood may be said  to  be  in contact  through the delicate
capillary wall, a film  less  than ■,„„„„ of  an inch  in  thickness.   In
some of the mammalia, as  the kangaroo, the rat, and the mouse, the
terminal air-spaces are too minute to  contain even  a  single particle
of epithelium, and cannot  therefore be lined by a pavement of such
particles.   The  elastic tissue described as forming the  cell-wall in
the human lung is in such instances very imperfect,  being deficient
in the areolae of the vascular network, so  as to  render the  cell-walls
cribriform,  or  rather  to reduce the terminal  air-receptacles  into a
congeries of inosculating and most minute and irregular passages.
   In the bird's lung, the elastic tissue, according to the same anato-
mist, is  even more scanty.   The  mucous  membrane  lining  the
bronchia ceases  at the commencement of the lobular passages, and
these passages seem hollowed out in the substance of a  solid capil-
lary plexus, or one in which  the capillaries extend and anastomose
indifferently in all directions.   This  vascular plexus  forms the only
wall  of  these passages, and the
air has access  from the passages
into the interstices of  the plexus,
so as everywhere to surround and
touch the whole  surface of every
capillary.   Instead, therefore,  of
the terminal air-spaces being cells
with a plane network  of  capilla-
ries  on  their walls, they are the
mere interstices  of a solid vascu-
lar plexus.   Thus, a  more  abund-
ant intermixture of the blood and
air is secured, and the ultimate
tissue of the lung is reduced to the
simple  capillary wall, arranged
so that air has access  to its exte-
rior.   The adhesion  of the lungs
to  the  costal surface, and the
support  afforded by the  cartila-
ginous and  other tissues  of the
bronchial tubes,  as well as by the
areolar tissue  bounding the elon-
gated lobules,  are  sufficient  to
maintain the  integrity of  so frail a web.   The aerial  interstices of
the vascular plexus are usually even smaller  in diameter  than the
capillaries themselves, and, according  to  Mr.  Rainey, average v^^
 Slightly oblique section through a bronchial
tube, showing at a the cavity of the tube. b. Its
lining membrane, containing bloodvessels with
large areolae, c, c. Perforations in this membrane,
where it ceases at the orifices of the lobular pas-
sages, d, d.  e,  e. Spaces between contiguous lo-
bules, containing the terminal pulmonary arteries
and veins supplying the capillary plexus, /,/, to
the meshes of which the air gains access by the
lobular passages. 
716
RESPIRATION.
of  an inch.   The above Fig.  (208) is from Mr. Rainey's paper, and
is drawn from the lung of the fowl, highly magnified.

  The gradations of perfection in the respiratory surface, considered as to its minute
organization in Reptiles, Mammalia,  and Birds, may be thus recapitulated:—
  In Reptiles the cells are large and few.  The air  has access to  the respiratory ca-
pillaries only on one surface, viz., that towards the cavity of the cell which they line;
and where two cells are  contiguous, but separated by a septum, the septum has a
capillary web on each of its surfaces.
  In Mammalia, for the most part, the cells are  much multiplied, and where two lie
side by side, the septum between them has but one  layer of capillaries, which is, in a
great measure, common to them both, and aerated on both its surfaces.  And here
we may remark the reason of the non-isolation of the lobules by areolar tissue in the
mammalian lung, except  at the borders and thinner parts, where  such isolation is
necessary for the movements of the lung in respiration.  AVhen the lobules are thus
isolated, the capillaries on the cell-walls which bound the lobule can have air only on
that surface which is towards the cavity of the cells; whereas, when the contiguous
lobules are blended by the fusion of the cell-walls which  form their exterior, these
cell-walls, like the rest, contain but  a single respiratory plexus, which is aerated on
both its surfaces.
  In Birds the respiratory capillary plexus is rendered the most perfect possible, both
by the omission of the elastic supporting tissue, and also by the vascular plexus being
n6 longer  lamellar, but solid, or extended alike in all directions.  It is manifest that
by this arrangement a given pulmonary space is made to contain the greatest possible
quantity of capillary wall, and that this wall is exposed most completely to the action
of the air admitted around it.

   Movements of Respiration.—The thorax is a movable framework
composed of a nearly fixed column, the  dorsal spine,  on which  are
movably articulated twenty-four  ribs, curved  and inclined so as  to
embrace a large conical space, and  ending in  cartilages, which, with
three exceptions on each side  (the  floating  ribs), are  joined in front
through the  medium  of a flat  piece, the sternum, the inclination  of
which is  downwards and forwards.   The  upper  orifice, embraced  by
the vertebral column, first ribs and  sternum, is closed by a fascia of
dense areolar tissue, rendered extremely irregular by the apices of
the  lungs rising slightly  into the  neck,  and by the various struc-
tures—the  oesophagus,  trachea, great bloodvessels, muscular  and
other parts—that pass through it.    The  lower  orifice,  which is very
much  larger, is closed by the diaphragm, an  arched and  sloping
musculo-tendinous septum between the thorax and abdomen, through
which pass the inferior  vena  cava, the aorta,  and great absorbent
trunk, as well as the  oesophagus  and the  pneumogastric and sympa-
thetic nerves.   Between the ribs are placed the two layers of inter-
costal muscles with oblique fibres oppositely crossing, and  chiefly  on
the exterior  of  the bony  framework are added  other  muscles, which
may enlarge  or diminish  the  area  of  the cavity, and thus  act  in
respiration, but which are,  for the  most part,  subservient to the
general  muscular movements of the body.
   The thorax is capable of enlargement in  all its  dimensions;  in
height, depth, width.   Its vertical extent is increased  by the eleva-
tion of the ribs and the widening of the intercostal spaces*, but chiefly
by the descent  of the  diaphragm.    Its antero-posterior and trans-
verse  diameters are  increased  by the  elevation of the ribs, which 
MOVEMENTS OF RESPIRATION.
717
Fig. 209.
carry forwards as well as raise the  sternum (and  the  lower end of
that bone usually a little more than the upper, in consequence of the
greater length  and obliquity of the lower  sternal  ribs), and which
also seem to undergo a slight rotation  on a line joining their two
extremities, by  which  their  middle  part  is raised and slightly re-
moved from the median plane of the thorax.  These are the princi-
pal modes provided in the mechanism of the thoracic walk for its
dilatation in breathing.  It should be added that during the advance
of the sternum  the arch of the ribs is Avidened, chiefly by a torsion
of their cartilages, and that  the elastic rebound of those parts is a
powerful agent in expiration.
   Observed Movements.—All the  foregoing modes of  enlargement
of the thorax act in deep inspiration, but in  ordinary breathing there
are  considerable  differences
according  to sex and age.
In men, an ordinary inspira-
tion  is  attended  with very
slight elevation  of the ribs,
not more than  one-twentieth
of an inch, according  to Dr.
Hutchinson's   observations;
whereas,  in  women,   this
movement is very  obvious,
particularly in the upper ribs.
It is not improbable that the
cause of this may lie  in the
narrower waist of the female,
obliging an  undue enlarge-
ment of  the upper  part  of
the thorax to compensate for
the smaller size and less dila-
tability  of  the  ample  base.
The separation  of the  ribs
and widening of the intercos-
tal spaces when  the  chest is
enlarged, are proved by mea-
surement both  in  the  living
and dead.  Dr. Hutchinson
has made casts of the interior
under both  states.  Dr. Sib-
son divides the ribs into three
sets:  a  superior  set of five,
separately joining the ster-
num; an intermediate set of
three  with   conjoint   carti-
lages ; and an inferior or diaphragmatic set  of four  with floating car-
tilages.   He considers that all, except the upper four in their front
part, diverge from one another in inspiration,  the  inferior set the
most, but the lowest of all remaining stationary.  Messrs. Beau and
  Diagrams showing the extent  of antero-posterior
movement in ordinary and forced  respiration in male
and female. " The back is supposed to be fixed in order
to throw forward the movement as much as possible."
The black line indicates, by its two margins, the limits
of ordinary inspiration and expiration. In forced inspi-
ration, the body comes up to the dotted  line, while in
forced expiration, it recedes to the  smallest space indi-
cated. From Dr. Hutchinson. 
718
RESPIRATION.
Maissiat* describe three varieties of ordinary respiration: 1. Ab-
dominal, or that chiefly effected by the diaphragm and  apparent in
the motion  of  the abdominal walls.   This occurs in infants  up to
the end of the third year, and in males generally.  2. Costo-inferior,
or that in which the  lower  ribs (those of Mr.  Sibson's intermediate
and inferior sets) are  observed to act.   This is observed in boys after
three, and  in men.  3. Costo-superior, or that  effected  in  a con-
siderable  degree by the upper  ribs.   This is observed in females,
especially in adults.
  Action of Muscles.—The diaphragm has an arched form, is highest
in front, lowest behind.  The fibres pass to a central tendon on which
is seated the heart in the pericardium, the lungs resting  chiefly on
the muscular parts.   Its contraction would tighten and then depress
both the central tendon and the muscle  generally, and would also
tend to straighten the curve formed by the fibres as they pass from
the spine and ribs to  the central tendon.   Thus the heart would be
lowered a little, but,  perhaps, the lungs more, and the area of  the
pulmonary compartments of the thorax would be much enlarged, for
the diaphragm  acts at their wide  and ample base, Avhere a  slight
range of vertical movement produces a great effect.  In its descent,
the diaphragm presses down the abdominal viscera, and  bulges  the
abdominal walls.  In expiration,  it recedes upwards, being pushed
upon  by  the abdominal walls through the medium of the viscera.
  The action of the intercostal muscles is less obvious, and had been
the subject of much difference of opinion, even before  the days of
Haller.  It may be studied  on  mechanical principles, and by obser-
vation.   Hambergerf has given the  most elaborate  and complete
exposition of the mechanical view of  the subject, and has illustrated
it with diagrams and  models.  He shows  that if two parallel bars
(ribs) slope  downward from a fixed vertical column (spine) to Avhich
they  are  separately  articulated (heads  of the ribs)  and are kept
separate  at their opposite ends (as by the  sternum), then a contrac-
tile force (muscle) acting  between them, will  raise  or depress both
bars,  according to the direction of its obliquity.  If the contractile
cord slope downward from the column representing the spine (exter-
nal intercostal fibres), the bars will both be elevated by its contrac-
tion, and will carry upwards the sternal element.   As they rise, the
cord is seen to shorten.
  If on the other hand the contractile cord slope downwards towards
the vertical column (internal intercostal fibres), then the  bars will be
both depressed by its  contraction.   It is obvious that the space be-
tween the bars  will be widened  as they rise towards  the horizontal
line, and narrowed as they fall.   Hence it  seems clear,  without
entering upon the mechanical theorems by which the above results
may be proved,  that  the action of the external and internal inter-
costals must be antagonistic.  That  the  former  must elevate and

            * Archiv. Gen. de He'd. t. xv. p. 399.
            f Physiologia Medica, Jenae, 1751, 4to. p. 140, et seq. 
ACTION OF THE INTERCOSTALS.
719
open out the ribs, the latter depress and approximate them—that, as
the fibres of the one are shortened, those of the other must of neces-
sity be lengthened.                            •.
  It is true that the ribs are curved,  and variously flexible, instead
of straight and stiff; that their articulations differ from one another,
and are  nowhere purely ginglymoid, and  that other forces besides
the intercostal muscles influence their movements.
  These considerations,  however, do not seem to  affect the substan-
tial accuracy of Hamberger's views, so far as relates to the greater
number of the ribs, and  indeed to all in the posterior region.   And
Dr. Hutchinson has  done well to call attention  to them and to  illus-
trate them by new researches.   But  Dr.  Sibson has shown by ob-
servations both in man and animals, and in the latter especially, by
a series  of careful  experiments upon  the  actual movements of the
thoracic walls and their  muscles,  exposed during life, that the exter-
nal intercostals are not everywhere inspiratory, nor the internal ones
expiratory.   For, in the upper  two  or three  spaces in front, the in-
ternal, as  well as the external  intercostal fibres, contract and ap-
proximate the ribs.   Those  fibres, also of the internal intercostals,
which pass between the cartilages of the ribs, contract during inspira-
tion, and correspond with the internal intercostals of the sternal ribs
of birds, which are poAverfully inspiratory, and  slope downwards and
backwards from the sternum.   These may  have their action explained
by Hamberger's  vieAVS,  if the  sternum be regarded as  giving the
fulcrum instead of the vertebral column.   Again, the lowest external
intercostal lengthens in inspiration, and is an expiratory muscle, the
eleventh  rib  in inspiration  rising from the twelfth, which is sta-
tionary.*
   On the whole we may conclude, that in  inspiration, the upper ribs
rise by the action, of the scaleni—that  the rest of the ribs in  their
hinder part  rise and open out by the  action chiefly  of the external
intercostals ;  while in front the intercostal  spaces  are narrowed above
by the rise of the second, third, and fourth ribs towards the first, and
at the same time widened midway and below,  the flexibility of the
costal cartilages having  much to  do  with this  latter  movement.  It
may, also, be regarded as  certain that  the internal intercostals,
except  in front, are muscles of expiration, and  approximate the
ribs.

  * On February 26, 1851, Dr. Sibson exposed the intercostal muscles in a dog under
chloroform, when we noted the following as facts: 1. The lower fibres of the serratus
magnus contract during inspiration;  the upper fibres lengthen.  2. The first  five
intercostal spaces diminish decreasingly during inspiration.  3. The seventh, eighth,
and ninth ribs  diverge increasingly from the seventh to the ninth, and the  tenth,
eleventh, and twelfth in a less degree.  4.  The twelfth rib is stationary.  5. The
first external intercostal muscle shortens, the  lowest lengthens, during inspiration.
6.  The first and second internal intercostal muscles, in front, shorten during inspira-
tion ; the third,  also, in a very slight degree.   7. The sixth internal intercostal elon-
gates during inspiration, and the ninth also, but in a greater degree. 8. The eleventh
anterior external intercostal of the diaphragmatic ribs shortens during inspiration.  9.
Behind, the tenth external intercostal shortens, the  tenth internal lengthens, during
inspiration. 
720
RESPIRATION.
  Dr.  Sibson has well pointed out that the forces which expand the
thorax act, in a great degree, in a separate and independent manner on
its several parts; that the lower region, and the lower lobes of the
lungs Avhich fill it, are enlarged by the diaphragm and lower external
intercostals, while the upper region expands  under the influence of
the scaleni, its external intercostals, and (in front) its  internal inter-
costals.  A variety of morbid conditions of the lungs, where the ex-
pansibility of one or more lobes is modified, illustrates this observa-
tion, for one  side of  the  chest may be observed  to expand without
the other, or a portion of one side without  the rest.  Hoav important
this amount of independence of the parts of the chest is to the pre-
servation  of  life,  under  accident or  disease,  needs  hardly  be ex-
plained.
  In addition to the muscles now mentioned, the levatores costarum,
cervicalis  ascendens, and serratus posticus superior  are probably
muscles of ordinary inspiration; and  those of the  abdominal wall,
with the levator ani, of expiration;  the latter  action being aided by
the elasticity of  the ribs  and their  cartilages, and by the resilience
of the elastic tissue entering  so largely into the composition of the
lungs themselves.   This resilience (which  Dr. Carson showed to be
sufficient in sheep and dogs to balance a column of water from one
to one foot and a half in  height) occasions the collapse of the lungs
when the pleural cavity is  accidentally opened, as  sometimes by
wound of  the parietes.   In such  cases  the air passes  in and out of
the thorax through  the wound in respiration, and the  air previously
in the  lung is expelled through the glottis by the elastic force of the
pleura and walls of  the  air-passages  and cells.  If  the lung also
be wounded, the air may pass into the pleural  sac  from the  air-
passages under  the same  resilient force, and  be thence pumped by
the expiratory forces through the wound  in  the parietes  into the
areolar tissue of the body, as so  often  happens in the case of frac-
tures of the ribs.
  Extraordinary Muscles of Respiration.—In voluntary deep breath-
ing,  or when (as in asthma) the  head, neck, and  upper  extremities
become fixed points for the muscles passing  between them and the
thorax, the lower part of the serratus magnus, the pectorales, the
subclavii, with the sterno-mastoidei, trapezii, and some others, aid in
dilating the  chest.   Some difference  exists among the most recent
authors as to the share particular  muscles  take in the movements of
respiration; and this  is not surprising when we consider the  com-
plexity of the problem, the difficulty of determining  the fixed  points,
or of observing the  muscles in separate action.  In forced expiration,
the triangulares sterni, the serrati postici  inferiores, sacro-lumbales,
latissimi dorsi, Avith their accessories  as high  as  the  highest costal
insertion, probably  help to depress and approximate  the ribs.
  Power  of  the  Respiratory Muscles.—Dr. Hutchinson has lately
made numerous experiments on this subject, and his results and those
of Valentin and Mendelssohn agree.   He finds as the  average of
1,500  trials that the  expiratory power exceeds the inspiratory by 
EXCITATION OF RESPIRATORY MOVEMENTS.        721
one-third;  that men of 5 feet 7 or 8 inches  have the greatest inspi-
ratory power, and should on an  average raise a column of mercury
three inches; while, above this, the strength gradually decreases as
the stature increases, so that a man of 6 feet raises a column of only two
inches and a half:  also, that occupation or mode of life serves much
to modify  the  relation which the  inspiratory and expiratory powers
bear to each other.  Thus, wrestlers, boxers, and others, accustomed
to employ  the extraordinary muscles of respiration, in rendering the
thorax a fixed point from which other muscles might act, were found
to have an unusual power  of expiration.  In one wrestler he found
the expiratory power exceed nearly four times that of the  natural
inspiratory power.  Valentin,  in six experiments  on  young  adult
males, found the force exerted  in ordinary, tranquil inspiration and
expiration  to be from about one-seventh to three-sevenths of an inch
of mercury.  Dr. Hutchinson calculates that a man who raises three
inches of mercury by an effort of inspiration exerts  a force equal
to 1,000 lbs.  In one man he found the mercury raised  to  such a
height (seven inches) as  to indicate a force  of 2,200 lbs., or nearly
a ton.
   When the  capacity of the thorax is augmented, the air in the lungs
expands so as to keep them in  contact with the walls, and the ex-
ternal air enters by the trachea to restore the  equilibrium.   When
the dilating  force  ceases, the walls of the chest  contract upon the
lungs, and  expel a  portion of the air, the lungs themselves conspir-
ing.
   Use of the Ttachealis Muscle.—That the trachealis in contracting
must  diminish the area of the trachea  and bronchia is obvious from
its arrangement no less than from experiment.  Dr. Williams found
that the lungs taken from an animal just killed manifestly contracted
under the stimulus of  galvanism.   The fibres are allied to those of
the ducts of  glands, and of the bloodvessels, and  are consequently
probably incapable of coinciding in action with the muscles of respi-
ration.   It further seems  impossible to assign  an object  to  any
peristaltic  action which might be  attributed  to  them.   We  are dis-
posed to consider that the trachealis muscle contracts and dilates the
air-tubes slowly, in relation to  the activity of the respiratory func-
tion at different times of the day, or under other  modifying  circum-
stances.  Its contraction  would  tend to limit  the quantity of air
transmitted in a given time, or would quicken its passage.  It  is in
all probability contracted spasmodically in spasmodic asthma, and in
the early stages of bronchitis.  If it contracts  during the sensation
that precedes and  accompanies coughing, this  would facilitate the
expulsion of mucus by quickening the expelled current of air.
  Excitation of the Respiratory Movements.—We have already re-
ferred to the share taken  by the nerves in respiration.  The respi-
ratory acts are essentially involuntary, and unconsciously performed,
although we have a limited power of checking or  accelerating them,
of varying  their rhythm or force, and can become aware of them by
an effort of attention.  After holding the breath for fifteen  or twenty 
722
RESPIRATION.
seconds during ordinary respiration, or forty seconds  after a  deep
inspiration, there arises an  insupportable sensation  over the whole
chest, concentrated under the sternum, and  no effort can maintain
the interruption of  the  respiratory acts.  This  urgent sensation of
want of breath, when carried to  its full  extent by  any mechanical
impediment to the aeration of the blood,  is one of the most painful
and oppressive kind, and is referable to the pulmonary plexuses dis-
tributed on the bronchia, and perhaps on the walls of  the lobular
passages and cells.   The impression made on  these peripheral nerves
by the absence of oxygen, and the undue presence of carbonic acid
in the air in contact with them, is propagated to the  spinal cord and
medulla oblongata by the  sympathetic and vagus, and there excites
those  combined actions of the muscles of inspiration which lead to
the renewal of the air; and it may  be  fairly concluded that the
ordinary motions  of respiration depend on the same circle of nervous
actions, which  thus, voluntarily arrested,  become apparent by  their
accumulated force!   The muscular actions of expiration,  which  seem
to follow so  evenly on those of inspiration, are  probably due, in
part at least, to the stimulus of elongation of their fibres.  When
the ribs  diverge, the fibres of the' internal  intercostals, except in
front, are extended.
  Frequency of Respirations and Ratio to the Pulse.—The number
of respirations per  minute  in healthy adults is from eighteen to
twenty;  but, according to Dr. Hutchinson's observations on  more
than 1,700 persons (Avhen sitting), the range in health may be from
six to forty, though most  persons  breathe from sixteen to twenty-
four times per minute.  The proportion which the respirations bear
to the beats of the heart is liable to much variation, but is in general
not far from  that  of one to four.  Dr. Guy has  shown that the
respirations are rather  more frequent in the  evening than in the
morning, whereas the pulse is rather sloAver.   He has also discovered
that the proportion betAveen the  respirations  and pulsations is much
deranged by changes of posture, probably  by these modifying the
expansion of  the lungs at  each inspiration, without  inducing any
corresponding change in the transmission of  the blood.
  Aerial Capacity  of the Lungs, and Amount of Air Breathed.—
When the lungs have been emptied as much  as possible of air, by a
forced expiration, they still  contain a residual  quantity, which may
be estimated at  about forty cubic  inches.   The mechanical condi-
tions under which the organs are placed do not allow of  their expel-
ling this remnant.  If, now, the deepest possible inspiration be taken,
it is found that they are capable of inhaling a further quantity,  vary-
ing much in different persons, but  on an average about 240  cubic
inches, which, with the former residual quantity, make a sum of 280
cubic inches as the full  capacity of the lungs of a person of  good
height (5 feet  8 inches).   But in ordinary breathing, the lungs are
neither very empty nor very full—they maintain a middle condition,
and their range of movement in natural or ordinary respiration  is
only sufficient to  pump in and out a quantity of air equal to about 
CHANGES IN RESPIRED AIR.
723
80 cubic inches.  From the best observations, it may be concluded
that a person whose full capacity is 280 cubic inches, contains in his
lungs, after an ordinary  expiration, about 110 cubic inches;  and
after an ordinary  inspiration, about 140  cubic inches, a quantity
which he is  enabled to double by a full  inspiration.   Thus rather
more than one-fifth of the ordinary contents of the lungs are expelled
at each expiration,  and again  renewed by inspiration.
   Dr. Hutchinson,  by means of a gasometer, which he terms a spiro-,
meter, has  examined  a large  number of persons with reference to
their power of  taking air  into  the lungs.   The  person first inspires
to the full extent, and then breathes into the instrument as much air
as he can, and  it results that the height of the individuals has much
to do Avith their respiratory  range.   Thus, while on an average a
person of 5 feet breathes  174 cubic inches,  one  of 5 feet 1 inch will
breathe 182 cubic inches,  and for every inch of height up to 6 feet,
will breathe about 8 cubic inches additional.  Weight has much less
influence than  height, but tends to  diminish  the respiratory power
when beyond  a certain limit.  In males  of  the same height, the
respiratory range (vital capacity of Hutchinson) increases from 15
to 35 years of  age; but from  35 to 65 it  decreases nearly 1J cubic
inches per  year.  Bourgery agrees  nearly  with this: he states  that
more air can be inspired at thirty than at any other age, and that in
old persons the range is  very limited.  Bourgery calculates that a
child of ten years of age, with  a weight three  times  less than  that
of a man of eighty, has  a respiratory power eight times greater.
This is due to the great difference there is in the range of the respi-
ratory movements.   The old man being able to increase the amount
breathed by less than a half, while the child may increase it nearly
fourteenfold.   Herbst has shown that the  capacity of the lungs is
much smaller in the female than in the male.
   Having  now considered the  anatomy  of the respiratory organs,
and the movements which regulate the supply  of air, we may proceed
to consider the changes which  occur  in the air  during its sojourn in
contact with the respiratory, surface, and also the  corresponding
changes in the blood  circulated there.
   Changes in  the Respired Air.—The air consists  of a mixture of
oxygen and nitrogen, in  the  respective proportions  of about 20.81
and 79.19 in 100 parts by volume, with the  addition of a very minute
portion of  carbonic acid  gas, not  exceeding  one part by volume in
2,000.  It contains watery vapour in variable quantity, according to
temperature and other circumstances ; and also non-estimable quan-
tities of other  gaseous and volatile substances, of no account in re-
lation to the respiratory  function.  In air that has been breathed,
the  temperature is  found to have assumed nearly or quite that of the
blood, the  quantity of moisture has nearly reached the point of satu-
ration, the proportion of oxygen has diminished, and that of carbonic
acid has increased, while  that of nitrogen has slightly increased, or
has undergone little  change.  A small  quantity of  animal matter
has also been  received from the air-passages, as is  proved by the 
724
RESPIRATION.
brown colour assumed by sulphuric acid, through  which the respired
air is made to pass.
  Aqueous Vapour Exhaled.—It results from the most careful expe-
riments, amongst which  may be  mentioned  those  of Valentin  and
Brunner, and of Moleschott, that  the  air expired is usually nearly
saturated with moisture, and that the quantity of Avater thus escaping
from the system in twenty-four hours, may be estimated in temperate
climates at from tAvelve to twenty ounces.  It is,  of  course, impossi-
ble to ascertain, nor is it important, how  much  of this quantity is
derived  from the  respiratory surface, strictly so  called,  and  how
much from the moist and vascular  surfaces  of the nasal, pharyngeal,
and bronchial passages.
  Exhalation of Carbonic Acid by the Lungs.—It  is easy to show
that  carbonic acid  gas is exhaled from  the lungs, by breathing  into
lime-water, which thus becomes turbid  by the formation of insoluble
carbonate of  lime ; or into  a phial, whejje a taper is  then at once
extinguished.
  In 100  parts by volume of expired  air (as  an average of many
experiments),
                                           Carbonic Acid.
               Coathupe  .     found .   .    .  4.02.
               Valentin and \     ti              a no
               Brunner   . /
               Vierordt   .       "   .   .    .4.33.
               Thomson  .       "              4.16.

  The general average of the results of Valentin and Brunner, and
Vierordt, all  of which were  performed  on adult males, may be ac-
cepted for that age and sex, viz.: 4.35 parts  of carbonic acid in 100
parts of  expired  air;  or deducting  the small  quantity  of carbonic
acid  contained  in the air when inspired, we may  conclude  that 4.30
parts per cent, by volume of that gas  are derived from the lungs at
each ordinary expiration.   Taking, as  before, 30  cubic inches as the
volume of each expiration, the actual  quantity of  carbonic  acid in
each will be 1.29 cubic inches= about 23 cubic  inches  per  minute=
about 1,393 cubic  inches  per hour=about 27,864  cubic  inches, or
16.1 cubic feet per day.  In  this  last quantity of carbonic acid,
there are about seven and a half ounces by weight of carbon.
  A  great variety of circumstances no doubt modify the activity
with Avhich  carbonic  acid is formed in  the  system, and eliminated
from  it;  some of  these  are  very Avorthy of notice.  Digestion  has
been observed to be attended with an  increased exhalation of it in
many of  the  lower animals;  and Scharling,  Valentin, and Vierordt
have recently noted the same fact with great accuracy in Man.  Thus,
one  hour after a  midday meal, Vierordt found  that his  pulse was
quickened by 15, his respiration by 1,  the volume of the expired air
was slightly increased, nearly 50 per cent,  more of air, and 2J cubic
inches more  of carbonic acid Avere expired in  one  minute, and the
percentage of carbonic acid in the expired air was also augmented
in a  very trifling degree.   If the  meal  were omitted, these results 
EXHALATION OF CARBONIC ACID.
725
did not occur.   On the other hand, fasting, especially if  prolonged,
diminishes the exhalation.
  Particular substances taken into the blood exert a very remarkable
influence upon the development of carbonic acid in the system.  Dr.
Prout long since observed  a considerable diminution under alcohol,
particularly if taken on an empty stomach; and his conclusions have
been  fully confirmed by Vierordt  and Bocker.   The former found
that, having taken more than half a bottle  of wine, the carbonic acid
fell in a quarter of an  hour from 4.54 to  4.01 per cent,  of  the  ex-
pired air;  i. e.,  by about one-ninth of its whole quantity; and this
lasted for two hours.  In  addition to this, the  latter author found
that, under the  same influence, the Avhole  constituents  of the urine
are diminished in amount.   Dr. Prout states that a dose of strong tea
likewise lessens  the exhalation of carbonic acid.
  Since the introduction of ether and chloroform as  anaesthetics in
the practice of surgery, their mode of action has been much inves-
tigated, and by no one more extensively or more accurately than by
Dr. Snow, who has, among other matters, turned his attention to the
amount of carbonic acid gas passing from the lungs under their use.
A small animal being placed in a jar, in which  the air could be  cir-
culated in connection with  a receptacle containing solution of potash,
for  absorbing the carbonic  acid,  the quantity of this gas  expired
during  periods of half an  hour  Avas  estimated, when the   animal
breathed firstly air, and afterwards air mixed with certain quantities
of the vapour of chloroform.  The results were such as  the follow-
ing : A dog,  eight pounds in weight, exhaled in  air 10.1 grains of
carbonic acid gas; in air mingled with 36 grains  of  chloroform  va-
pour,  only 4.8 grains.  A half-grown cat expired in air 5.7 grains
of carbonic acid gas; in air mingled with 20 grains of  chloroform
vapour, only 2.0 grains.  And this  diminution was observed, on this
and other occasions,  to  be  in spite of increased muscular efforts on
the first introduction of the  chloroform, such as  are  known to have
a tendency to augment the excretion of carbonic acid.
  Exercise increases the exhalation of carbonic acid, and doubtless
also the formation of it in  the tissues.  Mr. Newport observed  that
the generation of carbonic acid  from  bees,  when at  rest, did  not
exceed that from cold-blooded animals; but Avhen in active  movement,
it was more energetic than in any other  animals;  and other  experi-
menters have produced analogous results.   With more precision, and
in the case of the human  adult, Vierordt  shows that, during mode-
rate exercise, there is an  average  increase per minute of 19 cubic
inches in the expired air, and of 1 cubic inch  in the expired carbonic
acid.
  The temperature of the surrounding medium was shown by Seguin
and Lavoisier to have an  important influence on  the exhalation of
carbonic acid, and their results were corroborated by those of Craw-
ford.   Vierordt  has recently examined this point also.   In numerous
experiments upon himself,  at temperatures  of which the average was
47° Fahrenheit, he expired 18.25  cubic inches of carbonic acid per
       47 
726
RESPIRATION.
minute ;  while at temperatures of which the average was 67° Fah-
renheit, he expired only 15.72 cubic inches in the same period.  At
the lower temperature, the number of respirations was  increased,
and more air was expired in the proportion of 406 to 366, or about
10 to 9.   Cold, therefore, contrary to what might have been expected
from its depressing  effects on the  system, is attended  with an aug-
mented exhalation of carbonic acid, and, as will be  afterwards seen,
with an  increased development of animal  heat.   Of course there
must be limits to this result.
  MM. Andral and  Gavarret have  arrived  at some remarkable re-
sults  regarding  the  influence of sex and age on  the  exhalation of
carbonic  acid.  They found that, after the age of eight  years, the
male exhales much more than the female, the average quantity be-
tween the ages of 16 and 40 being double in the  male.   With re-
spect to each sex  at different ages, the  male child between 8  and 15
exhales per hour, in  the form of carbonic acid gas,  77 grains of car-
bon ;  the female about 15 grains  less.  In the male, the quantity
increases rather suddenly at puberty to 157  grains, and continues
increasing up to 25, when it  averages 191 grains  per hour (or 9|
ounces per day).  It remains about stationary up to 40 years of age;
between 40  and 60,  it averages only 155  grains ;  and between 60
and 80, 141 grains per hour.   In one man of 102,  remarkably hale,
it was only 91 grains ; in  another of 26, remarkably fine and mus-
cular, it reached 217  grains.  In the female, no great or correspond-
ing increase takes place at puberty ; and as long as menstruation is
regular, the  average  exhalation  of carbon is only 98 grains per hour.
During pregnancy, however, and also at the period of the cessation
of the menses, it is singular to  observe that this quantity is quickly
raised to 129 grains.   Between 50 and 60, the average is 112 grains;
between 60  and 80,  104 grains.  In a woman of 82 it was only 92
grains per hour.  Scharling has, to some  extent, corroborated these
results.
  This increase in the male during the period of the greatest activity
and muscular vigour, and also  the general higher  standard in the
male, and the decline of both sexes with age, is accordant with what
we know of  the rate  and activity of the changes of nutrition under
these several conditions.   The varieties in the female are less easily
explained, though obviously of great importance.  It may be here
remarked, that Hutchinson and Bourgery have ascertained that the
quantity of  air breathed increases up to 30 or 35 years of  age, then
decreases  slowly to 65, and very much in old age;  and also that it
is less in females.
  Such are some natural circumstances  modifying the  quantity of
carbonic acid exhaled.   The following  conclusions of Vierordt on
the influence  of the  respiratory movements  on the  amount  expired
are interesting in themselves, and throw  light on  the  theory of
the respiratory function.   He finds that, when the respirations are
increased in frequency,  more  carbonic acid  is  exhaled,  although,
from  the much larger  quantity of air breathed, the percentage of 
INHALATION OF OXYGEN.
727
carbonic acid in  the expired air  is less.  Thus the percentage of
this gas bears a certain proportion to  the  frequency of the respira-
tions, supposing their bulk to remain the same.
  If the respiratory movements are suspended for a short time, the
percentage of  carbonic acid in the expired air becomes increased.
The  total quantity  expired  is, on the other hand, somewhat  dimi-
nished ; showing that this increased percentage, in a given quantity
of air, does not compensate for the smaller  proportion of air entering
the lungs under these circumstances.
   Allen and Pepys found, that when the same  air was breathed
more than once, the proportion  of carbonic acid  underwent a con-
siderable increase.   Air breathed nine or ten times, contained 9.5
per cent,  of  carbonic acid;  but if  the air was breathed over again
as often  as  possible, the percentage  of  this gas  could  not be  in-
creased above  10.   Mr. Coathupe obtained  as  much as  12.75 per
cent, of carbonic  acid  from air in which animals  had been placed
until they were suffocated.
  The percentage of carbonic acid varies also at different periods of
time during the same respiration.   By taking the average of twenty-
one experiments,  Vierordt found, that  while  the proportion  of car-
bonic acid in the  entire expiration amounted to 4.48 per cent., the
first half  contained 3.72,  and the last half 5.44  per cent.  It has
been estimated, that the air from  the  air-cells  contains as much as
5.83 per  cent, of carbonic acid, or about 1.3 per  cent, more than
the air of an ordinary expiration.
  Amount of Oxygen Inhaled.—The quantity of oxygen  introduced
into the system in respiration, is always greater than is required to
form the  amount  of carbonic acid eliminated during this process.
This  surplus quantity no doubt is employed in oxidizing other sub-
stances in the organism besides the carbon ; such, for instance, as
sulphur and  phosphorus, which  are eliminated  in  the urine in the
form of  sulphuric and phosphoric acids.  Valentin and Brunner
found  that the proportions of these gases approximated very closely
to their diffusive volumes;  for the quantities obtained by direct ex-
periment, and by calculation, differed  very slightly.  Oxygen being
the lighter gas, a larger quantity is required to  replace the carbonic
acid;  81  parts of the latter will require 95 of the former to replace
it according to Graham's law, that the diffusion volume  of different
gases varies inversely as the square root of the density, or about one
volume of absorbed oxygen corresponds to .85 of exhaled carbonic
acid.  The experiments of Dulong and Despretz,  as well  as those of
Regnault and Reiset, have, however, shown that this relation  is by
no means constant.
   From the  above considerations, it is evident  that the respiratory
changes cannot be efficiently carried on, unless  a  certain proportion
of air  be assigned to each individual living  in a confined space.   For
if the cubic  capacity of the apartment be below a certain standard,
the air becomes so contaminated by the increased  quantity of car-
bonic acid expired, as to produce a highly deleterious effect upon the
health. 
728
RESPIRATION.
   Probably between four and five hundred cubic feet of air pass
through the lungs daily, and in the same period, about twenty-three
cubic feet of oxygen gas are absorbed.   The size of an apartment,
therefore, in which persons are confined should be such, and its venti-
lation should be so arranged, that each individual may be supplied
with  the  above quantity of pure  air as  a minimum.  The cubic
capacity of such rooms should not be less than 800  cubic feet for
each  person inhabiting them.  Leblanc found, that  in  the Chamber
of Deputies in Paris, each individual was  supplied with only from 353
to 706 cubic feet of air per  hour; and in  the  air issuing from the
apartment, he found from 2  to 4 of carbonic acid  in  1000 parts by
weight.  This proportion  of fresh air was  probably too small, since
it has been found that 1 per cent, of carbonic acid  produces a dele-
terious effect upon the system  when  breathed  for a long time con-
tinuously.   In the Model Prison,  Pentonville, from 1800 to 2700
cubic feet of fresh air pass into each cell per hour.   In hospitals, the
number of patients in each ward should be so arranged, that not less
than from 800  to  1000 cubic  feet  should  be assigned to each.  In
the new King's College Hospital,  each  patient has  from 1850  to
2500 cubic feet of air.
   Dr. Snow has shown that the bad  effects of air deteriorated by
respiration, are due not only to  the increased  quantity of carbonic
acid which it contains, but  also to the diminution of its  oxygen.
From his experiments upon animals  he has been  led to conclude,
u that 5 or 6 per cent, by volume of  carbonic  acid cannot  exist  in
the air without danger to life, and that less than half  this amount
will soon be fatal, when it is formed at the expense of the oxygen
of the air."
   Exhalation of Nitrogen.—MM. Regnault and Reiset have  shown
that an extremely small quantity of nitrogen is constantly exhaled,
its proportion varying according to the nature of the food.   After
prolonged fasting, this gas, however, appears to be absorbed, instead
of being exhaled.  Barral found that the  quantity of nitrogen ex-
haled from the lungs of man, was about T£otn 0I" tne amount of car-
bonic acid removed in the  same time.   It must  also be observed, that
a very small  proportion of  nitrogen  is constantly being expired in
the form of ammonia.
   Changes in the Blood resulting from Respiration.—Dark  venous
blood in its passage through the capillary vessels of the lungs assumes
the bright red colour characteristic of  arterial blood.   This change,
as is well known, depends  upon the removal of carbonic acid gas and
the absorption of oxygen.  Magnus showed that venous blood con-
tained 25 per cent, of its volume of carbonic acid, and 5 per cent, of
oxygen;  and that arterial blood, on  the other hand, contained  as
much as 10 per cent, of its volume of oxygen, and only 23 per cent.
of carbonic acid.   The seat of this change is clearly in the red blood
corpuscles;  but its precise nature has not yet been satisfactorily de-
termined.  It has been ascribed to a chemical  change  taking place
in the coloured  constituent of the blood globule (page 640), but later
researches render it probable that it is, at least in some measure, due 
CHANGES IN THE BLOOD.
729
to a physical alteration.   Henle was the first observer who referred
the change of colour in the blood corpuscle to a change in its form.
   Scherer states that the blood corpuscles of venous blood are nearly
spherical, and their walls thin and transparent, a condition which
causes them to transmit light freely.   On the  other  hand, the cor-
puscles of arterial blood  are bi-concave, their walls thicker, and they
reflect light more  readily, which  is  considered to account for the
brighter colour  of  arterial  blood.   Harless has  even been  able to
measure the difference in size between the blood  corpuscles of arterial
and venous blood of the  frog.
   Magnus proved that serum would dissolve twice as  much carbonic
acid as an equal quantity of pure water, a power which Liebig attri-
buted to the amount of phosphate of soda contained in blood serum.
   Of the gases existing in the blood,  a very small proportion only
is in chemical combination with any of the constituents of that fluid,
but the greater quantity is held in solution in a free and uncombined
state.   This is readily proved by passing a current of hydrogen gas
through some defibrinated blood placed in  a bottle to which tubes are
adapted.  The hydrogen takes the place of  the gas previously held
in  solution  and the  latter escape;  and  by causing  them to pass
through lime-water, evidence of the presence of much carbonic acid
is at once obtained by the formation of a precipitate of carbonate of
lime.   If the carbonic acid had existed in a state of  chemical com-
bination, we should not have been able to  obtain evidence of its pre-
sence by this process.  Besides much  carbonic  acid, oxygen, and  a
little nitrogen, are held in solution  in blood.
   With reference to the  oxygen, it cannot be doubted that part is in
chemical combination with the constituents  of  the blood corpuscle,
and part in a state of simple solution.
   The chief agents in  effecting the  absorption of gases in the blood
are undoubtedly the blood corpuscles, for it has been  clearly proved
by Davy and others, that defibrinated blood  possesses  the power of
absorbing gases in a greater degree  than blood serum.  Magnus found
that blood was capable of absorbing 1J times its volume of carbonic
acid gas.
   From the researches of Professor Lehmann upon the crystallizable
contents of the blood corpuscle,  originally discovered by Otto Funke,
we are led to  conclude that the colouring matter of the blood is
chemically affected by oxygen and carbonic acid gases.
   Lehmann has shown, that if oxygen is allowed to pass through de-
fibrinated blood slowly  for  fifteen  minutes, and  is followed  by the
transmission of a current of carbonic acid for five minutes under the
influence of light, these  crystals are formed  in  larger quantity, and
more rapidly, than if the carbonic  acid is  passed  through the blood
first.   These crystals are composed of a definite chemical compound;
and there can be little doubt that the influences which the gases ex-
ert upon its crystallizing properties are of a chemical nature.*

  * For much interesting matter upon the subject of blood-crystallization, the reader
is  referred to Lehmann's  Physiological Chemistry, 1853,  translated  by  Dr. Day,
Cavendish Society, vol. iii. 
730
RESPIRATION.
  It was formerly supposed that the oxygen of the air combined
with the carbon  of  the  venous blood in the pulmonary capillaries,
and that the carbonic acid eliminated from  the  system was formed
at the pulmonary surface; but later researches have shown that this
gas exists  preformed in the blood, and is therefore only exhaled from
the fluid contained in the vessels of the lungs, a view which was first
advocated by Lagrange  and  Hassenfratz in 1791. It has been found
that animals will give up carbonic acid when  placed in  atmospheres
which do not contain any oxygen, a fact which could not be accounted
for  upon the supposition that this gas was formed by the combination
taking place in the pulmonary organ.  Again, the presence of both
free oxygen and  carbonic acid can  be  proved in the  arterial and
venous blood.   Moreover, blood may be caused to absorb, or to give
up, these gases after it has been removed from the body.
  All the tissues of the body contain a small quantity of dissolved
gases; and  carbonic  acid can  be detected  in all the animal fluids,
even in the urine.
  Frogs' muscles, carefully  deprived of nerves and vessels, will give
out carbonic acid if placed in  an atmosphere of oxygen gas, and it
has been shown by G. Liebig,  that  the  muscles continue to absorb
oxygen, and to exhale carbonic acid, as long as  their power of con-
tractility lasts, and that they retain their  contractile  power for a
much longer period in an atmosphere of oxygen gas  than in one of
hydrogen, nitrogen, etc.  The careful observations of  Lehmann upon
the respiration of insects (in which  class the air is directly carried
to the elements  of  the  tissues  by the tracheae), tend still further to
prove the truth  of this view.   We may therefore conclude, that the
oxygen of the air is carried  by the blood to  the ultimate elements of
the tissues, and  that here chemical  combination takes place and car-
bonic acid is produced; the carbonic acid being then transmitted to
the lungs  in solution in  the venous blood, and there exhaled.
   Quantity of Carbon removed from the Body.—The estimation of
the amount of carbon eliminated from the organism in a given time
is a matter of great difficulty, and the results of the  experiments of
observers present wide differences.   Allen and  Pepys calculated the
daily quantity at rather more than 11 oz. troy,  while Mr. Coathupe
estimated it at only 4.97 ounces, and Scharling  at 7.382 ounces.
   The method employed by Liebig consisted in subtracting the total
quantity of carbon in the feces and urine from that present in the
food;  the remainder represented the quantity excreted in the breath
in the form of carbonic acid.   From  these data, Liebig calculates
that an adult male, taking moderate exercise, loses  13.9 ounces of
carbon daily from the lungs and skin.  In order to convert this large
quantity of carbon into carbonic acid, 37 ounces of oxygen must be
absorbed  during the  same  period by the lungs and skin; but this
estimate is doubtless too high.   Andral and Gavarret estimated the
carbon at nine ounces.
   According to the  recent accurate investigations  of Scharling, a
powerful adult man exhales  in the course of twenty-four hours about 
THEORY OF RESPIRATION.
731
30.6 oz. of carbonic acid, which corresponds to 8.34 oz. of  carbon,
and this we may look upon as a correct estimate.
  Some very accurate experiments upon this subject have been made
by M. Barral upon himself during summer and winter.  The great
difference noticed in the quantity  of carbon  exhaled  at  different
periods of the year may, to  some extent, explain  the discrepancies
in the results  of various observers—
                                               Carbon excreted.
                  Weight of body.  Carbon in food.  In feces
                      lbs.       grs.        grs.
In Summer.....104.5     5654.1     236.2
In Winter....."       4090.0     137.4

About 10.8 oz. troy of carbon, therefore, passed off daily in the form
of carbonic acid in  winter, and 7.8 oz. in summer.  The amount of
carbon eliminated by respiration will also  be influenced  by  the
quantity and nature of the food, and by  other circumstances, which
have  been previously adverted to.
  Theory of Respiration.—By the interchange of gases in the lungs,
the venous blood becomes  of the bright scarlet colour characteristic
of arterial blood.  The oxygen and carbonic acid both  permeate the
delicate, moist, limitary membrane of the air-cells  at the same time,
but in opposite directions.
  The oxygen, having passed through the capillary walls, is held in
solution in the blood; a small part entering into chemical combina-
tion with  the  contents of the  blood  corpuscle, and to  a less degree
with some of the constituents of the serum.
  A portion  of the oxygen not improbably acts directly upon certain
substances contained in the circulating blood, and contributes to the
formation of carbonic acid.   In this way some of the elements of the
food lately introduced  into the blood may become decomposed, and
their  carbon  removed  in the form of carbonic acid.  The greater
portion of the oxygen is no doubt  carried to  the capillaries, and
much of it then leaving the blood, and passing through the capillary
walls, becomes dissolved  by the  intercellular fluid, in  obedience  to
the same  physical laws by which it was absorbed.  At the same
time,  the  carbonic acid formed in the interstices of the tissues, and
dissolved  by the fluid which moistens their ultimate elements, leaves
this latter to enter the blood, from which the oxygen has just been
removed,  and causes it to assume the  colour of venous blood.
  Here, then, are two sources of carbonic acid—one resulting from
the action of  the oxygen upon certain elements recently introduced
in the food,  giving  rise to  the production of a certain amount  of
animal heat,  and the other depending upon the  union of  the oxygen
with  the carbon of those substances which are produced in the disin-
tegration  of  tissues  during the performance  of their functions;  in
this combination also, heat is developed.
  In  purely carnivorous animals, the greater portion of the carbonic
acid results from the disintegration of the muscular and nervous tis-
sues ; while, in the herbivora, much of the food, rich in carbon  and
poor  in nitrogen, is at once converted into carbonic acid,
In urine.	Exhaled.
grs.	grs.
234.6	5183.3
211.5	3741.1
 
732
RESPIRATION.
  Although the action of the oxygen upon the carbon  of the com-
pcfunds, from which the carbonic acid is formed, is a strictly chemical
process, the application of this oxygen  to  the substance  to  be de-
composed, and  the  removal  of  the  resulting carbonic  acid,  are
dependent solely upon  the physical relations which  these  gases bear
to each other, to the membrane through which they pass, and to the
fluids in which they are dissolved.
  The blood, loaded with carbonic acid, at length returns  to  the
respiratory surface, where it parts with this gas and absorbs oxygen
in obedience to the physical laws above referred to.
  More oxygen is usually absorbed than is  necessary to convert the
carbon into carbonic acid.  This is required for  the  oxidation  of
other elements, as  sulphur and phosphorus, by which compounds are
produced which are eliminated by other emunctories.
  The amount of oxygen inhaled will depend in great measure upon
the quantity and nature  of the food, and  upon the activity  of the
vital functions, and is  intimately associated with the  production of
animal heat, as will appear in the next  chapter.
  It has been shown that  the activity of the respiratory function is
materially influenced  by various  external  and internal  conditions.
Temperature, a dry or moist state of the atmosphere, the period of
the day, the digestive process, rest, exercise,  etc., all exert an influ-
ence on the amount of oxygen inhaled and of carbonic acid exhaled.
These are points which must be borne in mind by  the careful prac-
titioner in the treatment of such diseases as phthisis, pneumonia,
emphysema, and the like.
  Respiration is, therefore, partly a physical and partly a chemical
process ;  chemical as  far as regards  the  results;  physical,  with
reference to the means by which these results are produced.  The
introduction  of  the restorative  oxygen, and  the  removal  of the
deleterious carbonic acid, are  effected  solely  by a physical process  ;
while the formation  of the carbonic acid  is essentially a chemical
process, and in its  production many complicated  chemical decompo-
sitions take place.
  The  great objects of respiration  are,  first, the introduction of
oxygen, by which  the  products  resulting from the  disintegration of
tissues  are converted  into compounds, which are  easily  eliminated
from the body by the different organs of secretion; and,  secondly, the
removal of the most important and most  destructive of these, car-
bonic acid, at the pulmonary surface.

  Upon the subjects discussed in the present chapter, reference may be made to the
following works: Article "Respiration," by Dr. John Reid, Cyclopaedia of Anatomy
and Physiology; "Thorax," by Dr. Hutchinson; Physiological, Anatomical, and
Pathological Researches, by Dr. John Reid ; Recherches sur la Structure intime du
Poumon.  Rossignol, Bruxelles, 1846.   The following systematic  works:  Miiller's
Physiology; Bostock's System of Physiology;  Principles of Human Physiology, by
Dr.  Carpenter.
  On  the Mechanism of Respiration.—-Dr. Sibson, Phil. Trans., 1846; Med.-Chir.
Trans., vol. xxxi. ; Dr. Hutchinson, Med.-Chir. Trans., vol. xxix.
  On the Chemistry of Respiration.—M.  Barral, Ann. de Chim.  et Phys., torn. xxv.;
Messrs. Regnault and  Reiset, Annales  de Chimie et de Physique, 1849;  Comptes
Rendus, 1846 ; Lehmann's Physiological Chemistry, translated by Dr. Day, Cavendish
Spciety, 1851-4, 
ANIMAL HEAT.
733
                      CHAPTER XXX.

on  animal  heat.—development  of heat in plants.—develop-
  ment of heat in animals.—temperature of the human body.
  influence of exercise, sleep, age, climate and seasons, food
  and disease upon the development of heat.—hibernation.—
  theory of animal heat.—influencf of the nervous system.
  Bernard's researches.

  The chemical changes which are continually taking  place in ani-
mals, and, at least under  some  circumstances, in plants, are accom-
panied with the development  of a  certain amount  of heat.  The
elevation of temperature may be so slight as  to elude the ordinary
means of observation;  and although the sensible temperature of the
organized body is very slightly higher than that of  the medium in
which it is placed, the quantity of heat set free in a given time may
be considerable.  This development of heat seems to result from the
action of the oxygen upon the combustible elements of the food, and
in a less degree upon those of the tissues.  The chemical combination
in which  the largest amount of heat is disengaged  in the higher
animals, and upon which  their  high temperature seems to depend,
is that of carbon and oxygen, resulting in the production of carbonic
acid.
  Whenever oxygen combines  with  carbon, hydrogen, phosphorus,
sulphur, etc., or with a metal, heat is developed in  an amount ex-
actly  proportioned to the quantity of  substance  consumed.  The
sensible temperature produced  varies, however,  with the  intensity
and rapidity of the  chemical action.  When  the  action is intense,
the temperature rises very rapidly, and may reach a Arery high degree
for  a short time.   If, on the other hand, the action is  slow, the
temperature may be scarcely elevated above that of the surrounding
medium ; but this slight  elevation  may continue for  a considerable
time.   The quantity of heat developed in the two cases, however, is
precisely the same.
  Development of Heat in Plants.—Heat is developed by the seeds
of plants  during  germination ;  and  at the same  time oxygen is
removed from the air, and carbonic acid evolved. Buds, flowers, and
ripening fruits also evolve a certain quantity of heat.
  M. Hubert, in the Isle  of  France, encircled a thermometer with
twelve spikes of the arum cordifolium, and found it rise to 121° F.,
the temperature of the external air being 66°.   During the process
of flowering, the  spathe  of  the  arum  maculatum consumed in 24
hours five times its volume of oxygen derived from the surrounding
atmosphere, the termination of the spadix 30  times,  and the sexual
apparatus 132 times its volume, in the same  period.  In these ex-
periments it was  found, that if the plant was protected from  the
influence of the surrounding air, the development of heat ceased. 
734
ANIMAL HEAT.
In the germination of seeds, the starch is  converted  into gum or
dextrine, and ultimately into sugar.  The  sugar then disappears
while oxygen is absorbed from the air, and  carbonic acid evolved.
The  temperature at the same time rises.
  In these examples, the disappearance of the starch and saccharine
matters from the plant, the  absorption of oxygen, the formation of
carbonic acid, and  the development of heat  are  all manifestly con-
nected.   A corresponding series  of  phenomena attends the develop-
ment of heat in animals.
  Development of Heat in Animals.—It is to be observed in the first
place, that as all animals give out carbonic acid in their respiration,
so all develop heat, whether they  are  called cold-blooded (reptiles
and  all  below them), or warm-blooded (mammalia and birds).  The
cold-blooded animals are those which develop so little heat, form and
give out so little carbonic acid,  that they are unable to maintain a
temperature much  removed from that of the medium in which they
live ; and their circulatory and breathing organs are entirely accord-
ant with this feeble calorifacient power.  Dr. John Davy, who has
made a number of valuable and  exact observations on this subject,
found that when the average temperature around was 79.7° F., that
of reptiles was only 82°, and that of fishes nearly the same.   In
the case of insects, Crustacea, and  mollusca, there is even a closer
correspondence with the temperature of the  circumambient medium.
Insects, however,  especially when housed in  communities, so that
their heat is not  rapidly dissipated, have  shown a rise of 20° F.
above  the outward air—provided  they were in  a  state of active
movement.   On  this  point, the observations  of Mr. Newport are
very valuable.  On the other hand,  warm-blooded animals (birds and
mammalia) are those in which nutrition with all its attendant acces-
sory functions, assimilation, circulation, respiration, the  supply of
food and of oxygen, the formation  and disengagement of carbonic
acid are most active and energetic.   These  have  a  nearly uniform
temperature within the  limits of 96° and  1110 F., the mammalia
having the lower and birds the higher, in strict accordance with the
above-mentioned  circumstances.  A bird, for  its weight,  consumes
much more oxygen, and sets free much more carbonic  acid, while it
maintains in the same medium a  higher temperature than a mammal.
Finally, some degree of warmth is  evolved  by the egg in its devel-
opment during incubation.   In this process, oxygen  is  absorbed,
and  carbonic acid exhaled through the calcareous envelope.
   The  amount of  heat  developed  in the animal organism depends
very much upon the nature  and  quantity of the food.   The carbon
of the food in its slowly effected  union with oxygen within the organ-
ism, gives out probably as much heat as if  the  same quantity were
burnt in oxygen gas.  The  development of  animal heat will, there-
fore, in great measure depend upon the activity of the functions of
respiration and circulation.
   The greater part of the  oxygen  which an adult consumes in the
twenty-four  hours, instead  of remaining in the body, thereby in-
creases its weight, unites with carbon and hydrogen, and is removed 
TEMPERATURE OF HUMAN BODY.
735
in the form of carbonic acid and water.   The remainder enters into
combination with other elements, and compounds are formed which
are removed by the excreting glands.  In these combinations  a large
amount of heat is developed, ranging in amount according  to  the
conditions before referred to.
   Temperature of the Human Body.—The heat of the interior of
the body at those parts which are most accessible to our instruments
of measurement, as, for instance in the  axilla, within the mouth or
rectum, is found to be about 97°  or 99° F.; more frequently the
latter.  The temperature is, however, liable to  variation according
to circumstances, which modify the amount of heat generated within
the body or the  rapidity of its loss.  Independently of this, however,
great differences have been found  to exist in  the temperature of
different parts, according  to the rate of  their cooling, their vascu-
larity, distance from the centre  of circulation, etc.   A good  idea of
this will be derived from the following Table  of Dr. Edwards.   He
examined a strong man,  at  rest, in July, the air being at 71° F.,
and found
       Mouth and rectum........102°
       Hands..........99°.5
       Axillae and groin........99°
       Cheeks..........96°
       Feet..........96°
       Skin of Epigastrium.......95°

   The best experiments on  the temperature  of  internal parts, are
those of MM. Becquerel and Breschet, who employed  a thermo-
electric apparatus, consisting of  two  wires of  different  metals,
soldered together, and having their free ends brought into communi-
cation with an excellent thermo-electric multiplier,  with an index to
show lOths of a degree.   The wire, passed  through various parts of
the body, indicated the temperature of the tissues in contact with the
point  of contact of the two metals.  Passing this 1J inch into the
calf of the leg,  the temperature was found  to be 98° F., while at a
depth of ^ inch  it was only  94°, showing the  cooling from the sur-
face inwards.  The superficial fascia over the biceps was nearly 3°
lower than the muscle itself; on compressing  the brachial artery, so
as to intercept the flow of  blood, the temperature immediately fell
several lOths of a degree.  So after the ligature of the main artery
for aneurism, the  temperature is well known  to  fall, and to  require
to be economized with increased clothing.  Professor Fiik obtained
the following results  in twelve experiments upon living dogs.  No
difference in  the temperature was observed between the right  and
left ventricle of  the  heart.  The  highest degree  of  warmth  was
always met with in the vagina and rectum (101.75 to 105.79).
   As exercise is attended  with  quickened circulation, more active
respiration, a more abundant interchange of oxygen and carbonic
acid, so it occasions an augmentation of  animal  temperature.   The
secretions are more copious—there is a  more energetic nutrition—
the quantity of  food  required is greater,  and  we  all know how much
more keen our appetites are, and  how much more  food we consume 
736
ANIMAL HEAT.
when engaged  in  employments requiring  active exercise, than in
sedentary occupations.  MM. Becquerel and Breschet have observed,
that the muscles during their contraction become hotter by 2° or 3°,
a fact which one of us  can attest from an experiment on the biceps
in his own person,  made by these gentlemen themselves.
   Sleep,  as it is attended with  diminished frequency of respiration
and pulse, and a smaller  evolution of carbonic acid, is also marked
by a slight fall of temperature, viz., of from 1° to 3° F.
   Age has been shown  by Dr. Edwards  to  have much influence on
temperature.   Old persons, and very young ones, are alike unable to
preserve  their proper warmth without external aid, and have not the
same power  as  adults  of generating heat.   For example, he found
that young carnivorous and rodent animals, when placed in an atmo-
sphere of 50° F. apart  from the body of the mother, quickly became
cold, though when  lying near her they continued within 2° or 3° of
her temperature.   So,  young sparrows one  week old were at 97° F.
in the nest, but when  removed from the nest, fell in one hour to
66° F., when the external air was at 62° F.; and  he showed that
this result was not to be attributed to their unfledged state.
   Young animals,  therefore, require the  aid of external warmth, or
at least of every means of retaining their own warmth.  The nests
of birds not only serve to  retain the warmth of  the  parent during
incubation, but  also that of the young  brood during  their tender
age.  The human infant stands  no less in need of extraneous warmth
—and it  may be safely affirmed, that much of the immense mortality
of our infant population is owing to the want  of artificial heat.
   We  must  refer  to what has  been already  said in the chapter on
food (Chapter XXIL),  for observations on the relation of the kind
of food to the animal temperature.
   Influence of  Climate and Seasons.—The best  account we possess
of the  effect of climate  results from 4000 experiments made on board
the Bonite, a French vessel, during her passage between Cape Horn
and  the tropics.  The mean temperature  of 10 men at Cape Horn,
with the  thermometer at  32° F., was hardly two degrees  lower than
at Calcutta, where the  thermometer stood at 104° F.  The tempera-
ture of the body was found  to  rise and fall perceptibly, but slightly
—to fall slowly in passing from a warm to a cold climate, and to
rise more rapidly in re-entering the torrid zone.
   The rate at which an animal loses its heat will depend both on the
coldness of the  surrounding air, and  on the rapidity of evaporation.
In temperate climates  these causes  differ inversely with the season.
In winter there  is  much  loss by radiation, little by evaporation ; in
summer  the reverse.  But Dr.  Edwards has well  shown  that these
compensations are not the only cause of the uniformity of temperature
so wonderfully maintained, but  that there is also in animals a differ-
ence in the rate at which heat is produced, according  to the season,
"- the calorific faculty is more active in winter than in summer." " In
winter there is a more  active production with greater loss, in summer
a less  production  with smaller loss."   To test  this, Dr. Edwards
contrived a box surrounded with ice, having the same  external tern- 
LOSS OF HEAT BY EVAPORATION.
737
perature, and the same  humidity of atmosphere in winter and sum-
mer, so that the  loss by radiation and evaporation should be the
same in both cases.  Into  this apparatus, in February, he placed 5
sparrows that had been  living in  a warm room, and found that after
an interval of  3 hours they maintained their previous heat within 1
F.   Again, in July, he did the  same with 4 others, and these after
3 hours were found  to  have lost 10° F.   We may here recall the
fact, that the quantity of  carbonic acid exhaled is greater when the
external temperature is low.   Mice and guinea-pigs  evolve twice  as
much carbonic acid  at 32° as at 60° F., and birds more than double.
Also more food, and of the calorifacient kind, is required in winter
than in summer, and in cold climates than in warm.
   The  nature  of the food  must vary with  the temperature of the
climate, for at the same time that the respirations are less in number
in hot than in cold climates, the  air is less dense, and  contains in  a
given volume less oxygen ; hence a light and succulent diet  is better
adapted to the requirements of the system, and comparatively little
heat is developed; while, in cold  climates, a large quantity of highly
earbonaceous food is necessary in order to furnish the  requisite sup-
ply of  heat.
   In animals which are very active, and which are  not subjected to
the cooling influence of an atmosphere many degrees  lower in tem-
perature than their  own bodies, it is quite possible  that  a sufficient
 amount of heat may be generated in the combination of the  elements
 of their tissues without the  necessity of fatty  or starchy food form-
 ing a part of their highly nitrogenous  diet.   In cold  climates, how-
 ever, a large quantity of readily combustible  food is necessary in
 order to furnish the requisite amount of heat.
   Loss of Heat by  Evaporation.—The animal body  is continually
 subject to evaporation of its fluid parts, just as any other moist sub-
 stance, and the  amount of evaporation, and the consequent loss of
 heat,  will depend on the same causes as in  the  case of inorganic
 substances.  The moisture, or dryness, of the  surrounding air, and
 its state of motion or rest, will mainly  influence the result.   All the
 effects of excessive  temperature on the body are much  more apparent
 with a moist than a dry atmosphere ; because  in the  case  of a dry
 atmosphere a greater amount of evaporation takes place, and hence a
 greater quantity of heat is removed from the system.
  3  In England it would be impossible to  sustain a  vapour bath at a
 temperature of  110° or 120° for more  than 10 minutes, whereas the
 body may be without  danger  exposed for the same time to  a dry
 temperature twice as high or more. In some well-known experiments
  Sir Charles Blagden  remained immersed for 8 minutes in dry air
 heated to the extraordinary pitch of 240° or  260° F.   An oppres-
 sive day in summer is one where the  air is moist at the same time
 that it is hot and stagnant.                                    .
    Again, the refrigeration, arising from simple contact of cold air,
  is much  increased by motion of the air,  i. e.,  by a rapid renewal of
  fresh cold particles; and all the more  if the moving  air be dry.  A
  cold dry wind is one of the most powerful refrigerators, but we could 
738
ANIMAL HEAT.
hardly realize the full extent  to which this is true, without an ex-
ample. Mr. Fisher, the surgeon to the expedition to the Polar Seas,
under Sir Edward Parry, has related its extraordinary effects.   The
hardy sailors found that they could better  bear a cold which would
freeze mercury (viz., 40° below zero, F.) when the air was perfectly
calm, than a temperature of 10° F. i. e., 50° higher) when the wind
was up.
  The rate of cooling, and the amount  of heat  parted with in this
manner depends upon the difference in temperature between the body
and that  of the surrounding medium. The loss of heat must of course
be much  greater in the Polar regions, where the temperature is 100°
or more below that of the body, than in hot climates where the tem-
perature  of the air approximates to that of the body.   Yet the tem-
perature  of the body is the  same in each case.   The cooling effects
of cold climates are compensated  for  by the  increased quantity of
highly carbonaceous food taken, and the increased activity of the re-
spiratory functions.   A much larger quantity  of carbonic acid is
evolved,  and a much greater amount of heat liberated, than in warm
climates,  where the food must be smaller in  quantity, and should con-
tain less  carbon and hydrogen.
  Warm  clothing, by protecting the body from the influence of cold
air, and so peventing  the loss of a certain amount of heat, may be
said, as Liebig has remarked, to be equivalent in cold countries to a
certain amount of food.  The appetite is increased in cold weather,
and if in winter we clothe lightly we shall eat more  than if warmly
clad.   We may often remark, that lean spare men, who take a great
deal of exercise, consume many times the quantity of food which sa-
tisfies a  moderately plump  individual.   The former  has usually a
larger respiratory capacity, and is less  protected from  the  cooling
influence  of the external air.
  Influence of Food.—If an insufficient  quantity of food be taken,
the temperature of the body falls, and the carbon and hydrogen, en-
tering into the composition  of the  tissues themselves, combine with
the oxygen, and thus a certain amount  of heat  is furnished.  Defi-
ciency of food  is  borne much more readily in a high temperature
than in a low one. Cold very much expedites death from starvation.
The highly important and interesting experiments of Chossat* upon
animals have shown that  in starvation  the  fatty matters,  which  are
most readily convertible into carbonic acid, are  first removed, soon
afterwards the substance of  the muscles  is  acted upon, in order  to
furnish an amount of  heat, without the development of  which  life
would at  once cease; next the nervous system gives way to this oxid-
izing poAver—life ceases, and every portion of the organic material,
with the exception of the mineral matters combined with it, is brought
under the  destructive  influence  of the  oxygen.  M. Chossat found
that, taking 40 per cent, as the mean, fat lost 93.3, blood 75, heart
44.8, muscles 42.3, skin 33.3, bones 16.7,  and the nervous system
only 1.9  per cent, of their weight in fatal starvation.
Recherches experimentales sur PInanition. 
HIBERNATION.
739
  The time required to produce death from starvation varies accord-
ing to different circumstances.   If the body be very fat, life will be
supported for a longer period than if only a small  quantity of fatty
material be present.   A fat pig, which  was confined by a slip of
earth, lived 160 days without food, and during this period  he lost
more than 120 lbs. (Martell, Trans. Linn. Soc, vol. xi. p. 411, quoted
in Liebig's letters).   While death from starvation would be retarded
by warmth, little or no exercise, and  a moderate supply of water, it
would be much accelerated by the converse of these circumstances.
  Influence of Disease.—In acute diseases  accompanied with fever,
such  as pneumonia, pleurisy, acute rheumatism, and  in scarlatina,
typhoid fever, etc., the temperature often rises several degrees above
the normal standard, not unfrequently reaching 105° or 106° F.  Dr.
Edwards observed the temperature as high as HOf in a case of teta-
nus.   This high temperature sometimes decreases rapidly, and some-
times very gradually, the diminution  being frequently accompanied
by free perspiration and copious excretion of urine, rich in urea and
lithates.  The frequency of  the pulse also  diminishes  at  the  same
time.  This increased development of heat, during the  exacerbation
of the fever, is associated with the increased amount of disintegration
of tissues  taking  place at that time;  while  the  remission  is ac-
companied by the  elimination of the resulting  compounds, free  per-
spiration, diminished  frequency of pulse, and corresponding decrease
of temperature.*
  In those diseases, on  the  other hand, where  the activity of the
chemical processes going on in the body is impaired, the temperature
falls many degrees below the normal  standard.  In cholera, where
the dark blood and imperfect respiration mark the introduction of an
inefficient supply  of  oxygen, and  the  suspension  of secretion  and
the absence of symptoms  characteristic of  the accumulation of ex-
cretory products in the organism,  show that the  chemical changes
accompanying the disintegration of the tissues are only taking place
in a slight degree, or are altogether suspended, the temperature often
falls to 70°, or even  much lower.  It  is curious  that, in many of
these  conditions, the temperature  should rise.very rapidly imme-
diately after death.   The most striking examples of this  have been
placed on record  by  Dr. B.  Dowler,  of New Orleans,  and occurred
in cases of yellow fever, etc.  In one  instance, just before death, the
temperature was 104°;  and fifteen minutes after death, it had risen
to 113° in an incision in the  thigh.  The temperature still remained
very high for several  hours after death.
   Hibernation.—The phenomena of hibernation are dependent upon
the conditions we have just alluded  to.  Previous to becoming torpid,
the animal accumulates a quantity of fat, which is, as  it were, laid
up  as in  a storehouse, to  be consumed slowly, while  the period of
annual sleep lasts.  At this  time, the activity of the vital functions
is much reduced, the  animal  lies perfectly still, the frequency of the

  * See a review, by Dr. H. Weber, in the Medico-Chir. Review, Jan. 1853,  on Crises
and Critical Days, by Dr. L. Traube. Berlin, 1852. 
740
ANIMAL HEAT.
heart's  action and  of the respirations diminishes; its temperature
falls many degrees, and it is placed in a condition the most favourable
for supporting life for a considerable period of time with  a very
small supply of  combustible material.  The  moment   the animal  is
roused,  the vital processes again become active, and a supply of food
soon  becomes necessary.  In  the case of  the  marmot, in  which
animal the hibernation is complete, the pulse falls to  about 15 beats
in a minute, and the  respirations  to  about  14 in an hour, while in
the waking state these are respectively 150 and 500.   The tempera-
ture of  the body, during the  hibernating period, may fall as  low as
35°.  If, however,  the animal be  exposed to warmth,  the frequency
of the  pulse  and respiration increases, a much larger quantity of
oxygen  is consumed, and a corresponding proportion of carbonic acid
exhaled.  The temperature  of the  body suddenly rises, and  the
animal soon dies, unless supplied with food.
   Theory of Animal Heat.—It has been shown, that in certain parts
of plants, and in cold as well as warm-blooded animals,  heat is de-
veloped coincidently with the consumption of  oxygen, the combustion
of carbon, and the formation of  carbonic acid.   The heat produced,
and the chemical product of combustion, have been observed to bear
a certain general correspondence one with the other.
   To understand the  real  nature of the development of  heat  in
organized bodies, it is necessary to remember,  that the heat  disen-
gaged during the oxidation of carbon or of a metal (i. e.  during the
combustion  of these bodies) is directly proportioned to the amount
and not to the intensity of the chemical action.   In  the  words of a
distinguished chemist, "The rod of iron that is burnt in oxygen gas,
produces a heat  which no one  will deny;  but the iron which rusts
slowly in the air, disengages just as much heat, although its tempera-
ture never rises  sensibly above that of the surrounding atmosphere.
Phosphorus alight burns brilliantly, and produces abundance of heat;
phophorus in the cold,  still burns, but Avith little lustre, and the heat
which it evolves  was for a long time denied."*
  It has been  already stated (p.  515-16) that a large  portion of the
food being destitute of nitrogen, is  not the best adapted to form part
of the tissues of  the body into the composition of which that element
enters.   This  calorifacient food (consisting of various quantities of
carbon in combination with oxygen and hydrogen, in the  proportion
in which these last  form water, as starch, sugar, cellulose, or gum,
or of carbon and hydrogen in combination with a less proportion of
oxygen  in fatty matters) seems to be devoted  in the main to the pro-
duction  of heat by the combination of its carbon and hydrogen with
the oxygen furnished by respiration.  It is a question  through what
changes it passes ere thus consumed;  but of  its eventual destination
to the production of heat there would appear to be no  doubt.
  As was shown in the chapter on  Respiration, more  oxygen is
taken into the blood by the lungs than  is required to form the car-
bonic acid exhaled.   This superfluous  oxygen disappears, the greater
* Dumas, "Balance of Organic Nature," p. 37. 
THEORY OF ANIMAL HEAT.
741
part appearing to  enter  into  combination with hydrogen, while a
small quantity goes to oxidize the sulphur and phosphorus.  The  air
breathed is likeAvise found to have lost bulk.   Now, gaseous carbonic
acid contains its  own  bulk of oxygen—but oxygen uniting with
hydrogen to form water is condensed.   Such  a  condensation of the
oxygen would accord with the observed diminution of bulk in air by
being  respired.   It has  been  remarked that herbivorous animals
return to the air,  as  carbonic acid, only nine  out  of  ten  of the
volumes  of oxygen absorbed  in  respiration, and  that  carnivorous
animals return in the same form, only five or six out of ten volumes.
The carnivora, then, absorb nearly twice as much oxygen as they
employ for oxidizing carbon, and a very large proportion of the  re-
mainder, no doubt, combines with hydrogen to form water.
   To  explain the  prompt oxidation of  the  carbon  and  hydrogen
within the body, Liebig has pointed out that the oxygen is presented
to them not in a gaseous but in a liquid or solid form—that in  the
innumerable channels of the circulation, these  several elements  are
not merely brought  together in a very subdivided state, but every-
where in close  proximity  to  membranous surfaces, mechanically
adapted to favour the occurrence of chemical union.  Moreover, that
the carbon and hydrogen  are not offered to the oxygen in their pure
and simple state, but in combinations already existing and ready to
be dissolved.  He also insists, with great force, on the analogy of
these actions to  those promoted by the presence of a body already
undergoing oxidation.   For example, " when weak brandy is allowed
to trickle over shavings  in a  close vessel, through which a  feeble
current of air at  from 93° to  97° F.  circulates, the  alcohol in  the
brandy remains unchanged; in  spite of the greatly increased surface,
no  oxidation, no  formation  of acetic  acid  takes place.   But  if to
the brandy there be added one  hundred thousandth part  of vinegar,
beer, or wine, in the state of acetification, that  is, of oxidation,  the
alcohol disappears  with great  rapidity,  and is converted, by the
absorption of oxygen, into an equivalent quantity of acetic  acid.  In
the vessel, the surface of the shavings themselves  very  soon passes
into the state of oxidation, and from this period forth, the  brandy is
acetified without the addition of  a ferment; the wood, being in  the
state of decay, eremacausis, or slow combustion, plays the part of a
ferment.  These vinegar-producing vats give an idea, if only a rough
one, of the  process  of  oxidation going on in the animal body.   As
in the body, so also in these  vessels, a temperature higher than that
of  the surrounding  media is kept up, without  the  aid  of external
heat."*
   These actions of contact or catalysis may well be  supposed to play
a  large and most important part, not merely in the  production of
animal heat, but  also in  all the chemical changes  which are ever
going on in  the body, from  the first reception of food to the final
expulsion of its  elements in  other forms of combination.   Great

              *  "Animal Chemistry," p. 34, 3d edition, Part I.
       48 
742
ANIMAL HEAT.
obscurity, however, still hangs over the series  of  transformations
which the food undergoes in its passage through  the body.
  It has  been seen that  both  arterial  and venous blood contain
oxygen and carbonic acid gas in a state  of solution;  but into Avhat
form of combination the oxygen first enters, or from Avhat immediate
source the carbonic acid is  derived, is  as yet matter  of conjecture
only.   It may be regarded  as most  probable  that  the chemical
changes which issue in the formation of carbonic  acid and water, and
the disengagement of heat, are effected in the tissues themselves, or
in the systemic capillaries, in the immediate  vicinity of the tissues.
  Influence of the Nervous System.-—Much difference of opinion has
existed as to the share taken by the nervous  system in  the produc-
tion and maintenance of animal temperature, some distinguished men
having argued that this  system  is in some way the  source  of heat,
while others have limited its operation to the exercise of a controlling
and regulating  influence over  this important function.   The latter
conclusion is  that to which a  just  estimate of the numerous facts
advanced on both sides  would appear to lead.   The experiments of
Dulong, repeated and modified by Despretz, seemed, indeed, for some
time to indicate  that a  portion of the heat developed in the body
could not be referred to the consumption of the oxygen inhaled, and
that, therefore, some other source for it must be sought.   They com-
pared the heat given to  a calorimeter by an animal placed within it,
with that produced by the combustion  out of the body  of as  much
carbon and hydrogen as the animal gave off in the same  time,  in the
form of carbonic acid and water, and found that more heat was given
off by the  animal than the chemical  products of its respiration would
account for, to  the extent  of  from one-fifth  to  one-tenth.   It has
since been shown, hoAvever, that, on  the one hand, allowance was not
made for an actual cooling down of the animal below its normal tem-
perature by exposure to the refrigerating influence of the  calorimeter,
so that the heat indicated had not all  been produced  within the
period of the experiment; and, on the other, that the heat generated
by the corresponding chemical actions out  of the body had been
under-estimated.  Dulong himself furnished a more correct estimate
of the heat deATeloped by the combustion of hydrogen; and his  results
have been confirmed  by Fabre and  Silberman.  Hence,  while  it
would be premature to attach  too much  value to such experiments,
considering our ignorance  of the  exact series of chemical changes
indicated by the resultant  carbonic acid and water, they certainly
are not, as they once seemed to be, opposed to the  chemical  theory
of animal heat.
  It may be regarded as certain  that  the nervous system exerts a
considerable influence upon the  development of  heat in the  body.
The experiments of Sir  Benjamin Brodie, and subsequently those of
Le  Gallois and Chossat, have established the fact that lesions  of the
nervous centres are accompanied with a diminution of temperature, and
of the power of forming heat.  Again,  the temperature of paralyzed
limbs is almost always less than that of sound limbs, and often so to
a very marked degree.   In some instances, however, twin lesions of 
BERNARD'S RESEARCHES.
743
the nervous system are followed by an opposite effect.   Much light
has been thrown upon the influence of the nervous system upon the
development of heat,  by the recent highly interesting and important
researches of M. Bernard.
  Bernard has lately established the very interesting fact, that sec-
tion of the sympathetic nerve is followed by a considerable elevation
of temperature in  that side of the head or face corresponding to the
divided trunk.   This increase  of temperature occurs immediately;
and persists  after all  increased  vascularity and turgescence have  dis-
appeared, and after the wound  in the neck  has  quite healed.  The
same observer found  that sections of nerves of motion and sensation
produce respectively, besides paralysis, a diminution of temperature,
while, if a mixed nerve containing fibres of the sympathetic, as  the
facial, is divided, an exaltation  of temperature takes place, arising,
doubtless, from the division of the sympathetic fibres.  The increase
of  temperature seems to be a special result of  the division  of  the
sympathetic.
  Now, if the upper  extremity of the sympathetic, which  has been
divided in the neck of an animal, be subjected to an interrupted gal-
vanic current, the exalted temperature which follows its division is
no longer manifested, and the parts supplied by it actually fall below
the normal standard,  and they rise again when the current is stopped.
When an  animal, in which the sympathetic had been divided, was
placed under the influence of chloroform, the temperature which had
risen several degrees  in consequence of the division of the nerve, fell,
while it again rose when the animal had recovered from the effects
of the chloroform.
  Bernard has shown that the increased temperature following divi-
sion of the sympathetic, or removal of the superior  cervical ganglion,
cannot be attributed solely to the increased quantity of blood, Avhich
is allowed to enter the vessels in consequence of paralysis of their
contractile coats; for it occurs when the blood is allowed to stagnate
in  the vessels  by tying them.    At the same time, it is necessary
that the vessels should contain blood.   The  enlargement of the ves-
sels and the increased flow of blood  to  the  parts  are to  be  looked
upon as the result of  the altered nutritive changes which take place
in consequence of the division of the sympathetic, rather than as the
cause of the rise of temperature.   Whatever may be the  exact order
and nature of the changes which ensue,  they may be looked upon as
a more active manifestation  of the ordinary phenomena of  animal
heat.
  This increase of temperature, which is found generally to  accom-
pany the  abstraction  of nervous influence, has  been accounted  for
by the supposition that the tissues were more readily  acted upon
by the oxygen of the air when  deprived of  the protective agency of
the nervous system; but although this increased action of the oxygen,
or more rapid combustion, may perhaps have considerable weight in
the  production of these phenomena, it must, by  no means, be re-
garded as the sole cause, nor can the chemical theory of animal heat,
as it at present stands, be considered as giving an  explanation of the 
744
VOICE.
Avhole of the facts observed in connection with this highly interesting
but abstruse subject.
                                I
  Upon the subject of Animal Heat, the following works may be consulted: Dr. Craw-
ford's " Experiments and Observations on Animal Heat," 1788; Dr. J. Davy's Memoirs
inthe Philosophical Transactions, 1814;  "Recherches Experimentales sur I'lnani-
tion," M. Chossat, Paris, 1843; Liebig's Animal Chemistry, 3d edition; Sir Benjamin
Brodie's Physiological Researches, and also papers in the Phil. Trans., 1811-12 ;  the
article Animal Heat, by Dr. Edwards, in the Cyclopaedia of Anatomy and Physiology,
vol. ii.;  Lehmann's Physiological Chemistry; Mr. Newport on the Temperature of
Insects, in the Phil. Trans., 1837; Mem.  "Sur la Chaleur Animale," par MM. Bec-
querel and Breschet, in Ann. des Sciences Nat., Seconde Serie, torn. iii. iv. et ix.  M.
Bernard, "Recherches Experimentales sur la  Grand Sympathique," Paris, 1854.
                       CHAPTER XXXI.

VOICE.—H0AV PRODUCED.—ITS EXISTENCE IN THE ANIMAL KINGDOM.
  —THE HUMAN LARYNX.—ITS CARTILAGES.—THEIR ARTICULATIONS
  AND LIGAMENTS.—CHORDS VOCALES.—MUCOUS  MEMBRANE.—MUS-
  CLES, EXTRINSIC AND  INTRINSIC.—ACTION  OF  THE  LARYNGEAL
  MUSCLES.—NERVES.—ACTION OF THE LARYNX.—THEORY OF VOCAL-
  IZATION.—CHEST  VOICE.—FALSETTO  VOICE.—SINGING.—INFLU-
  ENCE OF THE NERVES ON VOICE.—SPEECH.

  The high development of man's intellect, as compared with that
of the lower  animals,  would be  of comparatively  little advantage
without his peculiar endowment of speech.  To this power, an  essen-
tial subsidiary is  that  of producing vocal  sounds  or voice; which,
however, he enjoys in  common with  a large  number of the  lower
classes.
  The phenomena of voice are  produced  by a very beautiful  and
simple mechanical contrivance, the larynx, which  is placed  at  the
top of the trachea, to  take advantage, as  an  exciting force, of the
air emitted from the lungs during expiration.   The air thus expelled
creates vibrations in certain  tense and elastic membranes  (chordx
vocales), the  boundaries of a chink which  is  the  orifice at once of
entrance and of exit for the supply  of air to the lungs.  These vibra-
tions generate voice.
   That the larnyx is the organ of  voice  is proved by the following
very obvious facts: first,  the  least alteration in the condition of the
mucous membrane covering the vocal chords  is invariably accompanied
by  a change  in the tone of the voice, e.  g. hoarseness ; secondly,
ulcerative disease eating through one  or  both of these vocal chords
destroys or greatly impairs the voice ; thirdly, opening the trachea
below the vocal chords, so as to divert the  current of air in expira-
tion from the larynx, will destroy voice; and fourthly, section of the
inferior laryngeal nerves, by which  the influence of the will is brought
to bear on its muscles,  and so the tension of the vocal chords is regu- 
HUMAN LARYNX.
745
lated, destroys the voice ; lastly, by experiment on the dead larynx,
sounds may be produced resembling those of the voice.   If a current
of  air be  made to play on the vocal chords by  a bellows fixed to the
tracheal end of the larynx, or by blowing air through  it, distinct
vocal sounds are excited which can be Araried by altering the tension
of  the  vocal chords.
  There is no instance of true voice among the lower  orders of creation except in
those animals that have a larynx connected with the respiratory apparatus, as in man.
In other words, all animals  that have no  larynx are voiceless.  The hum of insects
is a phenomenon essentially different from  voice, and is caused by the rapid vibration
of an apparatus connected with their wings.   All the other invertebrated classes are
incapable  of producing sounds.  Fishes,  likewise, are voiceless.   The Batrachian
reptiles possess a larynx and can pro-
duce vocal sounds.   The hissing of
serpents is, likewise, laryngeal.  But
the Chelonian reptiles have no voice.
In birds there are two organs placed,
the one in  front of the  other,  to
which the name of larynx has been
given  by anatomists; of  these,  the
lower, or that nearest the lungs, is
the true vocal apparatus; the upper
is  merely a resonating or reciprocat-
ing cavity destined to  enhance  the
intensity of the sounds  generated in
the lower.  Cuvier showed that an
opening between the  two  organs did
not destroy the power  of producing
sounds, so long as the inferior larynx
was uninjured.

   The human  larynx is  a
kind   of box,  composed   of
pieces  which  may  be  moved
on each other, and  incloses
the   membranous  bands   in
which the vocal vibrations are
produced.  These  pieces, when
articulated  together,  consti-
tute the skeleton of the larynx.
They are  composed of carti-
lage, and form a very curious
mechanism.    There  are five
distinct pieces (two of  which
are symmetrical)  essential  to
this  mechanism,   and  there
are   four   smaller,   accessory
cartilages.   The  first are the
cricoid and the thyroid carti-
lages,  the epiglottis, and the
arytenoid  cartilages,   which
are  symmetrical.  To  these
may  be added the  cuneiform
cartilages  and the cornicula,
which  are merely  sesamoid
Fig. 210.
 Cartilages of larynx and epiglottis, and upper rings
of trachea in situ seen from behind.  From a prepara-
tion in the Anatomical Museum, King's College, by Mr.
Cane.
 a. Arytenoid cartilages, b. Superior cornu.  c. In-
ferior cornu. d. Posterior surface of cricoid, e. Fora-
men for superior laryngeal nerve. /. Perforations of
epiglottis, i. Upper margin of thyroid,  t. Trachea.
h. Eight inferior tubercle. 
746
VOICE.
bodies destined to keep the folds of mucous membrane in  proper posi-
tion.
   The cricoid catilage is a ring, whose lower margin i3  parallel  to,
and united by fibrous  membrane with the first  ring of the trachea.
Its upper margin slopes from behind forwards, and from above down-
wards, so that the posterior surface of the cartilage  is considerably
deeper  than  the anterior, and  affords  two  large concave surfaces
for  the  attachment of the  posterior  crico-arytenoid  muscles.   Its
upper border is connected in front with the lower margin of the alse
of the thyroid cartilage by an  expansion of yellow fibrous tissue,
which is particularly thick in front, called the crico-thyroid ligament,
and which fills up the space  called by surgical anatomists the crico-
thyroid space.   This space  and  ligament, bounded on each  side  by
the  crico-thyroid  muscle, are penetrated  by the trocar  in the ope-
ration of laryngotomy.  The posterior half  of the upper border of
the cricoid cartilage exhibits on each  side an oval convex articular
surface on which plays one of the arytenoid cartilages.
   Tbe thyroid cartilage consists  of two  square plates  of cartilage
(alee) united at an acute angle in front; each  of these is prolonged at
the  upper and lower  corners behind, into a  long superior  process
(superior cornu) and a very short inferior process (inferior cornu).
By the superior process,  and along the whole superior border of  its
alas, the thyroid cartilage is united to the os hyoides by the thyro-
hyoid ligament.  Each inferior process rests upon the outer surface

                               Fig. 211.
  A. Thyroid cartilage,  a. The notch.  J. Superior cornu.  c. Inferior cornu. d. Slight prominence
rnSTubeTcle^ ^T^^A^T™* °* M^ "«■  *. I Superior and
  B. Cricoid cartilage seen from the side. a. Posterior superior margin, b Articulating surface of
^Stbyroir8- f~ SuPerior ^^ending margin, h. The right surface ^SlS^th Jiferior

  C. The right arytenoid cartilage,  a. Base; position of the crico-arytenoid articulating grooves
e. Lateral prominence at ba«e, which gives attachment to the crico-arytenoideus lateralis and posti
cos. d, b Convex triangular surfaces for the attachment of the superior thyroarytenoid li3
/. Cormculum laryngis ; between/and e, the posterior aspect of the arytenoid cartilage and concave
surfaces giving attachment to the oblique and transverse arytenoid muscles,  a. VerUca? portion of
cuneiform cartilage.                                          "     "<.«imiuu»»i 
VOCAL CHORDS.
747
of the cricoid cartilage, and plays upon a small circular plane articu-
lar facet situated thereon.
   By the angular union of the two alae of the thyroid cartilage in
front, a projection is formed beneath the integuments which is most
prominent in the male, and is commonly known as the pomum Adami.
Into the hollow angle behind, the vocal chords are inserted, and also
the stalk  and ligament of the epiglottis.  The broad outer surfaces
of  the alee give attachment  to muscles along an oblique line, which
is sufficiently conspicuous between the middle and lower third of each.
The thyro-hyoid and sterno-thyroid muscles are thus attached.   To
the  inner surface of each ala are inserted  the thyro-arytenoid and
the crico-thyroid muscles.
   By the gliding of the inferior horns of the thyroid upon the articu-
lar facet  on the outer  surface of the cricoid cartilage, a movement
of the one  cartilage may take  place on the other,  round an  axis
passing transversely through the  cricoid.   By  this  movement, the
crico-thyroid space may be enlarged  or diminished according as the
cartilages separate from or approximate each other in front.
   The arytenoid cartilages are two pyramidal bodies articulated by
their bases with the  oval articular surfaces, already described on the
upper margin of the cricoid  cartilage.   Each presents a concave pos-
terior surface  in  which is   implanted  the  arytenoid muscle  which
passes from one cartilage to the  other;  an inner smooth surface
covered  by mucous membrane, and  an  outer surface which  gives
attachment to the crico-arytenoid muscles.  From the anterior angles
of the bases of the arytenoid cartilages  proceed  the vocal chords to
be inserted into the angle of the thyroid.  The mobility of the articu-
lation of the arytenoids with the cricoid, and their connection with the
vocal ligaments give them great importance in the mechanism of the
larynx.
   The cornicula and the cuneiform cartilages are placed beneath the
mucous membrane—the former at the apex, the latter parallel to the
anterior border of the arytenoid  cartilages.
   The Epiglottis is a remarkable valve-like  cartilage, in shape  like
the spout  of a  ewer.  It seems  to issue from the angle between the
alge  of the thyroid cartilage, to which it is  attached  by a stalk-like
ligament.  It projects above the root  of the tongue, and lies between
that organ and the  aperture of the  larynx, like a valve, which is
pressed over the glottis when the tongue is retracted.  Its  upper
border is  convex, and  its posterior surface is concave, transversely
convex in its length.   It is a smooth and  very flexible cartilage,
covered by a mucous membrane, but penetrated by holes and depres-
sions in which are lodged the numerous mucous glands of the mem-
brane that covers it.
   Such is the skeleton of the larynx;  it hangs from the hyoid bone,
suspended by the thyro-hyoid ligament and muscles, and, through the
hyoid apparatus and some muscles, it  is  brought into connection with
the lower jaw and the base of the  cranium.
   Vocal  Chords,  or Superior Thyro-Arytenoid  Ligaments.—The
various cartilages of the larynx are connected to  each other by liga- 
748
VOICE.
ments.   Of these, the most important and interesting, as being the
essential part of the mechanism for producing vocal sounds, are the
bands of fibrous tissue which extend from  the anterior angle of the
base of the arytenoid cartilages to the  angle between the wings of
the thyroid.   These are the thyro-arytenoid ligaments, or, in physio-
logical language, the vocal chords.   They are bands  of elastic liga-
ment, extending between the  points named (t, v, Fig. 212).  They do
not, in the quiescent  state, lie parallel  to  each other, but converge
from behind forwards; their relative  position, as well  as their ten-
sion, can be varied to a considerable degree by reason of the mobility
of the arytenoid cartilages.  The length of the vocal  chords is greater
in the adult male than in the female, being as  3 : 2.
   The elastic chordae vocales are connected by an expansion of elas-
tic tissue  with  the superior thyro-arytenoid  ligaments, which are
small bands  of the same tissue, extending from the apices of the
arytenoid cartilages to the hollow angle of the thyroid, and separated
from the  inferior by  a  space called the  ventricle of  the larynx.
These  superior  ligaments are likewise known as  the false chordce
vocales.
   Much  importance is attached  by Lauth, Muller,  and others, to
the fact  that  many of the ligaments of  the larynx are composed of
elastic tissue, and connected  together by a fibrous expansion of a
similar structure.   Lauth describes  the  elastic tissue of the larynx
as starting from the angle of  the thyroid cartilage between the inser-
tions of the thyro-arytenoid muscles, whence the fibres radiate down-
                                wards,  obliquely  backwards, and
                                even  somewhat upwards, forming a
                                continuous membrane, which passes
                                to  the  cricoid and arytenoid carti-
                                lages, lines  the ventricles  of the
                                larynx, and  is  connected  with the
                                crico-thyroid  ligaments  and  the
                                vocal chords, both true and false.
                                The  thyro-hyoid  ligament is like-
                                wise  elastic; and also  the fibrous
                                bands which connect the epiglottis
                                to the thyroid cartilage, and hyoid
                                bone, and the tongue.   "If," says
                                Muller, "we  add to  these parts the
                                elastic  longitudinal   fibres  in  the
                                membranous  part  of the  trachea
                                and bronchi,  we shall  have an idea
                                of  the  great extent  of the tissues
                                susceptible of consensual  vibration
                                and  resonance in the  parts  sur-
                                rounding the organ of voice."*
                                   The  mucous membrane of  the
                                larynx  is part of the great respira-
Fig. 212.
 View of the larynx from above, after Willis.
B. Ligaments uniting arytenoid and cricoid
cartilages,  x and z.  Direction of axis on
which the thyroid cartilage turns. E. Thy-
roid cartilage,  k. Left thyro-arytenoid mus-
cle ; right removed, r, u, X, W. Cricoid car-
tilage. N, X. Right crico-arytenoid muscle.
N. Arytenoid cartilages. I. Crico-arytenoidic
postici muscles,  r. Posterior part of cricoid
cartilage.  T, V. Vocal ligaments.
* Miiller's Physiology, by Baly, vol. ii. p. 1005. 
                        ACTION OF MUSCLES.                    749

tory tract, described at page 523, and possesses the same anatomical
characters at many points, being covered by ciliated epithelium.   It
is involuted to a considerable extent, forming numerous glands, which
cover the epiglottis, and are scattered  over the interior of the larynx.
  We have  seen that the cricoid  cartilage may move freely on the
thyroid, or vice versa ; and the  arytenoids may be moved in various
directions on the upper border of the  cricoid.  Moreover, suspended
as it is, loosely in front of the  pharynx and  oesophagus, the whole
apparatus of the larynx  may be moved freely up and down  in  the
neck, approximating, or receding  from the lower jaw.  For these
various movements  the larynx is provided with two sets of muscles—
the extrinsic, by which the whole organ is  moved, and the intrinsic,
destined to regulate the movements of the various  segments.
  The  extrinsic muscles  are those which connect the larynx to  the
sternum below and the hyoid bone above ; the  sterno-thyroid, the
thyro-hyoid, and, indirectly, the  sterno-hyoid, omo-hyoid and stylo-
hyoid, and stylo-pharyngeal muscles.
  The intrinsic muscles are the  crico-thyroidei,  the arytenoidei, the
crico-arytenoidei-postici and laterales,  and the thyro-arytenoidei.  We
must refer to  works on  descriptive anatomy  for the  details  of the
connections of these muscles ; it
must suffice, here, to state  that
their names   denote very  accu-
rately their  attachments to  the
segments  of the  larynx  upon
which they can exert their force.
  Action of Laryngeal Muscles.
—The  arytenoid  cartilages are
attached  by  ligaments  to  the
posterior surface of the cricoid,
which permit a considerable ex-
tent of  rotation upon an articu-
lating  surface  formed  on  the
summit  of the latter;  by  this
arrangement the chordae vocales
may  be  stretched  or  relaxed,
and  the aperture of the glottis
increased or  diminished, accord-
ing to the direction of the force
which acts upon  the arytenoid
cartilages.   The posterior crico-
arytenoid  muscles   render the
vocal chords more tense, but  at
the  same time cause them  to
diverge from each other, and so
the width of the aperture  of the
glottis  is  enlarged.    On   the
other hand,  the thyro-arytenoid
muscles, by  drawing  the  aryte-
noid cartilages towards the thy-
Fig. 213.
 Magnified view of internal parts of larynx of
right side, after Willis, showing actions of laryn-
geal muscles.
 0, P. Axis of articulation of arytenoid carti-
lage.  T.  Direction of  force of thyro-arytenoid
muscle.  X.  Direction  of  force of crico-aryte-
noideus lateralis. W. Of crico-arytenoideus pos-
ticus.  Y. Of arytenoideus transversus.
 B. Crico-arytenoid ligaments  X. Crico-aryte-
noideus lateralis. Q. Crico-arytenoideus posticus.
h. Vocal ligament. 
750
VOICE.
roid, relax the vocal ligaments, while the crico-arytenoidei laterales,
by causing the arytenoid cartilages to rotate inwards upon their axes,
approximate the vocal chords and diminish the aperture of the glottis.
The arytenoid muscle draws the two  cartilages towards  each other,
and so tends to diminish the  aperture of the glottis, especially at its
posterior part.
  These different movements are further accelerated, or  increased
in extent, by the action of certain other intrinsic and extrinsic mus-
cles of the larynx.
  Thus  the  arytenoid cartilages being  fixed by the  contraction  of
the arytenoid and posterior crico-arytenoid muscles, the vocal chords
will be stretched by  the descent of the  thyroid cartilage over the
cricoid, a movement performed by the crico-thyroid and sterno-thy-
roid muscles.  The  thyro-hyoid muscle, by drawing the  thyroid car-
tilage upwards towards the hyoid bone, will  assist the action of the
thyro-arytenoids, and relax the vocal chords.
  By the action of these various muscles, the tension of the vocal
chords may be increased or diminished,  and the size of  the opening
of the glottis regulated at will.
    Modes of altering the aperture of the Glottis and the tension of the Vocal Chords.
Crico-thyroidei.....stretch the vocal chords .  .  .  .  ,        .  ,
„,         ...          f relax and place the vocal chords in 1  y°  c   P1 c
Thyro-arytenoidei  .  .  .  .|  the position for vocalization .  .}-»   of notes-
,.. .         ......         f separate the front  of the "|    open 1
Crico-arytenoideipostici .   .  .   |  arytenoid cartilages .   }   glottis |  govern
„ .     ,    ., . , ,   ,         f press together the front of)         Y aperture
Crico-arytenoidei laterales   .  .  { %he ar%noid cartilages M  close [of
.....                   f press together the back of \ j glottis J  glottis.
  ry enoi ei.......-^ ^ arytenoid cartilages   /

  Nerves.—The  nerves of the larynx are derived from the superior
and inferior laryngeal branches of the vagus.  Those from  the for-
mer are distributed to the mucous membrane, and  to the crico-thyroid
muscles, by the external  laryngeal branch, those from the latter to
all  the other intrinsic muscles of the larynx.   Both these nerves
anastomose with  each other beneath the  mucous membrane, near the
arytenoid muscles.
  The inferior laryngeal or recurrent nerve has relations  to the
innominata  artery on  the right  side, and to the aorta  on the left,
which often implicate it in aneurismal tumors, especially of the latter
artery.  These, by compressing, weaken and  paralyze the  nerve and
the muscles  which it  supplies,  and give rise  to those alterations  of
voice  which  are  sometimes  among the earliest  indications  of the
formation of  an aneurism within  the chest.
  Action of the Larynx and Theory of  Vocalization.—In the little
apparatus of vocal chords attached to movable cartilages and bounded
by  a free space above the laryngeal ventricles, and  by a free space
below the  tube of the trachea, in which they vibrate, are  found the
chief conditions  necessary for the production  of the vocal  sounds
over an extensive though variable range of pitch.
  Although  all physiologists are  agreed that this apparatus is the
seat of the production of vocal sounds, there  has, nevertheless, been 
THEORY OF VOCALIZATION.
751
much difference  of  opinion as to  whether the larynx  should  be
regarded as a stringed instrument, in which the sound depends upon
the vibrations produced by the  movement of the stretched strings,
as a wind  instrument, in  which sounds result from the vibration of
the column  of air within  them, or as a reed instrument which deve-
lops sound by the vibration of one or more highly  vibratile tongues
acted on by a current of air passing over them.
  By the mechanism we have  described, the vocal chords are placed
in a position favourable for the production of sounds  by their vibra-
tion, and the pitch of the sounds so  produced modified.
  Professor Willis showed, that in an ordinary respiration the aper-
ture of the glottis assumed a V form ; and its lips are inclined from
each other; the apex of the V is situated towards  the  thyroid car-
tilage.   When sound is to  be produced,  the lips of the glottis are
made to  approximate each other, and their inner edges become paral-
lel.  If  now a current of air  be forced through the chink, a sound
is produced, the pitch of which depends entirely upon the tension of
the vocal chords.   De Kempelin says, that in the production of sounds
the lips  of the  glottis  are approximated to the one-tenth  or one-
twelfth of an inch.  The  chords in  vocalization vibrate  throughout
their whole  length;  but  no voice-sounds  can  be  produced  by the
passage of air through  the posterior portion  of the chink of the
glottis between  the arytenoid cartilages.  Even when  the chords
are in contact, sound is produced by the forcible transmission of air.
  When  the vocal chords are rendered tense, a high note is produced;
when they are relaxed, a note of low pitch results.  A greater num-
ber of sonorous vibrations  takes place in the former case than in the
latter.   It has been shown, that in the case of stretched strings, the
pitch of the note varies in  direct proportion to the amount of tension,
according to the  law that  the  number of vibrations produced  by
strings of similar length varies in proportion to the square-roots of
the forces which stretch them.   A string stretched by a certain force
will produce twice the number of vibrations, if the force be increased
four times;  or, if  a stretched  string  is caused to vibrate, and so to
produce a certain note, if four times  the force be employed, we obtain
a note which is the octave of  the  first, requiring for  its production
twice the number of vibrations.   These results, however,  cannot be
obtained  upon the larynx, so  that, as Muller  has  proved, the pro-
duction of vocal sounds in this organ cannot be compared with those
produced in a stretched string.
  The distinguished physician, M.  Savart, was among the  most
active  supporters  of the  explanation of the formation  of voice, on
the principle of wind-instruments.   He likened the  larynx to a bird-
call, and referred the exact seat of the development of  sound to the
air contained in the ventricles of the larynx, which would be affected
by the upward current from the trachea, just as the air in the cavity
of the bird-call is by the  current  from  the mouth.  But,  to pass
over the  argument, that it is very doubtful whether  the bird-call can
be referred exclusively to  the  class of wind-instruments, M. Savart's
views are decidedly negatived by the fact that in the class of  rumi- 
752
VOICE.
nants the superior or false vocal ligaments are absent, and, conse-
quently, the ventricle of the larynx.
  Ferrein was the first to show, by experiment, that vibration of the
vocal chords was  the essential cause of  voice.  His  experiments,
published  in 1741, were  performed on  the dead larynx.   By them
he was enabled to  show, that the note varied according to the length
and tension of the vocal chords, the same  laws regulating the  pro-
duction of sound  by these chords as by strings which are thrown
into  sonorous vibrations by currents of air.
  The most important  experiments upon the production of vocal
sounds are those of Professor J. Muller, of Berlin, and of Professor
Willis, of Cambridge.  Muller investigated the action  of membran-
ous bands, or of tongues formed of caoutchouc, in generating sound
under the influence of a current of air.  The human organ of voice
is imitated by a tube, capable of being varied in length; to one end
of this  are applied two  membranous vibrating  tongues, attached to
the wall of the tube, but separated  from each other by a chink,
through which passes the current of air necessary for throwing them
into  sonorous vibrations.   Willis employed a similar instrument.
  The results of these experiments may be thus briefly stated—
  1st. That elastic bands, forming the lateral  boundaries of a chink
through which a current of air is driven by a  pair of bellows, may
be thrown  into vibrations  so  as to  produce sounds which resemble
those of the human voice.
  2d.  That for  such  vocalization it is necessary that these bands
should have, in addition to a certain degree of tension, a particular
position likewise.  This, which is called by Willis the vocalizing posi-
tion, consists in the parallelism of the margins of the  bands.   In
the quiescent state, during breathing,  the  lips  of the glottis are in-
clined from each other;  but in the vocalizing position, or that neces-
sary for the production  of  voice,  they become parallel.  In  the
former  condition,  the  glottis is a triangular  space, with divergent
sides and apex  in front; in  the latter, it becomes a simple slit, or
nearly so, with parallel  sides.  In  the human larynx, the thyro-
arytenoid muscles, lying on the outside of each of the  vocal  chords,
exercise a principal influence in determining their relative position,
and  in adapting them for vocalization.
   3d.  If a tube be adapted to the membranous tongues, in such a man-
ner that the air may play upon them through it, and may pass through
another tube after it  has acted upon  them, an  influence is exercised
not only on the timbre  of the sounds produced, but also  upon the
pitch, which varies with the  length of either  and of both.  In the
human organ of voice, the larynx and bronchi represent a tube pre-
fixed to the membranous tongues and chordae vocales ; and the cavity
in front of the inferior ligaments of the larynx, a tube placed below
the tongues.*

  * The reader is referred for the detail of Miiller's experiments to p. 988 et seq., of
Dr. Baly's Translation, vol. ii., and  to Miiller's separate  work, Ueber Compensation
der phys. KriLfte am menschlich.  Organ—Berlin, 1839. 
PRODUCTION OF VOCAL SOUNDS.
753
Fig. 214.
  The vocal sounds may be produced by blowing air from the trachea
through the aperture  of the  glottis in a larynx  removed from the
dead body; and by adopting means to vary  the tension and the rela-
tive position of the vocal chords, the phenomena of the voice may be
very closely  imitated.   When
air  is  thus blown through the
glottis, the vocal chords being
approximated,  clear  and full
tones are generated.   They are
produced most readily and cer-
tainly when the posterior part
of the glottis, situated between
the  arytenoid  cartilages,  is
closed.  A certain constriction
of  the glottis  appears  neces-
sary, as, when  it is  too open,
an  indistinct noise  is  merely
produced.   The  pitch  of the
note is determined by the ten-
sion of the vocal chords, that
of both being equal; it is not
influenced  by changes in the
width  of  the aperture of the
glottis.  By  increasing  the
weight which   stretches  the
vocal chords, the height of the
notes  is  raised;  On  the Other   Diagram to show parts concerned in vocalization,
i   i.i     i    .•  _   f .!    and the character and shape of cavities above and
hand,  the relaxation  ot the  beiow the vocai  chords.
chords lowers  the   notes:  a
register of about three octaves  may be formed in this way.  Even
after all the parts which lie over the vocal chords have been removed,
these  variations of sound may still be produced.
   The action of the vocal organ in man appears to approach more
nearly to that of a reed  instrument than  to  a  stringed  instrument.
The former is characterized by  being provided with a flexible vibrat-
ing tongue, against which the air can be propelled so as to throw the
tongue into vibration, and to excite a  musical  sound.   Such  is the
mechanism in the organ-pipe, hautboy,  bassoon, accordeon, and other
instruments; the form and disposition  of the tongue, and the mate-
rial of which it is made, differing in each instrument.
   Chest Voice.—In  the larynx, as before  remarked, the note may
be changed, by  varying the  tension of the  vocal chords, provided
 they be parallel and sufficiently close  to each  other.  Wben  a high
 note is to be produced,  the head is raised and the larynx elevated, in
 order that the vocal chords may be rendered  tense; on the  other
 hand, if we wish to sound  a very low note, the chin must  be  de-
 pressed upon the chest, so as to facilitate the relaxation of the vocal
 ligaments.   At the same time,  the strength of  the blast of air exerts
 a considerable influence upon the pitch of the note.   In reed  instru-
 
754
VOICE.
ments, it has been found that the note can be rendered higher by in-
creasing the force of the blast.
  Falsetto Notes.—The sounds  to which we have  been referring are
produced solely by the vibration of the chordae vocales ; modified no
doubt by the epiglottis, soft palate,  etc.,  and the laryngeal cavity
below.  These notes are all termed  chest notes ; but  in man  tones
can be generated very different  from  those which can be imitated by
experiments upon the  dead larynx.   These are the falsetto notes.
The precise mode of  their production is obscure.   From the experi-
ments of Muller and Lehfeldt, it is probable that these falsetto notes
are produced by the  vibration of the inner portion of the borders of
the vocal ligaments solely.  Magendie and Mayo accounted for them
upon  the view, that only half the  length of the chords was thrown
into vibration.
  Mr. Bishop has shown, that  in the transition from the chest note
to the falsetto note the crico-thyroid chink opens, having been closed
immediately before, during the  production of the highest note of the
chest  voice; so that  the vocal  ligaments become relaxed;  a change
which necessarily follows must  take  place, if they are to produce a
similar note, by  vibrating only  along half their length.
  Singing.—In  singing, a certain succession of tones is produced in
definite order by altering the  character  of the glottis, just  as by
varying the conditions  under which the air is thrown into vibrations
in musical instruments we are  enabled  to  alter the nature of the
note.
  The different varieties of the voice are arranged according to the
pitch, which depends upon the  length  and other conditions of the
vocal  ligaments, and  they are  comprised in the following classes:
Bass, Tenor, Alto or Contralto, Soprano; the two former belonging
to the male, and the  two latter to the female sex.  Besides these,
the Barytone is placed between the Bass and Tenor, and the mezzo-
Soprano between the Soprano and Contralto.   The compass of the
voice  varies from one to three octaves.  Few singers possess a greater
range  of  voice  than the  latter, but some  of the most celebrated
have much exceeded this—Catalani's voice included three and a half
octaves.  The compass of each  kind  of voice is shown  in the follow-
ing table :—
                                         Soprano.
                             |  Contralto.                     I

  CDEFGABC'D'E'F'G'A'B^DSE^G^B^D^F^A^LW
         |      Bass.______________
                    Tenor.

