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THE
            MICROSCOPIC   ANATOMY

                              OF


       THE    HUMAN    BODY,

                              IN

                HEALTH AND  DISEASE,

           ILLUSTRATED WITH NUMEROUS DRAWINGS IN COLOUR.

                              BY
                 ARTHUR  HILL  MSSALL, M. R.
i         Author of a "History of the British Fresh-water Algie;" Fellow of the Linnjean Society; Member of the
           Royal College of Surgeons of England; one of the Council of the London Botanical Society j
                 Corresponding Member of the Dublin Natural History Society, <kc.

                              WITII
        ADDITIONS  TO  THE  TEXT AND PLATES,
f                              AND
                    AN  INTRODUCTION,
l               CONTAINING INSTRUCTIONS IN MICROSCOPIC MANIPULATION,

                              BY
                    HENRY VAJVARSDALE, M, D.

                        IN TWO  VOLUMES.
                            VOL. I.

                        NEW  YORK:
              SAMUEL  S. & WILLIAM  WOOD,
                      261  PEARL  STREET.
                             1855. 
an
551
ENTERED, ACCORDING TO ACT OF CONGRESS, IN THE YEAR 1851, BY



                 E. C. KELLOGG,


IN THE CLERK'S OFFICE OF THE DISTRICT COURT OF CONNECTICUT.
   FOUNDRY OF


SILAS ANDRUS AND SON,


   HARTFORD.
  PRESS OF


F. C. GUTIERREZ,


  NEW-YORK. 
TO
THOMAS  WAKLEY,   ESQ.,  M. P.,

             CORONER, ETC., ETC.
      Dear  Sir:
  To you I dedicate  the accompanying pages, devoted  to
the elucidation of a department of minute anatomy of daily
increasing interest and importance.
  I thus dedicate this work to you  on two grounds; the
one personal and private, the other public.
  On my mentioning the design of this work to you—and
you were one of the first persons to whom it was mentioned
—you were kind enough to express yourself in  terms  of
approval and encouragement, and to proffer any assistance
in your power in the furtherance of my undertaking.  Of
this conduct on your part I have ever entertained a pleasing
and grateful remembrance;  and it is  this which constitutes
the private ground of my dedication.
  But I  dedicate this work  to  you on  a  higher and more
important ground.  I have for many  years seen in you the 
4
DEDICATION.
able and strenuous advocate—amidst  much obloquy and
misrepresentation—of the rights of that profession of which
we are both members:  on this high ground I conceive you
to be entitled to the gratitude of your professional brethren;
and with this feeling on  my mind  of  your conduct  and
services in a good cause,

              I beg to subscribe  myself,
                       Yours, very faithfully,
                                 THE AUTHOR. 
PREFACE   TO  THE  ENGLISH  EDITION.
   After three years of more or less constant labour, the welcome and often-wished-
 for period of the completion of this work has arrived, and the author is at liberty to
 address  himself to his readers, and to explain the motives and the circumstances
 which have led to its production.
   The idea of this work presented itself to the author's mind several years since;  it
 was not, however, until about the period above referred to, that its actual execution
 was commenced.
   At the time when its design was first conceived, the powers of the microscope in
 developing organic structure were but beginning to be known and appreciated, and
 the importance of its application to physiology and pathology was but dimly perceived.
   At that period, also, but few complete works devoted to microscopic anatomy had
 appeared in any language, native or foreign; more recently this deficiency, as res-
 pects  France  and Germany, has  been well supplied by the  appearance of several
 original works, as those of Donne, Mandl, Lebert, Miiller, Henle, Vogel, Gerber, and
 Wagner; England, however, has not as yet contributed her  share  of distinct and
 independent works on  general anatomy: not that our  observers  have been idle, or
 have neglected a field of inquiry so interesting and important, resting satisfied with
 mere translations-: a whole host of intelligent and  able microscopists have applied
 themselves to the investigation of the  ultimate  structure of the several tissues and
 organs, and this with a  preeminent degree of success.  Among the more remarkable
 of these investigators,  the following may be enumerated: Gulliver, Martin Barry,
 Busk, Addison, Kiernan, Sharpey, Goodsir, Tomes, Toynbee, Johnson, Simon, Todd
 and Bowman, Quekett, Erasmus Wilson, Hughes Bennet, Carpenter, Rainey, Hand-
 field Jones, and Gairdner.
  The results of the labours of these observers have not as  yet, however, been
 embodied in a  separate  work; but some of them have been mixed up with works on
 descriptive anatomy and physiology, as  in Sharpey's  edition of Quain's Anatomy, in
 Carpenter's "Principles" and "Manual" of Physiology, and in Todd and Bowman's
 "Physiological Anatomy."   The last is an admirable book, full of original research
 and important facts.
  Now, one of the purposes, the accomplishment of which has been attempted in the
 following pages, has been  the collecting together of the numerous communications
 on general anatomy to be found scattered through the pages of our different scientific
 periodicals, and their combination into a whole.
  The further  objects which the author has had in view in the production of this
 work have been simplicity  of description, fidelity of representation, and the addition
 of such facts and particulars as have occurred to himself in the course of his own
investigations:  and  he  may  take this  opportunity of  observing,  that in but few
instances has he written upon a subject  without previous investigation. 
 G            PREFACE  TO  THE  ENGLISH  EDITION.