  Before puberty, the pitch of the male and female voice is  nearly
the same; but at this period the larynx of the male  becomes larger
and more prominent, and the vocal ligaments elongated, in virtue of
which changes the pitch falls an octave in extent.  In  eunuchs this
alteration does not take place, and they retain the puerile character
of voice, which is, nevertheless, louder and stronger than in women. 
SINGING.
755
In men  the vocal  chords are one-third longer than in women, and
the larynx is altogether much larger.
   Unlike musical instruments, the human voice is  capable of pro-
ducing a vast number of  notes, intermediate between the successive
tones; and Dodart estimates  the  number of these which can be ap-
preciated by the ear  at three  hundred.
   Influence of the Nerves on  Voice.—The inferior laryngeal and the
crico-thyroid branch  of  the  superior laryngeal, from the pneumo-
gastric, are the sole channels  through which the  operations  of the
will affect the mechanism concerned in the production of the voice-
sounds, and as occurs in  the  case  of other muscles, the movements
of those  muscles whose office it is to regulate the tension of the vocal
chords, and govern the aperture of the  glottis, are much more rapid
and perfect, much more under the control  of  the will,  and capable
of executing more delicate movements in some persons than in others;
and hence the wide difference  between individuals  as  to their capa-
city for singing  and  vocalization.  Something in the  difference of
vocalizing power is due to minute and inappreciable differences in the
length of the vocal chords—size of  glottis—quantity of the  elastic
vocal  chord tissue—of the mucous membrane (slight  affections of
which create hoarseness).
   The movements  of the laryngeal muscles, as are the movements
of respiration,  are much  influenced by mental emotions.   In  laugh-
ter,  crying, sobbing, we have a combined  excitement of respiratory
and vocal actions.
   In health, the emotions of grief, joy, and  surprise,  affect both
voice and speech—the latter more  frequently and intensely than the
former.  Diseases which  involve  more or  less disturbance  of the
centre of  emotions, affect both voice  and  speech.   Hysteria, and
chorea, may be referred to, the former generally affecting the  pro-
duction of voice, the latter of speech.
   In certain affections of  the brain, speech is impaired or  altogether
destroyed, or at  most limited  to a monosyllable,  Yes or No.  This
occurs under  various conditions;  sometimes in consequence of  a
chronic disease, sometimes of a shock : a diseased state of the convo-
lutions or hemispheres is the most frequent concomitant of this symp-
tom, but no precise part  of  the brain  can be assigned as a special
organ of speech.
   In many diseases  of a spasmodic  or convulsive character, the action
of the muscles of the  larynx is affected.   In  the spasmodic croup or
crowing inspiration of children, the chink of the glottis is frequently
so firmly closed, and for so long a time as  to  endanger life.   The
peculiar  "hoop" of  hooping-cough, and the  curious voice-sounds
so common and so varied in hysteria, show that  either these  nerves
themselves  or  the  precise part of the centre with  which they are
connected, are influenced  by the morbid action.  In chorea the same
want of  power  of  co-ordinating the movements is  observed in the
little muscles of the larynx as  in those which preside  over the move-
ments of the limbs and other organs.
   In some of the conditions to which we have referred, it is difficult 
756
VOICE.
to say whether  the  motor nerve or its central origin is affected, or
whether the disturbance is not excited in the centre through the in-
fluence  of an afferent nerve. Anything irritating the delicate mucous
membrane of the larynx creates violent  spasmodic action of  the
muscles of the glottis, in which those of respiration frequently take
part, through the medium of the afferent superior laryngeal nerve.
   Pressure upon the inferior laryngeal excites spasmodic cough, which
often forms an  important symptom of aneurism, or of mediastinal
tumor.   Section or  disease of the  inferior or laryngeal nerve com-
pletely  destroys the power of vocalization.
   Stammering,  at least in the  greater number of instances,  is an
affection of the  nervous system, not of the articulating  organs.   It
consists  in a defective control over the will, and an imperfect power
of  co-ordinating the  muscles  of  speech.   Stammering  is  much
increased by any mental excitement, sudden surprise, etc., and one
of the most important points to be  kept in view, in the treatment of
this condition, is to avoid all cause  of excitement to the patient, and
to prevent him from thinking  about his  condition as much as possi-
ble,  so that he may gradually obtain that command  over the move-
ments of the muscles which is required for conversation.
   Speech.—In the vocal apparatus,  notes of very various pitch can be
produced at will.  The different sounds of voice have been shown to
be due  to variations in the size of  the aperture of the glottis, and
in the tension of the chordae vocales.  The vocal organ, however,
is not capable of producing those articulate sounds by which we are
enabled  to communicate  to each other our ideas; but this end is
obtained by an  alteration taking place in  the  cavity situated above
the glottis, and in the position of the organs which it contains.
  The most important conditions affecting speech  are, first, the size
of the oral  aperture; secondly, the size of the buccal cavity; and
thirdly, the position of the tongue.
  The production of vowel sounds, which  are  continuous, and can
be prolonged  at will, depends entirely upon the size of the buccal
cavity and outlet.   In the sound of the a in ah, these are opened to
their widest  extent, while in sounding a  in fate,  the buccal cavity
requires  to be much reduced  in size,  by  the lateral expansion and
elevation of the tongue.  When we sound  the e  in me, cavity and
outlet are made still less.   The o in no, results from a still further
diminution of the oral aperture, while the buccal cavity is much
increased; and in the oo in boot, the former is contracted to a  mini-
mum, and the latter increased to its largest size.
  The sounds just enumerated  are the vowel sounds of continental
languages, and they can all be prolonged  for  a time  limited only
by the passage  of the  air through  the vocal apparatus.  The  Eng-
lish * may be looked upon as a diphthongal sound,  and, like the true
diphthongs, cannot be prolonged like a continued vowel  sound.  The
diphthongal sounds appear to be produced by causing one particular
vowel sound  to pass into another with  a  considerable  degree  of
rapidity, thus:  ou is formed by  the transition of the a mfar to the
oo in cool. 
SECRETION.
757
  In the pronunciation of consonants, the soft palate, the tongue and
lips more especially, take part; and in order to produce many of the
sounds, it is necessary that the air should be forced through the pas-
sages suddenly, and often with a  considerable degree of force,  while
others can be produced as continuous sounds, like the vowels; hence
the divisions into explosive and continuous consonants.
  The former class includes  the  b, p, d, t, g, k, the latter, the v, f,
1, m, n, r, the sibilant consonants  s  and z, and the Greek 8 (theta) th,
which, like sh, is a perfectly simple sound, and might be represented
by one letter.   The manner in which these sounds are produced, by
the alteration of the position of the organs concerned in the  produc-
tion of speech,  can be studied  by every one in  his own person ; but
for a full description of the position of  the several parts concerned
in producing them, the reader is referred  to the works enumerated
at the end of the present chapter.

  For information upon the subjects treated of in the present chapter, the student ia
referred to the following works: Dissertatio de Loquela, 1700; Rev. Mr. Willis in the
"Cambridge Philosophical Transactions," vol. iv., 1832; Lauth, "Mem. de l'Acade-
mie Royale de Medecine," 1835; J. Muller, "Elements of Physiology," translated by
Dr. Baly; Articles "Larynx" and "Voice," by Mr. Bishop, in the Cyclopaedia of
Anatomy and Physiology.
                       CHAPTER  XXXII.

ON  SECRETION.—SECRETIONS  AND  EXCRETIONS.—SECRETIONS WHICH
  ARE EXCREMENTITIOUS.--SECRETIONS WHICH ARE  NOT  EXCREMEN-
  TITIOUS, WHICH SERVE  ULTERIOR PURPOSES.—VICARIOUS  SECRE-
  TIoN.—INGESTA AND  EGESTA.—ANATOMY  OF SECRETING  ORGANS
  GENERALLY.—OF THE  GLAND-CELL.—OF THE DUCTS OF GLANDS.

  The function of secretion is that by which organized bodies sepa-
rate from some portion of their internal or  external surfaces a ma-
terial which  thereby becomes free or loose, and capable of removal,
and which is likewise commonly known as  the secretion from such
surfaces.   It is not  sufficient that this  material  should be separated
simply from the blood ;  for, if this were so,  all the tissues would be
secretions;  but it must  also be separated from a tissue of a special
kind, hence known as a  secreting tissue.  The blood, then, furnishes
the materials which  are  to form the  secretions ; but certain  tissues
are required, without which, these materials could not become secreted
products :  and the secreting  tissues  are anatomically arranged so as
to have one surface  adapted to set free, in the form  of secretions, the
materials derived: on the opposite surface from the blood.
  A secretion may  be solid or fluid, living or dead, near to, or  dis-
tant from, the constituents of the tissues in chemical constitution,
capable of re-entering the blood, and  being further  serviceable in
       49 
758
SECRETION.
the economy, or requiring to be expelled from the  system as useless
or hurtful.   Thus, a great  variety of very dissimilar  products  are
conveniently classed together as secretions, in virtue of  their being
separated from the body by tissues provided for that purpose.
  Excretions.—Some secretions consist mainly of substances result-
ing from the waste of the tissues  coincident with their nutrition or
renewal, and which are  thrown off from the blood  through the se-
creting  surfaces almost as soon as the capillaries receive them from
the tissues.   Such are the urine, and portions  of those matters which
escape in the form of faeces ; and, allied to  these, is  the carbonic
acid, which is eliminated, without  the  intervention of a  true secre-
ting tissue, directly from the capillaries  of   the  lungs.   If these
matters were retained,  they would accumulate  in  the  blood  and
tissues,  and prove, sooner or later, incompatible with life;  and even
a simple  delay or  retardation in the process of their removal, to
whatever cause it may be attributable, must be attended  with grave
consequences to health.  It is, therefore, impossible to over-estimate
the importance of distinguishing these products from other secre-
tions, and of acquiring the  habit of considering them  under  one
common head.  They are known  as the excrementitious secretions,
or,  simply as excretions.
  The  kidneys are organs  through  which a large portion of  the
blood is constantly flowing,  and in which the  general  mass of that
fluid becomes so far purified as to be freed from certain waste  ma-
terials which have just been thrown into it by  the muscular and other
tissues.   The blood which leaves the kidneys, though rendered venous
by the  nutrition  of the glandular tissue itself,  is more free than
before to receive  the refuse  of the other parts.  Hence the kidneys
must be regarded as a depurating organ, subservient to the functions
of other parts of the frame.  To  prove this,  it is  only necessary to
extirpate the kidneys from an animal, or to see their function arrested
by disease :  in either case, the blood and tissues become more  and
more loaded by the urinary  matters which  continue to  be formed in
the body, and which should  have been eliminated as soon as formed
by the extirpated or diseased organs.  So essential, indeed, to animal
life, is this excretion of nitrogenized matters, resulting from the waste
of the nitrogenous tissues, that it may be safely said to be universally
present, and to have a  kidney, or analogous  organ, assigned to it,
wherever animals  exist having  an arrangement  of  different  and
mutually dependent parts, on such a  scale as to  render the direct
expulsion of the waste materials at the points where they are formed
impossible.
  The  principal  excretions  maybe thus enumerated:   1.  carbonic
acid gas, formed  by the action  of the oxygen upon carbon,  and
separated by the lungs; its accumulation in the blood is very rapidly
fatal to life.   2.  Urea,  uric  acid  (in herbivorous  animals  hippuric
acid), kreatine, and Creatinine: all nitrogenized principles of definite
composition, resulting principally  from the waste of the tissues,  and
eliminated by the kidneys;  their retention in the blood is soon, but
less rapidly, fatal.  3. Various saline matters, separated  by the  kid- 
RECREMENTITIOUS SECRETIONS.
759
neys  and skin.  4. Lactic  acid, principally by the  skin.   5.  Cer-
tain portions of the bile, already  considered  (see p.  602), by the
liver.  To these may  be added  sundry  constituents of the fasces,
of imperfectly known composition, but supposed by Liebig to be im-
perfectly  oxidized  matter,*  escaping by  the mucous lining of the
intestinal tract, probably by the tubes of Lieberkuhn and  by the
Bolitary glands; and lastly, also, whatever substances are taken in
as food and absorbed into the blood, but which  fail to be assimilated,
either from their being superfluous in quantity, or incapable of serving
any purpose in the economy.
   Secretions which are not composed of excrementitious substances,
and which serve important offices in  the economy.—Other  secretions
(and  this is a large  and  diversified class)  do  not consist  of waste
materials,  the results of  the disintegration of the tissues, but are
thrown off in certain situations where they are to perform a part
useful or necessary to the protection or preservation of other organs,
or of the whole body, or of the species.  Of these, speaking generally,
it may be said that  they are formed, as  well  as eliminated, by the
several organs which furnish  them; that they retain  more  or less
resemblance, in chemical constitution, to the food and the nutritious
parts of the blood;  and  that, in  many respects, they are allied to
the living tissues of the body from which they are  separated.
   The highest example which  can be given of  these qualities is that
of the male and female elements, the semen and the ova, which go
to form  the new being, and which  are the production  of organs es-
sentially secreting.   Here the secreted  matter retains  its organized
form  and its living  properties, which latter are of  so elevated a
character, as to end in the development of an entire organism like
that which has furnished the secretion.
   Other examples, in which these qualities  meet less  decidedly, are
presented by the milk, and  by some of those secretions which  have
been  already considered under the head of the digestive function, such
as the saliva, the gastric juice, and the pancreatic fluid.   These are
poured out to mingle  with the food, and variously to facilitate its
entry into the blood; and there can be no doubt, that after having
duly  effected this  object, they become  in a  considerable  measure
themselves  reabsorbed  with the food, so as to  be further serviceable
for a time in the ever-moving circle of the functions  of vegetative
life.   There is no waste here;  and we may suppose that they d) not
become finally  expelled  until  they  have  been  reduced to  forms of
combination in which they  can no longer minister to the life of the
tissues.   Such secretions  are conveniently classed together as recre-
mentitious.
   But it would be an  error to suppose  that all matters separated
from the natural  surfaces of  the body fall exclusively under one of

  * The faeces have lately been subjected to  chemical investigation by Dr. W. Marcet,
who has discovered an organic crystalline substance of an alkaline reaction, to which he
gives the name of Exaretine, an acid olive-coloured substance of a fatty nature, Ex-
crelolic acid, and a fatty acid, having the properties of Margaric acid, but not con-
stantly present.—" Proceedings of the Royal Society," vol. vii. No. 6. 
760
SECRETION.
the foregoing heads; on the contrary, it happens in some cases that
a secreted product is  of  a mixed kind, partly excrementitious  and
partly recrementitious—partly rejected as  needless  or  injurious—
partly thrown off that  it may subsequently fulfil a useful purpose in
the economy of the individual and species.   Thus the bile  contains
certain matters which are expelled with the excrements, while a large
proportion of its  elements is reabsorbed in the blood,  after their
commixture with  the chyme  in  the intestines, and  thus  furnishes
material for the production of animal heat in respiration.
  The chief  secretions serving an  ulterior purpose,  and which  are
thrown  out with  that object, are  the  following: The generative
elements—the milk, the salivary, the  gastric, pancreatic, and allied
fluids ; parts of the biliary fluid;  the mucus from some surfaces;  the
epidermis  and its  appendages from  the skin ;  the  sebaceous  and
odoriferous matters from certain glands; the tears.
   Water,  as  it forms a necessary part of the living frame, and is
probably  in  constant course  of  formation  within it, and  as it is,
besides, continually received  in large quantities as food  and  drink,
is a constant ingredient of the secretions, being thrown off especially
by  the lungs, skin, and  kidneys.  By the two former its loss is
determined, in a great degree, by simple evaporation into the sur-
rounding  air; and this is  necessarily influenced much by the hygro-
metric state and  other conditions of that medium.   By the latter,
whose office  is complemental of that  of the preceding,  a special
apparatus is  furnished for draining off the water, while this fluid is
made useful in extracting the ingredients of the most important of
the excretions from the surface over which  it is  subsequently made
to flow.
   Vicarious  Secretion.—It has been remarked, that  there is  a  sort
of compensating action between the skin and kidneys in the normal
condition  of  the system, dependent upon variations in temperature
and other conditions.   A similar power exists,  in  a more limited
extent, in other secreting structures, by virtue of which one organ
may take  upon itself the work of another, whose healthy function
has been temporarily suspended or impaired by disease.  Advantage
is taken of this circumstance in the treatment of kidney diseases, in
which the functions of those  organs are temporarily or permanently
impaired.   In such cases, the removal of the urinary constituents is
promoted  through  the skin,  or  from the intestinal tube, by giving
purgative  medicines, and by promoting secretions.   The  excretion of
biliary matter in the urine in  cases of jaundice, and  the separation
of the menstrual  fluid from  the  mucous membrane of the lungs or
stomach, are  familiar examples of this vicarious action.   Very nume-
rous cases of metastasis of the urinary secretion  are  on  record ;  and
elements  of the urine have been  met  with in vomit, in the  stools, in
the tears, and secretions of the ears and nose ; in the milk, and upon
the cutaneous surface generally,  particularly about the navel.
   If the  kidneys  of an  animal  be extirpated, the elements  of the
urine may be detected  in  many situations in which they  are not nor-
mally present.  In disease, when the  functions of the  kidneys are 
INGESTA AND EGESTA.
761
much impaired, it is not uncommon for the elements of the urine to
pass off from the stomach by vomiting.
  Ingesta and Egesta.—It is obvious, that if the weight of the body
remains the same, the quantity of matter removed  by the  different
excretory channels will exactly correspond  to the ingesta, although
the arrangement of the elements will be changed.
  The proportion in which the different elements entering  into  the
composition of the food are removed by  the  various secreting organs
is shown in the following table, the result of some excellent experi-
ments of  M. Barral:
          Ingested as Food.

Carbon   .   .   21,770-4 grs.
Nitrogen  .   .    1,649-0
Hydrogen .   .    3,370-6
Oxygen   .   .   16,446-7

Total     .   .    43,236-7         2,594-0     1,530-1        39,112-6

  The quantity of water  removed from the body was usually one-
fifth or one-sixth  more than that  taken  in, showing that water is
really produced in the organism.
   General  View of the Anatomical Plan of Secreting Organs.—We
have said that the secreting tissues are arranged in such a manner
in the body as to have an external anatomical  position, so  as  to be
able to set free the secreted  product when formed.   Some organs of
a strictly secreting kind,  pour their material directly into the blood.
It appears most reasonable to regard the whole lymphatic system as
an apparatus of this description, calculated not merely to  restore to
the  circulating current the superfluous or altered plasma, thrown by
the capillaries  into the interstices of the tissues, but destined  by its
glandular parts especially to act  on the passing fluid, and to pour
into it additional secreted matters, which pass  by the efferent vessels
to blend with the general mass of blood.   The inner surface  of the
lymphatic vessels is here  the external free surface, to which we refer
as that from which the secretion is liberated.*
   Again,  there are  other  organs, viz.,  the  synovial  and  serous
membranes, which  are  usually  and  correctly classed as secreting
organs.  They have been  already described (p. 126).  The fluid they
secrete seems  furnished for  the purpose of lubricating their surface,
so as to facilitate motion.  It, consequently, does not leave the sur-
face on which  it becomes free, but remains in  contact with it,  and
only undergoes the same  slow  renewal and  absorption, as all  other
solids and  fluids with which blood  in  motion is brought into close
contiguity.  We have no reason to suppose that the effusions on these
surfaces suffer much deterioration by their continued contact.   They
appear to  differ  but slightly from the  serum of  the  blood, contain
the same saline matters in solution, and in nearly the same  propor-
tions.  The epithelium of these surfaces  is no  doubt concerned in

  * This view results from Professor Goodsir's anatomical researches, and from con-
siderations which have been ably stated by Dr. Carpenter.—See ante, p. 615.
1060-7       798-3        19,911-4
 756-6       1420          750-4
 213-1       1220         3,035 5
 563-6       467-8        15,415-3 
762
SECRETION.
furnishing these fluids, but  exerts  little  catalytic  power  over the
liquor  sanguinis,  which,  consequently,  is little  altered by being
secreted.   Mr. Rainey has well pointed  out  that  the  epithelium in
certain situations is developed in a particular manner upon  the pro-
jecting folds and fringes of  synovial membrane, known as glands of
Havers;  and  has shown  it to be probable that the  viscid synovia
owes its origin chiefly to the surface of these parts.   He has found
this disposition not only in the joints, but also in the sheaths of ten-
dons, and in the bursse mucosae.*
   But, dismissing these structures, we arrive  at  that great system
of parts,  which  we have  before designated  the mucous system,  in-
cluding, under one common  title, the skin, mucous membranes, and
true glands;   the term true glands, meaning  those which, by a duct,
or otherwise, pour their secretion  on the external surface, and not
into tho blood.  For a summary account of  the tissues forming this
order of parts, the note at p. 522  of the present volume should be
referred to.   The  skin, and most of the great regions of the mucous
membranes, together  with some of the glands, have  been  already
minutely described in different parts of the preceding pages; and it
now only  remains, before  passing to a description, in  detail, of the
great remaining glands,  to  offer  some  observations on the general
plan or scheme of structure, discoverable in these  special organs of
secretion.
   Between skin, mucous  membranes, and  glands, there exists every
gradation of structure, by which one can be  conceived to pass into
the other.  They  are modifications of a  common type.   The two
former are secreting organs, in an expanded form, sometimes pre-
senting glandular involutions  in  their thickness.  But, in propor-
tion as the glands  differ from mere membranes, we find them assum-
ing a more solid form, gathered up, as it were, into a  more compact
mass, in which are to be still recognized all  the elements of the simple
membrane in  their true  relative  positions—the free  surface being
still the free  surface, though now forming,  it may be the lining of
ducts,  and composing the internal tubular,  or follicular recesses of
the solid  organ—and the deep, or vascular  surface preserving the
same relation  as before  to bloodvessels, lymphatics, nerves,  or areo-
lar tissue, under its various  modifications.  In particular the epithe-
lium, or proper  glandular tissue,  remains  capable by  its anatomical
position in regard to the external surface, to discharge its product
on that  surface.  Thus  the  epithelium  of the parotid gland,  the
liver, or the  kidney, has  such  a relation to  the remote parts of  the
excretory ducts  of those organs, as that the secretion, resulting from
the mutual action  of that  tissue and the blood, is  set free into those
channels,  which are in reality, continuations of the integument, and
therefore, in one sense, portions of the external surface of the body.
   It will be readily seen how close and intimate must be, in all cases,
the proximity  of the glandular epithelium  to the ducts.   In fact, in
many  instances, the epithelium of the  ducts is beyond doubt  the
* Proceedings of the Royal Society, May 7, 1846. 
STRUCTURE OF GLANDS.
763
secreting tissue, and  the gland is a congeries of finely divided  pas-
sages,  or ducts, whose  epithelium  (though  in  a modified  form)  is
directly  continuous with that of the  outer  surface, on  which the
duct opens.   This, for  example, is the case in the sweat glands,
in the sebaceous glands, already described (pp. 368, 369,), and in
the kidney.   But  in other instances, whether owing  to the form
assumed by  the terminal extremities  of the  duct,  or  to  an actual
difference  in the  arrangement of  the  glandular  epithelium,  the
greatest difficulty  exists in determining  the  exact nature  of  the
anatomical relation of the glandular and ductal epithelium,  and  of
ascertaining  whether they are  continuous at all times or only at cer-
tain periods  when  the secretion is discharged.   For example, in the
salivary glands, the pancreas,  and some others, the terminal parts
of  the gland are vesicular, while the ducts are tubular.   Vesicular
terminations of the ducts may be rendered  apparent  by mercurial
injection;  but it is by no means easy to demonstrate the permanent
continuity of the epithelium lining or filling these vesicles with that
which  lines the ducts.
   It is probable that most or all gland follicles were originally closed
vesicles.  This has been shown  by  Dr. Allen Thompson to be the
case in the early condition of the gastric glands; and Henle applies
this view to  other  gland-structures.   In his beautiful investigations
upon  the  testicle  of  Squalus Cornubicus,  Professor  Goodsir  has
shown that the  primary or mother cells are developed by the growth
of isolated nucleated cells attached to the side
of the  duct.   These cells grow and become the
future acini, being connected with  this duct
by a hollow  pedicle; in  their interior, second-
ary cells, in  which the spermatozoa are deve-
loped, appear.   Still the  mother  cell  is  a
closed cavity, and  separated from the duct by
its original  wall.  At  length it gives way
at  this point and  discharges  its progeny of
cells,  containing spermatozoa, into the duct.
 The follicles then appear to become atrophied.
There is another class of gland-structures in
which, according to this view, the mother cell
remains persistent after it has  discharged  its
first progeny of cells, and  continues  to pro-
 duce successive generations of cells ;  the deve-
lopment  of   these  cells  commencing  at  the
 cascal extremity of the follicle.  The point at
 which they originate  is looked upon by Pro-
 fessor  Goodsir  as the  persistent nucleus of
the original   parent cell; and it is termed  by
him, the "germinal centre."  Although it  is
scarcely possible to demonstrate the existence
of this germinal  centre in  the gland-follicle,
there  are many instances in which  this view
certainly  appears  to  be borne  out  by  the
Fi«r. 215.
Cajcal biliary tube of Cray-fish.
At a, b, c, d, e, are shown cells
in different stages as they ad-
vance from the lower part to-
wards the outlet. After Leidy,
/ 
764
SECRETION.
structure  of the  part when subjected to a careful microscopical ex-
amination.  In the accompanying drawing of one of the caecal tubes
of the liver of the cray-fish (astacus affinis), after Leidy, the gradual
transition from the granular matter at  the  bottom of the follicle to
the perfectly formed cells which are being discharged from its sum-
mit is well seen.
  In the  glandules of Peyer,  already  described (ante, p.  581), it
would  seem that vesicles form underneath, but in immediate con-
tiguity with, the mucous membrane, and, becoming filled with glandu-
lar contents, having the nature of nuclei, exhibit a great proneness
to burst, and liberate their contents, perhaps periodically, on  the
free surface of the membrane.  The ova,  too,  are very generally
elaborated in the first instance in a matrix, or stroma, placed  beneath,
and not upon, the  surface  from  which they are to  be discharged.
But notwithstanding  these  differences, which  will be further  con-
sidered, it must be borne in mind that  the gland-cells, or secreting
elements, in the  true glands, are always  so placed as to be able to
discharge themselves or their products on the outer surface.
   Of the  Grland-Cell.—The gland-cells  select and separate from the
blood the substances which form their secreted  product.  These ele-
ments form, in fact, in a certain sense, a part of the food or  pabulum
of these secreting cells, which  is set free when the cell  has  arrived
at maturity, either by its rupture or by its complete detachment from
the surface upon  which it has grown, or, as occurs in  other instances
merely by transudation  through its walls upon one side, while new
matter is supplied to  it from the plasma upon  the other.  Thus the
function of  secretion bears a  certain  analogy  to nutrition.   The
cells in both processes select from the blood certain elements adapted
for their  growth  ; but in secretion, these separate products, after
having  probably  undergone some changes in  the cell, are destined
soon to be cast off, and no longer form an integral part of the organ-
ism ; while, in nutrition, these elements serve to keep up the inte-
grity of the structure by which  they  have been appropriated.   It
may be remarked that the period of existence  of the  secreting cell,
or the length of its  life,  varies  considerably in different  organs.
Sometimes a very short time is sufficient for its development, growth
and decay, while  in other instances, it may persist for a long period
of  time.  Some  of the  most  important  modifications of secreting
cells will  be described  under the head  of the glands, into the com-
position of which they enter.
   Of the Ducts  of Glands.—Ducts are  tubular, usually branched
passages,  forming continuations between the secreting tissue of the
glands and the  surface  of skin,  or  mucous  membrane, on which
the secretion  is  eventually poured.  They are a  contrivance by
which a large mass of secreting tissue, packed in  a small solid space,
can  discharge its product at a given  point.  They  often  present
dilatations, wherein the  secretion  may  be delayed for  a time, and
where, in many instances, it may undergo changes;  and they very
commonly contain a layer  of  unstriped  muscle in their walls, by
whose  agency their contents are  propelled  in  the  proper direction, 
OF THE DUCTS OF GLANDS.
765
often against gravity.   This contractile tissue is sometimes developed
at their orifice into a sphincter muscle.  It is only the minuter
glands which open directly on a surface (e. g., those of Lieberkiihn
or Grew, in the intestinal mucous membrane), which are without  a
duct.
   The  walls of  ducts  present  most internally, an  epithelium and
basement tissue, continuous with those of the skin or mucous mem-
brane.   Outside,  there are (when present)  the  muscular coat and
the  areolar tissue,  which  is prolonged  upon  their exterior in  a
modified form.   Bloodvessels and nerves ramify upon and within the
latter coats.   We owe the best description of the anatomy of ducts
to Henle.
   The epithelium may vary from the scaly to the columnar or gland-
ular variety, and it is sometimes ciliated.   The most common  is the
columnar, particularly in large ducts.  In immediate connection with
the proper mucous tissue,  comes the muscular element, arranged in
two sets of fibres, one longitudinal,  the other circular, of  which the
latter can usually be seen  to be the  more internal.   The fibrous ele-
ments are commonly nucleated,  and  resemble those of  the muscular
coats of bloodvessels;  then follows  areolar tissue, forming an outer
coat,  together with bloodvessels and  nerves.   The areolar  coat gives
Btrength, toughness, and elasticity to the duct; the bloodvessels serve
for its  nourishment, and  the nerves supply  its  muscular coat, and
endow it with  a peculiar sensibility, which, under particular circum-
stances  of pressure or  detention (as in the  passage  of a biliary or
urinary calculus),  may rise to the height of the most exquisite pain,
reacting fearfully on the whole nervous system.
   The smaller ducts very generally are without muscular parietes,
and  are reduced to a homogeneous  basement membrane, lined with
epithelium.  Indeed, there  is reason to believe that, in some cases,
the very smallest consist either of simple epithelium or of mere base-
ment tissue.   The lobular passages  of the lungs are an example of
this latter constitution.
   It  is  not difficult to prove that  the larger ducts are  muscular.
Take, for example, the  ureter.   Open a small animal, just killed for
the purpose, and this canal will be seen to present occasional  peris-
taltic contractions, passing rapidly from the  kidney to the bladder,
which may be  easily excited by a  mechanical or galvanic  irritation,
if they  do not  appear spontaneously.  Besides this  peristalsis, they
undoubtedly undergo, like  the bloodvessels, a slow and  uniform dila-
tation and narrowing,  according  to  the bulk of their contents  or
other conditions.
   In  some of those dilatations of the gland-ducts, which are provided
for a  temporary reception of the secretion, such as the urinary blad-
der and the vesiculse  seminales, the muscular  coat  attains such  a
thickness as to allow of being  readily shown.  The muscularity of
the coats of the urethra was demonstrated, for the first time, some
years ago, by Mr. Hancock.  In the  gall-bladder, muscle is certainly
developed to a far  less extent; but even here, Dr. G. H.  Meyer
states that, by  means of a powerful  galvanic battery, he has  caused 
766
SECRETING GLANDS.
this  receptacle in the ox to contract, so as to diminish its capacity
one-fourth.   The  Fallopian tubes, uterus,  and  vagina, are  parts
rightly  falling under the  head of gland-ducts, though  wonderfully
modified in accordance  with  the  functions  they have  to  perform.
The  uterus in particular,  under the condition of pregnancy,  offers
an  example of the  highest development  of the  involuntary  or
unstriped muscular fibre-cells anywhere  met with.
  We  shall now proceed with a description  of those glands which
have not yet been treated of.  Of those  pertaining to the alimentary
canal,  the salivary glands and  their  secretion  (p.  539),  and  the
secretion  of the  pancreas (p. 592) and the  liver  (p. 600), have
been already  spoken of, and the  structure only  of the two  latter
remains to be considered.   The kidneys and their secretion will  fol-
low; and we shall defer the consideration of the glands relating to
the reproductive function  to  the  chapters  devoted  to  that subject.
Such are  the  ovaries, the  testes, the prostate, Cowper's glands,  the
mammae.

  The following  works may be  consulted  upon the subject of  secretion: Articles,
" Secretion" and " Mucous Membrane," in the Cyclopaedia of Anatomy and Physio-
logy; "Anatomical and Pathological Observations," Professor Goodsir, 1845; "Lec-
tures on  Nutrition," Professor Paget; Medical Gazette, 1847; Principles of Human
Physiology," Dr. Carpenter.
                      CHAPTER XXXIII.

SECRETING GLANDS.—OF THE PANCREAS.—OF THE LIVER.—THE LIVER
  IN  INVERTEBRATA.—LOBULES OF THE LIVER.--PORTAL CANALS.—
  PORTAL VEIN.—HEPATIC ARTERY.--HEPATIC DUCT.--GALL BLADDER.
  —HEPATIC  VEIN.—NERVES AND LYMPHATICS.—LIVER CELLS.—OF
  THE CONNECTION OF THE SMALLEST DUCTS WITH THE LIVER CELLS.
  —OF THE PASSAGE OF THE BILE INTO THE DUCTS.—OF THE QUAN-
  TITY AND USES OF THE  BILE.

  Of the Pancreas.—This is a large  gland, placed  across the spine,
behind  the stomach, in physiological relation with  the duodenum or
the first portion of the intestine.  It is flattened from before  back-
wards.  Its left extremity, or tail, tapers off towards the spleen ; its
right  extremity, or head,  is much  larger, lying close within the  curve
of the duodenum, and presenting  a recurved extremity following the
lower portion  of that intestine, and sometimes termed the lesser pan-
creas.  The ordinary weight of the pancreas, according  to Cruveil-
hier,  is from 2 to 2| ounces, but may rise to 6 ounces.  Its colour
is gray, inclining to  pink.
  The  pancreas,  like  the salivary glands, is  imbedded in areolar
tissue, and receives its blood from several neighbouring  vessels.  Its
arteries are derived  from the splenic and  hepatic branches of  the 
LIVER.
767
cceliac axis, and from  the superior  mesenteric.  The blood is re-
turned by the corresponding veins into the vena porta.  Its nerves
come from the solar plexus.
  In structure, the pancreas appears to resemble the salivary glands.
It is subdivided into lobules separated by septa of areolar tissue, which
dip inwards from  that which  forms a common envelop to the whole
gland.  The lobules  are  subdivided  into smaller parts by  similar,
but  less complete  and more delicate inflections of the areolar tissue;
and these minute  ultimate granulations or acini of the gland, corre-
spond to  the terminal extremities of the common duct.  The excre-
tory duct  is concealed within the substance of the gland, and takes
a course  from the left to the right extremity, receiving very nume-
rous  tributaries on its way, and  thus increasing in size, till it joins
the common bile duct, close to its entrance  into the duodenum.   At
its termination it is as large as a crow-quill.  Its coats are  thin and
extensible, its internal surface smooth.  It frequently happens  that
the duct belonging to the lower end of the curved portion or lesser pan-
creas opens separately into the intestine.  In the rabbit the pancreatic
duct opens by a separate orifice, sixteen or  seventeen  inches lower
down the  intestine than the bile duct (p. 595).
  It  is not difficult to inject  the duct, and  through it the ultimate
secreting  structure of the  pancreas,  with  mercury.  This  may be
best done in some of the smaller mammalia, where the glandular
tissue is disseminated in lamellated grains between the layers of  the
mesentery, and where consequently the ramifications of the duct are
naturally  spread out  towards the ultimate acini.  The metal easily
penetrates to  these parts, and  appears  in the form  of clusters of
minute globules, having an  average diameter  of -g^ of an inch.
These indicate, with  probable truth, the terminal vesicles in which
the  duct  ends, and which are lined with  the epithelium, or  true
secreting  tissue, continuous with that of the duct.
  The vesicular terminations lie  in the meshes of the capillary  net-
work, as is the case with the follicles of the salivary, and other  con-
glomerate glands.
  The secreting cells are  more or less spheroidal in form, and vary
somewhat in character according to their age.   The mature cells are
about the y^u  of an inch in diameter, and are opaque, in conse-
quence of being filled with numerous minute oil globules.  The young
cells are smaller than these, and  are not so opaque.
  The epithelium in the large  ducts is of  the  columnar variety.
The wall  of the duct appears to be composed of fibrous  tissue, in
which elongated nuclei make  their appearance upon the addition of
acetic acid.  The  secretion of the pancreas has been described in
Chapter XXV., p. 593.
  Liver.—The liver is a large solid glandular organ, of firm consist-
ence,  of  a dark reddish-brown  colour.   It measures  about twelve
inches from side to side, and six or seven inches from its anterior to
its posterior border.  According  to the observations of Krause, the
bulk of the liver corresponds  to about eighty-eight cubic inches; its
weight is between three and four pounds, and  in the adult usually 
768
LIVER.
amounts to about l-36th of the weight of the whole body ; but in the
fcetus it is  comparatively much larger.   The  female liver  weighs
somewhat less  than that  of  the male.   The specific gravity of the
liver is  about 1'05 in health.
  The following is  an analysis by Prof. Beale of a liver, presumed
to be healthy.  The organ was taken from the body of a man thirty-
one years  of age, who was  killed  by falling  from  a second-floor
window, while in the enjoyment of perfect health.
                                                     Per 100 of
                                                     Solid Matter.
     Water.........68 68
     Solid matter .    .   .   .   .v    .    .   .   31-42

         Fatty matter.......3-82
         Albumen     .......     4-67
         Extractive matter......5 40
         Alkaline salts     ......     1-17
         Vessels, etc., insoluble in water    .    .   .    16 03
         Earthy salts.......      -33

                                                100-00

  In  disease, the proportion of these constituents is liable to very
great variation.  In fatty degeneration, an enormous amount of fatty
matter  may accumulate in the organ.   In one remarkable case, ana-
lyzed by Dr. Beale,  the  liver contained  75.07 per cent, of  solid
matter, and of this 65.19 consisted of fatty matter.*   In scrofulous
degeneration of the liver the albuminous materials and the water are
increased, while the fatty matter is  diminished in quantity.
  The liver is situated in the right hypochondrium, and reaches over
to the left, being thick and indented behind where it crosses the pro-
jecting  bodies of  the vertebrae, convex on  its upper  surface where  it
lies in the hollow of the diaphragm, and concave below where it rests
against the stomach, colon,  and right kidney.   It is covered to a
great extent by the peritoneum, the reflexions of which on to neigh-
bouring parts, serve as ligaments to bind it in  place, as well  as  to
allow of the entrance and exit of the nerves and vessels, some of the
latter  being sufficiently large and strong to  aid materially in the
mechanical support of the organ.
  The liver is an unsymmetrical organ.  In the foetus, it is situated
more  equally on each side of the median line of the trunk; but in the
adult the right side enormously preponderates, by the wasting or want
of development of the left.  It is still, however, divisible into a right
and  left lobe  by the broad peritoneal ligament above,  and by the
longitudinal fissure beneath,  both of these commencing in front by a
notch in the border, across which passes, between the  layers  of the
broad ligament, the cord-like remnant of the umbilical vein, and both
tending towards the notch in the posterior border which  lodges the
vena cava; these divisions, however, are both of them on  the surface
only, and are rather vestiges  of the imperfect  conditions of foetal ex-
istence than  of  value in the study of the physiological anatomy of
the gland.

          *  Diseases of the Liver.  Dr. Budd. Second edition, 1852.
12-16
14-86
17-18
 3-72
5101
 1-05 
LOBULES OF THE LIVER.
769
  On the under surface of the liver, is observed a groove passing off
from the longitudinal fissure, transversely, for a certain distance, on
the surface of the right lobe, and lodging the biliary ducts, the sinus
of the vena  porta, the  hepatic  artery, with lymphatics and nerves,
all enveloped in  areolar  tissue,  called the  capsule of Glisson,  and
brought to  this  transverse fissure between the layers of the gastro-
hepatic omentum.  From this groove, there extends  throughout the
substance of the  organ  a series of tubular passages, so numerously
ramified and uniformly distributed, that no part whatever of the he-
patic substance  is at a greater distance from them than about the
thirtieth of an inch.   These are called the portal  canals  (fig. 216),
so named by Mr.  Kiernan, because they lodge the branches of the
portal  vein, from which  the plexus of  capillaries surrounding the
biliary-cells  takes origin.   The portal  canals also lodge the bile-
ducts, which are thus conducted to that aspect of  the  mass of bile-
cells, where  the capillary plexus commences.  The same canals  also
convey the hepatic  artery  with the  lymphatics and nerves of the
liver.
   On the posterior border of the liver already referred to, is a deep
groove placed obliquely,  the fissure for the inferior vena cava;  from
this there penetrate the substance of  the
organ,  another series of ramified tubular
passages, which  are completely occupied
by a  nearly  corresponding  number  of
branches of the  hepatic veins,  or venae
cavce hepaticce, which open  into the vena
cava.   These canals, called by  the same
distinguished anatomist,  hepatic  venous
canals, are so  distributed throughout the
organ that some part of them comes within
Jg of an inch of every portion of its sub-
stance, and they are intermediate to  the
ramifications of  the portal vein.   The
bases of the lobules adhere to these veins,
and when they are cut across they do not
collapse.  The hepatic  veins occupying
these  canals, throughout the organ, re-
ceive the blood of the portal vein after it
has traversed the  plexus  of capillaries
which envelops the series of biliary-cells.
This plexus of capillaries we therefore term the portal-hepatic plexus.
It  is  a plexus containing  venous blood, from which  the bile-cells
derive the materials which they secrete.   The space which the blood
passes over in traversing  this  plexus, in contiguity to the cells, is
measured by the  distance between the  ramified portal surface and
the ramified hepatic venous surface of the liver.   The series of bile-
cells  discharge  the bile into the biliary ducts on the port.il side of
the plexus, i.e., where the blood is entering  it, and their most remote
parts  commence on the hepatic venous side of  it, i. e.,  where the
 A transverse section of a small por-
tal  canal and its vessels,  after Kier-
nan. 4. Portal vein.  2. Interlobular
branches.  5. Branches of the vein,
also giving off interlobular branches,
termed  by Mr.  Kiernan, vaginal
branches.  7. Hepatic  duct.  6.  He-
patic artery. 
770
LIVER.
blood is leaving it, so that the blood circulates  in the reverse  direc-
tion  to that  in which the bile must flow.
  Human .liver in which the portal vein (d) had been injected white, the artery (e) red and the
 hepatic vein (c) lake; from the surface  Magnified 15 diameters. The capillary plexus is only shown
 in a few places  a. Portion of portal hepatic plexus.  6. Portal hepatic plexus receiving a°^ terortS
 surface small  branches from the artery,  c. Branches of the hepatic vein interdiritatin^ wifh tlfi
 portal canals,  d. Branches of the portal vein.   «, One of the branches of' the artfry  sonTe of s
 DraBCeaTeare ^ l'amlfymg Up0n the coats of the Portal vein> and a &w join the capillary plexus ft!

   The Liver  in Invertebrata.—The liver is  one of the most  constant glandular organs
 being  met with, in some form, in all animals provided with a digestive cavity   In the
polyps, the liver is represented by some coloured cells  round the  stomach   In manv
 of the annelids, clusters of biliary cells are seen surrounding the csecal prolongations of
 the digestive cavity.  In the Eohs (one of the nudibranchiate gasteropodous mollusks
 a somewhat similar arrangement is observed,  the follicles of the alimentary tube beini
 prolonged into the papilla,, covering the dorsal surface of the animal.   In most oS
 moUusks,  however, the liver exists as a distinct organ, and is composed of branched
 fo hcles, arranged round terminal ducts.   The follicles contain coloured ceUs, in which
oil globules are  often present m constable number.  In many of the crustac7a  he
liyer » detached from the intest nal walls, and consists 0f  numerous  h\ZT?Z* (t
215) which pour their contents into small ducts, although in others it seems  UTconsifi
amply of cells arranged m follicles, which are connected with the intestine, as in the
lowest classes.  In msects, the hepatic organ takes  the form of simple or  branched
tubes,  from two to  six m number, which  open into  the intestine.  Accordingto oS
observations  the cells do not appear to be arranged round the  tube, so as to leave a
distinct central  channel,  as in the uriniferous tubule, but lie within the basemen?
membrane, without order or regularity often completely filling the tube, and nTun
frequently, from their large  size, caus.ng it  to  bulge.  We shall presently see that a 
LOBULES OF THE LIVER.
771
Fig. 218.
very similar arrangement exists in the tubular network of basement membrane, which
contains the liver-cells in vertebrate animals.
  Throughout the whole animal series, the liver consists essentially of cells containing
colouring matter, and usually oil globules, which lie within a tube or follicle of base-
ment membrane, continuous with the alimentary canal.

   Having  premised these general  points, we shall now proceed to
consider  the anatomy  of  the liver more in detail.
   Lobules of the Liver.—The terminal twigs of the portal veins and
the commencing radicles of the hepatic vein, thus  distributed through
the liver with a definite thickness of capillary plexus with nucleated
bile-cells interposed, are further  arranged in
such a manner as  that the intervening mass
is gathered,  not  into a folded sheet, but into
a great  number of  small portions,  termed
lobules.   These  lobules are apparent to the
eye in many animals ; but in the  pig they are
each  of  them invested by a separate  and
distinct  membranous  envelope  or   capsule,
which is  composed  of delicate fibrous tissue
(fig. 218).   In this animal,  each lobule  may
be regarded as an isolated and separate liver,
and the whole gland as an agglomeration of
smaller  ones,  connected  by the  penultimate
branches of  the  portal vein, artery  and  duct,  which run between the

                                Fig. 218.

 Portion of fibrous capsule of
a lobule of the pig's liver, show-
ing arrangement of the fibres—
215 diameters.
 Lobules of a cat's liver partially injected through the portal vein, and also through the hepatic
vpin  a Twigs of portal vein.  6. Capillaries springing from them, which serve to mark the outline
nf the lobules d. Capillaries in the centre of the lobules injected from the hepatic vein  e. Situa-
tions at which the injection forced into the two vessels has met.  I. Central parts of lobule not
nj ected. 
772
LIVER.
lobules, and by the areolar tissue which accompanies them; but not
by any inosculation or coalescence of the ultimate secreting elements,
the liver-cells, or the capillaries.  In other animals, and in the human
subject, the  lobules  are not thus isolated,  but are only imperfectly
marked out  by the several  points of their exterior,  to which the ul-
timate twigs  of the portal vein and duct arrive.   The twigs of the
vein terminate in  a plexus of capillaries common  to all  the conti-
guous lobules, and continuous between them, so that the lobules them-
selves have  no definite limit (fig. 219), but blend with  each other,
except at certain points of their exterior.   It is not likely that these
differences in the isolation  of the lobules in various animals are of
any physiological importance, but they  have,  probably, given rise to
much of the difference of opinion which exists among anatomists on
this subject.
  The shape of the lobules, whether completely defined by an invest-
ment  of  fibrous tissue, or merely  mapped  out by  the position of
the several twigs of the  portal vein,  hepatic artery, and duct, may
be said to be determined by the mode of distribution  of these vessels.
The intralobular hepatic vein occupies the central axis of the lobules,
and usually consists of a stem, into which three to five, or even more,
subordinate twigs empty the blood derived from the capillary plexus.
The lobule is elongated on this vein, and presents a process for each
of the subordinate twigs.
                                    In all cases, the terminal branches
                                 of the  portal  vein  and  the  duct
                                 arrive at the surface of the lobule
                                 at several points ;  and the surface
                                 of the lobule, whether  complete or
                                 incomplete, is continuous with that
                                 of the  portal  canals.  From this
                                 surface, in  all  cases, the capillary
                                 plexus tends, by the slight elonga-
                                 tion of its  close meshes, and con-
                                 verges  towards  the intralobular
                                 hepatic
                                 lobule.
                                 in this
         vein in  the  axis  of the
         It  probably follows  that,
        latter situation, the blood,
after having been nearly deprived
of  those constituents from  which
the bile is formed, circulates  more
rapidly than at the more external
parts of the  lobule, whither it has
just been  brought  by the portal
veins,  richly charged with  these
constituents.
  Portal  Canals.—It
already  observed  that
canals  contain  a branch  of the
portal vein, with a branch  of the
hepatic artery  and of the  biliary
Fig. 220.
A.9
 Longitudinal section of a small portal vein
and canal, after Kiernan. a. Portions of the
canal from which the vein has been removed.
6. Side of the portal vein in contact with the
canal, c. The side of the vein which is sepa-
rated from the canal by the hepatic artery and
*">•* with areolar tissue (Glisson's capsule).
duct,
d. Internal surface of the portal vein, through
which is seen the outline of the lobules and the
openings of the interlobular veins.  /. Vaginal
veins of Kiernan.  g. Hepatic artery,  h. He-
patic duct.
has  been
the portal 
PORTAL VEIN.
773
duct; not unfrequently the vein is  accompanied by two branches of
the artery and duct.
   The branches  of the artery and  duct are  connected with those of
the portal vein by areolar tissue, which is  abundant in the transverse
fissure of the liver, and in the larger portal canals, but in the smaller
exists chiefly on that side of the vein where the artery and duct lie;
while,  as the vessels diminish in size, the  amount of this areolar tis-
sue becomes less until it  entirely ceases, where the small branches
which  supply the lobules  are given off.   This investment of areolar
tissue, described under the name of Glisson's  capsule, from its dis-

                              Fig. 221.
 A small lobule from the pig's liver, showing a, the interlobular branches of the portal vein, and 6,
a portion of the lobular capillary network within the capsule injected. Each branch is seen to give
off small branches on either side to the adjacent lobules.  After Dr. Beale.

coverer, has been stated, by many subsequent writers, to be prolonged
into every part of the gland, separating the lobules from each other,
and forming an investment for each—a description which we have
failed to verify in every mammalian animal  which we have examined
except the pig, where this areolar tissue is really prolonged between
the lobules.
  Portal Vein.—The large portal vein is formed by the union of the
veins of the stomach and intestines, the pancreatic and splenic veins,
and the veins of the mesentery, omentum, and gall-bladder.   The
portal circulation has been described in p.  676, and we have, there-
fore, only to describe the distribution of the vein in  the liver.   The
branches of the  portal vein may be said,  in general  terms, to be
arranged round  the lobules;  but  the branches  upon different sides
do  not anastomose so as to  encircle each lobule with a venous ring,
as  many authors, following Kiernan's  diagram, have described and
represented, but communicate with each other only through the inter-
vention  of  capillaries.  Even  in the pig there is no vascular ring,
       50 
774
LIVER.
although to the naked eye it might appear so.  In the liver of the
human subject, and in livers allied to it, small branches of the portal
vein can often be traced from the interlobular fissures into the lobule,
breaking  up into capillaries  as  they go.   The arrangement of the
branches of the portal vein round one of  the smallest lobules of the
pig's liver, with a few of the  lobular capillaries injected, is shown in
fig. 221.
  Hepatic Artery.—Many branches  of the artery pass to  the cap-
sule of the liver, in which they ramify abundantly,  forming a net-
work,  having large meshes.   These capsular branches  and  their
anastomoses, are readily injected in the liver of the fcetus or child.
  The artery gives off numerous branches in  the portal canals.  The
greater number  of these are distributed upon  the coats of the ducts.
The thick walls  of the  larger  ducts are  abundantly supplied with
arterial blood;  but the smaller branches of  the  duct, the  coats of
which are extremely delicate, pass through the meshes of an arterial
network.   In the pig, this network may  be demonstrated upon the
surface of  each lobule  (fig.  222), but in the human  subject, the
branches  are  less numerous, and  are seen only in the interlobular
fissures; other branches  supply the coats of  the  portal and hepatic
veins.   The greater quantity of blood, after  passing through  these
small arteries, is collected by venous radicles, which  empty them-
selves into the branches of the  portal vein.  A few very small arte-
rial branches may be traced from the portal  aspect of the lobule for
a short distance  into its  interior, where they join the portal hepatic

                             Fig. 222.
 a. Part of arterial ring, with branches ramifying upon the capsules of the lobules of the pig's liver.
6. Arterial network,  c. Portion of lobular capillary network injected from the artery, and small
branches of the latter entering it. After Dr. Beale.
plexus of capillaries.   The  whole of  the arterial blood, therefore,
which supplies nutriment to  the several structures of the liver, passes
through the capillaries of the lobule before it is returned to the heart,
and  no doubt furnishes  a small portion of the  matters from which 
DUCT.
775
the bile is formed.  The artery was rightly regarded by Kiernan as
one of the sources of the blood conveyed to the secreting structure
of the liver, by the branches of the portal vein.

                              Fig. 223.
  A small lobule, showing the duct branching upon the capsule, from the pig. The sacculi of the
 ducts are injected in this specimen. The vessel accompanying the duct is a branch of the portal
 vein.

   The gall-bladder is also supplied largely with arterial blood.   The
 arteries are arranged  so  as to  form a  beautiful network.   Each
 branch of the artery is  accompanied  by two  branches of the vein,
 one on either  side,  and when the arterial and venous networks are
 injected with  different colours a most  beautiful appearance is pro-
 duced.  A similar  disposition  of arteries and veins occurs in "the
 transverse fissure, and also in the large  portal canals.   This arrange-
 ment  has  probably the effect of insuring free circulation through
 the veins in those changes of size and  position to which  the vessels
 are liable.
   Duct.—At least one branch of the duct accompanies each branch
 of the portal vein, but frequently there are two or three.   From the
 branch or branches accompanying  the vein,  several  smaller  ones
 pass off to the secreting structure.   In  the  pig,  the interlobular
 ducts,  while running between contiguous  lobules, are applied,  as it
 were, to the exterior of their capsules, and  give off much smaller
 twigs on either side, which perforate the capsules,  and become con-
nected with the cells in the manner presently to be described.
  Parietal Sacculi  and  Appendages  of the  Ducts.—In ducts of
about  the T^?  of an inch in diameter, and  larger, there are many
little saccular  dilatations situated in the coats.  These  are  the so-
called  glands of  the ducts, and  in the pig, and most other animals
which  we have examined, are  arranged  all round  the  tube.   Dr. 
776
LIVER.
Beale, who  has examined them with great  care, describes them as,
for the most part, simple oval pouches connected with the cavity of
the duct by a very narrow neck, often not the  g^^ of an inch in
diameter.   In the larger ducts, they are branched, and often run for
some  distance in  the  coats.  Occasionally,  the branches  of  one
gland anastomose with those of another.   The largest are singularly
complicated, and project some distance  from the duct lying in the
areolar tissue which surrounds it.  Fig. 224.
   In  the human subject, a different arrangement occurs.  Instead of
being situated entirely round  the tube, the  openings form two rows
or lines  situated upon  opposite sides of  the  ducts.  The  greater
number of these openings are, however, the orifices, not of  sacculi,
but of small irregular tubes, which  run obliquely for  some distance

                              Fig. 224.
 a. Portion of a large duct of the pig, injected with vermilion, showing the large cavities or glands
in the coats of the ducts.  The largest and most complicated are represented at c, just at the point
where a smaller branch is coming off from the trunk of the duct. 6. A small branch without glands.
Magnified about ten diameters. From a drawing by Dr. Beale.

in the coats of the duct  and  anastomose; some of these  branches
leave the ducts anastomose with  each other just  outside the  trunk
from which they  are given off.
   Many of the small ducts about the ^ of an  inch in diameter, have
numerous csecal pouches connected with them, arranged pretty close
together, gradually becoming shorter as the duct becomes smaller,
and  giving off branches  composed  of  basement membrane only.
These irregular ducts with caecal pouches  are very  numerous  in the
transverse fissure  of the liver, where they form  an intricate network
connected with the larger  branches of  the duct in this  situation.
These were described by Theile as branching mucous  glands, but were
first  noticed and named vasa aberrantia by Weber, who also de-
scribed the anastomosis  between the right and  left hepatic ducts
in  the transverse  fissure, by the intervention of  these  irregular
branches.
   In the portal canals,  the vasa  aberrantia  occur as  already men-
tioned, but in diminished number.  Dr. Beale considers these cavi- 
GALL-BLADDER.
777
ties, or irregular branches, connected with the ducts, as little reser-
voirs in which the bile  in  ducts with thick  coats is  brought into
closer  proximity with  the  numerous vessels  surrounding them, by
which  means  it  loses some of its water, and  probably undergoes
other changes.   He observes, that  the  arrangement  of the vessels
around these ducts, both in the transverse fissure of  the liver  and
in the portal canals, is  similar to that which exists in  the coats of
the gall-bladder.  A small cavity with a  narrow neck seems scarcely
adapted for pouring out viscid mucus; moreover, the bile of animals,
in which these  so-called glands are very few in  number, as in the
rabbit, seems to contain as much mucus as that of the pig, in which
animal the glands are very numerous and well developed.  Accord-
ing to this view of their office, these cavities  may be regarded in  the
light of little gall-bladders.
   The coats of the larger ducts appear to be  principally composed of
condensed  fibrous tissue, but there is reason for supposing that, at
least in some of them, there are a few muscular fibre cells, although
they do not form a distinct layer or  muscular coat.
   The epithelium of the  larger ducts is of the  columnar variety.
The cells are large and well formed, often exhibiting a  distinct  nu-
cleus.   They  are frequently  tinged  with yellow  colouring  matter,
and often contain yellow granules.  In  the  smaller ducts, this  epi-
thelium becomes shorter, until, in the smallest branches, it approaches
more nearly to the tesselated  variety.
   Gail-Bladder.—The gall-bladder may be looked upon as a diver-
ticulum of the hepatic duct.   It lies in a fossa underneath the liver.
It is of a pear shape, and its  fundus is directed downwards and for-
wards ;  it terminates in the cystic  duct, which is about an inch in
length.   The hepatic duct, leaving the liver by the transverse fissure,
passes downwards, and soon joins the cystic  duct at an acute angle,
to form the ductus communis choledochus, which is about three inches
in length, and lies between the layers of the gastro-hepatic omentum.
After coming into close proximity with the pancreatic duct, the com-
mon duct enters the coats of the intestine with the latter, and passes
obliquely between them for three-quarters of an  inch.   The ducts
open by an orifice  common to both at the junction of the descend-
ing  and transverse portions of the duodenum.   The mucous mem-
brane of the gall-bladder is thrown into reticulated folds, which form
the boundaries of numerous polygonal depressions, so that upon its
internal surface it presents a honeycombed appearance.  It is highly
vascular, and  is covered with columnar  epithelium.   The folds  are
prolonged  into the  cystic duct, where they  are arranged in a cres-
centic  manner, their general direction being that of a spiral, and they
have been  compared to a spiral valve.  The peculiar arrangement of
the vessels of the gall-bladder has been  already referred to.   The
cystic artery is derived from  the right division of the hepatic, and
the veins empty themselves into the vena portae.   The  lymphatics
are very numerous.   The greater part of the thickness of the walls
of the gall-bladder is composed of fibrous tissue, but there also exists
a  thin  layer of  delicate muscular fibre  cells, which take partly a 
778
LIVER.
longitudinal and  partly a  transverse  direction.   The human gall-
bladder is capable of containing about an ounce of fluid, but it  un-
dergoes great  alterations in volume, and in it  the bile becomes in-
spissated, and probably undergoes other  changes.

  This viscus is  absent  in many genera of fishes ; in pigeons, toucans, and  some
other birds ; in the elephant, 6tag, horse, and tapir; but it is present in the ox, sheep,
and antelope.  It is always found amongst reptiles.  The reason of its  absence in
the animals above alluded to is not yet satisfactorily explained.

   Hepatic  Vein.—The branches of the hepatic vein run in channels,
which are  situated between the portal canals (fig.  217), and in con-
sequence of the  small quantity of areolar  tissue surrounding  the
hepatic vein, the  bases of the  adjacent lobules are in contact with
it, so that when a branch of the hepatic vein is cut across, it does
not collapse, but  remains open.  The  small  twigs  which  collect  the
blood from  the lobules surrounding the  trunk of  the vein open at
once into it, except  in  the  case of  the largest  branches,  where  the
coats are very thick.  This arrangement is  shown in fig. 225, after
                                    Mr.  Kiernan.   In  this draw-
Fig. 225.
Por-
ing  the openings  of the small
branches of  the  hepatic vein
(intralobular  vein)  are seen  in
the centre of each lobule, while
in fig.  220, which represents a
portal vein laid open, the orifices
of  the  smallest branches  are
seen in the spaces  between two
lobules  (interlobular veins).
   The capillaries in the central
part of the lobule open into the
small twig of the  hepatic vein
upon all sides.   These  points
are well seen  in the pig's liver,
where the lobules  are distinct,
but  in  the  human and other
livers,  the  arrangement  varies
slightly in  consequence of the
lobules communicatingwith each
other  in the intervals between
the  interlobular fissures  (fig.
217).
   Nerves  and  Lymphatics.—
The nerves   of  the   liver are
 Longitudinal section of an hepatic vein.
tion of the  canal from which the vein  has been
removed. 6. Orifices of ultimate twigs of the vein
(intralobular) situated in the centre of the lobules,
after Kiernan. Compare the arrangement of the  derived chiefly from the SVmpa-
small veins in this figure with the branches of the  .i.-i      Vc    -i     i     «
portal veinin fig. 220.                      tnetic, but  a lew  branches  01
                                    the vagus are also distributed to
the organ.  They consist of  tubular and gelatinous nerve fibres, and
are distributed  principally upon the walls of the artery over which
they  form a network.
  Branches may be traced into Glisson's capsule, and to the coats of 
LIVER CELLS.
779
the gall-bladder and larger ducts, as well as to the coats of the larger
branches of the hepatic vein.
   The lymphatics  are found in considerable abundance in the liver;
they are distributed  to the gall-bladder, and form a network upon
the surface of the organ underneath the peritoneum.   An abundant
network of lymphatics  exists in the largest portal canals, and when
the ducts  are injected, it  not unfrequently happens that  a  small
branch bursts, and the injection escapes into the lymphatics.  In this
way, some lymphatic glands  near the liver are often injected, and
the injection sometimes even reaches the thoracic  duct, as occurred
to Mr. Kiernan, and also to Dr. Beale.
   Of  the Liver Cells.—From what  has been already stated, with
regard to the arrangement  of the solid capillary venous plexus of the
lobules, it will be inferred that the cells occupy the meshes  of this
network.   It has long been a  question whether the cells lie amongst
these capillary vessels, or  are  enclosed in a basement membrane, as
we should expect from the analogy of other glandular organs. It has

                               Fig. 226.
 Section of horse's liver, at right angles to branches of the hepatic vein, showing the cells forming
lines radiating from the centre towards the circumference of the lobules. From a preparation of Dr.
Beale's.

been admitted by all who have examined the liver carefully, that in
sections made in  a particular direction, the cells are seen to form
lines which radiate from the centre towards the circumference of  the
lobule;   these  lines  being connected with  oblique or  transverse
branches.  Such an appearance is not presented in every section,  but
only in  those made exactly at right angles with the small twig of  the
hepatic  vein.   This  is well seen in fig. 226.   The cells are described
by Kolliker and  others, as being placed  end  to  end, forming solid
cylinders, but not invested with basement membrane.  Usually there
is only  room for  one row of cells; but in some situations, two or three 
780
LIVER.
may be seen  between two capillary vessels.   Dr. Handfield Jones
has been led by his researches to adopt the same conclusion with re-
gard to the arrangement of  the liver  cells, and  Dr. Carpenter has
expressed himself in favour of a similar view.
   On the other hand, Retzius, Leidy,  and some other observers, ad-
vocate the presence of a tubular basement membrane, in which the
cells lie, and which is continuous with  the hepatic ducts.
   The minute anatomy of the  liver has lately been subjected to a
careful  investigation by our friend and former pupil, Dr. Beale; and
we believe  he has established  the existence of this basement mem-
brane by several different methods of preparation.  His observations
have  been  made  upon  injected  as'well as uninjected  preparations.
The membrane is so  exceedingly delicate, that  it can  be  demon-
strated  alone  by the granular matter which adheres to it.  Dr. Beale
has succeeded in injecting  the tubular network in which the cells
lie;  and the injection has been seen to pass  round the  cells, sepa-
rating them slightly from each other.  When the cells are broken
down by the action of chemical reagents, the outline of the tube can
often be seen  distinctly.   This  delicate basement membrane in most
situations appears to be incorporated with the walls of the  capillaries,
but in some places it is to be demonstrated distinct from them.
   Not unfrequently cells are met with in  the fluid surrounding a
section  of liver with shreds of membrane attached to them ;  and in a
few rare instances this membrane may  be seen  in the form of a tube,
in which the cell is evidently contained.  Injection, however, affords
the most  satisfactory proof of the existence of this basement mem-
brane.  In  well-injected specimens  the outline of  the tube in which

                            Fig. 227.
 Portion of tubular network of basement membrane in which the liver cells lie, a. from an iniected
specimen—the shaded portions show the position of the injection, b. Cells and free oil globules lying
within the tube.  c. Specimen in which the cells have been disintegrated. From the  pig • 21u dia-
meters. After Dr. Beale.                                          r ° 
OF THE SMALLEST DUCTS.
781
the cells are contained can be seen in some parts of the lobule, sepa-
rated from that of the capillary vessels.*
   The liver cells may be broken down in some specimens, and the
tubular membrane contain  only granular matter suspended in fluid,
as represented in  fig. 227 c.
   The  peculiar and characteristic cells of which the substance of
the liver is chiefly composed, are of a more or less spheroidal form,
but  often  somewhat  flattened  and many-sided  from  mutual com-
pression.
   They vary from the y^^ to the ^^ of an inch in diameter, and
sometimes even smaller.  Their surface is smooth, and their outline
distinct and well defined.  Each contains  a distinct nucleus  in the
interior, and occasionally cells may be observed with two nuclei.  In
the nucleus a highly refracting nucleolus, with several granules, can
usually be distinguished.
   The contents of the cell appear  to be of a firm viscid consistence,
so that when pressed between glass, the contents do not escape sud-
denly, but the whole cell becomes flattened.   Usually there are, in
the interior,  several oil globules, which,  as regards size  and number,
are subject to great  variations.   In  some cells the  entire  cavity is
occupied by globules,  in others not one can be observed; besides  oil
globules, distinguished by their  light centre  and dark well-defined
outline, the cell contains in its interior numerous amorphous granules,
which may vary in size from a scarcely visible  dot, to  a particle as
large as a blood globule, or even larger. Granules of a bright yellow
colour, composed of biliary  colouring matter, are often  met with, but
do not occur constantly.  In  cases  of jaundice from obstruction of
the duct, the number and  size of these coloured particles often in-
crease to an enormous extent, so that the cell appears to be entirely
occupied with  them, and in extreme cases no distinct cells whatever
can be detected.
   In highly fed animals, and  in that condition termed  fatty degene-
ration of the  liver, so common  in cases of phthisis, the cells seem
almost entirely occupied by large oil globules, without any coloured
particles.  The cells  at the portal aspect  of the lobule usually con-
tain most oil, while  those in the centre contain a greater number of
coloured granules, but frequently  these yellow granules are present
in the cells in  both situations.
   In dilute  caustic  soda, or  potash, the  cells swell up and become
pale, and of a more rounded form;  after a short  time  they are  dis-
solved, unless  the solution  is very weak.  Acetic acid produces a
somewhat similar  change, but the cell membrane  does not  appear to
be dissolved.  The nuclei always appear more distinctly  defined after
the addition  of the acid; cells which, at first,  were found to contain
no coloured granules,  by being soaked for  some time in dilute acetic
acid exhibited  many.
   Of the smallest Branches of  the Hepatic Duct and  of  their Con-
nection with the Hepatic  Cells.—Of the manner in which  the ducts

  * These specimens were prepared by injecting the ducts with Prussian blue, and
the portal vessels with plain size. 
782
LIVER.
Fig. 228.
 Terminal portion of interlobular duct, with
epithelium within it. Four hepatic cells to
show relative size.  To illustrate Dr. Handfield
Jones' view.
commence in the liver, there has been much difference  of  opinion,
                                and the  most conflicting views have
                                been  entertained.   Mr.   Kiernan
                                considered  that  the  ducts  com-
                                menced in a lobular plexus although
                                he was never able to prove the ex-
                                istence  of  such  an  arrangement.
                                Kolliker gives  a diagram  to  illus-
                                trate his view,  which supposes that
                                the open ends  of the ducts impinge
                                against  the columns of the hepatic
                                cells at  the margin of the lobule.
                                Dr.  Handfield  Jones  traces  the
                                ducts to the same  point, where, he
                                believes, they  terminate  without
                                having  any direct communication
with the hepatic cells; and he considers that the small cells in these
ducts are alone concerned in the secretion of the bile (fig. 228).  If
this  view of the  anatomy of the liver be correct,  this large organ
must be nearly related to the vascular glands.*
  Dr. Beale's researches show  that Mr. Kiernan's original view is
more nearly allied to the truth.
  In the interlobular fissures numerous finer branches leave the small
trunk of the duct and pass towards the secreting cells.   In the human
subject,  many of these may be followed  for some  distance without
giving off branches  or anastomosing with each other.  These small
ducts lie around the small  branches of  the  portal vein, and  their
course is often  tortuous.
  In some animals, particularly in the rabbit, the small ducts anasto-
mose, forming a network round the vein.  This network is continuous
with the network of the lobule in which the cells lie.   In the human
subject, and in most  mammalia, the small ducts do not form a network
in this manner, but pass off at once to the  cell-containing network
with which they are continuous.   In the pig, the smallest  branches
of the duct penetrate the capsule of the lobule at various points, and
immediately become  connected  with an intimate network which lies
immediately beneath it,  and partly within its substance.  This net-
work may be regarded as the most superficial portion of the cell-con-
taining  network, and where  the liver is  fatty it contains  cells dis-
tended with oil globules.
  In the human liver, and in those  of most animals, except the pig,
some of the smallest branches of the duct pass  for  a short distance
beneath the surface  of the lobule, and  become continuous with some
of the branches of the cell-containing network in that situation.  In
a cursory examination these  narrow ducts appear to lie amongst  the
cells without being  connected with them.  The  greater number of

  *  Vide Kolliker's Manual of Human Histology,  translated by Busk and Huxley;
Sydenham Society, 1853-54.  Dr.  Carpenter's General and Comparative Physiology,
4th edition. 
OF THE SMALLEST DUCTS.
783
branches, however, join the cell-containing network round the margin
of the fissures.
  Near to the point where the duct joins the cell-containing network
it becomes very much  narrowed, and is often not  more than the
Woo or so'oo- of an inch in diameter, and even less, in the uninjected
state.   Several of the narrowest ducts in the  pig are represented in
fig. 229.
                              Fig. 229.
 a. Small branch of interlobular duct-pig.  b. Most superficial part of cell^Wnln«J}^0'^
with cells filled with oil, and free oil globules, c Narrowest portions of the duct  Magnified 215
diameters. The shaded parts show the points to which the injection reached. After Dr. Beale.

   Fig. 230 represents some of the small ducts and a part of the cell-
containing network at the  surface  of a  lobule  in the human liver.
The cells have been nearly destroyed  by the action of reagents in
preparing the  specimen.
   The epithelial cells which line these minute ducts approach to the
tesselated variety.  They are,  for the  most  part, round  or oval
granular cells,  some  of them  about the
■gjjsjith. of an inch in diameter, while others
are less.  They present  very similar cha-
racters  in the different  animals  which  we
have  examined,  and  the  same  general
arrangement of the minute ducts has  been
shown to occur in birds, reptiles, and fishes,
with certain unimportant modifications.
    The epithelium  of the ducts does not pass
by gradations into the secreting epithelium,
but terminates at the point where the latter
 commences.   The narrowing of  the  excre-
Fig. 230.
Narrowest portions of the duct,
Comments.   xuc  ™C •    *  'tl '  Z  ^  ^ by ductal epithelium, show!
tory portion ot the tube is met witn in many  ing theil. connection with the ceil-
other glands,  but in none  is there a  more  ™£?ftg™iJil-Ju£
striking contrast between the excretory and  ^ T^lteT"n feMoTrZ
secreting portions^ the gland, or between  i^^^y^
the epithelium lining the ducts and that by  an  uninjected specimen of the
which the secretion is formed, than in the  ^"gS^**
liver. 
784
LIVER.
   Of the Passage of the Bile into the Ducts.—If the view of the
anatomy of the liver which we have described be correct, the secret-
ing cells at the  surface of the lobule  are those which take the most
active  part in the  secretion.   These  are the cells which the portal
blood first reaches; and it is in this situation that the cells first show
an increased quantity of oil  globules within them  in cases of  fatty
degeneration.   The  bile is not formed in  the central  part  of the
lobule, and transmitted  from cell to cell, as has been described  by
some authorities, but the bile formed by each individual cell escapes
through the interstices  between the cells until it  reaches the  duct.
If it be urged, as an objection to this view, that no visible interstices
exist between the cells, it may be answered that injection can be made
to flow by these channels in a direction the reverse  of that which the
bile naturally takes, and, therefore, under the greatest disadvantage.
There  can  then be no obstacle to the passage of the bile towards the
ducts; moreover, the great changes in  bulk, which we know the liver
cells so readily undergo, will readily account for the close contact in
which  they are often observed to lie.
   From  a  careful consideration of the anatomy  of  the parts,  we
should be led to look upon the liver as a large gland, in which a con-
siderable quantity of a highly elaborated secretion was slowly formed,
and  slowly transmitted in a more highly concentrated form towards
the intestine.   The  arrangement of the vasa aberrantia and of the
little  cavities  in  the coats of the thick-walled ducts, the abundance
of vessels  and lymphatics in such close proximity  to the ducts, and
the great  similarity of their disposition with that  of the vessels of
the gall-bladder, where  we  know  absorption  of fluid  takes  place,
favour the  idea  that important  changes occur in  the  bile after its
formation by the cells of the liver.
   The liver is, therefore, a true gland, consisting of a formative por-
tion  and a system of excretory ducts directly  continuous with it.
The secreting cells lie within a delicate tubular network of basement
membrane, through the thin walls of which they draw from the blood
the materials of  their secretion.
   Quantity and  Uses of the Bile.—We have already considered the
composition and  uses of the bile in Chapter XXV.; but since that
part of our work was published, some important results  have been
communicated by Bidder and Schmidt, which we shall here briefly
allude  to.*
   These  excellent observers  have concluded, from  numerous experi-
ments  upon different animals, that the quantity of bile  secreted dur-
ing the twenty-four hours is much larger than  had been supposed.
Cats secreted 14.5 grammes, dogs nearly 20 grammes,  and sheep 25
grammes, for each kilogramme (about 2 lbs.  3 oz. avoirdupois) in the
weight of  the animal.   From these data, it is of course,  difficult to
draw a correct inference as  to  the quantity of  bile secreted by the
human subject;  but, from calculating from  these results, it has been
  I
  * Die Verdauungssaefte und der Stoffwechsel von Dr. F. Bidder und Dr. C. Schmidt.
Mitau und Leipzig, 1852. 
SECRETING GLANDS.
785
rendered  probable that an adult man secretes  about 54 oz. of pure
bile in the twenty-four hours,  and this contains about 2| oz. of solid
matter.  This estimate is very much higher than that which we have
given at p. 597.
   The activity of the secretion  varies greatly at different periods of
the day.   For one  or two  hours after a meal, it  is very small in
amount; but from this time, it gradually increases until it attains its
maximum, about the fifteenth hour after the last  meal.  The secre-
tion then rapidly diminishes in  quantity, until it is not more than it
was two hours after the meal.   The gall-bladder empties itself about
two and a half or three hours after taking food.
   It  appears that an exclusively amylaceous, or fatty diet, causes a
great  diminution in the  secretion of  bile, while  a pure  flesh diet
induces a very abundant secretion.
   The presence  of bile very much promotes the absorption of fatty
matter, although a certain quantity of fat is absorbed even if no bile
enters the intestine.   The presence of bile causes the absorption of
two and a half times more fatty matter than would be absorbed with-
out it.  Bile appears to render the mucous membrane more perme-
able to fatty matter.
   Bidder  and Schmidt consider  that the  chief object of the bile is
" to prolong the series of  changes to which animal matter is sub-
mitted within the organism, and  thus to render it for a longer  time
efficient in the discharge of  vital processes."

  On the Pancreas, consult article "Pancreas" in the Cyclopaedia of Anatomy and
Physiology, by Dr. Hyde Salter.  Upon the anatomy of the Liver, the following works
may be referred to:  Kiernan, " The Anatomy and Physiology of the Liver," Phil.
Trans., 1833; Theile, Art. "Leber,"  im Wagner's Handworterbuch der Physiologie;
Article " Liver," by Mr. Wilson,  in the Cyclopaedia of Anatomy and Physiology;
Leidy, in the American Jonrnal of the Medical Sciences; Kolliker's Mikroskopische
Anatomie ;  Beale, " On the Ultimate  Arrangement of the Biliary Ducts, and on some
other Points in the Anatomy of the Liver of Vertebrate Animals," Phil. Trans. 1856.
                      CHAPTER XXXIV.

SECRETING GLANDS.—THE KIDNEYS.—PARENCHYMA.—MATRIX.—URI-
  NIFEROUS  TUBES.—MALPIGHIAN BODIES.—CONVOLUTED  PORTION
  OF THE URINIFEROUS TUBE.—STRAIGHT PORTION.—VESSELS OF THE
  KIDNEY.—OF THE  SECRETION OF URINE.--URINE.—QUANTITY.—
  REACTION.--CHEMICAL COMPOSITION.—UREA.—URIC  ACID.—HIP-
  PURIC ACID.—CREATINE.—CREATININE.—EXTRACTIVE MATTERS.—
  AMMONIACAL SALTS.—FIXED SALTS.—CHLORIDES.—SULPHATES.—
  PHOSPHATES.

  Next in size and importance to the liver, are the kidneys.  These
glands are symmetrical organs, one being placed on each  side of the
spine in the lumbar  region.   In consequence of the position of the 
786
KIDNEY.
liver, the  right kidney is placed rather lower down  than  the left.
These organs are surrounded by a varying quantity of  fat, and are
placed  behind  the  peritoneum.   The  kidney is  of a dark reddish-
brown colour, of a firm consistence, and of  a close compact texture.
Its  general form is that  of an ordinary French bean, compressed
from before  backwards, its  convex border  being external, and  its
concave edge,  or hilum, where the vessels  enter,  looking towards
the  median line.   The weight  of the healthy kidney is from 4^ to
5 oz. in the male, and somewhat less  in  the female.   The kidneys
are  supplied with blood by the renal arteries, two large trunks which
come off at right  angles from  the  abdominal  aorta.   The blood is
returned by the  large renal or emulgent  veins which open into the
inferior cava.   These vessels, with  the nerves for the supply of the
organ, enter the kidney at its notch or hilum, whence also  proceeds
the  ureter.

  Of the Kidney in the lower Animals.—The first trace of an organ which can be re-
garded in the light of a kidney is met with among the Polypi, but the renal nature of
this  is at least doubtful.  In Porpita, one  of the Acalephce,  Kolliker has described
an organ which contains guanin, and which he therefore looks upon in the light of a
kidney.  In the Annelida the existence of a renal apparatus  is doubtful; but there
is some reason for believing that the so-called respiratory organs are to be regarded
in this light.  The existence  of these glands is not determined in the Crustacea; but
among the Arachnida tubes composed of basement-membrane, and containing epithe-
lium, exist.   Guanin also has been  detected in them, so that there  can be little doubt
of  their real nature.  Among Insects,  renal organs exist as  long narrow tubes, and
the presence of uric acid has been detected in  several species.  In the Mollusca, ex-
cept in the lowest class, kidneys are distinctly observed, and are either two in number,
or combined to form a single organ with an excretory duct.  The spongy organs of
the Cephalopoda have been proved to be true kidneys, and uric acid has been detected
in them with the murexide test by E, Harless.  Kidneys exist throughout the verte-
brate classes, and are composed of tubular glands, provided with one or more efferent
ducts, connected with which are often observed numerous appendages.   The urini-
ferous tubule consists essentially of a tortuous tube  of basement-membrane, lined
with  secreting epithelium, and dilated at its closed extremity,  so as to embrace a tuft
of highly tortuous capillary vessels.


  The specific  gravity of the healthy kidney is  about 1*050, but is
liable to vary  somewhat, according to the  quantity  of fluid  which
exists in the organ at the time of examination.
  The  following  is  an  analysis of  the cortical portion  of  a healthy
human  kidney  by Dr. Beale.   The organ was taken  from  the body
of a  healthy man,  thirty-one  years of age,  who was killed by  falling
from a second-floor window :—
                                                           100 parts of
                                                          Solid Matter.
r ........	76-450	
	23-550	
Fatty matter, containing much cholesterine .	•939	3-98
Extractive matter, soluble in water	5-840	24-79
Fixed alkaline salts .....	1-010	-1-28
Earthy salts.......	•396	1-68
Albumen, vessels, etc. .....	15-365	Go-24
  Even  in health, the proportion of water  and  solid matter varies
greatly,  which fully accounts  for  the varying statements of different
observers with respect to the weight  of the healthy kidney.  In dis- 
PARENCHYMA.
787
ease, the composition of the secreting structure of the kidney under-
goes great alteration.   The fat is very much increased in quantity
in kidneys in a state of fatty degeneration.   The relative proportion
of the solids generally may be much diminished in quantity, which is
remarkably  the  case in some specimens of enlarged kidney.  The
increase of size, in these  instances, being  accounted for  by an un-
usual quantity of water in the tissue of the organ ; but in many cases,
it is, no doubt, dependent upon deposition of new matter.  In a very
large kidney, weighing  half a pound, only  14-39 per cent, of solid
matter was present, so that  in  this instance the increased weight of
the organ was undoubtedly due to a larger  proportion of water than
occurs in health, rather than to the deposition of  any adventitious
tissue,  or  to an increase of the normal gland-textures.
   Surface of the Kidney.—The kidney is immediately invested with
a firm fibrous coat, called the capsule, which is composed of con-
densed areolar tissue, and is continuous with the tissue constituting
the matrix of  the  kidney, in the meshes of which the tubes ramify:
some small vessels also connect the capsule of the  kidney with  the
proper gland-structure.   At the hilum, the capsule is continuous with
the external or fibrous coat of the pelvis of the kidney and the fibrous
coat of the  ureter.  The vessels also receive an investment  from it
at this point.
   If the surface of the kidney be carefully examined, it is  seen to be
imperfectly  mapped out into a number of small polyhedral spaces or
lobules, in general appearance somewhat resembling the markings of
the lobules  of the liver.   These markings are in  part due to  the
arrangement of  small branches of the veins which are spoken of  by
anatomists as the stellate veins.   Commencing at the surface of  the
kidney, they penetrate the cortical part in a vertical  direction, at
nearly equal distances, and receive, in their course to the hilum, the
blood from the venous plexuses surrounding the secreting tubes.   In
the spaces just  described, may be seen the convolutions of some of
the uriniferous tubes.   No arteries reach the surface.
   Ferrien supposed  that  the tubes  formed little pyramids, each of
which  radiated from the medullary towards the cortical part of  the
kidney, the  base of each pyramid consisting of one of these spaces or
lobules.   It appears, however, that  although each pyramid contains
many  tortuous tubes,  with their  capillaries,  the convolutions of a
single  tube are by no means confined to one pyramidal space.
   Besides the apparent divisions into  lobules just  referred to,  the
surface of the kidney bears the vestiges of several fissures, marking
it out  into  lobes which may be seven or eight  or more in number;
these lobes  indicate the original  condition of the  kidney in intra-
uterine life  when they were separated  from each other, and formed
distinct renules.   In the embryos of mammalia generally, the same
arrangement is observed; and  it remains permanent in the cetacea.
In the kidney of  the otter, seal, ox, and some other animals, it is
also conspicuous.  In the ox, the division into lobes extends only to
the pyramids.
   Parenchyma.—The parenchyma of the kidney consists of two dis- 
788
KIDNEY.
tinct  portions;  the one  cortical, about half an inch in thickness,
forming the whole convex surface of the organ, of a dark red colour,
and to the unaided eye of a granular appearance, and exhibiting nu-
merous red spots (Malpighian bodies) abundantly scattered through
it.  The medullary portion is embraced in this ; it is pale and smooth,
arranged so as to form several  pyramids,  varying  in  number from
eight to fifteen;  their bases are  placed  towards the cortex, from
which may be traced a number of nearly straight lines, which con-
verge towards the summit of the pyramid to which they belong.  In
this part of the kidney there are no Malpighian tufts, and even to
the unaided eye, it appears to be composed of a number  of straight
converging lines or tubes.
  These pyramids or cones end by free  summits which  project on the
hilum  into  the  pelvis of the kidney, the  mucous membrane lining
this cavity being continuous at the summit of the cone (or mammilla)
with the tubes. The mucous membrane  of the pelvis, however, forms
a sort of fossa, or saucer-shaped cavity, around each mammilla, or ter-
mination of the pyramid.  These calyces receive the urine escaping
from the open orifices  of the tubes on the summit of the cones, and
convey it toward the pelvis ; they become  enormously increased in
dimensions if there be any obstruction to the passage of  the urine
from the ureter or bladder.
  Matrix.—With reference  to the presence of a fibro-cellular matrix
in the kidney, which serves  as a support for  the vessels and  tubes,
there has  been  much  difference of opinion.  It was  originally de-
scribed by Goodsir, and has since been noticed by several observers.
  The matrix appears  to us to be  composed  of a firm transparent
and granular substance, in which we have seen small granular cells;
but have not been able to ascertain their precise nature.  The fibrous
appearance seen in thin  sections we believe to be due rather to the
crumpled state of the  walls of the capillaries and uriniferous tubes,
than to the existence of ordinary fibrous tissue in the matrix itself.
  The intervals between the  contiguous tubes and capillaries are
greater in the pyramids than in  the  cortical  portion of  the organ,
and consequently the matrix is more distinct in this situation; but
even here it has  only  a  faintly granular appearance, and we have
been unable to see any distinct fibres.
  It appears to us that this structure  is of little physiological im-
portance; it probably serves as a support for  the tubes and capillary
vessels.
  As the tortuous tubes in the cortex pass  in and out amongst the
interspaces of this matrix, portions appear to be circumscribed, as it
were,  giving the idea upon a section  of a number of small cysts,* an
appearance which is often very marked  in certain cases  of disease,
when  the tubes are  enlarged. In the kidneys of many rodents, espe-
cially in that of the mouse, this  appearance exists in a very marked
degree, in  consequence of the highly  developed condition  of the
matrix in these animals;  but, in  all the  instances alluded to, the true
* On Diseases of the Kidneys, by George Johnson, M.D. 
MALPIGHIAN BODIES.
789
Fig. 231.
structure of this part, and often the continuity of the tube as it winds
in and out, can be  demonstrated with  ease.   A thin section of  the
cortical  part  of the kidney, made in any direction, displays these
interspaces  containing  sections  of the  tubes, between  which may
often be seen vessels which have been cut across.
   Uriniferous Tubes.—The uriniferous tubes, formerly termed tubes
of Bellini, in which the characteristic elements  of the urine are  se-
creted, consist of two  distinct portions, as already alluded to ;  the
first, or highly convoluted part of  the  tubes,  which is probably  the
sole seat of true secretion, and the straight portion, which is directly
continuous with the former,  and conducts the  secretion  towards  the
opening upon the mammilla, from which it passes into  the pelvis of
the  kidney.  In the  other direction, the  convoluted portion  of  the
tube terminates in a dilated
extremity, which completely
invests  the vessels  of the
Malpighian tuft.*
   We  shall now  consider,
first,  the minute structure
of  the  Malpighian bodies;
secondly, that of the convo-
luted portion of the  tube;
and,  lastly,  that  of  the
straight portion.
  Malpighian Bodies.—The
Malpighian bodies are  met
with in all vertebrata.   In
the    mammalian   kidney,
where there exists a division
into cortical and medullary
portions,   they  are   only
found in the former.  In an
injected specimen, they ap-
pear to  the  unaided   eye,
as  coloured points  abund-
antly scattered  throughout
the  cortex of  the  organ.
They vary much in  size  in
different mammalia, and are
often  larger  towards  the
baseof the cones.  They are,
for   the  most  part, of  a
spherical, oval, or  flask-like
form.   A small artery affe-
rent vessel may be seen  to
enter the tuft, and a minute
venous  radicle efferent ves-
sel  to  emerge  from it  in
 From the human subject.  This specimen exhibits the
termination of a considerable arterial branch wholly in
Malpighian tufts, a. Arterial branch, with its terminal
twigs.  At a., the injection has only party filled the tuft.
At &, it has entirely filled  it, and has also passed out
along the efferent vessel ef, without any extravasation.
At y it has burst into the capsule, and escaped along the
tube t,  but has  also filled the efferent vessel ef.  At S
and i it has extravasated,  and passed along th» tube.
At m and m the injection, on escaping into the capsule,
has not spread over the whole tuft.  Magnified about 4o
diameters.
* Phil. Trans., 1842.
51 
790
KIDNEY.
close proximity to the artery (fig. 231).   The Malpighian body itself
consists of a rounded bunch of capillaries derived from the afferent
and  terminating  in the efferent vessel, the former dividing  over the
surface, the  latter emerging from the interior.   This vascular tuft
lies within a clear  and  perfectly transparent capsule, lined at its
lower  part with  epithelium.   The  epithelium, which is  continued
upwards  from  the uriniferous  tube  into  its flask-like dilatation,
cannot usually be traced for more than about one-third of the length
of the  capsule (fig. 3, p. 76);  but in the  proteus  (fig.  232), the
capsule is seen to be entirely lined with an exceedingly thin layer  of
delicate  epithelium, the cells of which are of  an oval, or polyhedral
form, with a very large granular nucleus, and  about the ?^ of an
inch in diameter.  The capsule itself consists of  hyaloid membrane,
which  is directly continuous with the basement membrane of the con-
voluted portion of the tube.  In fact,  each uriniferous  tubule termi-
nates by a dilatation which embraces the vessels  of the tuft, and  is
intimately united to them at the point where they enter and emerge.
   The continuity of the tube with the Malpighian capsule  has been
proved in several ways.   In specimens  which have been  carefully
injected from the artery, not unfrequently it will  be found that the
coloured material escapes and extravasates from the vessels of the tuft
into the cavity of the capsule, and thence runs down the tube (fig. 231).
   In disease, it  is not at  all uncommon to find the capsule of the
                                  tuft, and  the tube itself, injected
                                  with  blood,  in consequence   of
                                  hemorrhage  from  the vessels  of
                                  the  tuft.
                                    The difficulty of  injecting the
                                  capsule by forcing injection from
                                  the  pelvis of the  kidney, cannot
                                  reasonably be urged as an objection
                                  to  this view, for all who have had
                                  any  experience  in  injecting the
                                  minute ducts of glands, will  agree
                                  that it  is in very  few instances,
                                  indeed, that the injection can  be
                                  forced  to the  termination  of the
                                  tube.   The  epithelium within it is
                                  apt  to be  forced towards  its  csecal
                                  extremity, and by its accumulation
                                  renders such  a result impossible;
                                  while,  in  the  majority  of  cases,
                                  the  force requisite to overcome the
                                  resistance to the passage of fluid,
                                  along a highly convoluted  tube  in
                                  the  reverse direction to that  which
                                  its contents naturally take, is more
                                  than sufficient to cause its rupture.
                                    The kidney of the horse is very
                                  favourable for demonstrating these
Fig. 232.
 Malpighian tuft; kidney of the Proteus an-
jrnineus, showing vessels lying within the cap-
sule, the inner surface of which is entirely
covered with a single layer of tesseUated epithe-
lium,  a. Uriniferous tube. 5. Capsule,  c. Tuft
of vessels which were injected in the prepara-
tion from which this drawing was taken, af.
Terminal twig  of the artery.  ef. Efferent
vessel.  Magnified about 50 diameters.—A smali
portion of the capsule, with its epithelial lining,
is represented in the smaller figure, magnified
215 diameters. 
VESSELS UNCOVERED BY EPITHELIUM.            791
points, and the double  injection composed of acetate of lead and
bichromate of potash will be found to  furnish  the  most  satisfactory
results.
  In the kidney of  the  frog, or of the newt, the continuity  of the
capsule with the basement membrane  of the tube is exceedingly dis-
tinct and  easy of demonstration.   The tuft of vessels is seen lying
naked  within the capsule,  uncovered  either with epithelium or by
any reflection  of the basement membrane  composing  the capsule.
In  the frog, the neck  of  the  tube close  to  and some way within
the capsule is lined  with ciliated epithelium, which continues in very
active  motion many hours after the death of the animal (vide fig. 3,
p.  76.)   In the newt, and in some snakes and other  reptiles, the
tube is completely lined with ciliated epithelium throughout;  and by
the  activity of the motion, the epithelium can  be traced for one-
third  of  the way within the capsule.   Ciliated  epithelium  has not
yet  been  demonstrated in  the kidneys of mammalia ; but  in one
instance Gerlach has seen it in the kidney of the fowl.  In  various
fishes  and in many  reptiles it is very frequently met with.
   The statement of Gerlach and other  observers, that the vessels of
the  Malpighian tuft are invested with  epithelium, may be  explained
by the fact that small granular or nucleated cells may be frequently
observed  in  connection  with the vessels.  After repeated and careful
observation, we  are convinced  that these  cells  are situated either
within the vessel itself or enclosed in its wall (fig. 233).   In the
tuft of batrachian  reptiles,  the  white  cor-
puscles of the blood often give the idea of
being  connected with the wall of the vessels,
instead of lying in their  interior.  When
the vessels are  much shrunken, and their
walls  a little plaited, or corrugated, the ap-
pearance of cells lying  upon the little capil-
lary loops is produced when these loops are
 seen  in  profile.  We  have been able,  in
 many instances,  however,  to  demonstrate
 small  oval or circular  cells within the wall
 of the capillary vessel itself, and are in-
 clined to  look upon  these as  the nuclei of
 vessels.   Here  and there  a granular cell
 may sometimes be detected on  the surface, but they are very few in
 number and irregular  in  their arrangement; and we  are  satisfied
 that it cannot be regarded as a fact of  any physiological importance,
 and that the vessels of  the tuft are really bare within the  capsule.
    Convoluted Portion of the Tube.—-From the capsule of the Mal-
 pighian tuft, we pass to the convoluted portion of  the tube, which is
 directly continuous with it.  This is  composed  of a delicate  base-
 ment  membrane,  lined by epithelium.   Externally,  the basement
 membrane is  in close  contact and  probably incorporated with  the
 matrix of the organ; and it is in immediate  relation with an abund-
 ant capillary plexus, which carries  the  blood  after  it has passed
 Small portion of a loop of capil-
lary vessels of the tuft of the kid-
ney  of the  large water newt
(Triton cristatus), showing nuclei
within the wall of  the vessel.
The line above the vessel is the
outline of part of the capsule,
magnified 215 diameters. 
792
KIDNEY.
through the vessels of the Malpighian body.   It is from this  blood
that the elements characteristic of the urinary secretion are selected
by the epithelium lining this part of the tube.  The diameter  of the
tube is less immediately after leaving the tuft, than in the rest of its
course further down (fig. 234).  The epithelium  in  the convoluted

                               Fig.  234.
 Entire uriniferous tube of the large black newt (Triton cristatus, female),  a. Artery having upon
its walls numerous branched pigment cells.  The commencement of the tube, and that part near the
tuft, are of less diameter than the central portion, which is the most active part of the secreting tube.
Towards its termination in the upper part of the oviduct, d, the tube becomes straight and much
narrowed, c. Magnified about 30 diameters, from a drawing of Dr. Beale1 s.
portion of the tube presents an excellent example of the spheroidal
or glandular variety.   It consists of polyhedral particles rather less
than  Tqoo °f an incn in diameter, with  a distinct nucleus, and con-
taining numerous granules, and  occupying as much  as one-third or
more of the total diameter of the tube.
   The  extreme  diameter of the convoluted tube is about ^ig of an
inch, while the diameter of the central canal is not more than from
tthjo- t0 vhv of an inch-
   Straight Portion of the Tube.—The straight portion of the tubes
of which the medullary cones or pyramids are  composed form  anas-
tomoses, or if traced from the papilla towards the base of the pyra-
mid,  the large tubes near the apex  may be said to  divide  dichoto-
mously, so that the number of the individual tubes,  which would 
STRAIGHT PORTION OF THE TUBES.
793
 Transverse section of a pyramid of the human
kidney, about a quarter of an inch from the papilla.
a. Section of largest tubes, b. Section of smaller
tubes, at a point previous to their opening into a
larger one.  The thin delicate epithelium approach-
ing to the squamous variety,  is seen lining this
straight portion of the uriniferous tubes,  c. Small
vessels which ramify between the tubes in the
transparent granular matrix, d. Magnified about
120 diameters.
Fig. 236.
be seen  in a  transverse section,               Fig. 235.
increases as we proceed from the
apices of  the  pyramids  towards
their bases, while  their diameter
gradually  diminishes.    In  the
latter situation  there may  be
many thousand  tubes,  while the
number  of  openings  upon  the
extremity of  the mammilla are
comparatively very  few in num-
ber.   The tubes at  their orifices
vary in diameter, from  the 3^ to
the ^^  of an inch, while towards
the base of the pyramid  they do
not exceed g^ of an inch.   The
aggregate capacity  of  the  tubes
at the base of  a  cone is  enor-
mously greater than that of the
much smaller number of somewhat larger tubes at their orifices.
   The epithelium in this situation differs in
character  from that  in  the  convoluted  por-
tion  of  the tubes ;  the  cells are  smaller,
more transparent, and approach more nearly
to the scaly or  tessellated variety.   They
seem rather to serve as a  protective  layer
than  to  share  in  the  secreting  function.
The  cells here  are  usually very  thin,  ap-
proaching to squamous epithelium in  cha-
racter ;  and although the total diameter of
the tube is less than that of the convoluted
portion,  the diameter of the central  canal
is greater.
   Vessels of the Kidney.—The  renal arte-
ries divide into four or  five branches, which
enter the kidney at  the hilum between  the
vein  and the ureter.  These vessels are sur-
rounded with a quantity of fat.  They pass
between the papillae to the bases  of  the
cones over  which   they  spread.   From
these  arteries smaller  branches  are given
off, which  ascend  in the cortical substance
nearly to the surface, and, in so doing, give  off, on all sides, a number
of small terminal twigs,  the afferent  vessels  of  the Malpighian
bodies.  Arrived within the capsule, the small afferent vessel at once
divides into four or five  branches, each of which again divides dichoto-
mously.  The small capillary vessels form loops, which project towards
the opening  of the uriniferous tube.  The blood is received from these
vessels, which lie  towards  the  outside of the  tuft, by branches of
the efferent vessel which converge  towards the more central part of
 Malpighian tuft from the horse.
The injection has penetrated only
to the capillaries, a. The artery.
af. One of its terminal twigs (or
the afferent vessel), d. The dila-
tation and mode of breaking up
of the terminal twig after entering
the capsule.  The division of the
tuft into lobes, I, I, I, is well seen,
i, i. Intervals between the lobes.
Magnified about 80 diameters. 
794
KIDNEY.
Fig. 237.
the tuft  to  form  one trunk,  which leaves the Malpighian body, and
                           soon breaks up into  a plexus  of capillary
                           vessels, in the meshes of  which the tubes
                           lie.  The  terminal  arterial  twigs with
                           their appended  tufts, when injected with
                           vermilion, have been compared not inaptly
                           to  a bunch of currants.
                              The size and complexity of the Malpi-
                           ghian bodies  differ much in  different ani-
                           mals, according  to  the  activity  of the
                           function they are called upon to discharge.
                           The vessels  present fewer convolutions,
                           the tufts  are smaller, and their arrange-
                           ment  much  simpler, in those animals in
                           which the urine is almost of  a  solid con-
                           sistence.   Compare  the complicated  ar-
                           rangement in the horse and other mam-
                           malia in  figs. 236 and 237, with the few
                            and simple   convolutions  in  birds, fig.
                           238.
                              By reference to the table on next page,
                           it will be seen that  the  diameter  of  the
                           tuft in  the  parrot and in the boa, is less
                           than in any other instance recorded; and in
                           these animals, as is well known, the urine
                           is  almost solid.   It  is  especially worthy
                           of remark,  that the  uriniferous tubes  do.
                           not exhibit a  corresponding difference  in
                           dimensions.
 Malpighian tuft, from near the
base of one of the medullary cones,
injected without extravasation, and
showing the efferent vein branching
like an artery as it runs into the me-
dullary cone.  a. Arterial branch.
ef.  The afferent vessel,  to, m. Mal-
pighian tuft. ef. The efferent ves-
sel,  b. Its branches entering the
medullary cone.  Magnified about
70 diameters.
Fig. 238.
 From the parrot; injected by the artery,  a, a, a. Terminal branches of the artery, af af, af. Ter-
minal twigs of the artery, d. Dilatation of the terminal twig on entering the Malpighian capsule.
m. This dilatation more completely filled, showingits convoluted form ; and, ef, ef, the efferent ves-
sel, c. The Malpighian capsule filled by extravasation from the contained vessel, and the tub« t like-
wise filled. Magnified about 80 diameters. 
MALPIGHIAN TUFTS.
795
Table of the Diameter of Malpighian Bodies, and of the Tabes emerging
            from them, in Fractions of an English Inch.
					Diameter of Malpighian bodies.			Diameter of Tubes.
					Maximum.	Mean.	Minimum.	
Man Dog Rat Horse Parrot Tortoise Boa					T2o"	T54 T8ff ^5 4^0" 24 0" ¥50	lis	l 48ff 59 0" z\e ilS FffO" t0 705 jiff ?{"0"
  The  small efferent vessel from the Malpighian tuft passes at once
into the plexus round the tubes, and, as  it  lies between the  capil-
one  hand, and  that  surrounding

              Fig. 239.
lary plexus  of the tuft,  on the
the tubes upon the other, it bears
the same relation to these two
capillary systems as the portal
vein bears to those of the intes-
tinal canal and the liver ; hence
these efferent  vessels may be re-
garded  as analogous to a portal
system  of vessels.  This view is
further strengthened by an exa-
mination of  the arrangement  of
the vessels in the  kidney of the
boa  constrictor, figs.  239,  240.
In  this  animal,  the  blood, after
passing through the capillaries of
the Malpighian  tuft, enters the
efferent  vessel, which conducts it
into the branch of a  portal  vein
ramifying upon  the surface  of
the lobule. From the portal vein,
it passes into a system of venous
capillaries surrounding the tubes,
from which it  is  at last carried
into the emulgent veins,  which,
with the artery, lie in the central
part of the lobule.
  " The comparison between the
hepatic and the renal portal circulation may be thus drawn in more
general  terms.   The portal system of the liver has a double source,
one extraneous, the other in the organ itself;  so the portal system
of the kidney, in  the lower tribes, has  a  twofold  origin, one  ex-
traneous, the other in the organ itself.   In both cases, the extraneous
source is the principal one, and the  artery furnishing  the internal
source is very small.   But in  the kidney of  the  higher tribes,  the
 Plan of the arrangement of the elements of a
lobe of the kidney in the boa constrictor.  The
references are the same as in Fig. 210. 
796
KIDNEY.
portal system has only one internal  source,  and  the artery supply-
ing it is proportionably large."*
   Of the Secretion of Urine.—Having passed in  review the ana-
tomical arrangement of the different structures composing the kidney,
                                             we shall  now proceed to
                  Fig. 240.                    consider  briefly the func-
                                             tions which  the  several
                                             parts perform. First, with
                                             regard to the Malpighian
                                             tufts;  we  have already
                                             seen  that in animals, in
                                             which  the urinary excre-
                                             ment  is   passed   in  an
                                             almost  solid  form,  the
                                             tufts are  small and simple
                                             compared with those in
                                             the  kidneys  of animals
                                             which  pass  the urinary
                                             constituents in solution in
                                             a large quantity of water.
                                             There can be little  doubt
                                             that the  special function
                                             of  the vessels of the tuft
                                             is,  to  furnish  the  fluid
                                             portion of the urine, while
                                             the  solid  matter,  com-
                                             posed of various  organic
                                             constituents and inorganic
                           aid of the glandular epithelium which lines
                             the  convoluted  portion  of  the  tubes.
                             "It would, indeed, be  difficult  to con-
                             ceive a disposition of  parts more calcu-
                             lated to favour the escape of water from
                             the  blood than that of the Malpighian
                             body.   A  large  artery breaks up in a
                             very direct manner  into a number of
                             minute branches, each of which suddenly
                             opens  into an  assemblage  of vessels of
                             far greater aggregate capacity than itself,
                             and from which  there is but one narrow
                             exit.   Hence  must  arise a very  abrupt
                             retardation in  the velocity of the current
                             of blood.  The   vessels  in  which  this
                             delay  occurs are uncovered by any struc-
                             ture.  They lie bare in a cell from which
                             there is but one outlet."f  The arrange-
                             ment  of the  convoluted portion of the
                             tubes  is very  similar to that of  other
e>v
 Part of Pig 239 shaded, showing the arrangement of the
vessels and viriniferous tubes in the kidney of the boa, and
in animals furnished with a portal vein from an extraneous
source, a.  Artery,  af. Terminal twig going to Malpighian
body. ef. Efferent vessel of the Malpighian body emptying
itself into a branch of the portal vein,pi), on the surface of
the lobe, b, b. Ultimate branches of the portal vein entering
the capillary plexus, p, surrounding the uriniferous tube, t.
u. Branch  of the ureter on  the surface  of the lobe.  ev.
Emulgent vein within the lobe, receiving the blood from the
plexus surrounding the uriniferous tubes.  Supposed to be
magnified about 40 diameters.
salts, is separated by the

          Fig. 241.
 Plan of the renal circulation in man
and mammalia, a.  Terminal branch
of the artery, giving the terminal
twig,  1, to the Malpighian  tuft, m,
from which emerges the efferent or
portal vessel, 2.  Other efferent ves-
sels, 2, are seen entering the plexus
of capillaries surrounding the urini-
ferous tube, t.  From this plexus the
emulgent vein (■») springs.
* Phil. Trans., 1842.
f Phil. Trans., 1842. 
URINE.
797
secreting tubular gland-structures. We have a delicate basement mem-
brane in  contact with vessels upon one surface and having secreting
epithelium upon  the other.   The capillary network surrounding the
uriniferous tubes is the counterpart of that investing the tubes of the
testes;  and the epithelium is allied in  structure to the best  marked
examples of  glandular  epithelium,  and there can be no  doubt  that
the function of these cells is such as  we have described.   There is no
reason for supposing that the cells of epithelium undergo rapid decay
and  renovation ;  it  appears  more probable that they are not being
constantly shed,  either in an entire  or  disintegrated state, but  that
they have the power  of selecting certain materials from the blood,
and  afterwards giving them  up without  their destruction.  In the
straight portion of the tubes the epithelium becomes thinner,  and ap-
proaches more nearly to the pavement variety.   It  probably serves
principally  as a protective covering,  and takes no part  whatever in
the secretion of the urine.
                                 URINE.

  Healthy urine is a clear, limpid fluid, of a pale straw colour, emitting a peculiar and
characteristic odour while warm, and exciting a saline and somewhat bitter taste.   As
the solid constituents of this fluid are entirely excrementitious, and in  great part
derived from the disintegration of the tissues concerned in the chemical changes con-
nected with animal life, we should be led to expect that any alteration in the activity
of these functions would lead to a corresponding variation in the characters of the
urine.  Even  in a state of health the  qualities of the urine vary much;  and it has
been found that active exercise exerts a considerable influence upon the quantity of
some  of the most important constituents of this fluid.  Nitrogenous matter, taken in
greater quantity than is required for the wants of the system, will be eliminated by
the kidneys in the form of urea, and the composition  of the urine will therefore be
influenced by the character, as well as by the quantity of the food.*   If an unusual
quantity of water be taken into the stomach, a great proportion will rapidly be elimi-
nated by the kidneys, and the urine will be found to be very dilute, and of low specific
gravity.  Again, as the action  of the kidneys is  materially affected by the activity
with which the functions of the skin are discharged, the condition of this great  se-
creting surface has much to do with the quantity and quality of the urinary secretion.
Changes of temperature, for the same reason, will cause the urine to vary in quantity.
In hot weather, when the functions of the skin are increased, and a large amount of water
is in this way removed from the  system, in order to compensate for the effects of the
increased external heat, the urinary secretion is  much diminished in quantity, and
becomes more concentrated, while, in cold weather, when this cooling effect of evapora-
tion is not required, we find the amount of urine much  increased, and, therefore,
diminished in  density.   A dry, or humid state of the  atmosphere, in  consequence of
affecting  the  rapidity  of  cutaneous transpiration, will exert a certain  amount of
influence  on the quantity of water. It does not appear, however, that the quantity
of the solid constituents excreted in a given time  is much  altered by these circum-
stances.  The state of  the nervous system will often be found to have a decided influ-
ence in modifying  the  characters of this  secretion;  and various  mental emotions,
such as sudden joy, or fright, or anxiety, will cause the secretion of urine having a
much larger proportion of water than usual.
  All these circumstances, and many others of less importance,  have been found to
affect the characters of healthy urine; and, on this account, considerable difficulty has
been felt in attempting to define the precise characters of the secretion  in health.
Again, the composition of the urine differs at different periods of life, but in a much

  * The frequency with  which we meet with an excess of urea in the urine of our country-
men is probably dependent in some  measure upon the highly nitrogenous nature of our
food.  On the continent of Europe this is so rare, that some foreign observers appear hardly
to credit the statements with reference to the frequent presence of excess of urea. 
798
URINE.
Fig. 242.
less degree in different individuals at the same period.  The urine of men, in the
prime of life, contains more solid matter, and less water, than that of old men, women,
or children.
   Quantity of  Urine.—The quantity of urine discharged in the course of twenty-four
hours, in  a state of health, varies  very much, but it may be said to amount to about
30 or  40  ounces.   The density varies  from 1-010 to 1020 or 1025 and the quantity
of solid matter from 4  or 5  to  8 per cent.  The amount of solid  matter eliminated
                                                        from the kidneys of a healthy
                                                        man who  lives well  may be
                                                        roughly stated to be  about
                                                        1000  grains in twenty-four
                                                        hours.
                                                          Reaction.—Healthy  urine
                                                        exhibits an acid  reaction;
                                                        but the intensity of the re-
                                                        action  varies  at  certain
                                                        periods of  the days.   Dr.
                                                        Bence Jones, who has lately
                                                        investigated  this   subject,
                                                        found that  the urine  was
                                                        most  acid immediately be-
                                                        fore meals, and the intensity
                                                        of  the acidity  diminishes
                                                        until  five or six hours after
                                                        the meal.   This condition,
                                                        occurring  in  the urine se-
                                                        creted  soon after  digestion,
                                                        depends upon  the quantity
                                                        of alkali set free in the blood
                                                        inconsequence of the decom-
                                                        position of certain salts which
furnish the acid entering into the composition of the gastric juice.
  The reaction of healthy urine has been attributed to the presence  of free  lactic
acid, and  also to acetic acid; but the investigations of Liebig have rendered it probable
that it depends, not upon the existence of free  or uncombined acid, but upon the pre-
sence of certain  salts which  exhibit a decidedly acid reaction, although there is no
free or uncombined acid.  Such salts are presented to us in the phosphates, which have
the property of being very readily changed  from the  alkaline to  the acid,  or super-salt.
  a. Various forms of lithic acid crystals.  5. Deposit of lithate
of soda, amorphous, c. Lithate of soda forming spherules with
irregular crystals projecting from them.  d.  Oxalate of lime.  e.
Dumb-bell crystals of oxalate or oxalurate of lime.
Fig. 243.
  Casts of the uriniferous tubes,  a. Casts with epithelium, at a; a free cell of epithelium,  b. Very
large cast containing epithelium,  c. Small granular casts,   d. Small  waxy cast.  e. Casts  contain-
ing fat cells and free oil, at x cell filled with fat globules.  /. Pus globules, at x once acted upon by
acetic acid. 
COMPOSITION OF HEALTHY URINE.
799
Fig. 244.
  a Crystals  of triple phosphate.
variety.  6. Granules of phosphate of lime.
Crystals of cystine.
  After standing for some hours, healthy urine deposits a slight precipitate, forming a
light flocculent cloud, consisting of vesical mucus, and a little epithelial debris. ^ This
deposit is much more abundant in the urine of women, in consequence of the admixture
of a considerable quantity of vaginal epithelium.   Not unfrequently, epithelium from
the urethra, or bladder, will be found in this deposit, and spermatozoa are occasionally
met with.  In disease, the deposit may consist of pus, or blood-corpuscles, and fibrin-
ous moulds of the uriniferous tubes,* entangling cells of renal epithelium, which may
contain many oil globules, and  crystals of
oxalate of lime, pus, or blood globules, are
sometimes found.   In such cases, the urine
will also contain albumen.   Among the de-
posits most frequently observed, may be
mentioned the amorphous deposit of lithate
of soda, crystals of lithic acid, of oxalate of
lime, of triple  or  ammoniaco-magnesian
phosphate, and occasionally crystals of cys-
tine.
   Composition of Healthy Urine.—The urine
is a highly complex fluid, and contains sub-
stances having very different properties. Its
constituents are composed partly of organic,
and partly of inorganic compounds which
are held in solution in the aqueous portion
of the secretion.  A small quantity of carbonic acid gas is likewise often found held in
solution. The chief organic constituents of healthy urine are the following: urea, uric
or lithic acid, and certain extractive matters,  with small quantities of creatine, creatinine,
 hivpuric and lactic acids, and ammoniacal salts.   The inorganic constituents consist of cer-
 tain  salts which enter into the composition of the food, but which are not required for
 the wants of the system, and salts which, having performed certain offices by their pas-
 sage through the tissues, are no longer required,  and certain other saline compounds,
 which  like many of the organic constituents,  are formed by oxidation in the processes
 concerned in nutrition.  The inorganic salts are  composed of chlorides, sulphates, and
 phosphates, with traces of silica, and the bases entering into the composition of these salts
 are, potash, soda, lime, and magnesia.   It is  exceedingly difficult to ascertain the precise
 composition of the salts as  they were originally held in solution in the urine; for, in
 the processes of evaporation, and subsequent incineration, certain decompositions take
 place, which entirely alter their nature.  The quantities in which these  substances
 occur, vary in different specimens of urine, and  the published analyses of the secre-
 tion  in a healthy state, will  be found to  differ  considerably from each other.   This
 difference arises chiefly from the variation in the proportion of water; for, by calcu-
 lating the relation existing between the quantities of the several solid constituents, it
 will  be found to be nearly  the same in all.
   The following is an analysis of  healthy human urine, by Dr. Miller.  The percent-
 age composition of the solid matter is shown in a separate column.  Specific gravity,

 I-020-                                                                In 100 of
                                                                     Solid matter.
      Water.........956'80
      Solid matter  ....
Organic matters
    29-822
Fixed Salts
  13-158
[" Urea  .
  Uric acid  .
  Alcohol extractive
  Water extractive.
  Vesical  mucus
  Muriate of ammonia
f Chloride of Sodium
I  Phosphoric acid .
|  Sulphuric acid  .
\  Lime .
I  Magnesia  .
|  Potash
[ Soda .
14-23	3310
•37	•86
12-53	29-15
1-60	3-72
•17	•39
•91	211
7-22	16 79
212	4-93
1-70	3 95
•21	•48
•12	•27
1-93	4-40
•05	•11
999-96
* Diseases of the Kidney, by George Johnson, M. D. 
800
URINE.
   Urea (C2 H4 N2 02) constitutes nearly half of the solid matter of healthy urine, and
the secretion itself contains from 2-5 to 3-2 per cent, of this substance.   The quantity,
however, is  much  increased by exercise, or by a purely animal  diet.   According to
Lehmann, when a highly nitrogenous diet is taken, a quantity of  urea equal to nearly
five-sixths of the nitrogenous matter introduced is eliminated by the kidneys.   A con-
siderable quantity of urea,  however, is formed when no  food whatever is taken, or
when a non-nitrogenous diet is adhered to for a considerable period,  which  clearly
shows that a large proportion of urea is derived from the disintegration  of the tissues,
by the process  of secondary assimilation.  It is often detected in abnormal quantity
in the urine of patients suffering from rheumatism, and certain febrile complaints, and,
in various diseases, it may sometimes be obtained from this fluid  in very large quanti-
ties.  This condition is very commonly associated with diseases  of  the kidneys, and
leads to the development of coma, which is often fatal.   Urea has been detected in the
blood of patients suffering from cholera, and once by Dr.  Garrod, in that of a gouty
patient.  In the serous fluids poured out in various parts of the body, in cases of kid-
ney disease, as well as in several of the secretions, such as the saliva, &c, it has been
found in  large quantity.  Dr.  Owen Rees has met with it in  milk, and the same ob-
server, and  Wohler,  have found it in the liquor amnii, an observation, however, which
others have failed to confirm.   It has been detected in the aqueous  and vitreous hu-
mours of the eye.
  There can be little doubt  that urea is formed in the blood by the action of oxygen
upon lithic  acid, creatine, and, possibly, upon some  of  the matters  comprehended
under the indefinite term of extractive matter.   In a state of health it is  so rapidly
separated from the circulating  fluid, in its passage through the kidneys, that its pre-
sence is not easily recognized;  but, in animals in which these organs have  been ex-
tirpated, it accumulates in sufficient quantity in the blood to be detected with facility.
Urea cannot be extracted from the muscles, although it is probable that the greater
quantity excreted  is formed from the effete materials produced  by muscular action,
since the quantity of urea is so much  increased by exercise, and is also  produced,
although only non-nitrogenous  food be taken.   At the same time, it is almost certain,
that if an amount of nitrogenous food greater than is required by the wants of the
system, be taken, the excess becomes converted into urea, and is eliminated from the
system by the kidneys.*
   Uric or Lithic Acid (Ci0H4N4O6) is always present in healthy urine, and exists  in
the proportion of about one part in a thousand.  It may very readily be obtained by
the addition of a few drops of  hydrochloric acid to a portion of the  urine placed in a
conical glass vessel.  After the lapse of  a few hours,  the uric acid is found deposited
in the form  of small  crystalline grains, adhering to the sides or collected at the bottom
of the glass.  Uric  acid prepared in this manner is always highly coloured, which
arises from the circumstance of its having a great affinity for the colouring matter of the
urine.
   Uric acid exists in healthy urine in combination with soda, and perhaps  also with
ammonia and lime;  as these salts are only present in small quantity they are held in
solution, but in the urine of patients suffering from fever, they often form an abundant
deposit, which, in this  country, is  generally known as lithate of ammonia, although
Lehmann, Becquerel, and Heintz, all agree that it is composed principally of lithate
of soda.
   In the urine  of the carnivora,  uric  acid is present in small quantity, but,  as a
general rule, it is absent from the urine of the herbivora; and, curiously enough, also,
it cannot be detected in the urine of the omnivorous pig.   The excrement of birds,
and that of serpents and other  reptiles, and of many insects, contains a  large quantity

  *  It has lately been advanced by Dr. Frerichs, that in cases  in which the urea is pre-
vented from  being eliminated from the blood, either by the extirpation of the kidneys (as  in
his experiments upon animals), or in cases in which the functions of these organs have been
impaired  by disease  (as  in certain forms of Bright's kidney), this substance  is resolved,
whilst in the circulating blood, into carbonate of ammonia; the presence of which, according
to this observer, gives rise to the coma which so frequenUy carries  off patients in an ad-
vanced stage of renal disease.   We should, however,  state, that  this view has  not yet
received confirmation from the experiments of others.  That a considerable quantity of urea
may be present in the blood without giving rise to any serious  symptoms, we can affirm
from actual experiment;  but at the same time, we consider that there is sufficient evidence
to prove that the coma, in many  cases of kidney disease, is dependent upon the presence of
urea.  We have tested the breath of a few patients suffering from  this form  of coma, in
King's College Hospital, and have also examined the blood, but have failed to demonstrate
the presence of carbonate of ammonia. 
EXTRACTIVE MATTERS.                        801
of alkaline urates.  Guano, as is well known, is chiefly composed of lithate of ammo-
nia.
  After profuse perspiration, the quantity of uric acid has been found to be diminished
in the urine; but a purely animal diet exerts but little influence upon the quantity of
this substance excreted by the kidneys.  It is much increased, however, in all febrile
conditions of the system, and after imperfect digestion  of food.  In cases where the
respiratory function is impaired, the amount of uric acid has been found to be abnor-
mally increased;  and insufficient exercise will produce a similar effect.
  Uric acid  has been detected in the blood of healthy men by Garrod, and in consider-
ably increased proportion  in the blood of gouty patients.   It has also been detected
in the perspiration, and the deposits formed  about the joints of gouty persons are
largely composed of it.
  According to Wohler and Frerichs, the  introduction of lithic acid into the blood is
followed by  an increased secretion of urea and  oxalate of lime in the urine, a point of
considerable interest when we know that, by the influence  of peroxide of lead, a simi-
lar decomposition of the lithic acid may be induced artificially.
  When  all these  circumstances are  considered, more especially that,  in certain
instances in which  the respiratory changes are not carried on with the activity con-
sistent with perfect health, a greatly increased quantity of lithic acid is eliminated by
the kidneys, there appears ample evidence to show that lithic acid is one of the purely
excrementitious substances derived from the disintegration of the tissues, and formed
by the action of oxygen upon effete material.   By a process of further oxidation, the
lithic acid itself becomes converted into urea as we just now mentioned.
  Eippuric  Acid (C,8 H8 N06, HO),  according to  Liebig, exists in  small quantity in
healthy human urine,  but it is  obtained in considerable quantity from  the urine of
horses, cows, and other herbivorous animals.   It is quite inodorous, has a rather bit-
ter taste, is slightly soluble in cold, but very soluble in hot water and alcohol, charac-
ters in which it differs from uric acid.   It is  easily prepared from the urine of cows
by precipitation by hydrochloric acid, and subsequent purification.   It is,  however,
absolutely necessary that the urine  should be perfectly fresh, otherwise the hippuric
acid will be found to have been entirely converted into benzoic acid, a change which
may also be induced in the pure acid by the action of heat and mineral acids.  It  has
been stated by Mr. Ure, that if benzoic acid be taken, it is eliminated from the system
as hippuric acid.
   Hippuric  acid has been found  in  the urine of many herbivorous animals, and by
Lehmann in that of the tortoise (Testudo Graeca) and many herbivorous insects.   It
is  not present  in  the urine of  the carnivora.   In cases of  diabetes, it  is stated
by the same observer to  be never absent from the urine;  and in health, may usually
be detected if the diet be purely of a vegetable character.   This acid, like uric acid,
must be looked upon as an excrementitious substance, and plays no other part in the
 system.
   Creatine (C8 H9N3 04) occurs  in very small quantity in the urine.  It is a colourless
 crystalline body, with  a strong pungent taste, soluble in cold, and very soluble in boil-
 ing water;  it is  almost  insoluble in alcohol.  Boiled with baryta water, it becomes
 changed into urea and sarcosine;  and it is probable that a somewhat similar  decompo-
 sition ensues within the organism, and that, of the quantity of creatine formed in the
 muscular fibre, a large proportion is eliminated from the system in the form of urea,
 and partly, perhaps, as carbonic acid and ammonia.
   Creatine  was obtained, in the  beautiful investigation of Liebig, from  the flesh of
 various animals; but the proportion in which  it exists is so small  that it  can only be
 extracted with  great  care, and by operating  upon large quantities.  It occurs most
 abundantly in the flesh of fowls, and in the heart of the ox.
   Creatinine (C, H7 N3 02) is also met with in  the urine, and its presence in this fluid
 was discovered by  Liebig, to whom we are  indebted for all that is known in reference
 to this body. Creatinine crystallizes in colourless crystals.  It possesses a hot, burn-
 ing taste, compared to caustic ammonia.   It is soluble in water, and, unlike creatine,
 is freely dissolved  by spirit.  It  is found, with the last mentioned body, in the juice
 of muscular fibre.  Creatinine may be formed by the action of hydrochloric  acid upon
 creatine a  change  which renders it probable that it is also formed from the last named
 body in  the organism.   In urine, creatinine exists in  larger quantity than creatine;
 while in muscular  fibre the latter is found to exceed the former in amount.
   Extractive Matters.—'Under this very unsatisfactory term are included certain sub-
 stances met with in the urine, blood, and other animal fluids which are not easily iso-
 lated whose properties are with great difficulty determined, which do not crystallize,
 are not volatile without decomposition, and cannot be obtained in a pure form.   Of 
802
URINE.
late years, however, several substances  have been separated from the extractive mat-
ters which were formerly included under that term. Of these, albuminate of soda, crea-
tine, and creatinine may be  referred to as examples.  These  extractive matters  no
doubt play a most important part in vital chemistry, and probably represent a stage
intermediate between the nutritive pabulum and the tissues formed from it, or between
the latter in process of disintegration and the  compounds we have been considering,
such as urea, lithic acid, etc., but in the present state of our knowledge, little beyond
mere speculation can be advanced.
  Our friend, Dr. G. 0. Rees, found  that, in cases  of albuminuria,  connected with
kidney disease, large quantities  of the  extractive matters of  the blood passed off in
the urine as well as albumen.   The test which Dr. Rees employed for detecting the
presence of the blood extraction was the tincture of  galls.*
  Ammoniacal Salts.—Ammonia exists in very small quantity,  if, indeed, it be present
in healthy urine, but in disease a considerable  proportion may occur.   It  has been
found as hydrochlorate, lactate, biphosphate, ammonio-magnesian or triple phosphate,
and in the form of phosphate of ammonia and  soda.   Its presence usually depends
upon the decomposition of some of the  nitrogenous constituents of the urine, as pre-
viously indicated.
  Fixed Salts.—By the careful incineration of urine, we obtain the fixed salts, and  we
find that, of the  saline  residue, part is soluble and part insoluble in water, the latter
having  been previously held in  solution  in the  urine  by some material which has
been destroyed by a red  heat.   Although the  presence of  certain acids and certain
bases in the ash is readily demonstrated, the precise manner in which these were ori-
ginally united together  is not so easily ascertained.
  The most important  saline constituents of normal  urine are chlorides, sulphates,
and phosphates; and the following bases are present—potash, soda, lime, magnesia,
with traces of silica and peroxide of iron.
   Chlorides.—The chlorine exists in combination with sodium, in the form of common
salt, and perhaps also occasionally as hydrochlorate  of ammonia.   Almost the whole
of the chloride of sodium is probably derived  from the food ; although, from  recent
investigations, it appears  probable that this substance plays an important part  in the
development of tissues, and also in certain morbid changes.   In growing tissues, it is
always abundant, and in the fluid on the surface of healing ulcers  it exists in large
quantity.f
  Sulphates.—The sulphuric acid exists in combination with potash, and perhaps also
with soda.   The  sulphates are highly important 6aline constituents, and their propor-
tion is much influenced by the activity of the vital functions, and also by an animal
diet.  After exercise, the amount of the sulphates, as well as that of the urea, under-
goes an increase ; and it has been found that  in Chorea (a  disease characterized by
inordinate action of the muscular system) a large quantity of  these salts are excreted
in the urine. J   The sulphuric  acid is, doubtless, in great measure produced  by the
oxidation of the sulphur contained in the proteine compounds.  Unlike the chlorides,
the sulphates are not present, or are only met  with in very small  quantities,  in the
fluids of the body generally, with the exception of  the  urine, a circumstance which
points to the importance of the former in the organism, while it clearly shows that
the latter are not required in  the  nutritive  changes, and  are, therefore, only to be
found in the excrements.
  Sulphuretted Hydrogen is from time to time detected in urine.   Dr.  Beale met with
it frequently in  the urine of insane patients.   Sulphur is no doubt eliminated in
considerable quantity in the urine in certain cases.   Cystine  contains as much as 26
per cent, of this substance.
  Phosphates.—Phosphoric acid is found in combination with soda, lime, and magnesia;
the salts thus constituted have been spoken of as alkaline or earthy phosphates,  the
former term being confined to the combination of phosphoric acid with soda and  the
latter to the phosphates of lime and  magnesia,  which are precipitated from healthy
urine by the simple addition of excess of  ammonia.
  The large amount of  phosphates present in urine  is chiefly derived from the food
but part results from the oxidation of the phosphorus which is contained in the tissues'
the particular tissue  concerned  in  the formation of  this phosphoric acid being the
nervous, which,  it is well known, contains a large  proportion of  phosphorus.   Dr.

  * Lettsomian Lectures.  London Medical Gazette, vol. xlviii., 1851.
  t " On the Diminution of the Chlorides in the Urine in  Cases of Pneumonia," by Lionel
Beale.  Med.-Chir. Trans., vol. xxx.                                         J
  t Dr. Bence Jones.  Med.-Chir. Trans. 
PELVIS OF KIDNEY.
803
Bence Jones foun 1 an increase in the quantity of the alkaline phosphates in the urine
of some cases of inflammation  of the brain, and a diminution in quantity in cases of
delirium tremens when no food was taken;  but in the latter case the diminution is,
probably, too slight to be recognized.   This circumstance would account for the result
of several  experiments we have ourselves  made upon this point, in which we have
found no diminution in the quantity of phosphates.
  To  sum up, the kidneys appear  to be  special organs for the removal of effete ma-
terial produced in the vital processes from the system,  and  they serve as channels for
the elimination of water and certain saline matter, as well  as excess of nitrogenous
material which is not required for the maintenance of the tissues.   The chief con-
stituents of the urine consist of compounds resulting from the action of oxygen upon
the albuminous or allied substances; and in urea and uric acid we  have probably ex-
amples of the highest state of  oxidation which  the chemical elements  of  the tissues
are capable of undergoing, and urea may be looked upon as the last of a series of com-
pounds resulting from the successive action of oxygen  upon those bodies which stand
above it on this scale.  The fixed salts which occur in urine also  exist  in a highly
oxidized state.   There can be little doubt, that the highly complex substances entering
into  the  formation of the tissues, by chemical action taking place in the organism,
become resolved into bodies of a more simple composition, until they are  eliminated
in the form of urea or some allied compound, the elements of which are so loosely
combined, that by external circumstances alone new substances are formed of a still
simpler  composition, such as  carbonic acid and ammonia.  In these, however, the
elements are united with such force, that it is only by most powerful  chemical action,
or by the still more powerful influence of the vital properties of plants, that they can
be separated from each other, and  again applied to the building up of those highly
complicated substances of which the tissues of animals consist, and which, by their
vital processes, are again reduced in complexity as before.
   The more actively the vital phenomena are performed, or, in other words, the greater
the rapidity with which the disintegration and repair of the tissues take place, the
larger is the quantity of urea excreted from the system.  With this increase of the
urea, there is certainly a corresponding increase of  the  sulphates, and perhaps  also
of the phosphates.  If, however, the activity of these changes be  interfered with, as
from  impairment of the respiratory apparatus, or  from other causes, as might be
expected, we find an increase of that constituent which stands next above urea in the
descending series of compounds resulting from oxidation,  namely, lithic acid.  This
finds its way out of  the system in the form of lithate of soda, forming the amorphous
sediment generally known as lifhate of ammonia,  but which really consists almost
entirely of lithate of soda.   Under similar circumstances, we often meet with a de-
posit of oxalate of lime.  The urine of the active carnivora contains, like that of man,
a large quantity of urea; on the other hand, the urine  of serpents  and many other
reptiles consists almost entirely of uric  acid in combination with ammonia.  The urine
of birds much resembles in character that of serpents,  which appears somewhat to
be opposed to the doctrine we have been endeavouring to inculcate, as the vital changes
are carried on with greater activity in  this than in any other class of  animals;  but,
on the other hand, it may be argued, that the demand  for oxygen is so great in birds,
and their vital functions so actively carried  on, that the extensive respiratory appa-
ratus necessary for the supply of sufficient oxygen to convert all the uric acid  into
urea would be incompatible with the lightness  of their bodies, which is so necessary
for flight;  while the removal of the urinary constituents in a state of  solution involves
the  necessity of a bladder, or receptacle, in which it can collect, and which would
still further add to the weight.  We find in the minute anatomy of the bird's lung a
beautiful arrangement by means of which not the smallest  space where blood can be
exposed to the action of air is lost.   ( Vide p. 715.)

   Pelvis of Kidney and Ureters.—The mucous  membrane lining the
pelvis of the kidney is continuous with that of the renal tubes at  the
point where  they open upon the papillae, in which situation it is ex-
ceedingly thin, and it is  difficult  to  distinguish  its epithelium.   The
epithelium of the pelvis of the kidney generally is polygonal in form,
and constitutes a  tolerably thick layer.   The deeper cells are small
and rounded.   Many cells  approaching  to the  columnar form may
also be observed ;  and these increase  in number  towards the  ureter,
which tube is lined  with  this variety of epithelium. 
804
BLADDER.
   The ureters have muscular coat composed of two  layers, an  in-
ternal layer of circular, and  an external one of longitudinal fibres.
These are prolonged upwards into  the pelvis of the kidney, and cease
at the calyces.  The muscular coat is composed entirely of unstriped
muscular fibre cells, the  nature of which  will  be particularly de-
scribed when we come to speak of  the uterus, and it is invested with
an external coat composed of fibrous tissue.
   The ureters reach the base of the bladder, run  obliquely through
its coats for the distance of nearly an inch, and open into this viscus
by two  narrow slit-like  openings  about  an inch and  a half behind
the prostate on its inferior surface, and  separated from  each other
by the distance of nearly two inches.  The openings readily permit
the urine to pass into the bladder ; but, by their  arrangement,  com-
pletely prevent its reflux  into  the ureter;  the reflection of mucous
membrane  at their mouth serves the office of a valve.
   We have already referred  to the  contraction of the ureters in p.
765  of the present volume.
   Bladder.—The urinary bladder  is the large receptacle  into which
the urine is poured and in which it  accumulates as it escapes from the
ureters.  Its size varies very greatly:  it may be distended to such a
degree  as  to  contain nine, or even twelve  pints of urine, in which
case its walls of course become exceedingly thin, or it may be  con-
tracted so much as to leave scarcely any visible cavity in  its interior.
Its contracted muscular walls may be found half an inch or more in
thickness, a condition very often met with in cases of cholera.
   The internal surface of the bladder has a reticulated appearance,
owing to  the arrangement of the  muscular fasciculi.  The mucous
membrane  is sometimes forced through the small spaces between the
fibres, and  thus a number of sacculi are produced, a condition termed
sacculated bladder.
   At the lower part of the bladder is  a perfectly smooth and pale
surface, of the form of an equilateral triangle, the apex of which
points towards the prostate.  The  ureters  open one at  each of the
posterior angles ; and between them there is a prominent line caused
by the mucous membrane being somewhat  raised in this situation.
This triangular portion of the floor of  the bladder is called the tri-
gone (triangle), and the mucous membrane  is attached more firmly
than in other parts to the muscular coat beneath, whence its smooth
character.  The bladder is only partially covered with peritoneum.
It is connected in the male with the rectum, and in the female with
the uterus and upper part of the vagina by much loose areolar tissue,
which permits great freedom of movement of these parts upon  one
another.
   The bladder is kept in its position by certain reflections of peri-
toneum passing over bands of  white fibrous  tissue, or reflexions of
the vesical fascia (true ligaments),  and  by folds of peritoneum alone
(false ligaments).
   The anterior reflections of the vesical fascia constitute the anterior
true  ligaments of the bladder.  These  arise from the lower margin
of the pubis on each side of the  symphysis.  They then pass over 
EPITHELIUM OF BLADDER.
805
 the upper surface of the bladder.   Many of these fibres are attached
 to the muscular fibres, and this ligament may be said to serve as the
 tendon of attachment of many  of the fibres which constitute the
 detrusor urinse muscle.
   The fundus of  the bladder is connected with the umbilicus by the
 suspensory ligament of the bladder, a reflection of peritoneum which
 encloses the obliterated hypogastric arteries and urachus.
   The muscular coat of the bladder is composed entirely of unstriped
 fibre-cells, which  are much interwoven, but may be  described as ar-
 ranged in two layers, an external longitudinal, and an internal trans-
 verse or circular.
   The latter are exceedingly numerous round the neck of the bladder,
 whence they have received the name of Sphincter Vesicae.
   The longitudinal fibres are most abundant upon the anterior and
 posterior surfaces of the bladder, and constitute the detrusor urince
 muscle.
   The mucous membrane is of a pale colour, and is loosely connected
 to  the muscular  tissue by the  intervention of much loose  areolar
 tissue, in which the yellow element is abundant, except over the tri-
 gone,  where it adheres  very firmly,  by which  a perfectly  smooth
 surface is produced in  this situation.
   About  the neck of the bladder are a number of small glands, each
 consisting of a few secreting  follicles, opening into a short wide duct.
 These are lined with columnar epithelium, and secrete  a perfectly
 clear transparent  mucus.
   Epithelium.—The epithelium  of the bladder varies much in its
 character in different situations.   Near the orifices of the ureters it
 is almost entirely  of a columnar form;  but over the fundus, generally,
 it consists of large  circular  and  oval  cells, with a distinct nucleus.
 These are of very large  size, and  present  a very  characteristic ap-
 pearance.   Kolliker describes many  of these  large cells as lying
 upon the surface  of columnar epithelium,  their  deep aspect being
 hollowed  out to receive the  summits  of  the latter cells.  Towards
 the urethra, the columnar  epithelium again predominates.  Epithe-
 lium from various parts of the mucous membrane above referred  to
 is often found in the urine ; and the characters are often so distinctive
 as to  enable the  observer to infer with accuracy the locality from
 whence it was derived, a point which is  occasionally of some value
 in diagnosis.
   We shall consider the  anatomy of the urethra, and other organs
 connected with the bladder, in the chapter on tho Organs of Genera-
 tion.

  The student should consult the following works and monographs for more detailed
information upon the  subjects treated of in the present chapter: M. Malpighi, de
Renibus, 1669; Schumlansky, de Structura, renum, 1788; W. Bowman, in the Philo-
sophical Transactions for 1842;  Goodsir, in the Monthly Journal of Medical Science,
1842; Dr. Johnson's article, " Ren," in the Cyclopaedia of Anatomy and Physiology,
and his work on Diseases of the Kidney;  and the treatises on Physiology and Minute
Anatomy before referred to.                                        ,
  Upon the  Urine.—Dr.  Golding Bird, on Urinary Deposits; Dr.  Bence Jones s Lec-
tures upon Animal Chemistry; Lehmann's  Handbuch der  Physiologischen Chemie,
       52 
806
SPLEEN.
Leipzig, 1854; translated by the Cavendish Society.  J. E. Bowman, Medical Che-
mistry.  Beale, on the Microscope, and its application to Clinical Medicine, Chapter
XIV.
                      CHAPTER XXXV.

ON  THE DUCTLESS  GLANDS.—SPLEEN.—ITS CAPSULE.—TRABECULAR
  TISSUE.—SPLEEN PULP.—SPLENIC ARTERY. — MALPIGHIAN CORPUS-
  CLES.--VEINS OF THE SPLEEN. — LYMPHATICS.—NERVES.—CHANGES
  IN THE BLOOD IN THE SPLEEN.—USES OF  THE  SPLEEN.—SUPRA-
  RENAL  CAPSULES.—THYROID BODY. — USES  OF   THE  THYROID.—
  THYMUS.—USES OF THE THYMUS.

  We have now to  consider a remarkable class of organs present in
all  the  mammalia, which resemble  the secretory glands  already
described in  external  conformation and in  the possession of a solid
parenchyma, but differ from them in the absence of any excretory
apparatus suitable for carrying off the products of secretion.   These
organs  cannot be associated with  such structures as the liver, the
kidneys, and  the other glands;  inasmuch as  they not only differ from
them in the essential particular just  mentioned ; but they exhibit in
their internal structure no mechanical  arrangement  clearly adapted
to a secretory function;  nor is any material (save  in the case of the
thymus) to be obtained  from  them  bearing  any  resemblance  to  a
secreted product.   Many physiologists, however, suppose  that these
organs  do exert an attractive  influence on certain  matters in the
blood, and separate them from it; but this  hypothesis necessarily
involves a second  and  a less plausible  one, that the matter thus
extracted must re-enter the circulation.
   These bodies  agree in  the common  characteristic, that their paren-
chymatous portion  consists of  cells and cell-nuclei, with bloodvessels
in great number variously disposed.   They may probably be regarded
as appendages to the vascular  system,  and, from the absence of any
excretory duct,  they are usually designated  vascular ductless glands:
under this head are grouped—the spleen, the supra-renal capsules,
 the thyroid body, and the thymus.
   Spleen.—The spleen is of an oval form and somewhat compressed;
its internal surface is  concave, and its external surface is in contact
with the diaphragm.   The spleen lies in the left hypochondrium, and
extends upwards as high as the tenth rib, but when enlarged reaches
much higher, and increases upon  the lower part of the thoracic cavity.
 The spleen  is of a dark red  colour, highly  vascular,  and of a soft
 pulpy consistence; it varies much in size,  according to the state  of
general nutrition, and also at different periods of the digestive process.
 The weight of the spleen compared to that  of the  body at birth, is  as
 1 : 350, in adult life, 1 : 320, and in old age, as 1 : 700.  The following
points have to be noticed in  considering the structure of the spleen : 
TRABECULAR TISSUE OF THE SPLEEN.
807
the capsule, the trabecular tissue, the spleen pulp, or proper splenic
parenchyma, and the arrangement of the arteries, veins, nerves, and
lymphatics.
   Capsule of the Spleen.—The spleen is covered by a reflection of
peritoneum, which extends to it from the fundus of the stomach, and
is  called the gastrosplenic omentum.   The  proper  capsule of the
spleen is  composed  of white  and yellow fibrous tissue, and permits
of considerable distension.  It envelops the organ  entirely, and is
prolonged  into  the  interior upon  the vessels, which are  inclosed in
sheaths composed of a structure  closely resembling  the capsule of
the organ.  In man  there is an absence of muscular fibre-cells  in the
capsule, but in  the dog and pig, and some other mammalian animals,
they are very numerous.
   Trabecular Tissue of the Spleen.—If a section of a spleen be care-
fully washed under a stream of water, the dark coloured, soft, pulpy
matter is removed,  and a perfectly white  and complicated fibrous
meshwork remains.   The interspaces  bounded by these trabeculse
vary much  in  size and form; but they are all intersected by still
smaller trabeculse, and these smaller spaces by fibres visible only by
the aid of the  microscope.   The network thus formed, much resem-
bles that of the corpora  cavernosa penis,  and  the fibres composing
it are intimately connected with the fibrous capsule of the  organ,
and also with the sheaths of the vessels supplying
it.  The  spaces or  interstices communicate freely      Fis- 2^
with each other, and in them  is situated the pulpy
tissue of the spleen.
   The larger trabecules, like  the fibrous capsule of
the organ, are  composed chiefly of white fibrous tis-
sue, with some fibres of the  yellow element. _  The
smaller trabeculse are composed of elongated spindle-
shaped cells, about  the 800th of an inch in length,    ^ ^ ^ ^
and about the = nSrTjth °*  an ltlC" Dr0a{1 ln  ttie Cen"   Secular tissue of spleen
tre, which is  their  widest part.   They contain  a   J^mSE* SS
distinct elongated or oval nucleus.  The nucleus is   diameters.
often found bulging upon one side of  the fibre cell,
and in some instances appears  only connected with it by a stalk.
The  cell is often much curved,  and sometimes bent upon itselt, an
 appearance arising  from  its mode of development, which takes place
 according to the observations of Mr. H. Gray, by  the  solution  of
 the cell wall at a point  opposite  the nucleus, which latter remains,
 and the  cell wall itself  forms the fibres which are prolonged from
 either side of  it.                                           .
   In  several of the mammalia, both in the capsule and also  in the
 trabeculse, a number of  muscular fibre cells,  with  a distinctly oval
 elongated nucleus, are present.  The fibre may be entirely composed
 of these cells.   They are not present in the human spleen, but may
 be readily demonstrated  in that of the sheep.  The spleen possesses
 very slight power of contractility, and in experiments upon the spleen
 of the ox and  sheep, Mr. Gray was unable to obtain marked con-
 tractions by the application of a strong galvanic current.
 
808
SPLEEN PULP.
  Spleen Pulp.—The spleen pulp, or parenchyma, the proper tissue
of the spleen,  is composed of peculiar colourless cells, containing
                                  masses of colouring  matter, free
             Fig. 246.               coloured  particles, granular mat-
                                  ter and blood corpuscles.
                                    The colourless portion of the
                                  spleen pulp is  composed princi-
                                  pally  of  small circular  cells, or
                                  nuclei, about the  size of a blood
                                  corpuscle, and having  a faintly
                                  granular appearance. These small
                                  nuclei vary somewhat in size, and
                                  are interspersed with a  consider-
                                  able quantity of granular matter,
                                  which  is  often collected  around
                                  them.  The spleen pulp also con-
                                  tains  a  few nucleated  vesicles,
                                  nearly T^0^th of an inch in dia-
                                  meter.
                                    These  colourless elements con-
                                  stitute a  considerable proportion
                                  of the spleen pulp, and are in con-
                                  tact with the capillary walls, and
                                  with the  Malpighian  corpuscles
                                  of the spleen.   Great variation
                                  occurs in  the size  and  general
character of the  cells and nuclei which compose  the colourless ele-
ments, and they vary much  in  quantity in different  physiological
conditions of the system.  Mr.  Gray has* shown, that in well-fed
animals they are much more  abundant  than in those supplied with
an insufficient quantity of food,  and their proportion increases after
the completion of the digestive process.
   They are composed of a proteine compound, and in their chemical
characters closely resemble the white corpuscles of the blood.
   The red colour of the spleen pulp is due to the presence of a great
number of blood globules and coloured corpuscles, free or contained
within cells.
   The blood globules are frequently observed to  be smaller than in
other situations; their outline is  often indistinct;  sometimes their
surface appears  corrugated or  shrunken, and their walls in some
places collapsed; their outline is irregular and angular, and in many
instances  corpuscles are seen evidently breaking up into small irregu-
lar masses of red colouring matter.  These appearances indicate that
the red blood corpuscles are undergoing a process of disintegration,
but this change also appears to be effected in another and very pecu-
liar manner, which was first  described by Kolliker.   Several blood
corpuscles (from one to nine or ten)  collected together,  appear to
become covered with an investing membrane, adhering to the interior
wall of which,  a distinct nucleus may be observed.   Such appears to
be the manner  in  which  these blood corpuscle-holding  cells  are
 Muscular fibre cells from the spleen of the sheep,
magnified 400 diameters,  a, a. Fibres more highly
magnified.  After Mr. Gray. 
COLOURLESS CONSTITUENTS.
809
formed, but whether  the  nucleus precedes the formation of the cell
or succeeds it, is not known.   The blood globules within now undergo
disintegration in the manner just referred to, and at length the cell
contains only coloured granules, varying in size and  form.   These
granules gradually become of a golden yellow colour, and then paler,
until at last the contents  of  the  cell become almost decolourized.

                             Fig. 247.
 Pulp of the human spleen, a, a. Blood corpuscles. 6, b. Dotted nuclei,  c, c. Nucleated vesicles.
d, d. Coloured corpuscles of hamatine.  From Gray on the Spleen.

   Occasionally, red crystals are seen in the blood corpuscles of the
splenic  parenchyma, as was first observed by Funke; and not un-
frequently numerous free coloured acicular crystals are met with.
   These appear to be the most important  changes which take  place
in  the disintegration of the red blood corpuscles  in the spleen  pulp.
In  some animals, the disintegration  seems to occur entirely within
the large cells; while in others, the blood corpuscle-holding cells are
very rarely met with, and the blood globules  become broken  down
into coloured granules without  being at any time enclosed in a cell.
In other cases, again, both  processes occur.   In the course of very
numerous observations upon  the human subject,  Mr. Gray only ob-
served blood  corpuscles  enclosed in cells in two instances, and then
in  very small number.
   We  may observe here, that  Gerlach interprets  these  facts in a
totally different manner, and considers that the changes taking  place
in  the blood corpuscle-holding cells occur in the  reverse  order  to
that which we have  described.  In fact, he considers that the  blood 
810
SPLEEN.
corpuscles preformed in these cells, commencing as irregular yellow
granules,  and gradually becoming developed  into the  perfect  red
blood globule.   In this view Virchow  appears  to  coincide.   Dr.
Hughes Bennett, of Edinburgh,  also considers the spleen as a blood-
forming organ.
  The changes above referred to take place in the spleen pulp which
lies between the trabeculse, and,  of course, external to the capillary
vessels.  Now, we  have to inquire how the blood corpuscles leave
the vessels and enter the pulp.
  Mr. Gray has shown  that many of the capillary vessels  are  not
directly continuous with the  veins, but that the blood, in  passing
from one set of vessels to the other, traverses intercellular spaces in
the spleen pulp.  The  veins  also, in  many cases, appear to com-
mence in  intercellular spaces, so  that it is not difficult  to conceive
how the contents of the vessels extravasate  into, and become mixed
with,  the constituents of the pulp, especially when the organ is  dis-
tended with blood.   These  changes appear  also  to take place  to a
more limited extent within the veins themselves.   Although this may
be the correct explanation  of the manner in which the cells in the
pulp communicate with the blood in the vessels, we cannot look upon
it by any means as demonstrative.
  Splenic Artery.—The splenic artery is the largest branch of  the
cceliac axis, and the size of this vessel in proportion to the organ to

                             Fig. 248.
which  it  is distributed, is  considerably larger than  that  of other
glands, with the exception of the thyroid.  The large  size of the
vessel would lead  to the inference that more arterial blood is dis-
tributed to the spleen than is required for the mere purposes of nutri-
tion.   The branches of the artery are  invested with sheaths derived
from and continuous with the fibrous capsule of the organ, and  they 
MALPIGHIAN CORPUSCLES.
811
have a similar  structure to it.   Each arterial branch is distributed
to a particular part of the organ, and it does not anastomose with
contiguous branches.  The smaller arteries, about the 5fo of an inch
in diameter, are connected with  the  Malpighian  bodies, which  are
usually placed in the points of bifurcation of the vessel.
   Malpighian Corpuscles.—-Upon making a section  of a fresh  ox s
spleen, a number  of small round whitish bodies will be seen.   They
are sometimes collected in groups of four or six together, and appear
to be connected with the  smaller arteries, which are  in close prox-
imity  to them.   These small bodies have been named Malpighian
corpuscles from their discoverer; they are in close contact with the
spleen pulp, except at the points where they  are in connection  with
the coats of the artery.
   The Malpighian corpuscles are very distinct in pigs, sheep, oxen,
 and guinea pigs.   In most  other mammalia  they are to be demon-
 strated, although  with greater difficulty.  In the human subject they
 are constantly present; but often are not to be distinguished in  con-
 sequence of rapidly undergoing post-mortem change.   In birds, these
 bodies are very numerous,  and  have been observed, by Muller, in
 the chelonia, among  reptiles, but they cannot  be seen in the naked
 amphibia.   In fishes, they appear to be absent.
 This figure shows the connection of a splenic corpuscle with the neighbouring^vesselsJ^cco^ng Jo




vessels communicate with the veins, are shown in this figure. 
812
SPLEEN.
   The  splenic corpuscles  are placed upon a small branch  of the
arteries as upon a short peduncle or stalk, which sometimes consists
only of fibrous tissue, prolonged  from the sheath of the vessels, or
they lie in the angle formed by the divergence of two branches from
each other.  The artery divides  into  numerous  branches upon the
surface of the Malpighian corpuscles.  The observations of Kolliker
and Dr. Sanders, which have lately been confirmed by Prof. Huxley,
have shown that the substance of the corpuscle itself is traversed by
small capillary bloodvessels.   These small vessels probably pour their
blood  into  small veins which surround  the corpuscle, and are of
considerable size.  According to Mr.  Gray, these veins receive the
secretion of the Malpighian bodies.
   The Malpighian corpuscle  does not  appear to us to be invested
with a distinct and well-defined  membranous capsule; but we are
inclined to agree with Remak and Leydig, who represent their con-
tents as not  being separated by any distinct line  of demarcation
from the  splenic pulp, although the fibrous  tissue derived from the
external wall  of  the vessels  appears  to form a sort  of imperfect
capsule.   The cells of  which these bodies are composed readily pass
from them into the pulp.  Mr. Gray has made the interesting  obser-
vation, that these bodies are very large, and  well defined  in well-fed
animals, and that, during the latter part of the digestive process,
they increase  in  size, while,  in  animals insufficiently fed, they are
very small, or absent  altogether.  In the  latter, little increase is
noticed in their size after digestion.  Their  increase is  considerable
under  the  influence of an albuminous diet; but when  animals are
confined to fat or gelatine, these bodies are not to be distinguished.
   Veins of the Spleen.—The splenic vein is the largest branch of
the vena  porta, and, like  the others, is destitute of valves.  The
branches into which the vein divides, do  not communicate with each
other  in the  substance of the  organ.  Mr. Gray describes three
different modes in which the veins commence :  1. As continuations
of the  capillaries  of the arteries, which is the most common method:
2. By intercellular spaces in the substance of the spleen pulp through
which  the  veins communicate with  each other.   The smallest veins
commence  in  this manner;  or 3. By forming an imperfect capsule
to each Malpighian body.  This latter mode of commencement has
not been described by other observers, and Mr. Gray considers these
small veins as the channels by which the  secretion of the Malpighian
bodies  is carried into the circulation.
   The vein ramifies abundantly upon the surface of the spleen, and,
as it enters into the organ, receives an investment of fibrous tissue,
which is prolonged upon the branches,  forming their sheaths,  which
are connected with the trabeculse.
   Lymphatics.—But little is  known of the ultimate arrangement of
the lymphatics of the spleen,  or of the manner in which they com-
mence.  They are certainly not connected with the Malpighian cor-
puscles, nor can we look upon them as the channels which carry off
the secretion of the organ, a view which has been advocated by many
observers. 
USES OF THE SPLEEN.
813
  Nerves.—The nerves of the spleen are derived from the splenic
plexus formed  by branches from the left semilunar ganglion,  and
from the right pneumogastric  nerve.   The branches are distributed
to the coats  of the arteries; they may be traced upon them for a
considerable distance, but gradually they become lost.
  Changes in the Blood in the Spleen.—The most important  pecu-
liarities  in splenic  blood  appear to  be the  following:   The  total
quantity of solid matter  is  considerably less  in  the blood of the
splenic vein  than  in  arterial or venous  blood, and the blood cor-
puscles are reduced to half the quantity.  The greatest reduction
seems to occur at the period of the greatest turgescence of the spleen.
Mr. Gray has made the very interesting observation, that in starved
animals  no change is observable.  The albumen is increased, par-
ticularly when the amount of blood corpuscles is much diminished.
The quantity of fibrine in splenic blood, is also found to be increased.
The serum is often observed of a pale reddish-brown colour.
   Uses of the  Spleen.—We have  now to consider the  uses of the
spleen in the animal economy.  From the large  quantity of elastic
tissue in its capsule and  trabeculse, it  seems  eminently adapted to
undergo great  changes in volume ; and  the  direct experiments of
Dobson, and  many other observers, have proved  that it  becomes
much enlarged during digestion, as well as when  blood was injected
into the jugular vein.   Connected with the large veins of the portal
system, it forms a dilatable diverticulum, or reservoir, in which  blood
may, for a certain time, be contained, thus  preventing dangerous
 congestion of the veins of the liver,  and some other abdominal viscera,
 and, indeed, of the venous system generally.   The spleen does not
 appear to be contractile.   In several careful experiments, Mr. Gray
 was never able to cause more than a slight corrugation of the surface
 of the organ  by the  galvanic current,  although  active contractions
 could be  produced in the oesophagus, or stomach, under similar
 circumstances.   In no  instance  out of  twenty  experiments,  was
 blood expelled from  the organ, or  its  diameter diminished.   Not
 only does the spleen  perform  this physical office, but, as  has been
 shown, certain important chemical and microscopical  changes are
 found to have occurred in the  blood which has passed through this
 organ.  In 1847, Kolliker advanced the theory that blood corpuscles
 became disintegrated  in the spleen, an opinion which was afterwards
 supported by Ecker and Be'clard.  From various facts which we have
 alluded to, we cannot but look upon  this point as decided in the
 affirmative, although  others have  been led to adopt the view, that
 blood corpuscles are actually formed, instead  of  being disintegrated
 in this organ.  Kolliker  thought  that  the  colouring matter of the
 blood was changed in the spleen, and converted  into  the peculiar
 colouring matter of the bile;  but Mr. Gray has shown, that yellowish-
 green bile is found in the gall-bladder  of the  chick, at a period con-
 siderably antecedent  to  the  development of the splenic vein.   ±ne
 small size  of the  spleen in the foetus, as compared with its increase
 after birth, and in adult life,  renders  it improbable that in  intra- 
814
SUPRA-RENAL CAPSULES.
uterine  life it  acts the part either of a blood-forming, or blood-de-
stroying, organ.
  Its great increase in size, in well-fed animals, and its diminution
in insufficiently-fed  animals, and, especially its increase  after the
completion of digestion, render it extremely probable that  it has the
power of storing  up albuminous material  for future consumption,
when a larger quantity of nutrient material is taken than is required
for the immediate wants of the system.  The cells of the Malpighian
corpuscles  appear, from Mr. Gray's observations, to be the organs
especially concerned in  this process.
  Supra-renal Capsules.—The  supra-renal capsules are two bodies
of a  somewhat  triangular form, situated one  on each  side of the
spine, a little above the corresponding kidney, to the capsule of which
each is connected by loose cellular tissue.
  Each  supra-renal capsule is about an inch  and a half  in depth,
somewhat less in width, and usually about half an inch in thickness.
The  weight varies  from one to two drachms.  The gland is inclosed
in a  thin fibrous capsule, which dips  down into its substance.  It is
surrounded with loose areolar tissue, containing an abundant quantity
of fat.
  Upon  making a section  through the body,  it is found to be  com-
posed of two distinct portions, a cortical and a medullary part.  The
former is of a yellowish colour, shading into a brown border towards
the interior.   It tears somewhat readily, and then exhibits a fibrous
appearance.   The  medullary  substance is of  a paler  colour, unless
the vessels are injected  with blood, and of a somewhat softer consist-
ence.  If  the gland be not perfectly fresh, a cavity is usually seen
in the interior, which results from the breaking  down of the medul-
lary tissue.
  The cortex is divided into  a  series of compartments or tubes by
septa of fibrous tissue  prolonged inwards from  the capsule of the
organ.   These spaces extend through the entire  thickness of this
part of the body, and pass from the surface vertically inwards.  They
contain numerous oval or  spherical  bodies, varying considerably in
length.  These  have been looked upon by Ecker as gland-follicles,
but Kolliker considers them merely as  aggregations of cells not in-
vested with a distinct membrane, or inclosed in a larger cell.   They
are separated from each other by meshes of areolar  tissue, the  fibres
of which often appear to be connected with the surface of  the  mass.
In the outer part of the  cortex separate cells, filled with pigment
granules, are usually to be met with ; but in the inner portion, round
or oval vesicles are found, which are  filled with  oil globules.
  The medullary  substance  is  composed of  a network of areolar
tissue which is prolonged from  the  cortex, and  contains  numerous
vessels, in  the meshes of which are found many cells, some of  which
contain fat or granular pigmentary matter.  A distinct nucleus and
commonly  a nucleolus are seen, and often the  cells have many  angu-
lar processes, or are much branched ; indeed, these cells present  an
appearance much resembling that of  the nerve vesicle.
  Besides  the fibrous, vascular, and  cellular elements just  described, 
THYROID.
815
the medullary portion of  the supra-renal bodies is very largely sup-
plied with nerve fibres derived from the semilunar ganglia and solar
plexus, with  a few fibres  also from the pneumogastric, and from the
phrenic.   The nerves appear  to  perforate the cortical substance in
several  places, pass through this, and  enter  the  medullary, where
they form a plexus amongst the fibrous tissue.  The mode of their
termination has not been made out.
  The function of these peculiar bodies is entirely unknown.  From
the great dissimilarity of  structure observed in  the cortical and
medullary portions of the organs, it  is probable that each performs
a distinct and separate office.  In the present state of our knowledge
we may continue to  classify the former with the ductless or vascular
glands, but, from the existence of cells much  resembling nerve vesi-
cles, and an abundant plexus of nerve fibres, it appears more correct
to regard the  latter as connected in some  manner with the nervous
system and probably with the sympathetic.   Bergman thinks that
this part of the supra-renal body may, perhaps, bear a relation to the
sympathetic,  similar to  that  which the pituitary body does  to the
brain.   It is interesting to note, in connection with this subject, that
our friend, Mr. Brown-Sequard, has observed  congestion, and hyper-
trophy of the supra-renal capsules, after injuries to the chord in the
dorsal region.
  Dr. Addison has  lately published  an account of several very in-
teresting cases of disease  of the supra-renal capsules, associated with
" anaemic general  languor  and  debility,  remarkable feebleness  of
heart's action, irritability of the stomach, and a peculiar change of
colour in the skin."*
   Thyroid.—The  thyroid body, or gland, as it is  sometimes called,
is  a soft, and very vascular organ, situated upon  the lateral aspect
of the upper part  of the trachea,  as far upwards as the sides of the
larynx.   It consists of two  lateral lobes, united by a thin narrow
portion, which has a similar structure  to that of the gland  itself,
extending across the front of the third or fourth rings of the trachea,
and known  as the isthmus.   The middle lobe, which  varies  some-
what  in  position, is a thin process, extending  upwards from the
isthmus,  or one of the lateral lobes, and  often reaches  as high  as
the hyoid  bone,  to which  it  is  attached  by loose  fibrous tissue ;
indeed, this process itself is not  unfrequently composed of  fibrous
tissue only, and sometimes  contains  a few fibres of the thyro-hyoid
muscle.
  The thyroid body itself  is  made  up of a  vast number of small
lobules, which are aggregated  together in larger globular  or oval
masses, of which  the entire substance of the gland  is  composed.
These  are  all  surrounded by, and connected  together with areolar
tissue, and each subdivision  itself consists of a  number of small
closed vesicles, between which the vessels ramify, also  closely in-

  * On the Constitutional and Local Effects of Disease of the Supra-renal Capsules, by
Thomas Addison, M. D., Senior Physician to Guy's Hospital, 1855. 
816
THYMUS.
vested with areolar tissue, varying considerably in size, and con-
taining fluid, or thick gelatinous matter.
  Each vesicle may, therefore, be described as consisting of a fibrous
coat,  composed of areolar tissue, internal to which there  exists a
delicate basement membrane, lined by cells of epithelium, which vary
somewhat in character, but usually are seen as polygonal, or almost
circular cells of a faintly granular appearance, and having a  nucleus,
which, however, is by no means invariably  present.   In most  in-
stances, the vesicle can be seen to be lined with a single layer of this
epithelium,  and many  free cells are  usually found floating in the
fluid contained in the cavity.
  The fluid in the vesicles  is coagulated by heat and nitric acid, and
evidently contains a large quantity of albumen.
  The stroma of the gland consists of fibres of  both the white and
yellow element, and it supports the  bloodvessels, which  are ex-
ceedingly numerous, and form a capillary plexus round each vesicle.
  The lymphatics in the thyroid are numerous, but of their  ultimate
distribution nothing is known.
  The following are analyses of the thyroid body, by Dr. Beale.*
	Human.	Ox.
	70-60	71-34
1 matter ......	29-40	28-66
Fibrinous and albuminous matter, vessels, and		
fat.......	26-384	24-628
Extractive matter .....	1-70	—
Extractive matter, with gelatine .	—	2-888
Alkaline salts .......	•50	•642
Earthy salts ......	•816	•502
   Uses of the Thyroid.—Of the  uses  of the  thyroid but little  is
known.  The material found in the  vesicles is  of an  albuminous
nature.  Mr. Simon has advanced  the opinion that the thyroid acts
as a diverticulum to the cerebral circulation, and that its nutrition
bears a certain relation to that of  the nervous  matter  of the brain.
When the latter is quiescent, the thyroid is supposed to be active  in
removing  from the blood, and storing up in its cells, certain con-
stituents which are required by the  brain only in its active state, and
which are diverted to it when it resumes  its activity.   This view is
based upon the important fact, that the  arteries of  the thyroid body
arise in close proximity to those which supply the brain, the superior
thyroids coming off from the external carotid, just immediately above
the point of bifurcation of the common  carotid,  and the inferior
thyroid arteries, from the subclavian, almost immediately  opposite
the origin of the vertebrals.
   Thymus.—The thymus body  or  gland is an  organ only distinctly
recognizable  during early life.   It appears to reach its  largest size
between the first and  third years;  but much  variation  occurs in this
point in different individuals.  It lies partly in the thorax and partly
in the neck, and is composed of two lobes, which vary considerably
in size, sometimes the right and sometimes the left being  the largest.

 * Dr. Handfield Jones, article "Thyroid," Cyclopaedia of Anatomy and Physiology. 
mr. simon's researches.
817
Fig. 250.
  The organ rests upon the front of the aortic arch and large arte-
ries  rising  from it,  and also on the left vena  innominata.  It is
covered by the sternum, and  at  birth reaches down  to the fourth
costal  cartilage.  It extends upwards into  the neck, as high as the
thyroid body, and lies upon the front and side of the trachea.
  The researches of Sir Astley  Cooper, and  more recently those of
Mr.  Simon, show that this  organ  consists essentially of an elongated
tube, from all sides of which extend numerous small  follicles or sac-
culi, which pour their contents into the central cavity.   Sir Astley
Cooper unravelled the gland,  and, by having previously injected the
central cavity and follicles  with alcohol, or coloured size, was enabled
to make  out  their  relations and arrangement;  although, by these
processes, it is probable that he distended  the central cavity to a
greater extent than natural,  and was  thus  led  to  look upon it as
much  more extensive than it was  subsequently proved to be by the
conclusive observations of our friend Mr. Simon, which are published
in his  well-known essay.
   The latter excellent observer,  carefully watched the  development
of this gland,  and thus was the first  to make  out accurately its
anatomy.                                                      .
   It is probable that it first arises  from a row of  cells arranged in
linear series,  which coalesce,  and thus become converted  into a  nar-
row tube.  The wall   of  this
tube then bulges at intervals,
 and vesicular cavities are gradu-
 ally formed.    These vesicular
 dilatations are much more abun-
 dant in some situations than in
 others; and the primary offset
 divides  in a   dichotomous or
 quaternary manner, until, from
 the number and irregular dis-
 tribution  of  these  vessels, the
 gland assumes its ultimate shape
 and   character.   The  closed
 cavity of  the gland  contains
 granular  matter, with numer-
 ous nuclei  dispersed through
 it.  In a thin  section, the out-
 line  of  the  cavities   can be
 readily seen;  they vary  from
 the l-50th to  the l-18th of an
 inch  in  diameter, and contain
 numerous granular and nearly
 spherical nuclei, which are, for
 the most part, about l-4000th of  an inch in diameter,  but vary con-
 siderably in  size.   Dr. Handfield Jones observes  that  before  any
 appearance of atrophy has  taken place,  these  elements  are alone
 found, and there is an entire absence of  oil particles, and granular
 material.  The nuclei seem to  fill the ultimate vesicles completely.
 a. Primordial cells in a row.  5.  Isolated cell,
unconnected with the row, and undergoing develop-
ment in  its original cell shape, c. Primary tube,
formed by the fusion of the cells, d. Second stage of
development of the thymus, showing bulgings of tube
in different stages,  which ultimately become them-
selves divided.  After Simon. 
818
THYMUS.
   Uses of the Thymus.—Mr. Simon  regards the secretion of  the
thymus as allied to proteine, and of a nutritious nature.
  In the human foetus, the thymus cannot be detected  before the
                            ninth week, and  its functional activity
                            is greatest in the early  period of life,
                            before the muscular  system is in a very
                            active state;  for when the muscles  be-
                            come more fully active, the  thymus ap-
                            pears not to be required.   It  seems con-
                            nected  with  the  preparation of matter
                            for the pulmonary organs in the  " age
                            of early growth."   Arguing  from these
                            and many other facts, Mr. Simon looks
                            upon the  thymus as acting  " as a sink-
                            ing  fund in  the service of respiration."
                            From the  twentieth  to the twenty-fifth
                            year it diminishes rapidly in size, until
                            no  trace of  it can  be detected in  the
                            areolar tissue of the mediastinum.   In
                            hibernating  animals,  previous  to  the
                            commencement of the winter  sleep, the
                            thymus becomes  gorged with fat,  which
                            is slowly consumed during the period of
                            hibernation.  It has been remarked, that
the use of the thymus at the different periods of active growth  and
hibernation is distinct.   In  the latter  case,  it  doubtless supplies
hydro-carbonaceous matter  for respiration ; but its office,  during the
former period, appears rather to be that  of elaborating fibrine from
albumen and  other substances by the  action of its numerous nuclei.
As the absorbent and other glands  connected with the vascular  sys-
tem become developed, there  seems no longer any need  of a special
organ for this purpose, and consequently the thymus soon disappears.
Professor  Paget  and  Dr.  Handfield  Jones  express  themselves in
favour of this latter view.  In the  present state of our knowledge,
perhaps no better  hypothesis of the office of this  gland can be sug-
gested.   The whole subject of  the  physiology of  the vascular duct-
less glands (if glands they be) is involved in deep obscurity,  and it
is impossible  to form a theory of their respective functions which is
perfectly satisfactory.  Not less obscure are their morbid conditions,
upon which the improved anatomy of the last few years  has thrown
but little light.

  The student is referred to the following works for a more detailed statement of the
various views now held upon the anatomy and physiology of the vascular glands.
  Spleen.—Kolliker's " Mikroscopische Anatomie," and the Article "Spleen," in the
Cyclopaedia of Anatomy and Physiology; Ecker's Art.  " Milz," in Wagner's Hand-
worterbuch; Sanders "On the Structure of the Spleen," in the Annals of Anatomy
and Physiology; Bennett "On Leucocythemia:"  Mr. Gray's Astley Cooper's  Prize
Essay upon the " Structure and Use of the Spleen," 1854 ; Mr. Simon's Astley Cooper's
Prize Essay on tbe "Thymus Gland," 1845 ; also his paper upon the " Thyroid," Phil.
Trans., 1844;  Dr.  Handfield Jones' Articles  "Thymus" and  "Thyroid," in the
Cyclopaedia of Anatomy aud Physiology.
Fig. 251.
 a. Binary and quaternary division
of  simple follicles.  6. Unusual ap-
pearance, in which the follicles must
have increased considerably in length
before undergoing division.  From the
foetal lamb.
 c. Mature structure of thymus, show-
ing the arrangement  of the vesicles
belonging  to one cone.  d.  Tube of
gland.  After Simon.  Reduced. 
GENERATION.
819
                     CHAPTER   XXXVI.

ON  GENERATION. — FISSIPAROUS  MULTIPLICATION. — GEMMIPAROUS
  MULTIPLICATION.--TRUE  GENERATION.—METAMORPHOSIS.—META-
  GENESIS,  OR  ALTERNATION  OF  GENERATIONS.—SEXUAL ORGANS.
  — INVERTEBRATA.--INFUSORIA.—POLYPS.— ACALEPH^.—ECHINO-
  DERMATA. — ENTOZOA. — ANNELIDA. — MOLLUSCA. — CRUSTACEA.—
  INSECTA.--PISCES.--REPTILIA.—AVES.—MAMMALIA.

  Amongst the lower classes of organized beings, both in the animal
and vegetable kingdom,  the multiplication of individuals, or the pro-
pagation of the species, is provided for by three different processes,
while in the highest forms of animal life the process of generation  is
restricted to one of these types.
  The simplest  manner in which  the  multiplication  of individuals
takes place, consists  in the  division of  the being into two, each  of
these again dividing into two others, and so on ; this is multiplication
by  fission.
   The  second mode of increase consists in the formation of a bud  at
some part of the body of the parent: this bud is gradually developed,
drops off, becomes independent of its parent, and ultimately assumes
a perfect  form, resembling in all particulars that from which  it
sprung.
   The  third mode differs materially from the two former, in the fact,
that the new organism results from a series of  changes occurring  in
an  impregnated ovum, which is produced by the mutual action of the
contents  of two dissimilar cells,  the  products of distinct parental
 organs. The new body differs essentially from either of the two cells
which produced it.  This is true generation.
   Fissiparous Multiplication.—In the lowest plants, such  as the
lichens and fungi, this mode of multiplication very commonly occurs.
 The cell, or cells, of which the plant consists,  divide and subdivide ;
 and, in this manner, new organisms are produced.   The same  mode
 of  reproduction is also  seen to be very common amongst  the in-
 fusoria, and may be watched in the common vorticella.
Vorticella Micrott^ma multiplying by spontaneous longitudinal division, from Ehrenberg. 
820
GENERATION.
  The joints of the common tape-worm multiply in this manner, and
after  a time, when perfectly developed,  become  free and separate
from the trunk of the worm.   Amongst the worms (Annelida) repro-
duction takes place partly in this  manner.   In the Nais, three  or
four young worms, resulting  from the division of the parent, may
often be seen still connected with its body.   As these become de-
veloped, they are disconnected from the parent, and, in their turn,
give rise to others by a similar process.

                             Fig.  253.
 Na'is proboscidea, multiplying by spontaneous transverse division, showing the body of the parent
worm and three young ones in different stages of development,  a. Point at which new segments are
being formed. After Miiller.

  In the above instances, multiplication by division occurs as a na-
tural process; but there are many instances in which  the parts re-
sulting from artificial division ultimately become  developed into  a
perfect animal.  Thus a planaria, or a  polyp, may be divided into
many segments;  and each  portion  has  the power of absorbing to
itself nutriment, and of  becoming  developed  into a  perfect  form.
The slightest  handling, again, causes some animals to  break up in
pieces, and each separate part  becomes a new being.
  Multiplication by Gemmation.—A bud consists of a mass of cells,
which possess the power of development, under  favourable circum-
stances, into a form  identical  with  that  from  which they were pro-
duced. In consequence  of this  property, the bud  of a plant has been
termed a phyton;  and a tree must, therefore, be  looked  upon  as an
assemblage of these phytons.  We must, however, bear in mind, that
all  buds have  not this power, as,  for instance, flower buds do not
give rise to the formation of  new  buds  of any sort, but produce
seeds.
  Amongst the lower animals,  reproduction by buds is very common,
and can be readily examined in the  vorticellse and  polyps.
  In the hydra, the first  change which  is observed consists  in  the
formation of a little elevation which soon becomes  globular;  next a
cavity is  formed in this  globular mass,  and becomes continuous with
that of the parent.  After  a time  the channel of communication
closes, and the bud begins  to assume the form of a  polyp,  which
ultimately drops off; and in this way a new creature is formed.   The 
METAMORPHOSIS.
821
 Figures of the fresh-water hydra and
vorticella, showing the multiplication
of new individuals by the formation of
buds.
echinococci multiply by the formation of            FiS- 254-
buds upon the internal surface of the
hydatid  vesicle.   At  first they are at-
tached by a sort of stem ; but ultimately
they become free, and move  about  in
the fluid of the  parent cyst by aid of
their hooks and suckers.
  A bud differs  from  an  ovum in the
important particular, that it contains
within itself the power of  development,
while the latter is incapable of becom-
ing developed  into the form of its pa-
rent until it has been subjected to the
action of the contents  of  another  cell.
The only resemblance between a bud
and an ovum is, that in both the organization is imperfect.
   True  Generation.—The processes of multiplication above referred
to must be distinguished from the one which we are now  about to
consider. True generation consists in the union of the contents of two
different cells,  called respectively the "sperm cell" and "germ cell,"
and the production of a structure differing from both, from which the
new being is ultimately evolved.  The simplest form of this process
is seen in the lower algae in conjugation.  At first, the opposite cells
of  two filaments are  seen to be swollen on the side turned towards
each other; the swelling increases until a sort of process is formed
from  each: these at length meet; the walls  become fused,  the cavi-
ties continuous, and the contents of the two cells
become mixed.   From this admixture a new body,
termed a spore or sporangium, results, by the  de-
velopment of which the new plant  is formed.
  In  the higher  plants and  in animals, distinct
organs are set apart for the formation of the sperm
cells  and germ cells.   By the action  of  the con-
tents of  the sperm cell the ovum becomes impreg-
nated ; and under favourable circumstances, often
quite independent of the parent, changes  result
which  give rise to the formation  of the embryo
from  which the  adult animal is gradually deve-
loped.
  Now,  either  the perfect form of the being may
be attained by  the gradual and progressive deve-
lopment  of the embryo, or several distinct phases
of  existence may be  passed  through before  the
creature  reaches  its  perfectly developed  form.
This latter condition is seen in many of the lower
classes of animals, and is familiar  to us in  the
class of insects; it is,  in fact, what we understand
by  metamorphosis.
                   -In metamorphosis, it  must be
Fig. 255.
  Metamorphosis.-
carefully borne  in
       53
mind, that it is  the  self-same
 Conferva bipunctata in
the act of conjugation,
after Meyen.  The cells
from  contiguous fila-
ments  approach each
other,  and  ultimately
their cavities coalesce.
The oval spores result-
ing from the action  of
the contents of one cell
upon the other are seen
in two of the colls. 
822
GENERATION.
embryo which passes through  certain transitional stages or phases,
and  ultimately becomes the perfectly developed animal; a condition
essentially different from that which we shall next  consider under
the term  Metagenesis, or  alternation of generations, in which suc-
cessive  generations of larval creatures are produced from  larva;
without the occurrence of any fresh generative act.   Here, instead
of one individual passing through several  transitional  forms, an im-
perfectly developed creature produces  a multitude of  forms, resem-
bling either  itself or the  perfect  individuals from which the ovum
was  formed which evolved  it.
   Metagenesis.—In  some  animals,  the embryo, instead  of being
developed into a form  resembling that of its parents,  only attains a
sort  of larval condition, the offspring of which, however, return to
the  perfect type, instead of assuming the character of their  larval
patient.   Now, between  the fully-developed  animals of one genera-
tion  and those of the next succeeding there may be several  series of
these imperfect or larval forms ; each larva  producing without  any
generative act, and, indeed, without itself possessing true generative
organs, many similar  larval forms, until at last  these larvse, instead
of producing larvae, give rise to perfect forms, which propagate only
by the production of  ova.
   This curious phenomenon occurs amongst many classes of animals ;
and  the subject  of late years has engaged  the attention of many
naturalists.  Steenstrup has described  the process under  the term
alternation of generations.  Owen terms  it metagenesis and parthe-
nogenesis.   The  facts have been  explained  differently by  different
observers; the two  most  important  theories being the  following:
according  to the first, the subsequent broods result  by a process
resembling budding, taking place within  the bodies of their prede-
cessors ; while the second supposes that  a portion of the original
germ-mass is  actually transmitted  from  the parent  through the
whole series  of beings existing  between two generative acts.   The
latter view has been most  ably advocated  by Professor Owen, in his
lectures on Parthenogenesis; and the former is supported by Dr.
Carpenter.   In the Campanularia dichotoma,  one of the tribe  of
polyps, at  certain periods, buds are developed from  the stem, which
do not become converted  into polyps,  but, after having reached  a
certain stage of development,  drop off,  and in their mature  state are
seen as transparent disc-like bodies, having the power of swimming
about in the water.   These  creatures have long  been  known  as
Medusae, or jelly-fishes.   It must be remarked, that  no  generative
organs are to be found in the  polyp ;  but  these organs are  found  in
the  Medusae, in  which  also ova  are  developed.   The ova become
polyps, which eventually put forth Medusa-buds as before.
   In another polyp, the Strobila, at certain periods, multiplication
by the formation of buds ceases, and the body of the polyp becomes
constricted, and at the same  time much  elongated.  The  constric-
tions, which  may be as many  as forty in  number, gradually become
deeper, until at length the body of the polyp becomes divided into a
number of flattened discs.   The terminal  disc drops off, and appears 
ALTERNATION OF GENERATIONS.
823
as a free swimming Medusa, in which generative  organs  are  found
and ova produced.  The other discs fall off  successively, and in like
manner become Medusae.   These polyps,  therefore, would with pro-
priety be considered as belonging to the class Acalephae, the Medusa
representing the perfect condition of  these animals.
  The livers of various  animals are infested  with an entozoon termed
a fluke.  The development of the fluke of the common fresh-water
snail (Limnaeus stagnalis) presents us with a beautiful example  of the
curious phenomenon we are now considering.   In the first stage of
its  existence it is seen as a creature (Cercaria) swimming about in
the water, and is  provided with a tail.  After a time, these cercariae
fix themselves to  the skin of the snail by means of a circlet of  hooks.
The tail is  cast off, and  the body becomes  covered with mucus, which
hardens, until a transparent case is formed.  This is the pupa state.
Next the creature bores its way into  the  body  of  the  snail, and
reaches the liver; the hooks drop off,  and it possesses all the charac-
ters of a fluke or  distoma.  The fluke develops ova ; the ova become
developed  into worm-like creatures, which inhabit the  snails.   The
worm-like body contains, as it were, a  progeny, each member of which
becomes the parent, of  another generation.   The original larvae are
developed  from a perfectly spherical germ, consisting of granules.
So that  the early stages of life of the fluke are passed in the body
of a worm-like creature; the next, in  the water, free,; next, attached
to  the body of a snail;  and lastly, in a  perfectly developed form in
the liver.   Thus  this creature assumes three distinct forms at differ-
ent periods of its existence, which, until these discoveries were made,
had been described as three distinct creatures.
   There are numerous other most striking instances among the ento-
zoa of this extraordinary change of character in the course of deve-
lopment.  It has long been known that the cystic entozoa (as Cysti-
cercus, etc.) are  not provided with  generative organs;  but  it was
reserved for Van Siebold to  show that these entozoa were only the
imperfectly developed forms of  species occupying a higher position ;
and he has been able to prove that the cysticercus fasciolaris, which
is found in the liver of  the rat and mouse, becomes developed in the
intestine of the cat into the tcenia crassicollis, the common tape-worm
of that  animal.   Kuchenmeister and Van Beneden have  been able
to  demonstrate the occurrence of similar changes  in many other
entozoa.
   Another beautiful example of metagenesis occurs among the mem-
bers of  a much higher  class of animals—insects.  The ovum of the
perfect winged aphides, or plant lice, becomes developed into  an im-
perfect wingless, or larval creature, in which no  sexual organs have
been discovered.   These viviparous, but non-sexual  larval forms are
 capable of producing  non-sexual descendants  exactly  resembling
 them, without the occurrence of any  generative act, and this process
 is  repeated for nine  or ten generations.  The last autumnal brood,
 however,  of  these larvae produce, in the same  viviparous manner,
 perfect  male and perfect female  insects, with fully developed  sexual
 organs.  The female deposits her ova in the  axils of the leaves and 
824
GENERATION.
other protected parts of the  plant, where they remain until the fol-
lowing spring, when they are hatched, and the larvae above described
issue forth; the first larva producing eight, and each of these repeat-
ing the process, until, in the course of the summer, millions of larval
forms are produced.  This must conclude our very imperfect sketch
of these  interesting processes;  and, for more detailed  information,
we must refer the reader to the works enumerated at the end of the
present chapter.
  Professor Owen considers  that  the larval forms  result from the
development of a portion of the original germ-substance of the yolk,
which was not converted into a portion of the textures of the beings
which resulted from the immediate development  of the  ovum ; and
hence he has applied the term parthenogenesis, or virgin generation,
to this process of development.  Dr. Carpenter,  on  the other hand,
looks upon the process as akin to gemmation, or budding, rather than
one  of actual generation.  Victor Carus  shows that in this process
of development the embryo is formed from a granular germ, whereas
ordinarily it  results from the process of cell-multiplication, as will
be shown in the chapter on  the development of  the embryo.   The
same author contrasts the  process of metamorphosis and metagene-
sis in the following words: "Larvae, the subjects of metamorphosis,
arrive at the state of perfection by throwing  off provisional structures
which belong to their larval condition ;  but nurses,* the subjects of
metagenesis,  are themselves entirely provisional structures."
  In the  present  state  of knowledge, it  is  difficult to group these
extraordinary phenomena under one general  head.  Although we
may contrast the processes of metamorphosis and  metagenesis with
each other,  and draw definite  distinctions  between them, we must
remember that there are instances in which  both these processes
occur; and although metamorphosis affects a single individual, and
metagenesis a very numerous progeny, we do not feel  ourselves in a
position to define the exact relation which one bears to the  other, and
we  think it  better to  avoid  any attempt at generalization until a
greater number of facts relating to these wonderful  processes  should
be discovered, rather than  adopt a view which future  research  may
show to be erroneous.
  Sexual Organs.—The generative organs are of two kinds, the male
and the female organs, the one secreting the "sperm cell," and  the
other the  " germ cell."  The generative apparatus consists of two
parts: a formative organ,  in which the elements are produced, and
which  is essential; and an efferent duct, by which the products of
secretion are carried off.
  The male  and female organs may exist in one  individual or in
separate individuals.   The first  condition is termed unisexual, and
the second bisexual generation.
  In some unisexual  or hermaphrodite  animals, self-impregnation

  * The term " nurse" was originally applied by Steenstrup to these larval forms,
but we have purposely avoided its use, as it is for many reasons very objectionable,
and likely to convey a wrong idea of the nature of the viviparous larvae. 
INVERTEBRATA.
825
takes  place, as is the case in the common tape-worm (Taenia solium);
while  in other instances, concourse is necessary in  order that the ova
should^ be exposed to  the action of the spermatic fluid,;  this is the
case with many of the mollusca, as the common snail, etc.   In these
instances, each hermaphrodite animal impregnates its neighbour.
   Besides the secretion of the formative organ,  other secretions are
frequently poured  into the efferent duct.   The duct undergoes great
modifications  in different parts of its  course  in various animals,
according to the particular office it has to fulfil.   We shall now con-
sider some of the most important characters which the sexual organs
exhibit in the  different classes of animals.

                               Invertebrata.

   The Infusoria multiply by fission, and rarely by gemmation.  No sexual organs have
yet been discovered in them, and  ova are not  met with in this  lowest class of the
animal series.
   Fission may occur in the longitudinal direction, as in the Vorticella: or transversely,
as in Stentor and some  others; or in both directions, as in Bursaria, Paramecium, and
others.  The Vorticellse are also propagated by the formation of buds.  When divi-
sion is  about to take place, the cell within the body, known as the nucleus, is seen to
divide into two ; each half containing, therefore, a newly-formed nucleus.
   The Polyps multiply by gemmation and by the formation  of ova, very rarely by
fission.  In gemmation, the young polyp may be ultimately set free, as in the Hydra;
or it may remain attached to the stem or common  body, or polypidon, as in the
majority of the members of this  class.  Some  polyps are hermaphrodite, while in
many the sexes are distinct.  At the time when the common hydra is about to propa-
gate by ova, the male and female organs are both developed as excrescences upon the
outer surface of  the body.  Others, again, are sexless, and give rise to the develop-
ment of medusa-buds, or split up into discs, as already described in p. 822.
   Reproduction in the class Acalephae takes place almost entirely by the formation of
ova.  It has, however, been shown by Professor Huxley, that  some multiply by gem-
mation as well as by the production of ova (Diphyidse).  Some of the species are uni-
sexual, and others bisexual.  The genital organs are only developed at certain periods
and the male and female elements are brought into contact through the influence of the
water in which they swim.
   In the Echinodermata, fission has only been observed to occur  in one class (Holo-
thuria); and the generative function, which is developed in this class to a great extent,
is carried on almost exclusively by the production of ova.   The sexes are distinct, but
the ova are impregnated without sexual intercourse. In some  there is a proper effer-
ent duct; but in others the elements pass into the respiratory  cavity, and thus escape
from the body.
   Among the Entozoa great variety is met with in the arrangement and character of
the generative organs.   Almost all the animals of  this class possess true generative
organs, and multiply by means of  ova, but in many of them fission occurs; as, for
instance, in the tape-worm;  but it is worthy of remark, that the entire animal is not
produced in this process.  The segments,  however, which have been separated con-
tinue to live.   As already mentioned, the Echinococcus multiplies by the formation of
buds.
   Some of the Entozoa are unisexual, and  have the power of self-impregnation, and
some are bisexual.
   The Annelida reproduce by sexual apparatus, and in some instances, as already re-
ferred to, by transverse fission. In the latter case, the different organs, including the
tentacles and  eyes, are developed before the new animal is separated from the old one.
This mode of multiplication, however,  only continues for a certain time ; at  length it
ceases; genital organs, which before could not be distinguished, are developed, and
ova are formed.  The  Hirudines and  Lumbrici are hermaphrodite, but copulation is
necessary for impregnation to take place.
   Amongst the lower Mollusca, the sexes are sometimes united in one individual, and
sometimes  distinct.   There are no copulatory organs, so that the water forms the
medium by which  the spermatic particles  are conveyed to the  ova.  Amongst the
Tunicata, multiplication also takes place by gemmation. 
826
GENERATION.
  Of the higher Mollusca, some are hermaphrodite, and in others the sexes are dis-
tinct.   Many families are characterized by the possession of what has been termed an
hermaphrodite gland, which is almost always imbedded in the substance of the liver.
This gland consists of numerous radiating and branched caeca.   Each caecum consists
of an external and internal sac folded within  the first.   Ova are produced by the ex-
ternal sac, and  spermatic  particles  by the internal  one.  Excretory ducts pass off
from these organs, and terminate in two  tubes; the one corresponding  to  the Fal-
lopian  tube,  the other to the vas deferens.  Besides  this apparatus, there is also
another organ connected with the excretory  duct;  this is the albumen gland, which
furnishes a secretion  in which the ova become  imbedded  as they pass towards  the
external orifice.  This curious arrangement may be well seen in the common snail.
  Into the same cavity or cloaca in which the  genital ducts terminate, is found  the
opening of another very remarkable organ—the  dart sac—in  which a hard and exces-
sively sharp-pointed, and sometimes toothed, calcareous body is formed, which is pro-
jected during copulation.  The dart may be looked upon as an arrangement for pro-
ducing sexual excitement, for each snail has been seen to prick the other just before
coition.
  Amongst the Cephalopoda, the highest of the Mollusca, the sexes are always distinct.
Connected with the  excretory duct of the ovary is  an apparatus which  furnishes a
secretion by which the eggs are bound together, and a firm horny covering formed for
their protection.
  The testicle consists of an oblong organ, situated at the bottom of the cavity of the
mantle.  Connected with the  excretory tube, is  a sac in which  some very complicated
organs, containing the sperm, are developed, from which the contents are  expelled by
a very remarkable projectile apparatus.  Coition appears to  take place simply by one
animal applying itself to the other.  A true intromission of the penis seems hardly
possible.
  One of the most curious phenomena which has been  discovered in  connection with
the generation of some of the members of this class must be briefly noticed here.  On
the male Argonaut is developed a curious elongated body, termed Hectocotylus, which
communicates with the testicle of the Argonaut  by a duct.  Before this body had been
proved to belong to the male  Argonaut, and had only been seen upon the female, it
was looked upon as a parasite, and Cuvier described it as one of the Trematoda. The
Hectocotylus, which is to be regarded as one of  the arms of the animal metamorphosed
in a peculiar way,  at length becomes filled with  spermatic fluid, and drops off.   It is
now independent, and comes into contact with the female Argonaut, which it impreg-
nates.   In this point it resembles, "as also  by its movements, by a kind of circula-
tion, and  by the long duration of its life after detachment, a  true male animal"
(H. Muller).
  Among different families of the Crustacea, the arrangement of the generative organs
varies much.   In  most, the  sexes are distinct; but one c^ass, Cirrhipoda, is herma-
phi-odite.   Some Crustacea, again, are almost exclusively females; and these for many
generations produce females, and at very  long  intervals only, males.  Some females,
again, lay two kinds of eggs, one of which becomes developed spontaneously, while
the  other  requires  to  be  fecundated  by  the spermatic fluid.  The female of  the
Daphnia, towards  the close  of  the year, produces  two eggs, which must be looked
upon in the light of gemmae,  or buds,  as they contain no germinal vesicle.   These are
the so-called hibernating eggs, and are developed without the fecundating influence
of the sperm.
   Among the Crustacea, the  genital organs  are usually double, and  symmetrical in
both sexes.   Connected with the efferent duct of the female organs are some glands,
which secrete a viscid substance, by which the  eggs are glued together in clusters te
the posterior abdominal  feet, as  occurs,  for the most part, among the  Decapoda
 (lobster, etc.); but in those species in which these organs  are deficient, there  is
formed a marsupium, or sort of pouch, connected with the lower surface of the thorax,
into which the eggs are received and retained until the young escape.   The greater
number of the Cirrhipoda are hermaphrodite; but it has been shown by Goodsir, that
 this is not a universal characteristic of this class.
   Among the different families of the large class Insecta, the arrangement of the gene-
 rative organs presents great  variety.  The sexes are always distinct, and impregna-
 tion is invariably effected by copulation; hence, the external aperture of  the efferent
 duct is found  to be variously modified, according to  the different circumstances  in
 which the animal lives, and the modification of  its general form.  In some classes, the
 females are very few in number, and  often whole colonies  are developed from'one
female.  This  is the case amongst the bees, termites, and ants, in which the great 
VERTEBRATA.
827
majority of the individuals are found to be neuters or workers.  In the pupa of these
last, the generative organs may be distinguished, but  they afterwards become atro-
phied.   Now it appears probable, that the development of the female organs is de-
pendent upon nourishment;  for it has been found, that the larvae which are to become
fertile females, or queen bees, have been supplied with  a much more stimulating kind
of food than that upon which the workers have been fed.
  The generative organs are double and symmetrical in insects, and several accessory
organs are found connected with the efferent duct.  Of these, the most remarkable ia
a receptacle connected with the vagina of the female, designed to receive the seminal
fluid of the male. This vesicle is termed the receptaculum seminis, and in it the sperma-
tic particles of the male may be kept in a living condition for a very long period of time.
Theoya are impregnated as  they pass the orifice of the  duct  of the receptaculum
seminis.   Besides this last, there is another organ  connected with the lower part of
the female genital organs, designed to receive the penis of the male.  This is known
as the bursa copulatrix, which, however, is not universally present.  Mucous glands
pour their secretion into the vagina near its external orifice.
  The arrangement of the  ovaries differs  considerably in various  classes.  The gland
usually  consists of caecal  tubes, which are four or five in number, and open into the
summit  of the efferent duct; while in some the tubes open separately in the sides of
the duct.  The number  of secreting tubes is very variable in the different classes.
  The testicles consist of two or more (and often  there  are very many)  simple cajcal
tubes, the arrangement  of which varies much, and which  opens into the vas  deferens
of the  corresponding side.  The vasa deferentia are often very long and much con-
voluted ; in some instances they are dilated below, so as  to form a sort  of vesicula
seminalis.
  The copulatory organs vary much in their disposition;  usually they consist of hard,
horny valvular appendages.   In some species, suckers are developed upon the legs;
and other arrangements are  found for the purpose of retaining the female during the
act.
  The imperfect or larval  form of many insects when they leave the egg,  has already
been alluded to under the  heads of metamorphosis and metagenesis, or alternation of
generations.

                                  Vertebrata.