   The author considers it right,jn justice to himself, that certain disadvantages under
 which  the  work  has  been produced  should be mentioned: these were,  constant
 engagement in general practice, much anxiety, and, though last, not least, ill health.
 These  would have been sufficient to have deterred many from the undertaking alto-
 gether.  Although this has not been  the effect  upon the  author, yet it cannot be
 questioned  but that they have operated in some respects to the  disadvantage of the
 work;  and  he begs that it  may be taken neither as the measure of  that of which
 the subject  is capable, nor of the author's  powers of observation and  description
 exercised under more favourable circumstances of health, leisure, and feeling.
   The  author makes these few remarks not  in order to deprecate any fair criticism,
 but simply that the truth in reference to the  production of this work may be known
 in justice both to the writer and the reader.
   Having said thus much in relation  to the work itself, the author has  now the
 pleasing task of returning his acknowledgments to  those who have in any way
 assisted him in his laborious though most agreeable task; these are particularly due
 to the following: Mr. Quekett, Dr. Handfield Jones, Professor Sharpey, Mr. Tomes,
 Mr. Bowman, Mr. Busk,  Professor Owen, Mr. Canton, Dr.  Carpenter, Dr. Letheby,
 Dr. Robert Barnes, Mr. Ransom, Mr. Pollock, and Mr. Gray, of St. George's Hospital,
 Mr. Hett, and Mr. Andrew Ross:  they are also due to  Mr. Drewry Ottley; Dr. Rad-
 cliffe  Hall;  Mr.  Coppin, of Lincoln's Inn; Messrs. Welch and Jones, of Dalston;
 Mr. Berry, of James-street, Covent Garden;  Mr. Cowdry, of Great Torrington; Dr.
 Jones, of Brighton;  Dr. Chambers, of Colchester; Mr. Milner, of Wakefield;  Mr.
 Walker,of St. John's-street Road; Mr. Ringrose, of Potter's Bar; Dr.  Halpin,  of
 Cavan; and Mr.  H. Hailey, of Birmingham.
  To Dr. Letheby I hope shortly to have a second  opportunity of  rendering my
 thanks,  in connexion, viz:  with the work on crystals,  entitled "Human  Crystallo-
 graphy," an  announcement of which appeared some months since, and towards  the
 completion of which considerable materials have already been collected.
  To Mr. Hett, my thanks are especially due for having, at considerable trouble and
 inconvenience, furnished me with very many of the injections required to illustrate
 Part  XV. of the "Microscopic Anatomy;"  these, together with numerous  other
 injected preparations of that  gentleman which I have  seen, have been of first-rate
 quality; and the microscopic anatomist has reason to hail the advent of such a man
 to the cause of general  anatomy with the highest satisfaction.
  To Mr. Andrew Ross, on this, as on a former occasion, I have to express my obli-
 gations, Mr. R. having at all times furnished me with any information I might require,
 as well as provided me  with any necessary apparatus.
  Thus much for  friends.   If, in  the inditing of this  work, I have made a single
 enemy, I am  sorry for it, and still more so if I have given any real occasion for offence.
 If, in  differing from  other observers as  to  certain facts and  conclusions,  I have
 expressed myself in such a  manner as to wound their feelings, as in  one  or two
instances I fear I may have done, I much regret it: the differences among men whose
common aim is the knowledge of truth, as manifested in  the works of creation, should
never be deep or lasting; for this community of purpose should ever be a firm bond
 of union between such men, seekers after truth, and should displace from their minds
the lesser and grosser feelings of rivalry and ill-will.
Nottino Hill, July 27th, 1849, 
          PREFACE,