  In the vertebrata, with the highest and most perfect development of the generative
function, we shall find the progressive elevation  characterized by greater complexity
of structure, more protracted dependence of offspring on  parent, and closer relations
of the two sexes.
  Fishes.—There are three types of structure in the generative organs of fishes.  First,
in the Cyclostomatous Group and in the Eel, the ovary consists of membranous folds
depending from the spine, between the layers of which the ova are, at the spawning
season, developed.   When mature,  they escape by the rupture of the membrane into
the general peritoneal cavity, in which they may  be found in large numbers, and from
which they escape  by a  small opening situated near the anus.   The  male organs  are
to the unaided eye so like  the female, that it is only in the spawning season that they
can be distinguished:  the  spermatozoa escape into the peritoneal cavity  in the same
manner as the ova.  Secondly, in the Osseous Fishes, the ovary, or roe, consists of a
large membranous  sac, inclosing the ovigerous folds, between  the layers of which the
ova are  developed,  just  as in those we have described, so that when the ova escape
they are discharged, not into the general peritoneal cavity, but into this ovarian sac,
and thence find their way out by a tubular prolongation of it, or excretory duct, which
opens just behind the anus.   The testicle is strictly analogous.  In neither  of these
classes does copulation take place; the spawn is cast  abroad  into the water, and  left
to be fecundated by the sperm  discharged over it  by the male, to be devoured, or to
perish in an unfecundated state, as chance may direct.  One of the most remarkable
points in  the  history of osseous fishes is  their immense  fecundity:  it is calculated
that a Cod discharges nine millions of ova in  a single spawning season.   The reason
of this  unparalleled fertility appears to  be, that there  may be the greater chance of
some escaping  and  surviving the many perils to which they are exposed.   Thirdly, in
the Cartilaginous Fishes, as  the Sharks and Rays, we have a much higher type of the
generative function.  Copulation takes place; the male is furnished with an intro-
mittent  organ, and with certain accessory parts, called "claspers," for  seizing and
embracing the female during the act of impregnation.   In the female, the ovaries  are
racemose, from the increased size and diminished number of the eggs, which, instead 
828
GENERATION.
of escaping into the peritoneal cavity, are seized by the patulous orifices of two long
oviducts, whereby they are conveyed out of the body, and by which they are furnished
with that peculiar  horny shell, which serves at once to protect and to attach them to
some fixed point.
  Reptilia.—The Amphibia exhibit, in the function of generation, an interesting link
between the piscine and the true reptilian structure;  there is no intromittent organ,
and yet copulation takes place, and the ova are fecundated neither after extrusion, as
in the  osseous fish, nor before extrusion, as in true  reptiles, but during the very act
of discharge, in exitu.  At the commencement of the spawning  season, a remarkable
papillary structure is developed on the thumbs of the male frogs, highly sensitive, and
giving rise, when stimulated, to a forcible reflex action, by which the upper extremi-
ties  are  approximated,  and tightly embrace anything  placed between  them (p.
298.)  By means of this,  the male frog firmly embraces the female, and continues to
do so  through  the whole  time  of  the expulsion of ova, without any expenditure of
voluntary action, and impregnates the ova as they pass from the female beneath him.
The  vas deferens passes through the structure of the kidney, and opens at once into
the ureter, the two being thence continued  as  one duct—a sort of  prolonged genito-
urinary cloaca.  In the  Triton,  we  go a  step  further,  and find the  ureter and vas
deferens  distinct  to their termination, and impregnation  taking place internally,
although there is no rudiment of a penis.   The Ophidians present a further advance,
and  show the first trace  of a penis; it consists  of  two erectile corpora cavernosa,
which, however, are quite separate, and constitute rather an organ of prehension than
of intromission.  In the Saurians and Chelonians another step is gained, and the two
corpora cavernosa are united in the middle line;  there  is still, however, no corpus
spongiosum, and no prolongation of the urethra, but the seminal secretion passes into
the female along the groove formed by the union of the two cavernous bodies.
   Aves.—The generative organs of birds exhibit a close analogy to those of the higher
reptiles,  the penis  is even less developed, except in the struthious  birds (ostrich) and
the  swimmers.   The ovary is racemose and single, the right with its oviduct being
permanently atrophied: a singular violation of symmetry which is confined to birds.
In this class of vertebrata, incubation, that singular substitute for utero-gestation,
attains its  highest perfection; it appears to arise from the concurrence of these three
exigencies: the necessary  size  and early maturity of the young, the  necessity of
warmth to their development, and  the incompatibility of utero-gestation with flight.
   Mammalia.—It is from the possession of a remarkable accessory organ of generation
that this important class of the highest organized beings takes its name.  After all
organic connection has ceased, the young are still dependent on the parent for nourish-
ment,  and are supported by the  secretion from a special  gland with which the female
is furnished for the purpose—the mammary gland.   The  mammalia are divided into
the monotremata, the marsupialia, and the  placental mammalia.   The monotremata are
as yet imperfectly known, but they present a curious connecting link between the ovi-
parous and mammalian type; they derive their name from possessing but one aperture,
that of the cloaca, common to  the  generative, urinary, and digestive canals,  and in
this respect resemble birds;  they are represented by the ornithorynchus and echidna
of Australia.  In the male, the penis is perforated by a urethral canal, through which
the semen, but not the urine, passes; in the female, the ovaries are racemose, the ova
large, and containing all the elements of an egg, and there are two uteri, opening by
distinct apertures  into the cloaca.   The marsupialia (called so from the possession of
a marsupium, or pouch, in which the young is lodged and suckled  after its  discharge
from the  uterus)  are  ovo-viviparous, that is, the young are brought forth  alive, but
they never have any placental connection with the parent.  Not only are there two
uteri,  but  two  vaginae, which terminate by  two separate  orifices in a sort of genito-
urinary cloaca.*  About thirty-nine days after conception, the young is expelled into
the  marsupium, where it becomes attached to one of the nipples by its mouth, and
continues thus to draw nourishment from the mother for a period of eight months ; this
peculiar method of foetal nourishment necessitates a very advanced  and disproportion-
ate development of the organs of assimilation,  which is the most remarkable charac-
teristic of  the embryo marsupial.    The placental mammalia, in the general structure
of their generative organs,  resemble man.  The testicle  consists of  seminiferous

   *  In the male, the testicles are contained  in a  scrotum placed above, and not below the
penis, in a situation analogous to  the  marsupium  in the female, and supported, like it, by
two marsupial bones; the vasa deferentia open into the urethra, which, invested  by  its cor-
pus spongiosum, passes  through the centre of the  penis, and which  now, for the first time,
we find forming a complete canal, leading from the bladder to the extremity of the intromit-
tent organ. 
MALE ORGANS OF GENERATION.
829
tubules arranged in bundles, and inclosed in a fibrous capsule.  The penis is composed
of two corpora cavernosa arising from the ischia, a corpus spongiosum urethrae, and
glans; and there are certain accessory glandular structures, vesiculse seminales, pros-
tate, and Cowper's glands, opening into the urethra in its course.  Into the different
numbers, modification, and structure of these organs it is not worth while to enter.
In the rabbit, the  ovary exhibits some trace of the racemose structure, and, by the
different modifications of the uterus, dependent on the proportionate size of its body
and cornua, we are conducted from the marsupialia, in which the two uteri are entirely
distinct, to the human female, in which the single uterus exists in its greatest degree
of concentration.

  In writing the present chapter, the authors have received much assistance from the
following works: Miiller's  "Elements of Physiology,"  by Baly;  Professor  Owen's
Lectures "On Comparative Anatomy," and his treatise  "On Parthenogenesis;" Dr.
Carpenter's  "Principles of General and Comparative  Physiology;" Victor Carus'
"System der Thierischen Morphologie;" Art. Ovum, in the "Cyclopaedia of Anatomy
and Physiology," by Dr. Allen Thompson;  " On the Alternation of Generations," by
Professor Steenstrup, translated by the Ray Society.
                      CHAPTER  XXXVII.

MALE ORGANS OF GENERATION.—TESTICLES.—VASA DEFERENTIA.—
  VESICULvE SEMINALES.—PROSTATE GLAND.—COWPER'S GLANDS.—
  PENIS.—URETHRA.—GLANDS OF   LITTRE.—GLANDULE  TYSONI.—
  VESICULA  PROSTATICA.—SEMINAL TUBULES.—SPERMATOZOA.—DE-
  VELOPMENT OF SPERMATOZOA.—MOVEMENTS OF SPERMATOZOA.

  Male Organs of  Generation.—The essential organ  of generation,
or the secreting portion of the sexual  apparatus, in the male, is the
testicle.   The efferent duct is the vas  deferens, which  opens into the
membranous portion of the urethra, and connected with  it are the
vesiculse seminales  and Cowper's glands.   The urethra is continued
forwards along the  lower  part of  the penis, or intromittent organ.
   Testicles.—Each testicle is  rather less than two inches in length.
and  is nearly one  inch broad.—Its weight is  about six drachms.
The  testicle  is covered by a  firm, fibrous, inelastic  tunic, or proper
covering, the tunica albuginea or tunica propria, consisting almost
entirely of white fibrous tissue,  in the substance of which vessels
ramifv.   It  is with difficulty divided  into  two  layers, the  inner  of
which is  the most vascular.   Adhering closely to the  tunica albu-
ginea, is the visceral layer of the serous membrane, or tunica vagi-
nalis, the  sac of  which was  originally formed by  the  descent of the
testicle from the abdomen, when  it  carries before it a  process  of
peritoneum.   In early life, the cavities of the tunica vaginalis and
peritoneum  are  continuous with  each other ; and, occasionally, the
opening remains unclosed in  the adult.   The parietal layer of the
tunica vaginalis is loose, and united  by lax areolar tissue to the other
structures which  form the scrotum.   This layer of the serous mem-
brane admits of  considerable distension ; and, in disease, a very large
quantity of  serous fluid will sometimes accumulate in  the sac, and
distend it  to a great extent {hydrocele). 
830
MALE ORGANS OF GENERATION.
  Structure of the  Gland.—The secreting portion of the organ con-
sists of a vast^ number of a minute and highly tortuous tubes, which
are arranged  in  conical lobes, or parcels, each consisting of two or
more tubes, which are covered with a layer of condensed  areolar tis-
sue,  continuous with the  corpus Highmori.   These  divisions  are,
however, not complete; for the tubes of one parcel communicate with
those of the adjoining ones.  The highly convoluted  seminal tubes
commence in blind  extremities or in loops; and, after dividing fre-
Fig. 256.
feii*

Fig. 257.
  a. Origin in blind extremities and branching of seminal tubules—human subject. 6 One of the
 blind extremities more highly magnified.

 quently, and forming anastomoses, they become less tortuous as they
 approach the mediastinum testis, where two or more unite to form
                    a short straight duct, the vas rectum ; these vasa
                    recta again  unite, so  as to form  a sort of net-
                    work, the rete testis, which occupies the  medias-
                    tinum testis or corpus Highmori.   From the rete
                    testis pass the vasa efferentia, which  are usually
                    about twelve or sixteen in number, and are much
                    convoluted ; and, by being packed together, form
                    part of the epididymis.   They open into  a single
                    and highly tortuous duct, the vas deferens, which
                    is  usually about sixteen inches in length, and
                    forms  a very hard,  round efferent duct, readily
                    distinguished, by the feel, from  the other struc-
                    tures which compose the spermatic cord.   The
                    vas deferens is lined with a single layer of tessel-
                    ated epithelium, and there is a layer of very lax
                    areolar tissue  beneath  the mucous  membrane,
Z7u%££JT&   Jhlch  woujd1 Permit of great increase in  the
b^oftheVbSnS   d,ara^er °[thl canal when it was distended with
by a thick layer of lax   secretion, o,  ng.  251.   It passes  behind  the
(^toTthin^ngltudrnai   Madder, and terminates in one of the ejaculatory
(^Aa^foFctcuiaro?   <«*«*•..»  ™ry short canal, which is  formed by
transverse fibres, e. Ex-   the union of the  vas  deferens with  the oorre.
ternal thick layer of longi-   ... j;      .  7      •   ■».    , . ,  .   .
tudinai fibres, surrounded   sponaing veswuta  semmalis, which is  situated  a
a^our u^TToVi   little external to it, upon the posterior surface of
drawing by Dr. Beale.      the bladder.
 '".:.;.v -■_

:
          !
/
Transverse section of the 
PROSTATE GLAND.
831
Fig. 258.
   Vesiculce Seminales.—The vesiculse  seminales are two sacculated
receptacles, about two inches in length and  about  three-quarters of
an inch in breadth, situated upon the posterior aspect of the bladder,
lying between it and the rectum.   They converge towards the point
at which they open, and almost meet.   The narrow terminal portion
(duct) lies for a short distance, previous to its opening in the urethra,
surrounded by the prostate.   Each vesicula may be unravelled, so as
to form a csecal tube, with several diverticula projecting from it.   It
is very much convoluted, and the convolutions are connected together
with areolar tissue, to  which arrangement the sacculated appearance
is due.
   The structure  of the  vesiculse seminales  is
very  similar  to  that  of the vasa deferentia,
but  their walls are much thinner.  There  is
an outer coat, composed of areolar tissue, in
which numerous muscular fibre-cells are found.
They are lined with a thin layer of tesselated
epithelium.
   The vesiculse are usually found to contain a
viscid,  mucus-like substance, which  may be
regarded as their secretion;  and  which, no
doubt, is of a nature favourable to maintain
the  vital  activity of the  spermatozoa, and
serves also to dilute the semen.   These organs
were formerly looked  upon as the receptacles
for  the semen;   but  a comparison of  their
 arrangement,  and an  examination of  their
 contents, in the lower vertebrata, by no means
 confirms this view, as  our friend, Mr. Pittard,
 has remarked.  In the  elephant, the vesiculse
 seminales  open into the vasa deferentia, as  in
 man ; but  seminal reservoirs are also  found  in
 this  animal.   In man,  however, spermatozoa  ^^  ^i^*"*
 are verv eenerallv found in them; and it is  b. vas deferens, c vesicuia
 aio vcij gvi"-    j                            seminalis.  d. Terminal diver-
 probable that they serve partly as receptacles  ticuia.
 for  the semen, but at  the same time, there can
 be no doubt that they furnish a proper secretion of their own for its
 dilution, and for  the preservation of its  integrity.            _  t
   Prostate Gland.—The prostate may  be described  as  consisting
 essentially of two distinct structures; first, of a  glandular portion,
 composed  of conical  or roundish  vesicles lined with  cylindrical
 epithelium and containing brown granules ;  and, secondly, of several
 layers of  fibrous tissue, with which many fibres of unstriped muscle
 are everywhere incorporated ; indeed, the proportion of the muscular
 and fibrous  elements to the glandular  structure, is so  great that
 Kolliker calculates that the latter does not constitute more than one-
 third part of the whole mass  of the gland.  The muscular fibres
  covering the prostate, were originally described by Mr. Hancock.
    The  secreting  follicles open  into  ducts,  which are  lined  with
 
832
MALE ORGANS OF GENERATION.
cylindrical epithelium, presenting similar characters to that found in
the prostatic portion of the urethra.
  The ducts, which are very numerous, open into the urethra, upon
each side of the caput gallinaginis.
  Little is known with reference to the nature of the secretion of
the prostate, or  of the function which it performs.  The secretion
is  stated to be  very similar in character to that of the vesiculse
seminales.
  Small  concretions, or prostatic calculi, are very frequently met
with in the  follicles of the gland, or are voided  during life.   They
usually consist  of phosphate of lime,  with  animal  matter,  and a
trace of carbonate of lime; and are often remarkable for their per-
fectly spherical form and smooth glistening surface. They commence
by the deposition  of calcareous matter in the walls of large  oval
cells, which are, probably, altered epithelial cells of the gland itself.
Dr.  Handfield Jones has carefully investigated  the formation of
prostatic concretions.*
   Cowper's Glands.—These small glands are two in number, and
are  situated anterior to the prostate, between  the layers  of  the
triangular  ligament.  Their somewhat long excretory  ducts open
into the  bulbous portion  of the  urethra.   They  are  composed of
vesicles, lined with tesselated epithelium, which  pour their secretion
into ducts  lined with columnar epithelial cells.  As in  the  case of
the prostate, the secreting portion of these little glands  is imbedded
in a fibrous stroma, which contains very numerous unstriped muscu-
lar fibre-cells.  The secretion of these glands appears to be analogous
to ordinary mucus.
  Penis.—The  penis of man is a  highly vascular organ, traversed
on its inferior surface by  the urethra; it is composed principally of
erectile tissue, which is  capable of  being  distended  with  blood.
This  erectile tissue is arranged in  three distinct  divisions  termed
the corpora cavernosa and  corpus spongiosum.  The corpora cavernosa
penis are two in number, and are separated  from each other, poste-
riorly, by a septum, composed of fibrous  tissue;  while anteriorly,
they are connected together, and might be considered as one  organ.
In  the middle line  above,  is situated the dorsal vein, and  other
vessels and nerves; while the corpus spongiosum urethras is received
into a groove beneath.   In the posterior  part of the  organ,  the
corpora cavernosa are separated  from each other by a considerable
interval, and each is inserted into the rami of the ischium and  pubis ;
these two  diverging extremities of the corpora spongiosa are termed
the crura  of the penis.
  The corpora cavernosa are invested with a layer  of  firm  fibrous
tissue, which contains numerous fibres of the  yellow elastic element.
   The corpus spongiosum urethrse  surrounds the urethra, and  com-
mences behind, in a dilated portion situated between the crura  penis ;
and it terminates anteriorly in the expanded glans penis, the rounded
* Medical Gazette, Aug. 20th, 1847. 
URETHRA.
833
Fig  259.
margin of which is termed corona glandis, and the constricted part
beneath, the cervix or neck.
  These bodies consist  of a vast number of small venous  sinuses,
which communicate with each other upon all sides, and contain venous
blood.   The walls of the sinuses  or trabeculse are lined with a layer
of tesselated epithelium, external  to which is found the proper fibrous
tissue,  or trabecular  tissue.  This is  composed of white and yellow
fibrous tissue, and fibres of organic muscle.  The arteries and nerves
for  the supply of the organ are  supported and  surrounded by this
texture.
  The arteries of the penis are branches of the pudic; and in their
arrangement, present certain peculiari-
ties, which  are  well  worthy  of  notice.
The smaller divisions, after pursuing  a
tortuous course in the trabecular tissue,
at length open into  the venous  sinuses,
without  entering into the  formation of
any capillary  plexus.   In the posterior
part of the penis, J. Muller discovered
several minute arteries,  which were much
convoluted,   and  assumed  the  twisted
appearance   of  tendrils;  whence  they
were termed the helicine arteries.   Kolli-
ker has shown that  these arteries  ter-
minate in  minute vessels, and  not  in
blind extremities, as was originally sup-
posed ; the  minute terminal vessels
mately open into the  venous spaces.
arrangement of the arteries in the
similar to that just described.
   Urethra.—The male urethra is the canal which extends  from the
neck of the  bladder to the end of the penis.   It is about eight inches
and a  half  in  length, but varies slightly in different cases.   The
tube itself is lined with mucous membrane, and its diameter is not by
any means the same in  its whole  extent.   Its direction is that of  a
double curve, like the letter/.  The walls of the urethra are strong,
and composed principally  of fibrous tissue, with a layer of unstriped
muscular fibre, the arrangement of which has been well described by
Mr. Hancock.
  The urethra is divided, by descriptive anatomists, into three por-
tions ;  the prostatic, being about twelve lines long;  the membranous,
about  three-quarters  of  an inch in length in its  upper part, but only
half an inch in its lower portion ; and the remainder, by far the most
extensive portion of the  canal,  called the spongy portion,  which
reaches to the orifice.
  The prostatic  portion of the urethra is its widest  part, and lies
imbedded in the upper part of the prostate, above its  middle lobe.
  At  the neck of  the  bladder, the mucous membrane forms a fold,
called the uvula vesicse.  Anterior to this is a narrow ridge,  rising
from the floor  of the tube, about  nine lines  in length,  and about one
       A small artery of the corpora caver-
     nosa, giving off a lateral branch, from
     which proceed helicine arteries, ter-
     minating in very small vessels, which
     are continued in the trabecular tissue,
.-.l*:  (a-)  *• Wall of the arteries.  After
Ultl- Kolliker.
The
corpus spongiosum urethrse, is 
834
MALE ORGANS OF GENERATION.
and a half lines in height in its highest part, called the verumonta-
num, caput gallinaginis, or crest of the urethra.*   On each side of
this, the mucous  membrane forms a depression, the prostatic sinus,
into which the ducts of the prostate gland open.
  At the highest part of the verumontanum is a little sinus, the vesi-
cula prostatica.   It is here that the ejaculatory ducts open.
  The membranous  portion  is that  narrowest part of the urethra
which lies beneath the pubis and passes through the layers of the
triangular ligament.   It is surrounded with muscular fibres, and the
compressor urethrce muscle  is situated  upon this  part of the tube;
beneath it are Cowper's glands.  This part of the urethra commences
at the anterior extremity of the prostate, and terminates in the bulb-
ous portion.  Its upper surface  is rather longer than the lower one,
and it curves upwards.
  In  the evacuation of the bladder, it is most  likely that the com-
pressor urethrse  muscle, which contains striped fibre, and guards the
membranous  portion  of the urethra, becomes relaxed;  then follows
the relaxation  of the sphincter vesicse, and  the contraction of the
fibres  of  the bladder (detrusor urinse), which  causes  the  urine to
escape from the  urethra with considerable force.
  The spongy portion of the urethra is about six inches in length, and
is so called, because  it is  surrounded  by the corpus  spongiosum
urethrae.  That part of the canal in the bulb is somewhat dilated, but
the diameter of  the  greater  part of this portion of the canal is uni-
form.   Cowper's glands open near the anterior extremity of the bulb-
ous portion.   When  it  reaches the  glans,  however, it undergoes
another dilatation, the fossa navicularis.   At its orifice, the urethra
is contracted.
  Mucous Membrane.—The short papillae covering the glans become
much  elongated  at the orifice  of the urethra,  and highly vascular
papillae are found in  the anterior half of the fossa navicularis (fossa
Morgagnii).  They  then  cease abruptly,  but recommence in  the
posterior part of the  glans, and are continued as far as  the bulbous
portion.
  About one-third of an inch from the meatus, on the  dorsal aspect
of the fossa navicularis, is  situated  the lacuna  magna.  In other
parts of the mucous membrane of the urethra, except in the prostatic
portion, are numerous small lacunae.
   Glands of Littre.—The  majority of these are  simple involutions
of the mucous membrane, or lacunas; but some may be  described as
small branched glands or follicles, which are numerous in the cavern-
ous portion of the urethra.   These become more simple in  the pros-
tatic  portion, and take the form of simple follicles.
   The epithelium lining  the urethra and  the small glands just re-
ferred to, is for  the most part of the columnar form.
   Glandulce Tysoniance.—These little glands are situated in  the
fold  of skin round the glans  penis.   They are modified sebaceous

  * Vide article "Vesicula Prostatica," in the  Cyclopaedia of Anatomy and Physi-
ology, by Prof.  Rud. Leuckart. 
SEMINAL TUBULES.
835
Fig. 260.
glands, and the follicles of which they are composed  contain epithe-
lium and fatty matter, resembling that which is met with in  the
ordinary sebaceous follicles of the skin.   In this locality these glands
open upon the soft skin of the prepuce, and are not associated with
hair follicles, as is usual in other situations in which they are found.
The peculiar secretion known as  the smegma preputii, is not due to
these glands alone ;  but is rather to be regarded as an accumulation
of the  moist epithelium of the glans, which is, of course, mixed with
the odoriferous  sebaceous material.  In the beaver, the epithelial
secretion is so abundant, as to accumulate in large preputial pouches,
the true  nature of which  was demonstrated by E. H. Weber.   The
secretion constitutes the substance known as castor.
   Vesicula Prostatica.—Between  the openings of the ejaculatory
ducts in the middle line of the urethra, and in  the substance of  the
caput gallinaginis, is a samll cavity, lined with columnar epithelium,
the prostatic vesicle, or uterus masculinus, as it has been termed by
Weber, from its supposed homology with the female organ.  It  has
since been described under  the name of Weberian organ, from its
discoverer.
   Seminal  Tubules.—The highly tortuous seminal tubes,  of which
the true  secreting portion of the testicle  is composed, consist of  a
fibrous coat, internal to which we  find  a basement  membrane sur-
mounted by epithelium.  Now the characters of this epithelium, and
the nature of the con-
tents of the  tube, will
be found to exhibit dif-
ferent  appearances, ac-
cording to  the  age  of
the individual; and  in
the lower animals, ac-
cording  to  the period
of the  year.   Sperma-
tozoa,  which  are the
fertilizing  agents, are
not found before pu-
berty  in   man,  and
among  animals  are
only developed at cer-
tain periods.   These
bodies appear  to be
formed by certain al-
terations  taking place
in the character of the
epithelium  lining the
tubes,  for this latter is
most   distinct   when
spermatozoa are  not being  formed; but when  the function of the
gland  is  very actively performed, the  tubes are seen to be entirely
occupied by cells, in which the spermatozoa are  ultimately developed.
   When semen is about to be formed, the following changes may be
observed to take place in the epithelium.
 ,jm
mm

 Portion of seminal tubules of man, with enclosed cells.  Mag-
nified 220 diameters,  a. Wall of the tube. b. Nuclei of fibrous
coat. c. Basement membrane.—The latter figure represents the
action of acetic acid.  d. Cells removed from the tubule. 
836
MALE ORGANS OF GENERATION.
   The cells become detached from the basement membrane, increase
in size, and assume a more spherical form, the contents at this time
being entirely granular ;  at length, however, several clearer points
or nuclei are seen  in the interior of the cell, which  is now passing
down the tubule towards the vas deferens,  while  it is succeeded be-
hind  by the formation  of new cells.  The nuclei  in  the  interior
enlarge, and are often seen  to contain  nucleoli.  The parent cell,
having much increased in size from the development of its nuclei
into cells, appears  to undergo no further change; but in each of the
contained cells, which vary much  in number, one spermatozoon is
developed on the inner wall, in  the form  of a spiral filament, as was
first described by Kolliker.   The spermatozoon  escapes into the in-
terior of the mother cell by the  rupture of its development  cell.
Others are in like manner set free; and  they arrange themselves  in
a parcel, which may ultimately consist of a vast  number of separate
spermatozoa, with all the  heads arranged in one direction and the
tails in the opposite one.
   The cause of this  arrangement  is  probably somewh'at similar  to
that which determines the blood discs to run together, and assume
the form of a small pile of coins.   There appears to be a sort of
attraction existing  between the different spermatic filaments for each
other.  The  contained spermatozoa  are  at last set free by the rup-
ture of the parent cell, and then separate.    These changes are usually
not completed until the cells arrive at the epididymis; so that in the
seminal tubules cells alone are found, while  in the vas deferens we
only meet with perfectly developed spermatozoa.
   Spermatozoa.—The spermatic filament or spermatozoon of man is
a perfectly clear hyaloid filamentous  body, in which a dilated por-
tion, termed the body or head, may be observed,  from which is  pro-
longed a long tail or filament, which gradually tapers to an extremity
which is hardly visible from its extreme tenuity.   The head or larger
extremity is  flattened from side to side  and of  a conical form, the
pointed extremity being anterior.  The length of the spermatozoon
is  about g^th  of an inch, and the width of the body in  one direction
about the go'ooth? ana* not more than the T^ootft 0I> an *ncn m tne
opposite.   The tail varies somewhat in length in different specimens.
                       The characters of the spermatozoa vary much in differ-
       Fig. 261.         ent animals; thus, in the rat and  mouse, the head or body
                     is unsymmetrical and curved.  In the squirrel, the ante-
                     rior extremity of the head is rounded, and wider than any
                     other portion.  In birds, the head is usually attenuated.
                     In reptiles  and fishes, the characters of the spermatozoa
                     vary much in different examples.  Among the inverte-
                     brata, those of the Crustacea are very remarkable in form.
                     For a detailed account of the characters of the sperma-
                     tozoa in different classes of animals, we must refer the
                     reader to the excellent  article, Semen, in the Cyclopedia
                     of Anatomy and Physiology, by Wagner and Leuckart.

                        Development of the  Spermatozoa.—The de-
J^llT^lJ^Lm-  y^P™^ °f  the spermatozoa has been care-
                     fully investigated  by Wagner,  Siebold, and
Kolliker.   The different stages are traced more readily in many of
 
MOVEMENTS OF THE SPERMATIC FILAMENTS.
837
Fig. 262.
 Development of the sperma-
tic filaments of the rabbit, a
Parent cell, with five nuclei,
b. Each nucleus of the parent
cell containing a spermatic
filament.   e. Nucleus  with
spermatic filament,  d. A pa-
rent cell, with a number of
the lower animals than  in  man.   In the rabbit, Kolliker has been
able to observe the single spermatic filament within the cell attached
to the wall and making two or three turns in a spiral form.  It may
now be looked upon as almost  certain, that  each  spermatozoon is
developed not from any change of the cell, but
from the contents within the cell  itself.  These
cells  are themselves developed in  the interior
of a  larger or mother cell, into the interior  of
which the spermatozoa escape by the rupture
of their developing cells, and are  at last  set
free  by the  destruction of  the wall of the
parent  cell itself.   Professor Kolliker, in  his
latest investigations, has arrived at the conclu-
sion  that the  spermatozoa are  not developed
in the nuclei of the cells, but  from  them.
 The nucleus becomes of an oval  form, and one
 extremity is elongated to form the filamentary
 tail,  while  its principal  part constitutes  the
 body  of  the  filament.   In this  case, they
 arrange themselves parallel to each other,  the  rent
 heads being in one  direction, and  the tails  in spermatic aumjnto settee
 the Opposite.                                 development.
   Movements  of the Spermatic Filaments —
 When  the  spermatozoa have escaped, their active  movements com-
 mence • and by  the continual vibrations of the filamentous tail,  they
 are propelled forwards, according  to Henle, at the rate  of one  inch
 in seven  minutes and a half.  The  tail  alone possesses the power of
 movement, and  the force  of the motion is  sufficient to move objects
 manv times the  weight of the spermatozoon.                      ,
    The movements are stopped by all those solutions which act chemi-
 cally upon the  spermatic  particle.  In water, the  activity  ot  the
 movements is at first increased, but  it  soon stops altogether, proba-
 bly in consequence  of endosmosis.   Urine very soon puts a  stop to
 the  movements.   The electric  spark instantly stops the motions;
 but, according to Prevost,  galvanism exerts no action upon them.
    After spermatozoa have  become quite motionless and appear to
 be  dead, movements may be excited by the addition of concentrated
 solutions of  different substances, such as  sugar, albumen, urea, and
 various salts.  Caustic  alkalies in various degrees of concentration,
 from -»„ to A, are  special excitants of the movements.   Moreover,
 Kolliker states  that semen  dried in indifferent  substances  and  in
  saline solutions, in  certain cases, may have  its motion  restored by
  dilution with the same fluid  or  with water.  The  motions cease in  a

  htTh^nS^r'female  organs of generation the movements
  continue  for a  longer period than in any other situation,   in tne
  wc^la  "minufof insects, spermatozoa have been known to retam
  thpir nnwer  of  movement for many months after they had been cus
  charged by the male, and  in  the" higher  mammalia, the movement
         54 
838
MALE ORGANS OF GENERATION.
continues  in  the  mucus lining the generative organs of the female
for many days after copulation.
  It must be borne in mind that the semen does not consist only of
the secretion of the  testicle, but that it also  contains the secretions
of the prostate,  vesiculse seminales,  and Cowper's  glands.  What
purposes these different secretions serve, it is difficult to say, but it
is probable that they merely effect the dilution of the fluid in which
the spermatozoa move, and thus render it a more favourable medium
for their diffusion.
  The movements of the spermatozoa have been regarded by some
as due simply to  the  existence of endosmotic currents, while other
authorities have attributed them  rather to the inherent contractile
property of the tissue of which they are composed.
  The action of certain saline solutions upon these movements, does
not seem, to us, to place this question in  a much  clearer point of
view:  since the mere physical alteration occurring in their contents
would  alone be  sufficient to excite the contraction of the tissue of the
spermatozoon.
  That the spermatozoon is really the essential part of the semen,
and is that in which all the mysterious fecundating power  resides,
may be now looked upon as proved beyond a doubt.   The later
beautiful observations  upon the ova  of the frog, of our lamented
friend, Mr. Newport, have  shown that impregnation does not  take
place unless the spermatozoon actually passes through the  vitelline
membrane  and comes into immediate  contact with  the  yolk  sub-
stance.
  The chemical analysis  of  the  semen has not led to any very im-
portant results.   The  investigations  of Frerichs are some of the
latest that have been undertaken  upon this subject.   The most im-
portant fact which he has established is, that the spermatozoa con-
sists of binoxide of protein, the substance of which  epithelial  cells
are chiefly composed.  The other constituents of semen are phosphate
of lime, fatty matter,  a certain quantity of extractive  matter  with
alkaline sulphates and phosphates, and a small quantity of phos-
phorus in an unoxidized  state.   The imperfectly developed semen
contains albumen, but this substance  cannot be detected in the fully
formed secretion.
  From the  various  phenomena  which we have  been  considering,
and from many other facts which  might have been brought forward,
we are led to conclude that the spermatozoon is  to  be  regarded in
the light  of an  epithelial cell, or, rather, its  nucleus, modified in
structure and endowed with peculiar  properties.   Its mode of de-
velopment, the  continuous  and obviously involuntary nature of the
movements, and lastly, its chemical characters,  all tend  to this con-
clusion, while they place the originally received notion of the animal
nature of the spermatozoon without the bounds of speculation.
  Upon the nature of the force which is communicated  by the  sper-
matozoon to the ovum, we know nothing.  Whether it is to be looked
upon as a catalytic action, or whether the changes induced are of a
chemical nature, are  questions to  which we  can give  no answer. 
FEMALE ORGANS OF GENERATION.
839
Certain it is, that the integrity of the spermatozoon is necessary for
fecundation.   The  spermatozoa  of hybrids have  been found, upon
examination, to  exhibit structural  imperfections, and it has  long
been known that these animals are incapable of producing offspring.
  That all the wonderful changes taking place in the ovum, which
lead to the formation of the embryo and the development of the new
being, result from the agency of the  spermatozoon, is certain ;  but
how these are brought about, seems beyond the pale of human know-
ledge.

  Upon the subjects treated  of in the present chapter, the student may refer to Sir
Astley Cooper's " Observations on the Structure and Diseases of the Testis;" Lauth's
" Memoire sur la Testicule Humaine;" Professor Kolliker's Microscopic Anatomy,
and articles in the " Microscopical Journal;" Hancock, " On the Physiology of the
Male Urethra ;" Article " Semen," in the " Cyclopaedia of Anatomy and Physiology."
                    CHAPTER XXXVIII.

FEMALE ORGANS OF GENERATION.—OVARIES.—GRAAFIAN  FOLLICLES.
  —GERMINAL  VESICLE.—PAROVARIUM.—FALLOPIAN  TUBE.—UTE-
  RUS.—VAGINA, AND ACCESSORY ORGANS  OF GENERATION  IN THE
  FEMALE.--FEMALE URETHRA.

  Female Organs of Generation.—The formative organ in the female
is the ovary, in which the ova are developed and prepared for fecun-
dation.  From the ovary, the ova pass into  the  Fallopian tube or
efferent duct,  which opens into  the  uterus, the cavity designed  for
the reception  of the ovum  after it has been  impregnated,  in which
the formation  of the embryo  takes  place, and its  development into
the form  of the future being occurs.   From  the  uterus  passes  the
vagina or tube which receives the penis  of the male in  copulation.
With  the vagina are connected certain glands and  accessory organs.
   Ovaries.—The ovaries are two in number, of an  oval form, and
flattened antero-posteriorly; they lie in the cavity  of the  pelvis, and
are enclosed in a fold of the broad ligament of the uterus, with which
organ they are connected  by  a narrow cord  or round ligament.
Each  ovary is  invested with a firm  capsule of  condensed fibrous
tissue, which is  covered with peritoneum, and is usually attached to
the corresponding Fallopian tube by one of the fimbria of the latter.
The ovary is composed of a firm, fibrous, and highly vascular stroma;
in which are imbedded, at various intervals, a number of small cavities
or vesicles, originally discovered by De  Graaf, hence called  Graafian
vesicles.   These contain  a  serous fluid, with  a  considerable number
of cells, amongst which the  ovum lies.  In  the  adult ovary, there
are usually from ten to  fifty, or more,  of these  Graafian vesicles,
varying in size from a small pin's head  to that of a pea.   The largest
are situated chiefly towards  the peripheral part  of the  organ.   In 
840
FEMALE ORGANS OF GENERATION.
the ovary of the advanced fcetus  and new-born child, Graafian folli-
cles  are abundant, and, even  at this early period, the ovum  can be
seen within them.   The fibrous stroma of the ovary is exceedingly
firm and hard;  it  consists principally of  a modification of white
fibrous tissue, the fibres of which interlace in all directions ; but it is
highly vascular, especially at  the period of puberty.
   Graafian Follicles.—The  Graafian follicles  or  ovisacs consist,
when fully developed, of a closed cavity and contents.   The walls
are composed  externally of a firm fibrous membrane, which  is con-
nected with the fibrous  structure of the ovary; internal to which is
a softer and more spongy tissue, containing numerous fusiform cells
and fibres, more  loosely arranged than  in the external part  of  the

                             Fig. 263.
 Ovary of human subject, a. Graafian follicle with opening, b. Inner lining of Graafian follicle
or membrana granulosa,  c. Outer portion of the same. d. Ovum. e. Vascular wall of follicle
After Coste.

follicle.  Internal to this, especially in young follicles, a clear hyaloid
basement membrane  may be  observed,  upon the  surface  of which,
lining the entire follicle, is  a tolerably thick layer of epithelium, the
membrana granulosa  of authors.   The epithelium is much more
abundant in that part of the  follicle in which  the ovum is situated;
indeed,  it is entirely imbedded in it.   According to the observations
of Dr. Barry, the ovum  is attached to the walls of the follicle by
certain  bands, termed by him  retinacula.  It is, however, not  easy
to demonstrate satisfactorily this peculiar arrangement of the mem-
brana  granulosa.   The  cells  of  the membrana  granulosa  of the
Graafian follicle have a polygonal form, and immediately around the
ovum are collected into a sort of ring, which is attached to the ex-
ternal clear membrane, or zona pellucida,  of the ovum.  This layer
is termed by Dr. Barry the tunica  granulosa.   The so called retina-
cula are composed of similar  cells,  of  which many are also found
floating in the fluid of the follicle,  which is entirely lined by them. 
GERMINAL VESICLE.
841
Fig. 264.
  Ovum.—The ovum is invested with a clear, homogeneous, perfectly
transparent,  firm, elastic,  and tolerably
thick membrane, exhibiting an  appear-
ance, when examined by the microscope,
very similar to that of the elastic laminae
of the cornea, the vitelline or yolk mem-
brane,  or  zona pellucida;  the  latter
being  the  term  always  employed  in
speaking of the mammalian  ovum.  The
zona  pellucida  appears as  a perfectly
clear ring, limited  on  either  side by a
well defined  dark outline.   Within this
membrane is the yolk, which is composed
of a fluid containing proper yolk granules
and oil  particles, with  the clear bright
germinal vesicle, containing within it
the germinal spot, lying  close  beneath
the zona pellucida.
  The ovum is about T^th  and  the ger-
minal spot about yoSoth to  g&oth °f an
inch in diameter.
  The yolk granules differ much in size
and form  in different animals.   They
are much more numerous in mature  ova
than  in ova at an early stage of develop-
ment, as was pointed out by Bischoff, an
observation which we can fully confirm.
They appear to be  composed of a pro-
tein compound, with  much fatty matter.
 Mammalian ova. The upper figure
shows an ovum at an early stage of de-
velopment. The second figure, a mature
ovum.  a. Zona pellucida.  6. Yolk. c.
Germinal vesicle, d. Germinal spot.
The lower figure shows the zona pellu-
cida a, ruptured, and the escape of the
yolk granules (6) and germinal vesicle
through the opening. From Coste.
Fig. 265.
 Ova in various stages of development, from the toad's ovary. In the right figure some very small
ones are observed.

   Germinal Vesicle.—The germinal vesicle, or vesicle of Purkinje,
consists  of  a perfectly clear  cell, filled with transparent  contents,
but containing one dark spot,  the germinal spot.
   From  some  observations of Kolliker  and Bagge upon the deve-
lopment  of  the ova of intestinal worms, it  appears that the germinal
spot is the  part of the ovum  which is first formed ; but it may be
regarded as a fact, that the germinal vesicle  precedes the formation 
842
FEMALE ORGANS OF GENERATION.
of the yolk and the zona pellucida.   The immediate formative organ
of the ovum is the Graafian vesicle.
  As the  ovum  approaches maturity, it passes from the centre  of
the Graafian follicle towards its peripheral portion, and becomes im-
bedded  in the  membrana  granulosa, which increases in thickness
until it entirely surrounds the ovum.  At the same  time, the zona
pellucida increases in thickness, and the germinal vesicle, which was
originally situated in the centre of the yolk, makes its way towards
the circumference.
  Parovarium.—Diverging from the hilus of the ovary, may be seen
a few canals, which appear to  be  the remains of the Wolffian body,
an organ which reaches its maximum of development  in intra-uterine
life.  These tubes have been termed the parovarium.
  Fallopian Tube.—The Fallopian tube, or oviduct, is a fibro-mus-
cular canal, lined with ciliated epithelium, opening by one extremity
into the uterus  and terminating in the other by a wide fimbriated
orifice, morsus diaboli, which opens into the cavity of  the perito-
neum.  Each Fallopian tube is usually, however, connected to the
corresponding ovary by one of its fimbriae.
  The Fallopian tube is invested with  peritoneum, and  at the fim-
briated extremity, the serous membrane becomes continuous with its
mucous lining.   The muscular fibres of the Fallopian tube are dis-
posed in  two layers; the  external  having a longitudinal and the
more internal a circular course.  The  contractile fibres are mixed
with much fibrous tissue.  The contraction of the oviduct has a ver-
micular character.  The mucous membrane is disposed in longitudi-
nal folds, upon which lies  a single  layer  of columnar  epithelium.
These cells are ciliated,  and by the vibration of the  cilia, a current
is produced, the direction of which is from the  ovaries towards the
uterus ; so that the transmission of the  ovum into  the uterus would
be  favoured, while the passage of the spermatozoa  along  the tube
would be retarded.
   Uterus.—The uterus is a firm hard body, of a pear  shape, flattened
more or less anteriorly and posteriorly.   On each side, at the upper
part, are situated the two angles into which the Fallopian tubes open.
The portion above this point is called the fundus, while the lower
constricted part of the organ is spoken of as the cervix or neck, and
that part  situated between the cervix and fundus is denominated the
body. The highest part of the neck is spoken of as the os internum.
The cavity of the uterus is of a triangular shape, about an inch and a
half in width at its upper part, where the Fallopian tubes open; but
in the unimpregnated state, its walls almost touch  each other, so as
to leave  a very slight interval, which is usually occupied by mucus.
The cavity terminates in the os uteri, or os tincse, a transverse open-
ing, bounded anteriorly and posteriorly by two thick and rounded
lips.
  The uterus undergoes extraordinary  alterations in form and size
after the impregnation of the  ovum, and becomes very vascular and
endowed with a highly contractile power.
  The walls of  the unimpregnated uterus are about half  an inch in 
UTERUS.
843
thickness in their thickest part, and c
fibres,  with a  certain  quantity  of
fibrous  and  areolar  tissue.   The
muscular fibres have been said to be
arranged  in three layers, but the
limits of these layers are  not very
clearly defined. The outermost layer
is very thin, and is incorporated with
the sub-peritoneal  tissue.   It con-
sists of longitudinal and transverse
fibres, many of the latter, after in-
vesting the anterior  and  posterior
surfaces of the  organ, lose  them-
selves upon the Fallopian  tubes, or
enter  the  broad  and  round  liga-
ments.   The middle layer makes up
the greater part of the  thickness of
 the  uterine walls, and consists of
 strong bundles; which also run,some
 in  a longitudinal  and  others in a
 transverse  direction.   It is in this
 layer that the greater number of the
 vessels which supply the organ, and
 which  become so enormously deve-
 loped in  pregnancy, ramify.   The
 innermost layer is thinner, and com-
 posed  chiefly of  thin  longitudinal
 fibres.
   Round the external  os  uteri,  the
 transverse  fibres  are  very abund-
 ant, and collected together beneath
 the mucous membrane, so as to form
 a sphincter muscle.
    In these different layers, in  the
  virgin  uterus, the muscular  fibre-
  cells for the most part are  seen as
  short spindle-shaped cells, in many
  of which, oval elongated nuclei  can
  be  demonstrated.  At this period,
  the cells are often seen to be of very
  irregular form,  and are not always
  very readily made out. The muscu-
  lar fibre-cells undergo  increased de-
  velopment  in the pregnant state,
  and towards the end of this period,
  will be found to be very long cells
  with a distinct oval nucleus.   The
  cell terminates  in  long  thin  and
  pointed extremities (fig. 266). After
  delivery, these cells again diminish
list of pale organic muscular

      Fig. 266.
dimensions, a  number  of fat 
844
FEMALE ORGANS OF GENERATION.
Fig. 267.

globules appear in  their interior, and  ultimately they regain their
former appearance  (fig.  267); while, at the  same time, the entire
                        organ returns to its former volume.
                          The mucous membrane of the uterus forms
                        a pale and not very thick lining membrane.
                        In  the fundus and body of the organ, it is of
                        a redder colour than in the cervix, in conse-
                        quence of the  greater vascularity  of this
                        part.
                          The epithelium is of the ciliated variety.
                          Imbedded in  the mucous membrane of the
                        uterus are numerous glandular follicles, much
                        resembling  the  follicles  of Lieberkuhn,  in
                        the intestine.   These follicles are lined with
                        cylindrical epithelium.  They appear to form
                        a little whitish mucous  secretion.  In preg-
                        nancy, these glands  are  enormously  deve-
                        loped; and we  shall  consider  the changes
                        taking place in their structure, when  de-
                        scribing  the  alteration which takes place in
                        the mucous  membrane of the uterus after
                        conception.   The mucous membrane of the
                        cervix uteri  is gathered into deep folds, form-
                        ing rugae, between which are seen secondary
                        rugae, with a few follicles  opening between
them.   These rugae were described  by the older anatomists, under
the terms plicce palmatce, arbor vitce  uterinus, etc.
  In the mucous membrane of the neck of the uterus, are situated
the so called glandulce, or ovula Nabothi, which  secrete  the thick
mucus usually plugging up  this part  of the canal.   These are closed
follicles, and it is  probable  that,  at  certain periods, they burst, dis-
charging  their  contents, and  are  succeeded  by the development of
new follicles.
  Surrounding the os  uteri  there are several tongue-like processes of
mucous membrane, the villi of the os uteri.  Each  contains a vascu-
lar  loop, and is covered  with squamous epithelium.*
  The nerves of the uterus  are derived from the hypogastric plexus.
According to Dr. Beck,  the nerves spread out upon  the  surface of
the uterus itself are  few in number, and consist of branches which
do not unite with each other so as to form a plexus.   Dr. Lee de-
scribes  numerous  ganglia connected with these nerves; and his dis-
sections would appear  to show that the uterus is much more  abund-
antly supplied  with nerves, than is admitted by  anatomists  gene-
rally.   We are not, however, prepared  to  admit  that  the textures
displayed  in the  elaborate dissections  of Dr. Lee, are entirely or
even in great part nervous,  or that  the  bodies which he has repre-
sented  as  ganglia, are really of this nature.   This anatomist, like
 Muscular fibre cells from the
uterus, three weeks after partu-
rition, showing the fat globules
in their interior. The four cells
to the left have been treated with
acetic acid.  After Kolliker.
  * These villi have lately been carefully described by Dr. Tyler Smith, Med.-Chir.
Trans., vol. xxxv. 
VAGINA.
845
William Hunter, and Tiedemann, considers, that in the gravid uterus
the nerves become much increased in  size; an opinion which Dr.
Beck  has failed  to  confirm  in his very careful and  elaborate dis-
sections.*
   The ligaments of the uterus  are described in works on descriptive
anatomy.   They are the anterior and posterior ligaments, the broad
ligaments and the round ligaments. The two first being merely folds
of peritoneum, the latter a rounded cord about five inches in length.
Mr. Rainey has shown that  the round ligament of  the  uterus con-
tains  numerous  striped  muscular fibres.  He  describes the round
ligament as arising by "thin fasciculi of tendinous fibres; the inner
one from the tendon of the internal oblique  and transversalis  near
the symphysis pubis, the middle one from the superior column of the
external abdominal ring near to its upper part, and the external fas-
ciculus from the inferior column of the ring just above Gimbernat's
ligament."
   The fibres pass backwards and outwards, soon become fleshy, unite
to form a rounded cord which runs between the layers of peritoneum
forming  the  broad ligament of  the uterus, and is inserted into the
upper and anterior part of the  uterus.  The  action  of these  fibres
would be to  draw  the  uterus  forwards  and thus elongate the
vagina.f
   Vagina, and Accessory Female Organs of Generation.—The vagina
consists of an external or fibrous layer, and a muscular coat.   It is
lined  by  mucous membrane.
   The fibrous tissue of the external coat contains many fibres of the
yellow elastic element, and a large network of vessels, with plexuses
of veins which form an erectile tissue.
   The muscular fibres run partly in a longitudinal direction, and
are partly arranged in transverse bundles which encircle  the vagina.
   The mucous membrane is of a  pale  reddish  colour, thrown into
many small, firm, prominent folds, columnse rugarum, separated by
fissures.   The  epithelium of the vagina is  very large,  and of the
scaly  variety.   These cells are  almost always present in the urine of
females.   The nucleus  is usually seen very distinctly, and is of an
oval form.  They present examples of the largest epithelial cells in
the body.  Close to the external orifice, the mucous membrane forms
a  reduplication, termed the hymen, which extends across the poste-
rior part of the opening.
   There are two small glands, the glands of Bartholini, in the female,
which correspond to Cowper's glands in  the male.   They are small
branched glands, the ultimate vesicles of which are lined with tesse-
lated  epithelium.  They appear  to secrete  a clear  yellowish thick
mucus.
   The corpora cavernosa of  the clitoris correspond  in structure  to
those of the penis of the male,  but are of very small  size.  Valentin
has described helicine arteries, as in the penis. In the mucous mem-
brane of  the external female genital organs, are numerous glands;

   * Phil. Trans. 1846, part ii.             f  PhiL TraDS- 1850' Part iL P' 515- 
846
PUBERTY.
and in the labia majora are some sebaceous glands, opening into the
hair follicles, which are so numerous in this region.
  The papillae  in this situation are very numerous and highly deve-
loped, and are covered with scaly epithelium.   The submucous tissue
is abundant, loose, and without fat; it contains  many fibres of the
yellow element.   At the labia majora, the mucous membrane becomes
continuous with the external skin, to which it gradually approaches
in structure.
   Urethra.—The female urethra is much shorter and wider than that
of the male.  It is about an inch and a half in length, and terminates
in the  meatus urinarius, which opens  in the  vulva between  the
nymphse.   This canal may be enormously dilated without  danger,
and a very large calculus has often been extracted from the female
bladder through it.  The mucous membrane, especially near  the
bladder, contains many follicles.

  Besides the works already  referred to in the  Notes, the authors recommend the
reader to consult the following: Kolliker's " Manual of Human Histology," translated
by Busk and Huxley, Cavendish Society;  Dr.  Barry's Papers in  the Phil. Trans.,
1838-40; Dr. Lee's " Memoirs on the Ganglia and Nerves of the Uterus," 1849; Dr.
Snow Beck "On the Nerves of the Uterus," Phil. Trans., 1846; Quain and Sharpey's
Anatomy.
                      CHAPTER XXXIX.

PUBERTY.—MENSTRUATION.—MATURATION  AND  DISCHARGE OF OVA.
  —FORMATION OF CORPORA LUTEA.—STRUCTURE OF CORPUS LUTEUM.
  —DISTINCTION OF THE TRUE FROM THE FALSE CORPUS LUTEUM.

  The period of puberty commences at different  ages, is characterized
by different phenomena, and lasts during widely different  periods of
time, in the two sexes.   In  the male, puberty seldom occurs before
the fourteenth or fifteenth years.  It is marked by increased deve-
lopment of the genital organs, the formation of spermatozoa, and the
occurrence of sexual feelings.   Besides these changes, however, there
are others scarcely less striking and characteristic, as  the growth of
hair on the face and pubes,  increased development and symmetry of
the limbs and general outline of the body, an alteration in the phy-
siognomy, a greater capacity of the respiratory organs, and a strik-
ing change  in  the  character of the voice, which  becomes of a deep
tone, very different  from that of boyhood and of the female sex.
This alteration of the voice does not  take place in eunuchs, who re-
tain throughout  life a  shrill  tone, of higher  pitch, approximating
more in character to the female voice than to that of the male.  Per-
fectly-formed spermatozoa are not found in the  genital organs of the
male before the period of puberty.  The power of procreation lasts
much longer in the male than the female, and often continues up to 
MENSTRUATION.
847
the sixtieth or sixty-fifth years; and instances of virility are recorded
at the advanced age of one hundred.
   In  the human female, puberty is likewise  characterized by the
occurrence of certain local changes in the generative organs, and also
by changes of a more general character occurring in the body. About
this time, which usually occurs between the thirteenth and sixteenth
years, but somewhat earlier in hot climates, the organs of generation
undergo a considerable  increase  in  size; the  breasts enlarge, and
an increased deposit of fat takes  place over the surface of the body
generally.  The most  important indication, however, of puberty, or
aptitude for procreation, in the human female, is  the appearance of
the catamenia.  Nevertheless, instances have occurred in which the
menstrual secretion was retarded for several years, or even in which
it never appeared, although the susceptibility for procreation existed,
and impregnation had taken place.   Hence, although  the  presence
of the menstrual discharge indicates  that  the period of puberty has
arrived, its absence cannot be looked upon as a proof of the want of
procreative  power; while in some instances, the  catamenia may
appear  regularly without impregnation ever taking  place,  in conse-
quence  of certain abnormal  conditions of  the organs of generation.
The period of puberty is more affected by the habits of the individual
than by temperature, although the latter probably exerts some slight
influence.  In Africa, menstruation is said to be common as early as
the eighth  or  ninth year; but in colder climates, and in our own
 country, it seldom  occurs before  the thirteenth year, and usually not
 till the fifteenth  or sixteenth year.   Still  cases  are on record  in
 which  the catamenia appeared in young  children in this  country;
 and their appearance was marked by enlargement of the breasts, and
 other changes indicative of puberty.
    In both  sexes, the  period of  puberty is much  influenced  by the
 conditions under which  the  child is placed.   Habits  of  indolence,
 luxury, and  indulgence, tend to  the early development of puberty;
 while,  on the  contrary, it occurs some  years  later in those who are
 inured  to active employments, and who are  placed under conditions
 favourable for promoting bodily  vigour and mental activity. ^
    The  catamenia occur at intervals of a month, and the  discharge
 usually continues from three to six days.   It ceases during pregnancy
 and lactation,  and, in most  women, does not recur  after the forty-
 fifth to the fiftieth  year;  but exceptions to these statements are met
 with from time to time.
    At  each  menstrual  period, the mucous membrane  of the uterus,
 and  of the generative  organs generally, becomes turgid, in conse-
 quence of an  increased local  determination of blood.  The  mucous
 surface of the uterus  is covered by a sanguineous discharge, which
 escapes from the turgid vessels.
    Of the Menstrual Fluid.—The quantity of the menstrual secretion
 varies  considerably, as also do its characters.   In this country, irom
 four to eight ounces are lost at each menstrual period, but sometimes
 the quantity is much greater.  It is  of a dark "d col°ur fr°m the
 numerous blood corpuscles it contains, and is perfectly fluid,  as it is 
848
MATURATION OF OVA.
 free from  fibrine, a character which distinguishes it from ordinary
 blood.  Besides  blood-corpuscles,  it contains a  number of  small,
 pale granular cells, and large corpuscles, containing  numerous small
 oil-globules, the so-called granular corpuscles.
   Dr. Letheby has  published an analysis of menstrual fluid which
 had accumulated to  the extent of forty ounces, in consequence of an
 imperforate hymen.   It was  thick and  black, and  it contained no
 fibrine.   Under the microscope were detected  altered blood  cor-
 puscles, exudation or  granular corpuscles, mucus cells,  epithelium,
 and granules.
      Water...........857-4
      Solid matter..........142-6

         Fat..........      5-3
         Albumen   .........     69 4
         Globuline.........491
         Haematin   .........      2-9
         Salts..........80
         Extractive matter........      6-7
   Maturation of Ova, and their Discharge from  the  Graafian Fol-
 licle.—The most important of the phenomena, however, accompany-
 ing  menstruation, is the  maturation and discharge of ova from the
 ovary.  At these periods, a Graafian follicle  becomes enlarged, pro-
jecting considerably from the surface of the ovary, and distended
 with  fluid.  Its wall becomes thin  at  one point, where it at length
 gives way, and the contents of the follicle escape into the Fallopian
 tube.  The ovum has but rarely been detected in the Fallopian tube,
 which is scarcely to  be wondered at when we consider its small size,
 and the very few cases in which we have an opportunity of search-
 ing for it with a chance of success.  It has, however, been actually
 seen in one case in the human female examined by Dr. Letheby, and
 in another by Mr. Hyett.  In animals,  it may be  detected without
 difficulty,  although it  is  only of late years  that the escape of the
 contents  of a Graafian follicle at each  menstrual  period has been
 placed beyond a doubt.   We  owe  to  Dr. Robert Lee, observations,
made  so long ago as the  year 1831, which establish the fact of the
 rupture of a  follicle, and  the  escape of  its contents, at each  recur-
rence of menstruation.  Ova  have been  detected in the ovaries at a
very early  age.
   Dr. Ritchie states,  that, even during  childhood, there is a con-
tinual rupture of ovisacs and  discharge of ova taking place ;  but  it
is  not until the  period of puberty that  the  number of ovisacs be-
comes very great, or the ova are perfectly developed and capable of
being impregnated.  At this  time, the  stroma of the ovary is seen
 to be  everywhere studded with ovisacs in various stages of  develop-
ment ; the  largest and most  mature occupying the peripheral parts
of the organ, while those  containing mature ova,  which are  about to
be discharged, form  considerable prominences, projecting from the
surface of the ovary.*

  * Dr. Barry calculates that, in the ovary of the cow, about the period of puberty,
there are as  many as two  hundred millions, corresponding  to a cubic inch of the
stroma. 
HEAT AND RUT IN ANIMALS.
849
  The discharge of ova from the ovary in animals, as in the human
subject, occurs only at certain definite periods, which vary much in
different animals.   It is only  at these times that the female animal
will receive the male, and that the aptitude for  conception exists.
At such a  time the animal is said to be "in heat"  or  "rut."   In
the bitch, this period occurs twice in the year, and lasts for about a
fortnight each time; in the sheep and in the cow, and in  domestic
animals generally, it occurs much oftener than in wild animals, and
the periods of recurrence are  not definite.
  If  the ovary of  an  animal be examined at the time of "heat," it
will be found turgid with blood, and several  Graafian  vesicles will be
seen  projecting from  its  surface, forming  prominences, the  most
superficial  portions of which  appear quite thin, and almost ready to
rupture and permit the escape of the contents of the follicle.   At
the same time, a more abundant secretion of mucus takes place from
the walls of the vagina and  contiguous parts.  In a few instances,
also, a bloody discharge has been detected in the vagina ; but it must
be distinctly borne in mind, that this is not a constant phenomenon.
It only occurs in small  quantity, and it never appears at each suc-
cessive period of heat, while it is always accompanied with increased
sexual desire.
   It  may be considered as established, that in the human female, at
 or about the period of menstruation,  a discharge of ova  takes place;
 and at these times the ovaries are extremely turgid, and their vascu-
 larity is much increased.  From very numerous observations, it has
 been distinctly proved, that conception is more likely to take place
 a few days after menstruation than at any other period, a fact which
 has led Naegele to fix the period of  delivery at nine months  and
 eight days after  the last menstrual discharge;  while,  in  a few in-
 stances, the ovum  has  actually been  seen  within a  very short time
 after its escape from the Graafian follicle.
   From these facts, most physiologists have been led to look upon
 the menstrual periods in the  human  female as identical with those
 of heat or rut in animals; a view which has  been especially advocated
 by Bischoff.                          ,        .,   .   .  .
   The maturation and escape of ova, then, in all animals, is a peri-
 odical phenomenon, and even in the human  subject, if not accom-
 panied with, is shortly followed by, increased sexual desire; while,
 in animals, sexual intercourse takes place at these times a one.   lhe
 rupture of the follicle is probably due to the increased local deter-
 mination  of blood  at these  periods, by which the contents of the
 Graafian follicle are forced towards the surface of the ovary   Be-
 sides the escape of a certain quantity of blood  into the follicle, an
 exudation takes place from its lower part, so that the con tente.of the
 follicle  are gradually forced  towards the surface, and  at-thesame
 time  the  structures at this point gradually become  thinner, until at
   Tt'the peroneal coat, and  the  thin layer of the stroma  give way
 and  the contents of  the follicle escape through the fissure,   lhe
         c^n  /»ln<ap<4 leaving  a small cicatrix.                 „ ,
 ^X ,he ovum hasarrifed at tho most superfioial portion of the 
850
CORPORA LUTEA.
follicle in the  manner just described, and is  about  to  escape, the
fimbriae of the Fallopian tube grasp the ovary; and the  ovum, after
it  has escaped from the  ruptured  follicle, ordinarily falls into the
funnel-shaped cavity at the base of the fimbriae, whence it is trans-
mitted into the Fallopian tube, along which it is gradually propelled,
chiefly, no doubt, by the vermicular contractions  of the walls, but in
part, also, by the vibration  of the cilia which line its interior, into
the uterus.   In some distressing cases, happily very rare, the ovum
falls into the cavity of the peritoneum, instead of entering the Fal-
lopian tube, and the embryo  becomes developed in  this situation.
These cases  usually terminate in  death.   Sometimes, however, the
remains of the foetus escape by suppuration through the abdominal
walls, or into the intestine.
   Immediately after the escape of the ovum from the ovary,  certain
peculiar and  characteristic changes  ensue  in the follicle which con-
tained it,  and these  are  influenced by the occurrence  of impregna-
tion.   If  impregnation has taken place, the lining membrane of the
uterus also becomes the seat of peculiar changes, which do not occur
under other  circumstances.   The changes which affect  the ovum
itself, consequent upon impregnation, will  be more conveniently con-
sidered when we have referred to the manner in which corpora lutea
are produced.  The mode of formation of  the membrana decidua will
be alluded to afterwards.
   Formation of Corpora Lutea.—If the Graafian follicle of a mam-
malian animal be examined soon after the  escape of the  ovum, it is
found  to  be  almost  completely  filled with an  exudation, similar to
that which, by its gradual increase in quantity, has caused the ovum
to be  carried to  the surface  of the  follicle.   In a short time, the
outer portion  of the follicle is occupied by a firm yellow substance,
which is probably formed from plasma, exuded from its walls.   After
many careful examinations, Dr. Lee has been  led to  conclude that
this yellow matter is deposited external to both the membranes of
the follicle.*   Montgomery regards it as situated between the layers,
while some authorities  look  upon the internal surface of the inner
membrane as the  precise seat of its formation.  Dr. Zwicky con-
siders  the large cells, of which the  yellow matter is  composed, as
modifications of the small cells of  the immature follicles.   Their
nuclei are large and well defined, and they contain numerous oil-
globules in their interior.  Although bodies, which are liable to be
taken for corpora lutea, are, from time  to time, found in the virgin
ovary, a foetus has never been found in the uterus without the for-
mation of an unmistakable corpus luteum.   Haller's remark, there-
fore, "nullus unquam conceptus est absque corpore luteo," although
made so many years ago, may still be regarded as strictly true.
   At first, this exudation is  of a dark brown or brownish-red  colour,
resembling effused blood;  but  soon  the colour  becomes paler, while
its consistence is firmer and more dense.   At length  the follicle is
seen to be occupied with a  firm mass, which  appears  to be  formed
* Med.-Chir. Trans., vol. xxii. 
                MATURATION AND DISCHARGE OF OVA.            851

from a  secretion poured out from its walls, which, from its yellow
colour in man  and many  animals, has  been  called corpus  luteum.

                              Fig. 268.
  Corpora lutea of the human female at different periods.  1. Eight days after conception. 2. At the
end of the second month. 3. At the termination of the fourth month.  4. At the seventh month. 5.
Two days after delivery. 6. Twelve weeks after delivery. 7. Corpus luteum of menstruation, or
false corpus luteum, four weeks old.  8. Corpus luteum of menstruation thirty days old.
  a. Capsule of ovary, b. Substance of corpus luteum.  c. Coagulum occupying cavity in its in-
terior,  d. Stroma of the ovary.—Altered from figures by Montgomery, Kolliker, and Dalton.

Hence, for every follicle in the ovary from which  an ovum is dis-
charged, a corpus luteum will  be  found.   In  cases of twins,  two
corpora  lutea are always present; sometimes  one  in  each ovary,
sometimes  two in one.  The characters  which the corpus luteum  ex-
hibits, and the extent to which the changes giving rise to its  forma-
tion undergo, will  be determined by the circumstance of the ovum
being impregnated or not.
   Bischoff proved decisively that the ova in mammalia were detached
from the ovary at the time of heat, without coition taking place ;  and
that corpora lutea were formed  in the ovaries, just as if  coition  had
occurred, and impregnation had taken place.
   Raciborski, from numerous  experiments upon animals, has shown
that whether  the rupture of the follicles is or is  not accompanied by
coitus  or by fecundation, the appearance of the lesion which results
is, in both  cases, absolutely identical.
   Nevertheless, the corpus luteum of pregnancy, except in its earliest
stages, has been admitted  by  all observers, to possess characters by
which  it may be distinguished from the corpus  luteum formed in a
follicle from which an ovum has  been discharged without subsequent
impregnation having occurred.   Hence, true and false corpora lutea
have been  described; the  true occurring only when  conception  has
taken place, while the false are met with in the  virgin ovary.   This
distinction must undoubtedly be recognized ; but there is every reason
to believe that the development  of  a true corpus luteum  takes place
in obedience to similar nutritive changes which determine the forma-
tion of this body, proceeding  to a much greater extent than in the
case of the  false or  virgin corpus luteum in consequence of their 
852              TRUE AND FALSE CORPORA LUTEA.
being promoted by the increased determination of nutritive pabulum
and  the greater vascularity  of  the  ovaries when impregnation has
occurred.
   In the cow (according  to Dr. Dalton), the corpus luteum reaches
its maximum of development in about two weeks after the rupture  of
the  vesicle, and  in  three weeks more all  that remains  is  a  small
yellowish spot.   If,  on the other hand, the rupture of the follicle
be followed by impregnation, the corpus luteum does  not attain its
greatest size till about the middle of the seventh  month, and at the
termination of the eighth month, it is still  of large size, and some-
times forms a very  remarkable  prominence on  the surface of the
ovary.
   The corpus luteum of menstruation  is smaller than that following
conception ; its yellow colour appears very rapidly, and soon fades.
In the course of one or two months after their first appearance, they
are  no  longer to  be distinguished.  Virgin corpora  lutea  are not
vascular, and cannot be injected.
   If a  section of  the corpus luteum be made, a small cavity will be
found  in the interior, from which  several lines  appear to radiate
towards its external  surface.   This little cavity gradually contracts,
and  ultimately disappears.   According  to  Dr. Montgomery, within
the  first  three or four months  of pregnancy,  the cavity  is  large
enough to contain a grain of wheat,  and often much larger.   The
same observer has always found the  cavity absent after  the  sixth
month ;  usually it seems  to disappear between the fourth and  fifth
months.  A few  months  after delivery, the corpus luteum entirely
disappears.  Dr.  Montgomery never saw one later than  the end  of
the fifth month after delivery.
   In a medico-legal  point of view,  the characters of  the corpus
luteum  are sometimes of great  importance, and it will be  well  to
recapitulate the most important.  The true corpus luteum of  preg-
nancy  possesses very  well marked  characters, by which it  may be
distinguished from the false corpus luteum.
   Its projection from the surface of the ovary; its large size,  often
equal to that of  a mulberry, and its rounded form;  the triangular
depression and cicatrix upon its surface ; the little cavity in its centre
during  the earlier period of its formation, or the stellate  cicatrix
during  the latter part of pregnancy; its lobulated  or puckered
appearance; its firm consistence and yellow colour; its great vascu-
larity,  as may be  shown  by injection, and  its  persistence for some
time after delivery, are all important points in which the true cor-
pora lutea  contrast  remarkably with  those which are formed where
conception  has not  taken place.  The false corpora lutea are  small
in size, and do not project from the surface of the ovary;  they are
often angular in form, seldom present any external cicatrix, contain
no cavity or stellate marking in the centre; the material of which
they are composed is not lobulated, and their consistence is usually
very soft; they often resemble coagulated blood; the yellow material
exists in the form  of a very thin layer, or,  as is more commonly the
case, not a trace  of this  substance is  present.   False corpora lutea 
GENERATION.
853
are easily broken down, and  often consist either of small cysts, con-
taining serum, or of a simple coagulum.

  The following works and monographs may be consulted upon the subjects treated
of in Chapter XXXIX: Dr. W. Hunter on the "Gravid Uterus," 1794; Sir Everard
Home, in the Phil. Trans., 1817; Dr. R. Lee's article, "Ovary," in the Cyclopaedia
of Practical  Medicine, 1834. and his Lectures on the Theory and Practice of Mid-
wifery, 1844; "An Exposition of the Signs and Symptoms of Pregnancy," etc., by
W. Montgomery, M. D., 1856; Dr. Ritchie's Papers in the Medical Gazette, vol. xxxvi.;
Bischoff, " Beweis von der Begattung unabhangiger Periodischen  Reifung und
Loslosung der Eier," Giessen,  1844; Raciborski, "Comptes  Rendus," 1843;  "Dela
Puberte" et de l'Age  critique chez la Femme et de la Ponte Periodique," Paris, 1844;
M. Pouchet,  " ThSorie Positive de l'Ovulation Spontanea, 1847 ; Miiller's Physiology,
supplement by Dr. Baly; Dr. Paterson's Papers in the Edin.  Med. and Surg. Journal,
Nos. 142 and 145; Mr. Roberton's "Essays on Menstruation, and on Practical Mid-
wifery," 1851; Zwicky, "Die Metamorphose  des Thrombus," Zurich, 1845; Prize
Essay on the "Corpus Luteum of Menstruation and Pregnancy," by John C. Dalton,
Jun., M. D.,  Philadelphia, 1851.
CHAPTER XL.
IMPREGNATION OF THE OVUM.—CHANGES IN THE OVUM IMMEDIATELY
  SUCCEEDING IMPREGNATION.—ROTATION OF THE YOLK.—CLEAVAGE
  OF THE YOLK. —KOLLIKER'S OBSERVATIONS.—FORMATION OF BLASTO-
  DERMIC  VESICLE,   OR  GERMINAL   MEMBRANE.—FORMATION  OF
  DECIDUA.—STRUCTURE  OF  THE MEMBRANA  DECIDUA.—DECIDUA
  REFLEXA.

  Impregnation  of the  Ovum.—It is  exceedingly difficult to give a
satisfactory description  of the  nature  of  the  phenomena occurring
in impregnation.   It was  recently held, by Mr. Newport and other
observers, that the contact of the spermatozoa with the  exterior of
the ovum was sufficient to impregnate it.   It was supposed, that
liquefaction of the spermatozoa occurred, and that the solution thus
formed permeated the  vitelline  membrane,  and impregnated  the
ovum.   The  latest researches, however, of the same  indefatigable
investigator  upon the ovum of amphibia,  and upon the mammalian
ovum,  have demonstrated satisfactorily that the spermatozoa actually
penetrate and pass through the yolk membrane, and are thus brought
into contact  with the yolk in the interior.   This view was advocated
by Dr Barry several  years ago (in 1843), and its accuracy  has since
been  confirmed by the  observations  of Newport and  Bischoff,  and

  What  becomes of the spermatozoa  when they have reached  the
interior  is unknown.   They disappear, and become liquefied;  but
the precise manner in which this occurs  has not been determined
neither is it  known if they penetrate  far into the  substance of the

J°]Micropyle.—ln  many  ova the vitelline  membrane  is very firm
       55 
851
GENERATION.
and hard;  and it may be fairly asked, how can the delicate sperma-
tozoa perforate so tough a structure as the  investing membrane of
the yolk undoubtedly is  in these  ova ?  Much light  has very lately
been thrown upon this part  of the  process of  impregnation  by the
researches  of our friend, Dr. Ransom, of Nottingham, by those of
Professors  Muller and Remak upon the impregnation of the ova in
fishes,  and  by the investigations of Leuckart, Leydig, and Meissner,
upon the eggs of insects, mollusks,  and some of the  radiata.
   These researches establish  the fact of the existence of one or more
pores or tubes passing through the coriaceous envelope, and opening
upon its interior.  Leuckart  has shown that these  pores are charac-
teristic of all insect ova.*
   In July, 1854, Dr. Ransom made some very important observa-
tions upon  the ova of the stickleback, and  demonstrated the exist-
ence of a funnel-shaped depression,  pierced by a canal, which passes
through the chorion in the unimpregnated ovum.   This is the micro-
pyle, through which the spermatozoa pass to the interior of the ovum.
" In the act  of impregnation, one or more  (as many  as four have
been seen)  spermatozoids pass into the microplye.  Actively moving
spermatozoids may remain  in contact with the  chorion  for eighteen
minutes at  least without producing any sensible change in the ovum,
provided none of them enter the micropyle; but  when one is seen
to enter, in about a quarter of a minute a change is observable."f
   Dr.  Ransom has found the micropyle in all the  fresh-water fishes
which he could obtain.
   The existence of the micropyle in the mammalian ovum has  not
yet been satisfactorily  proved.   Remak,  however, regards certain
streaks existing in the zona pellucida as pores or micropyles through
which the spermatozoa may pass.
   Changes in the Ovum immediately succeeding Impregnation.—The
period  of time  at which the ovum leaves the ovary, and passes into
the Fallopian tube, varies considerably in different animals ; some-
times it occurs within a few hours after impregnation, while in other
instances, days, or even weeks, may elapse between the time of coitus
and the escape of the ovum from  the Graafian follicle.   In the dog,
the ovum may sometimes  be found in the Fallopian tube  within
thirty-six  hours after coitus,  and  at others, not until ten or  twelve
days afterwards.   In the roe-deer, four months are said  to elapse
between the act of impregnation and the escape of the ovum, accord-
ing to the observations  of M. Pockels.  About the time  that  the
ovum leaves the  ovary, the cells of  the membrana granulosa imme-
diately surrounding it undergo a  curious change of form, becoming
club-shaped; their  pointed extremity being attached to the zona
pellucida, by which a  stellate appearance is  produced (fig. 271, b).
Each cell  contains a nucleus; and  the ovum, with these radiating
cells, presents a stellate appearance.   The cells afterwards become
round,  and disappear  about  the  time that  the ovum  reaches  the

     * Muller's Archiv., 1855.
     f Proceedings of the Royal Society, vol. vii. No. 7, Nov. 23d, 1854. 
ROTATION OF THE YOLK.
855
uterus, except in the case of the rabbit, where Bischoff has observed
that they are lost as soon as it enters the Fallopian tube.
   Soon after the escape of the ovum from  the follicle, and in  some
instances, even before this, the germinal vesicle disappears.  Accord-
ing to  the  observations of some  observers, amongst  whom may be
mentioned  Barry and Wagner, the germinal  vesicle  is the seat  of
cell-formation.*  The nature  of the earliest  changes, however, are
very  obscure.  Eventually,  two cells  result, which are destined  to
undergo subsequent division and subdivision.
   As the ovum passes along the Fallopian  tube, it increases some-
what in size; the yolk becomes of firmer consistence, and shrinks a
little, so as  to leave a cavity between it and the zona pellucida, which
is occupied  with a clear fluid.   The original vitelline membrane itself,
according  to Dr. Barry, disappears by liquefaction.  The external
investing membrane seems to  be derived from the mucous membrane
of the Fallopian tube, and it  is this which at length  becomes deve-
loped into the chorion.

  Dr.  Ransom describes the changes in the yolk immediately resulting from impreg-
nation in the  stickleback's egg, as follows: "About fifteen or twenty minutes after
impregnation, a remarkable and more vivid contraction begins, causing the yolk to
pass through a series of regularly recurring forms.  The contraction begins  on one
side, near the equator, and soon forms a circular constriction, which gives the yolk
the figure of a dumb-bell, the longer  axis of which is the polar axis of the egg.  The
constriction travels towards the germinal pole, and next produces a flask-shaped figure;
this is at length lost by the constriction passing on, and the round form is regained in
about a minute.  This wave reappears, and travels forward again, without any dis-
tinct period of rest;  and I have seen  these movements continue for forty-five minutes,
though towards the latter part of this period they are less distinct and more  limited
in extent.  The germinal mass itself, during these contractions, which  strongly re-
semble the peristaltic movements of the intestine, undergoes changes in form, and has
increased in bulk and distinctness.   These movements are unaffected by weak galvanic
currents.  Cleavage begins in about two hours after impregnation: no embryonic cell
was observed  before it began, nor in  any of the cleavage masses."

   Rotation of the Yolk.—At  a very early period after impregnation,
Bischoff has observed, in the ovum of the  rabbit, guinea-pig, and
some other animals, the very interesting phenomenon  of the rotation
of the yolk.   The movements were of  a regular rotatory character,
and were  produced by the  active vibration  of exceedingly delicate
cilia, which had become  developed upon  the surface  of  the  yolk.
This interesting  movement may be observed in the ova of  frogs and
other animals.    It can always be seen in those of the  common water-
snail (Limnceus  stagnalis), and forms a most  interesting object fur
observation.
   Cleavage of  the  Yolk.—Soon after the  ovum has become impreg-
nated,  and  the germinal  vesicle  has disappeared, the yolk  of the
mammalian animal divides into two  large  cells, and  each of  these
again subdivides into two, so  that the yolk mass now  consists of four
cells which soon become sixteen  in number; these  sixteen, thirty-
two ; and so on, until at last  the  yolk consists of  an aggregation ot

   * T  Muller has shown that in Entochoncha mvrabilis (one of  the  mollusca), the ger-
minal'vesicle  does not disappear, but forms the origin of the  embryonic cell in  the
centre of the yolk. 
856
GENERATION.
spherical  cell-like  bodies.   Each  one of  these, in the mammalian
ovum, is about the l-2000th  of an inch in diameter, and consists of
a central  light  portion, and  an external dark part.   The  external
part, which is composed entirely of  yolk granules, is not covered by
an investing membrane, but the yolk granules seem to be simply ag-
gregated round the central clear vesicle, which, when  set free, looks
very like an oil-globule.   According to Bischoff, this  vesicle  cannot
be looked upon in  the light of a nucleated embryonic cell.    It is pro-
bably more  correctly  considered  as a  nucleus,  around which  yolk
granules have become attracted.
   The process of cleavage of  the yolk is  very easily observed in the
eggs of the batrachia (frogs,  newts, etc.), in which animals the  change
may be  watched  from day to day.   The division of the  yolk has
been  also very carefully investigated in  the ova of certain entozoa,
in different species of which  two distinct modes of division have been
demonstrated.

   Kolliker found in the ova of certain species of Ascaris (nigrovenosa, acuminata, and
succisa), that after the disappearance of the germinal vesicle, a  new nucleated cell
appeared in the centre of the yolk, and  in  a short time two  such  cells manifested
themselves.  Round each one of these cells portions of yolk-mass collected, so that
soon the entire yolk was divided into two parts, in the centre of each of which a nucle-

                                  Fig. 269.
 Cleavage of the yolk in Ascaris nigrovenosa and acuminata, showing successive steps of the pro-
cess of yolk-cleavage. The three figures to the left are after KbUiker, the two others after Bagge.

ated  cell was situated.  Each of these cells again subdivides, and corresponding por-
tions of the  yolk surround the  cells resulting from the original subdivision.  This
process continues to be repeated until at last the individual cells cannot be distinguished
and a granular mass results, from which the  young worm is gradually evolved.  The
division of the yolk appears to result from an attraction existing between its particles
and the cells, which  divide previous to the subdivision of the yolk-mass.
   In the cephalopoda, only a portion of the yolk undergoes subdivision,  the remainder
Berving for the  nutrition of the  embryo during incubation ; hence the division into
germ-yolk  and food-yolk.  Amongst the vertebrata, this type is followed in the class
of fishes and birds, and in many reptiles.
   In the development of  the ovum of ascaris dentata, Kolliker has found that a totally
different process occurs.  In this  entozoon, the first embryonic cell is developed in
the centre of the yolk after the disappearance of the germinal vesicle, and grows at
the expense  of the yolk  substance, instead of causing the latter to collect around it.
This cell  divides into two, which appropriate nutriment in the same manner; and
further division and subdivision occurs,  until at last the yolk entirely disappears, and
its place is occupied by a number of cells, resulting from the division of the primary
 cell, and the absorption of the yolk-mass by the subsequent cells.
   Among the invertebrata, therefore, we have seen  three distinct types upon which
 the  division and subdivision of the yolk occurs ; but in all we notice the disappearance
 of the germinal vesicle, and the formation of a new " embryonic" cell, by the division
 of which  a large number of cells is at length produced, giving the ovum the appear-
 ance of being composed of a granular mass, from which the embryo is at length formed. 
GERMINAL MEMBRANE.
857
  In the mammalia, it is the first of these three modes which is followed.  The entire
yolk divides, its particles collecting themselves round cells resulting from the division
of the embryo-cell, until the yolk-membrane appears to be entirely occupied by granu-
lar contents;  in this stage it is often termed the " mulberry mass."
 Multiplication of cells in the yolk.  The first four figures are ova of Ascaris dentata; the remain-
der, of CucuUanus elegans.  After Kolliker.

   Formation  of Blastodermic  Vesicle, or  Germinal Membrane.^—
About the time that the ovum reaches the uterus, the  segmentation
is  complete, and in  its  general  appearance  it much resembles the
ovarian ovum ;  but according to Bischoff, upon careful examination,
it  is  found  that the apparently granular mass is really aggregated
into  minute spherical  masses,  in the centre  of  each  of  which  is
situated a clear vesicle.   Soon each of these  collections of  granules
becomes surrounded with an investing membrane, so that  cells are

                                Fig. 271.
 Ovum from the ovary of the Guinea-pig, surrounded by the membrana granulosa, through wl
the zona pellucida is distinguished. 
858
GENERATION.
                            Fig. 271.

Earliest changes in the mammalian ovum, consequent upon impregnation.
  A perfectly mature ovum from the ovary, showing the spindle-
i-hape which the cells of the discus proligerus have assumed.
  The same ovum with the
cells of the discus proligerus
removed.  The germinal ve-
sicle has disappeared.
  An ovum from the upper third of the
ovary.  The yolk does not completely
fill the cavity of the zona pellucida. Be-
tween it and the zona is seen a  clear
transparent body, distinct from it.  Ro-
tation of the yolk was visible in this
ovum.
  The yolk divided into four portions.
This ovum was taken from the lower
third of the ovary.
  An ovum from the middle of the ovary.
The yolk is divided into two masses.  Two
clear vesicles are seen between it and the
zona.  A spermatozoon  is observed upon
the zona pellucida.
  An ovum from the upper part of the
uterus, four days old.  The segmenta-
tion  of  the yolk has  proceeded stiU
further. 
FORMATION OF DECIDUA.                  859

        Fig. 271.
 An ovum also from the upper part of         An ovum from the upper part of the
the uterus, showing the further subdi-        uterus, on the sixth day. The yolk-
vision of the yolk ; but the separate        masses have become incorporated into
portions are beginning to become incor-        a single mass, which does not entirely
porated.                             occupy the cavity of the zona pellucida.
  All the ova delineated in Fig. 271 have been copied from Bischoff's beautiful Memoir on the De-
velopment of the Guinea-pig.  Giessen, 1852.

formed, the nuclei of which  are  represented by the  clear  central
vesicle.  The more peripheral cells are first formed, and these from
mutual pressure assume  a pentagonal or hexagonal form ; they be-
come flattened,  and united together at their margins, like pavement
epithelium.   The same  process takes  place in the interior of the
yolk-mass, and as the cells are formed they pass towards the surface,
and thus the thickness of the layer first produced becomes increased.
A clear fluid only occupies the central part of the yolk.   Thus, after
the termination of the cleavage process, a membrane composed of
cells is formed within the zona pellucida, which Bischoff has  termed
the "blastodermic vesicle."   Soon after the formation of this mem-
brane, but not  until it has increased in thickness by the  addition of
new cells upon  its inner  surface,  formed from the contained yolk-
mass, an opaque roundish  spot, consisting of cells and nuclei, makes
its appearance at one spot.  It is  in this space, or " area germinativa,"
that the  first traces of the embryo appear; and it is developed upon
the surface of the " germinal membrane," or " blastodermic^ vesicle,"
being covered only by the zona  pellucida.   As  occurs  in  the bird's
egg, the  germinal membrane soon becomes divided  into two layers:
an external or " serous layer" or animal layer, in which  the brain
and nervous system and different organs of animal life are developed ;
and an internal "mucous"  or vegetative layer, from which  the ali-
mentary canal and organs of vegetative life take their rise.
  At the same time that these  changes are taking place in the in-
terior, the  albuminous layer on the external  surface  of  the ovum
coalesces with the zona pellucida, forming  a single membrane, from
which the  chorion is formed, or,  as maintained by Dr. Barry, the
zona pellucida is first removed, and a completely new investing mem-
brane produced.
  Formation  of Decidua.—Besides the  changes which occur in the
ovum immediately  after conception, which  result in the formation of
the embryo, and the development of  a new covering termed the
chorion upon its external  surface, alterations of another  order are 
860
GENERATION.
taking place in the uterus, by which its  internal surface becomes
adapted for providing nourishment for the embryo in its very early
stages, before it has reached that period of development when it is
enabled to derive its nutriment by direct absorption  from the blood
of the mother.   The change in question consists in the formation of
a soft pulpy tissue, containing cellular elements in great abundance,
over the whole internal  surface of the uterus.  In this soft spongy
Bubstance the ovum becomes  imbedded, and with it the chorion be-
comes intimately connected.   This membrane, in  consequence of its
being thrown off at each parturition, has  been termed the " mem-
brana decidua."
  The decidua was formerly looked upon  as an exudation from the
mucous membrane of the uterus;  but from the observations of Pro-
fessor E. H. Weber and Dr. Sharpey, it has been shown to  consist
of the  much thickened  and  altered  mucous  membrane itself.   It
appears to be composed of glands lined with epithelium, between
which  ramify vessels surrounded by  much soft  pulpy  tissue, com-
posed principally of nucleated cells.   At the time of its formation,
the ordinary ciliated epithelial lining of the  unimpregnated uterus
entirely disappears, and  its cavity soon becomes  filled with  a  fluid
secreted by the  soft and swollen decidua.   The  os uteri is plugged
             v.-
■■ft            £#
 Section of human uterus at commencing pregnancy, showing the glands in the mucous membrane,
and their openings. Twice the natural size. After Weber.

up by a soft, viscid, mucus-like mass, composed of a secretion from
the decidual membrane; but  the  cells  which are found in  it differ
materially  in  character from those immediately surrounding  the
ovum, in being of an elongated form, while  the latter are spherical,
and, according to  Professor Goodsir,  perform the very  important
office of elaborating the nutrient material for the ovum.
  Structure of the Membrana Decidua.—In the  unimpregnated
uterus of the bitch and other animals, and  probably also in that of
the human subject, but more minute,  are situated numerous small
glands, which increase  enormously in size immediately after concep-
tion.  In the human uterus, soon after impregnation, they are seen
as elongated wavy tubes, having a tolerably straight course in their
more superficial part, but much contorted towards their deep aspect,
where they terminate in two or three csecal extremities.    The space
between these tubes contains capillary vessels and numerous cells, to
the increased development and multiplication of which, according to 
DECIDUA REFLEXA.
861
 Uterine glands of the bitch.  Twelve
diameters. 1. Simple glands.  2. Com-
pound glands. After Dr. Sharpey.
Professor Goodsir, the greatly increased thickness of the membrane
is due.   In the mucous  membrane of  the  uterus  of the bitch, Dr.
Sharpey has described two distinct kinds of glands, one simple and
the other compound.   The openings of both these forms of glands
may be readily seen upon  the surface of the mucous membrane; and
they soon increase in dimensions, in  order  to receive the foetal pro-
cesses of  the chorion, which are covered with epithelium, similar to
that lining  the follicle.   Immediately before the large compound
glands  open upon  the  surface, Dr.  Sharpy describes their tube as
forming a dilatation or cell, into which a foetal process of the chorion
is received.  At the bottom of this cell
the duct may be seen; and as it passes
towards the deep surface, it is observed
to form the branched compound gland.
At parturition, the vessels  of course
come away with  the decidual  mem-
brane, as well as the cells just referred
to,  but  the ducts and branching termi-
nations of the glands remain behind.
From this arrangement it  follows that,
in  the  bitch,  the secretion elaborated
from the system  of  the  mother by the
agency of these glands is brought into
close contact with the  vessels  of the
foetus, and afterwards absorbed by them.
   In the human decidua, the openings of the glands may be distinctly
seen, and their epithelial  lining  readily traced.   The  tubes can be
followed  through the membrane;  in  fact, from
numerous observations,  there can  be  no   doubt
that, like the decidual membrane in the bitch, the
human decidua consists really of the altered mu-
cous membrane of the uterus.
   Leydig has seen ciliary motion in the uterine
glands  of the sow.
   Next we have to  consider how  it is, that the
ovum  becomes  covered  with the decidual  mem-
brane.   Dr. W. Hunter looked  upon the decidua
as  a closed  sac, separating the uterine cavity from
the openings  of the  Fallopian tubes.  When the
ovum descended, he supposed that  it  pushed the
decidua, as it were, before it,  and  thus  became
covered in the same manner  that the  viscera are
invested with peritoneum ; and hence, Dr. Hunter
termed that portion of decidua covering the  ovum,
decidua reflexa, while that lining the  uterus was
called decidua vera.   As  the ovum increased in
size, that part of  it towards the Fallopian tube.              .
which of course remained  uncovered by the reflexa, at length received
a covering  which was termed decidua  serotina.
   Decidua Beflexa.—Since the time of Dr. W.  Hunter, much differ-
 Thin section of human
decidua soon after im-
pregnation  had taken
place, showing glands
divided  transversely.
Magnified  twelve  dia-
meters. 1.  Tube  with
epithelial  lining.   2.
Tube  from  which the
epithelium has escaped.
After Dr. Sharpey. 
862
GENERATION.
ence of opinion  has arisen  among anatomists as to the manner in
which the ovum  became covered with decidual membrane.   That his
view was incorrect, follows from the fact which has been ascertained
by subsequent researches—namely, that the  decidua  itself consists
of the altered mucous membrane of the uterus, and therefore, like it,
is continuous with the mucous lining of the Fallopian tubes, and not
stretched  across  the  opening, so as to be pushed forwards by the
ovum in its  descent.  The structure of the  decidua reflexa, as was
pointed out by Goodsir, differs from that of the vera in not contain-
ing many ducts.   It does, however, contain a few, which are derived
from that part of the decidua vera which is continuous with it.
  Dr.  Sharpey considers  the central part of the decidua  reflexa as
formed by a layer of exuded lymph, with which the ovum is covered
upon its entrance into the uterus, and that the decidua vera extends
upwards around it to a point where these two structures become con-
tinuous.   He also offers  the more simple suggestion, that  the ovum
may first become completely imbedded, and then may  carry forward
with it a covering of the membrane  as it  increases in development.
A view which agrees in  the main with Dr. Sharpey's, and which is
probably nearest the truth, is  that  of M. Coste, who  supposes  that
the ovum  becomes partially imbedded  in the decidual membrane and
soft pulpy matter poured  out by its glands.   As the ovum increases
in size, the decidua grows up around  it,  so as ultimately to cover it
completely.
  The two layers  of  decidua above referred to, gradually come in
contact as the ovum increases  in size, until,  towards the end of the
third month, they are incorporated  together and form  one mem-
brane, which becomes thinner as  pregnancy advances, and is ex-
pelled  with the fcetus at the  termination of the period  of gestation.
  The decidua is a structure admirably adapted  for the ovum to be
imbedded  in in the early stages of its existence, and the numerous
glands in its substance seem evidently destined  to elaborate a pabu-
lum fitted  for its nutrition, before its own especial organs are suffi-
ciently advanced in development to select and absorb the materials
for its subsistence.
  The tufts  or villi of the  chorion, each  of which consists of a col-
lection of nucleated cells  within a delicate membrane, are the organs
by  which  this nutriment  is  at  first absorbed, just as the collections
of cells at the terminations of the minute divisions of the root of the
plant absorb  and appropriate nutriment from the soil.  Soon, how-
ever, vessels are prolonged from the foetus into these tufts, and thence-
forward it continues to be nourished from  the vascular system of the
mother;  but the  nutrient matter  is still transmitted  through the
layer of cells covering the vascular maternal surface, as well  as that
covering the foetal tuft.   The precise  nature of this arrangement we
shall have to consider when  discussing the mode of formation of the
placenta.

  Upon the subjects discussed in Chapter XL., the reader is referred to  the following
works and monographs, besides  those mentioned in the notes: Mr. Newport, " On the
Impregnation of the Ovum in  Amphibia," Phil. Trans. 1851-3; Dr. Barry's " Re-
searches in Embryology," Series I. II. III., in Phil. Trans., 1838-40; Dr. Sharpey, 
DEVELOPMENT.
863
" On the Structure and Functions of the Membrana Decidua and the Uterine Glands,"
in Miiller's Embryology, translated by Dr. Baley;  "De Evolut. Strongyli Auric, et
Ascarid. acum. Vivip.," Diss. Inaug. Erlangge, 1841; Bischoff, "Entwickel. des Hun-
deeies;"  Vogt, "Untersuchungen  iiber die Entwickelung  der Geburtshelfer-krote
Solothurn," 1841; Goodsir's "Anatomical and Pathological Observations ;" M. Coste,
"Comptes Rendus," 1847;  Dr. Ransom, "On the Impregnation of the Ovum in the
Stickleback," in the Proceedings of the Royal Society, vol. vii. No. 7, 1854; Leuckart,
"On the Micropyle and Minute Structure of  the Egg-shell in Insects," Miiller's
Archives, 1855.
                        CHAPTER XLI.

ON THE DEVELOPMENT  OF THE EMBRYO — EARLY CHANGES  IN  THE
  BIRD'S OVUM—AREA  PELLUCIDA, AREA GERMINATIVA, AREA VAS-
  CULOSA — SEROUS  AND MUCOUS LAMINA--INVESTING MEMBRANE
  AND  MEMBRANA  INTERMEDIA  OF REICHERT—CHANGES  IN  THE
  MAMMALIAN OVUM—PRIMITIVE  STREAK—FORMATION OF DORSAL
  AND   VENTRAL   LAMIN2E — FORMATION  OF  THE   AMNION —
  BRANCHIAL FISSURES AND ARCHES--HEART AND LARGE  ARTE-
  RIES—ALLANTOIS—DEVELOPMENT  OF THE HUMAN  EMBRYO.

  In the last chapter we described  the  earliest changes  resulting
from impregnation, and  traced them up to the formation of  the ger-
minal membrane, and the first appearance of the embryo.  We have
now to consider the manner in which the  development of the embryo
takes place, and the mode in which the different organs are  evolved.
It will be  most convenient  to  describe, as briefly as  possible, the
earliest changes occurring in the bird's egg, in the first instance, and
then to consider the development of  the mammalian ovum, and that
of the human subject.
  Early Changes in the Bird's Ovum.—In considering the nature
of the earliest changes  in the egg, resulting from impregnation, but
which are dependent for their commencement and continuance  upon
a temperature varying  from 95° to 104° F., we must  premise that
the  yolk of the bird's  egg consists of two distinct  portions, one
which undergoes segmentation, and alone takes part in the formation
of the embryo—the germ-yolk ; the other, and by far the larger por-
tion, does not undergo segmentation, and takes no part  in the forma-
tion of  the germ, but provides the pabulum for  its  development and
nutrition, whence it is termed the food-yolk.
  Area Pellucida, Area Germinativa, and Area Vasculosa.—A. few
hours after the egg has been exposed to  a hatching heat, it will  be
found that the germ has become less adherent to the vitelline mem-
brane.   It has assumed a more membranous appearance; and  about
the sixth or seventh hour, a clear space may be discerned in its centre.
This increases gradually, until it is about a line in  diameter.   It is
called the area pellucida.   The  darker and more granular  part, ex-
ternal to  the area  pellucida, is the area germinativa, in which may 
864
DEVELOPMENT.
be observed a darker portion, which is the future  area vasculosa, so
called, because vessels are first observed in this situation.  The germi-
nal membrane is composed entirely of cells, which result from  the
original process of cleavage (page 859).  These cells increase at its
margin; and in this way the germinal membrane  gradually extends
itself so as to invest the entire yolk.
   Serous  and Mucous Laminse.—At an early period, the germinal
membrane manifests a tendency to split into two layers.  These  are
termed lamince.   The upper one, which, in  its extent, corresponds to
the area pellucida, is the  serous laminse.   The lower one, which is
more extensive, and which extends beyond the vascular area, is called
the mucous laminse
   Reichert, however, in his beautiful investigations upon  the deve-
lopment of the chick, has described the formation  of the layers from
which  the  different organs  are evolved  in  a somewhat different
manner.
   The "Investing Membrane," and "Membrana Intermedia," of
Reichert.—The most superficial layer of cells of which the germinal
membrane is composed, which is usually known as the " serous layer,"
has been termed by Reichert the investing membrane.  It extends, at
its circumference, between the yolk and the vitellary membrane by the
apposition of new cells of the yolk to its  periphery, and is formed
independently of the vascular system. The rudiments of the nervous
system are first  seen in the form of  a line  (primitive streak) imme-
diately beneath the investing membrane, and are  developed  from a
stratum of cells which has separated itself from the surface  of  the
yolk.  Immediately beneath this is another layer  of cells which  has
been termed the  mucous layer of the germinal membrane, also  the
vascular layer;  but Reichert has well described  it  under the term
membrana intermedia.   It is beneath the central organs of the nerv-
ous system, and in contact with the chorda dorsalis.  Lying between
the nervous centres on  the one hand, and the mucous membrane on
the other,  and extending beyond the limits of the  area pellucida, the
membrana intermedia gives origin to the  vertebral, cutaneous, and
vascular systems, and to the digestive system with the exception of
its mucous membrane.   In the development of the higher vertebrate
animals, according to Dr. Reichert, the membrana intermedia per-
forms a most important part.
  About the sixteenth hour, between the external and internal layers
of the  germinal  membrane  a new  deposition of cells takes place,
from which  the  first traces of vessels are produced.  This  is  the
middle layer of the germinal membrane, commonly known  as  the
vascular layer.   The vessels are not formed, in the first place, close to
the embryo, but  at some distance from it, outside  the area pellucida,
so that now the area  pellucida is surrounded by  the area  vascu-
losa ; and  this again by the area vitellina.  As the vessels increase in
number and size, they spread  outwards  over the  area vitellina, and
inwards over the area pellucida, until they join the large trunks con-
nected  with the  heart.   A little earlier than this, about the four-
teenth  hour, in the central  part  of  the long axis of the clear oval 
FIRST TRACE OF EMBRYO.
865
 Portion of germinal membrane about the
sixteenth hour of incubation,  a. Germinal
membrane. 6. Area vasculosa.  e. Area pellu-
cida. d. Nota primitiva or embryo.
area pellucida, which lies in the transverse axis of  the egg, appears
a line, thicker  at one  extremity than  the  other.   This is the first
trace  of  the embryo, and is called  the  primitive streak  or the nota
primitiva.
  About the third  day of incubation, on each  side of the primitive
streak,   appear  two  ridges  or
crests, which are termed laminse               Fig. 275.
dorsales.  These gradually  arch
over,  and at  length inclose the
brain and cord.   The chorda dor-
salis  occupies  a position  under-
neath the spinal cord, and appears
as a thin gelatinous thread, which
corresponds to  the axis of the
bodies of   the  vertebrae, which
latter, however, are not formed
from  the chorda dorsalis, but are
developed from a  double row of
four-sided  white spots,  or  verte-
bral plates, arranged  symmetri-
cally on each side of the central
chorda dorsalis.  Passing down-
wards from  the dorsal laminse, on
 each side  are the  ventral  laminse, which tend  to  inclose a space
 below the chorda dorsalis, like  that inclosed by the dorsal laminse
 above it.   The former  contains the large vessel of the  trunk  (fig.
 277); the  latter the central  organs of the  nervous system.   In
 this way are produced  the  haemal arch and the neural  arch of the
 vertebrae.
   Soon  the embryo, and that  portion  of the  germinal  membrane
 immediately connected with  it, become somewhat raised ;  the embryo
 itself taking the form of a boat with its concave surface downwards.
 This  is the first appearance of a  visceral  cavity, bounded by the
 ventral laminse, in which the ribs and  the  transverse processes  of
 the vertebras are formed.
   That part of the most superficial  layer of the germinal  membrane,
 or serous lamina, immediately surrounding the  embryo, forms a  pro-
 minent  fold which soon rises  above the  surface.  According  to
 Reichert, however, the fold is formed from the most  superficial layer
 of the membrana intermedia, and is only covered  by the investing
 membrane.   Each fold  approaches that on the opposite side, until,
 by their approximation and communication, a shut sac is formed, into
 which fluid is  poured.   In  this  fluid, the embryo floats.   Its open
 ventral surface gradually becomes closed, until  at last it is connected
 with  the yolk  only by means  of  a very narrow  pedicle or  cord
 (umbilical cord), which  consists of  a narrow tube passing from the
 intestine to the yolk, with certain vascular trunks, through which the
 nutritive matter absorbed by the vessels ramifying upon  the surface
 of the yolk is carried to the embryo.  Of this  attenuated cord  con- 
866
DEVELOPMENT.
 necting the embryo with the yolk sac or umbilical vesicle we shall
 speak at some length  hereafter.   Thus  is formed  the  amnion, to
 which we shall have to  allude more particularly in Chapter XLIII.
   Such are some  of the most important  changes occurring  during
 the earliest period of incubation in the  chick.   We shall  now con-
 sider the  nature of  those which take place in the mammalian ovum.

               Changes in the Mammalian Ovum.

   The essential changes which manifest themselves  in the early
 period of the development of the  mammalian embryo  are very
 similar to those which we have briefly described  as occurring in the
 bird's egg; but in  consequence of the small  amount of yolk in  the
 former compared with the latter, and therefore the greater depend-
 ence  of the embryo for its  nutrition upon external sources,  certain
 differences are observed in the development of the mammalian ovum.
   It  has  been already stated (p. 857) that by the time the mamma-
 lian ovum has reached  the uterus,  the process of segmentation is
 complete.  It is  also paler and more transparent.   The  germinal
 vesicle had disappeared previous to segmentation ; but  whether its
 contents  become mixed up with the substance of the yolk,  or new
 cell-formations primarily result  from it, has not yet been conclusively
 determined.
   By the aggregation of cells upon the surface of the yolk, a  sort of
 membrane, composed of pentagonal cells with nuclei is formed within
 the zona  pellucida,  or  yolk-membrane.   This is called  the  blasto-
 dermic vesicle, and in its mode of formation  nearly corresponds to
 the germinal membrane of the bird's egg.
   The chorion, or outermost membrane investing the ovum, is formed
 by the gradual coalescence  of the zona pellucida, and  the  layer of
 albuminous material  with which it is covered.   The chorion is at
 first smooth, but villi are subsequently developed all over  its surface.
 Beneath the chorion is the blastodermic vesicle, which  gradually in-
 creases in thickness by the growth of new cells upon its internal
 surface.
   In  consequence  of the great difficulty experienced  in procuring
 human ova at a very early  period in a perfectly normal state, and
 in sufficient  number, physiologists have  been compelled  to make
 direct  observations  upon the lower animals, and to  assume  that a
 series of  changes precisely similar takes place in the  human  ovum,
 an inference  which has  been of late years  fully justified by direct
 observation.  In discussing this part of our subject, we shall, there-
fore, infer that the early embryonic changes occur in a similar order,
 and are of the same essential character in all mammalia, except, of
 course, with reference to the precise period at which they  take place,
which necessarily differs  in various  animals, according to the dura-
tion of pregnancy.   For much  that we know of  the development of
the mammalian ovum, we are indebted to  the beautiful researches of
Bischoff upon the ova of the dog, rabbit,  guinea-pig, and  deer.
  Primitive Streak.—At a  period varying from  the twelfth  to the 
VENTRAL LAMINA.
867
sixteenth  day, the dog's ovum  assumes a  more  oval  form.   It is
about three lines in length, and about a line and a half in its  short
diameter.   Its external  surface is as yet perfectly smooth, for  none
of the tufts or villosities of the chorion are developed.   The central
clear space (area pellucida or germinativa) is  seen to be surrounded
by a darker circle,  which eventually becomes the vascular area.
  In the centre of  the clear space a line is  soon observed.   This is
the first trace of the embryo, the primitive streak, which appears  in
the form  of a straight  white  line, or  very shallow groove.  It lies
across the  short axis of  the ovum, and therefore occupies a position
precisely similar to the embryo chick.
   The primitive streak is formed  in the serous or  animal layer of
the germinal membrane, beneath  the  investing membrane of Rei-
chert.   Bischoff has shown, that in the mammalian ovum the germi-
nal membrane becomes  divided into  two laminae, as in the chick.
 Portion of the germinal membrane of the bitch's ovum, showing the area pellucida and first traces
of the embryo, after Bischoff.  A. Germinal membrane.  B. Area vasculosa. C. Area pellucida.  D.
Laminae dorsales. E. Primitive trace.  Magnified ten diameters

The external lamina is the serous or animal layer, and the internal
one is the mucous or vegetative layer.  The middle layer, or mem-
brana intermedia, described  by Reichert, has already been alluded
to in page 864, but, according to Bischoff, is not to be detected in the
mammalian  ovum.
  Formation of Dorsal and  Ventral Laminse.—In a short  time the
cephalic  extremity becomes  enlarged, and the  entire embryo of a
guitar-shape in its general outline.   As  soon as the primitive groove
is formed two oval folds are seen to rise up on each side of it from
the serous laminae (d, fig. 276).    These are the laminse dorsales,
Which gradually approximate ; and the groove between them becomes
- A


- B



--- C


— ii


- £ 
868
DEVELOPMENT.
converted into  a canal  which  contains the  central  organs  of  the
nervous system.
  Reichert supposes  that  the laminae dorsales  actually take part in
the formation of the central  parts  of the nervous system; but Bis-
choff considers  that they represent  the  dorsal portion of the embryo,
and that the nervous  system is  developed from  their lower and inner
part only.  About  this time a  few small square-shaped plates make
their appearance in the central portion of each dorsal lamina.   These
 Plan showing the mode of development of the dorsal and ventral laminae,  a. Serous or animal
layer; e. Mucous or vegetative layer ; b. Chorda dorsalis ;  c. Ventral laminae, arching downwards
to inclose the intestines, the rudiment of which is shown at d ; /. Dorsal laminae arching over to
convert the groove into a canal for the spinal cord ; g. aorta.
plates are the first rudiments of the vertebras.  The soft chorda dor-
salis, a structure which exists permanently in the lower cartilaginous
                                            fishes,   appears   subse-
                 Fig- 278.                    quently between the rows
                                            of plates, but  this  is by
                                            no  means so   distinctly
                                            marked  in  the  mamma-
                                            lian ovum as it is  in the
                                            embryo frog or fish, while
                                            in  the  lowest  cartilagi-
                                            nous fishes, as  the  myx-
                                            ine,  the  lamprey,  and
                                            others,  it  is   persistent.
                                            The two plates  of  oppo-
                                            site sides  gradually  ap-
                                            proximate, and ultimately
                                            coalesce,  including  be-
                                            tween  them a portion of
                                            the chorda dorsalis, a tem-
                                            porary  structure,  which
                                            disappears entirely with-
                                            without   being   trans-
                                            formed  into   any  more
                                            permanent texture.
                                              The laminse viscerates,
                                            or ventral  laminae,  are
                                            also   developed  in  the
                                            serous  layer,  and   con-
tinuous with  the laminae dorsales.   They project  downwards, and
ultimately inclose the anterior portion of the embryo.
 Germinal membrane with rudiments of embryo of the dog.
After Bischoff.  A. Primitive groove, not closed.  B. The
three dilatations corresponding to the three vesicles of the
cerebrum. C. Space at lower part of groove or sinus rliom-
boidalis. The streak at the bottom of the groove is the chorda
dorsalis. 
FORMATION OF THE AMNION.
869
  In the anterior dilated extremity of the embryo are developed three
vesicles, from which  the different parts of the brain are ultimately
evolved.
  Formation of the Amnion.—The upper layer of the serous lamina
becomes raised in the form of a convex ridge, which extends entirely
round  the circumference of the embryo.  This ridge, consisting, of
course, of two layers of serous lamina, rises up gradually, and  the
two portions from  opposite sides approximate above the dorsal sur-
face of the  embryo.   The parts of the fold  corresponding  to  the
anterior and posterior  extremities of the embryo grow faster than
other portions, and soon two considerable reduplications are formed.
These  are called the cephalic and  caudal involucra.   The embryo is
gradually inclosed  by these two layers, which  meet  over its  dorsal
surface, and at last coalesce.   Thus is formed the amnion ; and the
interval between the inner layer and the embryo  is the amniotic
cavity, which contains a fluid, the liquor  amnii.   The  two layers,
after some time, become united into one, except at the  points where
they are separated by the allantois and umbilical vesicle, forming the
single  amniotic  membrane, which lies within  the chorion.  The outer
layer,  however, is  separated from the inner surface  of  the chorion
by  a  quantity  of  viscid albuminous matter, which  is  subsequently
absorbed.
  The mode of formation of the amnion in mammalian ova is, there-
fore, precisely similar to that of the chick,  according to Von Baer.
Reichert,  however, considers that it is formed in a somewhat differ-
ent manner to that above described.*
Fig. 279.
 Plans showing manner of formation of amnion, allantois, and umbilical vesicle,  a. Chorion with
villi most abundant in that part beneath which the aUantois is seen in figure 280; this portion ulti-
mately becomes the placenta,  b. Space between the two layers of the amnion  e  Amniotic cavity.
d. Situation of intestine, showing its connection with the umbilical vesicle, e. Umbilical vesicle. /.
Situation of heart and vessels,  g.  Allantois.

   In mammalia, the formation of the amnion occurs at a very early
period, usually within twenty-four hours after the  first appearance of

the primitive trace.                   #
   About the twentieth day the  ovum is  about  ten, and the embryo

           * Muller's Physiology, translated by Dr. Baly, p. Voo'2. 
870
DEVELOPMENT
is between three and four lines in length.  The villi of the chorion
are beginning to make their appearance, and gradually extend them-
selves round the ovum.  That portion, however, which is immediately
beneath the embryo is the last part of the surface upon which villi
appear, while the two ends of the ovum always remain smooth and
uncovered with villi.
  By this time, with  the exception of  their posterior portion, the
laminae dorsales have  coalesced,  and the  vertebral plates have in-
creased in number.  The position of the  eye and ear can be deter-
mined, and the anterior surface of the body is being gradually closed
in by the convergence of the ventral laminae which spring from the
under part of the dorsal laminae.   At length the body of the embryo
appears entirely pinched off  as it were, and is only connected with
the yolk-sac  or umbilical vesicle by a narrow constricted portion, the
omphalo-enteric duct.
   Branchial Fissures and Arches.—At this period, three branchial
fissures and three visceral arches may be detected.
   The term branchial arch is a  bad one, since it  conveys the idea
                 that, at a certain period, branchiae are developed in
                 the higher vertebrata, which is not the case.   The
                  only structures representing  the  branchial vessels
                  of fishes are branches which unite to form the de-
                  scending aorta.  In fishes, the arches become per-
                  manent, and are surmounted  by branchial laminse.
                  They are five  in  number;  at a very early period
                  there are six, but one is  not further developed.  In
                  the amphibia a similar process takes place, but here
                  the branchiae waste away when the animal assumes
                  its adult form.  Usually only two, very rarely four,
                  arches remain  in reptiles ; and in birds, mammalia,
                  and man, only one is persistent.
  -visceral or branchial   Heart and large Arteries.—About this time also,
X^Bischoff^aTrarn- the heart and  large vessels are formed.  The heart
 6. eyes; e, d. right and appears first in the form  of a narrow elongated
 left auricles; e, f. right  FT     .    .             .                 &
 and left  ventricles; g. tube, which is a  little  twisted, and gradually be-
 a?chesdlvid,"$f '3,°™lm- comes  completely bent  upon itself.  The develop-
 brln°chtiigarCuesC.eral  or ment  of the heart may be watched in the  chick
                  from the beginning of the second day of  incubation.
 It appears between the  mucous  and serous laminae in the form of a
 sac, terminating in two  or three  branches, the future venous trunks.
 At this early period  even rhythmical motions  may be observed, but
 the fluid in its interior is at this time nearly colourless.  The large
 vascular  trunk immediately after its origin from the ventricle divides
 into four vascular arches, which unite again to form the aorta.   This
 vessel, as it passes down close to the spine, again divides, and gives
 off transverse branches;  some of which, the arteriae omphalo-mesen-
 tericae, lying upon the duct  of the  same name, are conducted to the
 yolk-membrane, upon the surface  of which  they are spread out.
 These vessels absorb the nutrient constituents of the yolk, and carry
 tthem to the system of the foetus.  With their corresponding veins
 
OF THE HUMAN EMBRYO.
871
they form a network over the umbilical vesicle.   Their arrangement
will be more fully described in Chapter XLIIL, on the development
of the membranes of the foetus.
  Allantois.—The allantois is first observed as a little solid eminence
composed of cells upon  the anterior surface of the caudal extremity
of the embryo (figs. 279, 280,  g).   A cavity is soon formed, which
is continuous at one period with the lower part of the intestine.
   The allantois grows very rapidly, and in ruminants soon surrounds
the entire foetus, its outer surface being in close  contact with the
chorion; but in rodent animals, and in man, its chief office is pro-
bably that of conducting the vessels of the foetus to the chorion.
             Development of the Human Embryo.

  It was formerly supposed that man, in his development, passed
through various successive stages, each of which was said to have its
permanent representative among the lower animals; but a doctrine
so obviously untrue  has  long  since  ceased to have any supporters.
Von Baer showed the fallacy of such a statement; but at the same
time proved that up to a certain period of development, the changes
occurring in the human embryo were precisely similar to those which
take place in the development of all other vertebrate animals; that,
for instance, up  to a certain  period of  its  existence, we should be
unable to distinguish the embryo of man,  or one of the higher verte-
brata, from that of a reptile  or a fish.   All seem to be developed
upon one general plan.   The  organs are  evolved in the same order,
and the organic functions  in  the  manner of their  performance
are precisely analogous.   After this point  has been reached, how-
ever, the distinctive  characters are well marked, and then it is very
easy to say whether the embryo  is to assume  permanently the  con-
dition of a fish, reptile, bird, or mammal.
  One of the youngest human ova which has been  examined, is  de-
scribed by Mr. Wharton Jones, and was aborted in the third or fourth
week after  impregnation,  It  was about  the size of a pea, and was
probably detached at a somewhat earlier period.  Villi were seen on
one side only of the chorion.   At one end of the ovum, lying in the
midst of a gelatinous material, was the germinal vesicle, but the em-
bryo was not yet visible upon it.
  Dr.  Allen  Thomson has examined two human ova at a  somewhat
later period.   One was a quarter of an inch, and the other half an
inch, in  diameter.  The embryo was about one line in length  (fig.
282).    It lay nearly flat upon the yolk-sac,  no constriction being as
yet formed.  The dorsal laminae were distinct, and had not yet united
together.  There was neither allantois nor amnion.  This ovum was
examined about fifteen days after conception.   >
  MM Pockels and Coste have had an opportunity of examining an
ovum about this period, in which  the umbilical vesicle and allantois
werT fleer'very distinctly.  The embryo  lay in  the amniotic fluid;
but the allantois had not yet become connected with the inner  sur- 
872
DEVELOPMENT
face of the chorion.   In another embryo described by Dr.  Allen
Thomson, about five or six weeks after conception, the allantois was
                                 attached to the chorion, and there
                                 existed  an umbilical  cord,  which
                                 was not yet inclosed in its sheath
                                 formed by the amnion.  It was the
                                 eighth of an inch in length.   The
                                 heart projected in the form  of a
                                 looped  vessel  from  the  anterior
                                 aspect of the body.  The intestine
                                 was  straight and opened  into the
                                 yolk-sac, and  the opening of the
                                 anus  was not  yet formed.   The
                                 umbilical  vesicle  was becoming
                                 narrower near  the embryo.  Two
                                 branchial   fissures were  present.
                                 Wagner and Muller have examined
                                 ova a little further advanced.  The
                                 embryo examined  by the latter ob-
server was two  and  a  half lines in length, and  the  amnion  was
seen closely applied to it.  There were three pairs of branchial fis-
sures and arches.  The age of this  embryo may be stated with tole-
rable certainty to be about twenty-five days.
   Several human ova have been  subjected to careful examination by
different observers, between three and four weeks old, which may be
considered to be in  a normal state, and not modified by the occur-
rence of any morbid  change.   At this time,  the  ovum is about seven
lines in length, and the embryo not more than two.  It is surrounded
by an  amnion which adheres to it  pretty closely.   The chorion  is
already covered with small villi.   Between the chorion  and amnion
is a considerable quantity of a viscid albuminous  material.   The
embryo is curved.   The anterior cerebral vesicles are well  marked,
and immediately behind  them are the very large corpora quadrige-
mina.   The positions of the ophthalmic  and auditory  vesicles are
indicated.  Three or four visceral arches are seen with the branchial
fissures between them.   The heart is not yet fully formed,  and pro-
jects  from the anterior surface  of the body as  a  bent tube.   The
anterior and posterior extremities exist in  the form of curved flattish
appendages.  The abdomen is completely open, and the amnion  is
reflected  over the anterior and  posterior extremity of  the  embryo,
to form the cephalic and caudal  involucra.
   The heart is large, and consists of a  simple auricle and ventricle.
Behind the  heart is seen the liver, beneath which is  situated the
intestine, attached by its  mesentery.   The  umbilical  vesicle is  as
large as the embryo, and it is connected with the intestine by a long
pedicle, the  ductus omphalo-entericus.   The vesicle itself  is found
lying between the chorion and  amnion (figs. 280, 294).  The duct,
with the  vessels which  accompany it,  and  the  allantois, constitute
the umbilical cord, enveloped by the amnion, which membrane forms
a tube inclosing  these structures.
Fig. 282.
 A human ovum described and figured by Dr.
Allen Thomson, about fifteen days after con-
ception, magnified ten diameters,  a. The open
vertebral canal, bounded by the laminae dor-
sales.  b.  Folds of the intestinal groove, c. Po-
sition of the heart,  d. Yolk-sac.  e. Apiece of
membrane perhaps connected with the forma-
tion of the chorion. 
OF THE HUMAN EMBRYO.


           Fig. 283.
873
  Human fetus between the twenty-fifth and twenty-eighth days, to show the relative position of
the several organs,  a. Chorion with tufts developed over the greater part of its surface,  b. Am-
nion- between the situation of the two 6's  the amnion forms a sheath which invests the structures
which compose the umbilical cord.  c. Position of Allantois with the vessels upon it which ramify in
that part of the chorion where the placenta is developed,   d. Umbilical vesicle with  its narrow
pedicle and trunks of omphalo-mesenteric vessels spread out upon its surface,  e. The point at which
it opens into the intestine.  /.  Corpora Wolfflana.  g.  Liver,  h. Heart,  i. Rudiments of anterior ;
and k rudimentary posterior extremities.  I. Branchial fissures and visceral arches,  m.  Cavities of
nose and mouth not yet separated, n. Rudimentary eye.  o. Rudiments of ear.   After Coste. 
874
DEVELOPMENT
  The allantois is seen  as  a  large  and well-defined vesicle, which
extends to the inner surface of the chorion, to which it is attached.
On  each side of the  mesentery, close to the spine, are situated the
large Wolffian bodies.
  About the fourth  week, there are three branchial fissures  and
arches behind the lower jaw.   The divisions of the vertebrae are very
distinctly marked, and, in consequence of the curvature of the em-
bryo, the coccyx and forehead are brought very close together.
  Up to this period, the development of the human embryo is very
similar to that of other vertebrate animals.
  The umbilical vesicle, about four  or five lines in  diameter, dimi-
nishes considerably in size during the third month.
  The viscid albuminous material between the chorion and amnion gra-
dually becomes absorbed, in consequence of  which these two mem-
branes approach each other, and almost come into contact, but they still
remain separated by a thin membrane, the tunica media of Bischoff.
  The villi of the chorion  increase very much in that portion of its
surface situated over the allantois, where the placenta is to be formed.
They are not absorbed  from other parts, but the interspaces between
them gradually become much greater;  and as the ovum increases in
size, the tufts appear to be almost limited to the position of the pla-
centa, although, with  care, they may be seen in other parts  of the
surface.
  The cord  gradually increases in length, and the quantity of liquor
amnii in which  the ovum floats becomes greater.-
  Ossification commences  towards the end of the  second  month,
when the foetus is about an inch in length.  The septum of the heart
begins to be formed, and the aortic arches diminish in number to two,
which  unite behind to form the descending aorta.  One of these
arches becomes the pulmonary artery.  The  development of the kid-
neys, ovaries, testes,  and  external  generative  organs  commences.
The bladder is formed somewhat later by the pinching  off of a por-
tion of the urachus, a narrow  tube, which is all that remains  of the
allantois. The cavities of the mouth and nose are  not yet separate;
but the divisions between the fingers  and toes are commencing to be
marked.
  During the third month, the embryo increases from  one inch to
about two and a half or three  inches in  length.  In the fourth, it
increases another inch;  but  during  the  fifth  month, it grows so
rapidly as  to  attain the  length of  twelve  inches.  Fat  is  formed
about this time, and the nails are developed.   The first movements
of the foetus felt by the mother, and termed quickening, usually take
place between  the fourth and fifth  month.  The  whole surface  is
covered  with lanugo or soft down.   The very slow growth  of the
foetus during the time when the organs are being evolved and it  is
assuming its distinctive characters, contrasts very remarkably with
its rapid increase in size as soon as the various organs have attained
a definite form.   The process of evolution is a complicated one, and
obviously requires much time for the occurrence  of the necessary
transitional  changes.   The  process of growth is a simple one, and 
OF THE SPINAL COLUMN.
875
consists merely of the appropriation of new material by structures
already formed.   The further development of the different textures
gradually takes place, and the various  organs assume  their perma-
nent character, until, about the seventh month, the foetus has attained
a length  of sixteen  inches or more, and, under favourable  circum-
stances, its life may be  preserved if it be born at this  early period.
The testicles descend about the eighth month.
  By the end of the ninth month the foetus has attained the length
of eighteen or twenty inches.   The  head is  covered with hair, and
the skin becomes invested with a soft pultaceous substance, the vernix
caseosa,  which  consists of cells  of epidermis, with  a  considerable
quantity of oily material.   The membrana pupillaris  is  absorbed.
During the latter months of pregnancy, the child lies in utero, with
its head downwards,  the position in which birth takes place.

  The student is referred, for further information upon the subjects  treated of in the
present chapter, to the works enumerated at the end of Chapter XL., and to  the fol-
lowing: Reichert's Observations  on the Development of the Chick, in Miiller's Phy-
siology, translated by Dr. Baly;  Bischoff's Monographs on the Development of the
Dog and Guinea-pig;  De Graaf, Opera Omnia ; Von Baer's Entwickelungs-geschichte;
Dr. Thomson, in the Edinburgh  Med. and Surg. Journal, No.  140;  Wagner, Iconea
Physiol.; Article "Ovum," in the  Cyclopaedia of Anatomy and Physiology, by Dr. Allen
Thomson.
CHAPTER  XLII.
ON THE  DEVELOPMENT OF  THE  DIFFERENT ORGANS.—DEVELOPMENT
  OF THE SPINAL COLUMN.—OF  THE FACE AND VISCERAL ARCHES.—
  DEVELOPMENT  OF THE NERVOUS  SYSTEM.—OF ORGANS OF VISION
  AND HEARING.—DEVELOPMENT OF THE HEART AND  AORTIC ARCHES.
  —OF  THE ANTERIOR VENOUS  TRUNKS.—OF THE LUNGS.—OF  THE
  THYROID.—DEVELOPMENT OF THE ALIMENTARY CANAL.—OF  THE
  LIVER AND PANCREAS.—OF THE SPLEEN.—DEVELOPMENT OF  THE
  WOLFFIAN BODIES AND KIDNEYS.—OF THE  SUPRARENAL CAPSULES.
  —OF  THE ORGANS OF GENERATION.

  In  the present chapter we have to consider the mode of develop-
ment  of the most important organs of the body; but we do not pro-
pose to  enter further into the process of development of the separate
tissues,  as this part of the subject has been already treated of in the
preceding chapters upon the anatomy of the different organs.
  Development of the Spinal Column.—In man and the higher ver-
tebrata, the spinal column is composed  of a number of  distinct and
separate segments, which are connected together by  the intervention
of a fibrous material.   This gives to the whole column  a considera-
ble  amount of  mobility.   In  the lower fishes, however, no such
division exists;  and in  the place of numerous vertebrae we have a
continuous mass of a soft consistence  running  through  the whole 
876
DEVELOPMENT
length of  the  animal, and known as  the  Chorda Dorsalis.   The
material of which this is composed is the simplest form of cartilage,
consisting entirely of a number of large cells, without the interposi-
tion of any matrix or  intercellular material between them.  In the
embryonic  condition of all vertebrate animals, we meet with a chorda
dorsalis entirely composed of cells, and possessing similar characters
to the permanent  chorda dorsalis of the cartilaginous fishes.  It is
seen as a faint streak at the bottom of the primitive groove.  Above
it, the central organs of  the nervous system are formed;  and imme-
diately beneath it, is the great artery of the body, with the viscera.
At the anterior and  posterior  extremities of the embryo,  the chorda
dorsalis tapers to a point.   In its earliest condition, it is composed
of a perfectly clear  gelatinous material, in the anterior extremity of
which cells soon make their appearance, and increase in number un-
til  the whole becomes cellular.   It  is  surrounded by a  delicately
fibrous sheath; external to which the blastema, which gives  rise  to
the development of  ossifying cartilage,  is deposited.   In this situa-
tion,  after  a time, cartilaginous  rings make their appearance, and
merge by insensible  gradations into the fibrous sheath.   The fibrous
structure gradually disappears, and in  its place cartilage is formed,
while at  the same  time the substance of the chorda is removed, to
give place to the developing cartilage.  The cells of the  cord, how-
ever, are not transformed into cartilage cells.  Eventually only a
portion of  the cellular substance remains between the bodies of the
vertebrae.  At a much later period, cartilaginous arches are formed
in the inner part of  the dorsal laminse, which become converted into
the vertebral arches.    The outer portion of the  laminee dorsales be-
comes converted into muscular tissues and integuments.
   The cranium is originally formed from an extension forwards  of
the chorda dorsalis,  and its development occurs at  a much earlier
period than the bones of the face.  In the lamprey and the sturgeon,
the connection between the chorda and  the cerebral cartilage is per-
manent.   In mammalia,  those  portions  analogous  to  the bodies of
vertebrae appear in the basis cranii;  and  prolonged from  these,
above, are portions corresponding to the neural arch of the typical
vertebra ; and below, parts belonging to the haemal arch.
   The body of the epencephalic or occipital vertebra is represented
by a distinct point of ossification, for the basilar process of  the
occipital bone; its neural arch by the expanded portion of the bone
itself; its hsemal arch by  the  scapulae, bones of arm, forearm, and
hand, and  the  coracoid processes of the scapula  (coracoid bones of
oviparous vertebrata).
   The body of the mesencephalic or parietal vertebra is seen in the
basi-sphenoid, or  body of the  sphenoid  bone;  its neural  arch is
formed by the mastoid  portions of the temporal bones, the great wings
of the sphenoid and the parietal bones ; its hsemal arch by the styloid
process of the temporal, and by the body and greater and lesser cornua
of the hyoid bones.
   The prosencephalic or frontal vertebra has its body represented  by
the anterior or spheno-orbital portion of the sphenoid;  its neural 
OF THE FACE AND VISCERAL ARCHES.
877
arch by the external angular processes of the frontal, the small
wings of the sphenoid, and the frontal bone; its hsemal arch by the
tympanic portion  of  the  temporal  bone, and by the articular  and
dental portion of the  inferior maxilla.
  The body of the rhinencephalic or nasal vertebra is  represented
by the vomer ; its neural arch by the ossa plana of the ethmoid, and
by the nasal bones ; its hsemal arch, by the palatine, pterygoid, and
malar bones, by the squamous and zygomatic portions of the temporal
bones, and by the superior maxillary and intermaxillary bones.
  In thus briefly describing the manner  in which the cranial verte-
brae are constructed,  we feel great regret that our limited space will
not permit us to enter more  at  length into the beautiful and well-
known discoveries of Professor Owen in this department.  We cannot
too strongly recommend the reader to consult upon this  important
subject, Professor  Owen's "Archetype Skeleton," and his "Homo-
logies of the Vertebrate Skeleton."
  Development  of the  Face and  Visceral Arches.—The visceral
cavity in the upper part of the embryo, at a very early stage of deve-
lopment, is bounded above by the cerebral capsule ; and below, and at
the sides, by the anterior visceral arch.  Reichert has shown  that
this arch  becomes bent upon  itself, and from  it are formed above
the angle, the superior, and below the angle the inferior, maxillary
apparatus.
  The superior maxilla grows upwards, and unites with a prominence
which is seen in the  centre of the  forehead, the frontal process of
Von Baer—a space  being left  between the two superior maxillae,
which becomes the nasal  cavity.  Beneath this, the two  bones are
connected together by the partition which forms the palate, and which
does not appear for some  time.
  In animals, besides the maxillary bones, there are a pair of narrow
bones between them,  extending from the interval between the lower
portion of the nasal, and the ascending process of the superior maxilla.
These are the intermaxillary bones,  which exist in the human fcetus
in a rudimentary condition.  They appear to be formed partly  from
the nasal process of  the forehead, and  partly  from a portion of
blastema which  is  detached from the lower jaw, to which Reichert
gives the name  of  intermaxillary rudiment.   In man  this bone is
not developed;  but in fishes and amphibia it  contains teeth.  The
intermaxillary bones  differ, therefore,  in their  origin, from the max-
illae, and are probably developed from centres independently of the
latter.   In  the  monstrosity familiar to us as  hare-lip, the superior
maxillae and palate bones of opposite sides do not meet, while the
intermaxillary bones  are united in the centre, and form a prominent
tongue of bone,  on either side of which is a deep fissure between the
intermaxillary and corresponding  maxillary   bones of each side-
thus is produced the  deformity of double hare-lip.  The cleft; ot the
nalate in these cases  usually remains open, and in this way the mal-
formation  is increased.   The fissure of the lip seems to arise  from
the alteration of the deeper parts;  for as such a fissure exists  at no 
878
DEVELOPMENT
period of embryonic life in the soft  parts, it cannot, like the  bony
fissure above described, be dependent upon an arrest of development.
   The first visceral arch gives rise to the  superior maxillary appa-
ratus, consisting of the intermaxillary bones, the vomer, the maxillary
and palate bones, and the pterygoid plates of the sphenoid,  the lower
jaw, and the malleus and incus.
   The second visceral arch gives origin to the hyoid bone, the styloid
process, and its ligaments, and the stapes of the ear.  In animals a
great part of this hyoid apparatus becomes ossified.
   From the third visceral arch arise the posterior cornu and body of
the hyoid bone.
   In the embryo of mammalian animals, the fourth arch is very in-
distinct.
   Development of the Nervous System.—Reichert has shown that, in
their earliest condition, the central organs of the nervous system are
composed of two laminae united in the middle line, so as to form a
central groove.  This groove soon becomes converted  into  a canal,
except in  the position corresponding to  the medulla oblongata.   In
front of this, certain vesicles appear,  from which the several parts of
the brain are subsequently developed.
   These vesicles have been named Prosencephalon, Deutencephalon,
Mesencephalon, and Epencephalon, by Professor  Owen.   Of these
vesicles,  the latter, which  corresponds to the cerebellum, is at this
early period, the largest  of  the four.  The mesencephalon,  or vesicle
of the  corpora quadrigemina, corresponds to the large  optic lobes in
fishes,  reptiles, and birds, which  in  these classes  are only two in
number (corpora bigemina), and in the adult human brain  is repre-
sented by the small  corpora  quadrigemina (anteriorly nates, poste-
riorly testes).  In front of this vesicle is a small one, which is formed
before any of the others, and for some time is the  most anterior of
all.  This is the vesicle of the third ventricle, and contains the optic
thalami.   These points are all well seen  in  the fish's brain.
   The prosencephalon, from which the cerebral vesicles are formed,
lies  in front of  this, and at first is extremely small; it bears a pro-
portion to the rest of the encephalon  not greater than that which  the
small,  unimportant cerebral lobes of the adult fish bear to its entire
cerebrum.  The prosencephalon soon, however, increases in size, and
becomes much larger than all the others.
   Our friend, Professor Retzius, has shown that  the three lobes of
the  hemispheres of  the human  brain.'are developed  at  different
periods;  the anterior being formed  during the  second and  third
months, the middle lobes between the end of the third and beginning
of the fifth  month, and  lastly, the  posterior lobes are produced.
The cerebellum was seen  by Von  Baer, in  the  chick, during  the
fourth day of incubation.  It is formed by the meeting of the laminae
of the spinal cord  anteriorly to the fourth ventricle;  a  short canal
is, however, left, which passes towards the corpora quadrigemina or
optic lobes, the future iter a tertio ad quartum ventriculum.
   Bischoff  has demonstrated that, at a very early period, nervous
matter is formed along the inner surface of the lips of the primitive 
OF THE ORGANS OF VISION AND HEARING.         879
groove. These two masses of nervous matter gradually approximate,
and thus a tube is produced, the walls consisting of nervous matter—
while the central cavity, after contracting, becomes the canal of the
spinal cord.  The upper portion forms the thin dilatations before de-
scribed ; while at the opposite end is seen a lancet-shaped depression,
the future  cauda equina, or sinus rhomboidalis in birds.
  Development of the Organs of Vision and Hearing.—According to
Mr.  Gray, the  eye  of the chick is first  seen about  the  thirty-third
hour  of incubation, in  the  form  of a  protrusion from the anterior
vesicle, which corresponds to the cerebral  lobes, and  may be called
the optic vesicle.  This view agrees with that of Baer; but it does
not accord with the observations of Wagner or Huschke.  The latter
observer states that the  eye is developed  from a protrusion of  the
vesicle of the third ventricle—from the deutencephalic enlargement.
The retina is a vesicular body which  communicates with the cavity of
the brain  through the hollow,  tubular  optic nerve.  These points
may be observed in the chick during the second  day of incubation.
Bischoff and Mr.  Gray have been unable to confirm the statements
of Huschke, with reference to the doubling-in of  the retina  to form
two layers.  The latter observes that the fibrous lamina and Jacob's
membrane  are  not developed  until after the cellular layer of  the
retina is formed.*
   About the third  day  of  incubation a fissure, which  commences  at
the border of the lens, is seen in the eye of the chick, which Huschke
regards as the consequence of inversion  of the retina.   In fishes,
the cleft running from the centre, towards the anterior border of the
retina, exists throughout life.  In the turtle there is a fissure in the
nerve but not in the retina.
   Jacob's membrane is  not developed before the  thirteenth or four-
teenth  day of  incubation.  Mr. Gray describes it as forming at this
period an exceedingly fine pale  granular stratum upon the choroidal
surface of the  retina.
   The circle of the iris is seen in the  anterior part of the choroid
at a very early period ;  but the pupil is  occupied by a highly vascular
membrane, the  membrana pupillaris.  This  is  not  attached to  the
margin of the  iris, but to its anterior surface, from which it derives
its -vessels; and it is probable that it is reflected over the whole
anterior surface of the iris, and possibly lines  the anterior chamber
of  the eye.   From  the  margin  of the  iris,  there  extends back-
wards another vascular membrane, the  membrana capsulo-pupillaris,
which is  united to the  border of the capsule  of the lens.   This
membrane forms a closed  sac, the  anterior part of which is united
to  the membrana  pupillaris;  while the posterior portion lines  the
anterior concave  surface  of the  vitreous body._ This is  supplied
with vessels by the capsular branch of the arteria  centralis retinae;
and at the margin  of the  iris, the vessels of the membrana pupillaris,
and  those of  the  membrana  capsulo-pupillaris, communicate  with
those of the iris.
* Phil. Trans., 1850. 
880
DEVELOPMENT
  The eyelids  are  first  developed in the form of a ring, which ex-
tends over the surface of the eye ;  and afterwards the two portions
which are to be  developed  into the lids become adherent to  each
other.   They separate again, either before  birth, as in  the human
subject—or after  birth, as in the carnivora and some other classes.
  Organ of Hearing.—The ear appears, at a very early period,  upon
the vesicular protrusion which ultimately becomes the auditory nerve.
It communicates  with the  cavity  of  the fourth ventricle, and is
situated above the second branchial  cleft.   The first rudiments of the
auditory vesicle were seen by Mr. Gray about the  fiftieth  hour of
incubation  in  the chick.  Throughout the  life of the cyclostomous
fishes, the ear  retains the  condition which it presents  at an early
period of development  in  the mammalia.  Valentin describes the
labyrinth as  appearing  in  the form of a separate body of  a some-
what elongated form.  The inner extremity forms a turn  and at this
point a second vesicle  makes its  appearance, which becomes the
cochlea.
  The semicircular canals are developed by a contraction and folding-
in of the walls  of the vestibule.   From Mr. Gray's careful observa-
tions, it appears that the labyrinth, about the  twelfth or thirteenth
day of development in the chick, has an appearance closely resembling
the retina  at  the same time—a point of great interest.  Huschke
has  shown that the Eustachian tube,  the cavity of the  tympanum,
and  the external meatus, are the remains of the first branchial  cleft,
which eventually  becomes divided by the membrana tympani.
  The ossicles of the ear are formed as follows: The malleus and
incus, according  to  Reichert, are produced from the first visceral
arch, which also  gives origin  to the superior  and inferior maxillae.
The  stapes appears  to be  produced from the second visceral  arch,
which also gives rise to the hyoid bone and its suspensory apparatus.
The  ossification of  these little ossicles commences in  the fourth
month of intra-uterine life.
  The development of the mouth and nose have already been alluded
to at page 877.
  Development of the Heart and Aortic  Arches.—The development
of the heart is best studied in  the chick.  It appears towards the
end  of the second day of incubation, as a small hollow tube between
the mucous and serous laminae of the  germinal membrane.  About
the thirty-sixth hour it has become a simple tube, much  curved and
twisted upon  itself.  Posteriorly, it terminates in two or three  large
venous trunks, which are insensibly lost on the germinal  membrane ;
and  anteriorly, it divides into two branches, which unite beneath the
vertebral column to form the aorta.  The trunk  of  the vessel again
divides  into  two  branches, which  are lost on the  vascular  area.
Early on the third day, the heart consists of three cavities—the  sinus
venosus, the ventricle, and the bulbus aortae ;  the first soon becomes
divided into  the  two auricles, and by the fourth day the ventricle
assumes  its usual form, and  the  formation  of  the septum,  which
divides its cavity  into two portions, commences.
  About the beginning of the third day, the aortic bulb  divides into 
OF HEART AND AORTIC ARCHES.
881
four pair of vascular arches.   On the fourth day, the first pair dis-
appears and  is  at  length obliterated, and the second pair becomes
smaller; but  now is formed  a fifth pair, which becomes  larger  on
the fifth day, while the second  entirely disappears; so that there
are at this time only three pairs, and these  of nearly equal size.
   About the sixth day, a  considerable  alteration takes place in the
circulation.  By this time, the allantois forms a vesicle of considera-
ble size, upon the surface  of  which numerous vessels are spread out.
These are  derived from two branches  resulting from the division of
the aorta after it has given off the mesenteric artery.   The allantois
rapidly increases in size;  and as the albumen diminishes in quantity
it becomes applied to the  membrane of the egg-shell.  Through the
latter, and through the pores of the  shell itself, the  air passes to
aerate  the blood circulating in  the vessels of the allantois, which
may therefore be looked upon as the great respiratory surface of the
 chick previous to the formation of  lungs.
   About the  sixth or seventh day, the heart acquires  its character-
 istic form ; its cavities have approximated more closely, and  become
 conjoined; the  division between the auricles  and ventricles can be
 seen distinctly.   The bulb of the  aorta appears  to rise  from both
 ventricles, immediately over  the septum; and  its division into two
 canals is complete on the  seventh day.  The pericardium is  formed.
 Only  two  vascular arches arise on  the  left  side of the aorta, but on
 1, 2, 3.  Heart of chick at the 45th, 65th, and 85th hours of incubation.  After Dn Allen Thomson

3- fent^ict %hZirsttreyrioasbu°sUtethee Two" aTtfe .^^^t.^^™^^^
I. V^&^StoSZSSS? * ^Ptum arising from the lowest part of the cavity of the ven-
tricle.  t. Inferior vena cava.
the right there are three.   The latter, and the  two anterior arches,
are the chief divisions of the aorta,  and receive the blood transmit-
ted from the left ventricle.   On the seventh day  the  two posterior
arches receive blood only from  the right ventric e, and  become  the
pulmonary arteries.  At present,  however, all the arches terminate
in the descending aorta.                   #
   At this  period, the course of the blood is as follows: From  the
system of the embryo it is carried by the arterial vitelline, or omphalo-
Telentericce, to the' network of vessels of  the vascular area, whence
it  passes to the sinus terminal*, which bounds he ^ an^ ^
even on the fourth day, is found to  be full of b ood; J^^8
returned to the heart by two anterior and two posterio venous; trunks

arranged in pairs ^^^^fZ poL^i^pa^re the^
;SSTwhKry back  the blood fr^m the Wolffian bodies 
882
DEVELOPMENT
and  hinder parts of the embryo.   Besides  these trunks, however,
there is a single one  below, which  receives the blood from the om-
phalo-mesenteric veins, and into this trunk the umbilical veins open
subsequently.   It becomes eventually converted into the inferior
vena cava.
  The pulsations of  the  heart  commence before any cavity can be
observed in the mass  of embryonic cells of which it at first consists.
Prevost and Lebert have observed the contractions before the  deve-
lopment of any tissue  distinctly  muscular—a statement  which we
can confirm from  observations upon the heart of the young field-snake
(coluber natrix).   Bischoff and Vogt also testify to the very  early
occurrence of  pulsations.
  In the human subject, about the fourth week, the septum between
the ventricles  commences to be formed.  This is completed by the
termination of the eighth week.   The auricular septum, however,
remains incomplete  throughout foetal  life.  The circulation in the
foetus, and the peculiarities of the foetal  heart,  have  been already
described in page 677 of the present volume.
  Aortic Arches.—In fishes, the vessel continuous with the bulbus
arteriosus gives off on either  side large branches, which are  distri-
buted to the gills; from these organs the blood is collected by small
vessels, which ultimately reunite to form a large trunk correspond-
ing to the aorta, which  lies immediately in front of the spine.  In
the early embryos of all vertebrate animals, similar branches, called
aortic arches,  may be seen ; and these unite at the back of the vis-
ceral cavity, to form the descending aorta.  They are  visible in the
chick about the fortieth hour, according to Dr. Allen Thomson.
  In birds there  are  at first six aortic  arches; but, as  development
proceeds, the  number becomes less.   In mammalia the arches soon
diminish to three.  One becomes the arch of the aorta, and the  other
two  are the ductus arteriosi of the pulmonary artery, of  which the
right soon disappears, so that at  length only two arches  remain—
one  from the right, and the other from the left ventricle.   The  an-
terior part of the arch from the former  becomes the  trunk of  the
pulmonary artery; while the cavity of the posterior portion (ductus
arteriosus), which leads  into the aorta, gradually becomes obliterated,
and  soon after birth nothing remains of it  but  a fibrous cord, between
the aorta and pulmonary artery, which marks its  original position
throughout life.
  Anterior Venous  Trunks.—At an early period of development of
the human embryo, the  veins entering the heart from the upper part
of the body are symmetrical; and  in many of the lower animals they
preserve this arrangement throughout  life.  As the development of
the human embryo advances the large venous trunk on the left side
diminishes, and subsequently disappears  entirely, leaving  the right
trunk only as a persistent vessel.   In a valuable paper published in
the  Philosophical Transactions,  Mr.  J.  Marshall shows  that  the
dilated portion of the coronary vein, the coronary sinus, is the per-
sistent  lower portion  of the left anterior vein.   It is interesting, that
in animals which have a left superior cava, the great cardiac coronary 
OF ALIMENTARY CANAL.
883
vein opens into it.  Even in the adult human heart there are certain
structures which are obviously the remains of the upper portion of the
left primitive venous trunk.  " These observations are very interesting,
as they serve to explain certain unusual arrangements in  the great
anterior veins.   Cases  are recorded in which  the two symmetrical
trunks, usually only found  at a very early period of development,
remain persistent in the adult—an abnormal condition which receives
explanation from  the  investigation of  the nature of the  early em-
bryonic changes.
   Development of the  Lungs.—The lungs are  first seen in the form
of  two small  masses  of  cells, at  the lower part of the oesophagus.
These masses gradually  increase  in
size, and  a cavity is formed  within.             Fig. 285.
They  coalesce  at  the  upper part,     a         b          c
which ultimately becomes the trachea.
At this period of  their development,
the respiratory organs appear in the
form  of  vesicles,  appended  to  the
lower part of the trachea.
   Reichert has  shown that  in  the
 chick the lungs  appear about  the
 same  time as  the liver, and  states,
 that although they seem to take their   ll^rM^Smtn7p.°^S°aii:
 rise from the membrana intermedia   ™^™^^^£$%;.
 (Wing between  the rudimentary ner-   cubation.  The rudiments ofthe trachea and
 w  o         j  .1          „™«.v,    lungs of the left side.  1. Inferior wall of
 VOUS Centres  and  the  mUCOUS mem-   the oesophagus; 2. Superior wall; 3. Rudi-
 brane, p. 864), the upper portion  of   ™^Z&: t^e anl'^
 the visceral  tube, according  to his   fiT^**^™^^^
 observations, is the real seat  01 their   seen from  behind.
 origin.
    Thyroid Glands.—The first traces of the thyroid are observed in
 the chick between the sixth and seventh  days as a small spherical
 mass of blastema on each side of the root of the neck.   In structure
 the thyroid  resembles that of the spleen. Professor  Goodsir  de-
 scribes the thymus, thyroid, and supra-renal capsules as arising from
 the membrana  intermedia;  but  Mr.  Gray, on the other  hand  has
 pointed out  that they are formed from separate and  independent
 masses of blastema.                             .          .
    The development of the  thymus gland, and  its  subservience to
 respiration, have been already considered in p. 817.               #
    Development of the Alimentary Canal.—The alimentary canal is
 first seen in the form  of an elongated straight tube, in which oil glo-
 bules may be distinguished.   According  to Reichert's observations
 on the embryo of the frog, the walls  of the  intestine appear  to be
 formed originally from the most superficial cells of the yolk    Ihe
 mucous membrane is  developed from a thin layer of smaller cells of
 Z yo kTn the interior.  Between the outer layer, which  becomes
 converted into the muscular  coat, and the inner layer,  which con-
  futes the mucous membrane, a glandular layer is  formedF™m
 this tube the  different parts are gradually evolved.  Ihe omptialo 
884
DEVELOPMENT
mesenteric duct is connected with the lower part of the small intes-
tine, just  previous  to its junction with  the large intestine.  The

                                Fig. 286.
 Embryo dog, showing the junction of the umbilical vesicle, with the intestinal canal, a. Nostrils.
6.  Eyes. c. First visceral arch.  d. Second visceral arch,  e, f. Right and left auricular appendage.
g, h. Right and left ventricle of the heart, i. Aorta, k. Liver, between the two lobes of which is re-
presented the divided omphalo-mesenteric vein. I. Stomach, m.  Intestine, communicating with the
umbilical vesicle by the omphalo-mesenteric duct. n. Umbilical vesicle, o. Wolffian bodies, p.
Allantois.  q. The upper extremities, r. The lower extremities. After Bischoff.

original  connection with the umbilical vesicle is sometimes marked
by an  elongated pouch, or  diverticulum, persistent  in the  adult.
The original  yolk-cells, contained in the  cavity of the intestine,
slowly disappear.  The  length of the small  intestine gradually in-
creases,  until it assumes  its mature form.
   The stomach, at an early period, is not wider than the rest of  the
canal, and its  limits are not to be distinguished.
   Originally,  the tube of the  intestine is completely closed, both at
the mouth and anus.   The membrane is  gradually removed, and an
opening formed.   In cases of imperforate anus there is no opening,
in which condition an operation is necessary as soon as possible after
birth.
   Development of the  Liver and Pancreas.—The precise mode of
origin of  the  liver in the embryo has not yet been ascertained with
certainty.    Some observers hold that this large  gland  is originally
formed  upon a diverticulum of the intestine, while others have  con-
cluded  that it is developed from  a  distinct and  separate  mass of
blastema.   In the chick,  the first rudiment of this  organ may be  dis- 
OF SPLEEN.
885
cerned between the fiftieth and sixtieth hour, and is described by
Remak as consisting of two sets of cells—an external one, continu-
ous with the external surface of the intestine, and an internal layer,
composed of epithelium, and lining the sac, which ultimately becomes
divided, so as to form ducts.  From the epithelial lamina the columns
of liver  cells are formed;  these extend into the outer lamina,  branch
and anastomose, and include in the  meshes thus produced the cells
of the outer surface, from which the vessels, nerves, and areolar tis-
sue of the gland are developed.
   Miiller describes the liver as formed, on the fourth day of  incuba-
tion, by a  conical  protrusion  of the  intestinal tube.  The walls of
the protrusion become very thick, and in their substance the ducts
ramify.
   According to Reichert, the liver and pancreas in the embryo frog
are developed from a portion of yolk,  which becomes separated from
the general mass at a very early period, and is penetrated by a pro-
longation, posteriorly,  of the vessel  continuous with the cavity of
the heart. At first there is no appearance of a division in this mass
of yolk substance, which becomes separated from  the  remainder
before any trace of the alimentary canal has manifested itself.  Sub-
sequently the two  organs become more distinctly marked out.  In
the chick, according to the same observer, these organs  are formed
 from a  cellular growth upon the surface of the membrana intermedia,
 which is separated  from  the  rest of  this membrane.  At firsl;, the
 two lobes of the liver are of  equal size, but, after a time, the right
 lobe preponderates, as it  does in the adult.
   Mr.  Gray has figured the liver and pancreas of the chick.  They
 seem to be developed from two separate protrusions of the intestinal
 tube, about  the ninetieth hour  of incubation.  No vestige of the
 spleen  is to be detected at this early period.
   The  following is Dr. Handfield Jones' account of the development
 of the  liver in the chick.  The parenchymatous portion  is found  to
 appear first;  soon afterwards, an eminence, for which Dr. H. Jones
 proposes the name of colliculus, makes its appearance on the wall of
 that portion of the intestine which becomes the duodenum.  From
 the latter tube pass two  offsets to  the liver;  these, however, waste,
 but the colliculus remains.  Subsequently,  the  cystic  and hepatic
 ducts are developed close to the liver; they extend downwards, and
 open at the colliculus.  In fishes and reptiles, the process of  develop-
 ment is similar. Dr. H.  Jones observes that, at one period,  the gall-
 duct in tadpoles is lined  by ciliated epithelium.
    Reichert describes the formation of the columns of liver cells, and
 their increase  in  number; but he considers that the cells  are not
 invested with  basement  membrane.   This question has,   however,
 been discussed in Chapter XXXIII.                      .   .
    SfaUen— Mr. Gray has demonstrated that the spleen  arises in a
 fold of the intestinal  laminae about  the 114th hour of incubation  in
  heMt anfit is probable that  in the human ^ect^rma
 tion takes place during the third or fourth week. It "quite distinct
 from the pancreas from  the earliest period of development.
         57 
886
DEVELOPMENT
  The first traces of  the  splenic vein  are seen about the thirteenth
day of incubation ; and the first blood discs appear in the organ about
the eighth day.  The  Malpighian vesicles are not developed till about
the twentieth or twenty-first day, when the period of incubation is
near its completion.   It is probable that during foetal life this organ
plays no very important part, either in the development or destruc-
tion of blood  corpuscles ; and, as the gall-bladder is found to contain
yellowish-green  bile, before  the formation of the spleen, it is clear
that this organ, at least in intra-uterine life, is not concerned  in pro-
ducing the colouring  matter  of that fluid—an office assigned to  the
spleen by Kolliker.
   Wolffian Bodies.—The  Wolffian Bodies are two small glands  de-
veloped at  a very early period, and situated upon each side  of the
spine, extending upwards for some distance.  They lie in front of the
kidneys and supra-renal capsules, figs.  283, 286.
  Each Wolffian body is provided with an excretory duct, which
opens  into the  cloaca or sinus urino-genitalis, whence its contents
pass into the  allantois.
  These bodies are to be regarded in the light of temporary kidneys,
and bear a  similar relation to the permanent organs, that the  tempo-
rary branchiae of the tadpole bear to the lungs of the fully developed
frog.
  In  osseous fishes, the corpora Wolffiana are  permanent, and con-
stitute the kidneys of this class of animals.
  They are  much  elongated, and are  composed of a number of
transverse  caecal tubes arranged  parallel to  each other.   At first
they completely conceal the kidneys, but soon diminish  in size,  and
are at length placed below those organs, which  at the same time are
gradually assuming importance.
  The Wolffian bodies are not eventually transformed into  the epi-
didymis, as some have held,  or, indeed, into any other organ;  but
they disappear completely.   The  ducts of  these glands, however,
take part in the formation of the Fallopian tube  in the female,  and
of the vas  deferens in the male;  and the  last  traces of the tem-
porary corpora Wolffiana  are found to  have  some  relation  to  the
generative  organs.   Their remains constitute the parovarium in the
female (p. 842).
  From  the  lower part  of  the excretory tube, in those  animals
whose uterus is bifid, its  cornua are developed.   In the human sub-
ject, although at a very  early period  there  are two  cornua, these
soon  coalesce with the central part   of the organ  which  is being
developed at  the same time,  and at last all traces of  them are lost.
   The corpora Wolffiana  disappear at a much  earlier period  of de-
velopment  in the  human  foetus, than  in the lower mammalia ; but
Miiller has figured  traces of  them in an embryo about 3£ inches in
length.  Each  body  was  composed of  numerous transverse caeca,
passing from the Fallopian tube towards the corresponding ovary.
   The kidneys  are developed independently of the  Wolffian bodies,
and are situated  on  the  inner side of the ducts of these temporary 
OF ORGANS OF GENERATION.
887
organs.   As  the latter gradually diminish in size, the development
of the former advances.
  Supra-renal Capsules.—The investigations of Mr. Gray upon the
development  of the supra-renal  capsules in the chick, have proved
that these bodies are not to be recognized before the end of the 7th
day, when an ill-defined granular mass, of a reddish colour, makes its
appearance between the aorta and upper and inner sides of the Wolf-
fian  bodies.   It seems to have  no connection with the thyroid or
thymus, as Professor  Goodsir described.  Its minute  structure re-
sembled  that of the  spleen about the fifth day of  incubation.  By
the  8th  day, vesicles  could be distinguished, and by the 14th  day
were found to contain oil  globules, but no nuclei could be  detected
in their interior.  The capsules were of large size, and of a yellow
colour by the 18th day, and now the division into cortical and medul-
lary portions  was  quite distinct.  The supra-renal capsules are de-
veloped from  two separate masses of blastema, situated between the
aorta and upper and inner extremities of  the Wolffian bodies.  They
have no connection with the latter, or with each other, and although
in  their minute structure they resemble the spleen, they arrive at
their maximum of development before that organ.
   Organs of Generation.—The sexual  organs are developed  at a
later period  than  other glands.  They are  formed from  masses of
blastema  situated upon the inner side of the upper and free part of
the  ducts of the  Wolffian  bodies.   The ovaries and testicles are
developed independently of the Wolffian bodies.  At an early period
of development the glands in both sexes have very similar characters,
and  it  is not possible to  say whether the organ  is  ultimately to
become converted into a testicle, or whether it is to retain its primi-
tive characters, which agree with those of the  ovary. _  According to
the  observations of Valentin, the ovary of mammalian  animals is
 developed in the  form of tubes, in which the Graafian follicles are
produced.
   The  excretory ducts in the lowest  vertebrata are two  in number,
 and  open into  the cloaca, an  arrangement which  is  persistent in
 many fishes, but in the higher  classes  they are united, and form a
 single canal, the  arrangement of which  has been carefully investi-
 gated by Muller.   From this canal, in the male, is formed  the We-
 berian  organ, or  uterus  masculinus, while  in the female it gives
 origin to the uterus and vagina.                               .
   The upper part of the excretory duct of the Wolffian bodies in
 the male, becomes much modified in character, and is ultimately con-
 verted into the epididymis, whilst the lower portion becomes the vas
 deferens
   The  lower part of the urino-genital canal, which becomes con-
 verted into the external organs of generation for some time presents
 a cleft  or fissure on its inferior surface, which in male reptiles ana
 birds remains open  throughout life, but in mammalia becomes con-
 verted  So a canal, which extends to the tip of the penis in the male,
 or along the under surface of the clitoris in the female.  Sometimes,
 howeve? a portion remains open, and tho wall of the urethra is de- 
888
DEVELOPMENT.
ficient  in its anterior part  below, when the  congenital deformity
known as hypospadias results.   The folds of skin which bound the
furrow, ultimately become converted into the scrotum of the male, or
labia of  the female.   The testicles descend  into the  cavity of the
scrotum  about the eighth  month, but  not unfrequently are  retained
within  the abdominal  cavity.

  The authors would refer particularly to the following works with  reference to the
subjects  discussed  in the present chapter:  Miiller's  Physiology; Rathke, Beitrage
zur Geschichte der Thierwelt;  Valentin, Entwickelungs-Geschichte;  Dr. Handfield
Jones on the  Structure and Development of  the Liver, Phil. Trans., 1849; Victor
Carus' System der Thierischen Morphologie;  Reichert, das Entwickelungsleben im
Wirbelthier-Reich; Mr. Marshall's paper On the Development of the  great Anterior
Veins in Man and Mammalia, Phil. Trans., 1850; Mr. Gray's papers On the Develop-
ment of  the ductless Glands in the Chick, Phil. Trans., 1852; and his paper on the
development of the retina and optic nerve, and of the membranous labyrinth and
auditory nerve, Phil. Trans., 1850.
                         CHAPTER  XLIII.


OF  THE MEMBRANES OF  THE FOETUS.—OF THE  STRUCTURE  OF  THE
   CHORION.—OF   THE  AMNION.—LIQUOR  AMNII.—OF   THE   UMBI-
   LICAL  VESICLE.—OF  THE ALLANTOIS.—ALLANTOIC FLUID.—UMBI-
   LICAL  CORD.—BIRTH.


   Formation of the Placenta.—The early development of the chorion
has been described in a former page.  At first, the villi are composed
entirely of cells,  invested on their external surface with  a very deli-
cate structureless membrane; but  after the vessels, conducted by the
allantois, have reached its inner surface, vascular loops are prolonged
into them.   Bischoff considers that in the human ovum, and in  that
of the bitch, which are destitute of an albuminous covering, the tufts
are formed directly from the zona pellucida alone.

  In two orders of mammalia, the marsupialia and the monotremata, there is no con-
nection between the vascular system of  the mother and that of the foetus, which is
nourished from a very early period with milk.
  The relation  between the blood of the fcetus and that of the  mother is nearly the
same in all placental mammalia.  The wall of the maternal vessels—a layer composed
of cells from the modified mucous membrane of the uterus—and another cellular layer
belonging to the foetal tuft, always separate them; but in the greater number of mam-
malia, the foetal tufts come into relation with the capillary vessels of the mother; while
in man they are in contact with the walls of a  large cavity containing blood.
  The mode of arrangement of the tufts, or, in other words, the form which the pla-
centa  assumes,  is very different in  the various mammalia.  Sometimes the whole
chorion is covered with villi, as in the pachydermata (hog, elephant, etc.); sometimes
these form little collections  or cotyledons, as in the greater number of ruminants
(sheep, ox, goat, etc );  sometimes they form a band encircling the central portion of
the chorion, as in the  carnivora; and in some instances they  are confined to one single
part, forming a single placenta, as in the rodentia, and also in the human subject (vide
figs. 280, 292).
  The beautiful branched and highly complicated conical foetal villi of the ruminant
dip into deep recesses in the maternal cotyledons, upon the walls of which the maternal 
CHORION,
889
Fig. 287.
capillary vessels are spread out; while the vascular loops of the human foetus, as was
shown by Professor AVeber, dip into the dilated vessels of the mother, which become large
venous sinuses, and are thus completely bathed on all sides by the mother's blood.

   The villi increase very much in number and complexity in  that
part of the chorion which is to become the placenta ;  while on other
parts of the surface they retain the  same characters as at  a very
early stage.  Each villus contains a vascular loop, which is directly
continuous with the umbilical vessels of the fcetus; and the whole  of
the blood of the foetus  is  made to pass through  the vessels  in the
tufts by the forces of the fcetal circulation.   The cells of which the
villi were  entirely  composed,  at a very  early period diminish  in
number; but still several remain towards the apex.
   During this time, the soft  membrana decidua  has been increasing
in  thickness  and vascularity.   Its  capillary vessels become enor-
mously increased in diameter, and ultimately form small pouches  or
sinuses containing blood.   The foetal  tufts come  into close relation
with the walls  of these sinuses, but are still separated by a thin layer
of the cellular decidua, and project into their interior, being of course
invested with the wall of the sinus, just as  the viscera are covered
with peritoneum.   Such  is the relation of the  bloodvessels  of the
foetal  placenta to those  of the mother, accord-
ing to the observations  of Dr. J.  Reid, Weber,
and Goodsir.   The structures, therefore, which
intervene  between  the  blood  of  the foetus and
that of the mother, are  the following: the walls
 of the foetal capillaries  ; the cells at the extre-
mity of the foetal tufts; the delicate  investing
membrane  covering these ;  a thin stratum  of
fluid separating the maternal and foetal portions
 of the placenta,  and containing  not  only the
materials  for  absorption, but  any substances  to
 be removed from the foetal blood; the cells of
 the membrana decidua; and, lastly, the wall  of
 the venous sinus, into which the  fcetal tuft pro-
jects.
   The cells upon the surface of the villus form
little groups, and appear to radiate, as it were,
 from the centre  of each collection.   This cen-
 tral point, Professor Goodsir regards in the
 light of a germinal spot or nutritive centre, which supplies successive
 generations of cells as  the old ones are gradually removed.
 3 The wall of the venous sinus  of the  mother, reflected  from tuft
 to  tuft, forms numerous  tubular  processes, passing  in various  di-
 rections amongst them; thus connecting the several tufts with each
 other, and forming a  sort of supporting framework  for the entire
 orsran   The  tubular prolongations, of course,  contain cells ot  tne
 decidua in their interior, and by their outer surface  are continuous
 with the lining membrane of  the venous sinuses of the mother.   L»r.
 J. Reid has shown that the foetal tufts often dip quite into the uterine
 Extremity of a villus,
showing capillary vessels.
After Weher.
sinuses. 
890
DEVELOPMENT.
Fig. 288.
  Weber has made some beautiful injections of the foetal tufts, which
demonstrate  very satisfactorily the highly tortuous  nature of  the
                    capillaries, and show that the convoluted capil-
                    lary vessel may make many turns from one foetal
                    loop into another, before it opens into one of the
                    branches of the umbilical  vein.   Dr.  Reid de-
                    scribes the blood brought by the curling arteries
                    of the uterus as being  poured " into a large sac
                    formed by the inner coat of the vascular system
                    of the mother," from which the blood is carried
                    back  by  the  veins.  The researches of Dr. J.
                    Reid  agree with those  of Weber; but Eschricht
                    holds, that in man the arrangement is essentially
                    the same as in animals ; and that the capillaries
                    of the placenta of  the  human  foetus are brought
                    into  relation  with  the capillaries only of  the
mother.   In many animals, the maternal and foetal  portions of  the
placenta can be very readily  separated  from each other ;  but in man
this cannot be done without tearing the vessels.
 Relation  between  the
fetal  and maternal ves-
sels ; after Dr. Reid. Foetal
tuft dipping  into dilated
venous sinus, a. Curling
artery of uterus, b. Ute-
rine vein.  c. Sinus.   d.
Vessels of foetal tuft, com-
posed of a small branch of
artery and vein.
Fig. 289.

 Uterine sinuses and foetal tufts ; after Dr. Reid.  e. Curling artery of the uterus.
into which a tuft is prolonged, e. Foetal tuft.  b.  Foetal vessels branching.
a. Uterine sinus,
   The formation of the  placenta commences  in  the human subject
towards the end of the second month; and by the third it assumes
its ordinary character.   As the uterine vessels become enlarged, the
rush of blood through them is accompanied with a well-known mur-
mur, termed the placental bruit, which is usually detected about the
third month.   It is one  of the most  important signs of pregnancy,
and  is not liable to be mistaken for the sounds of the fcetal heart,
because it is  exactly synchronous with the mother's pulse, and its
situation does not vary.
   Towards the  termination of the period  of pregnancy, the placenta
becomes hard, and a curious change takes place in its capillary ves-
sels, which has only been carefully investigated  within  the last few
years.  The alteration consists in the appearance  of  a number of
oil-globules in the coats of the vessels—in fact, in the occurrence of
fatty degeneration of the  foetal tufts.  In a former page, we described
a  similar change taking  place in muscular fibre-cells of the uterus,
when the  period of  their activity was passed, and the organ was
gradually  returning to its former volume.   The  change alluded to 
                            PLACENTA.                        891

has been looked upon by many pathologists as of a morbid  nature,
and has been brought forward as one of the causes of abortion ; but

                              Fig. 290.
 Villi of the foetal portion of a placenta; after E. H. Weber.  1. Vein. 2. Artery. Magnified 100
diameters.

the observations  of our friend, Dr.  Druitt,* and others, show that
fatty degeneration of the vessels occurs in the great majority of pla-
centae which  are  subjected to examination, although in  some it  is
much more advanced than it  is in  others.  It occurs first in those
tufts situated at the circumference  of the placenta, in which  part the
functions  of  the  organ cease first.   In  numerous  instances, also,
small masses  of  earthy phosphates  are found  in  the  foetal tufts.
Although fatty degeneration is  doubtless  to be regarded,  in many
instances, as  a  morbid alteration, we  must  at the same  time bear in
mind, that it does  occur  as  a normal  process, and is  one of the
changes which  ensues in tissues prior to their absorption, after the
period of their functional activity is brought to a close.  It seems
to be one of the first of a series of changes which ends in the removal
of the tissue, or in the complete  disappearance of its ordinary cha-
racters.
   From what we have already said with reference to the structure  of
the human decidua and placenta, it  follows, that both are separated
at birth, and must be renewed at each successive pregnancy.  Both
the uterine and foetal portions of the placenta are removed, and  of
course a  considerable  lesion  takes  place  at the  time.   The great
uterine veins are torn across, and  the  violent  contraction  of the
uterus alone  prevents the  death  of the  mother from  hemorrhage  at
each period of parturition.  Should  the uterus,  from any cause, fail
to contract, the death of  the  mother from hemorrhage  is inevitable,
as the experience of almost every practitioner but too clearly proves.

                    * Medico-Chir. Trans., vol. xxxvi. 
892
DEVELOPMENT.
Such a result, however, would not happen in the ruminants, and in
some other animals, where the foetal tufts are readily withdrawn from
the maternal sheaths, which  merely contract after parturition, and
become much smaller, but suffer no lesion whatever.
  Amnion.—The early stages of  the  development of  the  amnion
have been already fully described (p. 866).   It  is  formed upon the
same plan in all classes  of  animals, as  it is in the human subject, as
the later researches of Bischoff have conclusively shown.  The human
ovum, at an early period of  development, is  seen  to  be closely in-
vested with the amnion ;  which  membrane, originally consisting of
two layers, is  separated from the  chorion by a considerable space,
which is entirely occupied by an  albuminous material of a jelly-like
consistence, the " corps  reticule" of Velpeau.  This  substance is
separated from the chorion  by a  thin membrane,  the endochorion;
so that it appears to be contained within a special sac.
  The amnion consists  of a closed sac, and it is prolonged over the
structures of the cord, in the form of a tubular sheath, which becomes
continuous Avith the integument  of the foetus  at  the navel.  The
amnion  is tolerably transparent, and not very  thick; but often so
firm, that it cannot  be ruptured very readily.  No vessels, nerves, or
lymphatics have yet been demonstrated  in the healthy membrane;
but in some cases of disease it has been found to be highly vascular.
M. Coste speaks of the amnion as the " epidermis of the blastoderma."
  The sac of the  amnion  contains  a  considerable quantity of an
albuminous  fluid, the  liquor  amnii, which, according to  Vogt, con-
sists of common salt, lactate of soda,  albumen, and sulphate  and
phosphate of lime.   Dr. G.  0.  Rees has found urea in  the liquor
amnii, and the presence of this substance has been  confirmed  by
other observers.  The liquor  amnii, at three and a  half months, had
a specific gravity of 1-0182, and contained 10*77 of albumen in 1000
parts ; and at six months its  specific gravity was 1*0092, and it con-
tained only  6-67 parts of albumen per  1000.
  Liquor Amnii.—The liquor amnii enters the  mouth of the foetus,
and no doubt passes into the  trachea as well as the  stomach ; but  the
amount of nutrition which  the foetus receives from this source, must
indeed be small.  At the same time, it is interesting to observe that
the composition of the liquor amnii varies at  different periods of
pregnancy,  as has  been shown  by  Vogt; and  during  the earlier
periods  of gestation,  the quantity of  chloride of sodium is much
greater  than during the latter part of the time.  The proportion of
this substance appears to be greater at that period of the development
of the embryo, when cell-multiplication and growth is most active.
   Dr. Beale has made, for Dr. A. Farre, an examination of liquor
amnii at the  eighth month,  taken from the  body of a woman who
died at this period of gestation.   The fluid was of  a very pale straw
colour, slightly turbid, and  contained flocculi suspended in it.  It was
quite limpid, and readily dropped  from a tube.   It was very feebly
acid, and remained so for several  days after it had been removed.
The deposit was subjected  to microscopical examination, and found
to contain many epithelial cells and  oil-globules  from  the vernix 
UMBILICAL VESICLE.
893
caseosa, the soft oily coating with which the skin of the fcetus becomes
covered in the later months of pregnancy.  Besides these, there were
several  clear, transparent,  elongated  cylindrical  bodies,  evidently
casts  of the  uriniferous  tubes  of  the kidney  of  the foetus.   This
observation proves, very satisfactorily, that the  urinary  secretion
becomes mixed with the liquor amnii in the human subject.
   The specific gravity of this specimen was 1009-2 and it  contained
in 1000 parts—
AATater .
Solid matter
Organic matter soluble in water
Fixed alkaline salts    .    .    .    .
Albumen, earthy salts, and fatty matter
982-00
 1800

 611
 8 09
 3-80
In 100 parts solid
   matter.
33-94
44 94
2111
Fig. 291.
  Dr. Prout found sugar of milk in the liquor amnii of a cow, at an
early period of pregnancy.
  Umbilical  Vesicle.—We have alluded to the mode of formation of
the  umbilical vesicle in page  866.  Our friend, Mr. Grainger, has
made some very important observations on its minute  structure and
functions in the chick.  At a very early period, the lining membrane
of the umbilical vesicle presents the appearance of a highly organized
mucous membrane, the surface of which is perfectly smooth.   After
a time, a number of folds, which were termed  "valves" by Haller,
make their appearance.   By  the  ninth day, these are considerably
developed,  and project into the yolk.   The folds become more com-
plicated and numerous;  and  by the nineteenth  day, are as much as
T52ths of an inch in depth in the deepest part.  Upon the folds, and
in the intervals between them,  grayish-white corpuscles  are very
numerous.  Mr. Dalrymple has shoAvn that these cells may be washed
away from the  vessels beneath, of which he has made very beautiful
injections.   The yellow  appearance  of the
vessels,  whence they have been  called vasa
lutea by Haller, is due to their being  entirely
covered with  these yellowish corpuscles.  The
surfaces  of the folds of the  membrane  are
highly vascular, and the majority of the capil-
laries spread  out upon  them  are probably
venous.   Thus the surface  of the umbilical
vesicle is  enormously increased  in  extent, in
a manner  precisely similar  to that in which
the mucous membrane of the intestines is ex-
tended  by the arrangement of  the  valvulae
conniventes.    Such is  the character  of  the
vascular surface by  which  all  the nutritive
constituents  of the yolk are  absorbed, which
are afterwards carried to the system of the
chick for its nutrition, throughout  the whole
period of development within the shell.  That
portion of the yolk nearest to the vessels becomes quite fluid, ana is
 Folds of the vitellary mem-
brane and vasa lutea (after
Mr. Dalrymple), showing ar-
rangement of the  vessels.
From the chick. 
894
DEVELOPMENT.
therefore in a state most favourable for absorption;  it also becomes
mixed with the albumen, by which it was originally surroundt-d, and
which enters by  endosmosis through  the yolk membrane ; and  it
undergoes certain chemical changes,  as the experiments of Dr. Prout
have shown.
  We have already shown (page 866) that the yolk is in direct con-
tinuity with the cavity of the intestine, through the intervention of
the vitelline duct; and it is therefore possible for the nutrient mate-
rial to reach the system of the chick, by this  shorter and more sim-
ple course, at a very early period of development.   Although there
can be  no doubt of the existence of this tubular communication at
one time, it is nevertheless quite certain that, throughout the greater
part of the period of incubation, the duct  is impervious,  and the
nutrient material  of the yolk is  absorbed by the vessels ramifying
upon the  surface of the umbilical vesicle, and is carried, by the om-
phalo-mesenteric vessels, to the vascular system of the embryo in the
manner above described.
   The yolk-sac of the  mammalian ovum has  a structure very similar
to that  of the bird.  The communication with the intestine is at first
very wide, but  soon becomes reduced to a narrow tube, the omphalo-
mesenteric or vitelline  duct.  The umbilical vesicle generally disap-
pears at a very early period; and in the embryo calf, not more than
six lines in  length, according  to Bischoff, it is only connected with
the embryo  by a thread-like pedicle, and is  of very small size.   In
the frog it disappears  very early, while in carnivorous  animals, and
also in  the rodents, it remains throughout a considerable period of
intra-uterine life, and is very highly vascular.
   The vessels of the umbilical vesicle are well shown  in an embryo
of Dr.  Sharpey's.  The foetus was 1^ of an inch in  length.  The
vesicle was T4D  of an inch in diameter, and the pedicle  T7n of an inch
long.  A beautiful engraving of this  embryo will be found in Muller s
Physiology, translated by Dr. Baly.
   In the human embryo of from two to three lines in length, Muller
found the duct of  the umbilical vesicle very short and wide, and was
able to  trace its walls in direct continuity with those  of the intestine.
Dr. Allen Thomson also  testifies to the same fact, and Weber has
delineated its bloodvessels.  It is very distinct in the human embryo
about the twentieth day.  It lies between the chorion and amnion,
and is filled with a yellowish-white yolk.   By the third month, it is
about four or five  lines in diameter; and from this time it becomes
smaller, and gradually disappears.   Mayer has,  however, detected
both  the vesicle  and  its  thread-like  pedicle at the full  period  of
gestation.
   Development of the Allantois.—At a very  early period of develop-
ment of  the mammalian  embryo,  a collection of  cells makes its
appearance upon the anterior surface of its caudal extremity.  This
gradually increases in  size, becomes  flask-shaped, and a cavity in the
interior of the mass becomes visible.   The vesicle thus formed rapidly
enlarges.  It contains  fluid, and upon its  surface, vessels, which ulti-
mately  become the umbilical vessels,  are seen  ramifying.  As  it 
ALLANTOIS.
895
grows, these vessels are  carried with
the  chorion.   The  vessels  of  the
umbilical  vesicle  waste   with  this
structure,  while those conducted to
the  placenta by the allantois, ulti-
mately become  the  two umbilical
arteries and the  umbilical vein.   In
the  human embryo, the  chief office
of the allantois seems to be that of
conducting the vessels towards that
portion of the  chorion which is to
become  the  future placenta;  and
as soon  as the  connection  between
the  foetus  and the  placenta is esta-
blished, which in the human embryo
takes  place between  the third and
fourth weeks,  the  allantois  is  no
longer distinguishable. Besides this
office, however, the allantois receives
the secretion from the  temporary
kidneys, or corpora Wolffiana, pre-
 vious to the formation of  the per-
 manent structures.

   In many  of the lower animals, however,
 the allantois is developed to a much greater
 extent than it is in man.   In birds, and in
 several mammalian orders, it forms a very
 large sac, which completely surrounds the
 embryo; and in the ruminants,  it contains
 many quarts of fluid,  towards the  termina-
 tion of intra-uterine life.
   The allantois in the  chick is readily dis-
 tinguished before the close of the third day,
 and appears to be connected with the termi-
 nal portion  of the intestine.  Reichert has
 carefully investigated its  development, and
 has  shown that it is not developed from the
 intestine or from the membrana intermedia,
 but  arises from two masses of cells, situated
 at the posterior extremity of the Wolffian
 bodies, which afterwards  coalesce, forming
 a pear-shaped mass, in which a  cavity soon
 manifests itself.  Passing from the Wolffian
 bodies to the two small masses above referred
 to, are two lines or threads, which ultimately
 become the excretory ducts  of  the former
 organs.
   At an early period, the allantois communi-
 cates with a common cavity,  or  cloaca, into
 which the ureters, the excretory ducts of the
 Wolffian bodies, and those of the organs  of
 generation  open.  This is called the  sinus
 urino-genitalis.   The  allantois  grows very
 rapidly, and ultimately entirely envelops the
 embryo with its  amnion and  yolk  and
 becomes applied to the inner surface of the
it  towards the inner surface  of
Fig. 292.
  Diagrams to show the arrangement of the
allantois, and the formation of the placenta in
different classes of animals:—
  a. A portion of the wall of the uterus, b.
Chorion,  c. Allantois.  d. Umbilical vesicle.
e. Amnion.
  A. In ruminants. The cotyledons, spread
out over the internal surface of the uterus, fit
into cup-shaped cavities formed by the altered
chorion.  The allantois is of a very large size,
and entirely surrounds the embryo.
  b. In the ferse (cat, etc.), the placenta forms
a zone which surrounds the embryo like a ring.
There are no cotyledons.
  c. In rodentia  and in the human subject.
The placenta is limited to one particular part
of the chorion. The allantois is very small,
and only distinguished at a very early stage. 
896
DEVELOPMENT.
membrane of the egg-shell.  It is highly vascular, and is, in fact, the respiratory
organ of the chick as long as it remains within the shell.
  The arrangement of the capillaries has  been investigated by our friend, the late
Mr. Dalrymple, who has made some very successful injections of the allantois of the
chick.  On the outer surface (that which is in immediate contact with the membrane
of the shell), the capillaries are exceedingly abundant and very minute.  Mr. Dal-
rymple compares their arrangement to that of the vessels in the air-cells of the lung
of reptiles—a resemblance of  great interest, when we consider that in the bird this
membrane performs a most important part in aerating the blood; indeed, it is through
the intervention of the allantois that all  the respiratory changes taking place in the
chick are carried on.  The air passes through the  pores in the shell and membrane
beneath, and thus is brought into contact with the  blood ramifying in the vessels of
the allantois.
  The allantois, as was shown by Reichert and others, is connected with the efferent
ducts of the Wolffian bodies, and receives the secretion from these glands.

   In the human  subject,  soon  after its formation,  a dilatation  is
observed in that  part of the  allantois  nearest the fcetus.   This  is
the rudiment of the urinary bladder.  Just at  the junction between
the vesicular portion  and the straight tube which passes from  this
point to the chorion, a folding or constriction  occurs.   This indicates
                                               the first formation of the
Fig. 293.
  Diagram of uterus, with a fully formed, but very young
ovum. a. Plug of mucus occupying cervix uteri, b. Opening
of Fallopian tube. c. Decidua vera. d. Cavity  of uterus,
nearly filled with ovum.  e. Decidua reflexa. k. Chorion.
/ Decidua serotina. g. Allantois in situation of placenta,  i.
Amnion,  h. Umbilical vesicle. 11. Umbilical cord. 12. Space
between chorion and amnion, filled with albuminous matter.
urachus, which has been
erroneously considered to
be  situated in that  part
between  the vesicle and
the  foetus.   This latter
portion,  however,   soon
becomes divided into two
tubes,  one  being   con-
nected with each Wolffian
body.  These  tubes  are
ultimately converted into
the  ureters.   The  ure-
ters and  urinary bladder
are gradually drawn into
the  cavity of the pelvis,
through   the   umbilical
opening.   This   process,
according to Langenbeck,
is completed between the
twelfth   and   twentieth
week.   The urachus, be-
tween the bladder  and
umbilicus, remains tubu-
lar  long  after this,  and
even at birth in some few
instances; in which  cases
urine has been known  to
escape  from  the umbili-
cus.
   Allantoic   Fluid   is
 clear, of a brownish yel-
low  colour.  Its specific 
UMBILICAL CORD.
897
gravity varies from 1005 to 1030.  It contains alkaline  lactates,
extractive matters, and ammoniacal salts, with alkaline and earthy
phosphates, and chloride of sodium.  Besides  these, however,  there
is  a definite crystallizable  substance peculiar to this  fluid, termed
allantoin, which is closely related  to uric  acid; indeed, it may be
prepared  artificially from this substance, while  urea is produced at
the same time.   The composition of allantoic  fluid seems nearly
identical with that of the urine of calves  while suckling, at which
time it contains no hippuric acid.  This latter  substance, however,
makes its appearance in the urine  as soon as the animal takes vege-
table food.   Uric acid has been found in the allantoic fluid of birds
by Jacobson.
   Velpeau held that the allantois completely surrounded the human
 embryo, as it does in many animals; but  this  statement  has  been
 completely refuted by the researches  of Muller, Bischoff, Langen-
 beck,  and others.
    Umbilical Cord.—The umbilical cord is  the long, narrow pedicle,
 contained in a tube of  the amnion, which  connects the foetus with
 the placenta.   In the advanced embryo, it consists  principally of
 the large vessels,  through the  intervention  of which all the nutrient
 material absorbed from  the blood of the mother is conducted to the
 system of the foetus.
    At  an earlier period of development, the cord is really composed

    1.  The remains of  the  omphalo-enteric duct, or  pedicle of the
 umbilical vesicle.
    2.  The vasa omphalo-meseraica, or  branches of  the  mesenteric
 vessels of the foetus.
    3   The urachus, and all that remains of the allantois.   ^
    4  The umbilical vessels ; consisting of  one umbilical vein, which
 brings the blood back from the placenta, and two umbilical arteries,
 by which the blood is carried  to the placenta.     _
    In  animals generally,  however,  there are two veins, as well as two
 arteries, which are the chief branches of the hypogastric  arteries of
 the fcetus.  The  circulation of the foetus has been fully described in

 mBirth.—In the human subject,  the period of pregnancy lasts about
 nine  solar, or ten lunar months, or 280 days.  It varies, however,
 within certain limits.                                .   „ .      ,
    The  phenomena of parturition are specially treated of in works
  on Midwifery; so that a very brief reference to this part  of the sub-

 ^1.^^^ of the contraction of the  uterus  little i.
  known   Valentin attributes  it to the excitement of the organs which
   iry^xltsat\he menstrual periods; and  ne considers t  at pa.
  tnrition takes place at the tenth menstrual period.  Dr. lyler bmitn
  tuntion takes pia                 ^.^  ^ ^ contractl0ns of
  t\l7us are duTto the increased action of the ovaries operating
        tWord through the  ovarian nerves, which act as exciters;
  IZe the uterus is thfrown into contraction through the medium of 
898
LACTATION.
the uterine nerves, which are therefore to be regarded as the motor
nerves concerned in this reflex  action.  The action of the uterus is
no doubt in part due to the stimulus produced by the increasing bulk
of its contents.
  The foetus lies in utero with its head downwards during the later
months of  pregnancy.   The contraction of the thick muscular walls
of the uterus tends to force the head upon the os uteri, in conse-
quence of which the circular fibres of the latter gradually relax, and
the opening dilates.  The membranes are pressed towards the vagina,
and protrude through the  os,  until at  length  they burst, and the
liquor amnii escapes.
  At each successive pain, the child's head is forced lower and lower
into the vagina.  The  pains increase in  force and frequency, and
the uterine contractions are assisted by the voluntary contractions  of
the abdominal muscles ; until at last, in a violent paroxysm of pain,
the head is born, and the remainder of the child very quickly follows.
  A little hemorrhage usually occurs  immediately  after the  birth  of
the child, in consequence of the partial detachment of the placenta.
This is followed, however, by contractions; and the  placenta itself
is forced into the vagina shortly after  the birth of  the child.  With
the placenta are also expelled portions of the membrana decidua, the
remains of the chorion, and the amnion.
  After labour, a considerable quantity of fetid discharge takes place
from  the uterus.  At first, this is  composed principally of blood ;
but afterwards it becomes paler, and consists  chiefly of  mucus, with
pus  corpuscles,  and a certain  quantity of  fluid  exudation.   The
uterus gradually returns to its former volume.

  For information upon the questions discussed in the present chapter, the student
is referred to the works previously enumerated.
                       CHAPTER  XLIV.

OF  LACTATION.—THE LACTEAL  GLANDS.—NIPPLE.—MINUTE STRUC-
    TURE OF THE GLAND.—BLOODVESSELS.—ABSORBENTS.—MILK.

  The Lacteal Glands  are two large, symmetrical organs, which are
only fully developed  in the  female.   In the  male, however,  they
exist in a very rudimentary state.  During the  later half of preg-
nancy, the lacteal  glands increase very much in size ;  and about the
period of parturition, they begin to secrete milk.  They are racemose
glands, and are ultimately composed of numerous roundish follicles,
arranged round the terminal extremities of the ducts.
  The structure of  the lacteal glands formed the subject of a very
important investigation  by Sir Astley  Cooper. 
LACTEAL glands.
899
  The lacteal  tubes  are about twenty in number, and terminate at
the extremity  of the nipple,  by as many orifices.  The ducts are
Fig. 294.
 Preparation with six milk-tubes injected from the nipple, by Sir Astley Cooper.—a. The straight
or mammillary tubes, proceeding from the apex of the nipple, b. Reservoirs or dilatations of the
ducts,  c. Branches of the mammary ducts, d. Glandules.

dilated as they approach the nipple, and  the  dilatations  are called
reservoirs.   In the human subject,  these are very small;  but in the
cow, they are large enough to hold  a quart.
  The nipple  is  surrounded by a  dark coloured circle, termed the
areola, smooth  in the child, but  slightly tuberculated at the period
of puberty.   In  the  child it is about half  an inch in diameter; but
in the adult, about an inch; while  during lactation, it increases to
two inches.   After impregnation, it changes from its reddish colour
to a dark brown.
  A secretion  is poured out from the mucous  follicles, which  lubri-
cates the skin about the nipple.
  The terminal  follicles of the  gland were injected by Mascagni;
but for almost all that we know of the minute anatomy of the breast,
we  are indebted  to  the  beautiful  researches of Sir Astley Cooper,
published in 1840.
  The surface of the breasts, in the unimpregnated state, is smooth
and compact;  but as pregnancy advances, they become  uneven, in
consequence of the distension of  the follicles with  secretion.
  The nipple,  before  puberty,  forms  an  almost  smooth conical
eminence* but in lactation it becomes flattened, so  that its extremity
becomes  the broader part, and  thus it is  more readily held by the
child's mouth.   Its characters  have been minutely described by Sir
Astley Cooper:  "At sixteen years it is slightly wrinkled; at seven-
teen it  has small papillae upon its  surface;  from  twenty to  forty
years  the papillae are large ; from  forty to fifty, the nipple becomes 
900
LACTATION.
wrinkled; from  fifty to sixty,  the  nipple is- elongated; and in  old
age, it usually has a warty appearance."
  The cutis of the nipple contains a great number of papillae.   It
is  sensitive  and highly vascular.   "The direction of these papillae
is from the  base  towards the apex of the nipple ;  so that they are
pushed back as the mammilla enters the mouth of the child, and thus
greater excitement is  produced."   Connected with the cutis of the
nipple are numerous non-striated muscular fibres, to the presence of
which  the erection of the nipple is  due.
   In their  minute structure, the lacteal glands are closely allied to
the pancreas and salivary fluids.
   The  gland  structure is  arranged so as to form lobules, which  are
connected together with a considerable quantity of firm areolar tissue
(p.  87).
  The terminal follicles are about the 3 J-^th of an inch in diameter.
They are lined with a layer of delicate epithelial cells, which become
much altered  at  the time of lactation.   At  this  time the  cells
                                   become larger and much  more
             Fig. 295.               numerous.    They contain  a
We have searched for them carefully, but with no better success.
  The bloodvessels are  very numerous,  and  their  finer branches
ramify around the terminal follicles of the gland.
  The absorbents  have been injected  by Sir  Astley Cooper, who
describes  a superficial set  beneath the  skin,  and a  deeper set of
trunks which penetrate into the substance  of the gland, and form a
plexus of  great beauty in the interior.
  In  the male, the lacteal glands exist only in a very rudimentary
condition; but their  structure  is precisely similar  to those of the
female, as Sir Astley Cooper demonstrated.   In a  few  very rare 
FOLLICLES OF MAMMARY GLANDS.
901
instances, they have been  unusually developed;  and  instances are
even on record, where milk has been secreted by the  lacteal gland
Fig. 296.
 Terminal follicles of the lacteal gland, with ducts, from a woman who was not pregnant. The
fibres of yellow elastic tissue are numerous upon tho wall of the duct. The terminal follicles are
separated from each other by a considerable quantity of areolar tissue.  Magnified about 150 diameters.

of the male; indeed it has been  related by Humboldt, that the infant
has been nourished by the male  parent after the death of the female.
   The  lacteal  glands  are  developed
like  other glands  connected  with the
skin.    In the  fourth  or fifth  month,
according to the observations of Langer
and Kolliker, a papillary projection of
the  mucous layer* of  the  epidermis
occurs.   This  increases in size; and,
by the  sixth or seventh month, throws
off a number of  offsets,  from which
the lobes of the gland are gradually
formed.
   Milk  is  white  and  opaque,  from
the presence  of numerous oil-globules.
Besides  these, which are  held  in sus-
pension, and are  insoluble, milk  con-
tains numerous  nutritious substances
which   exist  dissolved   in  the  fluid.
After it has been  allowed  to stand for                             .
some time, the  oil-globules rise to  the surface, by  reason of  their
lightness, forming the cream.
 °     58
 Lacteal gland of a newly-born child.
The rudimentary follicles are well shown.
After Langer. 
902
LACTATION.
   Milk usually does not obtain its normal characters until three or
four days  after delivery.   The first  proportion, which is secreted
                  before parturition, is thinner, and contains but a
                  quantity of saccharine and oily materials.  In it
                  albumen is often detected.    This is  called  the
                  colostrum.   The specific gravity varies from 1020
                  to 1045.
                     The  oil existing  in  milk, occurs in  a state of
                  minute  division, in the form of oil-globules, which
                  are equally diffused throughout the fluid.   These
                  oil-globules  are  each  invested with  a delicate
                  membranous envelope, composed of caseine, which
                  prevents  their  running  together.  If  milk and
                  ether be  shaken and well mixed, the  oily con-
                  stituents are not dissolved, in consequence of  the
                  envelope   of caseine  with  which  they  are  in-
vested ; but if, previous to the addition  of the  ether, a little acetic
acid or alkali, or alkaline salt, which has the power of dissolving  the
covering, be added, the globules are immediately dissolved, and  the
milk  becomes  perfectly  clear.   By  churning,  the  envelopes  are
ruptured,  and  the  oil-globules  are made  to run together, forming
butter.
   If the slightly  turbid solution from  which the cream  has  been
removed be allowed to stand  for some time, or if an acid be added to
it, a flocculent  precipitate  occurs.   This is  caseine, which is coagu-
lated by all acids.   It  is, however, not  coagulated  by  heat;  but
during evaporation, a scum forms upon the surface of solutions con-
taining caseine.
   The following analyses  show the chemical composition of human
milk.  Specific gravity, 1030—1034.
 a.  Colostrum corpus-
cles.  6. Milk globules.
In the lower part of the
figure, two are seen run-
ning  together, in conse-
quence of the investing
membrane having been
dissolved.    Magnified
about 215 diameters.
Colostrum.	4 days after
	parturition.
Water . . . 828-0 . . .	879-848 . .
Solid matter . 1720 . . .	120152 . .
Albumen . . 40 0 caseine	35-333 . .
Butter . . . 50-0 . . .	42-968 . .
Sugar of milk. 700 . . .	41-135 . .
Salts ... 3-1 .. .	2-095 . .
9 days.	12 days.	Average
885-818 .	905-809 .	891 -0
114-182 .	94-191 .	109-0
36-912 .	29-111 .	33-7
35-316 .	33-454 .	37-1
42-979 .	31-537 .	38-5
1-691 .	1-939 .	1-9
   The first two analyses are by Franz Simon, and the last three by
Clemm.
   Cow's milk contains more caseine and less sugar than human milk.
Ass's milk contains  less butter and less  caseine, but more suo-ar;
while in goat's  milk the caseine preponderates over  the other  con-
stituents.  L'Heretier has shown that temperament exerts an influ-
upon the character of the milk.  The average quantity of  solid matter
in 1000 parts of milk from  fair women, was  120 grains; and  of
brunettes, as much as 134 grains.
   The characters of  the milk, also,  it need hardly be  said, are much
influenced  by the health and  diet of the mother, and  by the age of
the infant.  At first, the caseine is small in quantity,  and  gradually
increases up to  its normal  standard; while, on the* other  hand, the 
MILK.
903
proportion of sugar is very large at first, and subsequently diminishes
in quantity.   The proportion of butter varies considerably.   Phos-
phate of lime is very soluble in solutions of caseine, and in this way,
no doubt, is introduced into the system of the young animal.
 ^ In disease, the milk may  contain blood, pus, or mucus, and occa-
sionally lactic acid and albumen have  been detected in it;  urea and
bile-pigment have also been found  in milk.

  Upon  the subject of lactation,  the student may refer to the  following:  On the
Anatomy of the Breast, by Sir Astley Cooper, 1839.  C. Langer, Ueber den Bau und
die Entwicklung der Milchdrusen, mit 3 Taf.,  Denkschr. d. Wiener  Akad.  Bd. iii.
Wien. 1851.  Article "Mammary  Gland," by Mr. Solly, in  the Cyclopaedia of Ana-
tomy and Physiology.  And Simon's Animal Chemistry, translated by the Sydenham
Society. 
 