BY  THE  AMERICAN  EDITOR.
   The Microscopic Anatomy of Dr. A. H. Hassall is offered to the student in this
 department of Medical Science, as  the only completed work on the subject in the
 English language.
   In the present edition, the  introduction and additions to the text, are chiefly of a
 practical nature; this feature, it is hoped, will not  detract from the high scientific
 character of the original work, but will give it some additional value for  those who
 wish to pursue the study of minute anatomy, by the aid of the microscope.
   It will be observed that, in some  instances, Dr. Hassall's views differ from those of
 other writers.  Some of these  views Dr. Hassall has  himself modified,  and made
 mention of the fact in the Appendix: other instances of difference have been pointed
 out by the editor; others, again, and these are chiefly matters of opinion on disputed
 points, have not been alluded to, as it did not seem desirable to extend the work, by
 adducing farther conflicting statements on unsettled  questions.
   The ten Plates added to the American edition, are mostly original, and from the
 human subject.   The drawings for these Plates were made  by aid of one of Mr.
 Spencer's  excellent  microscopes, which was obligingly loaned for the purpose by
 Prof. C. R. Gilman.
   For some of the specimens illustrating certain points of anatomy which  have been
 figured, the  editor is indebted to Mr. Hett, of London, so well  known  to micro-
 scopists for his  beautiful preparations  of  healthy  and diseased structures.   For
 other objects of value, to Drs.  Neill and Goddard  of Philadelphia, whose minute
injections have equalled the best foreign ones.
  Almost  all the drawings were made by Mr. W. R. Lawrence of Hartford, whose
previous experience  in drawing from the  microscope, contributed greatly to the 
8          PREFACE   BY  THE  AMERICAN  EDITOR.

accurate  representations he has given.  Several of the figures in Plates LXXIV.
and LXXV., were drawn by Mr. H. A. Daniels, who is well known  to  the  profes-
sion of this city as an accomplished anatomical draughtsman.
  To all these gentlemen, as well as to Prof. A. Clark, and A. S.  Johnson, Esq.,
of New-York, for  valuable hints in manipulation;  and, lastly, to the publishers,
for the  generous manner in  which they allowed the expensive additions, and for
the excellent style in which they have  issued the work, the editor desires to tender
his acknowledgments.
  The additions to the text  are inserted at the end of the Articles, and enclosed
in  brackets.
New-York, 112 West Twenty-Second Street, ^
                       May 1st, 1851.     J 
CONTENTS.
                        INTRODUCTION.

                                                                 PAGE
Its Object.............27
Choice of a Microscope..........27
Division of Subject...........27

      I.—MICROSCOPES  AND  THEIR  ACCESSORIES.
Ross' Microscope............29
PoweU and Lealand's ditto...........29
Smith and Beck's ditto............30
Chevalier's ditto............30
Oberhauser's ditto............30
Brunner's ditto............31
Nachet's ditto............31
Spencer's ditto............31
Allen's ditto.............33
Pike  and Sons' ditto...........33
Accessory Instruments...........33

               II,—PREPARATION  OF  OBJECTS,

Of Fluids   .    .         ..........37
Of Solids.............38
Fine  Injections............42
Materials, used in............42
General Directions...........42
Injections with Turpentine   .         ........42
Ditto with Ether...........43
Ditto by Double Decomposition.........44
Ditto with other Materials..........48

             III.—PRESERVATION  OF  OBJECTS,

Different Cements used...........49
Glass Slides and Cells..........51
Thin Glass    .    .        ..........61
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           SPEECH  R:H',3:,.:TAT!D.M  INSTITUTE
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10                            CONTENTS.

Thin-glass Cells.........
Drilled ditto..........
Tube ditto..........
Built-up ditto..........
Gutta-percha ditto.........