INDEX.
Abdominal, muscles, influence on vomiting,
  564, action of, in defecation, 608 ;  respi-
  ration, 718
Absorbents,  minute  anatomy of,  613; con-
  tractility of, 615 ;  contents of,  619 ; func-
  tion of, 627 ; viewed as a glandular system,
  627 : of lacteal glands, 900
Absorption, 611; influenced by motion of the
  fluid, 626 ; by pressure, 625 ;  by porous
  solid, 624 ; by quality of fluids, 623 ;  me-
  chanism of, 622 ;  of chyle by villi, 578 ; of
  gum, sugar, alcohol, etc., 578 ; of tissues,
  611; by bloodvessels, 619 ; by the stomach,
  562,  588 ; and secretion in the  skin, 372.
Aealephffl, 823; renal  organs of, 786;  re-
  production of, 825
Acervulus, 252
Acetic acid, action of; upon wall  of Pacinian
  corpuscles, 347 ; upon epidermis, 362
Achromatism of eye, 432
Acids, effect of in digestion, 555 ; nature of,
  in gastric juice,   557;  lactic, in  gastric
  juice, 558
 Action of heart, 672
Adaptation of eye to vision at different dis-
  tances, 429
 Addison, Dr. W., on fibrin of blood, 634; on
  lobular passages, 712 ; on supra-renal cap-
  sules, 815
 Adipose tissue, 88;  vesicles, 89;  bloodvessels
   of, 90; development of, 93; subcutaneous,
   354
 Admirault on taste, 386
 Aerial capacity of lungs,  722
 After-tastes. 390
 Age, influence of; upon animal temperature,
   736; upon  quantity of carbonic acid ex-
   pelled, 726
 Aggregate glands, 583
 Air, accumulation  of in stomach, 563;  a-
   mount breathed,  722 ;   changes of,   in
   respiration, 723 :  expired, volume of car-
   bonic acid in, 724 ;  residual, 722; respired,
   temperature of, 723
 Air-cells, 709                 l  . A,      ..
 Albinus, on  the muscular  coat  of the  small
   intestines, 572
 Albinos, light painful to, 4^54     ..
 Albumen, 53 ; acted on by gastric juice, 555 ;
   digestion of,  555
 Albuminous aliment, 515
 Alcock Dr., his experiments on taste, 387,
   on  glossopharyngeal, 388;   on sensation

 AlcdSts6 influence on respiration, 725 ; on
  retarding digestion, 562 ; its action on gas-
  tric juice,  557
Alexis St. Martin, 561
Alimentary  canal,  development of,  883 ;
  mucous membrane of,  522 ;  compartment
  of pharynx, 541
Allantoic fluid, 896
Allantoin, 897
Allantois, 871,  894;  development of, 881.
Allen and Pepys; on the quantity of carbon
  removed from the body, 730 ;  on the pro-
  portion of carbonic acid in expired air, 727
Alto voice, 754
Alveolus, 526, 532; of lung, 712
Amaurosis, 433
Ammoniacal salts in urine, 802
Amnion, formation of, 869, 892
Amphibia, generative organs of, 828 ; organ
  of hearing of, 443
Amphioxus  lanceolatus,  nervous system of,
  276
Ampullae, 450
Amylaceous substances not digested by sto-
  mach, 588
Analysis, of blood,  quantitative, 643 ;  of
  blood of dog under the influence of vene-
  section,  646 ;  of  milk,  .902 ;  of ox-gall,

  598                         , T   .
 Anastomosis, of arteries, 656 ; of Jacobson,
  447 ; of nerves, 201 ;  of third nerve, 474
 Anderson, Dr., experiments on vomiting, 564
 Andersch, on the ganglion petrosum, 485
 Andral, cases of lesion of optic thalamus and
   corpus striatum, 311
 Andral and Gavarret, on the influence of age
   upon the exhalation of carbonic acid, 726
 Anencephalic  foetus, movements of, 278
 Animal heat, 733 ; influence  of, on nervous
   system. 742 ; theory of, 740
 Annelida, liver of, 770 ;  renal organs of, 786 ;
   reproductive of 820 ;  sexual apparatus of,
   825
 Annulus ovalis, 666
 Anaemia, value of iron  in  the  treatment oi,

 Ant-eater,  tongue of, 524;  teeth of, 526
 Anterior, chamber,  420 ; columns of  cord,
   282  ; venous trunks, 882
 Antero-lateral columns of cord, function  ol,
   284, 285
 Anthelix, 444
 Antiperistaltic action, 584
 Antiseptic power of bile, 598
  Antitragus, 445
  Aorta, origin of, 656 
906
INDEX.
Aortic arches, 882 ;  development of, 880
Aphis, metagenesis in, 823
Aponeurosis, 81
Appendices  epiploicae,  568 ;  pyloricas,  in
  fishes, 569
Appendix cseci vermiformis, 567
Aqua Morgagni, 418
Aqueductus,  cochleae, 452 ;  Fallopii,  447 ;
  course of portio dura nerve in, 477; Sylvii,
  261
Aqueous,  alimentary materials,  group  of,
  515 ; vapor, exhalation of, 724
Arachnida, circulation of, 706 ; renal organs
  of,  786
Arachnoid membrane,  230;  subarachnoid
  cavity,  231
Area,  germinativa,  859 ; pellucida,  863;
  vitellina, 864
Areola of nipple, 899
Areolar, framework of skin, 356; tissue com-
  posed of white and yellow fibrous tissues,
  84 ; its  corpuscles, 84 ;  development, 85 ;
  its cellular spaces, 85;  its association with
  bloodvessels,  86 ;   distribution,  86 ;  and
  use, 87  ; modifications of its elements, 87 ;
  in serous membranes, 129 ; physical pro-
  perties, 88;  of  muscles,  159;  beneath
  mucous membrane, 572; of pharynx, 542;
  sub-basement, 524
Argonaut, sexual apparatus of,  826.
Arnold, Bischoff and Bendz,  on the spinal
  accessory nerve, 496
Arnold, on  the  otic  ganglion, 501; on the
  branch  of nerve from the otic ganglion to
  Tensor  tympani,  453 ; on development of
  teeth, 532
Arterial, system, 655; blood, 629 ; and ven-
  ous blood, 645
Arteries, 649 ; development of, 870 ; branch-
  ing and anastomosis of,  656 ; external coat
  of,  650  ; middle coat  of, 650 ;  epithelial
  layer, 653 ;  nerves of,  655;  vasa vasorum
  of, 650; of choroid, 407 ; of penis, 546 ;  of
  stomach, 546
Artery,  hepatic, 774 ; posterior communica-
  ting, 264 ;  pulmonary,  707 ;  splenic, 810.
Articulata, digestive organs of, 514; circu-
  lation in, 697
Articulation of lower jaw, 538
Artificial,  digestive  fluid,  557;  division,
  multiplication by, 820
Arum maculatum, temperature of, 733
Arytenoid cartilages, 746
Ascaris dentata, cleavage of yolk in ovum of,
  856 ; nigrovenosa, cleavage of yolk in  ovum
  of, 856
Ascidia, heart of, 663
Asellias, the discoverer of lacteal vessels, 612
Asphyxia, circulation in pulmonary  capil-
  laries in, 699
Ass' milk, 902
Assimilation, 34
Astacus fluviatilis, spermatozoa of, 836
Asthma, nature  of, 493;  following section of
  vagi,  492
Atrophy of glands in advancing life, 611
Attention, its importance  in vision, 436
Attitude,  183 ; standing,  184 ;  walking, 185
Auditory  canal, 445
Auricle of ear, 444 ;  use of, 464
Auricles  of .heart,  664 ; muscular fibre of,
  671 ;  suction  power of, 702
Auricular appendage, 665
Auriculo-ventricular orifice, 664
Autenrieth,  on the  use of the semicircular
  canals, 472
Aves, generative organs of, 828
Axial reversed current, 585
Axilla, sweat glands of,  368
Axis cylinder, in Pacinian corpuscles, 348
Azotized substances, absorption  of  by sto-
  mach, 588

Babinoton, Dr., on the cause of buffing and
  cupping, 632
Baer, Yon, on development of superior max-
  illa, 877; on the formation of the amnion,
  869
Bagge, on the development of ova of intes-
  tinal worms, 841
Baly, Dr., on taste, 388
Barral,  M., on ingesta and egesta, 76] ; on
  the quantity of carbon removed by respi-
  ration, 731
Barry, Sir David, on the influence of respira-
  tion on the circulation, 701
Barry, Dr., on the changes in the germinal
  vesicle,  855; on  the impregnation of the
  ovum, 853 ;  on retinacula, 840
Bartholini, glands  of, 845
Basement membrane, 61,  129, 523; of sto-
  mach, 547 ;  of sweat-glands, 369 ;  of villi,
  577
Bass voice, 754
Bat, circulation in wings of, 703; sense  of
  touch in the wings of, 373
Batrachia, intestinal canal of, 569
Beaver, epithelial secretion of penis,  835
Beale. Dr., his analysis of dog's blood, 646;
  of healthy kidney, 786 ; liver, 768 ; thyroid,
  816 ; on chlorides in the urine,  802; mode
  of injecting the  tubular network  of the
  liver,  780 ;  on the relation of the  hepatic
  ducts  to the liver cells,  782;  on parietal
  sacculi, 776 ; examination of liquor amnii,
  892
Beau, on ordinary respiration, 718
Beaumont,  Dr., on changes in mucous mem-
  brane of the stomach, 551 ; on  the rate of
  digestion, 561
Beccaria, on  glutinous  portion of the  food,
  515
Beck, Dr. T. Snow, his dissection  of the sym-
  pathetic, 499;  on  nerves  of  the uterus,
  844
Becquerel, and Breschet, for the temperature
  of internal  parts of the  body, 735 ;  and
  Itodier, their analysis of the blood, 644
Bell, Sir Charles,   on the fourth nerve  in
  apes,  476 ;  on the functions  of  roots of
  nerves, 274; on the spinal accessory nerve,
  497
Belladonna, effects of, upon the cord, 282
Bellini,  tubes  of, 789
Bellows murmur, 674
Bennett,  Dr. Hughes,  on leucocythemia,
  648 ;  on the spleen, 810
Benzoic acid formed from hippuric acid, 801
Bergmann, on the supra-renal capsules, 815
Bernard, on branches of the portal vein, 677 ;
  on the digestion  of fat,  594; experiments
  on the functions  of the liver, 604; on the
  influence of the  nervous system upon ani-
  mal heat, 743 ;  on pancreatic juice,  592 ; 
INDEX.
907
  and Barreswil on the action of pancreatic
  fluid on starch, 589 ; on the  acid of the
  gastric juice, 558 ;  on the spinal accessory,
  496 ; and  Blondlot upon the acid fluid of
  the caecum,  608
Berzelius, his analysis of faeces, 609 : analy-
  sis of lens, 420 ; analysis of ox-gall,  598 ;
  of vitreous humour, 417
Besoin de respirer, not destroyed by section
  of vagus,  492
Bichloride of mercury, its action on digestive
  fluid, 557
Bidder, on the quantity of lymph, 622 ;  and
  Schmidt on the quantity of bile, 784
Bicuspid teeth, 527
Bile,  escape  through a  fistulous  opening,
  597;  colouring matter  of, 599;  fat  of,
  598 ; its escape favoured by digestion, 597;
  influence  on coagulation  of blood,  632 ;
  not exclusively an excretion, 602 ; passage
  into ducts,  784;  physical and  chemical
  characters of, 598 ; quantity of, 597, 784;
  in  human faeces, 602 ;  uses  of,  600 ; se-
  creted from portal blood, 596 ; saline con-
  stituents, 600 ;  pigment  in milk, 903
 Bilifellinic and Bilicholinic acids, 599
 Bilin, 598
 Biliverdin,  599
 Bill of birds, 524
 Biot, M., on  the detection  of sugar by the
   polariscope, 561;  on propagation of sound,
   463
 Biphosphate of lime in gastric juice, 557
 Birds, aortic arches of, 882; blood corpuscles
   of,  635;  circulation  of,  707;  cochlear
   nerves in, 457; digestive organs of,  513
   crop of, 513 ; early changes in egg of, 863
   intestinal canal  of, 569;  heart  of,  663
   organ of hearing of, 444 ; sympathetic in
   498 ; uric acid in allantoic fluid  of, 715
   vessels of lung of, 897 ;  villi of,  576 ; vocal
   organs of, 745
  Birth, 897
  Bischoff, on the amnion, 892; on  formation
   of corpora lutea, 851 ;  on formation of
   blastodermic vesicle, 857; on impregnation
   of  ovum, 853 ;  on stellate cells of zona
   pellucida, 855; on the  development of the
   eye, 879; tunica  media of, 874 ; and Vogt
   on the pulsations of the heart before the
   formation of muscular fibres, 882
  Bishop, on the production of falsetto  notes,
   754
  Bladder, 804 ; development of, 896 ; forma-
   tion of, 874
  Blagden, Sir Charles,  experiments on  the
   effects of a high  temperature on  the body,
   737
  Blainville, De, on the perilymph, 453
  Blake, on  the heart's force, 689 ; on the rate
   of the circulation, 705          _
  Blastodermic vesicle, 858 ;  formation of, 857
  Blindness, coincident with disease  of corpora
    quadrigemina, 313       ...   -,,-
  Blondlot, on acidity of gastric juice, 557; on
    escane of bile, 596 ; on use of bile, 602
  Blood  628;  analysis  of, 643; arterial and
    venous, 629,  645 ; buffing  and cupping
    RS9 •  niinnp-es in, from  respiration,  728 ,


    quantity of, 630; red  corpuscles of, 634;
  serum of, 633 ; specific gravity of, 628 ; in
  anaemia and  after hemorrhage, 633 ; in-
  crease  of  fibrin  in, 647 ;  in  intermittent
  fever, 648;  in gout,  648 ;  in  rheumatic
  fever and pneumonia, 647; physical analy-
  sis of, 629 ; temperature of, 645 ;  urea in,
  800 ; of spleen, changes in, 813;  of vena
  portae,  645
Blood corpuscles, aggregation of, 635 ; colour-
  less, 637 ;  development and decay of, 642 ;
  generation of, in the  liver, 606;  of birds,
  635 ;  of camelidae, 635 ;  fishes,  636;  of
  invertebrata, 636 ;  in animals, 635 ;  rep-
  tiles,  635 ;  function  of,  640 ;  nature of,
  636 ; origin of, 639 ;  of spleen pulp, 808 ;
  structure  of,  636
Bloodvessels, 649 ;  of adipose tissue, 90 ;  of
  bone, 110; of brain, 263;  of cartilage, 99;
  of fibrous tissue, 80 ;  of lacteal  glands,
  627 ;  of meninges, 228 ;  of  muscle,  159 ;
  of nerves, 200;  of  pulp cavity,  532 ;  of
  villi, 577
Blubber, 356
Blumenbach, cases of congenital deficiency
  of tongue, 387
Blushing, 697
Boa, circulation in kidney of, 796
Body of lens, 418 ; of tooth, 526
Boerhaave  and Bressa, on the use of the
  Eustachian tube, 469
Bone, 102 ;  physical and chemical properties,
  103, 105 ; rickets and mollifies ossium, 105 ;
  general structure, 107; long,  flat, and ir-
  regular, 107  ; Haversian canals, 110 ; gran-
  ules of the osseous tissue, 111; pores and
  lacunae, 112 ; lamellae, 114, 116 ; nerves,
   118 ; development, 118 ;  growth, 122;  re-
   paration, 125
 Boucbardat and  Sandras, experiments  on
   chyle,  588; on digestion of  starch, 561,
   589
 Bourgery, on inspired air,  723
 Brachet and  Dr.  J. Reid, on  influence of
   nerves in hunger, 521
 Brain, or encephalon, 237 ;  its four segments,
   237 ;  weight, 237 ;  association with mind,
   239 ;  circulation in, 263 ; is it compressi-
   ble ?  267;  functions of, 303;  capillaries
   of,  660; convolutions  of,  321;  effects of
   alterations of pressure upon, 268
 Branchiae, 706
 Branchial fissures and arcbes, 870
 Branching of arteries, 656
 Breschet, on the veins of bone, 110 ; on the
   temperature of internal  parts of the body,
    735 ; on the utriculus, 443
  Brewster, Sir David, on achromatism of  eye,
    432 ; on adaptation of eye to vision  at dif-
    ferent distances,  429 ;  on fibres of lens,
    419 ; on the refractive power of the lens,
    419
  Brinton, Dr., on inversion of the action of
    the stomach, 563 ; on antiperistaltic action,
    584
  Brodie, Sir B., on chyle,  621; experiments
    on digestion of fat, 561; on the  uses of the
    bile, 603 ;  on the influence of the nervous
    system in animal heat, 742
  Bronchi, 709
  Bronzing of skin by sun, 606
  Brown, Robert, on molecular motion, 71
  Brunn or  Brunner, on exhalation of aqueous 
908
INDEX.
  vapour, 724; on follicles of intestine, 573;
  glands of, 579
Bryozoa, digestive organs of, 514
Buchanan, Dr., on milky serum, 633
Budd, Dr. W., on spinal cord, 283 ; his case
  of paralysis, 283
Budge, experiments on cerebellum, 318
Buds, reproduction by, 820
Bulb of hair, 366  ; of olfactory process, 397
Bulbous portion of the urethra, 834
Burdach, on termination of nerves in skin,
  359
Bursa, 127 ; copulatrix, 827
Butter in milk, 902
Butyric acid, from action of pancreatic fluid
  on fat, 594

Cjsctm, 567; of birds, 569;  digestion in,
  608;  acid  reaction of  fluid of, 608;  in
  solipeds, 570 ; in herbivora and carnivora,
  608 ; large in herbivora, 571
Calcification of enamel, 530
Calorifacient food, 516, 740
Calyces of  the kidneys, 788
Camelidoe,  blood corpuscles of, 635
Camera obscura, 402
Campanularia  dichotoma,  development  of
  medusae from, 822
Camper on otoliths,  471
Canal of Petit, 417
Canaliculi, 426 ; of cementum, 531
Canine teeth,  526
Capacity, cubic of rooms, 728.
Capillaries, 659 ;  absorption by in stomach,
  562;  of brain, 266; and circulation in,
  rate of,  693, 694; of foetal tufts, relation
  to maternal vessels, 888 ; of lungs,  713 ;
  of lymphatic  glands, 616 ;  of olfactory
  region,  395 ; of optic nerve, 423 ;  of Pa-
  cinian corpuscles, 347 ;  of papillae, 359 ;
  portal  hepatic  plexus of, 769;  relation of
  tissues to,  660 ; of retina, 414; of villi,
  577
Capillary force, 695
Capsule,  of lens, 418;  of  Pacinian corpus-
  cles, 348 ; of spleen, 807
Caput, caecum coli, 567; gallinaginis, 832
Carbon, quantity removed from  body,  730 ;
  result of introduction of too much, 606
Carbonaceous matters eliminated by liver,
  606
Carbonic acid, exhalation of by lungs,  724 ;
  in intestine, 610 ; sources of,  731
Cardiac plexus, superficial and deep, 671
Cardinal veins, 881
Carlisle, Sir A., on the rete mirabile,  658
Carneae columnae, 665
Carnivora, Brunner's glands in,  579;  cho-
  rion in, 888;  intestinal canal  of,  569;
  Peyer's patches in,  582 ; sources of car-
  bonic acid in, 731;  stomach of, 513; urine
  of, 800
Carotids, 264
Carpenter, Dr.,  on  arrangement  of  liver
  cells, 780 ;  on  emotional fibres,  289 ;  on
  seat of emotional  influence,  314;  on the
  functions of the  white  blood  corpuscles,
  641;  on the nervous system,  290, 314 ;  on
  parthenogenesis,  822; and Mr. Newport,
  on  sensori-volitional and excito-motory
  fibres, 290
Carson, Dr., on resilience of lungs, 720
Carswell, Dr., experiments on digestion of the
  stomach, 554
Cartilage,  95;  temporary and  permanent,
  95, 118 ; structure of the varieties, 90 ; ves-
  sels of, 99 ;  of  ear, 444; of eyelids, 424 ;
  of larynx, 745 ;  of nose, 391; of trachea,
  708
Caruncle, 425
Carus, Victor, on metagenesis, 824
Caseine, 55
Castor, 835
Casts of uriniferous tubes, 798 ;  of foetus in
  liquor amnii, 893
Catalytic action of gastric juice, 559
Catalysis,  741
Catamenia, 847
Cauda equina, 270
Cavity of reserve,  537
Cells, development from, 63; nucleated, the
  most  elementary organic forms, 32, 61 ;
  transformation of, 63 ;  of the  colon, 572;
  of hair, 364 ; of liver, 779 ; of spleen pulp,
  808; of stomach, 547
Cellular coat of arteries, 650
Cement of teeth,  531
Centrum ovale of Vieussens, 253
Cephalopoda;  cleavage of yolk in, 856 ; di-.
  gestive organs of, 513 ; heart of, 663 ; renal
  organs of, 786 ; sexual organs of, 826
Cercaria, 823
Cerebellum, its connections, 320;  descriptive
  anatomy of, 245 ; functions of,  317; influ-
  ence upon locomotion, 285
Cerebral hemispheres,  253; circulation in,
  263 ; commissures, 257 ; convolutions,  254
Cerebro-cerebellar commissures, 260
Cerebro-spinal fluid, 231
Cerebrum, descriptive anatomy of, 250
Cetacea,  eye  of,  403;  intestinal canal of,
  571 ; olfactory nerves of, 312
Cerumen, of ear,  445
Ceruminous glands, 371, 445
Cervical glands, effects of enlarged, 493
Cervix of glans penis, 833 ;  of uterus, 842
Chamber of deputies, cubic capacity of, 728 ;
  anterior and posterior of eye, 420
Chara and valisneria, 697
Cheeks, 524
Cheiroptera, intestinal canal of, 570
Chelonia, generative organs of, 828;  intesti-
  nal canal of, 569
Chest voice, 753
Chevreul  on the  gastric juice, 559 ;  on the
  imbibition of fluids,  623
Chiasma of optic nerves,  421
Chick,  development of,  863; bile in  gall-
  bladder of, 813
Chloride of sodium, as a source  of the acid
  in the gastric juice,  554 ;  in liquor amnii,
  892 ; in urine, 802
Cholepyrrhin, 599
Cholera, Peyer's  patches in, 582;  tempera-
  ture of body in, 739
Cholesterine, 599
Cholinie acid, 598
Chondrine,  58
Chorda dorsalis, 868, 876
Chorda tympani,  478 ;  function of, 479
Chordae, tendineae,  664;  vocales, true  and
  false, 748
Chorea, 307, 316 ;  increase of sulphates in
  urine, 802 
INDEX.
909
 Chorion, 866; on papillary structure oftongue,

 Choroid, 407; of birds, 409
 Choroidal gland,  409
 Chossat, on effects of impaired nutrition, 521;
   on death from  starvation,  738
 Christison on the influence of venesection on
   the blood,  646
 Chromatic aberration, 428

 Ch9U0r2inS' CffeCt °f'  °n 0U Slobules of milk,
 Chyle  586, 587; analysis of, 622 ;  absorption
   of by villi, 578 ; corpuscles,  587 ;  fibrine
   in, 619 ; white  colour dependent upon oily
   matter, 621; and lymph, quantity of, 622 ;
   transparent and  white,  cause of,  589;
   white, independent of the bile, 603
 Chyme, 561
 Cicatrix in ovary after the escape of the ovum
   from the follicle, 849
 Ciliary, ganglion, 500;  motion,  73;  inde-
   pendent of nerves, 74 ; distribution in the
   animal kingdom, 75 ; when found in man,
   75;  its uses,  76;  cause,  77;  ligament,
   muscle, 412; nerves long, 423; result of
   irritating, 434 ; processes, 410 ; of vitreous
   body,416
 Ciliated epithelium,  523 ; in kidney of frog
   and newt, 791; of nose, 393
 Circular fibrous coat  of arteries, 651
 Circulation of blood, 649 ;  in embryo, 881;
   in arteries, 679  ; in brain, 263 ;  course of,
   676 ; in capillaries, 693 ;  continuous, 680 ;
   forces of,  694;  in fcetus,  677;  forces of,
   678; in frog's  foot, 695 ;  in lymphatics,
   618 ; rate of, 704 : in vascular area of e«-gs
   697; in veins, 700
 Circumvallate papillae, 381
 Cirrhopoda, sexual organs of, 826
 Claspers, in cartilaginous fishes. 827
 Cleavage of yolk after impregnation, 855
 Clemm, his analysis of milk, 902
 Climate and  seasons, influence of upon tem-
   perature, 736
 Clothing, influence of, upon temperature of
   the body, 738
 Coagulation  of blood, phenomena of,  630 ;
   of caseine,  etc., by gastric juice, 556
 Coathupe, Mr., on  volume of carbonic acid
   in expired air, 724
 Coats of a vein, 658
 Cochlea, 451; action of, 471 ; of birds, 444
 Cochlear ligament, 456
 Cochlearis muscle, 455
 Cold climates, food in, 516 ; effects of on taste,
   388
 Cold-blooded animals, 734
 Cole, on the velocity of the  circulation in
   arteries, 692
 Collard  de  Martigny, on  the  lymphatics
   during fasting, 521
 Colliculus, 885
 Colostrum, 902 ; corpuscles, 900
 Colon,  567; cells of, 573 ; muscular coat of,
  572
Colour of hair, destroyed by chlorine, 367
Colouring matter  formed by  red blood-cor-
  puscles, 641
Colourless corpuscles, office of, 641
Columella or modiolus of ear, 451
Columns of cord, functions of, 2K2
Columnae rugarum, of vagina, 845
 Columnar epithelium, 523 ; of bladder, 805 ;
   of ureter, 8(14 ; of villi, 576
 Coma, 323, 327
 Commissural fibres of retinae, 440
 Commissures,  cerebral, 258;  functions  of,
   329
 Common gall duct, 596
 Common sensation, 356;  sensibility, 352
 Comparative anatomy,  its value   to phre-
   nology, 49
 Compound  mucous  membrane,  546, 573;
   tissues, 62
 Compressible pulse, 6S2, 684
 Compressor urethrae, 834
 Concha, 445
 Cones, uriniferous tubes in, 793
 Congestion,  active and passive, 698
 Conical teeth,  526
 Conium,  effect of, on cord, 282
 Conjugation, 821
 Conjunctiva, 404;  imitation  of, from duct,
   698
 Consciousness, 45
 Consonants,  how produced in  vocalization,
   757
 Contact,  or catalysis, 741
 Contiguity, continuity, 345
 Contraction, active, 164,  170,  173  ; passive,
   164 ; duration and extent of, 175
 Contractility, 68, 163 ;  of  absorbent vessels,
   615 ; of arteries,  654, 682 ;  of skin, 355 ;
   varying character of,   evidenced by  its
   duration, 177 ; byits aptness to excitation,
   179
 Convoluted portion of uriniferous tubes, 789,
   791
 Convolutions of brain,  253;  functions  of,
   321
 Convulsions,  from lesion of corpora  quadri-
   gemina, 313
 Cooper,  Sir  Astley,  on circulation in  the
   brain, 265;  on the lacteal  glands, 898;
   absorbents of, 900 ; on the thymus, 817
 Co-ordination of movements, 301
 Copulatory organs of insects, 827
 Cord, invested with amnion, 892
 Cords, vocal, position of in vocalization, 752
 Cornea, 404
 Cornicula laryngis, 747
 Corona glandis, 833
 Coronary arteries, 664; vein, 664
 Corpora cavernosa penis,  832 ; lutea, 850,
   851; mamillaria, 259 ; quadrigemina, 312 ;
   fibres from, to chiasma, 422; and bige-
  mina, 878 ; striata, connections and func-
  tions, 308,  310
Corps reticule of Velpeau, 892
Corpus Arantii, 665, 668 ; callosum, functions
  of,  329; fornicis,  259;  Highmori, 830;
  spongiosum urethrae, 832 ; striatum, 250
Cortex of hair, formation of, 365
Cortical portion  of kidney, 789 ;  of supra-
  renal capsules, 814
Coste, M., on the decidua,  862
Costo-superior respiration, 718
Cotyledons of ruminants, 888
Course of the circulation, 676
Cow, corpus luteum of, 852 ; milk of,  902
Cowper, glands of, 832,  845 ;  on capillaries,
  662
Crampton, Sir  P. on the  ciliary muscle  of
  birds, 413 
)EX.
910
Cranium,  development of,  876 ; not a solid
  case, 267
Cranio-vertebral nerves, 272
Crassamentum, 628 ; contraction of, 631
Crawford, on influence of exhalation of car-
  bonic acid upon animal temperature, 725
Crayfish, follicles of liver of, 764
Creatine in urine, 799, 801
Creatinine in urine, 801
Crest of urethra,  or verumontanum, 834
Cricoid cartilage, 746
Crown of  tooth, 526
Crura cerebelli, 250
Crustacea, circulation in, 706 ; heart of, 662;
  organ of hearing, 442 ; sexual organs of,
  826 ;  spermatozoa of, 836
Crushing teeth, 526
Crystalline lens, 417
Crystals in blood  of spleen, 809
Cuneiform cartilages, 747
Cupola, 452
Cupped and buffed, 631, 632
Current, direct and inverse, 337
Cuticle, 359 ; depressions  in,  for ridges of
  cutis, 357;  under  surface of,  358; very
  thick on heels and palms of the hands,  360
Cutis, 354, 356; intimate structure of, 354
Cutting teeth, 526
Cuvier,  on  cerebral convolutions,  322;  on
  the shape of the jaw and character of  the
  teeth, 539
Cyclosis, 697
Cyclostomous  fishes,  generative  organs  of,
  827
Cystic duct, 596
Cystic entozoa, multiplication of, 823
Cysticercus fasciolaris, 823
Cysticule, 443
Cystine, 799, 802

Dalton, Dr.,  on  corpus luteum, 852
Dalrymple,  Mr.,  on  the capillaries of  the
  allantois,  896 ;  on vasa lutea, 893
Daphnia, hibernating, eggs of,  826
D'Arcy, on  the duration of impressions on
  the retina, 434
Dart sac in mollusca, 826
Dartos,  contractile fibres of, 156
Davy, on  the solubility of carbonic acid in
  defibrinated blood,  729
Death, 27, 36
Decapoda, sexual organs of, 826
Decussation of fibres in chiasma, 422
Decidua,  formation of, 859;   reflexa, 861;
  serotina, 861
Decomposition of gastric juice, 556
Defecation,  608
Deglutition,  541;  dependence on  medulla
  oblongata, 306
Demodex  folliculorum, 370
Dental groove, primitive, 532
Denticulate  lamina of cochlea,  453
Dentition, first and second, 536
Derma, 353
Descartes, Albinus, Hunter and Young, on
  the muscularity of the lens, 429
Desmoulins, on the distribution of the third
  nerve in falcons and eagles, 475
Detrusor urinae, 805
Development  of  blood  corpuscles,  642;  of
  animal, and tissues from cells,  63;   of
  the embryo, 863 ; of the eyelids, 880; of
  the heart and  aortic arches, 880 ;  of the
  lungs, 883 ;  of spermatozoa, 836 ; of Thy-
  mus,  816
Dextrine, 560, 588
Diabetes, presence  of hippuric acid in urino
  of, 801 ; food in,  520
Diaphragm, its condition  during vomiting,
  504, 566
Diarthrosis, 133
Diastole, 672
Diet, nature of, 516
Dietaries  in navy and in union workhouses,
  519
Diffusion of gases, 727
Digestive branch  of glosso-pharyngeal, 486
Digestion,  changes in  mucous  membrane
  during, 585 ;  effect of carbonic acid upon,
  724; general view of,  512; of fatty matter,
  594;  influence of alcohol upon, 562;  of
  exercise, 562 ; temperature, 556 ; in large
  intestine, 608 ; not stopped by section of
  vagi,  493 ; rate of, 561 ;  of stomach, 561 ;
  state  of villi  during, 578;  of vegetable
  substances, 560
Digestive principle, 556
Dilated capillaries of olfactory region, 395
Direct current in galvanizing nerves, 273
Discharge of ova. 848
Disease, influence of, upon animal tempera-
  ture,  739 ; effects of, on blood,  645
Distinction between plants and animals, 29,
  44
Diving-bell, effects  of, upon ear, 469
Dobson, on the use  of the spleen, 813
Dodart, on the number  of notes produced by
  the human voice, 755
Dormouse, intestinal canal of, 570
Dorsal,  laminae, 867 ; vessels of insects, 662
Double, chin,  354; vision in drunkenness,
  440
Doubleness of the organ of vision, 439
Dowler, Dr., on temperature in yellow fever,
  739
Draper, Professor, on circulation  of sap,  696
Druitt,  Dr., on  fatty  degeneration  of  the
  placenta, 891
Dry air, effect of, on the quantity  of urine,
  797
Duct, hepatic,  775; smallest branches  of,
  781;  of glands, 764; of the liver,  596
Ductus,  arteriosus, 678,  882;   communis
  choledochus,  596, 777; venosus, 677
Ductless glands, 806
Dugong, intestinal canal of, 571
Dulong and Despretz, on influence of nervous
  system on animal heat, 742 ; on relation of
  carbonic acid in respired air, 727
Dumas, on the acidity of gastric juice, 557
Dunglison, on gastric juice, 551
Duodenum, 568;   Brunner's glands,  579;
  mucous membrane of, 582 ;  valvulae con-
  niventes, 574
Dupuy,  on extirpation  of superior cervical
  ganglion of sympathetic, 510
Dupuytren and Orfila, on injecting fluids into
  the blood to relieve thirst, 522
Dura mater and its vessels, 227
Dysentery, 609

Ear,  ceruminous glands of, 371 ;  external,
  444, 463 ; in  man and ruminants, 464;
  internal, 449 
INDEX.
911
Ecker, on splenic blood, 607 ; on supra-renal
  capsules, 814 ; and Beclard, on disintegra-
  tion of blood-corpuscles of the spleen, 813
Echidna, 828
Echinodermata, reproduction of, 825
Edentata, intestinal canal of, 570
Edwards,  Dr., on  the temperature of the
  human body, 735
Efferent vessel of Malpighian body, 789
Ehrenritter, on the ganglion jugulare, 485
Ejaculatory canals, 830
Elaine, 59, 90
Elastic laminae, anterior and posterior,  406
Elasticity of arteries, 654 ; of arterial walls,
  679 ; of tissues, 66
Electrical fishes, 223; organs, 350 ;  current
  in muscles,  332
Elements  of organic  matter, essential and
  incidental, 29 ; mode of combination, 31';
  of respiration in food, 516
Emotions, 339 ;  centres of, 307,  314 ; effects
  of,  on speech, 755 ; mechanism of, 682
Embryo, blood-corpuscles in, 638;  cell, 856
Emetics, 564
Emulsion  of fat and pancreatic fluid, 594
Enamel, 530 ;  pulp,  533
Encephalic nerves, 271
Enderlin, on ashes of faeces, 610
Endochorion,  892
Endolymph, 453
Endosmose, into blood-corpuscles, 637 ; con-
  cerned  in the action of purgatives,  624;
  and exosmose, 67
Enemata, action of,  609
Entozoa, circulation  of, 706 ; from follicles of
  skin, 371 ; reproduction of, 825
Epencephalic vertebra, 876
Epidermis, 359 ;  action of acetic acid upon,
  361; shedding of, 361
Epididymis, development of, 887
Epiglottis, 747
Epilepsy, 281
Epiploon,  568
L'Epione,  on  the  action  of the stomach in
  vomiting, 565
Epithelium of  absorbent vessels,  614;  of
  aqueous humour,  407 ;  of artery, 653 ;  of
  bladder, 805 ; of cavities of the heart, 666 ;
  choroidal, 409 ; ciliated, of Fallopian  tube,
  842; conjunctival,  404;   of  convoluted
  portion  of uriniferous tubes, 792 ; of Cow-
  per's glands, 832 ; of ducts of glands, 765 ;
  imbricated,  of hair, 366; of Lieberkuhn's
  follicles, 573; of  lymphatic glands,  616 ;
  of minute hepatic ducts,  783 ; of mucous
  membrane,  523 ;  of nasal cavity,  393 ;  of
  oesophagus,  544;  of  pancreas,  767;  of
  papillae of tongue, 379 ; of prostate,  831 ;
  of scalae of cochlea, 457 ;  of seminal tu-
  bules, 835 ; changes in, during the develop-
  ment of the  spermatozoa, 835;  of  skin,
  353; of  stomach cells, 547;  of sweat-
  glands  369 ; of uterus, 844; of villi, 576 ;
  during fasting, 578; during intestinal di-
  gestion,  586             .
Erectile tissue, 578 ;  of penis, X6Z
Erection of nipple, 356, 900
Eremaeausis,  741
Erichsen, Mr., his experiments on absorption,
  611
Eructation, 563                 .
E.uption of permanent teeth, period of, 538
Eruptive stage of development of teeth, 536
Eschricht. on the relation of the fcetal capil-
  laries to the maternal vessels, 890
Ether, effect of inhalation of upon the quan-
  tity of carbonic acid expired, 725
Eustachian, tube,  448;  use  of,  469; valve,
  666, 677
Eyelids, development of, 880
Excito-motory actions of cord, 280
Excretion, 34, 758
Excretine, 759
Exercise,  favouring  or  retarding  digestion,
  562;  effects of,  on respiration,  725;  on
  temperature of the body, 735
Expiration, 720; muscles of, concerned in
  vomiting, 566
Extensibility of tissues, 66
External meatus, 444 ; tunic of arteries, 650
Extractive matter in urine, 801
Extremities, 141, 145
Extraordinary muscles of respiration, 720
Eye,  general  description of,  402;  of birds,
  cetacea, and fishes, 403 ; of invertebrata,
  402 ;  lids, 424

Faber and Silbermann, on animal heat, 742
Face, development of, 877
Facial nerve, 477 ; disease of, 479
Faeces,  analysis of,  609;  expulsion  of, 608 ;
  quantity of, 609
Fallopian tube, 842
False corpora lutea,  851
Falsetto notes, 754
Farre, Dr. Arthur, on bryozoa, 514; on organ
  of hearing in Crustacea, 443
Fascia,  subcutaneous, 354
Fascination of prey  by serpent, 342
Fasting, effects  of,  521; on  quantity of ex-
  pired carbonic acid, 725
Fat, 90 ; constituents of, 90 ; ultimate analy-
  sis  of, 91; distribution  of, in animals, 91 ;
  in man, 92, 93 ; morbid accumulation of,
  92 ; whence derived,  93 ; uses, 94 ;  in the
  liver, 605; in the  stools, 595 ; subcutane-
  ous, 356
Fatty degeneration,  of foetal tufts,  890 ;  of
  muscular fibre-cells of uterus, 843; de-
  generation of liver, analysis of, 768 ; cells
  in,  781 ; matter, absorption of, 591 ; action
  of  pancreatic fluid upon,  595 ; in chyle,
  621, substances, digestion of, 561
Fauces, mucous membrane  of, supplied by
  glosso-pharyngeal, 487 ; highly sensitive,
  307
Fecundity of osseous fishes, 827
Feeling in tongue, 387
Fellinic acid, 598
Female organs of generation, 839
Fenestra ovalis and  rotunda, 446
Fenestrated membrane of arteries, 654
Fernaby,  Mr., on the areas  of arteries, 692
Ferrein, on the production of vocal sounds,
  752 ;  on the pyramids of the kidney, 787
Festoons of heart, 668
Fever, faeces in, 610
Fibres of lens, 418
Fibrin, 54; in blood, 634;  in chyle, 587,
  588;  and lymph,  619; diminution  of, in
  fevers,  648 ; formed  by white blood-cor-
  puscles, 641; increase of, in blood, 647
Fibro-cartilage,  structure,  properties, and
  uses of, 100 
912
INDEX.
Fibrous tissue, white, 79 ; yellow,  82 ; coat
  of artery, 650 ; longitudinal of veins,  659 ;
  gray layer of retina, 413 ;  stroma of ovary,
  840 ; tissue in papillae of tongue, 384; zone
  of heart, 667
Fifth, nerve, lingual branch of, 388;  ventri-
  cle, 260
Figuier, on separating haematin from globu-
  lin, 644
Filamentous tissues, 62
First trace,  or nota primitiva, 865
Fishes,  blood-corpuscles of, 636 ; choroidal
  gland of, 409 ; cartilaginous, chorda dorsa-
  lis of,  868; circulation in, 695, 707; di-
  gestive  organs  of,  513;   heart  of,  663;
  intestinal canal of, 568 ;  organ of hearing
  of,  443 ; organ  of  smell  of, 400 ;  sympa-
  thetic nerve of, 498;  spermatozoa of, 836 ;
  teeth of, 526
Fisher,  Mr.,  on effects of cold  in Arctic
  voyage, 738
Fissiparous multiplication, 819
Fissure of Sylvius,  264
Flocculus,  connection of with portio dura,
  477
Flourens,  M., experiments  on the  encepha-
  lon, 304,  317; on the  destruction of the
  corpora quadrigemina, 312 ; on the removal
  of cerebellum in birds, 317 ; on removal of
  cerebral hemispheres, 305
Fluid in stomach during digestion, 551
Fluke, 823
Focus of a lens, 427
Fcetal, circulation,  677; tufts or villi, 862
Foetus, its position in utero  during the latter
  months of pregnancy, 898
Fohmann, on lymphatic glands,  616
Folds in large intestine, 575
Follicles of LieberkUhn,   573;  of  lacteal
  gland, 900 ; of mucous membrane  of ute-
  rus, 843
Food, changes of in small intestine,  587 ;
  Dr. Prout's classification of, 514;  effect of,
  on the temperature of the body, 735,  738 ;
  effects of  too  much or  too  little,  519 ;
  quantity necessary for health,  518; yolk,
  856
Foramen, caecum of tongue, 381;  commune
  anterius, 259 ; ovale or Botalli, 665 ;  fora-
  mina Thebesii, 666
Force, of the heart, 684; of the stream in
  arteries, 685
Forced expiration, 720
Forces, of the capillary circulation, 694; of
  the circulation, 678
Fordyce, on frequency of  heart's  action,
  675
Fornix, 258; function of, 329
Fossa, navicularis, 834 ; ovalis, 666
Fourth nerve, origin, 476
Fovea hemispherica, semi-elliptica,  450
Foville, on the functions of  the corpora stri-
  ata and optic thalamus, 311
Frequency of heart's action, 675
Frerichs, Dr., on carbonate  of ammonia in
  the blood in renal disease, 800 ;  on  con-
  stituents of semen, 838
Fraena of Ileo-caecal valve, 575
Frog, galvanoscopic, 331; kidney  of, 758;
  proper current of, 334
Fiik, Prof, on  temperature of internal parts
  of the body, 735
Functions, organic and animal, 45 ; of nerves,
   270 ;  of the liver, 605 ; of the kidney, 796;
   of plants and animals, general view of the,
   42, 46 ; of the red blood corpuscle, 640
Fundus of uterus, 842
Fungiform papillae, 382
Funke, on crystallization of blood, 729 ;  on
   crystals in splenic blood, 809
Fur on  tongue, 379
Furrows of skin, 354

Gall, arguments  against his theory of the
   function of the cerebellum, 320
Gall-bladder, 777;  use of,  596;  not uni-
   versally present, 597 ;  vessels of,  775
Galvani, his  experiments on the frog, 334
Ganglia, of nerves, structure of, 207; cepha-
   lic, of sympathetic,  500 ; of sympathetic,
   498;  of  hearing, smell, taste, touch, and
   vision, 314
Ganglion, cardiacum Wrisbergii, 672; impar,
   498 ;  jugulare petrosum, 485 ; ophthalmic,
   500 ;  otic,  501; semilunar, 503 ;  spheno-
   palatine, 500 ; submaxillary, 501; superior
   cervical, connections of, 502
Ganglionic system of nerves, 192
Garrod,  Dr., on the detection  of  urea  in
   blood, 800
Gases, in intestinal canal, 610
Gasserian ganglion, 481
Gastric  juice, 554; antiseptic power of, 556 ;
   action of various acids in, 554; artificial,
   554 ;  importance of acid in, 555; organic
   principle of, 556 ;  its action on albumen,
   555, 560 ;  on  meat, milk, and vegetables,
   560
Gasteropoda, heart of, 663;  organ  of hear-
   ing of, 442; stomach teeth of, 525
Geiger,  on the quantity of lymph, 622
Gelatine, 57;  producing colourless  chyle,
   621;  from  cutis, 355
Gelatinous nerve fibres in sympathetic, 196
Generation, 819 ; female organs of, 839 ; true,
   821
Generative organs ; development of, 887; of
   fishes, 827 ; of vertebrata,  827
Geniculate bodies, connection of optic tracts
   with,  421
Genito-urinary mucous membrane,  523
Gerber, on the termination of nerves in skin,
   360
Gerlach, on  blood corpuscle-holding cells,
   809 ;  on ciliated epithelium of the kidney
   of the fowl, 791; on the Malpighian tufts,
   791
Germ, cell, 821; yolk, 856
Germinal, centres of glands, 763; spot, 841  ;
   vesicle, 841; formation of, 857 ; disappear-
   ance of after impregnation, 855;  of Ento-
   choncha, persistence  of, 855;  spot, or nu-
  tritive centre, 889
Giddiness, 326
Gizzard in birds, 569
Gland cell, 764
Glands,   aggregate, 583;  of Brunner,  579;
   of Havers, 762; of intestine, 579;  ofLittre,
  834; of Peyer, 581  ; sebaceous, 370; sweat,
   368;  solitary, 580;  tracheal,  708; true,
  762
Glandulae  Nabothi,  844;  odoriferae,  370;
  Tysonianae, 834
Glandular epithelium, 523 
INDEX.
913
Glans penis, 832
Glasserian fissure, 447
Globe of the eye, 402
Globuline, 59
Globus hystericus, 307
Glottis, alteration of aperture of, 750 ; closure
  of, 494 ; its condition in vomiting, 564
Glycerine, 91
Gmelin  and Berzelius, on the character of
  choroidal pigment, 409
Goat's milk, 902
Goodsir, on  the cavities of reserve, 536;  on
  centres of nutrition, 523;  on cirrhopoda,
  826 ;  on the development of teeth, 532 ;
  on  lymphatic glands, 615;  on matrix of
  'kidney, 788 ; on membrana decidua, 861;
  on the development of the thymus, thyroid,
  and supra-renal capsules, 883
 Gorup-Besanez, on the reaction  of the bile,
  598
 Gosse, on the rate of stomach digestion, 562
 Gottsche, on the optic lobes of pleuronecta,
   312
 Gout, 699
 Graafian vesicles,  839
 Graham, Prof., on analysis of blood-corpus-
   cles of invertebrata, 640 ; his law of diffu-
   sion of gases, 727
 Grainger, Mr., on  effects of the removal of
   cerebral hemispheres,  306;  on  medulla
   oblongata, 306 ;  on roots of nerves, 271;
   on the spinal cord, 287 ; on the umbilical
   vesicle, 893
 Grandchamps, on the functions  of the  cor-
   pora striata and optic thalami, 311
 Granular, lids, 426;  layer of dentine, 414;
   cells, 638; corpuscles in menstrual fluid,
   848
 Gravity,  influence of upon  venous circula-
   tion, 703
 Gray, Mr. H., on Malpighian corpuscles of
   the spleen, 812 ; on the use of the spleen,
   813 ; on the development of the liver and
   spleen, 885 ; of the supra-renal capsules,
   887;  thyroid,  883;  organs of vision and
   hearing, 879
 Gray matter of convolutions,  256 ; of cord,
   predominance of, in lumbar region, 286
 Grew's glands, or Peyer's glands, 581
 Grinding teeth, 526
 Groove on the heart,  664
 Guanin in the renal organs  of arachnida,

 Gulliver, Mr., on molecular  base, 587 ; of
   chyle, 619
 Gums, 532
 Guy, Dr., on the pulse, 675 ; on the frequency
   of the respiration, 722
 Guyat, on taste, 386

 Habit, influence of, in the economy, 37
 Haemadromometer, 690
 Haemadynamometer,  686
 Haemal arch of vertebrae, 865
 Haematine, 59, 644;  a secretion of the blood
   corpuscles, 641        .          fiQ1
 Hemorrhage from the uterine vessels 891
 n„;„  fniii^ip 364 ;  colour of, 367 ;  growing
 H7hite! S; method  of making  sections

 Hall Dr Marshall,  on the nervous system,
    280, 288  290 ;  on muscular  contractility,
  177, 303;  on excito-motory actions, 280;
  on the vagus, 494
Haller, on the great cardiac plexus, 505 ;  on
  the formation of corpora lutea, 850 ; on the
  musular fibres of the meatus, 445 ; on the
  quantity of bile, 597 ; on the quantity of
  blood, 630;  on the folds of the  umbilical
  vesicle, 893
Hales, on capillaries,  662 ; on the capillary
  circulation, 680 ; on the force of the heart,
  678 ;  on the pressure of the blood in arte-
  ries, 684; on  the velocity of the blood in
  arteries, 684; and Poiseuille, on the force
  of the current in the veins,  701
Hamberger, on the movements of intercostal
  muscles, 719
Hamulus, 452
Hancock, on  muscular fibres, of  prostate,
  831; of urethra, 833
Hand, 145
Hare-lip, 877
Harless, on  the  presence of uric acid in  the
  renal  organs of the cephalopoda, 786 ; on
  the diameter of  the  blood-corpuscles in
  arterial and venous blood,  729
Harvey, on the discovery of the circulation,
   649 ;  on the quantity of blood,  630
Hassenfratz, on carbonic acid in  the blood,
  730
Hastings, Sir Charles, on the irritability of
  arteries, 682
Havers, glands of, 762
Haversian canals of bone, 110
 Headache,  325
 Hearing, difference of in different persons,
   472 ;  organ of, general description, 442 ;
   development of, in  animal  series, 442 ;
   phenomena of, 463 ; development of organs
   of, 880
 Heart, 662 ; arrangement of fibres in, 158  ;
   contractions  of,  182 ;  of  Crustacea, 663 ;
   development of, 870, 880 ; of birds, 663 ; of
   fishes, 663 ; force of, 684 ; ofmollusca, 663 ;
   muscular tissue  of, 669;  nerves of, 671;
   nutrition of, 671; of reptiles,  663; influ-
   enced by spinal cord, 302 ;  sounds of, 673
 Heart's action, 672 ;  frequency of, 675 ; in-
   fluence of the period of the day, posture of
   the body, etc., upon,  675.
 Heat,  amount  of, developed, in  organism,
   734;  animal, influenced by exercise,  735;
   development of, in animals, 734; in plants,
   733; developed  when carbon combines
   with oxygen, 733 ;  loss of,  by evaporation,
   737; period of, in animals, 849 ; and cold,
   sensations  of, 376
 Heberden, on frequency of the heart's action,
   675
 Hectocotylus, 826
 Heintz, on urate of soda in urine, 800
 Helicotrema, 452
 Helix, 444 ; groove, 445
 Hemiplegia, paralysis of tongue in, 48U;^ac-
   companying lesion of corpora striata,  «$uy
 Hemispheres, cerebral, 253
 Henle, on epithelium of arteries, bbd  ; on
   change of form in the red blood corpuscles,
   729 ; on  lacteal ducts,  900 ; on  movements
   of spermatozoa, 837; and Kolliker on Paci-
   nian corpuscles, 349
  Hepatic duct, 596 ; vein, 777
  Herbivora, Brunner's glands m, 579 ; Peyer » 
911
INDEX.
  patches in, 582;  sources of carbonic acid
  in, 731
Herbst, on the capacity of the lungs, 723
Hermaphrodite, 825
Herschel, on achromatism of the eye, 432;
  on intensity of sound, 463
Hewson, on coagulation of the blood, 631
Hiatus Fallopii, Vidian nerve in, 477
Hibernation, 739 ; absorption of fat during,
  612 ; in animals,  thymus during, 818
Hippocampus major, 262
Hippuric acid, 801; in  urine, 799
Hirudines, reproduction of, 825
Hissing of serpents, 745
Holding the breath, effects of, 721
Home, Sir E., on membrana  tympani, 446
Hoofs, 363
Hoop, production of in  hooping-cough,  755
Hooping-cough, nature  of, 493
Hope, Dr., on cause of second sound of heart,
  674
Horn, on taste, 390
Horse, kidney of, 793
Houston,  Mr., on the folds  of the rectum,
  575
Houston. Dr., on the circulation in an anen-
  cephalic foetus, 697
Hubert, on the temperature of plants, 733
Human, embryo, development of, 871; heart,
  663  •
Humboldt, Baron Von,  his case of suckling
  by the male parent, 901
Hunefeld's experiments on the action of the
  bile,  603
Hunger, 521
Hunter, John, on the contractility of arteries,
  655, 682 ; on the changes in the jaw bone,
  538 ;  on the gastric  juices, 553 ; on  the
  tonicity of  arteries,  683; on  vomiting,
  565
"Hunter, Dr. W., on the decidua, 861
Huschke, on the  development of the  eye,
  879
Hutchinson Dr., on the movements of respi-
  ration, 717; on the force of the respiratory
  muscles, 721; on the spirometer, 723
iHuxley,  Professor, on reproduction in acale-
  phae, 825 ;  on the spleen, 812
Hyaline, 61
Hyaloid membrane of vitreous body, 416
Hybrids, spermatozoa of, 839
Hydrocele, 829
Hydrochloric acid in gastric juice, 554
Hydrocyanic acid, its absorption, 619
Hydrophobia, part of nervous centres affected
  in, 307
Hymen,  845
Hypoglossal nerve, 480
Hypophysis of pituitary body, 261
Hypospadias, 888
Hypotheses, to explain  action of cord,  655
Hyrtl, on the escape of the  ovum from the
  Graafian follicle,  848
Hysteria, 307;  associated  with excited states
  of emotion, 316 ;  and chorea, effects of on
  voice, 755

Ice, its effects upon the cord, 282
Ileo-caecal valve, 575
Ileum, mucous membrane of, 583
Ilg, on the wall of  the cochlea, 452
Image, formation of on the retina, 432
Imbibition, 622
Impregnation of the ovum, 853
Impressions, duration of on the retina, 434
Impulse of the heart, 673
Incisors, 526
Incisurae Santorini, 445
Incus, 448
Inferior cava, 665
Infundibulum, 452, 664; of lungs, 712
Infusoria, multiplication of, 825
Ingesta and egesta, 761
Injecting ducts of liver, 780 ; tubes of kidnev,
  789
Inorganic bodies, their modes of combination,
  28
Insalivation, 539
Insects, circulation of, 707 ; dorsal vessel of,
  662 ; generative organs of, 826 ;  gizzard of,
  525;  hum  of, 745; liver of, 770;  renal
  organs of, 786 ; temperature of, 734
Insectivora, intestinal canal of, 570
Inspiration, full, 723
Instinct, 46, 186
Intellectual action, centre of, 323
Intercostal muscles, movements of, 718
Interlobular fissures, 782
Intermaxillary bones, 877
Intermittent fever, blood in, 648
Intervertebral discs, 101
Intestines, large, mucous membrane of, 570,
  583 ;  villi of, 576 ;  development of  walls
  of, 883 ; digestion in, 608 ; movements of,
  583; muscular coat of, 572; Peyer's glands,
  581 ; solitary glands, 580
Intestinal canai, anatomy of, 567 ; in verte-
  brata generally, 571;  of birds, carnivora,
  and insectivora, 569 ;  of cheiroptera, eden-
  tata, pachydermata, ruminantia, rodentia,
  and solipeda, 570; of cetacea, marsupialia
  and  quadrumana,  571;  of fishes,  568 ;
  changes of mucous membrane  of, during
  digestion, 579
Intestinum, crassum,  567;  tenue, 567
Intromittent organ, 829
Intumescentia genuformis, 477
Inverse current, in galvanizing nerves,  273
Inversion, in action of the stomach, 563 ;  of
  image in vision, 428
Invertebrata, blood-corpuscles of, 636 ;  liver
  of, 770 ; teeth of, 525
Inverted  image,  correct  vision  with an,
  437
Investing membrane of Reichert,  864, 867
Involucra, cephalic and caudal, 845
Involuntary movements, 276
Ipecacuanha, production of asthma by, 493
Iris, 410 ; alteration of during the adaptation
  of the  eye to  distances, 430 ; influence of
  corpora quadrigemina upon, 313; office of,
  431;  paralysis of, after section of the third
  nerve, 475 ; its use in protecting the retina
  from too much light, 433
Iron  in  blood-corpuscles, 640 ; state  of, ac-
  cording to Liebig, 645
Iter a tertio ad quartum ventriculum, 261

Jacob, Dr., on the lines of the iris, 411
Jacob's  membrane,  415:  development of,
  879
Jacobson, anastomosis  of, 447;  nerve of,
  485 ;  on allantoic fluid of birds, 897
Jaw-bones at different ages, 538 
INDEX.
915
Jejunum, 568 ; mucous membrane of,  582 ;
  valvulae conniventes, 574
Johnson, Dr. G., on matrix of kidney, 788; on
  vessels of kidney in chronic nephritis, 699
Joints,  126,  130 ;  influence  of  atmospheric
  pressure upon, 131; forms  and classifica-
  tion of, 131
Jones, Dr. Bence,  on the increase of alkaline
  phosphates in the urine, in cases of inflam-
  mation of the brain, 803 ;  on the reaction
  of urine, 798; on the  increase of the sul-
  phates in the urine in chorea, 802
Jones, Dr. Handfield, on the arrangement of
  the liver-cells, 780 ; on the development of
  the liver, 885 ; on the relation of the  liver-
  cells to the  duets, 782 ; on the intestinal
  mucous membrane, 582 ; on prostatic con-
  cretions, 832; on the thymus, 818
 Jones, Mr. Wharton, on  the development of
  the human ovum, S71; on the lymph corpus-
  cle, 620 ; on the  membrane of the black pig-
  ment, 409 ; on the rhythmical contractions
  in the veins of the bat's wing, 703; on the
   red blood-corpuscles, 637;  on buffing and
   cupping, 632 ; on the white blood-corpus-
   cle, 637
 Jugular vein,  881
 Jurin. Ramsden, and Home, on the  change
   of the cornea in vision, 429
Kempelin, Dr., on the action of the glottis,
  751
Kerner, on the effects of the loss of the au-
  ricle, 465; on the  use of the semicircular
  canals, 472
Kidneys,  785;  analysis  of, 786 ;   general
  remarks on  the function  of, 803 ; vessels
  of, 793 ; development of, 886
Kiernan, Mr., on  the hepatic vein, 778; on
  portal canals, 769
King's College Hospital, quantity of  air
  allowed to each patient, 728
Knox,  Dr., on the alteration of the curvature
  of the  lens,  429 ; on the frequency of the
  heart's action, 675 ; on the yellow spot on
  the retina, 415
Kolliker, on the  anastomosis and branching
  of the fibres of the  heart, 670; on the
  blood-corpuscles of the spleen, 808 ; on the
  cells of the liver, 779 ; on the cleavage of
  the yolk in the ova of the intestinal worms,
  856 ; on the colouring matter of the bile,
  6H7 ;  on the epithelium  of the  bladder,
  805; on the helicine arteries of the  penis,
  833 ;  on the Malpighian corpuscles  of the
  spleen, 812 ; on the  origin of lymphatics,
  617 ; on lacteal ducts, 900 ; on the prostate
  gland, 831 ;  on the relation of  the hepatic
  ducts to the liver cells, 782 ;  on the red
  blood-corpuscles,  637 ; on the  spermato-
  zoon, 836 ; and Bagge, on the development
  of intestinal worms, 841
Krause,  on the  bulk  of the liver, 767;  on
  the weight of the  lungs, 707
Krieger on otoliths,  459              _
Kronenberg, on  sensitive  filaments  in the
  anterior roots of the  nerves, 275
Kuchenmeister,  and Van Beneden  on the
  development of the  cystic entozoa, 823

Labyrinth, 449 ; experiments to show the
  use  of, 470 ;  of birds, 444
Lachrymal sac, 426 ;  gland, 426
Lactation, 898
Lacteal, glands, 898 ;  of male, 900;  tubes,
  899
Lacteals, distribution of, in intestine, 612;
  filled  with chyle,  586 ;  of villi, 577 ;  do
  they absorb fat only? 591; and lymphatics,
  612
Lactic acid in caecum, 608 ; in gastric juice,
  558 ; formed from digestion of starch, 560 ;
  in urine, 799
Lacuna magna, 834
Lafargue, on the effects of removing the cor-
  pora striata, 309
Lagrange and Hassenfratz, on carbonic acid
  in the blood, 730
Lamina spiralis, 452
Laminae dorsales,  867
Lamprey,  mouth  of, 524;  organ of  hearing
  of, 443 ; and myxine, blood-corpuscles of,
  636
Lane, Mr., on valves of absorbents,  614
Langenbeck, on the development of the uri-
  nary bladder, 896
Langer and Kolliker,  on the development of
  the lacteal glands, 901
Lanugo, 874
Large intestine, 567
Laryngismus stridulus, how produced, 493
Larynx, the organ of  voice, 744 ;  action of,
   750
Lassaigne, on the gastric juice, 559
Lateral pressure in arteries, 684
Lauth, on lymphatic glands, 616 ; and Muller,
   on the ligaments of the larynx, 748
Lee, Dr. R., on the nerves of the heart, 672 ;
   on the  nerves of the uterus, 844 ;  on the
   rupture of the  Graafian  follicle,  848 ;  on
   yellow matter of corpus luteum, 850
 Le Gallois, experiments  on the medulla ob-
   longata, 306
 Lehmann, on the acid of the gastric juice,
   558 ; on crystallization of blood, 729 ;  on
   increase of urea in urine from a nitrogen-
   ized  diet,  800  ; on hippuric acid  in the
   urine of diabetes, 801
 Leidy, on the arrangement of the liver-cells,
   780
 Letheby, Dr., his case of ovum, detected in
   the Fallopian tube, 848 ; on  the  composi-
   tion  of the menstrual fluid, 848
 Lens, 418 ; analysis of, 420
 Lenticular, process  of incus, 448; ganglion,
   423, 500
 Leuchs, his experiments on saliva, 541
 Leucocythemia, 648
 Leuret on the weight of the cerebellum, 320 ;
   on the cerebral convolutions, 254
 Lassaigne on the gastric juice, 559
 Leeuwenhoek, on capillary vessels.
   the fibres of  the crystalline lens,
   teeth,  527
 Ley, Dr., on laryngismus stridulus, 4.).
 Leydig,  on  ciliary motion
   glands  of the sow, 861
 L'Heritier, on the effect of temperament upon
   the character of the milk, 902
 Lieberkiihn, follicles  or glands of, 57d, <t>i>
 Liebig, Professor, on absorption by animal
   membrane, 623;  on the acid of the gastric
   mice,  559 ; on elements of nutrition, 516;
   on the  uses of  the bile, 602; on the quan-
662;
419 ;
the uterine 
916
INDEX.
   tity of carbonic acid removed from the
   body,  730 ;  on the  state of the iron in the
   blood, 645; on the reaction  of the urine,
   798 ;  on the red blood-corpuscle, 640
 Life,  27, 35 ;  dormant, 28 ; theories of, 36, 41
 Ligaments, their varieties, 80 ; ciliary,  412 ;
   of  bladder, true and false,  804;  thyro-
   arytenoid,  747; thyro-hyoid, 748; of the
   uterus, 845
 Light, composition of, 427
 Lime salts, in gastric juice, 558; in urine,
   799
 Limnaeus stagnalis, fluke in the  liver  of,  823 ;
 Lips,  524; cuticle of, 356 ; as organs of pre-
   hension, 523 ;  of ruminants and rhinoceros,
   sense  of touch in, 373
 Liquor,  chyli, 587;  amnii,  892; sanguinis,
   629 ; still layer of liquor sanguinis, 693
 Lithate of soda,  in urine, 799
 Lithic or uric acid, 800 ; in urine, 799
 Littre, glands  of, 834
 Liver, 767 ; analysis of,  768; cells, 779, 780 ;
   development of, 884 ;  of chick during in-
   cubation, 606 ; fat in,  604;  of frog,  change
   of colour in, 607;  function of the, 596 ;
   subservient to respiration,  602; sugar in,
   604 ; supply of blood, 596 ; as a  source of
   the  blood-corpuscles, 607
 Lobe of ear, 445
 Lobular passages in lungs, 711; diameter of,
   712
 Lobules,  of liver,  771;  of  lung,  709;  on
   surface of the kidney, 787
 Locomotion, 78,  301;  passive and  active
   organs of, 78
 Locus niger, connection with third pair, 474;
   motor influence of, 309
 Locus  perforatus, chiasma  of optic  nerves
   connected with, 421
 Longet, M., experiments on anterior columns
   of the cord, 284; on  optic thalami, 311;
   on encephalon, 309,  310 ; on motor nerves,
   273
 Lower on the fibres of the heart, 670
 Ludwig and Volkmann, on the circulation
   in arteries, 689
 Luminosity of animals, 224
 Lungs, 707;  resilience of,  720;  develop-
   ment of, 883
 Lunula of nail, 363
 Lymph, 612 ;  composition of, 622 ;  corpus-
   cles, 619, 620  ; Mr. Wharton Jones  on,
   620 ; and blood, distinction between, 622
Lymphatics, function of, 627 ; of gall-bladder,
   777 ; of liver, 779;  of lower  extremities,
   613; in  the  tail of larvae  of batrachia,
   617 ; origin  of, 616 ; of spleen, 812 ; and
   capillaries of skin, 372
Lymphatic  glands, number of,  613 ;  struc-
   ture of, 615
Lymphatic system,  as  one origin of  blood-
   corpuscles, 642
Lymphatic hearts, 618
Lymphatic network of  skin,  367
Lyra, 259

Maoder colours bone,  123
Magnesia, salts of, in urine, 799
Magnus,   on the  quantity of oxygen and
  carbonic acid in blood, 728 ; on solubility
   of carbonic acid in serum, 729
Maissiat, on ordinary respiration, 718
  Majendie on  absorption, 626 ; on  the  cere-
    bellum, 318 ;  on the superior and inferior
    laryngeal nerves, 490;  on cerebro-spinal
    fluid, 268 ; on circulation in the veins, 695 ;
    on cerebellum, 318; on the effects of  feed-
    ing dogs on sugar, 518 ; on taste,  385, 390 ;
    on vomiting, 565;  and Mayo on falsetto
    notes, 754
  Male, organs  of generation of, 829 ; lacteal
    glands of, 900
  Malleus, 448
  Malpighi, on capillary vessels, 662
  Malpighian bodies of kidney, 789 ; corpus-
    cles of spleen, 811, 886
  Mammalia, air-cells of, 716 ; blood-corpuscles
    of,  635 ;  circulation  of,  707;  intestinal
    canal of, 569 ; generative organs of,  828 ;
    organ of hearing of, 444; ovum of, changes
    in, 866
  Man, an omnivorous animal, 514
  Mandl, on the vitality of hair, 366
  Manis, teeth of,  526
  Manubrium of malleus, 448
  Marcet, Dr., on the composition of faeces, 759
  Margarin, 59,  90
  Marianini,  Dr., contractions produced  in
   frog by galvanism, 337
 Mariotte, on the absence of  visual sensation
   over the point of entrance of the  optic
   nerve, 435
 Marmot during hibernation, 740
 Marshall, Mr.  J., on the development of the
   anterior venous trunks, 882
 Marsupialia, 828;  intestinal canal  of, 570 ;
   connection between foetus and mother, 888
 Mascagni, on  the  follicles  of the lacteal
   glands, 899
 Mastication, 541;  motor  nerve   of,  484;
   movements of, 538
 Mastoid cells, 448
 Maternal cotyledons, £88
 Matrix of enamel, 534;  of nail, 363 ; of kid-
   ney, 788
 Matteucci, electro-physiological experiments,
   273, 331; on the gills of the ray, 707 ;  and
   Cima, on absorption through membranes,
   624 ; researches in animal  electricity, 223,
   327, 331, et seq.
 Mayo, on falsetto notes, 754 ; on fifth nerve,
   483 ; and Valentin on third  nerve, 475
 Meat, digestion of, 555,  560
 Meatus auditorius, 445;  urinarius,  846  ; of
   the nose, 391
 Mechanism, of valves, 669;  of the skeleton,
   136
 Meckel's ganglion, nasal branches of, 399
 Mediastinum testis, 830
 Medulla of hair,  365
 Medulla oblongata,  descriptive anatomy of,
   239 ;  course  of fibres in,  244 ; disease of
   one-half of,  304;  function  of, 304;  in-
   fluence of in  vomiting, 566 ;  irritation of,
   304;  office of nerves arising from, 304
 Medullary portion of kidney, '
   renal capsules,  814
 Medusa  buds,  formation  of,
   S22
 Medusae, circulation  in, 706 ;  digestive  or-
  gans of, 514
Meibomian glands, 425
Meissner on the impregnation  of the ovum.
  853
   ; ofsupra-

from  polyps, 
INDEX.
917
Me
elsens and Dumas, on the acidity of gastric i   of respiration,  716 : quantitv of carbonic
juice, 557                                |   aeid exhaled in, 726 ; of stomach, 550
Membrana decidua,  860;  granulosa,  840;
  intermedia of Reichert,  864,  867; pupil-
  laris and capsulo-pupillaris, 879 ;  tympani,
  446 ; action of, 464; secundaria,  451
Membrane, simple  and  compound, 61;  of
  the aqueous humour, 420
Membranous,  labyrinth,  449, 45S  ; portion
  of urethra, 834;  zone  of cochlea, 454
Memory, 325
Men, analysis of the blood of, 644
Menstrual fluid, 847
Mercury, bichloride, its action on albumen,
  53; on gastric juice, 557
Mesencephalic vertebrae, S76
Mesentery, 568
Mesenteric glands,  612
Mesmerism, 328
Mesocephale, descriptive  anatomy  of,  248  ;
  functions of, 303  ; centre of emotion, 307
Mesocaecum,  56S
Mesocolon, 568
Metamorphosis, 821
Metagenesis,  822 ;  in insects, 823
Meyer on the contraction of the gall-bladder,
  765
Micropyle, 853
Microscope, as an aid to research in anatomy,
  50
Middle coat of arteries, 650
Milk, 901 ;  cow's,  902 ;  goat's,  902 ;  acted
  on  by gastric juice, 560 ;  alimentary ma-
  terials in, 515
Milk teeth, 537
Miller, Dr., his analysis of urine, 799
Mind, 45, 238 ; its  influence on the organic
  processes, 317; associated with the cerebral
  convolutions, 322 ;  its influence  in sensa-
  tion, 351
Mitral orifice and valve, 664
Mitscherlich, on the quantity of saliva,  540
Model prison, quantity of air passing through
  each cell of, 728
Modiolus, or columella, 451
Molar teeth, 527
Molecular, base in  chyle, 587, 619 ; motion,
  organic, 71
Moleschott, on exhalation of aqueous vapour,
  724
Mollusca, circulating organs of,  707; diges-
  tive organs of, 514; heart of, 663 ;  liver
  of, 770 ; organ of hearing, 442 ; reproduc-
  tion of, 825
Monotreinata, 828; intestinal canal of, 570;
  nutrition of embryo in, 888
Montgomery,  Dr.,  on corpus luteum, 850
Morganti and Bernard, on the spinal acces-
  sory, 496
Mother cell, containing spermatozoa, 836
Motion, centres of,  308
------visual perception of, 422
Motores oculi, 473
Movements, association of, 182 ; symmetrical
  and harmonious  movements, 183; co-ordi-
  nate movements, 183, 319; mode of excita-
  tion, as by volition and emotion, 185, 293,
  307 •' bv reflected stimulus, 186,  307 ;  in-
  stinctive movements, 186 ; mechanical or
  habitual movements, 186 ; in  the interior
  of  the body, 70;  of  the intestine,  583 ;
         59
Mucous membrane, descriptive anatomy of,
  522 ; of bladder, 805 ;  of caecum, 583 ;  of
  duodenum,  582 ; of large intestine, 583 :
  of intestinal canal,  573 ;  of nasal cavity,
  392 ; of  stomach,  551 ;  changes in, 540 ;
  changes in during intestinal digestion, 585 :
  of urethra, 834;  of uterus, 844; at men-
  strual periods, 847
Mucous or vegetative layer of germinal mem-
  brane,  859
Mucus, of bile, 599; of stomach,  551, 559 ;
  of stomach cells, 517
Mulberry mass, 857
Mulder, his analysis of hoematine, 615 ; on
  the red blood-corpuscles, 635
Muller, on the actions of the oesophagus, 545 ;
  on the arteries of the penis, 833 ; on hectoco-
  tylus, 82(1; on the impregnation of the ovum,
  854 ; on the development of the liver, 885 ;
  on the  office of the labyrinth, 470 ;  on the
  Malpighian corpuscles  of the spleen, 811 ;
  on  the roots of the nerves, 274;   on the
  oscillations of the membrana tympani, 468 ,-
  on vocal  sounds, 751 ;  on the suction power
  of the auricle,  702 ; on Wolffian  bodies,
  886 ; and Dickhoff on section of the vagi,
  493; Gurlt and Kornfeld, on  section  of
  the lingual nerve, 387; and Lehfeldt  on
  falsetto notes,  754;  and  Dr. J. Reid  on
  functions of the spinal accessory, 496 : and
  Volkmann on  correct vision with  an in-
  verted  image, 438
Multiplication, 819
Muscles, how formed, 157; shapes and ar-
  rangement of fibres, 157-8 ; origin and in-
  sertion, 158; bloodvessels of, 159 ;  nerves
  of,  160 ;  antagonist  muscles,   162 ;  ar-
  rangement of muscles on the skeleton, 162 :
  arytenoid, 750; buccinator  supplied   by
  fifth nerve, 479 ; cervicalis ascendens, 423 ;
  ciliary, 412; cochlearis, 455; compressor
  naris, 392; compressor urethrae, 834 ; cor-
  rugator  supercilii, nerve to, 478; crico-
  arytenoidei postici  and laterales,  and
  crico-thyroidei, 749;  depressor  alae nasi,
  392 ; detrusor urinae,  805, 834 ; digastric,
  539 ; external pterygoid, 539 ; internal of
  malleus,  449 ;   internal  pterygoid, 539 ;
  of internal ear, 468 ;  intrinsic and  extrin-
  sic of larynx, 749 ; laxator tympani, 449 ;
  laryngeal, action  of,  749 ;  levator  ani,
  levatores costarum, 720; levator palpebrae,
  obliqui and recti oculi, 424; omo-hyoid,
  sterno-hyoid,   stylo-hyoid,  and  stylo-
  pharyngeal,  749;  orbicularis  palpebra-
  rum, 425 ; pectoral, 720 ; serratus magn us,
  serrati postiei, sterno-mastoidei, and tra-
  pezii,  720 ;  nerves   of,  495 ;   sphincter
  vesicae, 805 ;  superior,  anterior, and pos-
  terior auris, 445 ; respiratory, 7.10 ; power
  of, 720;  action of,  718; stapedius,  447,
  449 ;   thyro-arytenoidei,  437 ;  temporal,
  masseteric, 539; trarhoalis, 708, 721; un-
  striped of absorbents, 614
Muscular coat of arteries, 052 ; of small in-
  testine,  572;  of colon, 572
Muscular fatigue, 164
Muscular,  movement, varieties of, 179; ac- 
918
INDEX.
  tion of sphincters,  180 ;  peristaltic, 180 ;  J
  and rhythmical contractions, 182
Muscular pile, 332
Muscular sense,  373
Muscular sound, 173
Muscular tissue  of two kinds,  146 ;  Striped
  Fibres, 146 ; their internal structure, 147 ;
  sarcous elements, 147 ; sarcolemma, 150 ;
  union of tendon to  muscle, 151  ; develop-
  ment,  152; corpuscles or cell-nuclei, 153;
  growth,  153.   Unstriped  Fibres,  153;
  distribution of the two varieties  of fibre in
  the body, 155; and in the  animal series,
  156; contractility, 68, 163, 176;  stimuli,
  165
Muscular tissue;   minute changes during
  contraction, 167; during passive contrac-
  tion, 170 ; during active contraction, 170 ;
  exhibited in fatal tetanus, 173  ; develop-
  ment of heat  during  contraction, 174;
  duration and  extent of contraction, 175 ;
  zigzags explained, 176 ;  force at different
  degrees of contraction, 176
Muscular contraction;  influence of nervous
  system upon,  303;  development  of elec-
  tricity in, 337 ;  electrical current, 332
Muscular fibres, of arteries, 652, 682 ;  of
  heart,  669 ; of oesophagus, 544 ; of stomach,
  546 ; of uterus, 843
Muscular zone of spiral lamina of cochlea,
  456
Muscularity of ducts of glands, 765
Musculi, papillares, 665; pectinati, 665
Musical sound, 462
Myopia,  430
Myriapoda, circulation in, 707
Myxine, chorda dorsalis of, 868

Naegei.e, on the duration of pregnancy, 849
Nails, 363
Na'is, reproduction of, 820
Naked capillaries of lung,  713 ; of Malpig-
  hian tuft, 791
Nasal, cavity,  development  of, 877 ; duct,
  427 ; fossae, 391
Nasse, Dr., his case  of paralysis, 284;  on
  chyle, 622; on  the cause of buffing and
  cupping, 632
Nasmyth, on the cementum, 536
Nausea,  nature  of, 494
Neck of tooth, 526
Negro, cuticle of,  363 ; hair  of, 367
Nerves,  definition, 191; tubular fibres, 193 ;
  gelatinous  fibres,   196.     Cerebro-spinal
  nerves, 200 ;  neurilemma, 200 ; bloodves-
  sels, 200 ; origin,  200 ; branching, 201 ;
  anastomosis, 201; plexuses, 203 ; termina-
  tion, 204.   Ganglionic iierves, their struc-
  ture, arrangement,  and connections, 205 ;
  regeneration of nerves, 211 ; endowments
   of, 212.  Spinal nerves, 269 ; their func-
  tions,  274 ;  how to  determine the function
   of a nerve, 272 ; peripheral  disposition of
  nerves necessary for  reflex  actions, 298 ;
   of arteries, 654;  compound encephalic,
   481; encephalic, 271, 473 ; influence  of,
  on voice, 755 ;  of heart, 671;  of larynx,
   750 ;  of liver, 778 ;  spinal, 269; of nose,
   396 ;  of spleen, 813 ;  of stomach, 546; of
   taste,  386 ; termination of, in  skin, 359 ;
   of uterus, 844 ;  of villi, 578
 Terves,  auditory, portio mollis, 461;  portio
  dura, 462; chorda tympani, 117; cochlear,
  457, 461; posterior auricular, stylo-hyoid,
  submastoid, 478 ; eighth pair, 485 ;  excitor
  and motor, 273; facial, function of, 478;
  fourth  pair,  476 ;  fifth  pair, 396 ;  motor
  portion  of,  481;  distribution  of,  482;
  function  of, 483;  nasal  branch of, 423;
  ciliary, 423 ; function of, how determined,
  272; glosso-pharyngeal, 480, 485 ;  experi-
  ments  on,  756;  branches  to   ear, 462;
  ninth,  396; function of,  480;  olfactory,
  396 ; ophthalmic, 396 ; of Jacobson, 462 ;
  inferior cardiac, 504 ; laryngeal, effects of
  pressure upon, 756 ; nasal, connection with
  ophthalmic ganglion, 500 ; optic, 403, 421;
  petrosal, 501; of Pacinian corpuscles, 348 ;
  palatine,  501;  pneumogastric  to   heart,
  671; portio  dura,  425 ; sixth pair,  476 ;
  splanchnic,  503;  spinal accessory,  course
  of, 495 ;  submaxillary, 396 ; suboccipital,
  270 ; superficial petrosal,  477,  485 ; sym-
  pathetic,  to  heart, 671; third pair, action
  of, 430 ; function of, 474; to thyro-hyoid
  and  genio-hyoid  muscles,  480;  Vagus,
  488;  anterior  pulmonary  branches  of,
  489;   cervical  cardiac   branches,  489;
  oesophageal, posterior, pulmonary, pharyn-
  geal, superior and inferior laryngeal, tra-
  cheal, and  thoracic branches, 489 ;  vesti-
  bular, 459 ;  Vidian,  501
Nervi, molles, 502 ;  pathetici,  476
Nervous actions, examples of, 188, 212 ; their
  connection with  mind,   189,  217,  239 ;
  physical nervous actions, 190 ; laws of the
  nervous force, 214-217 ; course of nervous
  power in the centres,  262 ;  theory of certain
  nervous actions, 295 ; many need a double
  stimulus, 297 ; in vomiting,  565
Nervous  centres,  definition, 191 ; arrange-
  ment of tubular and vesicular elements in,
  199;  investing  membranes,   207, 228;
  structure of ganglia, 207 ; in the inverte-
  brata,  209;  spinal  cord,  208;  medulla
  oblongata,  239;  cerebellum,  245; meso-
  cephale,  248 ; cerebrum,  250 ;  inferences
  upon function of, 330
Nervous and electrical forces, 213; compared,
  218
Nervous matter, vital properties of, 68, 213;
  two forms  of, vesicular and fibrous, 191;
  physical and chemical properties of, 192 ;
  fibrous form of nervous matter, 193 ; tubu-
  lar fibre, its structure,  193;  gelatinous
  fibre,  its  structure, 196 ; vesicular nervous
  matter, simple and caudate vesicles, 197 ;
  development of nervous matter, 209 ;  re-
  generation of, 211
Nervous power, course of, 262
Nervous system of animal  life, 191; of  or-
  ganic life, 192 ; arrangement invertebrate
  and invertebrate  animals,  225; develop-
  ment of,  878 ; effect of lesions upon animal
  heat,  742 ;  influence of, upon animal heat,
  742
Neural arch of vertebrae, 865,  876
Newport Mr.,  on the generation of carbonic
  acid by bees, 725;  on the impregnation
  of the ovum, 838,  853;  on  the  nervous
  system of myriapoda, 290 ;  on  the spinal
  cord, 290; on the temperature of insects, 734 
INDEX.
919
Nipple, 899 ;  erection of, 356, 900
Nitrogen, exhalation of, 728; importance of,
  in food, 518
Nobili, on animal electricity, 334
Nodal lines, 464
Noise, definition of, 462
Nose, 391
Nostrils, 392
Nucleated nerve filaments of olfactory region,
  397
Nuclei of capillary vessels, 661
Nurse in metagenesis, 824
Nutrition of heart, 671
Nutritive food,  516
Nutritive centre, 889

 Obstruction,  effect of, upon the action of
   the intestines, 584
 Ocelli, 402
 Ocular spectra,  434
 Odours, appreciation of, 400; of faeces, cause
   of, 610 ; occasioning syncope,  342
 (Esophagus, 544 ; motions  of, dependent on
   laryngeal nerves, 491
 O'Ferrall on the tunica vaginalis oculi, 424
 Oil, its absorption, 625 ; globules of milk,
   901
 Oily alimentary materials, 515
 Oily matter, digestion  of, 561
 Olfactory, nerves, 396 ; processes,  or lobe,
   397 ; filaments, 397  ; region,  394
 Olivary columns, connection with portio dura,
   477
 Omentum, gastro-hepatic,  546
 Omphalo mesenteric duct,  870, 894
 Ophidia, intestinal canal in, 569
 Opium producing a polar state of the cord in
   cold-blooded animals, 281
  Ophthalmic ganglion,  423
  Optic nerve, effects of irritation of, upon the
    pupil, 475 ; incapacity of vision at its en-
    trance, 435
  Optic thalami, 250;   functions of,  310; at
    centres of sensation, 310 ; relation  to cor-
    pora striata, 311
  Optic tracts,  260, 421; connections of, 313
  Optic vesicle, 879
  Ora serrata, 409
  Orbit, 402
  Organic compounds, 29                   _
          chemistry, its importance to physi-
           ology, 51
          matter, its chemical constituents, 30
  Organized, bodies, distinctive characters of,
    32 ; origin of, 32; and unorganized bodies,
    27
  Ornithorynchus, 828
  Os internum, of uterus, 842
  Osseous zone, 452 ; labyrinth, 449
  Ossicles, of ear, 448 ; action of, in propaga-
    ting sound,  465 ; development of, 880
  Ossification of permanent teeth, 537
  Ostrich, generative organs of, 82»
  Otic ganglion, branches of, to ear, 462
  Otokonia, 443, 459
  Otolithes, 443, 459 ;  actum of, 471
  Ova, maturation of  848        .^    gM

  0Ta7t; ofduring the' period of heat or rut,

  OvfcL, number of in  ovary, 848
Ovula Nabothi, 844
Ovum, 841 ; changes in, succeeding impreg-
  nation, 854 ; mammalian, yolk-sac of, 894 ;
  human, development of, 871; passage of,
  down Fallopian tube, 850
Owen, Professor, on the cerebral convolutions,
  254; on dentine, 527; on parthenogenesis,
  822;  on the vertebrate  theory, 877
Oxalate of lime, in urine, 799
Oxidation, nature of process in body, 741
Oxygen inhaled, amount of, 727

Pacchionian bodies, 233
Pachydermata,  intestinal canal of,  570 ;
  chorion in, 888
Pacinian  corpuscles, 345 ; nerves of, 349
Paget, Professor,  on the  areas of arteries,
   692 ; on the arteries and veins of the bat's
   wing, 662 ; on the multiplication of blood-
   corpuscles, 642; on the thymus, 818
Pain, 340
Pancreas, 766 ; in fishes, 569 ; effects of dis-
   ease of, 595 ; its  office in  digestion, 592 ;
   development of, 885
 Pancreatic duct, point at which it opens, 592
 Pancreatic fluid, its action on starch, 588 ; its
   action on fat, 594 ; abnormal, 594 ; method
   of obtaining it  in quantity, 592 ;  its cha-
   racters, 593, 594 ; in birds, dogs, horses and
   rabbits, 589, 594
 Pancreatine, 593
 Panizza,  on absorption by veins, 619 ; on the
   glosso-pharyngeal,  487 ;  section  of, 387 ;
   on lymphatic glands, 616
 Papillae,  circumvallatae, 381; compound con-
   ical, 382; epithelium of,  380; fungiform,
   380 ; capillary  vessels of,  359 ;  essential
   tissue of,  360 ;  of fore foot of male frog,
   282 ; effects of shaving off,  298 ;  of skin,
   358 ; nerves of,  359;  of  taste  compared
   with villi, 385 ; of teeth, 533 ; of tongue,
   hairlike, 383 ; their influence in taste, 389 ;
   function of, 389
 Papillary structure of tongue,  378
 Paralysis, of portio dura, 478; of oesophagus
   after section of vagus, 491; of fifth nerve,
   483 ; sensation in, 377 ; of sphincter am,
   299 ; third nerve, effects of, 475
 Paraplegia, 280, 302
 Parenchyma of kidney,  788
 Parietal sacculi, 775
 Parotid glands, 539
 Parovarium, 842, 886
 Parrot, no lingual branch of fifth nerve in,
    386
 Parthenogenesis, 822
 Par vagum, 488
 Pause in heart's action, 674
 Pecten,  409
 Peduncle of pineal body, 252
  Pelvis, 142 ; of kidney, 803
  Penis, 832 ; arteries of, 833 ; erection of,  de-
    pendent upon cord, 302    ,          .
  Penniform fibres of circular coat of arteries,
    651
  Pepsine, 556     •                     .   A
  Pereira, Dr.,  on contractility of  paralyzed
    limbs, 303                    A,     .   -
  Perfect vision, only in  or  near the axis oi
    vision, 436
 1 Pericardium, 666 
920
INDEX.
Perilymph, 453
Peritoneum,  568; of stomach,  546
Per saltum flow of blood in arteries, 681
Pes anserinus, 478
Petit, canal of, 417
Peyer's patches,  581; office of, 582 ;  secre-
  tion of odoriferous matter from, 610 ;  in
  typhus and typhoid fever, 582
Pharynx,  541
Phosphate in urine,  802
Phosphoric acid in digestion, 555
Phrenology,  324
Phthisis, Peyer's patches in,  582
Phvsiology, 324 ;  modes  of investigation in,
  47, 51
Physiological anatomy, meaning of the term,
  47 ;  its  bearing on practical  medicine, 47
Physical, movements of the cord, 280 ; nerv-
  ous actions, 280, 327, 340
Phyton, 820
Pig, stomach of, for  artificial digestive fluid,
  557
Pig which remained  160 days without food,
  739
Pia mater, 232
Pigment cells of choroid, 408
Pigment,  in  cuticle  of negro, 363; in hair,
  365
Pigmentum nigrum,  its uses, 434
Pillars of  the fauces, 542 ; of the fornix, 259
Pineal body, 252
Pinel on the functions of the corpora striata,
  and optic thalami, 311
Pitch,  of sounds, 463 ; of the note, how pro-
  duced,  753
Pitot, on measuring the velocity of the stream
  in rivers, 685
Pittard, on vesiculae  seminales,  831
Pituitary body, 261; regarded as a ganglion
  by some, 498
Placenta,  888
Placental  bruit, 890
Placental  mammalia, 828
Planaria, multiplication of, 820
Plastic elements of nutrition, 516
Pleasure and pain, 45
Pleuronecta,  optic lobes of, 312
Plexus, cavernous or carotid and tympanic,
  502 ;  inferior mesenteric, and hypogastric,
  504 ; cardiac and pulmonary, 504; gangli-
  formis,  488 ;  solar, phrenic, suprarenal,
  caeliac, hepatic, gastric and splenic, inferior
  mesenteric, renal and spermatic,  505
Plexuses of nerves, 203
Plica polonica, 367
Plica1 palmatae of uterus, 844
Pockels, M.,  on changes in  ovum after im-
  pregnation, 854; and  Coste,  on the deve-
  lopment of the  human  ovum, 871
Poiseuille, on the elasticity of arteries, 679 ;
  on the  haemadynamometer,  686  ; on the
  rate of the circulation, 705
Polar state of the  cord in the  male frog in
  spring, 281
Polyps, circulation in, 706 ;  multiplication,
  825 ; renal organs  of, 786
Pomum Adami, 747
Pons Tarini, 260, 261; Varolii, function of,
  329
Porosity of tissues, 66
Portal canals, 769, 772
| Portal, circulation in liver and in  kidneys,
   676 ; vein, 773
 Porterfield, on the adaptation of the  eye to
|   distances, 429
 Portio dura, 477 ;  communication with vagus,
   480 ; to orbicularis palpebrarum,  425
 Portio intermedia, 461, -177
 Posterior commissure, 258 ; columns of cord,
   283 ; functions of,  285
 Potash acetate, its absorption, 611
 Potash salts in urine, 799
 Pourfour du Petit, on the office of  the sym-
   pathetic, 510                 .
 Prehension, 523                \
 Presbyopia, 431
 Prevost, on  the movements of spermatozoa,
   837 ; and Lebert, on the contraction  of the
   heart before the development of muscular
   fibre, 882
 Primitive streak,  865, 866
 Processus cerebelli ad testem, 249 ; cochleari-
   formis, 447
 Prochaska on capillaries, 662
 Promontory, 447
 Proper current of the frog, 334
 Prosencephala; vertebrae, 876
 Prostate gland, 831
 Prostatic portion of the urethra, 833
 Proteine, 56
 Proteus, kidney of, 790
 Prout, Dr., on the acid of the gastric juice,
   557; experiments  on  digestion,  554;  on
   the effects of alcohol  in respiration 725 ,
   on the classification of food, 514  ; on  the
   gastric juice, 554; on the absorption  of the
   yolk, 894
 Proximate principles,  29, 30,  52
 Puberty, 846
 Pulmonary, artery, 707 ;  sacs, 707; tissue,
   709; veins, 666
 Pulmonic circulation,  676
 Pulp, cavity of tooth,  526
 Pulse, 674, 681; quality of, 682 ; small, hard,
   wiry, 684; of marmot during hibernation,
   740
 Puncta lachrymalia, 426
 Pupil, 411
 Purgatives, saline, action of,  624
 Purkinje, and Pappenheim,  on artificial  di-
   gestion, 562; and Valentin, on ciliated epi-
   thelium of lateral ventricles, 262
 Putrefaction, 39
 Pyloric, follicles in fishes, 569 ; tubes, 549 ;
   valve in fishes,  569
 Pylorus, characters of the mucous membrane
   of, 549 ;  effects of obstruction of, 563
 Pvramids of tympanum, 447 ; of kidney,
  '788
 Pyramidal  bodies of medulla, disease  of,
   305

 Quaorumana, intestinal canal of, 571
 Quality of sounds, 4.63
 Quantity of bile   secreted  in  twenty-four
   hours, 784; of blood in the body, 630 ; of
   urine, 798

 Rabbit, development of spermatozoa in, 837 ;
   pancreatic duct of, 592
 Rainey, Mr., on epithelium of serous  mem-
   branes, 762;  on  the  ligaments  of  the 
INDEX.
921
  uterus, 845 ;  on the pulmonary capillaries,

Ransom, Dr., on the micropyle, 854
Rapp on the nerves of taste," 386
Rat, spermatozoa of, 836
Rate of the circulation, 704
Reaction of healthy urine, 798
Reaumur  on  gastric juice, 552;  and Spal-
  lanzani on the movements of the stomach,
  551
Receptaculum,  chyli, 612; seminis, 827
Recrementitious substances, 759
Rectum, 568, 608 .-  folds of, 575
Red blood-corpuscles, 634 ; chemical compo •
  sition of, 644
Rees, Dr.  G. 0., analysis of bone, 104; analy-
  sis of lymph  and chyle, 022 ; on extractive
  matters in the urine, 802 ; on urea in milk,
  800
Reflex actions,  imperfectly controlled by the
  will, 296 : in vomiting, 566
Reflection, laws of, 427; from retina, 432
Refracting media of eye, 402 ; power of vit-
  reous body, 417 .- of lens, 420
Regnault  and  Reiset  on the  relation  of
  oxvgen and carbonic  acid in respired air,
  727
Regurgitant venous pulse, 700
Regurgitation  through  valves of heart pre-
  vented, 669
Reichert, on  the development of the  allan-
  tois, 895 ; of the liver, 885 ; of the lungs,
  883; nervous  system,  878:  on  the in-
  vesting membrane  and membrana  inter-
  media,  864
Reid,  Dr.  John, on asphyxia, 699 :  on the
  arrangement of  the  fibres of the heart,
  670 ; on the glosso-pharyngeal, 486 ;  on
  contractility, 303 ;  experiments on laryn-
  geal nerves, 491 ; on  the  influence of the
  nerves in hunger, 521; on loss of nutrition
  in paralyzed  muscles, 303;  on the  sympa-
  thetic, 510
Remak on the ganglia and nerves of the
  heart, 505, 672 ; on the development of the
  liver, 885
Rennet, 556
Reproduction,  33, 819
Reptiles,  air-cells of, 716 ; blood corpuscles
  of, 635;  circulation  in,  707 ;  digestive
  organs  of, 513 ;  heart  of,  663 ; intestinal
  canal in, 569;  generative  organs  of, 828 ;
  organ of hearing, 444;  spermatozoa  of,
  836
Resilience of lungs, 720
Respiration,  conditions of,  707;  partly a
  physical and partly  a chemical  process,
  732; influence  of, upon the circulation,
  689 ; movements of,  716 ;  objects of, 732 ;
  theory  of,  731 ; connection of function  of
  liver with,   602; effects  of  temperature
  upon, 725 ;  effects  of posture upon,  722 ;
  influence of  vagus in, 492
Respirations, frequency, and  ratio to pulse,
  722
Respiratory, compartment of the  pharynx,
  542  ; movements, excitation of, 721  : l.y the
  application of cold to the surface, 726; mu-
  cous membrane, 523
Restiform bodies, functions of, 306
Rete Malpighi or mucosum,  3(>2
                                    59*
Rete mirabile, 658
Retina, 413 ;  capillaries of, 660 ;  connection
  with sensorium, 436
Retinae, corresponding points in each, 441
Retinacula, 840
Retzius  on  the arrangement of  the  liver
  cells, 780 ; on the hemispheres of the brain,
  S7S; his preparations of the lung of the
  calf, 7.12
Rheumatism, diet in, 520
Rhinencephalic vertebra, 877
l!i'>es, ganglion of,  498
Ridges of cuticle, :S57
Rinor mortis, 178 ; in arteries, 684 ; in mus-
  cles, 179
Ritchie, Dr., on the rupture of  ovisacs in
  children, 848
Robinson, Dr.,  on absorption, 626
Rodentia, intestinal canal of, 570 ; chorion
  of,  888
Rodier, his analysis of the blood, 644
Rods  of enamel, 530 ; of Jacob's membrane,
  415
Roe of fishes, 827
Rolando, his experiments  on the cerebellum,
  318
Roots of the  fifth nerve, 4S1 ; of the spinal
  nerves, 270 ;  of the sympathetic, 499
Roots of the  tooth,  526
Rossignol on pulmonary tissue, 712
Rotation of the yolk, 855
Ruga1 of uterus, 844
Rumbold  and  Fowler,  experiments on  the
  third nerve, 475
Rumination,  564
Ruminantia,  action of  oesophagus  in, 545 ;
  digestive organs  of, 513;  intestinal  canal
  of,  570 ; chorion  of, 888
Rumkorff's galvanometer, 331
Rut in animals, 849
Rhythm of the heart, 074

Saccharine alimentary materials,  515
Sacculus, 443, 458
Sacculated bladder, 804
Saline constituents of bile, 600
Saline solutions, action of,  upon the move-
  ments of the spermatozoa, 8^7
Saliva, uses of, 541
Salter, Dr. Hyde, on the pancreas,  785
Salter, Mr. S. J. A., on the anatomy of veins,
  659
Salts, fixed,  in urine, 802
Sanders, Dr., on the spleen, 812
Sarcolemma  of muscular fibre, 150
Sarcous  elements  of muscular  tissue, 147,
  150
Saucerotte on the functions of the optic tha-
  lami and corpora striata, 311
Sauria, intestinal  canal of, 509;  generative
  organs, 828
Savart, on the formation of the voice, 751;
  on  hearing,  463, 468 ;  on the time which
  sensations of sound last, 47-'J
Savi, on electrical organs, 350
Scala, tympani, vestibuli, 452
Scaly epithelium, 523
Scaphoid fossa, 445
Scarpa, on the nerves of the heart, 672 ; on
  the spinal  accessory nerve, 496
Scharling, on the influence of digestion upon 
922
INDEX.
  the quantity of carbonic acid exhaled, 724 ;
  on the quantity of carbonic acid removed
  from the body, 730
Scherer, upon iron in  the blood, 645 ;  upon
  the form of the blood-corpuscle in arterial
  and venous blood, 729
Schneiderian membrane, 392
Schulz, on the acid fluid secreted in the cae-
  cum, 608
Schwann,  Professor,  his  experiments  upon
  the secretion of bile, 601; and  Muller on
  pepsine, 556
Sclerotic,  of eye, 403 ; in aquatic mammalia,
  birds, and reptiles, 403
Sclerous tissue, 62
Scrotum, 829
Scurvy, causes of, 517
Sea-sickness, how produced, 494
Sebaceous follicles of nose, 392
Sebaceous glands, 370, 372 ; of labia, 846.
Secondary organic compounds, 30, 52,  60
Secreting organs, general view of, 761
Secretion, 757 ;  of Brunner's glands,  580 ;
  of pancreas, 592; of urine, 796
Section of hair,  method of making, 365
Seguin and  Lavoisier,  on the influence  of
  temperature on the exhalation of carbonic
  acid, 725
Sella Turcica, 264
Semicircular canals, 450 ; membranous, 458 ;
  action of,  472; development of, 880
Semilunar valves, 664
Seminal tubules, 830, 835
Sensation, 45;  centres of,  305,  308,  310;
  common and special, 69,  214,  352;  me-
  chanism of,  293,  301.  305 ;  subjective,
  objective, 352, 377 ; sympathetic, 340 ;  of
  temperature, 377
Sense,  muscular, 373
Sensibility of palms of hands and feet, 374
Septal  cartilage  of nose, 392
Septum lucidum, 259
Serous  membranes,   128;  structure,  129;
  physical and vital properties, 130;  inflam-
  mation, adhesion of, 130
Serous and mucous laminae of bird's egg, 864
Serous pericardium, 666
Serous or animal layer of the germinal mem-
  brane, 859
Serres, on corpora quadrigemina, 312
Serum, 628; of blood, 633
Sexual instinct,  is it seated  in the cerebel-
  lum? 317
Sexual organs, 824
Shaft of hair, 364
Shape and size, visual perception  of,  438
Sharks and rays, mucous tubes of, 371
Sharpey, Dr., on ciliary movement,  76 ; on
  the force of the heart, 678 ;  on the forma-
  tion  of the decidua, 860 ; his investiga-
  tions upon an  early human embryo, 894
Sheaths of the arteries in the spleen, 810
Shortsightedness, 430
Sibson, Dr., on the  action of the intercostal
  muscles, 719;  on  the movement  of the
  ribs  in inspiration, 717
Siebold, Van, on cystic entozoa, 823
Sighing, yawning, coughing, their depend-
  ence on the medulla oblongata, 306
Sigmoid flexure  of the colon, 567
Silica in urine, 799
Simon,  Dr.  Franz, on  demodev,  371;  on
  ptyalin, 540 ;  on the  blood of the  vena
  porta, 645 ; analysis of milk, 902
Simon,  Mr.  J.,  on fibrine as a  product of
  decay, 647 ; on the use of the thymus, 817  ;
  on the use of the thyroid, 816
Singing, 754
Sinus,  rhomboidalis,  879;  urino-genitalis,
  895 ; venosus, 665
Sinuses of the nose, 391
Sixth nerves, 476
Skeleton, external and  internal, 102;  me-
  chanism of, 136
Skin, absorption through, 611 ; contractility
  of, 355 ; functions  of,  371; general ana-
  tomy of, 354; tanned,  355 ; termination
  of nerves in, 359
Skin of external ear,  445
Sleep, effects of upon  the temperature of the
  body, 736
Sleep and somnambulism,  327
Small intestine, 567
Smegma preputii, 835
Smell,  391; conditions of, 399
Smith, Dr. Tyler, on the cause of birth, 897
Smith and Harris,  on  the smallest portion of
  the retina capable  of independent  sensa-
  tion, 437
Snow,  Dr.,  experiments of the deleterious
  nature of respired air, 728; on the quan-
  tity of carbonic acid expelled after the in-
  halation of chloroform and ether, 725
Soda salts in urine, 799
Soemmering on the yellow spot, 415
Soft, palate, 542 ; commissure, 258
Solid and fluid constituents of animal bodies,
  51
Solipeds, intestinal canal of, 570
Solitary glands, 580
Solution of meat,  albumen, etc., in gastric
  juice, 555, 560
Somnambulism,  328
Soprano voice, 754
Sound,  nature  of  laws of transmission of,
  462 ;  length which  a sensation lasts, 473 ;
  velocity of, 462
Sounds of heart, 673 ; vocal, how modified,
  439
Spallanzani, experiments on saliva, 541; on
  digestion, 552; on  the  movements of the
  stomach, 551
Specific  gravity of bile,  598 ; blood,  633;
  milk, 628 ; urine, 798
Spectrum, solar, 427
Speech, 756
Spengler, on the  pressure of the  blood in
  different arteries, 688
Spermatozoa, in seminal tubules, 835 ; move-
  ments of, 837 ; their motions analogous to
  the ciliary, 77
Sperm-cell, 821
Spheno-palatine foramen, 399
Spherical aberration,  427 ; prevented bv iris,
  431
Sphincter vesicae, 805
Sphincters, action of, 180, 299
Spinal accessory nerve,  495
Spinal column, 137;  development of, 875
Spinal cord, 208 ;  antero-lateral columns of,
  283;  descriptive anatomy, 233; minute
  anatomy,  235 ; course of fibres, 237; func- 
INDEX.
923
  tions, 275,  2S2 ;  its share in mental and
  physical nervous actions, 275, 301 ;  polar
  state of,  281; mechanism of its actions,
  287 ; effect of injury below the phrenics,
  304 ; lumbar region of, 286 ;  functions of,
  in  vertebral  animals, 278 ; hypothesis,  to
  explain the action of, 287 ; of Dr. Marshall
  Hall, Whytt, Prochaska, 288 ;  effects  of
  mental emotions on actions, 289
Spinal nerves, their double roots, 270 ; their
  functions, 274
Spiral duct of sweat-gland, use of, 370
Spirometer, 723
Spleen, 806, 885;  the seat of destruction of
  blood-corpuscles, 643 ;  uses of, 813 ;  pulp,
Spongy portion of urethra, 834
Spore, or sporangium, 821
Squalus cornubicus, testicle of, 763
Squirrel, spermatozoa of, 836
Stammering, 756
Starch, digestion of, 560, 5S9 ; its conversion
  into  dextrine  by  pancreatic fluid,  589;
  sugar, cellulose, etc., as calorifacient food,
  740
Stannius, on pancreas of fishes, 592
Stapes, 448
Stark, Dr., effects of a diet without azotized
  food,  518
Stearine, 59, 90
Steenstrup, on the alternation of generations,
  822
Stentor, multiplication of, 825
Stereoscope, 441
Stevens on digestion, 552
Stilling, on  the fibres of the optic thalami,
  310;  and Wallach, on the roots of the
  nerves, 271 ;  on the spinal cord, 236, 243
 Stimuli, to muscle, 165 ;  all act on the mus-
  cular tissue  itself, 166 ;  to nerves, 165,
  215 ;  a double stimulus necessary to many
  nervous actions, 297
 Stomach, 545; vermicular  contractions  of,
  caused by irritation of the vagi, 492 ;  its
  part in vomiting, 565 ; movements of, 550
 Stone in the bladder, sympathetic sensations
  produced by, 340
 Straight portion of uriniferous tube, ?lJ^
 Strecker on the composition of the bile, 600
 Striped muscular fibre of the heart, 669
 Strobila, multiplication  of, 742
 Strychnine, its action on the cord, 281
 Subjective  phenomena  of hearing,  473
   smell, 401;  of taste, 390
 Submaxillary  glands, 539
 Submucous tissue, 5i2
 Succus gastricus, 554
 Suction-power of auricles, 702
 Sugar, in blood, 633;  formed  in the liver
   605 ; formed from starch, 589 ; effects  of
   feeding dogs on, 518
 Sulphates in urine,  802
 Sulphocyanides in saliva, 540
 Sulphuretted  hydrogen m intestines, 610


 Supra renal Lpsules, 814; development of
Sympathetic, 498 ; cervical ganglia of, 502 ;
  lumbar and sacral portions of, 504 ;  cervi-
  cal portion of, 501;  endowment  of fibres
  of,  508 ;   effect  of section of, on animal
  heat, 743 ; effects of division of trunk of,
  510 ;  function of, 506 ; sensations, 340
Sympathy,  sympathetic sensations  and mo-
  tions, 339 ; between digestive and respi-
  ratory organs, 493 ; contiguous,  345
Sympathies, affecting the mind, 341
Synarthrosis, 132
Synovia, 128
Synovial sheath, 127, 129
Syphilitic poison, its absorption, 619
Systole, 072 : and diastole, their influence on
  the circulation,  689
of
Supra-orbitar convolution, 255
Sweat-glands  368
Sylvius, aqueduct ot, -oi
Tactile papillae, 356
Tape-worm, multiplication of, 820
Tapetum lucidum, 409 ;  reflection from, 433
Tarsal cartilage, 424
Tartar emetic, 566
Taste, conditions of,  388;  heightened by
   motion,  388; influence of movements of
   tongue upon, 389 ;  nerves of, 386 ; precise
   seat of, 385 ; persistence of after section of
   glosso-pharyngeal, 387 ; in soft palate, 386 ;
   influence of smell upon, 388 ; varieties of,
   389
Taste and touch, do they coexist in any of
   the papilbc ; 389
Tastes, bitter, 388
Taurin, 598
Tea, effects of, upon  the exhalation  of car-
   bonic acid, 725
Teeth, 525 ; development of, 532; number of,
   536
Temperature, of blood, 629 ; of human body,
   735 ; its effects upon respiration, 725 ; ele-
   vation of, after section of the sympathetic,
   743
Temporary teeth, 536
Tench, striped muscular fibres  in intestine
   of, 510
 Tendo oculi,  424
| Tendons, 81
 Tenor voice,  754
 Termination  of nerves,  161, 201
 Testicles, 829 ; of insects, 827
 Tetanus, 280
 Thackrah, his experiments on the coagulation
   of the blood, 631
 Theile, on vasa aberrantia, 776
 Theory and hypothesis, 20
 Third nerve, function of,  174
 Third ventricle of brain,  252
 Thirst,  522
 Thomson, Dr. R. D.,  on volume of carbonic
   acid in expired air, 72 t; on the acid of the
   gastric juice,  558 ; on calorifacient food,
   516 ;  on milky serum, 63.".
 Thomson, Dr. Allen,  on the development  of
   the human ovum, 871
 Thoracic duct, 612 ; contractility of, &lo
 Thorax, 140 ; enlargement of, in respiration,
    716
  Thymus, 816
  Thyro-hyoid ligaments, 748
  Thyroid,  815; cartilage,  746;  development
    of, 883
  Tic douloureux, 484 
924
INDEX.
Tiedemann and Gmelin, on chyle, C21; on j
  the digestion of starch, 560 ; experiments
  on the~uses of the bile, 603
Timbre of sound, 463
Tingling, tickling, sensations of, 377
Tinnitus aurium, 473
Tissues, composed of cells, 62 ; their classifi-
  cation and  properties, 61;  properties of,
  65, 68
Taenia semicircularis, 260
Tomes, Mr., his researches  on bone, 111, et\
  seq.; on the granular layer of dentine, 529
Tone,  of arteries, 683 ; of muscular system,
  influence of cord upon, 302
Tongue, as  an organ  of mastication,  388;
  motor nerve  of, 480 ;  movements  of in
  deglutition,  543;  its use as a prehensile
  organ, 524;  its use in mastication,  525;
  portion in which taste resides, 387 ;  used
  in suction, 524
Tonicity of muscle, 164; identical with con-
  tractility, 166; not derived  from the cord,
  302
Tonsils, 543 ; nerves of, 486
Tooth bone, 531
Torpedo, Matteucci's experiments upon, 338
Tortoise, intestinal canal of, 569 ;  urine of,
  801
Touch, 352 ; diffusion of sense of, in man,
  374 ; in animals, 373 ; organ of, 373 ; ex-
  isting in the tongue, 388
Toynbee, Mr., his researches on cartilage, 99
Trabeculse of  penis, 833
Trabecular tissue of spleen, 807
Trachea, 708 ;  development of, 883
Tracheae, 707
Tracheal glands, 708
Trachealis muscle, 708;  use of, 721
Tragus of ear, 445
Training, diet in, 520
Transverse fissure of liver, 769
Tricuspid valve, 664
Trigone of bladder, 804
Triple phosphate in urine, 799
Triton, generative organs of, 828
Trunk of elephant, supplied by portio dura,
  478
Tuber cinereum, 260
Tubes, of dentine, 528 ;  of stomach, 548 ; of
  cornea, 405
Tubular nerve fibres in syrup, 507
Tubuli, dentinal, 530
Tufts  of chorion, 862
Tunica, albuginea and vaginalis testis, 829 ;
  granulosa,  840 ; media of Bischoff, 874;
  Ruyschiana, 408; vaginalis oculi, 424
Tunicata,  multiplication  of, by  budding,
   825 ; heart of, 663
Tympanitis, 610
Tympanic,  cavity, 446; plexus, 485;  ring,
   445
 Tvmpanum, its contents, 465 ;  use of, 468 :
  "internal wall of, 446
 Typhus and typhoid fever, Peyer's  patches
   in,  582

 Ultimate facts, 25
 Umbilical, arteries, 895 ; cord, 897 ;  vesicle,
   893 ; vessels, 897
 Unisexual generation, 824
 Unstriped muscle of absorbents, 614
Urachus, 896
Urea, 800; in blood, 634; in milk, 903
Ureters, 804; muscularity of, 705
Urethra, female, 846 ; male, 833 ; muscularity
  of the, 765; development of, 833
Uric or lithic acid, 800 ;  in allantoic fluid,
  897
Urinary bladder, 804 ;  development of, 896
Urine, 797; analysis of healthy, 799; secre-
  tion of,  796;  diminution of  constituents
  from taking alcohol, 725
Uriniferous tubes, 789 ; continuity of, with
  the capsule of the Malpighi!; n body, 790
Uterus, 84-2 ;  its action in parturition, 302;
  masculinus, 835
Uteri in marsupialia, 828
Uterine sinuses, 890
Utriculus, 443, 458
Uvea, 411
Uvula vc-icae, 833

Vagi, distribution of, 488; motor branches
  of, 490 ;  office of gastric branches of, 492
Vagina, 845
Vagus, conclusions with respect to function,
  494;  section of, by  Dr. J. Reid, 49]  ;  its
  importance in respiration, 492
Valentin,  on  the exhalation  of  aqueous
  vapour, 724 ;  on the cause  of the impulse
  of the heart, 673 ; on the  cause of birth,
  897 ; on circulation in the capillaries,  694 ;
  on the rate of the circulation, 704; on the
  force of the heart,  678 ;  on the force of the
  respiratory muscles, 721 ; experiments  on
  spinal nerves, and their influence  on sym-
  pathetic, 511; on the  quantity of blood,
  030;  and  Brunner  on  the  proportion of
  oxygen and  carbonic acid in respired air,
  724, 727; and Mogk, on the force of the
  current in the veins, 701; Schubert and
  Panizza, experiments on nerves, 275; and
  Wagner, on section of  the  glosso-pharyn-
  geal,  387 ;  and Wagner, on taste,  386
Valves,  of absorbents, 614;  of the heart,
  664;  structure  of, 667 ;  ileo-caecal,  575 ;
  mechanism,  669;  of Thebesius,  666;  of
  the umbilical vesicle, 893 ; of veins,  659 ;
  of Vieussens, 250
Valvulae conniventes,  574
Van Deen, experiments upon animals poisoned
  by strychnine, 299
Varicose veins,  influence  of gravity on, 704
Vas,  deferens,  830;  development  of,  887;
  rectum testis, 830
Vasa, aberrantia, 776 ; efferentia, 830; lutea,
  893 ; vasorum of arteries, 650 ; vorticosa,
  408
Vascular area, 867 ; glands, 806
Vauquelin, on ashes of hair, 367 ; on colour
  of hair, 307
Vegetable substances, digestion of, 560
Vein, portal, 773
Veins, 658;  of choroid, 407; circulation in,
   700; coats of, 658;  valves, 659 ; circula-
  tion  in, of bat's  wing, 703 ; pulmonary,
  666 ; of spleen, 812
Velocity of the circulation in arteries, 690
Velpeau, on the allantois, 897; on the corps
  reticule, 892
Velum interpositum, 252
Venae cavae, 658 ; magnae Galeni, 266 
INDEX.
925
Venesection, influence of, upon blood, 646 ;
  over fibrine, 646
Venous blood, 629, 645 ; absorption by, 562
Venous circulation, favoured by  muscular
  movements, 702 ; influence of respiratory
  movements,  701 ;   influence  of gravity
  upon, 703
Venous pulse, 700
Ventilation, importance of,  728
Ventral laminae, 867
Ventricles of heart, 664; force of left, 686
Ventricle, fifth, 260
Ventricles of the  brain, third, lateral, 248,
  261
Venus ehione, heart of, 663
Vermicular action of intestines, 583
Vermiform appendix, 571
Vernix caseosa, 875
Yerschuir on irritability of  arteries, 682
Vertebra, typical, 876
Vertebral, arches,  876 ; arteries, 264, 656 ;
  plates,  865
Vertebrata, generation in, 827; pancreas in,
  592
Vertigo, 325 ; from lesion of corpora quadri-
  gemina, 313
Yerumontanum, 834
 Vessels, of the iris, 412 ; of the kidney, 793;
  nose, 392 ; of the lungs, 712 ; of the retina,
  414; umbilical, 897
 Vesiculae seminales, 831
 Vesicular gray layer of retina, 414
 Vestibule, 449 ;  the  essential part of  the
   organ of hearing, 469
 Vicarious secretion, 760
 Vierordt, on the proportion of carbonic acid
   in expired air, 724, 727
 Villi,  576; capillaries, lacteals,  and  nerves
   of, 577 : during  intestinal digestion, 585 ;
   of intestines compared to papillae, 385
 Vinegar, formation of, 741
 Virehow, on the spleen, 810
 Vis nervosa, 217
 Vis, a fronte, 696; a  tergo,  678,  694; in-
   fluence in venous circulation, 700
 Visceral  arches, development of, 877
 Vision, development of organs of, 879 ; cor-
   pora quadrigemina, the special ganglia of,
   313;  distinct,  428; organ of, 401; phe-
   nomena of, 427
 Visual, angle, 428
 Vital  capacity, 723;  properties, 36, 68; of
   tissues, 68 ; stimuli, 36
 Vitelline, membrane, 841;  duct, 894
 Vitreous body, 416
 Vocal cords,  747
 Vogt, on the origination of blood corpuscles,
   639 ;  on the liquor amnii, 892
 Voice, 744
 Volition, 45                             .,
 Volkmann, on the circulation in the capil-
   laries,  094 ;  on contraction of  lymphatic
   hearts, 618 ; on  the force of the heart 68
   on the haemadromoineter. 690 ; on the rate
   of the circulation, 704             „plirT.P<i
 Voluntary motion, 275 ; movements, centres

 Vomitint',350693; caused by section  of vagi
   °S3 , effect of-rvo,, changes upon,^,

   ^K^  P.odtced^y irritation of
  vagus, 494;  oesophagus in, 545;  sympa-
  thetic of diseased  kidney, or passage of a
  calculus along the ureter, 341
Vorticelloe, multiplication of,  823 ;  reproduc-
  tion of, 820
Vowel sounds, production of, 756

Wagner,  on development of  spermatozoa,
  836 ;  on white  corpuscles, 641;  on  the
  changes in the germinal vesicle,  855 ; and
  Muller on the development of the human
  ovum, 872
Walknaer, on the  division of the cord in in-
  sects, 300
Wallace,  Dr. Clay, on  the  action  of  the
  ciliarv muscle, 430
Ward, Mr., on  the skeleton, 139, 1-12
Warm-blooded  animals, 734
Water, as  a constituent of animal bodies, 52 ;
  removal of, from body, 760
Weber, on castor,  835 ; on the circulation in
  the capillaries,  694; on appreciating  the
  weight  of bodies, 376; on  formation of
  decidua,  860 :  on the  generation  of  the
  blood-corpuscles in  the liver, 639 ;  on ir-
  ritation of arteries, 683 ; on  the organ of
  hearing in  fishes,  443 ;   on the  striped
  muscular fibres in  the intestine  of the
  loach, 510 ;  on  vasa aberrantia, 776 ;  on
  the relation of the fcetal vessels  to those of
  the mother, 889
Weber and Goodsir on the placenta, 889
Weberian organ, 835,  887
Webster, Dr., his case  of paralysis  of motion,
  283
Wedemeyer  and Guenther,  on the suction-
  power of the auricles,  702
Weight, power of appreciating, 376;  of the
  human heart, 664; of spleen, 806
Whale, the skin of, 356 ; teeth of,  526
Wheatstone, Professor,  on  semicircular ca-
  nals, 472 ; on the stereoscope, 441
White blood-corpuscles,  637
White  chyle, influence  of  pancreatic fluid
  on the formation of, 593
White of the eye,  403
White fibrous tissue, 80 ; in the cutis, 354;
  common description of, incorrect, 80 ; its
   vessels  and nerves, 80 ; chemical composi-
   tion, 80 ; reparation of, 82
 Whytt, cases of numbness of arm, etc., asso-
   ciated with  suppuration of the  liver, 340 ;
   Prochaska,  Blane,  and Flourens,  on  the
   excitation of involuntary movements, 280
 Will, influence of, upon the spinal cord,  293
 Willis, his arrangement of the  encephalic
   nerves, 271; circle of, 265, 656 ;  on  the
   aperture of the glottis, 751 ; on  the  pro-
   duction of vocal sounds, 752 ; on the func-
   tions of the cerebral convolutions,  323
 Wind, action of cold increased by, 738
 Woliler and Frerichs on  the formation of
   urea from uric  acid, 801
 Wolffian  bodies, 886
 Wollaston, Dr., on the effects of tension of
   the membrana tympani, 469 ;  and Mayo,
   on the course of the nerves in optic tracts,
   440
 Women,  analysis  of blood of, 644
 Wright, Dr., on saliva, 540
 Wrisberg, portio  intermedia of, 461 
926
INDEX.
Yellow fever, temperature in, 739
Yellow fibrous tissue, structure and  proper-
  ties of, 82 ; in the cutis, 354;  at the bor-
  der of the anterior elastic lamina, 411
Yolk granules, 841; sac of mammalian ovum,
  894
Young, Dr.,  lectures on the functions of the
  heart and arteries, 688
Zimmermann,  on fibrine as  a product  of
  decay of tissues, 647
Zinn,  zone of, 416
Zona pellucida, 841
Zonula ciliaris,  or, of Zinn, 416
Zwicky, Dr., on yellow  matter of corpus
  luteum, 850
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to their library.  *  * * This treatise is quite in- (
dispensable to all who aspire to keep up their know-
ledge with the high standard of the present day.  *
*  *   We must congratulate Dr.  Todd and Mr.
Bowman, and especially the latter gentleman, that
they have been able  by their admirable and skilful
observations to throw  so  much new light on  the
delicate organization of many important parts; ti
merit  this of no  ordinary kind, when it is recol-
lected that the intimate texture of the organs  to
which we refer has been made the subject ot labori-
ous and repealed investigations  by several of  the
most distinguished microscopists of Europe.—Medi-
co-Chirurgical Review.
  It cannot fail to recommend itself to students by
the clearness of description and the accuracy of the
illustrations  met  with in every chapter: and we do
not hesitate to express our opinion that it supplies a
void which has hitherto  existed between works es-
pecially devoted to anatomy and physiology.  The
engravings represent not only those parts of anato-
my which can be easily traced with the scalpel, and
which really need no other illustration than that met
with in the dissecting-room, but  by the aid of the
microscope and of sundry chemical appliances, tln-v
carry him into the intimate structure of organs, anil
lay bare to the eye the most minute subdivisions of
vessels and nerves.  *  *  *  The chaptersare not
encumbered with unnecessary details; and those
parts of physics which  are required for the under-
standing of the physiology of the senses, are con-
cisely given in the form of notes   #  #  #  It will
form, when completed, a most useful addition to the
library of every student and practitioner who sets a
value upon the scientific knowledge of his profes-
sion —London Medical Gazette. 
               ULAJNGHARD  &  LEA'S
MEDICAL  AND  SURGICAL  PUBLICATIONS.
                   TO THE MEDICAL  PROFESSION.
  In the present catalogue we have affixed prices to  our publications, in obedience
to the repeated  requests of numerous members of the profession.   While books,
like all other articles, must necessarily vary  somewhat in cost throughout the ex-
tended territories of this country, yet our publications will  generally be furnished
at these rates by booksellers throughout the Union, who can  readily and speedily
procure any which they may not have on hand.
  To accommodate those physicians who have not convenient access  to bookstores,
or who cannot  order through  merchants visiting the larger  cities, we will forward
our works by mail, free of postage,  on receipt of the printed  prices in  current funds
or postage stamps.   As our business is wholesale, and we open accounts with book-
sellers  only, the amount must in every case, without exception, accompany the
order, and we can  assume no risks  of the mail, either on the money or the books;
and as we only sell our own  publications, we can supply no  others.  Physicians
will, therefore, see the convenience and advantage of making their purchases, when-
ever practicable, from the nearest bookseller.
  We can only add that no exertions are spared to merit a continuance of the
gratifying confidence hitherto manifested by the profession in all  works bearing our
imprint.
                                                 BLANCHARD & LEA.
  Philadelphia, March, 1857.
  *,* A copy of our new Illustrated Catalogue, 80 pages, octavo, will be sent free
to any address on receipt of nine cents in postage stamps.  Catalogues of our nume-
rous publications in miscellaneous and educational literature forwarded on application.
   TWO MEDICAL  PERIODICALS,  FREE OF POSTAGE,

          FOR FIVE DOLLARS  PER  AUOTUM.

THE AMERICAN JOURNAL  OF THE  MEDICAL SCIENCES, subject to
  postage, when not paid for in advance,    -    -    -    -    -    -    -$5 00
THE MEDICAL NEWS AND  LIBRARY, invariably in advance,   -    -   1 00
  or, both periodicals furnished, free of  postage, for Five Dollars remitted
  in advance.
  THE  AMERICAN  JOURNAL  OF THE MEDICAL SCIENCES,

                  Edited  b?  ISAAC HAYS, M. D.,
is published Quarterly, on the first of January, April, July, and October. Each number contains
at least two hundred and eighty large  octavo pages, handsomely and appropriately illustrated,
wherever necessary. It has now been issued regularly for more than thirty-five years, and it has
been under the control of the present editor for more than a quarter of a century.  Throughout
this long period, it has maintained its position in the highest rank of medical periodicals both at home
and abroad, and has received the cordial support of the entire profession in this country.  Its list ot
Collaborators will be found to contain a large number of the most distinguished names of the pro-
fession in every section of the United States, rendering the department devoted to

                ORIGINAL  COMMUNICATIONS
full of varied and important matter, of great interest to all practitioners.         -
  As the aim of the Journal, however, is to combine the advantages presented by all the different
varieties of periodicals, in its
                     REVIEW  DEPARTMENT
will be found extended and impartial reviews  of all important new works, presenting subjects of
novelty and interest, together with very numerous
                BIBLIOGRAPHICAL NOTICES,
inolnHino- nearlv all the medical publications of the day, both in this country and Great Britain, with
a choice selection of the more important continental works. This is followed by the 
2
BLANCHARD & LEA'S  MEDICAL
                           QUARTERLY SUMMARY,
being a very full and complete abstract, methodically arranged, of the

           IMPROVEMENTS AND DISCOVERIES IN  THE MEDICAL  SCIENCES.

  This department of the Journal, so important to the practising physician, is the object of especial
care on the part of the editor. It is classified and arranged under different heads, thus facilitating
the researches of the reader in pursuit of particular subjects, and will be found to present a very
full and accurate digest of all observations, discoveries, and inventions recorded in every branch of
medical science. The very extensive arrangements of the publishers are such as to  afford to the
editor complete materials for this purpose, as he not only regularly receives

    ALL  THE AMERICAN  MEDICAL AND  SCIENTIFIC  PERIODICALS,
but also twenty or thirty of the more important Journals issued in Great Britain and on Ihe Conti-
nent, thus enabling  him to present  in a convenient compass a thorough  and complete abstract ol
everything interesting or important to the physician occurring in any part of the civilized world.
  An  evidence of the success which has  attended these efforts may be found in the constant and
steady increase in  the subscription list, which renders it advisable for  gentlemen  desiring the
Journal, to make known their wishes at an early day, in order to secure a year's set with certainty,
the publishers having frequently been unable to supply copies when ordered late in the year.  To
their old subscribers, many of whom have been on their list for twenty or thirty years, the publish-
ers feel that no promises are necessary; but those who may desire for the first time to subscribe,
can rest assured that no exertion will be spared to maintain the Journal in the high position which
it has occupied for so long a period.
  By reference to the terms it will be seen that, in addition to this large amount of valuable and
practical information on every branch of medical science,  the subscriber, by paying in advance,
becomes entitled, without further charge, to

            THE  MEDICAL  NEWS AND LIBRARY,
a monthly  periodical of thirty-two large octavo pages.  Its "News Department" presents the
current information of the day, while the " Library Department" is devoted to presenting stand-
ard works  on various branches of medicine.   Within a few  years,  subscribers have thus received,
without expense, the following works which have passed through its columns:—
WATSON'S LECTURES ON THE PRACTICE OF PHYSIC.
BRODIE'S CLINICAL LECTURES ON  SURGERY.
TODD AND BOWMAN'S PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN.
  724 pages, with numerous wood-cuts, being all that has yet appeared in England.
WEST'S  LECTURES ON THE DISEASES OF INFANCY AND  CHILDHOOD.
MALGAIGNE'S OPERATIVE SURGERY, with wood-cuts.
SIMON'S  LECTURES ON GENERAL PATHOLOGY.
BENNETT ON PULMONARY TUBERCULOSIS, with wood-cuts,
WEST ON ULCERATION OF THE OS UTERI, and
BROWN  ON  THE SURGICAL DISEASES OF  FEMALES, with wood-cuts.
      While in the number for July, 1856, is commenced a new and highly important work,
        WEST'S LECTURES ON THE DISEASES  OF WOMEN.
                           Part I.—Diseases of the Uterus.
  The very favorable reception accorded by the profession  to  the valuable " Lectures on the
Diseases of Children," by the same author, which likewise appeared in this periodical, has in-
duced the  publishers to secure the present work for their subscribers, from advance sheets, supplied
by the  author.   The very high reputation of Dr. West, and  the unusual clinical advantages which
he has enjoyed, sufficiently indicate the practical value of a systematic work  from his pen on so
important  a subject.  The publishers, therefore, trust that its appearance in the " News" will afford
entire satisfaction to their numerous subscribers, who will thus receive it free of all expense.
  fgf For a more extended advertisement, see p. 32.
  It will thus be seen that for the small sum of FIVE DOLLARS, paid in advance, the subscriber
will obtain a Quarterly and a Monthly periodical,

            EMBRACING  ABOUT FIFTEEN HUNDRED  LARGE OCTAVO  PAGES,
mailed to any part of the United States, free of postage.
  These very favorable terms are now presented by the publishers with the view of removing all
difficulties and objections to a full and extended  circulation of the Medical  Journal to the office of
■every member of the profession throughout the United Slates.  The rapid extension of mail facili-
ties will  now place  the numbers before subscribers  with a certainty and dispatch not heretofore
attainable;  while by the system now  proposed,  every subscriber throughout the Union is placed
upon an equal footing, at the very reasonable price  of Five Dollars for two periodicals, without
further expense?
  Those subscribers who do not pay in advance will bear in mind that their subscription of Five
Dollars will entitle them to the Journal only, without the News, and that they will be at the expense
of their own postage on the receipt of each number.  The advantage of a remittance when order-
ing the Journal will thus  be apparent.
  As the Medical News and Library is in no case sent  without advance payment, its subscribers
will always receive  it free of postage.
  Remittances of subscriptions can be mailed at our risk, when a certificate  is taken from the Post-
master that the money is duly inclosed and forwarded.
                                   Address       BLANCHARD «fc  LEA,  Philadelphia. 
AND  SCIENTIFIC  PUBLICATIONS.
3
                              ALLEN  (J.  M ),  M. D.,
                  Professor of Anatomy in the Pennsylvania Medical College, See.
THE  PRACTICAL  ANATOMIST;  or,  The  Student's Guide in the Dissecting.
  ^00M^„ ^lth l£6 ^lustrations.  In one handsome royal 12mo. volume, of over 600 pages, lea-
  ther.  $2 25.   (Now Ready.)
  In the arrangement of this work, the author has endeavored to present a complete and thorough
course of dissections in a clearer and more available form for practical use, than  has as yet been
accomplished.  The chapters follow each other in the order in which dissections  are usually con-
ducted in this country, and as each region is taken up, every detail regarding it is fully described
and illustrated, so that the student is not interrupted in his labors, by the necessity of referring from
one portion of the volume to another.

                         ANALYTICAL  COMPENDIUM
OF MEDICAL SCIENCE, containing Anatomy, Physiology, Surgery, Midwifery,
  Chemistry, Materia Medica, Therapeutics,  and  Practice of Medicine.  By John Neill, M. D.,
  and  F. G.  Smith, M. D.   New and  enlarged edition, one thick volume royal 12mo. of over
  1000 pages, with 374 illustrations.  OP See Neill, p. 24.

                ABEL  (F. A.),  F.  C. S.  AND  C.  L.  BLOXAM.
HANDBOOK  OF CHEMISTRY, Theoretical, Practical, and Technical; with a
  Recommendatory Preface by Dr. Hofmann.  In one large octavo volume, extra cloth, of 662
  pages, with illustrations.  $3 25.
  It must be understood that this is a work fitted for | cessary, with such manipulatory details as rendered
                                              Faraday's ' Chemical Manipulations' so valuable at
the earnest student, who resolves to pursue for him-
self a steady search into the chemical mysteries of
creation.  For such a student the ' Handbook' will
prove an excellent guide,  since he will find in it,
not merely the approved modes of analytical investi-
gation, but most descriptions of the  apparatus ne-
the time of its publication.  Beyond this,  the im-
portance of the work is increased by the introduc-
tion of much of the technical chemistry of the manu-
factory.—Dr. Hofmann>$ Preface.
                         ASHWELL  (SAMUEL),  M.D.,
                  Obstetric Physician and Lecturer to Guv's Hospital, London.
A PRACTICAL TREATISE ON THE DISEASES PECULIAR TO WOMEN.
  Illustrated by Cases derived from Hospital and Private Practice. Third American, from the Third
  and revised London  edition.  In one octavo volume, extra cloth, of 528 pages.  (Lately Pub-
  lished.)  $3 00.
  The most useful practical work on the subject in
the English language. — Boston Med. and Surg.
Journal.
  The most able, and certainly the most standard
and practical, work on female diseases that we have
yet seen.—Medico-Chirurgical  Review.
  The young practitioner will find it invaluable,
V/hile those who have had most experience will yet
find something to learn, and much to commend, in a
book which shows so much patient observation,
practical skill, and sound sense.—British and Fo-
reign Med. Review.

  We commend it to our readers as the best practi-
cal  treatise on  the subject which has yet appeared.
—London Lancet.
                            ARNOTT (NEILL), M. D.
ELEMENTS  OF  PHYSICS;  or  Natural Philosophy,  General  and  Medical.
  Written for universal use, in  plain or non-technical language.  A new edition, by Isaac Hays,
  M. D.  Complete in one octavo volume, leather, of 484 pages, with about two hundred illustra-
  tions.  $2 50.                     ____________________

                           BENNETT (HENRY),  M.  D.
A PRACTICAL  TREATISE  ON  INFLAMMATION OF  THE  UTERUS,
  ITS  CERVIX AND  APPENDAGES,  and  on its connection with Uterine Disease.  Fourth
  American from the third and revised London edition.  To which is added (July, 1856), a Review
  of the Present State of Uterine Pathology.  In one neat octavo volume, extra cloth, of
  500 pages, with wood-cuts.  $2 00.
  The addition of the "Review" presents the most recent aspects of the questions discussed in
this well-known work, bringing it down  to the latest moment.
  This edition has been carefully revised and altered,   When, a few years back, the first edition  of the
and various additions have been made, which render  present work was published, the subject was one al-
it more complete and,  if possible, more worthy of  most entirely unknown to the obstetrical celebrities
the hi"h appreciation  in which it is  held by  the j of the day ; and even now we have reason to know
medica°l profession throughout the world.  A copy j that the bulk of  the profession are not fully alive to
should be in the possession of every physician.—| the importance and frequency of the disease of which
Charleston Med. Journal  and Review.            | it takes cognizance.  The presentedition is so much
                        .,  . ■   ,__„,(.;,,*, QO o I enlarged, altered, and improved, that it can scarcely
  We are firmly of opinion  that in proportion as a      °sl(Jered tlle sllme ^,)ck.J.Dr. Rankings Ac-
knowledge of uterine diseases becomes  more appre- j
ciated, this work will be proportionably established ,
as a text-book in the profession.—The Lancet.      i
                 Also, just ready,  by the same author, and for  sale separate,

A REVIEW OF THE PRESENT STATE OF UTERINE PATHOLOGY.
  1 small vol. 8vo.  50 cents, in  flexible  cloth.
  In this little work, which can be had  either  in connection with the  "Practical Treatise,"  or
.pnar«iP  the author presents his latest views with regard to the various doctrines which have re-
cenUv been brought forward on this interesting  question, under the following heads :-
r   ol  Preliminary.  II.  Sketch of Uterine Pathology.  III. Objections.  IV. The Leucorrhoea
  TAheory-the Syphilis  Theory-tbe  Ovarian Theory.  V. The Displacement Theory.  VI.

  Summary. 
4
BLANCHARD & LEA'S MEDICAL
                           BROWN  (ISAAC  BAKER),
                       Surgeon-Accoucheur to St. Mary's Hospital, &c.
ON SOME DISEASES OF  WOMEN ADMITTING OF SURGICAL TREAT-
  MENT.  With handsome illustrations.   One vol. 8vo., extra cloth.  (Now Ready.) $L 60.
  Mr. Brown has earned for himself a high reputa- | and merit the careful attention  of every sur^eon-
tion in the operative treatment of sundry diseases
and injuries to which females are peculiarly subject.
We can truly say of his work that it is an important
addition  to obstetrical literature.  The operative
suggestions and contrivances which  Mr. Brown de-
scribes, exhibit much practical sagacity  and  skill,
accoucheur.—Association Journal.

  We have no hesitation in recommending this book
to the careful attention of all surgeons who make
female complaints a part of their study and practice.
—Dublin Quarterly Journal.
                BENNETT (J.  HUGHES), M.D., F.  R. S. E.,
               Professor of Clinical Medicine in the University of Edinburgh, &c.
THE  PATHOLOGY AND  TREATMENT OF PULMONARY  TUBERCU-
  LOSIS, and on the Local Medication of Pharyngeal and Laryngeal  Diseases frequently mistaken
  for or associated with, Phthisis.   In one handsome octavo volume, extra cloth, with beautiful
  wood-cuts.   pp. 130.   (Lately Issued.)  f 1 25.
                       BUDD (GEORGE), M. D., F. R. S.,
                      Professor of Medicine in King's College, London.

ON DISEASES  OF  THE LIVER.   Second  American,  from  the second and
  enlarged London edition.   In one very handsome octavo volume, extra cloth, with  four beauti-
  fully colored plates, and numerous wood-cuts.   pp. 468.  $3  00.
  For many years, Dr.  Budd's work must be the I  the subject has been taken up by so able and experi-
authority of the great mass of British practitioners   enced a physician.—British and Foreign Medico-
on the hepatic diseases; and it is satisfactory that I  Chirurgieal Review.

                          by the same author.  (Now Ready.)

ON THE  ORGANIC  DISEASES  AND  FUNCTIONAL DISORDERS OF
  THE STOMACH.  In one neat octavo volume, extra cloth.   $1  50.  A new work, 1856.
  While special treatises have been multiplying upon almost all the different classes of diseases, there
has long been felt the want  of aii authoritative work  on  the disorders of the stomach, which con-
stitute, perhaps, a larger proportion of the daily practice of the physician than any other class of
maladies.  To supply this want has been the object of the  author, and his reputation  is an ample
guarantee of the value  of his labors.
  From the high position occupied by Dr. Budd as
a teacher, a writer, aud a practitioner, it is almost
needless to state that the present book may be con-
sulted with great advantage. It is written in an easy
style, the subjects are well arranged, and the practi-
cal precepts, both of diagnosis and treatment, denote
the character of a thoughtful and  experienced phy-
sician.—London Med. Times and Gazette, Dec. 1855.
                     BIRD (GOLDING), A. M., M. D.,  &c.
URINARY   DEPOSITS:   THEIR   DIAGNOSIS,   PATHOLOGY,  AND
  THERAPEUTICAL INDICATIONS.  A new and enlarged American, from the last improved
  London edition.  With over sixty illustrations.  In one royal 12mo. vol, extra cloth, pp. 372.  $ I 30.
  It can scarcely be necessary for us to sa^ anything
of the merits of this well-known Treatise, which so
admirably brings into practical application the re-
sults of those microscopical and chemical researches
regarding the physiology and pathology of the uri-
nary secretion, which have contributed so much to
the  increase of our diagnostic powers, and to the
extension and satisfactory employment of our thera-
peutic resources.  In the preparation of this new
edition of his work, it is obvious that Dr. Golding
Bird has spared no pains to render it a faithful repre-
sentation of the present state of scientific knowledge
on the subject it embraces. — The British and Foreign
Medico-Chirurgical Review.
BY THE SAME AUTHOR.
ELEMENTS OF NATURAL  PHILOSOPHY;  being  an  Experimental Intro-
  duction to the Physical Sciences.  Illustrated with nearly four hundred wood-cuts.  From the
  third London edition.  In one neat volume, royal 12mo., extra cloth,  pp.402.  $125.
BILLING'S  PRINCIPLES  OF  MEDICINE.—
  Second American, from the Fifth and Improved
  London edition.  In one handsome octavo volume,
  extra cloth. 250 pages.  $125.
BLAKISTON'S PRACTICAL OBSERVATIONS
  ON  CERTAIN  DISEASES OF THE  CHLST,
  and on the Principles of Auscultation. In one vol.,
  cloth, 8v<>  pp.384. $125.
BURROWS ON DISORDERS OF THE CERE-
  URAL CIRCULATION,  and on the  Connection
  between the Affections of  the Brain and Diseases
  of the Heart.  In one 8vo. vol., extra  cloth, with
  colored plates,  pp. 216. SI 25.
BEALE ON  THE LAWS  OF HEALTH IN RE-
  LATION TO MIND AND BODY.  A Series of
  Letters from an old  Practitioner to a Patient.  In
  one volume, royal 12mo , extra cloth,  pp. 296.
  60 cents.
BUSHNAN'S PHYSIOLOGY OF ANIMAL AND
  VEGETABLE LIFE; a Popular Treatise on the
  Functions and Phenomena of Organic Lite. In
  one handsome royal J2mo. volume, extra cloth,
  with over 100 illustrations,  pp.234.  80 cents.

BUCKLER ON THE ETIOLOGY, PATHOLOGY,
  AND TREATMENT  OF  FIBRO-BRONCHl-
  TIS AND  RHEUMATIC  PNEUMONIA.  In
  one 8vo. volume, extra cloth,  pp. 150.  $1 25.

BLOOD AND URINE (MANUALS ON).   BY
  JOHN  WILLIAM  GRIFFITH,  G. OWEN
  REESE, AND  ALFRED MARKWICK.   One
  thick volume,  royal  12mo.,  extra cloth,  with
  plates, pp. 460.  $1 25.

BRODIE'S CLINICAL LECTURES ON SUR-
  GERY.  1 vol. 8vo., cloth.  350 pp.  $125. 
AND  SCIENTIFIC  PUBLICATIONS.
5
                         BARLOW (GEORGE H.),  M.D.
                          Physician to Guy's Hospital, London, &c.

A MANUAL  OF THE PRACTICE OF MEDICINE.  With Additions by D.
  F. Condie, M. D., author of" A Practical Treatise on Diseases of Children," <fec.  In one hand-
  some octavo volume, leather, of over tjOO pages.   (A new work, just ready, 1856.)  $2 75.
  The position of the author as physician to Guy's Hospital and other large public institutions, is
a sufficient guarantee of the extent and value of the experience which  is here systematically re-
corded and condensed.  His aim throughout has been to produce a practical work, on which the
student can rely as a guide, and to which the practitioner can refer with confidence.  The additions
by the editor comprise  chapters on Cerebro-spinal Meningitis, Cholera Infantum, and Yellow Fever,
besides numerous notes wherever the diseases or practice of this country seemed to render them
necessary or desirable.
  We most emphatically commend it to the attention
of the profession, as deserving their confidence—a
depository of practical knowledge, from which they
may draw with great benefit.—Cincinnati Med. Ob-
server, Mar. 1856.
  The student has long been in want of a good ele-
mentary work on the Practice of Medicine.  In Dr.
Barlow's Manual that want is supplied; and we
have no question that it will at once be installed
as the favorite text-book in all Medical Schools.—
Medical Times and Gazette.
  We recommend Dr. Barlow's Manual in the warm-
est manner as a most valuable vade-mecum. We
have had frequent occasion to consult it, and have
found it clear, concise, practical, and sound.  It is
eminently a practical work, containing all that is
essential, and  avoiding useless theoretical discus-
sion.  The work supplies what has been for some
time wantingj a manual of practice based upon mo-
dern discoveries in pathology and rational views of
treatment of disease.  It is especially intended for
the use of students and junior practitioners, but it
will be found hardly less useful to the experienced
physician.  The American editor has added to the
work three chapters—on Cholera Infantum, Yellow
Fever, and Cerebro-spinal Meningitis.  These addi-
tions,  the two first of which are indispensable to a
work on practice destined for the profession  in this
country, are executed with  great judgment  and fi-
delity, by Dr. Condie, who has also succeeded hap-
pily in imitating the conciseness  and clearness of
style which are such  agreeable characteristics of
the original book.—Boston Med. and Surg. Journal,
Feb. 1856.
                           BARTLETT (ELISHA),  M. D.

THE  HISTORY,  DIAGNOSIS,  AND TREATMENT  OF  THE  FEVERS
  OF THE UNITED STATES.   A new and revised edition.  By Alonzo Clark, M. D., Prof.
  of Pathology and Practical Medicine in the N. Y. College of Physicians and  Surgeons, &c.  In
  one octavo volume, of six hundred pages, extra cloth.  (Now Ready.)  Price $3 00.
  The position which this work has obtained as one of our medical classics, renders unnecessary
any remark further than to say that the editor, in executing the  task assigned  to him by the late
author, has endeavored to render the work a faithful exposition of the subject in its most advanced
condition.  To effect this, a considerable amount of matter has been introduced, but by a slight
enlargement of the  page it has been accommodated without unduly increasing the bulk  of the
volume.  The reputation of the editor as an accurate observer and philosophical writer is sufficient
guarantee that, in his hands, the work will fully maintain its former character.
  The masterly and elegant treatise by Dr. Bartlett
is invaluable to the American student and practi-
tioner.__Dr. Holmes's Report to the Nat. Med. Asso-
ciation.
  We regard it, from the examination we have made
of it, the best work on fevers extant in our language,
and as such cordially recommend it to the medical
public.—St. Louis Medical and Surgical Journal.
  Take it altogether, it is the most complete history
of our fevers which has yet been  published, and
every practitioner should avail himself of its con-
tents.— The Western Lancet.
                           BOWMAN (JOHN  E.), M.D.
PRACTICAL  HANDBOOK  OF  MEDICAL   CHEMISTRY.   Second Ame-
  rican from the third and revised English Edition.  In one neat volume, royal 12mo., extra cloth,
  with numerous illustrations,  pp. 288.  (Now Ready, 1856.)  $1 25.
  Pre<entin°- in a condensed and convenient form, at a very low price, the applications of Chemistry
to the^nractical purposes of  Clinical Medicine, this work  supplies a  want which has long been
elt bvthe physician   The numerous editions which have been called for both in England and this
country, sufficiently attest the success with which the author has carried out his plan.

                           BY THE SAME author.  (Now Ready.)

INTRODUCTION  TO  PRACTICAL  CHEMISTRY,  INCLUDING  ANA-
  T YSIS   Second American, from  the second and revised  London edition.  With numerous illus-
  trations.  In one neat vol., royal 12mo., extra cloth,  pp. 350.  U 25.


                           CURLING  (T.  B.>, F. R.S.,
             Sureeon to the  London Hospital, President of the Hunterian Society, &c.

A PR\CTICAL TREATISE  ON  DISEASES  OF  THE  TESTIS, SPERMA-
  rpjyT pryRD  AND SCROTUM.   Second American, from the second and enlarged English edi-
  11U OUJ^ handsome octavo volume, extra cloth, with numerous illustrations, pp. 420.  (Now

  Ready 1856.)  $2 00.
  t «fc,TrPvi«ed English edition, of which this is a reprint, the author, for want of space, omitted
u i  VmiAl Introduction.  By a more condensed style of printing, room  has been found m tha
the Anatomy       {n this important portion without rendering the work inconveniently large.
r^esent volume       ^ former American editor have also been incorporated, and a number of new
Some oi tne no. .       w .^ thege jmprovementS) ami tne thorough revision which it has enjoyed
illustrations w™™1^^ it w;u be found fully worthy to retain the authoritative position which
If hS acquired with regard to this class of affections. 
6
BLANCHARD 6c LEA'S  MEDICAL
             CARPENTER (WILLIAM  B.), M.  D., F. R. S.,  &c,
           Examiner in Physiology and Comparative Anatomy in the University of London.

PRINCIPLES OF HUMAN  PHYSIOLOGY;  with  their  chief applications  to
  Psychology, Pathology, Therapeutics, Hygiene, and Forensic Medicine. A new American, from
  the last and revised London edition.  With nearly three hundred illustrations.  Edited, with addi-
  tions, by Francis Gurney Smith, M. D., Professor of the  Institutes of Medicine in the  Pennsyl-
  vania Medical College, &c. In one very large and beautiful octavo volume, of about nine hundred
  large pages, handsomely printed and strongly bound in leather, with raised bands.   (Just Issued,
  1856.)  $4  2b.
  In the preparation of this new edition, the author has spared no labor to render  it, as heretofore,
a complete and lucid exposition of the  most  advanced condition  of its important subject.  The
amount of the additions required to effect this object thoroughly, joined to the former large  size of
the volume, presenting objections arising from the unwieldy  bulk of the work, he has omitted all
those portions  not  bearing  directly upon Human Physiology, designing to incorporate them in
his forthcoming Treatise on General Physiology.  As a full and  accurate text-book on  the Phy-
siology of Man, the work in  its present condition therefore presents even  greater claims upon
the student and physician  than  those  which have heretofore won  for it the very wide and distin-
guished favor which it has so long enjoyed.  The additions of Prof. Smith will be found  to supply
whatever may  have been  wanting to the American  student,  while  the introduction of many new
illustrations,  and the most careful  mechanical execution, render the volume one of the  most  at-
tractive as yet issued.
  For upwards of thirteen years Dr. Carpenter's
work has been  considered by the profession gene-
rally, both in this country and England, as the most
valuable compendium on the subject of physiology
in our language. This distinction it owes to the high
attainments and unwearied industry of its accom-
plished author.  The present edition (which, like the
last American one, was prepared by the author him-
self), is the result of such extensive revision, that it
may almost be considered  a new work.  We need
hardly say, in concluding this brief notice, that while
the work is indispensable to every student of medi-
cine in this country, it will amply repay the  practi-
tioner for its perusal by  the interest and value of its
contents.—Boston Med.  and Surg. Journal.

  This is a standard work—the text-book used by all
medical students who read the  English language.
It has  passed  through several editions in order to
keep pace with the rapidly growing science of Phy-
siology.  Nothing need  be said in its praise, for  its
merits  are universally known ; we have nothing to
say of its defects, for they only appear where the
science of which it treats  is incomplete.—Western
Lancet.
  The most complete exposition of physiology which
any language  can at present give.—Brit, and For.
Med.-Chirurg. Review.

  The greatest, the most reliable, and the best book
on the subject  which we know of in the English
language.—Stethoscope.
  To eulogize this great work would be superfluous
We should observe, however, that in this edition
the author has remodelled a large portion  of the
former, and the editor has added much matter of in-
terest, especially in the form of illustrations.  We
may confidently recommend if. as the most complete
work on Human Physiology  in  our language.—
Southern Med. and Surg. Journal, December, 1855
  The most  complete work on the science  in our
language.—Am. Med. Journal.
  The most complete work now extant in our lan-
guage.—N. O. Med. Register.
  The best text-book in the language on this ex-
tensive subject.—London Med. Times.
  A complete cyclopaedia of this branch of science.
—N. Y. Med. Times.
  The profession of this country, and perhaps also
of Europe, have anxiously and for some time awaited
the announcement of this new edition of Carpenter's
Human  Physiology.  His former editions have for
many years been almost the only text-book on Phy-
siology in all our medical schools, and its circula-
tion among the profession has  been unsurpassed by
any work in any department of medical science.
  It is quite  unnecessary for us to speak of this
work as its merits would justify.  The  mere an-
nouncement of its appearance will afford the highest
pleasure to every student of Physiology, while its
perusal  will  be  of infinite  service in advancing
physiological science.—Ohio Med. and Surg. Journ.
                          BY THE same author.  (Lately Issued.)

PRINCIPLES OF COMPARATIVE  PHYSIOLOGY.   New  American, from
  the Fourth and Revised London edition.  In one large and handsome octavo volume, with over
  three hundred beautiful illustrations,  pp. 752.   Extra cloth, $4 80;  leather, raised bands, $5 25.
  The delay which has existed in the appearance of this work has been caused by the very thorough
revision and remodelling which it has undergone at the hands of the author, and the large number
of new illustrations which have been prepared for it.  It will, therefore, be found almost a new
work, and fully up to the day in every department of the  subject, rendering it  a reliable text-book
for all students engaged in this branch of science.   Every effort  has been made to render its typo-
graphical finish and mechanical execution worthy of its exalted reputation, and creditable to the
mechanical arts of this country.
  This book should not only be read but thoroughly
studied by every member of the profession.  None
are too wise or old, to be benefited thereby.  But
especially to the younger class would we cordially
commend it as best fitted of any work in  the English
language to qualify them for the reception and com-
prehension of those truths which are daily being de-
veloped in physiology.—Medical Counsellor.
  Without pretending to it, it is an encyclopedia of
the subject, accurate and complete in all respects—
a truthful reflection of the advanced state at which
the science  has  now  arrived.—Dublin Quarterly
Journal of Medical Science.
  A truly magnificent work—in itself a perfect phy-
siological stady.—Ranking's Abstract.
  This work stands without its fellow.  It is one
few men in Europe could have undertaken; t is one
no man, we believe, could have brought to so suc-
cessful an issue as Dr. Carpenter,  ft required for
its production a physiologist at once deeply read in
the labors of others, capable of taking  a general,
critical, and unprejudiced view of those labors, and
of combining the varied, heterogeneous materials at
his disposal, so as to form an  harmonious whole.
We feel that this abstract can give the reader a very
imperfect idea of the fulness of this work, and no
idea of its unity, of the admirable manner in which
material has been brought, from the most various
sources, to conduce to its completeness, of the lucid-
ity of the reasoning it contains, or of the clearness
of language in which the whole is clothed.  Not the
profession only, but the scientific world at large,
must feel deeply indebted to Dr. Carpenter for this
great work.  It must,  indeed, add largely even to
his high reputation.—Medical Times. 
AND  SCIENTIFIC  PUBLICATIONS.
7
                CARPENTER (WILLIAM B.),  M.  D., F. R. S.,
          Examiner in Physiology and Comparative Anatomy in the University of London.
                                  (Now Ready, 1856.)

THE  MICROSCOPE AND ITS  REVELATIONS.   With an  Appendix con-
  taining the Applications of the Microscope to Clinical Medicine, &c.   By F. G. Smith, M. D
  Illustrated by lour hundred and thirty-four beautiful engravings on wood. In one large and verv
  handsome octavo volume, of 724 pages, extra cloth, $4 00 ; leather, $4  50.
  Dr. Carpenter's position as a microscopist and physiologist, and his great experience as a teacher,
eminently qualify him to produce what has long been wanted—a good text-book on the  practical
use of the microscope.  In the present volume  his object  has been, as stated in  his Preface, " to
combine, within a moderate compass, that information with regard lo the use  of his ' tools,' which
is most essential to  the working microscopist, with such an account of the objects best fitted for
his study, as might  qualify him to comprehend what he observes, and might  thus prepare him to
benefit science, whilst expanding and refreshing his own mind "   That he has succeeded in accom-
plishing this, no one acquainted with his previous labors can doubt.
  The great importance of the microscope as a means of diagnosis, and the number of microsco-
pies who are also physicians, have induced the American publishers, with the author's approval, to
add an Appendix, carefully prepared by Professor Smith, on the applications  of the instrument to
clinical medicine, together with an  account of American Microscopes, their modifications  and
accessories.  This  portion of the work is illustrated with nearly one hundred wood-cuts, and, it is
hoped, will adapt the volume more particularly to the use of the American student.
  Every care has been taken in the mechanical execution  of the work, which is confidently pre-
 sented as in no respect inferior to the choicest productions of the London press.
  The mode in which the author has executed his intentions may be gathered from the following
 condensed synopsis of the
                                      CONTENTS.
 Introduction—History of the Microscope.   Chap.  I.  Optical  Principles of the Microscope.
  Chap. II.  Construction of the Microscope.  Chap. III.  Accessory Apparatus.  Chap.  IV.
  Management of the  Microscope   Chap. V.  Preparation, Mounting, and Collection of Objects.
  Chap. VI.  Microscopic Forms of Vegetable Life—Protophytes.  Chap. VII. Higher Cryptoga-
  mia.  Chap. VIII. Phanerogamic Plants.  Chap. IX. Microscopic Forms of Animal Life—Pro-
  tozoa—Animalcules.  Chap. X. Foraminifera, Polycystina, and Sponges. Chap. XI. Zoophytes.
  Chap. XII. Echinodermata.  Chap. XIII.  Polyzoa and Compound  Tunicata.  Chap. XIV.
  Molluscous Animals Generally.  Chap. XV.  Annulosa.  Chap. XVI. Crustacea.  Chap. XVII.
  Insects and  Arachnida.  Chap.  XVIII. Vertebrated Animals.  Chap. XIX. Applications of the
   Microscope to Geology. Chap. XX. Inorganic or Mineral Kingdom—Polarization. Appendix.
   Microscope as a means of Diagnosis—Injections—Microscopes of American Manufacture.
  Those who are acquainted with Dr. Carpenter's
previous writings on Animal and Vegetable Physio-
logy, willfully understand how vast a store of know-
ledge he is able to bring to bear upon so comprehen-
sive a subject as the revelations of the microscope j
and even those who have no previous acquaintance
with  the construction or uses of this  instrument,
will find abundance of information conveyed in clear
and simple language.—Med. Times and Gazette.
tise on Physiology, cannot do better than to possess
themselves of the manual of Dr. Carpenter.—Medical
Examiner.
  The best and most complete expose' of modern
Physiology, in one volume, extant in the English
language.—St. Louis Medical Journal.
                                 BY THE SAME AUTHOR.

ELEMENTS (OR MANUAL) OF  PHYSIOLOGY, INCLUDING PHYSIO-
  LOGICAL ANATOMY.  Second American, from a new and revised London edition.  With
  one hundred  and ninety illustrations.  In one very handsome octavo volume, leather,  pp. 566.
  $3 00.
  In publishing the first edition of this work, its title was altered from that of the London volume,
by the substitution of the word " Elements" for that of " Manual," and with the author's sanction
the title of " Elements" is still retained as being more expressive of the scope of the treatise.
  To say that it is the best manual of Physiology    Thosewho have occasion for an elementary trea-
now before the public, would not do sufficient justice
to the author.—Buffalo Medical Journal.
  In his former works it would seem that he had
exhausted the subjectof Physiology. In the present,
he gives the essence, as it were, of the whole.—N. Y.
Journal of Medicine.
                           BY THE SAME author.  (Prepa. ing.)

PRINCIPLES  OF  GENERAL  PHYSIOLOGY,   -NCLUDING  ORGANIC
  CHEMISTRY AND HISTOLOGY.  With a General Sketch of the Vegetable and Animal
  Kingdom.  In one large and very handsome octavo volume, with several hundred illustrations.
  The subject of general physiology having been omitted in the last editions oi the author's " Com-
parative Physiology" and "Human Physiology," he has undertaken to prepare a volume  which
shall present it more thoroughly and fully than has yet been attempted, and which may be regarded
as an introduction to his other works.
                                 BY THE  SAME AUTHOR.

A PRIZE ESSAY ON THE USE OF ALCOHOLIC LIQUORS  IN HEALTH
  AND DISEASE.   New edition, with a Preface by D. F. Condie, M. D., and explanations of
  scientific words.  In one neat 12mo. volume, extra cloth, pp. 178.  (Just Issued.)  50 cents.


                             CHELIUS  (J. M.), M. D.,
                    Professor of Surgery in the University of Heidelberg, &c.

A  SYSTEM OF SURGERY.   Translated from  the German,  and  accompanied
    th additional Notes and References, by John F. South.  Complete in three very large  octavo
    1 mes  of nearly 2200 pages, strongly bound, with raised bands and double titles.  $10 00. 
8
BLANCHARD & LEA'S MEDICAL
                           CONDIE (D. F.),  M. D., &c.

A PRACTICAL TREATISE  ON THE DISEASES OF CHILDREN.  Fourth
  edition, revised and augmented.  In one large volume, 8vo., leather, of nearly 750 pages. $3 00.

                              From the Author's Preface.
  The demand for  another edition has afforded  the author an opportunity of again subjecting the
entire treatise to a careful revision, and of incorporating in it every important observation recorded
since the appearance of the last edition, in reference to the pathology and therapeutics of the several
diseases of which it treats.
  In the  preparation of the present edition, as in those which have preceded, while the author has
appropriated to his use  every important fact that he has found recorded in the works of others,
having a direct bearing upon either of the subjects of which he treats, and the numerous valuable
observations—pathological as well as practical—dispersed  throughout the pages of the  medical
journals of Europe and America, he has, nevertheless, relied chiefly upon his own observations and
experience, acquired during a long and somewhat extensive practice, and under circumstances pe-
culiarly well adapted for the clinical study of the diseases of early life.
  Every species of hypothetical reasoning has, as much as possible, been avoided. The author has
endeavored throughout the work to confine himself to a simple statement of well-ascertained patho-
logical facts, and plain therapeutical  directions—his  chief desire being to render it what its title
imports it to be, a practical treatise on the diseases of children.
  Dr. Condie's scholarship, acumen? industry, and
practical sense are manifested in this, as in all his
numerous contributions to science.—Dr. Holmes's
Report to the American Medical Association.
  Taken as a whole, in our judgment, Dr. Condie's
Treatise  is the one from  the perusal of which the
practitioner in this country will rise with the great-
est  satisfaction.—Western Journal of Medicine and
Surgery.
  One of  the best works upon the Diseases of Chil-
dren in the English language.—Western Lancet.
  Perhaps the most full and complete work now be-
fore the profession of the United States; indeed, we
may say in the English language. It is vastly supe-
rior to most of its predecessors.—Transylvania Med.
Journal.
  We feel assured from actual experience that no
physician's library can be complete without a copy
of this work.—N. Y. Journal of Medicine.

  A veritable pediatric encyclopaedia, and an honor
to American medical literature.—Ohio Medical and
Surgical Journal.

  We feel persuaded that the American medical pro-
fession will soon regard it not only as a very good,
but as the very best "Practical Treatise on  the
Diseases of Children."—American Medical Journal,

  We pronounced the first edition to be the best
work on  the diseases of children  in the  English
language, and,  notwithstanding all that has oeen
published, we still regard it in that light.—Medical
Examiner.
            CHRISTISON  (ROBERT), M. D., V. P.  R. S. E.,  &c.

A DISPENSATORY; or,  Commentary on the  Pharmacopoeias of Great ^Britain
  and the United States; comprising the Natural History, Description, Chemistry, Pharmacy, Ac-
  tions, Uses, and Doses of the Articles of the Materia Medica.   Second edition, revised and im-
  proved, with a Supplement containing the most important New Remedies. With copious Addi-
  tions, and two hundred and thirteen large wood-engravings.   By R. Eglesfeld Griffith, M. D.
  In one very large and handsome octavo volume, leather, raised bands, of over 1000 pages. $3 50.
  It  is not needful that we should compare  it with  this branch of knowledge which the student has a
the other pharmacopoeias extant, which enjoy and
merit the confidence of the profession : it is enough
to say that it appears to us as perfect as a Dispensa-
tory, in the present state of pharmaceutical science,
could be made.  If it omits any details pertaining to
right to expect in such a work, we confess the omis-
sion has escaped our scrutiny. We cordially recom-
mend this work to such of our readers as are in need
of a Dispensatory.  They cannot make choice of a
better.—Western journ. of Medicine and Surgery.
                        COOPER (BRANSBY B.), F. R. S.

LECTURES ON  THE  PRINCIPLES  AND  PRACTICE  OF  SURGERY.
  In one very large octavo volume, extra cloth, of 750 pages. $3 00.
COOPER  ON DISLOCATIONS AND  FRAC-
  TURES OF THE JOINTS —Edited by Bransby
  B.  Cooper, F. R. S., &c. With additional Ob-
  servations by Prof. J. C. Warken.  A new Ame-
  rican edition.  In one  handsome octavo volume,
  extra cloth, of about 500 pages, with numerous
  illustrations on wood.  $3 25.
COOPER ON THE ANATOMY AND TREAT-
  MENT OF ABDOMINAL HERN 1A.  One large
  volume, imperial 8vo., extra cloth, with over 130
  lithographic figures.  $2 50.
COOPER ON THE ANATOMY AND DISEASES
  OF THE BREAST, with twenty-five Miscellane-
  ous and Surgical Papers.  One large volume, im-
  perial 8vo., extra cloth, with 252 figures, on 36
  plates.  $2 50.
COOPER  ON THE  STRUCTURE AND DIS-
  EASES  OF  THE  TESTIS,  AND  ON THE
  THYMUS GLAND.  One vol. imperial 8vo., ex-
  tra cloth, with 177 figures on 29 plates.  $2 00.
COPLAND ON  THR CAUSES, NATURE, AND
  TREATMENT OF PALSY AND APOPLEXY.
  In one volume, royal 12mo., extra cloth, pp. 326.
  80 cents.
CLYMER ON FEVERS; THEIR DIAGNOSIS,
  PATHOLOGY, AND TREATMENT   In one
  octavo volume, leather, of 600 pages.  $1  50.
COLOMBAT DE L'ISERE ON THE DISEASES
  OF FEMALES,  and on the special Hygiene of
  their Sex. Translated, with many Notes and Ad-
  ditions, by C.  D. Meigs, M. D.  Second edition,
  revised and improved.  In one  large volume, oc-
  tavo, leather, with numerous wood-cuts. pp. 720.
  $3 50.
                           CARSON  (JOSEPH),  M. D.,
           Professor of Materia Medica and Pharmacy in the University of Pennsylvania.
SYNOPSIS OF THE COURSE  OF  LECTURES ON MATERIA  MEDICA
  AND PHARMACY, delivered in the  University of Pennsylvania.  Second and  revised edi-
  tion.  In one very neat octavo volume, extra cloth, of 208 pages.  (Now Ready.)  $1 50. 
AND  SCIENTIFIC  PUBLICATIONS.
9
               CHURCHILL (FLEETWOOD), M. D., M. R. I. A.

ON THE  THEORY AND PRACTICE OF  MIDWIFERY.  A new American,
  from the last and improved English edition.   Edited, with Notes and Additions, by D. Francis
  Condie, M. D., author of a "Practical Treatise on the Diseases of Children," &c.  With 139
  illustrations.  In one very handsome octavo volume, leather,  pp.510.  $3 00.
  To bestow praise on a book that has received such
marked approbation would be superfluous. We need
only say, therefore,  that if the first edition was
thought worthy  of a favorable reception  by the
medical public, we can confidently affirm that this
will be found much  more  so.  The lecturer, the
practitioner, and the student, may all have recourse
to its pages, and derive from their perusal much in-
terest and instruction  in everything relating to theo-
retical and practical midwifery.—Dublin Quarterly
Journal of Medical Science.

  A work of very great merit, and  such as we can
confidently recommend to the study of every obste-
tric practitioner.—London Medical Gazette.

  This is certainly the most perfect system extant.
It is the best  adapted for  the purposes of  a text-
book, and that which he whose  necessities confine
him to one book, should select in preference to all
others.—Southern Medical and Surgical Journal.

  The most popular work on midwifery ever issued
from the American press.—Charleston Med. Journal.

  Were we reduced to the necessity of having but
one work on midwifery, and permitted  to choose,
we would unhesitatingly take Churchill.—Western
Med. and Surg. Journal.
  It is impossible to conceive  a more useful and
elegant manual  than Dr.  Churchill's Practice  of
Midwifery.—Provincial Medical Journal.

  Certainly, in our opinion, the very best work on
the subject which exists.—N. Y. Annalist.
  No work holds a higher position, or is more de-
serving of being placed  in the hands of the tyro,
the advanced student, or  the practitioner.—Medical
Examiner.

  Previous editions, under the editorial supervision
of Prof R.  M. Huston,  have been received with
marked favor,  and they  deserved it; but this, re-
printed from a very late Dublin edition, carefully
revised and brought up by the author to the present
time, does present  an unusually accurate and able
exposition of every important particular embraced
in the department of midwifery.  * * The clearness,
directness, and  precision of its  teachings, together
with the great amount of statistical research which
its text exhibits, have served to place it already in
the foremost rank of works in this department of re-
medial science.—N. O. Med. and Surg. Journal.

  In our opinion, it forms one of the best if not the
very best text-book and epitome of obstetric science
which  we at present possess in the English lan-
guage.—Monthly Journal of Medical Science.

  The clearness and precision of style in which it is
written, and the great amount of statistical research
which it contains, have served to place it in the first
rank of works in this department of medical science.
— N. Y. Journal of Medicine.

  Few treatises will be  found  better adapted as a
text-book for the  student, or as a manual for the
frequent consultation of  the young practitioner.—
American Medical Journal.
                         by  the same author.   (Now Ready, 1856.)

ON THE  DISEASES  OF  INFANTS  AND  CHILDREN.   Second American
  Edition, revised and enlarged by the author.  Edited, with Notes, by W. V. Keating, M. D.  In
  one large and handsome volume, extra cloth, of over 700 pages.  $3 00, or in leather, $3 25.
  In preparing this work a second time for  the  American profession, the author has  spared  no
labor in o-iving it a very thorough revision, introducing several new chapters, and rewriting others,
while everv portion of the volume has been subjected to a severe scrutiny.  The efforts of the
im^ni^n vAiuir hnvp been directed to suDnlvina- such  information relative to matters peculiar
fore  be safely pronounced one ot the most complete worKs on me suDjeci aa-ewiuic iu »«= ^">-
rican Profession.  By an alteration in the size of the  page, these very extensive additions have
been accommodated without unduly increasing the size of the work.
  A  few notices of the former edition are subjoined :—
  We regard this volume as possessing more claims
to completeness than any other  of  the  kind  with
which we are acquainted.  Most cordially and ear-
nsstly, therefore, do we commend it to our profession-
al brethren, and we feel assured  that the stamp of
their approbation will in due time be impressed upon
it.  After an attentive perusal  of its contents, we
hesitate not to say,  that it is one of the most com-
prehensive ever written upon the diseases of.chil-
dren, and that, for copiousnessof reference, extent of
research, and  perspicuity of detail, it is scarcely to
be equalled,  and  not to be excelled, in any lan-
guage.— Dublin Quarterly Journal.

  After this meagre, and we  know, very imperfect
notice of Dr.  Churchill's work, we shall conclude
by sayIL, that it is one that cannot fail from its co-
oiousnesf extensive research, and general accuracy,
Te~ ill higher  the reputation. «rf th<, autho.: «,
this countrv.  The American reader will be.narticu
arlv Pleased to find that Dr. Churchil  has done full
 ustLe throughout his work to the various American
justice mrougi            Tn   names of Dewees,
^kT8 Pnndie -ind Stewart, occur on nearly every
Eberle.'„?these authors £e constantly referred toby
page, and these autnors *         praise, and with

l£ mXbeUSrte*^ *^«- **«*■"■
  The present volume will sustain the reputation
acquired  by the author from his previous works.
The reader will find in it full and judicious direc-
tions for  the management of  infants at birth, and a
compendious, but clear account  of the diseases to
which children are  liable, and the most successful
mode of treating them.  We must not close this no-
tice without calling attention to the author's style,
which is  perspicuous and polished to a degree, we
regret to say, not generally characteristic of medical
works.  We recommend the work of Dr. Churchill
most cordially, both to students and practitioners,
as a valuable and reliable guide  in the treatment of
the diseases of children.—Am. Journ. of the Med.
Sciences.

  We know of no work on this department of Prac
tical Medicine which presents so candid and unpre-
judiced a statement  or  posting  up of our actual
knowledge as this.—N. Y. Journal of Medicine.

  Its claims to merit both as a scientific and practi-
cal work, are of the highest order.  Whilst we
would not elevate it above every other treatise on
the same subject, we certainly believe that very few
are equal to it, and none superior.—Southern Med.
and Surgical Journal.
BY THE SAME AUTHOR.
t^avs ON  THE PUERPERAL  FEVER, AND  OTHER  DISEASES  PE-
    ttt t a w TO WOMEN   Selected from the writingsof British Authors previous to the close of
  the Eighteenth Century.  In one neat octavo volume, extra cloth, of about 450 pages.  '
$2 50. 
10
BLANCHARD  & LEA'S  MEDICAL
           CHURCHILL (FLEETWOOD),  M. D., M. R. I. A.,  &c.

ON THE  DISEASES OF WOMEN;  including  those of Pregnancy and  Child-
  bed.  A new American edition, revised by the Author.  With Notes and Additions, by D Fran-
  cis Condie, M. D., author ot "A Practical Treatise on the Diseases of Children."  With nume-
  rous illustrations.  In one large and handsome octavo volume.  (Nearly Ready.)
  This  edition of Dr.  Churchill's very popular treatise  may  almost be termed a new work, so
thoroughly has he revised  it in every portion.   It will  be found greatly enlarged, and thoroughly
brought up to the most recent condition of the subject, while the very handsome series of illustra-
tions introduced, representing such pathological conditions as can be accurately portrayed, present
a novel feature, and afford valuable assistance  to  the young practitioner.  Such additions as ap-
peared  desirable for the American student have  been  made  by the  editor, Dr. Condie, while a
marked improvement in the mechanical execution keeps pace with the advance in all other respects
which the volume has  undergone.
A few notices of the former edition are subjoined :—
  We now regretfully take leave of Dr. Churchill's
book.  Had our typographical limits permitted, we
should gladly have borrowed more from its richly
stored pages.  In conclusion,  we heartily recom-
mend it to the profession, and would at the same
time express our firm conviction that itwill not only
add to the reputation of its author, but will prove a
work of great and extensive  utility to obstetric
practitioners.—Dublin Medical Press.

  Former editions of this work  have been noticed in
previous numbers of the Journal.  The sentiments of
high commendation expressed in those notices, have
only to be repeated in this; not from the fact that
the profession at  large are not aware of the high
merits which this work really possesses, but from a
desire to see the  principles  and doctrines therein
contained more generally recognized, and more uni-
versally carried out in practice.—N. Y. Journal of
Medicine.

  We know of no author who deserves that appro-
bation, on " the diseases  of females," to the same
extent that  Dr. Churchill does.  His, indeed, is the
only thorough treatise we know of on the subject;
and it may be commended to practitioners and stu-
dents as a masterpiece  in  its particular department.
The former editions of this  work have been com-
mended strongly in this journal, and they have won
their way to an extended,  and a well-deserved popu-
larity.  This fifth edition, before us. is well calcu-
lated to maintain Dr. Churchill's  high reputation.
It was  revised and enlarged by the author, for  his
American publishers, and it seems to us that there is
scarcely any species of desirable information on its
subjects that may not be found in this work.—Tht
Western Journal of Medicine and Surgery.

  We are gratified  to announce a  new and revised
edition of Dr. Churchill's valuable work on the dis-
eases of females   We have ever regarded it as one
of the  very  best works on the subjects embraced
within  its scope, in the English lansruage;  and  the
present edition, enlarged and revised by the author,
renders it still more entitled to the confidence of the
profession.   The valuable notes  of Prof.  Huston
have been  retained, and contribute, in no small  de-
gree, to enhance the value of the work.  It is a
source  of congratulation  that the publishers have
permitted  the author to be, in  this instance,  his
own editor,  thus securing all the revision which
an author alone is capable of making.—The Western
Lancet.

  Asa comprehensive  manual for students, or a
work of reference for practitioners, we only  speak
with common justice when we say thnt it surpasses
any other that has ever issued  on  the same sub-
ject from the British press.—The Dublin Quarterly
Journal.
                              DICKSON  (S.  H.),  M. D.,
       Professor of Institutes and Practice of Medicine in the Medical College of South Carolina.

ELEMENTS  OF MEDICINE;   a Compendious  View of  Pathology  and  Thera-
  peutics, or the History and  Treatment of Diseases.  In one large and handsome octavo volume,
  of 750 pages, leather   (Now Ready.)  $3 75.
  As an American text-book on the Practice of Medicine for the student, and  as a condensed work
of reference for the practitioner, this volume will have strong elaitns on the attention of the profession.
Few physicians have had wider opportunities than the author for observation and experience, and
few perhaps have used them belter.   As the  result of a life of study and  practice, therefore, the
present volume will doubtless be received with the welcome it deserves.
  This book is eminently what it professes to be;  a
distinguished merit in these days.   Designed for
" Te.-tVliers and Students of Medicine," and admira-
bly suited to their wants, we think it will be received,
on its own merits, with a hearty welcome.—Boston
Med. and Surg. Journal.
  Indited by one of the most accomplished writers
of our country, as well as by one who h»s long held
a high position among teachers and practitioners of
medicine,  this work is entitled  to patronage  and
careful study.   The learned author has endeavored
to condense in this volume  most of  the practical
matter contained in his former productions, so as to
adapt it to  the  use of those who have not time to
devote to more extensive works.—Southern Med. and
Surg. Journal.
  We can strongly recommend Dr. Dickson's work
to our readers as one of interest and practical utility,
well deserving of a place in their libraries as a book
of reference ; and we  especially commend the first
part as presenting an admirable outl ine of  the princi-
ples of medicine.—Dublin Quarterly Journal, Ftb.
1856
  This volume, while as its title denotes it is  a
compendious view, is  also a comprehensive system
of practice, perspicuously and pleasantly written,
and admirably suited to engage the interest, and in-
struct the reader.—Peninsular Journal of Medicine,
Jan. 1856.
  Prof. Dickson's work supplies, to a great extent,
a desideratum long felt in American medicine.—A.
0. Med. and Surg. Journal.
  Estimating this work according to the purpose for
whicli it is desisned, we must think t>igbly of its
merits, and we have no hesitation in predicting for
it a favorable reception by both students and teachers.
  Not professing lo be a complete and comprehensive
treatise, it will not be found full in decail, nor filled
with discussions of theories  and opinions, but em-
biacing all  that is essential in theory  and practice,
it is admirably adapted to the wants of the American
student.  Avoiding all that is uncertain, it, presents
more  clearly to the mind of the  reader thnt. which is
established  and verified by experience.  The varied
and extensive reading of the author is conspicuously-
apparent, and all the recent  improvements and dis-
coveries in  therapeutics and pathology are chroni-
cled in its  pages.— Charleston  Med Journal.

  In the first part of the work the subject of gene-
ral pathology is presented in  outline, ghirg a tuau-
tiful   picture of  its  distinguishing features, and
throughout the succeeding chapters we find that  he
has kept  scrupulously  within  the bounds of sound
reasoning  and  legitimate deduction.   Upon  the
whole, we do not hesitate to pronounce it a superior
work  in its class, and that  Dr.  Dickson merits  a
place in the  first rank of American writers.— lVeM-.TJi
Lancet. 
AND  SCIENTIFIC  PUBLICATIONS.
11
                      DRUITT (ROBERT), M.R. C.S., &c.
THE  PRINCIPLES AND  PRACTICE  OF  MODERN  SURGERY.   A new
  ATvrenCan> fr°m the improved London  edition.   Edited bv F. W. Sargent, M. D., author of
  "Minor Surgery,"  &c.  Illustrated with one hundred and'ninety-three wood-engravings.  In
  one very handsomely printed octavo volume, leather, of 576 large pages.  $3  00.
  Dr. Druitt's researches into the literature of his
Bubject  have  been  not only extensive, but well di-
rected ;  the most discordant authors are fairly and
impartially quoted, and, while due credit is given
to each, their respective merits are weighed with
an unprejudiced hand.  The grain of wheat is  pre-
served, and the chaff is unmercifully stripped off.
The arrangement is simple and philosophical, and
the style, though clear and interesting, is so precise,
that the book contains more information condensed
into a few words than any other surgical work with
which we  are acquainted.—London Medical Times
and Gazette.

  No work, in  our opinion, equals it in presenting
so much valuable surgical matter in so small a
compass.—St. Louis Med. and  Surgical Journal.

  Druitt's Surgery is too well known to the Ameri-
can medical profession to require its announcement
anywhere.  Probably no work of the kind has ever
been more cordially received and extensively circu-
lated than this.  The fact that  it comprehends in a
comparatively small compass, all the essential ele-
ments of theoretical and practical Surgery—that it
is found to contain  reliable and authentic informa-
tion on the nature and treatment of nearly all surgi-
cal affections—is a sufficient reason for the liberal
patronage it has obtained.  The editor, Dr. F. W.
Sargent, has contributed much to enhance the value
of the work, by such American improvements as are
calculated more perfectly  to adapt it  to  our  own
views and practice in  this  country.  It abounds
everywhere with spirited and life-like illustrations,
which to the young surgeon, especially, are of no
minor consideration. Every medical man frequently
needs  just such a work as this, for immediate refer-
ence in moments of sudden emergency, when he has
not time to consult more elaborate treatises.—The
Ohio Medical and Surgical Journal.

  The author has evidently ransacked every stand-
ard treatise of ancient and modern times, and all that
is really practically useful at the bedside will be
found in a form at once clear, distinct, and interest-
ing.—Edinburgh Monthly Medical Journal.
  Druitt's work, condensed, systematic, lucid,  and
practical as it is, beyond most works  on  Surgery
accessible to the American student, has had much
currency in this country, and under its present au-
spices promises to rise to yet  higher favor.—The
Western Journal of Medicine and Surgery.

  The most accurate and ample resume; of the pre-
sent state of Surgery that we areacquaintedwith.—
Dublin Medical Journal.

  A better  book on the principles and practice of
Surgery as now understood in England and America,
has not been given to the profession.—Boston Medi-
cal and Surgical Journal.

  An unsurpassable compendium, not only of Sur-
gical, but of Medical Practice.—London  Medical
Gazette.
  This work merits our warmest  commendations,
and we strongly recommend it to young surgeons as
an admirable digest of the principles and practice of
modern Surgery.—Medical Gazette.

  It may be said with truth that the work of Mr.
Druitt affords a complete, though brief and  con-
densed view, of the entire field of modern surgery.
We know of no work on the same subject having the
appearance of a manual, which includes so many
topics of interest to the surgeon ; and the terse man-
ner in which each has been treated evinces a most
enviable quality of mind on the part of the author,
who seems to have an innate  power of searching
out and  grasping  the leading facts and features of
the most  elaborate productions  of the pen.  It is a
useful handbook for the practitioner, and we should
deem a teacher of surgery unpardonable who did not
recommend it to his pupils.  In our own opinion, it
is admirably adapted to the wants of the student.—
Provincial Medical and Surgical Journal.
           DUNGLISON, FORBES,  TWEEDIE,  AND  CONOLLY.
THE CYCLOPAEDIA OF  PRACTICAL MEDICINE: comprising Treatises on
  the Nature and Treatment of Diseases, Materia Medica, and Therapeutics, Diseases of Women
  and  Children, Medical Jurisprudence, &c. &c.   In four large super-royal  octavo volumes, of
  3254 double-columned pages, strongly and handsomely bound, with raised bands.  $12  00.
  *jj.* This work contains no less than four hundred and eighteen distinct treatises, contributed by
sixty-eight distinguished physicians, rendering it  a complete library  of reference for  the  country
practitioner.
  The most complete work on Practical Medicine
extant;  or, at least,  in our  language.— Buffalo
Medical and Surgical Journal.
  For reference, it is above all price to every prac-
titioner.—Western Lancet.
                                              titioner.  This estimate of it has not been formed
                                              from a hasty examination, but after an intimate ac-
                                              quaintance derived from  frequent consultation of it
                                              during  the past nine or ten years.  The editors are
                                              practitioners of established reputation, and the list
                                              of contributors embraces  many of the most eminent
One of the most valuable medical publications of j professors and teachers of London, Edinburgh, Dub-
the day__as a work of reference it is invaluable.—
Western Journal of Medicine and Surgery.
  It has been to us, both as learner and teacher, a
work for ready and frequent reference, one in which
modern  English medicine i3 exhibited in the most
advantageous light.—Medical Examiner.

  We rejoice that this work is to be placed within
the reach of the profession in this country,  it being
unquestionably one of very great value to the prac-
lin, and Glasgow.  It is, indeed, the great merit of
this work that the principal articles have been fur-
nished  by practitioners  who have not only devoted
especial attention to the diseases about which they
have written, but have also enjoyed opportunities
for an extensive practical acquaintance with them,
and whose reputation carries the assurance of their
competency  justly to appreciate  the opinions of
others, while it stamps their own doctrines with
high and just authority.—American Medical Journ.
DEWEESS COMPREHENSIVE SYSTEM OF
  MIDWIFERY.  Illustrated by occasional cases
  and many engravings.  Twelfth edition, with the
  author's  last improvements and corrections   In
  one octavo volume, extra cloth, of 600pages. «3 20.
HKWFES'S TREATISE ON  THE  PHYSICAL
  AND  MEDICAL TREATMENT  OF  CHILD-
  REN.  Tenth edition.   In  one volume, octavo,
RE.
extra cloth, 518 pages
$2 80.
nW'FS'S  TREATISE  ON THE DISEASES
  OF F!'M \LES   Tenth edition.  In one volume,
  oetavo,'extra cloth, 532 pages, with  plates. S3 00.
DANA ON ZOOPHYTES AND CORALS.  Inone
  volume, imperial quarto, extra cloth, with wood-
  cuts. $15 00.  Also, AN ATLAS, in one volume,
  imperial folio, with sixty-one magnificent colored
  plates.   Bound in half morocco.  $30 00.
DE LA BECHE'S GEOLOGICAL OBSERVER.
  In one very large and handsome octavo volume, ex-
  tra cloth, of 700 pages, with 300 wood-cuts. $4 00.
FRICK ON  RENAL AFFECTIONS; their Diag-
  nosis and Pathology.  With illustrations.  One
  volume, royal 12mo., extra cloth.  75 cents. 
12
BLANCHARD &  LEA'S  MEDICAL
                          DUNGLISON  (ROBLEY),  M.D.,
          Professor of Institutes of Medicine in the Jefferson Medical College, Philadelphia.

MEDICAL  LEXICON;  a Dictionary  of Medical Science,  containing a concise
  Explanation of the various Subjects and Terms of Physiology, Pathology, Hygiene, Therapeutics,
  Pharmacology, Obstetrics, Medical Jurisprudence, &c.  With the French and other Synonymes;
  Notices of Climate and of celebrated Mineral Waters;  Formulae for various Officinal, "Empirical,
  and Dietetic Preparations, etc. Thirteenth edition, revised, is now ready.  In one very thick
  octavo volume, of over nine hundred large double-columned pages, strongly bound in  leather,
  with raised bands.   $4 00.
  Every successive edition of this work bears the marks of the industry of the author, and of his
determination to keep it fully on a level with the most advanced state of medical science.  Thus
nearly fifteen thousand words have been added to it within the last few years.   As a complete
Medical Dictionary, therefore, embracing  over  FIFTY THOUSAND  DEFINITIONS, in  all the
branches of the science, it is presented as meriting a continuance of the great  favor and popularity
which have carried it, within no very long space of time, to a thirteenth edition.
  Every precaution has been taken  in the preparation of the present volume, to render its mecha-
nical execution and typographical accuracy worthy of its  extended reputation and universal use.
The very extensive additions have been accommodated, without materially increasing the  bulk of
the volume  by the  employment of a small  but exceedingly clear type, cast for this purpose.  The
press has been watched with great care, and every effort used to insure the verbal accuracy so ne-
cessary to a work of this nature.   The whole is printed on fine white paper; and, while thus exhi-
biting in every respect so great an improvement over former issues, it is presented  at the  original
exceedingly low price.

  We welcome it cordially; it is an admirable work,
and indispensable to all literary medical men. The
labor which  has been bestowed upon it is something
prodigious.  The work, however, has now been
done, and we are happy in  the thought that no hu-
man being will have again to undertake the same
gigantic task.  Revised and corrected from time to
time, Dr. Dunglison's "Medical Lexicon" will last
for centuries.—British and Foreign Med.-Chirurg.
Review.
  The fact that this excellent and learned work has
passed through eight editions, and that a ninth is
rendered necessary by the demands of the public,
affords a sufficient evidence of the general apprecia-
tion of Dr. Dunglison's labors by the  medical pro-
fession in England and America.  It is a book which
will be of great service to the student, in teaching
him  the meaning of  all the technical terms used in
medicine, and will be of no less use to  the practi-
tioner who desires to keep himself on a level with
the advance of medical science.—London Medical
Times and Gazette.
  In taking leave of our author, we feel compelled
to confess that his work bears evidence of almost
incredible labor having been bestowed upon its com-
position.—Edinburgh Journal of Med. Science.
  A  miracle of labor and  industry in  one who has
written able and voluminous works on nearly every
branch of medical science.  There could be no more
useful book  to the student  or  practitioner,  in the
present advancing age, than one  in which would be
found, in addition to the ordinary meaning and deri-
vation of medical  terms—so many of which  are of
modern introduction—concise descriptions of their
explanation and employment; and all this and much
more is contained in the volume before us   It is
therefore almost as indispensable to the other learned
professions as to our own.  In fact, to all who may
have occasion to ascertain the meaning of any word
belonging to  the many branches of medicine.  From
a careful examination of the present edition, we can
vouch for its accuracy, and  for its being brought
quite up to thedate of publication ; the author states
in his preface that he has added to it about four thou-
sand terms, which are not to be  found in the  prece-
ding one. — Dublin  Quarterly Journal of Medical
Sciences.
  On the  appearance  of the  last edition of this
valuable  work,  we  directed the attention  of oui
readers to  its peculiar merits; and we need do
little more than state, in  reference to the present
reissue, that, notwithstanding the large additions
previously  made to it, no fewer  than four thou-
sand terms, not to be found in the preceding  edi-
tion, are  contained  in the  volume  before us.—
Whilst it is a wonderful monument, of its author's
erudition and industry, it  is also n work of great
practical utility, as we can  testify from our own
experience; for we keep it constantly within  oui
reach,  and  make  very frequent  reference to it,
nearly always finding in it  the information we seek.
—British and Foreign Med.-Chirurg. Review.

  It has the rare merit that it certainly has no rival
in the English  language for accuracy and extent
of references. The terms generally include short
physiological and pathological descriptions, so that,
as the  author justly observesj the reader does not
possess in this work a mere dictionary, but a book,
which, while it instructs him in medical etymo-
logy, furnishes  him with a large amount of useful
information.  The  author's labors have  been pro-
perly appreciated by his own countrymen; and we
can only confirm their judgment, by recommending
this most useful volume to the notice of  our cisat-
lantic readers. No medical library will be complete
without it.—London Med. Gazette.

  It is certainly more complete and comprehensive
than any with  which  we are acquainted in  the
English language.  Few,  in  fact, could be found
better qualified than Dr. DungHson for the produc-
tion  of such a  work.  Learned, industrious, per-
severing, and accurate, he brings to the task all
the peculiar  talents necessary  for  its  successful
performance; while, at the  same time,  his fami-
liarity  with the writings of the ancient and modem
" masters of our art,"  renders him skilful to note
the exact usage of the several  terms of science,
and the various modifications which medical term-
inology has undergone with  the change  of theo-
ries or the  progress of improvement. — American
Journal of the Medical Sciences.
  One of the  most complete and copious  known to
the cultivators  of medical science.—Boston Med.
Journal.

  The  most comprehensive and best English Dic-
tionary of medical  terms extant.—Buffalo Mediial
Journal.
BY THE SAME AUTHOR.
THE PRACTICE  OF  MEDICINE.   A Treatise on Special Pathology and The-
  rapeutics.  Third Edition.  In two large octavo volumes, leather, of 1,500 pages.  $8 25.
  Upon every topic embraced in the work the latest
information  will  be  found  carefully  posted up.—
Medical Examiner.

  The  student of  medicine will  find,  in these two
elegant volumes,  a mine of facts, a  gathering of
pTecepts and advice from the world of experience,
that  will nerve him with courage, and faithfully
direct him in his efforts to relieve the physical suf-
ferings of the race.—Boston Medical and Surgical
Journal,

  It is certainly the most complete treatise of which
we have any knowledge.— Western Journal of Medi-
cine and Surgery.

  One of the mos (elaborate  treatises of the ki::i
we have.—Southern  Med. and  Surg. Journal. 
AND SCIENTIFIC  PUBLICATIONS.
13
                         DUNGLISON  (ROBLEY),  M.D.,
          Professor of Institutes of Medicine in the Jefferson Medical College, Philadelphia.

HUMAN  PHYSIOLOGY.   Eighth  edition.   Thoroughly revised  and  exten-
  sively modified and enlarged, with five  hundred and thirty-two illustrations.  In two large and
  handsomely printed octavo volumes, leather, of about 1500 pages.  (Now Ready, 1856.)   $7 00.
  In revising this work for its eighth appearance, the author has spared no labor to render it worthy
a continuance of the very great favor which has been extended to it by the profession.  The whole
contents have been rearranged, and to a great extent remodelled; the investigations which  of late
years have been so numerous and so important,  have been carefully examined and incorporated,
and the work in every respect has been brought up to a level with the present state of the subject.
The object of the author has been to render it a concise but comprehensive treatise, containing the
whole body of physiological science, to which the student and man of science can  at all times  refer
with the certainty of finding whatever they are in search of, fully presented in all its aspects; and
on no former edition has the author bestowed more labor to secure this result.
  A similar improvement will be found  in  the typographical execution  of the volumes, which, in
this respect, are superior to their predecessors. A large number of additional wood-cuts have been
introduced, and the series of  illustrations  has been greatly modified by the  substitution of many
new ones for such  as were  not  deemed satisfactory.   By an enlargement of the  page,  these very
considerable  additions have been accommodated without increasing  the size of the volumes to an
extent to render them unwieldy.
  It has long since taken rank as  one of the medi- | should be without it.  It is the completest work on
eal classics of our  language.  To say that it is by  Physiology in the English language, and is highly
far the best text-book of physiology ever  published  | creditable to the author and publishers.—Canadian
in this  country, is but echoing the general testi-
mony of the profession.—N. Y. Journal of Medicine.
  There is no single book we would recommend to
the student  or physician, with greater confidence
than the present, because in it will be found a mir-
Medical Journal.
  The most complete and satisfactory  system of
Physiology in the English language.—Amer. Med.
Journal.
  The best work of the kind in the  English Ian-
rorof" almost" every standard phvsioloeical work of \ guage.—S^iman's Journal.
the day. We most cordially recommend the work   The most full and complete system of Physiology
to every member of the profession, and no  student I in our language.—Western Lancet.
BY THE SAME AUTHOR.
GENERAL  THERAPEUTICS  AND   MATERIA MEDICA;  adapted  for a
  Medical Text-book.  Fifth edition, much improved.  With one hundred and eighty-seven illus-
  trations.  In two large aud handsomely printed octavo vols., leather, of about 1100 pages. $6  00.
  In this work of Dr. Dunglison,we recognize the
game untiring industry in the  collection and em-
bodying of facts on the several subjects of which he
treats, that has heretofore distinguished him, and
we cheerfully point to these volumes, as two of the
most interesting that we know of.  In noticing the
additions to this, the fourth edition, there  is very
little in  the periodical or  annual literature of the
profession, published in  the  interval  which  has
elapsed since the issue of the first, that  has escaped
the careful search of the  author.  As a book for
reference, it is invaluable.—Charleston Med. Jour-
nal and Review.
  It may be said to be the work now upon the sub-
jects upon which it treats.— Western Lancet.
  As a text-book for students, for whom it is par-
ticularly designed, we know of none superior to
it.—St. Louis Medical and Surgical Journal.

  It purports to be a new edition, but it is rather
a new book, so greatly has it been  improved, both
in the amount and quality of the matter which it
contains.—N. O. Medical and Surgical Journal.

  We bespeak for this edition, from the profession,
an increase of patronage over  any of its former
ones,  on account  of its  increased merit. — N. Y.
Journal of Medicine.

  We consider this work  unequalled.—Boston Med.
and Surg. Journal.
                        BY THE  same author.  (A new Edition.)

NEW REMEDIES, WITH  FORMULAE FOR THEIR  PREPARATION AND
  ADMINISTRATION.  Seventh edition, with extensive Additions.  In one very large octavo
  volume, leather, of 770 pages.  (Now Ready, May, 1856.)  $3 75.
  Another edition of the " New Remedies"  having been called for, the author has endeavored  to
add everything of moment that has appeared since the publication of the la*t edition.
  The chief remedial means which have obtained a place, for the first time, in this volume, either
owing to their having been recently introduced into pharmacology, or to their having received novel
applications—and which, consequently, belong to the category of « New Remedies  -are the fol-

l° Anio|:"CafTein, Carbazotic acid, Cauterization and catheterism of the larynx and trachea, Cedron,
Cer urn!  Chloride of bromine, Chloride of iron, Chloride of sodium, Cinchonioine, Cod-liver oleiti,
Congelation Eau de Pajrliari, Galvanic cautery, Hydriodic ether, Hyposulphite of soda and silver,

FnunfS^
Rennet  Saccharine carbonate of iron and  manganese. Santonin, Tellurium, and Traumatic, ne.
  The artteW treated of in the former editions will be found to  have undergone considerable ex-
DanStin thfsin order that the author might be  enabled to introduce as far as practicable the
Kt "of the  subsequent experience of others, as well  as of his own observation and reflection
and to make the work still more deserving of the  extended circulation with which  the preceding
edftio^is have  been favored by the profession.  By an enlargement of the page, the numerous addi-
tions  have been incorporated without greatly increasing the bulk of the7°lume;~f "£"*■
  One of the most useful of the author's works.—
Southern Medical and Surgical Journal.
  This elaborate and  useful  volume  should  be
   nd in every medical library, for as a book of re-
r  nee  for  physicians, it is  unsurpassed by any
 n7r work in existence, and the double index for
"„,,, and  for remedies, will be found greatly to
enhance its value.-iVeu, York Med. Gazette.
  The great learning of the author, arid his remark-
able industry in  pushing his  researches  .nto^every
source whence information is derivable, has enabled
him to throw together an extensive mass of facts
und statements, Accompanied by full reference to
authorities; which last feature renders the work
practically'valuable to investigators whe.desireito
examine tne original papers.-IVie American Journal
of Pharmacy. 
14
BLANCHARD  &  LEA'S  MEDICAL
                                  ERICHSEN  (JOHN),
                     Professor of Surgery in University College,  London, &c.

THE SCIENCE  AND ART OF SURGERY;  being a Treatise on Surgical
  Injuries, Diseases, and Operations.   Edited  by John H.  Brinton, M. D.  Illustrated with
  three hundred and  eleven engravings on wood.  In one large and handsome octavo volume, of
  over nine hundred closely printed pages, leather, raised bands.  $4 25.
                                               rarely encounter cases requiring surgical  manage-
                                               ment.—Stethoscope.
  It is, in our humble judgment, decidedly the best
book of the kind in the English language.  Strange
that just such hooks are not oftener produced by pub
lie teacher? of surgery in this  coumry and  Great
Britain  Indeed, it is a matter of great astonishment.
but no less irue than astonishing, that of the  many
works on surgery republished in this country within
the last  fifteen or twenty years as text-books for
medical students, this is the only one that  even ap-
proximates lo the fulfilment of the peculiar wants of
young men just entering upon the study of this branch
of the profession.— Western Jour, of Med. anil Surgery.

  Its value is greatly enhanced by a very copious
well arranged index.  We regard this as one  of the
most valuable contributions to modern surgery. To
one enterine his novitiate of practice, we regard it
the mosi serviceable guide which he can consult.  He
will find a fulness of detail leading him through every
slep of the operation, and not deserting him until the
final issue of the case is decided  For the same rea-
son wp recommend it to those whose routine of prac-
tice lies in such parts of the country that they must
  Embracing, as will be perceived, the whole  surgi-
cal domain, and each division of itself almost com-
plete and pprfect, each chapter full and explicit, each
subject faithfully exhibited, we can only express our
esiimate of it in  the aggregate.  We consider it an
excellent contribution  to surgery, as probably  the
best single volume now extant on the subject,  and
with great pleasure we add  it lo our text books —
Nanhv tile Journal  of Medicine and Surgery.

  Prof. Erichsen's work, for its  size, has not been
surpassed; his nine hundred and eight pages, pro-
fusely illustrated,  are rich in physiological, patholo-
gical, and operative suggestions, doctrines, details,
and processes ; and will  prove  a reliable resource
for information, both to physician  and surgeon, in the
hour of peril— N.  0. Med. and Surg. Journal.

  We are acquainted with no other  work wherein
so much good sense, sound  principle, and practical
inferences, stamp every page.—American Lancet.
                             ELLIS (BENJAMIN), M.D.
THE  MEDICAL  FORMULARY:  being a Collection of  Prescriptions,  derived
  from the writings and practice of many of the most eminent physicians of America and Europe.
  Together with the  usual Dietetic Preparations and Antidotes for Poisons.   To which is added
  an  Appendix, on the Endermic use of Medicines, and on the use of Ether and Chloroform.   The
  whole accompanied with a few  brief Pharmaceutic and Medical Observations.   Tenth edition,
  revised and much extended by Robert P. Thomas, M. D., Professor of Materia Medica in the
  Philadelphia College of Pharmacy.   In one neat octavo volume, extra cloth, of 296 pages. (Lately
  Issued.)  f 1 75.
  After an examination of the new matter and the
alterations, we believe the reputation of the work
built up by the author, and the late distinguished
editor, will continue to flourish under the auspices
of the present editor, who has the industry and accu-
racy,  and, we would say, conscientiousness requi-
site for the responsible task.—Am. Jour, of Pharm.
  It will prove particularly useful to students and
young practitioners, as the most important prescrip-
tions employed in modern practice, which lie scat-
tered through our medical literature, are here col-
lected and conveniently  arranged for reference.—
Charleston Med. Journal  and Review.
                        FOWNES  (GEORGE),  PH. D., &c.
ELEMENTARY  CHEMISTRY;   Theoretical and  Practical.   With  numerous
  illustrations.  A new American, from the last and revised London edition.  Edited, with Addi-
  tions, by Robert Bridges, M. D.   In one large royal 12mo. volume, of over 550 pages, with 181
  wood-cuts.  (Lately Issued.)  In leather, $1 50; extra cloth, $1 35.
  We know of no better text-book, especially in the
difficult department of organic  chemistry, upon
which it is particularly full and satisfactory.  We
would recommend  it  to  preceptors as a  capital
" office book" for their students who are beginners
in Chemistry.  It is copiously illustrated with  ex-
cellent wood-cuts,  and altogether admirably "got
dp."—iv\ j. Medical Reporter.
  A standard manual, which  has  long enjoyed the
reputation of embodying much knowledge in a small
space. The author hasachieved the difficult task of
condensation with masterly tact.  His book is con-
cise without being  dry, and brief without being too
dogmatical or general.— Virginia Med. and Surgical
Journal.
  The work of Dr.  Fownes has long been before
the public, and its merits have been  fully appreci-
ated  as  the best text-book on chemistry now in
existence.  We do not, of course, place it in a rank
superior to the works of Brande, Graham,  Turner,
Gregory, or Gmelin, but we say that, as a work
for students, it is preferable to any of them.—Lon-
don Journal of Medicine.
  A work well adapted to the wants of the student.
It is an excellent exposition of the chief doctrines
and facts of modern chemistry. The size of the work,
and still more the condensed yet perspicuous  style
in which it is  written,  absolve it from the charges
very properly  urged against most manuals termed
popular.—Edinburgh Journal of Medical Science.
                       FERGUSSON  (WILLIAM), F. R. S.,
                      Professor of Surgery  in King's College,  London, &c.
A  SYSTEM  OF  PRACTICAL SURGERY.   Fourth American, from the third
  and enlarged London edition.  In one large  and beautifully printed octavo volume, of about 700
  pages, with 393 handsome illustrations, leather.  $3 00.
  The most important subjects in connection with
practical surgery which have been more recently
brought under  the notice of, and discussed by, the
surgeons of Great Britain, are fully and dispassion-
atefy considered by Mr. Fergusson, and that which
was before wanting has now been supplied, so that
we can now look upon it as a work on practical sur-
gery instead of  one  on operative surgery alone.
Medical Times and Gazette.

  No work was  ever written which more  nearly
Comprehended  the necessities of the student  and
practitioner, and was  more carefully arranged to
that single purpose than this.—N. Y. Med. Journal.
  The addition of many new pages makes this work
more than ever indispensable to the student and prac-
titioner.—Ranking's Abstract.
  Among the numerous works upon surgery pub-
lished of late years,  we  know of none we value
more highly than  the one before us.  It  is perhaps
the very best we have  for a text-book and for ordi-
nary reference, being concise and eminently practi-
cal.—Southern Med. and Surg. Journal. 
AND SCIENTIFIC  PUBLICATIONS.
15
                             FLINT (AUSTIN), M. D.,
        Professor of the Theory and Practice of Medicine in the University of Louisville, &c.
                                 (An Important New  Work.)

PHYSICAL EXPLORATION AND DIAGNOSIS  OF  DISEASES  AFFECT-
  ING THE RESPIRATORY  ORGANS.   In one  large and  handsome  octavo  volume, extra
  cloth, 636 pages.  (Now Ready.) $3  00.
  The author has aimed in the present work to  supply a vacancy in medical literature, viz:  "a
work limited to diseases affecting the respiratory organs, treating in extenso and almost exclusively
ofthe principles and practice of physical exploration, as applied to the diagnosis of those affections."
The intricacy and importance of trie subject demand a fuller and nnore detailed exoosition than has
been accorded to  it  in any volume  as yet accessible to  the American profession ;  while the high re-
putation which the author has acquir-'d by his researches in kindred topics sufficiently manifests his
ability to render the present work a text-book of great  practical utility for the student, and a source
to which the practitioner can at all times refer with certainty.
  A very condensed summary of the contents is subjoined.
                                        CONTENTS.
              INTRODUCTION.
Section I. Preliminary points pertaining to the Ana-
  tomy and Physiology of the Respiratory Appara-
  tus.  Section II. Topographical Divisions of the
  Chest.

                   PART I.

     Physical Exploration of the Chest.

Cha.p. I. Definitions—Different Methods of Explora-
  tions—General Remarks.  Chap. II.  Percussion.
  Chap. III. Auscultation.  Chap. IV. Inspection.
  Chap. V.  Mensuration.   Chap. VI. Palpation.
  Chap. VII. Succussion.  Chap. VIII. Recapitu-
  latory Enumeration of the Physical Signs  fur-
  nished  by the  several methods of Exploration.
  Chap.  IX. Correlation of Physical Signs.
                  PART II.
Diagnosis of Diseases  Affecting the Respira-
                tory Organs.
Chap. I. Bronchitis, Pulmonary or Bronchial  Ca-
  tarrh.  Chap. II. Dilatation  and Contraction of
  the Bronchial Tubes— Pertussis— Asthma. Chap.
  III. Pneumonitis—Imperfect Expansion (Atelec-
  tasis) and Collapse.   Chap. IV.  Emphysema.
  Chap. V.  Pulmonary  Tuberculosis — Bronchial
  Phthisis.  Chap.  VI.  Pulmonary (Edema-Gan-
  grene of the  Lungs—Pulmonary  Apoplexy—Can-
  cer of  the Lungs—Cancer in the Mediastinum.
  Chap. VII. Acute Pleuritis—Chronic  Pleuritis—
  Empyema—Hvdrothorax— Pneumothorax— Pneu-
  mo-hydrothorax-Pleuralgia- Diaphragmatic  Her-
  nia.  Chap. VIII. Diseases affecting the Trachea
  and Larynx—Foreign Bodies in the Air-passages.
  Appendix. On the Pitch of the Whispering Souffle
  over Pulmonary Excavations.
                          GRAHAM  (THOMAS),  F. R. S.,
                   Professor of Chemistry in University College, London, &c.
THE ELEAIENTS OF CHEMISTRY.   Including the application of the Science
  to the Arts  With numerous illustrations.  With Notes and Additions,  by Robert Bridges,
  M. D., &c. &c.  Second American, from the second and enlarged London edition.
PART I. (Lately Issued) large 8vo., 430 pages, 185 illustrations,  f 1 50.
PART II. (Preparing) to match.__________________

                      GRIFFITH  (ROBERT E.), M. D., &c.
A  UNIVERSAL FORMULARY, containing the methods of  Preparing and Ad-
  ministerin- Officinal and other Medicines.  The whole adapted to Physicians and Phaxmaceu-
  tiZ   Second Edition, thoroughly revised, with numerous additions, by Robert P. Thomas,
  MD  Profe" sofo  Materia Medica" in the Philadelphia College of Pharmacy.  In one lar.^e and
  handsome octavo volume, extra cloth, of over 600 pages, double columns.  (Just Issued.) $3 00,
  or bound in sheep, $3 25.
  It was a work  requiring much perseverance, and .ioner can possibly have in  hts possesston.-ilfeW
wherTpublished wal lookld upon as by far the bes, I Chronicle.
work of its kind that had issued from the American
press.  Prof Thomas has certainly" unproved,'  as
well as added o this Formulary, and has rendered it
additionally deserving of the confidence of ph»'™«-
ceutists and physicians.-^. Journal of Pharmacy.

  We are happy to announce  a new and improved
edition of this, one ofthe most valuable and useful
works that have emanated from an American pen.
It would do credit to any country, and will he found
of daily usefulness to practitioners of medicine, it is
better adapted to their purposes than the dispensato
ries.-Southern Bled, and Surg. Journal.
  A new edition of ihis well-known work, edited by
R P Thoma" M D., affords occas.oii for renewing
ou.'commMd'a on of so useful a handbook, which
oughuo be universally '"died Iby  me.tea men of
everv cla« and made use of by way of red r. nee ny
 ffi„2 n„n,l-  as a standard authority. It  has been
office oupiU, *s *dTnow condenses a vast amount
"rUCh h7 and  necessary knowledge in small com-
of "eedful and  nece  J      thp <J)pUer for lhe pro.
pass.  The mor^ o  u^          Gazette.
fession and the punuc
  It is one ofthe most useful books a country practi-
  The amount of useful, every-day matter, for a prac-
ticing physician,  is really immense.— Boston Med.
and Surg. Journal.
  This is a work of six hundred and fifty one  pages,
embracing all on the subject of preparing and admi-
nistering medicines that can be desired by the physi-
cian  and pharmaceutist — Western Lancet
  In  short, it  is a full and complete work of the kind,
and should be m the hands of every physician and
apothecary.  O  Med. and Surg. Journal
  We predict a great sale for this work, and we espe-
cially recommend it to all medical teachers.— Rich-
mond Stethoscope.
  This edition of Dr Griffith's work has been sreatly
improved by the revision and ample additions ot Ur
Thomas,  and is now. we believe, one of  the most
complete works of it* kind  in any language.  The
addition* amount to about seventy  page> .and no
effort ha- been  spared to include in them all  the re-
cent  improvements which have been published  in
medical journals, and systematic ue^mr,   A work
of this kind appears lo u« indispensable o he physi-
cian and ihereisnone we can more cordially recom-
 mend.— N. Y. Journal of Medicine.
BY THE SAME AUTHOR.
,,-n-m-PAT   -ROTHNY;  or, a Description of all the more  important  Plants used
MEDIOAL.  »y J-f\  .  Properties, Uses, and Modes of Administration.  In one large octavo
  in Medicine, and of the„ * rope■                             ^ iUustratlon8 on wood.  $3 00. 
16
BLANCHARD  &  LEA'S MEDICAL
                          GROSS (SAMUEL DJ,  M. D.,
             Professor of Surgery in the Jefferson Medical College of Philadelphia, &c.