                   FLUIDS  FOR  MOUNTING  OBJECTS.

Alcohol and Water.........
Goadby's Solutions........
Other Fluids..........

                 METHODS OF MOUNTING OBJECTS.
The diy way .
In Canada  Balsam
In Fluid  .
As Opaque  Objects
Labelling Slides
Cabinets
PART   I.
                 FLUIDS  OF  THE  HUMAN  BODY,

                              ARTICLE  I.
The Lymph and Chyle.—General description of Lymphatics and Lacteals, page 67.
  Characters and Structure of Lymph, 68.  Ditto of Chyle, 68.  Ditto of Fluid  of
  Thoracic duct, 70.  Corpuscles of  Thymus,  72.  Structure of Lymphatics, 76.
  Examination of Lymph and Chyle, 78.

                             ARTICLE  II.
The Blood.—Definition,  80.  Coagulation of the Blood, without  the  Body, 80.
  Formation of the Clot, 81.   Formation of the Buffy Coat of the Blood, 83.   Cup-
  ping of the Clot, 85.   Coagulation  of the Blood in  the  Vessels after  Death, 86.
  Signs of Death, 86.  Globules  of the Blood, 88.  The Red Globules, 89.  The
  White Globules, 100.  Molecules of the Blood, 121.   Blood Globules of Reptiles,
  Fishes, and Birds, 123.  Capillary Circulation, 125.   Circulation in the Embryo of
  the Chick,  129.   Venous and  Arterial Blood, 134.   Modifications of  the  Blood
  Corpuscles the results of different external Agencies,  138.   Modifications, the
  results of Decomposition occurring in Blood abandoned to itself without the Body,
  139.   Modifications, the results of Decomposition occurring in Blood  within the
54
54
54
55
55
56
56
57
          ..........59
with heat.........60
               .........62
                         \......63
               .........63
                                                        64 
CONTENTS.
11
  Body after Death, 139.  Causes  of Inflammation, 140.  Pathology of the Blood,
  142.  Importance of a Microscopic Examination of the Blood in  Criminal Cases,
  164.  Examination of, 169.   Preservation of, 170.

                             ARTICLE  III.
Mucus, 171.  General characters, 171.  Mucous Corpuscles, 174.  Nature of Mucous
  Corpuscles, 176.  The Mucus of different Organs, 179.

                             ARTICLE  IV.
Pus, 183.  General characters, 183.  Identity of the Pus and Mucous Corpuscle, 183.
  Distinctive characters of Mucus and Pus, 186.   Distinctions between certain forms
  of Mucus and Pus,  190.  Detection  of Pus in the Blood, 191.  False Pus, 192.
  Metastatic Abscesses, 193.  Venereal Vibrios, 194.

                              ARTICLE  v.
Milk, 195.  Serum of the Milk, 196.  The Globules, 197.  Colostrum, 201.  Patho-
  logical Alterations of the Milk, 203.  The Milk of Unmarried Women, 206.  The
  Milk of Women previous to Confinement, 206.  The  Milk of Women who have
  been delivered, but who have not  nursed their Offspring, 208.   Milk in the Breasts
  of Children, 208.  Different kinds of Milk, 208.   Good Milk, 210. Poor Milk,
  212.  Rich Milk, 213.  Adulterations of Milk, 213.  Formation of Butter, 214.
  Modifications of Milk abandoned to  itself, and in which  Putrefaction has com-
  menced, 215.  The  Occurrence of Medicines, &c. in the Milk, 217.   Examination
  of Mucus, Pus, and  Milk, 217.

                              ARTICLE  VI.
The Semen, 218.  Spermatozoa, Form, Size and Structure of, 218.   Motions of the
  Spermatozoa, 225.   Spermatophori, 228.  Development of the Spermatozoa, 229.
  The Spermatozoa essential to Fertility, 232. Pathology of the Seminal Fluid, 234.
  Application of a Microscopic examination of the Semen to Legal Medicine, 237.
  Examination of Semen, 239.

                             ARTICLE  VII.
Saliva, Bile, Sweat, Urine, 240.  The Saliva, 241.  The Bile, 242.  The Sweat,
  243.  The Urine, 245.   Pathology of the Urine, 246.  Examination of Urine, 252. 
12
CONTENTS.
                               PART   II.