A  PRACTICAL   TREATISE  ON  THE  DISEASES,   INJURIES,  AND
  MALFORMATIONS OF  THE URINARY BLADDER,  THE PROSTATE GLAND, AND
  THE URETHRA.  Second Edition, revised and  much enlarged, with one hundred and eighty-
  four illustrations.  In one large and very handsome octavo volume, of over nine hundred pages.
  (Just Issued.)  In leather,  raised bands, $5 25; extra cloth, $4 75.
  The author has availed himself of the opportunity afforded by a call for  a new edition of (his
work, to thoroughly revise and render it in every respect worthy, so far as in his power, of the very
flattering reception which has been accorded to it by the profession.  The new matter thus added
amounts to almost one-third ofthe original work,  while the number of illustrations has been nearly
doubled.   These additions pervade every portion of the work, which thus  has rather  the aspect of
a new treatise than a new edition.  In its  present improved form, therefore, it may confidently be
presented as a complete and reliable storehouse of information on this important  class of diseases,
and as in every way fitted to maintain the position  which it has acquired in Europe and in  this
country, as the standard of authority on the subjects treated of.
  A volume replete with truths  and principles ofthe
utmost value in the investigation of these diseases.—
American Medical Journal.
  On the appearance of the first edition of this work,
the leading English medical review predicted that it
would have a " permanent place in the literature of
surgery worthy to rank with the best works of the
present age."  This prediction has been amply ful-
filled. Dr. Gross's treatise has  been found  to sup-
ply completely the want which  has been felt ever
since the elevation of surgery to the rank of a science,
of a good practical treatise on  the diseases of the
bladder and its accessory organs. Philosophical in
its design, methodical in its arrangement, ample and
sound in its practical details, it may in truth  be said
to leave scarcely anything to be desired on  so im-
portant a subject, and with the additions and modi-
fications resulting from future discoveries and im-
provements, it will probably remain one of the most
valuable works on this subject so long as the science
of medicine shall exist.—Boston Med. and  Surg.
Journal.
 "Dt.  Gross has brought all his learning, experi-
ence, tact, and judgment to the task, and has pro-
duced  a work worthy of his high reputation.  We
feel perfectly safe in recommending it to our read-
ers  as a  monograph unequalled  in  interest and
practical value by any other on the subject in our
language.—Western Journal of Med. and Surg.
  Whoever will peruse the vast amount of valuable
practical  information it contains, and which we
have been unable even  to notice, will, we think,
agree with us, that there is no work in the English
language which can make any just pretensions to
be its equal.—N. Y. Journal of Medicine.
                           BY THE same author.  (Just Issued).
A PRACTICAL TREATISE ON FOREIGN BODIES  IN THE AIR-PAS-
  SAGES.   In one handsome octavo volume, extra cloth, with illustrations,  pp. 468.   $2 75.
  A very elaborate work. It is a complete summary
of the whole subject, and will  be a useful book of
reference.—British and  Foreign Medico-Chirurg.
Review.
  A highly valuablebook of reference on a most im-
portant subject in the practice of medicine.  We
conclude by recommending it to our readers, fully
persuaded that its perusal will afford them much
practical information well conveyed, evidently de-
rived from considerable experience and deduced from
an ample collection of facts. — Dublin Quarterly
Journal, May, 1855.
                           BY the same author.  (Preparing.)

A SYSTEM OF SURGERY; Diagnostic, Pathological, Therapeutic, and Opera-
  tive.  With very numerous engravings on wood.

                           by the same author.  (Preparing.)

ELEMENTS  OF  PATHOLOGICAL  ANATOMY;  illustrated  by several hun-
  dred wood-cuts.   New edition, thoroughly  revised.   In one  very large and handsome octavo
  volume.
                          GLUGE  (GOTTLIEB),  M.D.,
        Professor of Physiology and Pathological Anatomy in the University of Brussels, &c.
AN  ATLAS  OF  PATHOLOGICAL HISTOLOGY.  Translated, with Notes
  and Additions, by Joseph Leidy, M. D., Professor of Anatomy in the University of Pennsylva-
  nia.  In one volume, very large imperial quarto, extra cloth, with 320 figures, plain and colored,
  on twelve copperplates.  $5  00.
GARDNER'S MEDICAL CHEMISTRY, for  the
  use of Students and the Profession.  In one royal
  12mn. vol., ex. cloth, pp. 396, with illustrations.
  $t 00.
HARRISON'S ESSAY TOWARDS A CORRECT
  THEORY  OF THE NERVOUS SYSTEM.  In
  one octavo  volume, leather, 292 pages.  $1 50.
HUGHES'  CLINICAL INTRODUCTION  TO
  THE PRACTICE OF AUSCULTATION AND
  OTHER MODES OF PHYSICAL DIAGNOSIS,
  IN DISEASES OF THE LUNGS AND HEART.
  Second American, from the second London edition.
  1 vol. royal 12mo., ex. cloth, pp. 304.  $1  00.
                       HAMILTON  (FRANK  H.),  M.  D.,
                     Professor of Surgery, in Buffalo Medical College, &c.

A TREATISE  ON  FRACTURES AND DISLOCATIONS.   In one handsome
  octavo volume, with numerous illustrations.  (Preparing.)
  The numerous improvements which this important branch of surgery has received from the skill
and ingenuity of American  surgeons, renders particularly appropriate and valuable a complete and
systematic original  work on the subject.   The essays which Professor Hamilton has  published on
kindred topics are already widely and favorably known, and give earnest that his forthcoming work
will prove indispensable, both as a text-book for the student, and as a guide for the practitioner. 
AND SCIENTIFIC  PUBLICATIONS.
17
                         HOBLYN  (RICHARD D.),  M. D.

A DICTIONARY  OF  THE  TERMS  USED  IN MEDICINE  AND  THE
  COLLATERAL SCIENCES.  By Richard D. Hoblyn, A. M, &c   A new American from
  the last London edition.  Revised, with numerous Additions, by Isaac Hays, M. D., editor of
  the "American Journal of the  Medical Sciences."  In one  large royal 12mo.  volume, leather,
  of over 500 double columned pages.   (Now Ready, 1856.)  $ 1 50.
  If the frequency with which we have referred to
this volume since its reception  from the publisher.
two or three weeks ago, be any  criterion for the
future, the binding will soon have to be renewed, even
with careful handling.  We find that Dr. Hays has
done the profession great service bv his careful and
industrious labors.  The Dictionary has thus become
eminently  suited  to our  medical brethren in this
country.  The additions by Dr. Hays are in brackets,
and we believe there is nota single page but bears
these insignia; in every instance which we have thus
far noticed, the additions are reallv needed and ex-
ceedingly valuable.  We heartily co'mmend the work
to all who wish to be au courant in medical termi-
nology.—Boston Med. and Surg. Journal.
  To both practitioner and  student, we recommend
this dictionary as being convenient in size, accurate
in definition, and sufficiently full and complete for
ordinary consultation.—Charleston Med. Journ. and
Review.
  Admirably calculated to  meet the wants of the
practitioner or student, who has neither the means
nor desire to procure a larger work. — American
Lancet.
  Hoblyn has always been a favorite dictionary, and
in its present enlarged and improved form will give
greater satisfaction than ever. The American editor,
Dr. Hays, has made many very valuable additions.
—N.J. Med. Reporter.
  To supply the want of the  medical reader arising
from this cause, we know of no dictionary better
arranged and adapted than the one bearing the above
title.  It is not encumbered with the obsolete terms
of a bygone age, but it contains all that  are now in
use ; embracing every department of medical science
down to the very latest date.  The volume is of a
convenient size to be used by the  medical student,
and yet large enough to make a  respectable appear-
ance in the library of a physician.—Western Lancet.
  Hoblyn's Dictionary has long  been a favorite with
us.  It is the best book of definitions we have, and
ought always to be upon the student's  table.-^-
Southern Med. and Surg. Journal.
             HOLLAND  (SIR  HENRY),  BART.,  M.D.,F.  R.S.,
                      Physician in Ordinary to the Queen of England, &c.
MEDICAL  NOTES  AND REFLECTIONS.   From  the third  London edition.
  In one handsome octavo volume, extra cloth.   (Now Ready.)  $3  00.
  As the work of a thoughtful and observant physician, embodying the results of forty years' ac-
tive professional experience,  on topics of the  highest interest, this volume is commended to the
American practitioner as well worthy his  attention.  Few will rise  from its perusal without feel-
ing their convictions  strengthened, and armed  with new weapons for the daily struggle with
disease.
                                 HUNTER (JOHN).
TREATISE  ON  THE VENEREAL DISEASE.
  Dr. Ph. Ricord, Surgeon to the Venereal Hospital of Paris.
  F. J. Bumstead, M. D.  In one octavo volume, with plates.
With copious Additions, by
Edited, with additional Notes, by
$3 25.  I3P See Ricord.
Also, HUNTER'S COMPLETE WORKS, with Memoir, Notes, &c. &c.
  volumes, leather, with plates.  $10 00.
In four neat octavo
                        HORNER (WILLIAM  E.), M. D.,
                    Professor of Anatomy in the University of Pennsylvania.
SPECIAL  ANATOMY  AND  HISTOLOGY.   Eighth edition.   Extensively
  revised and  modified.  In two large octavo volumes, extra  cloth,  of more than one thousand
  pages, handsomely printed, with over three hundred illustrations.  $6 00.
  This edition enjoyed a thorough and laborious revision on the part  of the author shortly before
his death, with the view of bringing it fully up to the existing state of knowledge on the subject of
general and special anatomy.  To adapt it more perfectly to the wants ofthe student, he introduced
a large number of additional wood-engravings, illustrative ofthe objects described, while the pub-
lishers have endeavored to render the mechanical execution of the work worthy of its extended
reputation.

                        JONES  (T.  WHARTON), F. R. S.,
         Professor of Ophthalmic Medicine and Surgery in University College, London, &c.
THE PRINCIPLES  AND  PRACTICE  OF  OPHTHALMIC   MEDICINE
  AND SURGERY.  With one  hundred and ten illustrations.   Second American from the second
  and revised London edition, with additions b/ Edward Hartshorne, M. D., Surgeon to Wills'
  Hospital, &rc  In one large, handsome  royai 12mo. volume, extra cloth, of 500 pages.  (Now
  Ready.)  $1 50
  We are confident that the reader will find, on
perusal that the execution ofthe work amply fulfils
the  promise of the preface, and sustains, in every
point  the already hgh reputation of the author as
an ophthalmic surgeon  as well as a physiologist
and pathologist.  The book is  evidently the result
of much labor and research, and has been written
with the  greatest care and attention; it possesses
that best  quality which a general work, like a sys-
tem or manual can show, viz : the quality of having
 11 the materials whencesoever derived, so thorough-
ly wrought up, and digested in the author's mind,
as to come forth with the freshness and impressive-
ness of an original production. We entertain little
doubt that this book will become what its author
hoped  it might become, a manual for daily reference
and consultation by the student and the general prac-
titioner.   The work is marked by that correctness,
clearness, and precision of style which distinguish
all the productions of the learned author.—British
and For. Med. Review. 
18
BLANCHARD &  LEA'S  MEDICAL
JONES (C.  HANDFIELD),  F. R. S.,  & EDWARD  H. SI EV EKING, M.D.,
                Assistant Physicians and Lecturers in St. Mary's Hospital, London.

A  MANUAL OF  PATHOLOGICAL  ANATOMY.  First  American  Edition,
  Revised.  With three hundred and ninety-seven  handsome wood engravings.   In one large and
  beautiful octavo volume of nearly 750 pages, leather.  (Lately Issued.) $3  75.
  Asa concise text-book, containing, in a condensed
form, a complete outline of what is  known in  the
domain of Pathological Anatomy, it is perhaps  the
best work in the English language.  Its great merit
consists in its completeness and brevity, and in this
respect it supplies a great  desideratum in our lite-
rature.  Heretofore the  student of  pathology was
obliged to glean from a great number of monographs,
and the field was so extensive that but few cultivated
it with sny degree of success.  As a simple work
of reference, therefore, it  is  of great value to  the
student of pathological anatomy, and should be in
every physician's library.—Western Lancet.
  We urge upon our readers and the profession gene-
rally the importance of informing themselves in re-
gard to modern views of pathology, and recommend
to them to procure the work before us as the best
means of obtaining this information.—Stethoscope.
  In offering the above titled work to the public, the
authors have not attempted to intrude new views on
their professional brethren, hut simply to lay before
them, what has long been wanted, an outline of the
present condition of pathological anatomy.  In this
they have been completely successful. The work is
one of the best compilations which  we have ever
perused.—Charleston Medical Journal and Review.
  We have no  hesitation in  recommending  it  as
worthy of careful and thorough study by every mem-
ber of the  profession, old or young.—N. W.  Med.
and Surg. Journal.
  From the casual examination we have given we
are inclined to regard it  as a text-book, plain, ra-
tional, and intelligible, such a book as the practical
man needs for daily reference.   For  this reason it
will die likely to be largely useful, as it suits  itself
to those busy men who have  little  time for minute
investigation, and prefer a summary to an elaborate
tieatise.—Buffalo Medical Journal.
                   KIRKES (WILLIAM  SENHOUSE),  M.D.,
               Demonstrator of Morbid Anatomy at St. Bartholomew's Hospital, &c.

A  MANUAL  OF  PHYSIOLOGY.   Second  American, from  the second  and
  improved  London edition.  With one  hundred and sixty-five illustrations.   In  one large and
  handsome royal 12mo. volume, leather,  pp. 550.  $2 00.
  In the present edition, the Manual of Physiology
has been brought up to the actual condition of the
science, and fully sustains the reputation which it
has already so deservedly attained.  We consider
the work of MM. Kirkes and Paget to constitute one
of the very best handbooks of Physiology we possess
—presenting just such an outline of the science, com-
prising an account of its leading facts and generally
admitted principles, as the student requires during
his attendance upon a course of lectures, or for re-
ference whilst preparing for examination.— Am.
Medical Journal.
  We need only say, that, without entering into dis-
cussions of unsettled  questions, it contains all the
recent improvements  in this department cf medical
science. For the student beginning this fc,udy, and
the practitioner who has but leisure to refresh his
memory, this book is invaluable, as it contains all
that it is important to know, without special details,
which are read with interest  only by those who
would make a specialty, or desire to possess a criti-
cal knowledge of the subject.—Charleston Medical
Journal.
  One of the best treatises that can be put into the
hands of the student.—London Medical Gazette.

  Particularly adapted to those who desire to pos-
sess a concise digest of the facts of Human Physi-
ology.—British and Foreign Med.-Chirurg. Review.
  We conscientiously recommend it as an admira-
ble "Handbook of Physiology."—London Journal
of Medicine.
KNAPP'S TECHNOLOGY ; or, Chemistry applied
  to the Arts and to Manufactures.  Edited, with
  numerous  Notes and  Additions, by Dr. Edmund
  Ronalds and Dr. Thomas  Richardson.  First
  American  edition, with Notes and Additions, by
  Prof. Walter R. Johnson.  In twe handsome
  octavo volumes, extra cloth, with about 500 wood-
  engravings.  $6 00.
LALLEMAND ON SPERMATORRHOEA. Trans-
  lated and edited by Henry J. McDougal.  In one
  volume, octavo, extra cloth, 320 pages. Second
  American edition.  $1 75.
                              LUDLOW (J.  L.l.  M. D.
A  MANUAL  OF  EXAMINATIONS  upon  Anatomy,  Physiology,  Surgery,
  Practice of Medicine, Obstetrics, Materia Medica, Pharmacy, and Therapeutics.  To  which is
  added a Medical Formulary.   Designed for Students of Medicine throughout the United States.
  Third ediiion, thoroughly revised and greatly extended and enlarged.  With over three hundred
  and fifty illustrations.  In one large and handsome royal 12mo. volume, leather, of  over 800
  closely printed pages   (Just Ready.)  $2  50.
  The great popularity of this volume, and the numerous demands for it during the two years in which
it has been out of print, have induced the author in its revision  to spare no pains to render it a
correct and accurate digest ofthe most recent condition of all the branches of medical science. In
many respects it may, therefore, be regarded rather as a new book than a new edition,  an entire
section on Physiology having been  added, as also  one on Organic Chemistry, and  many portions
having been rewritten.  A very complete series  of illustrations has been introduced, and every
care has been taken in the mechanical execution to render it a convenient and satisfactory book for
study or reference.                •
  The arrangement of the volume in the form of question and answer renders it especially suited
for the office examination of students and for those preparing for graduation.
                    LARDNER (DIONYSIUS),  D. C. L., &c.

HANDBOOKS   OF  NATURAL   PHILOSOPHY   AND   ASTRONOMY.
  Revised  with numerous Additions, by the American editor.  First Course, containing Mecha-
  nics  Hydrostatics, Hydraulics,  Pneumatics, Sound,  and Optics.  In one  large  royal  12mo.
  volume, of 750 pages, with 424 wood-cuts. $1 75.  Second Course, containing Heat, Electricity,
  Magnetism, and Galvanism, one volume, large royal 12mo., of 450 pages, with 250 illustrations.
  $1 25  Third Course (now ready), containing Meteorology and Astronomy, in one large volume,
  roval 12mo. of nearly eight hundred pages, with thirty-seven plates and two hundred wood-cuts.
  S2 00  The whole complete in three volumes, of about two thousand large pages, with over one
  thousand figures on steel and wood.  $5 00. Any volume sold separate, strongly bound in leather. 
AND SCIENTIFIC  PUBLICATIONS.
19
„„,                            LEHMANN  (C.  G.)
PHYSIOLOGICAL   CHEMISTRY.   Translated from  the  second  edition  hy
  ^T^ m  a BY\,M- D-' F- R" S- &c ' edi,ed by R" E-  Rogers, M. D., Professor of Chemistry
  FUke'fAU^of Pr^T1110^^  Un^rsity of Pennsylvania,'with  illustrations selecte^ffi
  ■nH ht«j         Physio ogtcal Chemistry, and an Appendix of plates.  Complete in two large

  SS   (NoTZ2d7!rmoTa cloth'containi,,g 120°p^es'wilh near'ytwo hund-d u™-
th JnrnfS Wor^'unive«a''v acknowledged as the most complete and  authoritative exposition of
PrX"n fe   d dC,ulls  °f Zoochemi*«T, in »* Parage through the  press, has received from
f ™„J «;i v, -8         °,aTe 8S.WaS ,,eces^ary t0 Present it in a correct and reliable form.  To such
IZTin el,10™ WrC,rf dTmed s"Pe,-flu»us= »ut several years having elapsed between the appear-
lltT  y  a th.e,firSt a"d la,^ V0IUme- the latter co»'ained a supplement, embodying nume-
rous corrections and additions resulting from the advance of ihe science.  These have all been incor-
Ph^nirtln VrGu''? l^lr aPPr°Prjat« P'acers; whi'e lh« subjects have been still further elucidated by
theinsertion of illustrations from the AtlasofDr.OttoFunke. With the view of supplying the student
with the means of convenient  comparison, a  large number of wood-cuts, from works on kindred
subjects, have also been added in the form of an Appendix of Plates.  The work is, therefore, pre-
sented as m every way worthy the attention  of all who desire to be familiar wilh the modern facts
and doctrines of Physiological Science.
  Already well known and appreciated by the scien-
tific  world, Professor  Lehmann's great work re-
quires no laudatory sentences, as, under a new garb,
it is  now presented to us.  The  little space at our
command would ill suffice to set forth even a small
portion of its excellences.  To all whose studies or
professional duties render the revelations of Physio-
logical Chemistry at once interesting and essential,
these volumes will be indispensable.  Highly com-
plimented by European reviewers, sought  for with
avidity by scholars of every nation, and admirably
written throughout, it is sure to win a welcome and
to be thoroughly studied.—Boston Med. and Surg.
Journal, Dec. 1855.
  The most important contribution as vet made to
Physiological Chemistry—Am. Journal  Med. Sci-
ences, Jan. 1856.
  The present volumes belong to the small class of
medical literature which comprises elaborate works
a(the highest orderof merit.—Montreal Med. Chron-
icle, Jan. 1856.
  The work of Lehmann stands unrivalled  as the
most comprehensive book of reference and informa-
tion extant on every branch of the subject on which
it treats.—Edinburgh  Monthly Journal of Medical
Science.
  All teachers must possess it, and  every intelligent
physician ou?ht todo likewise.—Southern Med. and
Surg. Journal, Dec. 1855.

                        BY the same author.   (Now Ready, 1856.)

MANUAL  OF CHEMICAL  PHYSIOLOGY.    Translated  from the  German,
  with Notes and Additions, by J. Cheston Morris, M. D., with an Introductory Essay on Vital
  Force, by Samuel Jackson, M. D., Professor of the Institutes of Medicine in  the University of
  Pennsylvania.  With illustrations on wood.   In  one very handsome octavo volume, extra c'oth,
  of 336 pages.  $2  25.

  The. original of this work, though  but lately issued  by its distinguished author, has already
assumed the highest  position, as  presenting in their latest development the modem  doctrines and
discoveries in the chemistry of life.  The numerous additions  by the translator, and the Introduc-
tion by Professor Jackson will render its physiological aspect more complete than designed  by the
author, and will adapt it for use as a text-book of physiology, presenting more thoroughly than has
yet been attempted, the modifications arising from the vast impulse which organic chemistry has
received within a few years past.

                          From Prof. Jackson's Introductory Essay.
  In adopting the handbook of Dr. Lehmann as a manual of Organic Chemistry  for the use of the
students of the University,  and in recommending his original work of Physiological Chemistry
for their more mature studies, the high value of his researches, and the great weight of his  autho-
rity in that important department of medical science are  fully recognized.
  The present volume  wiil be a very convenient one I densed  form,  the positive facts  of  Physiological
for students, as offering a brief epitome of the more Chemistry.—Am. Journal Med. Sciences, April, 1856.
elaborate work, and as  containing, in a  very eon- |
                          LAWRENCE (W.), F. R. S.,  &c.

A TREATISE   ON   DISEASES   OP  THE  EYE.   A   new edition,  edited,
  with numerous additions, and 243 illustrations, by Isaac Hays, M. D., Surgeon to Will's Hospi-
  tal, &c.  In one very large and handsome octavo volume, of 950 pages,  strongly bound in leather
  with raised bands.  $5 00.
  This work  is so universally recognized  as the standard authority on the subject, that the pub-
lishers in presenting this new edition have  only to remark  that in its preparation the editor  has
carefully revised  every  portion, introducing additions and  illustrations wherever the advance of
science has  rendered them  necessary or  desirable,  constituting  it a complete  and  thorough
exponent of  the most advanced state ofthe subject.
  This admirable treatise— the safest guide and moat
comprehensive work of reference, which is within
the reach of the profession.—Stethoscope.

  This standard  text-book on  the department  of
which it treats, has not been  superseded, by any or
all of the numerous publications on the subject
heretofore issued.  Nor with the multiplied improve-
ments of Dr. Hays, the American editor, is  it at all
lilcelv that this great work will cease to merit  the
confidence and preference of students or practition-
ers  Its  ample extent—nearly one thousand large
octavo pages—has enabled both author and editor to
do justice~to all the details of this subject, and con-
dense in this single volume the present state of our
knowledge of the whole science in this department,
whereby its practical value cannot be excelled.  We
heartily commend it, especially as a book of refer-
ence, indispensable  in every  medical library.  The
additions  of the American editor very greatly en-
hance the value ofthe work, exhibiting the learning
and experience of Dr. Hays, in the light in which he
ought to be held, as a standard authority on all sub-
jects appertaining to this specialty.— N. Y. Med. Gaz. 
20
BLANCHARD  &  LEA'S  MEDICAL
                            LA  ROCHE  (R.),  M. D.,  &c.
YELLOW FEVER, considered  in its  Historical, Pathological,  Etiological,  and
  Therapeutical Relations.  Including a Sketch of the Disease as it has occurred in Philadelphia
  from 1699 to 1854, with an examination of the connections between it and the fevers known under
  the same name in other parts of temperate as well as in tropical regions   In two large  and
  handsome octavo volumes of nearly 1500 pages, extra cloth.   (Just Ready.)  $7 00.
 From Professor S. H. Dickson, Charleston, S. C,
              September 18, 1855.
  A monument of intelligent and well applied re-
search, almost without example.  It is, indeed, in
itself, a large  library, and is destined to constitute
the special  resort as a book of reference, in the
Bubject of which it treats, to all future time.
  We have not time at present, engaged as we are,
by day and by night, in the work of combating this
very disease, now prevailing in our city, to do more
than give this cursory notice of what we consider
as undoubtedly the most  able and  erudite medical
publication our country has yet produced   But in
view of the startling fact, that this, the most malig-
nant and unmanageable disease of modern times,
has for  several years been prevailing in our country
to a greater extent than ever before;  that it  is no
longer confined to either large  or small cities, but
penetrates country villages, plantations, and farm-
houses; that it is treated  with  scarcely better suc-
cess now than thirty or forty years ago; that  there
is vast mischief done by ignorant pretenders to know-
ledge in regard to the disease, and in view of the pro-
bability that a majority of southern physicians will
be called upon to treat the disease, we trust that this
able and comprehensive treatise will he very gene-
rally read in the south.—Memphis Med. Recorder.
  This is decidedly the great American medical work
of the day—a full, complete, and systematic treatise,
unequalled by any other upon the all-important suh-
jectof Yellow Fever.  The laborious, indefatigable,
and learned  author has devoted to it many years of
arduous research and careful study, and the result
is such as will reflect the highest honor upon the
author and our country.—Southern Med. and Surg.
Journal.

  The genius and scholarship of this great physician
could not have  been  belter  employed than in the
erection of this towering monument to his own fame,
and to the glory of the medical literature of his own
country.  It is destined to remain the great  autho-
rity upon the subject of Yellow Fever.  The student
and physician will find in these volumes a rtsumi
ofthe sum total ofthe knowledge ofthe world upon
the awful scourge which they so elaborately discuss.
The style is so soft and so pure as to refresh and in-
vigorate the mind while absorbing  the thoughts of
the gifted author, while the publishers have suc-
ceeded in bringing the externals in to a most felicitous
harmony  with the inspiration  that dwells within.
Take it all in all, it is a book we have often dreamed
of, but  dreamed not that it would ever meet our
waking eye as a tangible reality.—Nashville Journal
of Medicine.
  We deem it fortunate that the splendid work of
Dr. La Roche should have been issued from the press
at this particular time.  The want of a reliable di-
gest of all that is known in relation to this frightful
malady has long been felt—a want very satisfactorily
met in the work before us.  We  deem it but faint
praise to say that Dr. La Rtche has succeeded in
presenting the profession with an able  and complete
monograph, one which will find its way into every
well ordered library.— Va. Stethoscope.
  Although we  have  no doubt that  controversial
treatises on the mode of origin and propagation of the
fever in question will, as heretofore,  occasionally
appear, yet it must be  some time before another sys-
tematic work can arise in the face  of so admirable
and carefully executed a one as the  present.  It is a
mine of information, quite an encyclopaedia of refer-
ences, and resume of knowledge relative to what has
been recorded upon the subject.—London Lancet.
  A miracle of industry and research, constituting
a complete library of reference  on the disease of
which it treats.—Dublin Quarterly  Journal.
                                    BY THE SAME AUTHOR.

PNEUMONIA;  its  Supposed Connection,  Pathological and Etiological,  with Au-
  tumnal Fevers, including an Inquiry into the Existence and Morbid Agency of Malaria.   In one
  handsome octavo volume, extra cloth, of 500 pages.  $3 00.
  A more simple, clear, and forcible exposition of I    Thiswork should becarefully studied by Southern
the groundless nature and dangerous  tendency of |  physicians, embodying as it does the reflections of
certain pathological and etiological heresies, has |  an original thinker and close observer on a subject
seldom been presented to our notice.—N. Y. Journal  peculiarly their own.— Virginia Med. and Surgical
of Medicine and Collateral Science.              \  Journal.
                   LAYCOCK  (THOMAS),  M. D.,  F. R. S. E.,
          Professor of Practical and Clinical Medicine in the University of Edinburgh, &c.

LECTURES  ON  THE  PRINCIPLES  AND  METHODS  OF  MEDICAL
  OBSERVATION AND RESEARCH.  For the Use of Advanced Students and  Junior  Prac-
  titioners.  In one very neat royal 12mo. volume, extra cloth.   Price $1  00.  (Now Ready.)
  Though addressed more particularly to the  student, this  little volume  will be found of much
use to all members of the profession who aim  at rendering their practice a science rather than  a
routine.  The importance of the development and application of principles, and  the exercise of
correct and logical reasoning from clinical observations are beginning to be generally recognized,
and in furtherance of this object, a wide circulation of the  present volume cannot fail to  exercise a
most beneficial influence.  The object and scope of the work may be gathered from the following
condensed summary of the contents :—
  Lecture 1.  General Principles of Observation and Inquiry—Nature  and Acquisition of Experi-
ence in Medicine—Combination  of Experience with Theory and Observation, with illustrations
of the Fallacious use of Theories.  Lect. II. General Methods and Objects of Clinical Study.
Lect. III. Methods of Clinical Examination—Clinical  Observations of General  or Constitutional
Morbid States. Lect. IV. On Prognosis, and the Order of Succession of Morbid Phenomena.  Lect.
V. On the Due Estimate of Treatment—Management ofthe  Case.  Lect. VI. Numerical Method
of Research in  Medicine.   Lect. VII. Analogical, Philosophical, or Purely Inductive  Method of
Research—Practical Examples of the  Conduct of an  Analogical Investigation—Examples  of its
Applications to Anatomy, Physiology,  and Histology.
                        MULLER (PROFESSOR  J.),  M. D.
PRINCIPLES OF  PHYSICS  AND   METEOROLOGY.  Edited, with  Addi-
  tions, by R. Eglesfeld Griffith, M. D.  In one large and handsome octavo volume, extra
  cloth, with 550 wood-cuts, and two colored plates, pp. 636.  $3 50. 
AND  SCIENTIFIC  PUBLICATIONS.
21
                          MEIGS (CHARLES  D.), M. D.,
             Professor of Obstetrics, &c. in the Jefferson Medical College, Philadelphia.

OBSTETRICS:  THE  SCIENCE AND  THE  ART.  Third  edition,  revised
  and improved.  With one hundred and twenty-nine illustrations. In one beautifullv printed octavo
  volume, leather, of seven hundred and fifty-two large pages.  $3 75. (Now Ready.)

  The rapid  demand for  another edition of this work is  a sufficient expression of the favorable
verdict of the profession.  In thus preparing it a third time for the press, the author has endeavored
to render it in every respect worthy of the favor which it has received.  To accomplish this he
has thoroughly revised it in every part.  Some portions have been rewritten, others added, new
illustrations have been in many instances substituted  for such as were not deemed satisfactory,
while, by an alteration in the typographical arrangement, the size of the work has not been increased,
and the price remains unaltered.  In its present improved form, it is,  therefore, hoped that the work
will continue to meet the wants of the American profession as a sound, practical, and extended
System of Midwifery.

                         by  the same  author.  (Lately Issued.)

WOMAN: HER  DISEASES AND THEIR  REMEDIES.   A Series of Lee-
  tures to his Class.   Third and Improved edition.  In one large and beautifully printed octavo
  volume, leather.     pp. 672.  $3 60.
  The gratifying appreciation of his labors, as evinced by the exhaustion of two large impressions
of this work within a few years, has not been lost upon the author, who has endeavored in every
way to render it worthy of the favor with which it  has been received.  The opportunity thus
afforded for a second revision has been improved, and the work is now presented as in every way
superior to its predecessors, additions  and  alterations having been made whenever the advance of
science has rendered them desirable.  The typographical execution of the work will also be found
to have undergone a similar improvement, and the work is  now confidently presented as in every
way worthy  the position it  has acquired as the standard American text-book on the Diseases of
Females.
  It contains a vast amount of practical knowledge,
by one who has accurately observed and retained
the experience of many years, and who tells  the re-
sult in a free, familiar, and pleasant manner.—Dub-
lin Quarterly Journal.
  There is an off-hand fervor, a glow, and a  warm-
heartedness infecting the effort of Dr. Meigs, which
is entirely captivating, and which absolutely hur-
ries the reader through from beginning to end. Be-
sides, the book  teems with solid instruction, and
it shows the very highest evidence of ability, viz.,
the clearness with which the information  is pre-
sented.  We know of no better test of one's under-
standing a subject than the evidence of the power
of lucidly explaining it.  The most elementary, as
well as the obscurest subjects, under the pencil of
Prof.  Meigs,  are isolated and made to stand out in
  The instructive and  interesting author  of this
work, whose previous labors in the department of
medicine which he  so  sedulously cultivates, have
placed his countrymen under deep and abiding obli-
gations, again challenges their admiration in  the
fresh and vigorous, attractive and racy pages before
us.  It is a delectable book. * *  * This treatise
upon child-bed fevers will have an extensive sale,
being destined, as it  deserves, to find a place in  the
library of every practitioner who scorns to lag in the
rear of his brethren.—Nashville Journal of Medi-
cine and Surgery.
such bold relief, as to produce distinct impressions
upon the mind and memory ofthe reader. — The
Charleston Med. Journal.
  Professor Meigs has enlarged and amended this
great work, for such it unquestionably is, having
passed the ordeal of criticism at home and abroad,
but been improved thereby ; for in  this new edition
the author has introduced real improvements, and
increased the  value and utility of  the book im-
measurably.  It  presents  so many novel, bright,
and sparkling thoughts;  such an exuberance of new
ideas on almost  every page, that we confess our-
selves to have become enamored  with the book
and its author; and cannot withhold our congratu-
lations from our Philadelphia confreres, that such a
teacher is in their service.—N. Y. Med. Gazette.
  This book will add more to his fame than either
of those which bear his name. Indeed we doubt
whether any material improvement will be made on
the teachings of this volume  for a century to come,
since it is so eminently practical, and based on pro-
found knowledge of the science and  consummate
skill  in the art of healing, and ratified  by an ample
and extensive experience, such as few men have the
industry or good fortune to  acquire.—N. Y. Med.
Gazette.
MALGAIGNE'S OPERATIVE SURGERY, based
  on  Normal and Pathological Anatomy.   Trans-
  lated from the French by Frederick Brittan,
  A. B.,M.D. With numerous illustrations on wood.
  Inone handsome octavo volume, extra cloth, of
  nearly six hundred pages.  $2 25.
                       BY THE SAME AUTHOR ;

A TREATISE ON ACUTE  AND CH
  OF THE UTERUS.  With  numerous plates,
  style of art.  In one handsome octavo volume, e

                                  BY THE SAM

OBSERVATIONS  ON   CERTAIN  0
  CHILDREN.   In one handsome octavo volume

MAYNE'S  DISPENSATORY   AND THERA-
  PEUTICAL  REMEMBRANCER.  Comprising
  the entire lists of Materia Medica. with every
  Practical Formula contained in  the three British
  Pharmacopoeias.  Edited, with the addition of the
  Formula;  of the U. S. Pharmacopoeia, by R. E.
  Griffith, M.D. 1 12mo. vol. ex. cl.,300pp. 75 c.
                       BY THE SAME AUTHOR J  WITH COLORED PLATES.

A TREATISE ON ACUTE  AND CHRONIC  DISEASES OF  THE  NECK
  OF THE UTERUS.  With  numerous plates, drawn  and colored from nature in the highest
  style of art.  In one handsome octavo volume, extra cloth.  $4 50.
                                  BY THE SAME AUTHOR.

OBSERVATIONS  ON   CERTAIN  OF  THE  DISEASES   OF  YOUNG
  CHILDREN.   In one handsome octavo volume, extra cloth, of 214 pages.   $175
                        BY the same author.  (Lately Published.)

ON  THE  NATURE,   SIGNS,   AND   TREATMENT  OF  CHILDBED
  FEVER.  In a Series of Letters addressed to the Students of his Class.  In one handsome
  octavo volume, extra cloth, ol 365 pages.  $2 50. 
22
BLANCHARD  &  LEA'S  MEDICAL
                        MACLISE (JOSEPH), SURGEON.

SURGICAL  ANATOMY.   Forming  one volume,  very large  imperial  quarto.
  With sixty-eight large and splendid Plates, drawn in the best style and beautifully colored. Con-
  taining one hundred and  ninety Figures, many of them the size of life.  Together with copious
  and explanatory letter-press.   Strongly  and handsomely bound in  extra cloth, being one of the
  cheapest and best executed Surgical works as yet issued in this country.  $11 00.

  %* The size of this work prevtnts its transmission through the post-office as a whole, but those
who desire to have  copies  forwarded by  mail, can receive them  in five parts, done  up in stout
wrappers.  Price $9 00.

  One of the greatest artistic  triumphs of the age
in Surgical Anatomy.—British American Medical
Journal.
  Too  much cannot be said in its praise;  indeed,
we have not language to  do it justice.—Ohio Medi-
cal and Surgical Journal.
  The most admirable surgical atlas we have seen.
To the practitioner deprived of demonstrative dis-
sections upon the human  subject, it is an invaluable
companion.—N. J. Medical Reporter.
  The  most accurately  engraved  and beautifully
colored  plates we have  ever seen in an American
book—one of the best and cheapest surgical works
ever published.—Buffalo Medical Journal
  It is very rare that so  elegantly printed,  so well
Illustrated, and so useful a  work, is  offered at so
moderate a price.—Charleston Medical  Journal.
  Its  plates can boast a superiority which places
them;almost, beyond the reach of competition.—Medi-
cal Examiner.
  Every practitioner, we think, should have  a work
of this kind within reach.—Southern  Medical and
Surgical Journal.
  No such lithographic illustrations of surgical re-
gions have  hitherto,  we think, been given.—Boston
Medical and Surgical Journal.
  As a surgical anatomist, Mr. Maclise has proba-
bly no superior.—British and Foreign Medico-Chi-
rurgical Review.

  Of great value to the student engaged  in dissect-
ing, and to the surgeon at a distance from the means
of keeping up his anatomical knowledge.—Medical
Times.
  The mechanical execution cannot be excelled.—
Transylvania Medical Journal.

  A work which has no parallel in point of accu-
racy and cheapness in the English language.—N. Y.
Journal of Medicine.
  To all engaged in  the study or  practice of their
profession, such a work is almost  indispensable.—
Dublin Quarterly Medical Journal.

  No practitioner whose means will admit  should
fail  to possess it.—Ranking's Abstract.

  Country practitioners will find these plates of im-
mense value.—iV. Y. Medical Gazette.
  We are extremely  gratified to announce to the
profession the completion of this truly magnificent
work, which, as a whole,  certainly stands unri-
valled, both for  accuracy of drawing,  beauty of
coloring,  and all the requisite explanations of the
subject in hand.—The  New Orleans Medical and
Surgical Journal.

  This is by far the ablest work on Surgical Ana-
tomy  that has come under our observation. We
know of no other work that would justify  a stu-
dent, in any degree, for neglect of actual dissec-
tion.  In  those  sudden emergencies that so often
arise, and which require the instantaneous command
of minute anatomical knowledge, a work of this kind
keeps the details of the dissecting-room perpetually
fresh in the memory.—The  Western Journal of Medi-
cine and Surgery.
   g^° The very low price at which  this work is furnished, and the beauty of its execution,
require an extended sale to compensate the publishers for the heavy expenses incurred.
      MOHR (FRANCIS)  PH.D., AND RED WOOD (TH EOPH I LUS).
PRACTICAL  PHARMACY.    Comprising the Arrangements,  Apparatus,  and
  Manipulations of the Pharmaceutical Shop  and Laboratory.  Edited, with extensive Additions,
  by  Prof. William Procter, of the Philadelphia  College  of Pharmacy.  In one  handsomely
  printed octavo volume, extra cloth, of 570 pages, with over 500 engravings on wood.  $2 75.
                             MACKENZIE  (W.),  M.D.,
                  Surgeon Oculist in Scotland in ordinary to Her Majesty, &c. &c.

A  PRACTICAL  TREATISE ON  DISEASES   AND INJURIES  OF  THE
  EYE.  To which is prefixed an Anatomical Introduction explanatory of a Horizontal Section ol
  the Human Eyeball, by Thomas  Wharton Jones, F. R. S.  From the Fourth Revised and En-
  larged London Edition.  With Notes and Additions by Addinell Hewson, M. D., Surgeon lo
  Wills Hospital, &c. &c.  In one very large and handsome octavo volume, leather, raised bands, with
  plates and numerous wood-cuts.   (Now Ready.)  $5 25.
  The treatise of Dr. Mackenzie indisputably holds
the first place, and forms, in respect of learning and
research, an Encyclopaedia unequalled in extent by
any other work of the kind, either English or foreign.
—Dixon on Diseases ofthe Eye.

  Few modern books on any department of medicine
or surgery have met with such extended circulation,
or have procured for their authors a like amount of
European celebrity.  The  immense research which
it displayed, the thorough acquaintance with the
subject, practically as well as theoretically, and the
able manner in which the author's stores of learning
and experience were rendered available for general
use, at once procured for the first edition, as well on
the continent as in this country, that high  position
as a standard work which each successive edition
has more firmly established, in spite of the attrac-
tions of several rivals of no mean ability.  This, the
fourth edition, has been in a great measure  re-writ-
ten ;  new matter, to the extent of one hundred and
Gfty pages,  has been added, and in several instances
formerly  expressed opinions have  been modified in
accordance with  the advances in the science which
have been made of late years.  Nothing worthy of
repetition upon any branch of the subject appears to
have escaped the author's notice.   We consider it
the duty of every one who has the love of his profes-
sion aud the welfare of his patient at heart, to make
himself familiar with this the most complete work
in the English language upon the diseases of the eye.
—Med. Times and Gazette.
  The fourth edition of this standard work will no
doubt be as fully appreciated as the three former edi-
tions.  It is unnecessary to say a word in its praise,
for the verdict has already been passed upon it by
the most competent judges, and " Mackenzie on the
Eye" has justly  obtained a  reputation which it is
no figure of speech to call world-wide.—British and
Foreign Medico-Chirurgical Review.
  This new edition of Dr. Mackenzie's celebrated
treatise on diseases of the eye, is truly a miracle of
industry and learning.  We  need scarcely say that
he has entirely exhausted the subject of his specialty,
—Dublin Quarterly Journal. 
AND SCIENTIFIC  PUBLICATIONS.
23
                           MILLER  (JAMES), F. R. S. E.,
                      Professor of Surgery in the University of Edinburgh, &c.

PRINCIPLES  OF  SURGERY.   Fourth American, from  the  third and  revised
  Edinburgh edition.  In one large and  very beautiful  volume, leather, of 700 pages, with  two
  hundred and forty exquisite illustrations on wood.   (Now Ready, 1856.)    $3 75.
  The extended reputation enjoyed by this work will be fully  maintained  by the  present edition.
Thoroughly revised by the author, it will be found a clear and compendious exposition of surgical
science in its most advanced condition.
  In connection with the recently issued third edition  ofthe  author's " Practice of Surgery," it
forms a very complete system of Surgery in all its branches.
                                                fall behind that great work in soundness of princi-
                                                ple or depth of reasoning and research.  No physi-
                                                cian who values his reputation, or seeks the interests
                                                of his  clients,  can acquit himself before his God and
                                                the world without making himself familiar with the
                                                sound and philosophical views developed in the fore-
                                                going  book.—New Orleans Med. and Surg. Journal.
                                                  Without doubt the ablest exposition of the  prin-
                                                ciples of that branch of the healing art in any lan-
                                                guage.  This opinion, deliberately formed after a
                                                careful study of the first edition, we have had  no
                                                cause to change on examining the second.   This
                                                edition hns undergone  thorough revision by the au-
                                                thor;  many expressions have been modified,  and a
                                                mass  of new matter introduced. The book is got up
                                                in the finest style,and is an evidence of the progress
                                                of typography in our country.—Charleston Medical
                                                Journal and Review.
                                                   We recommend it to both student and practitioner,
                                                feeling assured that, as it now comes to us, it pre-
                                                sents  the most satisfactory exposition of the modern
                                                doctrines ofthe principles of surgery to be found in
                                                any volume in any language.—N. Y. Journal  of
                                                Medicine.
  The work of Mr. Miller is too well and too favor-
ably known among us, as one of our best text-books,
to render any further notice of it necessary than the
nnnouneement of a new edition, the fourth in our
country, a proof of its extensive circulation arann»
us.  As a concise and reliable exposition of the sci-
ence of modern surgery, it stands deservedly high—
we know not its superior.—Boston Med. and Surg.
Journal.
  The works of Professor Miller are so well known
to the profession, that it is unnecessary for us say
anything in relation to their general  merits.   The
present edition of his "Principles," however, de
serves a special  notice, from the number, variety,
and faithfulness of its illustrations.  The wood-cuts
are beautifully executed, and many of them are new
and exceedingly instructive, particularly those illus-
trating mortification, diseased and fractured bones,
and the varieties of aneurism.—Western Lancet.
  This edition is far superior, both in the abundance
and quality of its material, to any of the preceding.
We hope it will be extensively read, and the sound
principles which are herein taught treasured up for
future application.   The work  takes  rank with
Watson's Practice of Physic; it certainly does not
                         by the same  author.  (Lately Published.)

THE  PRACTICE  OF  SURGERY.   Third  American  from  the  second  Edin-
  burgh edition.   Edited, with Additions,  by F. W. Sargent, M. D , one ofthe Surgeons to Will's
  Hospital, &c.   Illustrated by three hundred and nineteen engravings on wood.   In one large
  octavo volume, leather, of over  700 pages.  $3  "7-
  No encomium of ours could add to the popularity
of Miller's Surgery.  Its  reputation  in this country
is unsurpassed by that of any other work, and, when
taken in connection with the author's Principles of
Surgery, constitutes a whole, without reference to
which no conscientisus surgeon would be willing
to practice his art.  The additions, by Dr. Sargent,
have materially enhanced  the value of the work.—
Southern Medical and Surgical Journal.
 It is seldom that two volumes have ever made so
profound an  impression in so short  a time as the
"Principles" and the " Practice" of Surgery  by
Mr. Miller—or so richly merited the reputation they
have acquired.  The author is an eminently sensi-
ble, practical, and well-informed man, who knows
exactly what he is talking  about and exactly how to
talk it.—Kentucky Medical Recorder.
 By the almost unanimous voice of the profession,
his works, both on the principles and  practice of
surgery have been assigned the highest rank.  If we
were limited to but one work on  surgery, that one
should be Miller's, as we regard it as superior to all
others.—St. Louis Med. and Surg. Journal.
  The author, distinguished alike ns a practitioner
and writer, has in this and his " Principles,  pre-
sented to the profession one of the most complete and
reliable systems  of Surgery  extant. His style of
writing is original, impressive, and engaging, ener-
getic, concise, and lucid.  Few have the faculty ot
condensing  so much in small space, and  at the same
time so persistently holding the attention;  indeed,
he appears to make the very process of condensation
a means of eliminating attractions.  Whether as a
text-book for students or a  book  of reference for
practitioners, it cannot be too strongly recommend-
ed —Southern Journal of Med. and Phys. Sciences.
              MONTGOMERY (W.  F.l,  M.  D.,  M. R.  I. A., Ac,
        Professor of Midwifery in the King and Queen's College of Physicians in Ireland, &c.

AN EXPOSITION OF THE SIGNS AND  SYMPTOMS  OF  PREGNANCY
  With some other Papers on Subjects connected with Midwifery.   From the second and ,enlarged
  English edition.  With two  exquisite colored plates, and numerous wood-cuts.   In  one very
  handsome octavo volume, extra cloth, of nearly 600 pages.  (Just Ready.)  S3 7o.
  The  orient edition of this classical volume is fairly entitled to be regarded as a new wo^ ^ ery


size.   Translated into various  languages, and .y'versally ^^^fyrm^my maintain its
numerous interesting questions discussed, it will ^, ^"^'"^.^^^Jf™ i°m ^in^ every point
high character, the author having exhausted  thef^. nnsa'i,5,ted by &-' own long and enlarged
wfth all the aid furnished by t^srece^                                        ofthe topic,

experience   Ihe t. le^o J ™JX^,Pn«r'wnh  the exception ofthe operative  procedures of m,d-
brought under consderation ,em   ™»thWobstetrjes, ei her directiy or* incidentally ;  and there are
wifery.amos.everyUu^                      ^ ^     X           t    t  and value  in





  In ever) jjuhii
from the American press. 
24
BLANCHARD  & LEA'S  MEDICAL
                               NEILL  (JOHN),  M. D.,
                         Surgeon to the Pennsylvania Hospital, &c; and

                      FRANCIS  GURNEY SMITH,  M.D.,
              Professor of Institutes of Medicine in the Pennsylvania Medical College.

AN  ANALYTICAL  COMPENDIUM  OF   THE   VARIOUS  BRANCHES
  OF MEDICAL SCIENCE ; for the Use and Examination of Students.   A new edition, revised
  nnd improved.  In one very large  and handsomely  printed royal 12mo. volume, of about one
  thousand pages, with three hundred and seventy-four illustrations on wood.   Strongly bound in
  leather, with raised bands.   (Now Ready, 1855.)  $3  00.
  The very flattering reception which has been accorded to this work, and the high estimate placed
upon it by the profession, as evinced by the constant and increasing demand which has rapidly ex-
hausted two large editions, have stimulated the authors to render the volume in its present revision
more worthy of the success which has attended it.  It has accordingly been thoroughly examined,
and such errors as had on former occasions escaped observation have been corrected, and whatever
additions were necessary to maintain it on a level with the advance of science have been introduced.
The extended series of illustrations has been still further increased and much improved, while, by
a slight enlargement ofthe page, these various additions have been incorporated without increasing
the bulk of the volume.
  The work is, therefore, again presented as eminently worthy of the favor with which it has hitherto
been received.  As a book for daily reference by the student requiring a guide to his more elaborate
text-books, as a manual for preceptors  desiring to stimulate their  students by frequent and accurate
examination,  or as a source from which the practitioners of older date may easily and cheaply acquire
a knowledge ofthe changes and improvement in professional science,  its reputation is permanently
established.
  In the rapid course of lectures, where work for
the students is heavy, and review necessary for an
examination, a compend  is not only valuable, but
it is almost a sine qua non. The one before us is,
in most of  the divisions, the most unexceptionable
of all books of the kind  that we know  of.  The
newest and soundest doctrines and the  latest  im-
provements and discoveries are  explicitly,  though
concisely,  laid before the student.  Of course it is
useless for us to  recommend it  to all last course
students, but  there is a  class to whom we  very
sincerely commend this cheap book as worth its
weight in  silver — that class is  the graduates in
medicine of more  than ten years'  standing,  who
have not studied medicine  since.  They will perhaps
find out from it that the science is not exactly now
what it was when they left it off.—The Stethoscope.
  AVe recommend it to our readers as the best ■work
of the kind with which we are acquainted.—Med.
Examiner, April, 1856.
  Having made free use of  this volume in our ex-
aminations of pupils, we can  speak from experi-
ence in recommending it as an admirable compend
for students,  and as especially useful to preceptors
who examine their pupils.   It will save the teacher
much  labor by enabling him readily to recall all of
the points upon which  his pupils  should  be ex-
amined. A work of this sort should be in the hands
of every one who takes pupils into his office with a
view of examining them; and this is unquestionably
the best of its class.—Transylvania Med. Journal.
                               NEILL  (JOHN),   M.  D.,
                  Professor of Surgery in the Pennsylvania Medical College, &c.
OUTLINES OF THE VEINS AND LYMPHATICS.   With  handsome colored
  plates.  1 vol., cloth. $1  25.

OUTLINES OF THE  NERVES.    With handsome plates.   1 vol., cloth.  $1  25.
                NELIGAN (J.  MOORE),  M. D., M. R. I. A., &.C.
                             (A splendid work.  Now Ready.)

ATLAS OF  CUTANEOUS DISEASES.   In one  beautiful quarto volume, extra
  cloth, with splendid colored plates, presenting nearly one hundred elaborate representations  of
  disease.  $4 50.

  This beautiful volume is intended as a complete and accurate representation of all the varieties
of Diseases of the Skin.  While it can be consulted in conjunction with any work on Practice, it has
especial reference to the author's " Treatise on Diseases of the Skin," so favorably received by the
profession some  years since.  The publishers feel justified in saying that no  more beautifully exe-
cuted plates have ever been presented to the profession of this country.
  The diagnosis of eruptive disease, however, under
all circumstances, is very difficult.  Nevertheless
Dr. Neligan  has  certainly, "as far as possible,"
given a faithful and accurate representation of this
class of diseases, and there can be no doubt that
these plates will be of great use to the  student and
practitioner in drawing a diagnosis as to the class,
order, and species to which the particular case may
belong.  While looking over the " Atlas" we have
been induced to examine also the " Practical  Trea-
tise," and we are inclined to consider it a  very su-
perior work, combining accurate verbal  description,
with sound views of the pathology and treatment of
eruptive diseases.—Glasgow Med. Journal.
  The profession owes its thanks to the publishers of
Neligan's Atlas of Cutaneous Diseases, for they have
                                   BY THE SAME AUTHOR
placed within its reach and at a moderate cost a most
accurate and well delineated series of plates illus-
trating the eruptive disorders.   These plates are all
drawn from the life, and in many of them the daguer-
reotype has been employed with great success. Such
works as these are especially.useful to country prac-
titioners, who have not an opportunity of seeing the
rarer forms of cutaneous disease, and hence need the
aid of illustrations to give them the requisite infor-
mation on the  subject.  With these  plates at hand,
the inexperienced practitioner is'enabled to discri-
minate with much accuracy, and he is thus, com-
paratively speaking, put on an equal  footing with
those who have had the opportunity of visiting the
large hospitals of Europe and America.—Pa. Med.
Journal, June, 1856.
A  PRACTICAL  TREATISE  ON  DISEASES  OF  THE  SKIN.
  neat royal 12mo. volume, extra cloth, of 334 pages.  $1 00.

   fl@~ The two volumes will be sent by mail on receipt of Five Dollars.
In  one
OWEN ON  THE DIFFERENT  FORMS OF
  THE SKELETON,  AND OF  THE TEETH.
One vol. royal 12mo., extra cloth, with numerous
illustrations.  (Just Issued.)  $1 25. 
AiiD SCIENTIFIC PUBLICATIONS.
25
                                      (Now Complete.)
             PEREIRA (JONATHAN), M. D., F. R. S., AND L.  S.
THE  ELEMENTS  OF  MATERIA   MEDICA   AND  THERAPEUTICS.
  Third American edition, enlarged and improved  by the author;  including Notices  of most of the
  Medicinal Substances in use in the civilized world, and forming an Encyclopaedia of Materia
  Medica.  Edited, with Additions, by Joseph Carson, M. D., Professor of Materia Medica and
  Pharmacy in the University of Pennsylvania.  In two very large octavo volumes of 2100 pages,
  on small tvpe, with about  500 illustrations on stone and wood, strongly bound in leather, with
  raised bands.  $9 00.
  Gentlemen who have the first volume  are recommended to complete their copies  without delay.
The first volume will no longer be sold separate.   Price of Vol. II. $5 00.
  When we remember that Philology, Natural His-
tory, Botany, Chemistry, Physics, and the Micro-
scope, are ail brought forward to elucidate the sub-
ject, one cannot fail  to see that the reader has here
a work worthy of the name of an encyclopaedia of
Materia Medica.  Our own opinion of its  merits is
that of its editors, and also that of the whole profes-
sion, both of this and foreign countries—namely,
" that in copiousness of details, in extent, variety,
and accuracy of information, and in lucid explana-
tion of difficult and recondite subjects, it surpasses
all other works on  Materia Medica  hitherto pub-
lished."  We cannot  close this notice without  allud-
ing to the special  additions of the American editor,
which pertain to  the prominent vegetable produc-
tions of this country, and to the  directions of  the
United States Pharmacopoeia, in connection with all
the articles contained in the volume which are re-
ferred toby it. The illustrations have been increased,
and this edition by  Dr. Carson cannot well be re-
garded in any other light than that of a treasure
which should be found in the library of every physi-
cian.—New York Journal of Medical and Collateral
Science.
  The third edition of his " Elements of Materia
Medica, although completed under the supervision of
others, is by far  the most elaborate treatise in the
English language, and will, while medical literature
is cherished, continue  a monument alike honorable
to his  genius, as to his  learning and industry.—
American Journal of Pharmacy.
  The work, in  its present shape, forms the  most
comprehensive  and  complete treatise  on  materia
medica  extant  in  the English language. — Dr.
Pereira has been at great pains to introduce into
his work, not  only  all  the information on the
natural, chemical, and commercial history of medi-
cines, which might be serviceable to the physician
and surgeon, but whatever might enable his read-
ers to understand thoroughly the mode of prepar-
ing and manufacturing various articles employed
either for preparing medicines, or for certain pur-
poses in  the arts connected with  materia medica
and the practice of medicine.  The accounts of the
physiological and therapeutic effects of remedies are
given with great clearness and  accuracy,  and in a
manner calculated to interest as well as instruct the
reader.—Edinburgh Medical and Surgical Journal.
                             PEASELEE (E.  R.),  M.  D.,
                 Professor of Anatomy and Physiology in Dartmouth College, &c.

HUMAN HISTOLOGY, in its  applications to Physiology and General Pathology;
  designed as a Text-Book for Medical Students.  With numerous illustrations.  In  one handsome
  royal 12mo. volume.  (Preparing.)
  The subject of this work is one, the  growing importance of which, as the basis of Anatomy and
Physiology, demands for  it a separate volume.  The book will  therefore supply an  acknowledged
deficiency'in medical text-books, while the name ofthe author, and his experience as a teacher for
the last thirteen years, is a guarantee that it will be thoroughly adapted to the use ofthe student.

                         PIRRIE  (WILLIAM),  F.  R.  S. E.,
                      Professor of Surgery in the University of Aberdeen.

THE  PRINCIPLES  AND  PRACTICE  OF  SURGERY.   Edited by John
  Neill  M. D. Professor of Surgery  in the Penna.  Medical College, Surgeon tothe Pennsylvania
  Hospital, ice''in one very handsome octavo volume, leather, of 780 pages, with 316 illustrations.
  $3 75.
                                              arrived.  Prof. Pirrie, in the work before us,  has
                                              elaborately discussed the principles  of surgery,  and
                                              a safe and effectual  practice predicated upon them.
                                              Perhaps no work upon this subject heretofore issued
                                              is  so full  upon the  science of the art of surgery.—
                                              Nashville Journal of Medicine and Surgery.
                                                One of the best treatises on surgery in the English
                                              language.—Canada Med. Journal.
                                                Our impression is, that, as a manual for students,
                                              Pirrie's is the best work extant.— Western Med. and
                                              Surg. Journal.
  We know of no other surgical work of a reason-
able size, wherein there is so much theory and prac-
tice, or where subjects are more soundly or clearly
taught.—The  Stethoscope.
  There  is scarcely a disease of the bones or soft
parts, fracture, or dislocation, that is not illustrated
by accurate wood-engravings.  Then, again, every
instrument employed by the surgeon is thus repre-
sented.  These engravings are not only correct, but
really beautiful, showing the astonishing degree of
perfection to which  the art of wood-engraving  has

                               PANCOAST (J.), M. D.,
              Professor of Anatomy in the Jefferson Medical College, Philadelphia, &c.

OPERATIVE  SURGERY;  or, A Description and  Demonstration of the various
  Pmces.es of  the Art; including all the  New Operations, and  exhibiting the State of Surgical
  Science in its present advanced  condition.  Complete in  one royal  4to. volume, extra cloth, of
  380  pages  of"letter-press description and eighty large 4to. plates, comprising 486 illustrations.
  Second edition, improved.
$10 00.
of its kind it has no superior.—N. Y. Journal of
Medicine.
  Ti,rr«^llent work is constructed on the model | cerned, we are proud as an American to say that,
•f theFrench Surgical Works by Velpeau and Mai-
Signed Sd, wfagr as the English languag^con-_

                              PARKER  (LANGSTON),
                         Surgeon to the Queen's Hospital, Birmingham.

titp MODERN  TREATMENT OF SYPHILITIC DISEASES, BOTH PRI-
1 *lXi l   irJr atrrnNTlARY-  comprising the Treatment of Constitutional and Confirmed Syphi-
  MARY AND &~^!.essful method.  With numerous Cases, Formulae, and Clinical Observa-
  lis, by  a sale ana -        , entirely  rewritten London edition.  In  one neat octavo volume,

  SCiclStrafS^piii   ^st Issued,  $175. 
26
BLANCHARD  &  LEA'S  MEDICAL
                                PARRISH  (EDWARD),
  Lecturer on Practical Pharmacy and Materia Medica in the Pennsylvania Academy of Medicine, Ae.

AN INTRODUCTION  TO PRACTICAL PHARMACY.   Designed as a Text-
  Book for the Student, and as a Guide for the Physician  and Pharmaceutist.   With many For-
  mulae and Prescriptions.  In one handsome octavo volume, extra cloth, of 550 pages, wilh 243
  Illustrations. (Just Issued.) $2 75.
  A careful examination of this work enables us to
speak of it in  the highest  terms, as being the best
treatise on practical pharmacy with which we are
acquainted, and an invaluable vade-mecum, not only
to the apothecary and to those practitioners who are
accustomed to prepare  their own medicines, but  to
every medical man and medical student.  Through-
out the work are interspersed valuable tables, useful
formula?, and practical hints, and the whole is illus-
trated by a large number of excellent wood-engrav-
ings.—Boston Med. and Surg. Journal.
  This is altogether one ofthe most useful books we
have seen.  It is just what we have long felt to be
needed by apothecaries, students, and practitioners
of medicine, most of whom in this country have  to
put up their own prescriptions. It bears, upon every
page, the impress of practical knowledge, conveyed
in a plain common sense manner, and adapted to the
comprehension of all who may  read it.  No detail
has been  omitted, however trivial it may seem, al-
though really important to the dispenser of medicine.
—Southern Med. and Surg. Journal.
  To both the country practitioner and the city apo-
thecary this work of Mr. Parrish is a godsend.  A
careful study of  its contents will give  the young
graduate a familiarity with the value and mode  of
administering his prescriptions, which will be of  as
much use to  his patient as  to himself.— Va. Med.
Journal.
  Mr. Parrish has rendered a very acceptable service
to the practitioner and student,  by furnishing this
book, which contains the leading facts and principles
of the science of Pharmacy, conveniently arranged
for study, and with special reference to those features
of the subject which possess an especial practical in-
terest to the physician.  It furnishes the student, at
the commencement of his studies, with that infor-
mation which is  of the greatest importance in ini-
tiating him into the domain of Chemistry and Materia

                                 RICORD (

A TREATISE ON THE  VENEREAL
  With copious  Additions, by Ph. Ricord, M. D.
  M. D.  In one handsome octavo volume, extra
  Every  one will recognize the  attractiveness and
value which this work  derives from thus  presenting
the opinions of these two masters side by side.  But,
it must be admitted, what has made the  fortune  of
the book, is the fact that it  contains the " most com-
plete embodiment of the veritable doctrines of the
Hopital du Midi," which has ever been msde public.
The doctrinal ideas of M. Ricord. ideas which, if not
universally adopted, are incoutesiably dominant, have
heretofore only been interpreted by more or less skilful

                                   BY THE SAME AUTHOR
ILLUSTRATIONS OF SYPHILITIC DISEASE.
  Translated by Thomas F. Betton, M. D.  With
  fifty large quarto colored  plates.  In one large
  quarto volume, extra cloth.  $15 00.
Medica; it familiarizes him with the compounding
of drugs, and supplies those minutiae which but few
practitioners can impart.  The junior practitioner
will, also, find this volume replete with instruction.
—Charleston Med. Journal and Review, Mar. 1856.
  There is no useful information in the details of the
apothecary's or country physician's office conducted
according to science  that is omitted. The  young
physician will find it an encyclopedia of indispensa-
ble medical  knowledge, from the purchase of a spa-
tula to the  compounding  of  the most learned pre-
scriptions.  The woi k is by theablest pharmaceutist
in the  United States, and must meet with an im-
mense sale.—Nashville Journal of Medicine, April,
1856.
  We are glad  to receive this excellent  work.   It
will supply  a want long felt  by the profession, and
especially by  the  student of Pharmacy.  A large
majority of physicians are obliged to compound
their own medicines, and to them a work of this
kind is indispensable.—N. O. Medical and Surgical
Journal.
  We cannot say but that this volume is one  of the
most welcome and appropriate which has for a long
time been issued from the press.  It isa work which
we doubt not will at once secure an extensive cir-
culation, as it is designed not only for the druggist
and pharmaceutist, but also for  the great body  of
practitioners throughout the country, who not only
have to prescribe medicines, but in the majority of
instances have to rely upon their own resources—
whatever these may be—not only to compound, but
also  to manufacture  the remedies  they are  called
upon to administer.  The author has not  mistaken
the idea in  writing this volume, as it is alike useful
and invaluable to those engaged in the active pur-
suits ofthe  profession, and to those preparing to en-
ter upon the field of professional labors.—American
Lancet, March 24, 1856.
P.), M. D.,
DISEASE.  By John Hunter, F. R. S.
  Edited, with Notes, by Freeman J. Bumstead,
cloth, of 520 pages, wilh plates.   $3 25.
 secretaries, sometimes accredited and sometimes not.
   In the notes to Hunter, the master substitutes him-
 self for his interpreters, and gives his original I bought?
 to the world in a lucid and perfectly intelligible man-
 ner.  In conclusion we can say that  this is  incon-
 lestably the best treatise on syphilis with which we
 are acquainted, and, as we do not often  employ the
 phrase, we may be excused for expressing the hope
 that it may find a place in the library of every phy-
 sician.— Virginia Med. and Surg. Journal.
LETTERS ON SYPHILIS, addressed to the Chiet
  Editor of the Union Medieale.  Translated by W.
  P.  Lattimoee, M. D.  In one neat octavo vol-
  ume, of 270 pages, extra cloth.  $2 00.
                            RIGBY  (EDWARD),  M.D.,
                     Senior Physician to the General Lying-in Hospital, &c.

A  SYSTEM  OF  MIDWIFERY.   With  Notes and  Additional Illustrations.
  Second American Edition.  One volume octavo, extra cloth, 422 pages.   $2 50.

                           BY THE SAME AUTHOR.   (Now Ready.

ON  THE  CONSTITUTIONAL  TREATMENT  OF  FEMALE DISEASES.
  In one neat royal 12mo. volume, extra cloth, of about 250 pages.   $1 00.  Now Ready.
  The following condensed summary of the contents will show the topics treated in this little
volume.  The aim of the author has been throughout to present sound practical  views of the im-
portant subjects under consideration ; and without entering into theoretical disputations and disqui-
sitions to embody the results of his long  and extended experience in such a condensed  form  as
would be easily accessible to the practitioner.
Chapter  I.  Amenorrhcea.—II. Dysmenorrhoea.—III. Menorrhagia.—IV. Uterine  and  Vaginal
  Discharges.—V. Inflammation of the Os and Cervix.—VI. Ulceration of the Os and Cervix.—
  VII. Displacement ofthe Uterus.—VIII.  Retroversion.—IX. Anteversion.—X. Prolapsus Vesicae.
  —XI. Prolapsus Uteri.—XII. Fibrous Tumor  of the Uterus.—XIII. Malignant  Disease of the
  Uterus.—XIV.—Cauliflower  Excrescence of the Os.—XV.  Corroding Ulcer  of the Os.—XVI.
  Pruritus Pudendi.—XVII. Vascular Tumor of Orifice of Urethra.—XVIII. Ovarian Affections.
  —XIX.  Displacement of the Ovary.—XX. Ovarian Tumors. 
Anjj  BUlliJMTlFIC PUBLICATIONS.
27
mTTT1                RAMSBOTHAM (FRANCIS  H.),  M.D.

T5Sr tSIvNCIPLES AND  PRACTICE  OF  OBSTETRIC  MEDICINE AND
  bURU.fc.KY  in reference to the Process of Parturition.  A new and enlarged edition, thoroughly
  revised  by the Author.   With Additions by W. V. Keating, M. D.  In one large and handsome
  imperial octavo volume, of 650 pages, strongly bound in leather, with raised bands; wilh sixty-
  lour Deautiiul Plates, and numerous Wood-cuts in the  text, containing in all nearly two hundred
  large and beautiful figures. (Lately Issued, 1856.) $5 00.
  In calling the attention of the profession to the new edition of this standard work, the publishers
would remark that  no efforts have been spared to secure  for it a continuance  and extension  of the
remarkable favor with which it has been received.  The last London issue, which was considera-
bly enlarged, has received a further revision from the author, especially for this country.  Its pas-
gage through the press here has been  supervised by Dr. Keating, who has made numerous addi-
tions with a view  of presenting more fully whatever was necessary to  adapt  it thoroughly to
American modes of practice.  In its mechanical  execution, a like superiority over former editions
will be found.
                            From Prof. Hodge, of the University of Pa.
  To the  American public, it is most valuable, from its  intrinsic  undoubted excellence, and as being
the best authorized exponent of British Midwifery.  Its circulation will, I trust, be extensive throughout
our country.                                                                             °
  The publishers have shown  their appreciation of j cine  and  Surgery  to  our  library, and confidently
the merits of this work and secured its success by  recommend it  to our  readers, with  the assurance
the truly elegant style in which they have brought | that  it will not disappoint their most sanguine ex-
                                                pectations.—Western Lancet.
                                                 It is unnecessary to say anything in regard to the
                                                utility of this work.  It is already appreciated in our
                                                country for the value of the matter, the clearness of
                                                its style, and the fulness of its illustrations.  To the
it out, excelling themselves in  its production, espe
cially in its plates.  It is dedicated to Prof. Meigs,
and has the emphatic endorsement of  Prof. Hodge,
as the  best exponent  of British Midwifery.  We
know of no text-book which deserves in all respects
to be more highly recommended to students, and we ' "h8,.8_?c *'?™u "J"1»?':" '  SJ'^[atl<Ti  ™ T
could wish to see it in the hands of every practitioner, I S./^s »   xPh not  ?r„mPwh^  I     S  ? .
r  .i.     -ii r  i •.     i   i i  c     c        tt .' i student as a text-oooK, trom which to extract the
for they will find it invaluable for  reference.—Med.  mi,teri-il f..r ln-i™ .!,„ f„„„H.>n„„ „c. „ CAU"V1, ",c
„    '                                         material tor laying tne foundation of an education on
Gazette
  But once in a long time some brilliant genius rears
his head above the  horizon of science, and illumi-
nates and purifies every department that he investi-
gates ; and his works become types, by which innu-
merable  imitators model  their feeble  productions.
Such a genius we find in the younger Ramsbotham,
and such a type we find in the work now before us.
The binding, paper,  type, the engravings and wood-
cuts are all so excellent as to make this book one of
the finest specimens of the art of printing that have
given such  a world-wide reputation to  its enter-
prising and liberal publishers.   We welcome Rams-
obstetrical science, it has no superior__Ohio Med.
and Surg. Journal.

  We will only add that the student will learn from
it all he need to know, and the practitioner will find
it, as a book of reference, surpassed by none other.—
Stethoscope.
  The character and merits of Dr. Ramsbotham's
work are so well known and thoroughly established,
that comment is unnecessary and praise superfluous.
The illustrations, which are numerous and accurate,
are executed in the highest style of art.  We cannot
too highly recommend the work to our readers.—St.
botham's Principles and Practice of Obstetric Medi- i Louis Med  and Surg. Journal.
                           ROKITANSKY (CARD,  M.D.,
     Curator of the Imperial Pathological Museum, and Professor at the University of Vienna, &c.

 A   MANUAL  OF PATHOLOGICAL  ANATOMY.   Four  volumes,  octavo,
  bound in two, extra cloth, of about 1200 pages.  (Now Ready.)   $5 50
 Vol. I.—Manual of General Pathological Anatomy.  Translated by W. E. Swaine.
 Vol. II.—Pathological Anatomy of the Abdominal Viscera.  Translated by Edward  Sieveking,
     M. D.
 Vol. III.—Pathological Anatomy ofthe Bones, Cartilages, Muscles, and Skin, Cellular  and Fibrous
     Tissue, Serous and Mucous Membrane, and Nervous System.  Translated by C. H. Moore.
 Vol. IV.—Pathological Anatomy of the Organs of Respiration and Circulation.  Translated by G.
     E. Day.
^To render this large  and important work  more easy of reference, and at the same time  less cum-
  brous and costly, the four volumes have been arranged in two, retaining, however, the separate
  paging-, &c.
  The publishers feel much pleasure in presenting to the profession of the United  States the great
 work of Prof. Rokitansky, which is universally referred to as the standard of authority by the pa-
 thologists of  all nations.   Under  the auspices of the Sydenham Society of London, the combined
 labor of four translators has at length overcome the almost insuperable difficulties which have so
 long prevented the  appearance of the  work in an English dress, while the  additions made from
 various papers and essays ofthe author present his views on all the topics embraced, in their latest
 published form.  To a work so widely known, eulogy is unnecessary, and the publishers would
 merely state  lhat it is said to contain the results of not less than thirty thousand post-mortem
 examinations made  by the  author, diligently compared, generalized, and wrought  into one com-
 plete and harmonious system.
                                               | so charged his  text with valuable truths, that any
                                                attempt of a reviewer to epitomize is at once para-
                                                lyzed, and must end in a failure.— Western Lancet.
                                                  As this is the highest source of knowledge upon
                                                the important subject of which  it  treats, no  real
                                                student can afford to be without it.  The American
                                                publishers have entitled themselves to the thanks of
                                                the profession of their country, for this timeous and
                                                beautiful edition.—Nashville Journal of Medicine.
                                                  As a book of reference, therefore, this work must
                                                prove of inestimable value, and we cannot too highly
                                                recommend it to  the  profession.— Charleston Med.
                                                Journal and Review, Jan. 1856.
  The profession is too well acquainted with the re-
nutation of Rokitansky's work to need our assur-
ance that this is one of the most profound, thorough,
and valuable books ever issued  from the medical
Dress  It is sui generis, and has no standard of com-
parison.  It is only necessary, to announce that it is
issued in a form as cheap as is compatible  with its
  ze  and  preservation, and its sale follows  as a
matter"of  course.  No library can be  called  com-
pTelewithoutit.-Buffalo Med. Journal.

  An attempt to give our readers any adequate idea
 r R.  Zl\ nmount of instruction accumulated in
1 evoYumeTwouldbe'feeble and hopeless.   The
effort of "he  distinguished author to  concentrate
f„a small space hi! great fund of knowledge, has
  This hook is a necessity to every practitioner.-
Am. Med. Monthly. 
28
BLANCHARD  &  LEA'S  MEDICAL
ROYLE'S  MATERIA  MEDICA  AND  THERAPEUTICS;  including  the
  Preparations of the Pharmacopoeias of London, Edinburgh, Dublin, and of the United States.
  With many new medicines.  Edited by Joseph Carson, M. D.  With ninety-eight illustrations.
  In one large octavo volume, extra cloth, of about 700 pages.  $3 00.
                           SMITH  (HENRY  H.),  M.D.,
                    Professor of Surgery in the University of Pennsylvania, &c.
MINOR  SURGERY; or, Hints on the Every-day Duties of  the Surgeon.   Illus-
  trated by two hundred and forty-seven illustrations.   Third and enlarged edition.  In one hand-
  some royal 12ino. volume,  pp. 456.  In leather, $2 25; extra cloth, $2 00.
  And a capital little book it is. .  . Minor Surgery,
we repeat, is really  Major  Surgery, and anything
which teaches it is worth having.  So we cordially
recommend this little book of Dr. Smith's.—Med.-
Chir. Review.
  This beautiful little work  has been compiled with
a view to the wants of the profession in the matter
of bandaging, &c.,and well and ably has the author
performed his  labors.  Well  adapted to give  the
requisite  information on  the subjects of which it
treats.—Medical Examiner.
  The directions are  plain, and illustrated through-
out with clear engravings.—London Lancet.
  One of the best works they can consult on the
subject of which it  treats.—Southern Journal of
Medicine  and Pharmacy.

                                BY THE SAME  AUTHOR,  AND

                         HORNER (WILLIAM  E.), M. D.,
                   Late Professor of Anatomy in the University of Pennsylvania.

AN ANATOMICAL  ATLAS, illustrative of the  Structure of the Human Body.
  In one volume, large imperial  octavo, extra cloth, with about  six hundred and fifty beautiful
  figures. $3 00.
  A work such as the  present is therefore highly
useful to the student, and we commend  this one
to their attention.—American Journal of Medical
Sciences.
  No operator, however eminent, need hesitate to
consult this unpretending yet excellent book. Thosa
who are young in the business would find Dr. Smith's
treatise  a necessary companion, after once undef-
standing its true character.—Boston Med. and Surg.
Journal.

  Noyoung practitioner should be without this little
volume; and we venture to assert, that it maybe
consulted by the senior members of the profession
with more real benefit, than  the more voluminous
works.— Western Lancet.
  These figures are well selected, and present a
complete and  accurate representation of that won-
derful fabric, the human body. The plan  of this
Atlas, which renders it  so peculiarly convenient
for the student, and  its superb artistical execution,
have been already pointed out.  We must congratu-
late the student upon the completion of this Atlas,
as it is the most convenient work of the kind that
has yet appeared ; and we must add, the very beau-
tiful manner in which it is " got up" is so creditable
to the country as to be flattering to our national
pride.—American Medical Journal.
                              SARGENT (F.  W.),  M. D.

ON BANDAGING  AND OTHER OPERATIONS OF MINOR  SURGERY.
  Second edition, enlarged.  One handsome royal 12mo. vol., of nearly 400 pages, with 182 wood-
  cuts.  (Now Ready, 1856.)  Extra cloth, $1 40; leather, $1 50.
  This very useful little work has long been a favor-
ite with practitioners and students. The recent cull
for a new edition has induced its author to make
numerous important additions.  A slight alteration
in the size of the page has enabled him to introduce
the new matter, to the extent of some fifty pages of
the former edition, at the same time that his volume
is rendered still more compact than its less  compre-
hensive predecessor.  Adoublegain in thus effected,
which, in a vade-mecum of this  kind, is a  material
improvement.—Am. Medical Journal.
  Sargent's Minor Surgery has always been popular,
and deservedly so. It furnishes that knowledge ofthe
most frequently requisite performances of surgical
art which cannot be entirely understood by attend-
ing clinical lectures.  The art of bandaging, which
is  regularly taught in Europe, is very frequently
overlooked by teachers in this country; the student
and junior practitioner, therefore, may often require
that knowledge which this little volume so tersely
and happily supplies.  It is neatly printed and copi-
ously illustrated by the enterprising publishers, and
should be possessed by all who desire to be thorough-
ly conversant with the details of this branch of our
art.—Charleston Med. Journ. and Review, March,
1856.
  A work that has been  so long and favorably known
to the profession as Dr. Sargent's Minor Surgery,
needs no commendation from us.  We would remark,
however, in this connection, that minor surgery sel-
dom gets that attention in our schools that its im-
portance deserves.  Our larger works are also very
defective in their teaching on these small practical
points.   This little book will supply the void which
all must feel who have not studied its pages.—West-
ern Lancet, March, 1856.
  We confess our indebtedness to this little volume
on many occasions, and can warmly recommend it
to our readers, as it is not above the consideration
of the oldest and most experienced.—American Lan-
cet, March, 1856.
SKEY'S OPERATIVE SURGERY.  In one very
  handsome octavo volume, extra cloth, of over 650
  pages, with about one hundred wood-cuts. $3 25.
STANLEY'S TREATISE ON  DISEASES OF
  THE BONES. In one volume, octavo, extra cloth,
  286 pages.  $1 50.
SOLLY ON THE HUMAN BRAIN; its Structure,
  Physiology, and Diseases.  From the Second and
  much  enlarged London  edition.  In one octavo
  volume, extra cloth, of 500 pages, with 120 wood-
  cuts.  $2 00.

SIMON'S  GENERAL PATHOLOGY,  as conduc-
  ive to the  Establishment of Rational Principles
  for the prevention and Cure of Disease.  In one
  neat octavo  volume, extra cloth, of 212 pages.
  $ 1 25.
                             STILLE (ALFRED), M.D.
PRINCIPLES  OF   GENERAL  AND   SPECIAL   THERAPEUTICS
  handsome octavo.  (Preparing.)
In 
AND  SCIENTIFIC  PUBLICATIONS.
29
      SHARPEY (WILLIAM),  M. D.,  JONES  QUAIN, M. D., AND
WTTMaxt  ivT.mo,  RICHARD  QUAIN,  F. R. S., &.C.
  M  d  p  fANATOMY.   Revised, with Notes  and Additions, by Joseph Leidy,
  vohnnesleafh^ „<■ uto,?y ln the University of Pennsylvania.  Complete in two large octavo
  engravings^ on wood  $6 M**™ hundred Pa&es-  Beautifully illustrated with over five hundred
anatomical study, by placing before"""VudeS
every department of his science, with a view  to
the relative importance of each   and so skilfully
have  he different parts been interwoven, that  no

OT-?|WwT£rVb1' W°rk the basis of his si^.
will hereafter have any excuse for  neglecting  or
undervaluing any important particulars connected

www th! h-ctu7 .?f  tl,e human  framei  and
whether the bias of his mind lead him in a more
especial manner to surgery, physic, or physiology,
he will find here a work at once so comprehensive
and practical as to defend hiin from exclusiveness
on the one  hand, and  pedantry on the other.—
Journal  and Retrospect of the Medical Sciences.
  We have no hesitation in recommending  this trea-
tise on anatomy as the most complete on  that  sub-
ject in the English  language; and the only  one,
perhaps, in  any language, which  brings  the state
of knowledge forward  to  the most recent disco-
veries.—The Edinburgh Med. and Surg. Journal.
                           SMITH  (W. TYLER), M. D.,
                       Physician Accoucheur to St. Mary's Hospital, &c.

ON  PARTURITION,  AND  THE  PRINCIPLES  AND  PRACTICE  OF
  OBSTETRICS.  In one royal 12mo. volume, extra cloth, of 400 pages.  $1 25.

                          BY THE SAME AUTHOR.—(Just Issued.)

A PRACTICAL  TREATISE  ON  THE  PATHOLOGY  AND  TREATMENT
  OF LEUCORK.H03A.  With numerous  illustrations.  In  one very handsome  octavo volume,
  extra cloth, of about 250 pages.  $ 1 50.
  We decide this book to be one of the most useful  indirectly, under abiding obligations. — Nashville
monographs which has  appeared in this country.  Journ. of Medicine.
K! bhf= ^"rhf ^ confus,ion,in TeSf rud W    We hail the appearance of this practical and in-
*  be  ^."^.Hf^ d">'eg"'a"ty and  har-  valuable work, therefore, as a real  acquisition to
T^fhi wwJ    e  ■ sc'ence;, Dr- fmith has  our medical iiUrature.-flr«HcaJ Gazette.
placed the whoie profession directly, and mankind
                           SIBSON (FRANCIS),  M. D.,
                              Physician to St. Mary's Hospital.
MEDICAL ANATOMY.  Illustrating the  Form, Structure,  and Position of the
  Internal Organs  in Health and Disease.  In large imperial quarto, with splendid colored plates.
  To match "Maclise's Surgical Anatomy."  Part I.  (Preparing.)
                      SCHOEDLER (FRIEDRICH),  PH.D.,
                       Professor ofthe Natural Sciences at Worms, &c.

THE  BOOK OF  NATURE;  an  Elementary  Introduction  to  the  Sciences  of
  Physics, Astronomy, Chemistry, Mineralogy, Geology, Botany, Zoology, and Physiology.  First
  American edition, with a Glossary and other  Additions and Improvements; from  the  second
  English edition.   Translated from  the sixth German edition, by Henry Mkdlock, F. C. S., Sec.
  In one thick volume, small octavo,  extra cloth, of about seven hundred pages, with 679 illustra-
  tions on wood. Suitable for the higher Schools and private students.   (Now Ready.)  $1 80.
                             TANNER  (T.  H.),  M. D.,
                          Physician to the Hospital for Women, &c.

A MANUAL OF CLINICAL  MEDICINE AND  PHYSICAL DIAGNOSIS.
  To which  is added The Code of Ethics of the  American Medical  Association.   Second
  American Edition.  In  one  neat volume, small 12mo.  Price in extra cloth, 87$ cents ;  flexible
  style, for the  pocket, 80 cents.  (Lately Published.)
  In this admirable little work the author's object has been to give the young practitioner that kind
of information which enables him to make practical application of the  knowledge acquired by his
studies and which is not to be found in the text-books.  Such a manual has been much wanted,
as it  fills a void which has long been felt, but which there has hitherto been no attempt to supply.
That the author has succeeded in his endeavor, is  sufficiently shown  by the unusually favorable
reception which the work has already received, although only just published.
                                             practitioners, it has only to be seen, to win for itself
                                             a place upon the shelves of every medical library.
                                             Nor  will it be " shelved" long at a time; if we mis-
                                             take not, it will be found, in the best sense of the
                                             homely but expressive word, " handy."  The style
                                             is admirably clear, while it is so sententious as not
                                             to burden the memory.  The arrangement is, to our
                                             mind, unexceptionable.  The work, in short, de-
                                             serves the  heartiest commendation.—Boston  Med.
                                             and Surg. Journal
                                               We cordially recommend every young practitioner
                                             who wishes to reap the greatest possible benefit from
                                             his observation of disease to make  this  book his
                                             daily companion.—New Hampshire Journal of Medi-
                                             cine.
                                               As a convenient and suggestive book of reference,
                                             weaccord it our hearty praise.— Va. Med. and Surg.
                                             Journal.
  Dr. Tanner has, in a happy and successful manner,
indicated the leading particulars  to which, in the
clinical study of a case of disease, the attention of
the physician is to be directed, the value and import
ofthe various abnormal phenomena detected, and the
several instrumental and accessory means which
maybe called into requisition to facilitate diagnosis
and increase its certainty —Am.  Journal of Med.
Sciences.                         .  ,    ,  .
  In this small work is collected a fund of such in-
foSlto.. the student at the commencement and
pvpt, dnrin" the continuance of his studies, is oiten
sadTy troubled to know where to look toe .-Montreal
Med. Chronicle.
  The Work is an  honor to its writer, and must ob-
JC„* wide circulation by its intrinsic merit alone.
U ttZ K us that but slight effort on  he part of the
nnnhshers will be requisite to exhaust even a large
Pd tion  Suited alike to the wants of students and 
30
BLANCHARD  &  unaa  MCUIUAL
                     TAYLOR (ALFRED S.), M.  D., F. R. S.,
                Lecturer on Medical Jurisprudence and Chemistry in Guy's Hospital.
MEDICAL JURISPRUDENCE.   Fourth American, from the fifth improved and
  enlarged English Edition.  With Notes and  References to American Decisions, by Edward
  Hartshorne, M. D.  In one large octavo volume, leather, of over seven hundred pages.   (Just
  Ready, June, 1856.)  $3 00.
  This standard work has lately received a very thorough revision at the hands ofthe author, who
has introduced whatever was necessary to render it complete and  satisfactory in carrying out the
objects in view.  The editor has likewise used every exertion to make it equally thorough with
regard to all matters relating to  the practice  of  this country.  In doing this, he has carefully ex-
amined all that has appeared on  the subject since the publication ofthe last edition, and has incorpo-
rated all the new information thus presented.  The  work has thus been considerably increased in
size, notwithstanding which, it has been kept  at its former very moderate price, and in every respect
it will be  found  worthy of a continuance  of  the remarkable favor which has carried it  through so
many editions on bpthsides of the Atlantic.   A  few notices  of the former editions are appended.
                                              most attractive books that we  have met with ; sup-
                                              plying  so  much both  to inierest and instruct, that
                                              we do not hesitate to affirm that afler having once
                                              commenced its perusal, few could be prevailed upon
                                              to desist before completing it.  In the last London
                                              edition, all the newly observed and accurately  re-
                                              corded facts have been inserted, including much that
                                              is recent of Chemical, Microscopical, and Patholo-
                                              gical research, besides papers on numerous subjects
                                              never before published.-C/»aWes«on Medical Journal
                                              and Revievt.
  We know of no -work on Medical Jurisprudence
which contains in the same space anything like the
same amount of valuable matter —N. Y. Journal of
Medicine.
  No work upon the subject can be put into the
hands of students either of law or medicine which
will  engage them more closely or profitably ; and
none could be offered  to the busy practitioner of
either calling, for the purpose of casual or hasty
reference, that would be more likely toatford the aid
desired.  We therefore recommend itas the best and
safest manual for daily use.—American Journal oj
Medical Sciences.
  So well is this work known to the members both
of the medical and legal professions, and so highly
is it appreciated  by them, that it cannot be necessary
for us to say a word in its commendation; its having
already reached a fourth edition being the best pos-
s ble testimony  in its favor.  The author has ob-
viously subjected the entire work to  a very careful
revis on.—Brit, and Foreign Med. Chirurg. Review.
  This work of Dr. Taylor's is generally acknow-
ledged to be one  of the ablest extant on the subject
of medical jurisprudence.  It is certainly one of the
  It is not excess of praise to say that the volume
before us is the very best treatise extant, on Medical
Jurisprudence.   In saying this, we do not wish to
be understood as detracting from  the merits of (he
excellent works of Beck, Ryan,  Traill,  Guy,  and
others; but in interest and value  we think it must
be conceded that Taylor is superior to anything that
has preceded it.  The author is already well  known
to the profession by his valuable treatise on Poisons;
and the present volume will  add  materially to his
high  reputation for accurate  and  extensive know-
ledge and discriminating judgment.—N. W. Medical
and Surgical Journal.
                                  BY  THE SAME AUTHOR.
ON POISONS,  IN  RELATION TO  MEDICAL  JURISPRUDENCE  AND
  MEDICINE.  Edited, with Notes and Additions, by R. E. Griffith, M. D.  In one large octavo
  volume, leather, of OSS pages.  $3 00
With
octavo
                            Now Complete (March, 1857).

                 TODD (ROBERT BENTLEY),  M. D.,  F. R.  S.,
                     Professor of Physiology in King's College, London ;  and
                          WILLIAM  BOWMAN,  F. R.  S.,
                      Demonstrator of Anatomy in King's College, London.

THE PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN.
  about three hundred large  and beautiful  illustrations on wood.  Complete in one larg
  volume, of 950 pages, leather.  Price $4 50.
  The very great delay which has occurred in the completion of this work has arisen from the de-
sire of the authors to verily  by their own examination the various questions and statements pre-
sented, thus rendering the work one of peculiar value and authority.   By the wideness of its scope
and the accuracy of its facts it thus occupies a position of its own, and becomes necessary to all
physiological students.
  [g^* Gentlemen who have received portions of this work,  as published in the " Medical News
and Library," can now complete their  copies,  if immediate application be made.  It 'will be fur-
nished as follows, free by mail, in paper covers, with cloth backs.
  Parts I., II., III. (pp. 25 to 552),  $2 50.
  Paet IV. (pp. 553 to end,  with Title, Preface, Contents, &c), $2 00.
  Or, Part IV., Section II. (pp. 725 to end, with Title, Preface, Contents, &c), $1 25.
                                              cannot conclude without strongly recommending the
                                              present work to all classes of our readers, recogniz-
                                              ing talent and depth of research in every page, and
                                              believing, as we do, that the diffusion of such know-
                                              ledge will certainly tend to elevate the sciences of
                                              Medicine and Surgery.—Dublin Quarterly Journal
                                              of Medical  Sciences.
  In the present part (third) some of the most diffi-
cult subjects in Anatomy and Physiology are handled
in the  most masterly manner.  Its authors have
stated that this work was intended " for the use of
the student and practitioner in medicine and  sur-
gery," and we can recommend it to both, confident
that it is  the most perfect work of its kind.  We
                       TODD (R.  B.),  M. D.,  F. R. S.,  &c.
CLINICAL  LECTURES  ON CERTAIN  DISEASES  OF  THE  URINARY
  ORGANS AND ON DROPSIES. In one octavo volume.  (Just Ready.)  $1 50.
  The valuable practical nature of Dr. Todd's writings have deservedly rendered them favorites
with the pro es^ion, and the present volume, embodying the medical aspects of a class of diseases
not elsewhere to be found similarly treated, can hardly fail to supply a want long felt by the prac-
titioner. 
AND  SCIENTIFIC  PUBLICATIONS.
31
LECTURES  ON
 WATSON (THOMAS),  M.D.,  &.C.
THE  PRINCIPLES  AND  PRACTICE
OF  PHYSIC.
Third American edition, revised, with  Additions, by D.  Francis Condie, M. D , author of a
  "Treatise on the Diseases of Children," &c
  large pages,  strongly bound with raised bands.
  To say that it is the very best work on the sub-
ject now extant, is but to echo the sentiment of the
medical  press  throughout the country. — N. O.
Medical Jou rnal.

  Of the text-books recently republished Watson is
very justly the  principal favorite.—Holmes's Rep.
to Nat. Med. Assoc.

  By universal consent the work ranks among the
very best text-books in our language.—Illinois and
Indiana Med. Journal.

  Regarded on all hands as one of the very best, if
not  the very best, systematic treatise on practical
medicine extant.—St. Louis Med. Journal.
In one octavo volume, of nearly eleven hundred
 $3 25.
  Confessedly one of  the very best works on the
principles and practice of physic in the English or
any other language.—Med. Examiner.
  Asa text-book it has no equal; as a compendium
of pathology and practice no superior.—New York
Annalist,
  We know of no work better calculated for being
placed in the hands of the student, and for a text-
book; on every important point the author seems
to have posted up his knowledge  to the  day.—
Amer. Med. Journal.
  One of the most practically useful books that
ever was presented to the student.— iV. Y.  Med.
Journal.
                    WILSON (ERASMUS),  M. D.,  F. R. S.,
                               Lecturer on Anatomy, London.

A SYSTEM  OF  HUMAN ANATOMY, General and Special.   Fourth Ameri-
  can, from the last English edition.   Edited by Paul B. Goddard, A. M., M. D.  With two hun-
  dred and  fifty illustrations.  Beautifully printed, in  one large octavo volume, leather, of nearly
  six hundred pages.  33 00.
  In many, if not all the Colleges of the Union, it
has become a standard text-book.   This, of itself,
is sufficiently expressive of its value.  A work very
desirable to the student;  one, the  possession of
which will greatly facilitate his  progress  in the
study of Practical Anatomy.—New  York Journal of
Medicine.

  Its author ranks with  the highest on Anatomy.—
Southern Medical and Surgical Journal.
                                              It offers to the student all the assistance that can
                                             be expected from such a work.—Medical Examiner.
                                              The most complete and convenient manual for the
                                             student we  possess.—American Journal of Medical
                                             Science.
                                              In every  respect,  this work  as  an  anatomical
                                             guide for the student and  practitioner, merits our
                                             warmest and most decided praise.—London Medical
                                             Gazette.

                          by the same author.  (Now Ready.)

THE   DISSECTOR'S MANUAL; or, Practical  and  Surgical Anatomy.   Third
  American, from  the  last revised and enlarged English edition.  Modified and  rearranged, by
  William Hunt, M. D., Demonstrator of Anatomy in the University ot  Pennsylvania.   In one
  large and handsome royal 12mo. volume, leather, of 582 pages, with 154 illustrations.  $2 00.
  The modifications and additions which this work has received  in passing recently through the
author's hands, is sufficiently indicated by the  fact that it is enlarged  by more  than one hundred
pages, notwithstanding that it is printed in smaller type, and with a greatly enlarged page.
  It remains only to add, that after a careful exami- I ing very superior claims, well calculated to facilitate
nation, we have no hesitation in recommending this | their studies, and render their labor less irksome, by
work to  the notice of those for whom it has been I constantly  keeping before  them  definite objects  of
expressly written—the students—as a guide possess- | interest.—The Lancet.

                                 BY THE SAME AUTHOR.

ON DISEASES  OF  THE  SKIN.   Third  American,  from the third London
  edition.  In one neat octavo volume, of about five hundred pages, extra cloth.   $1 75.
  The "Diseases  of the Skin," by Mr. Erasmus I in that department of medical literature.—Medico-
Wilson, may now be regarded as the standard work | Chirurgical Review.

                                 BY THE SAME AUTHOR.

ON  CONSTITUTIONAL   AND  HEREDITARY   SYPHILIS,  AND   ON
  SYPHILITIC ERUPTIONS. In one small octavo volume, extra cloth, beautifully printed, with
  four exquisite colored plates, presenting more than thirty varieties of syphilitic eruptions.  $2 25.

                          BY THE SAME AUTHOR.  (Just Issued.)

HEALTHY  SKIN;  A Popular Treatise on the  Skin and Hair,  their  Preserva-
  tion and  Management.  Second American, from the fourth London edition.   One neat volume,
  royal 12mo., extra cloth, of about 300 pages, with numerous illustrations.  $1 00; paper cover,
  75 cents.
WHITEHEAD ON THE CAUSES AND TREAT- I WALSHE ON  DISEASES  OF  THE  HEART,
  MENT OF ABORTION  AND STERILITY. |   LUNGS,  AND  APPENDAGES;  their  Symp-
  Second American Edition.  In one volume, octa--   toms and Treatment.  In one handsome volume,
  vo extra cloth, pp. 308.  $1 75.               |   extra cloth, large royal 12mo., 512 pages.  $1 50.

                                   WILDE (W.  R.),
                  Surgeon to  St. Mark's Ophthalmic and Aural Hospital, Dublin.

AURAL SURGERY,  AND THE NATURE AND TREATMENT OF DIS-
  FASES OF THE EAR.   In one handsome octavo  volume, extra cloth, of 476 pages, with
  illustrations.  $2 80.
  i<h-  work certainly contains more information on I the author for his manful effort to rescue this depart-
  Itns worn       ,  ■  ■  devoted than  any other  ment of surgery from the hands of the empirics who
wfth whfch we^re acquainted.  We feel  grateful to | nearly monopolize  it. 
32       BLANCHARD  &  LEA'S  SCi^Hiinu  ruBLlUATIONS.
                          WEST (CHARLES), M. D.,
Accoucheur to and Lecturer on Midwifery at St. Bartholomew's Hospital, Physician to the Hospital for
                                   Sick Children, &c.
LECTURES   ON  THE  DISEASES  OF INFANCY AND  CHILDHOOD.
  Second American, from the Second and Enlarged London edition.   In one volume, octavo,
  extra cloth, ol nearly five  hundred pages.  (Just Issued. ) $2 00.
  We take leave of Dr. West with great respect for
his attainments, a due appreciation of his acute
powers of observation, and a  deep sense of obliga-
tion for  this valuable contribution to  our profes-
sional  literature.  His book is undoubtedly in many
respects  the best we possess on diseases of children.
Dublin Quarterly Journal of Medical Science.
  Dr. West has placed the profession under deep ob-
ligation by this able, thorough, and finished work
upon a subject which almost daily taxes to the ut-
most the skill of the general practitioner. He  has
with singular felicity threaded his way through all
the tortuous labyrinths of the difficult subject he  has
undertaken to elucidate, and has in  many of  the
darkest corners left a  light, which will never be
extinguished.—Nashville Medical Journal.
                        by the same author.   (Nearly Ready.)
                 Publishing in the "Medical News and Library," for 1856.

LECTURES  ON  THE DISEASES OF  WOMEN.   In two parts.
  Part I. 8vo. of about 300 pages, comprising the Diseases of the Uterus.
  Part II. (Preparing), will contain Diseases of the Ovaries, and of all the parts connected
    with the Uterus; of the Bladder, Vagina, and External Organs.
  The object of the author in this work is to present a complete but  succinct treatise on Female
Diseases, embodying the results of his experience during the last ten years at St. Bartholomew's
and the Midwifery Hospitals, as well as in private practice.  The characteristics which have se-
cured to his lonner works  so  favorable a reception, cannot fail to render the present volume a
standard authority on  its important subject.  To show the general scope ofthe work, an outline ol
the Contents of Part I. is subjoined.
Lectures I, II—Introductory—Symptoms—Examination of Symptoms—Modes of Examina-
  tions.  Lectures HI, IV , V—Disorders of Menstruation, Amenorrhcea, Menori hagia, Dys-
  menorrhoea.  Lectures VI,  VII, VIII.—Inflammation of the Uterus, Hypertrophy, Acute
  Inflammation, Chronic Inflammation, Ulceration ofthe Os Uteri, Cervical Leucorrhoea.  Lectures
  IX , X., XI, XII, XIII.—Misplacement of the  Uterus, Prolapsus, Anteversion, Retrover-
  sion, Inversion.  Lectures XIV.,  XV., XVI, XVII.—Uterine Tumors and Outgrowths,
  Mucous, Fibro-cellular, and Glandular Polypi, Mucous Cysts, Fibrinous Polypi, Fibrous Tumors,
  Fibrous Polypi, Fatty Tumors, Tubercular Diseases.  Lectures XVIIL, XIX., XX.—Cancer
  of the Uterus.
Part II. will receive  an equally extended treatment, rendering the whole an admirable text-book
  ibr the student, and  a reliable work for reference by the practitioner.

                          by the same author.  (Just Issued)

AN ENQUIRY INTO THE  PATHOLOGICAL IMPORTANCE  OF ULCER-
  ATION OF THE OS UTERI.  In one neat octavo volume, extra cloth. $1  00.
                    WILLIAMS (C  J. B.),  M.  D., F.  R. S.,
                Professor of Clinical Medicine in University College,  London, &c.

PRINCIPLES OF MEDICINE;  comprising General  Pathology and Therapeu-
  tics, and a brief general view  of Etiology, Nosology, Semeiology, Diagnosis, Prognosis, and
  Hvienics.  Edited, with Additions, by Meredith Ulymer, M.D.  Fourth American, from the
  last^and enlarged London edition.  In one octavo volume, leather, of 476 pages.  $2 50.
  The best exposition in our language, or, we be- I   Few books have proved more useful, or met with
lieve in any language, of rational medicine,  in its | a more ready sale  than this, and no practitioner
present improved  and  rapidly improving  state.— I should regard his library as complete without  it.
British and Foreign Medico-Chirurg. Review.    | —Ohio Med. and Surg. Journal.
                              WHAT TO OBSERVE
AT   THE  BEDSIDE  AND   AFTER  DEATH,  IN  MEDICAL  CASES.
  Published under the authority of the London Society for Medical Observation.  A new American,
  from the second and revised London edition.  In one very handsome volume, royal 12mo., extra
  cloth.  (Just Issued.)  $ 1 00.
  To the observer who prefers accuracy to blunders I  One of the finest aids to a young practitioner we
and precision to carelessness, this little book is in- have ever seen.—Peninsular Journal of Medicine.
valuable.__N- H. Journal of Medicine.            I
                          YOUATT (WILLIAM), V. S.
THE   HORSE.   A new  edition, with numerous illustrations;  together with a
  general history ofthe Horse; a Dissertation on the American Trotting Horse ; how Trained and
  Jockeyed; an Account of his Remarkable Performances; and an Essay on the Ass and the Mule.
  By J. S. Skinner, formerly Assistant Postmaster-General,  and Editor of the  Turf Register.
  One large octavo volume,  extra cloth.  $1  50.
  The attention of all who keep horses is requested to this handsome and complete edition  of a
work which is recognized as the standard authority on all matters connected with veterinary medi-
cine.  The very low price at which it is now ottered,  free by mail, places it within the reach oi
every one.
                                BY  THE SAME  AUTHOR.

THE  DOG.   Edited by  E. J. Lewis,  M. D.  With  numerous  and beautiful
  illustrations. In one very handsome volume, crown Svo., crimson cloth, gilt. $1 25. 
 
 

 
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