                  SOLIDS  OF  THE  HUMAN  BODY.

                            ARTICLE  VIII.
Fat, 254.   Form, Size, and Structure of the Fat Corpuscle, 254.  Distribution of
  Fat, 259.  Disappearance of, 261.  Injection of FaWesicles, 263.

                             article  IX.
Epithelium, Distribution  of,  264.   Tesselated  Epithelium,  Structure  of,  265.
  Conoidal Epithelium, naked and  ciliated,  Structure of,  267.   Development  and
  Multiplication  of Epithelium, 271.  Nutrition of Epithelium,  272.   Destruction
  and Renewal  of Epithelium, 272.  Epithelial  Tumours, 275.  Examination of
  Epithelium, 275.

                              article  x.
Epidermis, Distribution, Form, Structure, and  Development of, 277.  Epidermis of
  the White and Coloured Races,  279.  Destruction • and Renewal of Epidermis,
  279.  Description of, according to Mr. Rainey, 281.  Examination of, 281.

                             article  XI.
The Nails, Structure of, 282.   Development of, 283. Examination of, 258.

                             ARTICLE  XII.
Pigment Cells, Structure and Varieties of, 286.   Study of, 290.

                            ARTICLE  XIII.

Hair, Form of, 291.  Size of,  292.  Structure of, 292.  Growth of, 297.  Regen-
  eration of, 297.   Nutrition  of, 299.   Distribution of,  300.   Colour  of, 301.
  Properties of,  302.   The Hair of  different Animals, 303.  Method of making
  thin sections of, 305.

                            ARTICLE  XIV.

Cartilages, 306.  True Cartilages, 306.  Fibro-Cartilages, 309.  Nutrition of Car-
  tilage, 311.  Growth and Development of Cartilage, 312.  Study of Cartilage, 316.


                             ARTICLE  XV.

Bone, Structure of, 317.  Growth and Development of, 324.   Accidental Ossification,
  332.  Preparation of Bone,  334. 
CONTENTS.
13
                             ARTICLE XVI.
Teeth, Structure of, 335.  Development of, 339.  Caries of, 344.  Tartar on, 345.
  Method of making sections of, 345.

                            ARTICLE  XVII.
Cellular or Fibrous Tissue, 346.  Inelastic or White Fibrous Tissue, 346.  Elastic
  or Yellow Fibrous Tissue 348  Development of Fibrous Tissue, 352.

                            ARTICLE XVIII.
Muscle, 354.  Structure of Muscle, 355.  Structure  of the Unstriped Muscular
  Fibrilla, 355.  Structure of th£> Striped Muscular Fibre, 357.  Union  of Muscle.
  with Tendon, 362.  Muscular Contraction, 363.   Development of  Muscle, 367.
  Prof. Kolliker on Unstriped Muscle, 371.  Mode of preparing for examination, 375.

                             ARTICLE  XIX.
 Nerves, 376.  Structure of, 376.  Cerebro-Spinal  System.   Secreting or Cellular
   Structure of, 376.   Tubular Structure of, 378.  Sympathetic System, 380.  Gelatin-
       Nerve, Fibres of, 380.  Structure of Ganglia, 383.  Origin and Termination
   of Nerves, 384.  Pacinian Bodies, 386.   Development and Regeneration of Nerv-
   ous Tissue, 388. Researches of M. Robin, 391. Preparation of, for examination, 394.


                               ARTICLE  xx.
 Organs of  Respiration, 395.   Aeriferous Apparatus.   Bronchial Tubes, and Air-
   Cells, 395.   Vascular Apparatus, 398.  Pathology, 399.  Mr. Ramey's views  on,
  404.  Examination of, 405.

                             ARTICLE  XXI.
 Glands, 406.   Classification of Glands, 408.   a. Follicles, 410.  Stomach Tubes, 412.
   Fallopian and Uterine  Tubes, 413.   Solitary Glands, 413.  Aggregated  Glands,
  414. B.  Sebaceous Glands, 414; comprising the Meibomian Glands,  416.  Glands
  of Hair Follicles, 416.   The Caruncula Lachrymalis,  418.  Glands of Nipple, 418,
  and Glands of Prepuce, 418.  Mucous Glands,  418;  including the Labial, Buccal,
   Lingual,  Tonsilitic, Tracheal, and Bronchial  Glands;  also, the Glands  of  the
   Uvula, Brunner's and Cowper's Glands, 418.   Brunner's Glands, 421.   Cowper's
   Glands,  421.  c  Salivary Glands, 422.  Lachrymal Glands, 423.  Mammary
   Glands, 423.  Liver, Structure of, 423.  Pathology of, 432.  Examination of, 435.
  Prostate Gland, 436.   D.  Sudoriparous Glands, 437.   Structure and examination
  of, 439.  Axillary Glands, 441.  New Tubular Gland in Axilla, Plate LVEL, fig.
  4 b.  Ceruminous  Glands, 441.  Kidneys, 442.   Secreting Apparatus of, including
  Tubes, Malpighian Bodies, and Epithelial Cells,  442.  Vascular Apparatus of, 444.
  Development of the Kidney,  449.   Pathology of,  453.  Examination of, 482. 
14
CONTENTS.
   Testis, 483.   e.  Thymus Gland, 484.  Thyroid Gland, 486 Supra-renal Capsules,
   488.  Spleen,  489.   F.  Absorbent  Glands,  492.   Villi  of  the  Intestines,  493.
   Examination of, 496.

                            ARTICLE  XXII.
Organs of  the  Senses, 497.  Touch: Papillary  Structure  of the  Skin,  497.
   Examination of, 500.  Taste: Papillary Structure  of the Mucous Membrane of
   the Tongue, 501.   Smell:  Structure of the Mucous Membrane of the Nose, 505.
   Vision:  Structure of the Globe of the Eye, 509.   Sclerotic, 509.   Cornea, 510.
   Choroid, 514.  Retina, 518.   Vitreous Body, 521.   Crystalline Lens, 522.  Dissec-
   tion of  the Eye, 533.   Hearing: Organ of, 523   External Ear, 523.  Middle
   Ear, 523.   Internal Ear, 525.

                               APPENDIX.
Pituitary Gland, 535.   Pineal Gland, 536.  Pia Mater, 537.  Pacchionian Glands,
   538.  Development of the Fat Vesicle, 538.   On the  Structure and Formation of
  the Nails, 541.  On the Ganglionic Character of the Arachnoid Membrane, 543.
   Structure  of the Striped Muscular  Fibrilla, 547.   Structure of the  Bulb of the
   Hair, 547.  Synovial Fringes, 547.   Structure of the Sudoriparous Glands, 547. 
INDEX   OF   THE  ILLUSTRATIONS,
     THE WHOLE OF THE FOLLOWING ILLUSTRATIONS  ARE
             ORIGINAL  WITH  BUT NINE  EXCEPTIONS:

                                 BLOOD,

Corpuscles of man, the red with the  centres clear, 670 diam.   .    .  Plate  i. Fig. 1
The same, the red with the centres dark, 670 diam.    ...      "    i.  "  2
The same, seen in water, 670  diam.  .    ......"    i.  "  3
The same, the red united into  rolls, 670 diam.     ....      "    i.  "  4
Tuberculated condition of the red corpuscles, 670 diam.    .    .    .    "    I.  "  5
White corpuscles of man, in water, 670 diam.     ....      "    i.  "  6
Corpuscles of frog, 670 diam.    .    .    ......"   ii.  "  1
The same, with the nucleus of the red visible, 670 diam.      .    .      "   n.  "  2
The same, in water, 670 diam.      ......."   n.  "  3
The same, after prolonged action of water, 670 diam.   ...      "   n.  "  4
Nuclei of red corpuscles of frog, 670 diam.     .    .    .    .    .    "   H.  "  5
Elongation of red corpuscles of ditto, 670 diam.     .    .    .    .      "   n.  "  6
Corpuscles of the dromedary, 670 diam.   ......"   in.  "  1
The same of the siren, 670 diam.  .......      "   m.  "  2
The same of the alpaco, 670 diam........"   ill.  "  3
The same of the elephant, 670 diam.......      "   rv.  "  1
The same of the goat, 670 diam........"   iv.  "  2
Peculiar concentric corpuscles in blood, 670 diam.  .    .    .    .      "   iv.  "  3
Coagulated fibrin, 670 diam........."   rv.  "  4
The same with granular corpuscles, 670 diam.     .    .    .    .      "   iv.  "  5
Corpuscles of earth-worm, 670 diam......."   iv.  "  6
Circulation in tongue of frog, 350 diam.^....."   v.  "  1
The same in web of the foot of ditto, 350 diam.      .    .     .    .    "   v.  "  2
Corpuscles in vessels of the same, 670 diam......      "   vi.  "  1
White corpuscles in vessels of the same, 900 diam....."   vi.  "  2
Glands of tongue of frog, 130 diam......."  vn.  "  1
Under surface of tongue of same, 500 diam.     ....."  vn.  "  2
Red corpuscles of embryo of fowl, 670 diam.       ....      "   ix.  "  1
The same, in water, 570 diam.      ......."   ix.  "  2
Red corpuscles of adult fowl, 670 diam.      .     .    .    .    .      "   ix.  "  3
The same of young frog, 670 diam........"   ix.  "  4
The same of the adult frog, 670 diam.......      "   ix.  "  5
The same united into chains, 670 diam......."   ix.  "  6 
16              INDEX  OF  THE  ILLUSTRATIONS.
              DEVELOPMENT  OF EMBRYO  OF  CHICK,

The cicatricula prior to incubation       .    •    •    •  *   •     •         e
The same at the end of first day of incubation.....
The same at the thirty-sixth hour.......
The same at the close of the second day......
The same at the end of the third day......
The embryo on the conclusion of the fourth day       .
The same at the termination of the fifth day.....
                                                                    ci    x
The embryo of six days old........
The embryo of the ninth  day of development......
The same at the end of the seventh day, detached    ....         x-
Ditto at the end of the ninth day, also detached    ....

                                   MUCUS,

Corpuscles of, in their ordinary condition, 670 diam.....          **•
The same collapsed, 670  diam........            M-
The same, showing the action of water, 670 diam.....          xl-
The same acted on by dilute acetic acid, 670 diam.     ...       "    xi.
The same after the action of undilute acetic acid, 670 diam.      .    .    "    xi.
The same in process of development, 670 diam.    ....      "    xi.
Vaginal mucus, 670 diam.........         xn-
Esophageal mucus, 670  diam........           xn-
Bronchitic ditto, 670 diam........."   *n.
Vegetation in mucus, 670 diam........       "   xu.
Mucus of stomach, 670 diam........."   xn.
Vaginal tricho-monas........."   xn.

                                     PUS.

Corpuscles of laudable pus, 670 diam......."   xm.
The same acted on by acetic acid, 670 diam.      ....       "   xm.
The same treated with water, 670 diam......."   xm.
Epithelial scales from pustule, 670 diam.     .....       "   xm.
Corpuscles from scrofulous abscess, 670 diam......"   xm.
Vibrios in venereal pus, 670 diam.       ......      "   xm.

                                     MILK.

Globules of healthy milk  of woman, 670 diam......"   xiv.
The same of impoverished human milk, 670 diam.      ...       "   xiv.
Colostrum, 670 diam.........."   xiv.
Ditto,  with several corpuscles, 670 diam......«   xiv.
Globules of large size, 670 diam.     .......«   xiv.
Ditto,  aggregated into masses, 670 diam......«   xiv.
Pus in the milk of woman, 670 diam.......«    Xv.
Blood  corpuscles in the human milk, 670 diam....."    xv.
Globules after treatment by ether, 670 diam......«    xv. 
INDEX  OF   THE  ILLUSTRATIONS.
17
 Caseine globules, 670 diam.........Plate   xv.  Fig. 5
 Milk of cow adulterated with flour, 670 diam.....      "     xv.   "  6

                                     SEMEN,

 Spermatozoa and spermatophori of man, 900 diam.       ..."    xvi.   "  1
 Spermatozoa of Certhia familiaris......"    xvi.   "  2

                                       FAT.

 The fat vesicles of a child, 130 diam......."   xvm.   "  1
 Ditto of an adult, 130 diam........"   xvm.   "  2
 Ditto of the pig, with apparent nucleus, 130 diam....."    xix.   "  1
 Ditto of the same, ruptured, 130 diam......"    xix.   "  2
 Ditto of marrow of the femur of a child, 130 diam....."    xix.   "  3
 Ditto, with the membranes of the vesicles ruptured, 130 diam.     .      "    xix.   "  4
 Crystals on human fat vesicles, 130 diam......"    xix.   "  5
 Fat vesicles in melicerous tumour, 130 .diam.      ....      "    xix.   "  6
 Ditto contained in parent cells, 120 diam......"   lxix.   " 10
 Ditto after the absorption of the parent cell-membrane, 120 diam.  .      "   lxix.   "11

                                EPITHELIUM.

 Buccal epithelial cells, 670 diam........"     xx.   "  1
 Cuneiform ditto from duodenum, 670 diam.       ....      "     xx.   "  2
 Ciliary epithelium from trachea of frog, 670 diam.   •...*'    xxi.   "  1
 Human ciliary epithelium from  lung, 670 diam.    ....      "    xxi.   "  2
 Ditto from trachea, 670 diam.       ......."    xxi.   "  3
 Tesselated epithelium from tongue of frog, 670 diam.   ...      "    xxi.   "  4
 Ditto from tongue of triton, 670 diam......."    xxi.   "  5
 Ditto from serous coat of liver,  670 diam......      "   xxu.   "  1
 Ditto from choroid plexus, 670  diam.     ....'."   xxu.   "  2
 Ditto from vena cava inferior, 670 diam......"   xxu.   "  3
 Ditto from arch of the aorta, 670 diam......."   xxu.   "  4
 Ditto from surface of the uterus, 670 diam......      "   xxu.   "  5
 Ditto from the internal surface of the pericardium, 670 diam.    .     .    "   xxu.   "  6
 Ditto of lateral ventricles of brain, 670 diam....."   xxvi.   "6e
 Ditto of mouth of menobranchus lateralis, 670  diam.       ..."   xxvi.   " 6d

                                 EPIDERMIS,

 Upper surface of epidermis, 130 diam.      ....."   xxm.   '   1
 Under surface of ditto, 130 diam........"   xxin-   "  2
 Epidermis of palm, viewed with a lens only,      ....      "   xxiv.   '   1
 Ditto, magnified 100 diam........."   XXIV-   "  2
 Vertical section of ditto, 100 diam......."   xx,v-
 Ditto of one of the ridges, 100 diam......."   XXIV-   "  4
 Epidermis from back of hand, viewed with  a lens      ...      "   ^iv-
A portion of same more highly  magnified, 100 diam.      .                 XXIV-
Epidermis from back  of haud 100 diam......      '  XXVI-  "
Ditto, viewed on its under surface, 100 diam......
Portion of ditto, with  insertion of hairs, 100 diam.      ...      '   XXVI-
                                  2 
18
INDEX  OF  THE  ILLUSTRATIONS.
 Ditto from back of neck, 670 diam.      ......Plate xxvi. Fig. 5
 Detached cells of epidermis, 670 diam......"  xxvi.  " 6 A
 Cells of vernix caseosa, 130 diam........"  xxvi-  "6b
 Cells of ditto, 670 diam........."  xxvi.  "6c

                                     NAILS,
 Longitudinal section of nail, 130 diam......."   xxv-  "   I
 Ditto, showing unusual direction of striae, 130 diam.     ...       "   xxv.  "   2
 Ditto, with different distribution of striae, 130 diam.       ..."   xxv.  "   3
 Transverse section of nail, 130 diam.......       "   xxv.  "   4
 Cells of which the layers are formed, 130 diam. and 670 diam.      .     "   xxv.  "   5
 Union of nail  with true sktn, 100 diam......"  xxvi.  "   4

                              PIGMENT  CELLS.
 Cells of pigmentum nigrum (human), 760 diam.                          "  xxvn.  "   1
 Ditto of the same of the eye of a pig, 350 diam.....       "  xxvn.  "   2
 Stellate cells of lamina fusca, 100 diam......."  xxvn.  "   3
 Ditto more highly  magnified, 350 diam......"  xxvn.  "4a
 Cells of skin of negro, 670 diam........"  xxvn.  "4b
 Ditto from lung, 670 diam.........       "  xxvn.  "4c
 Cells in epidermis of negro, 350 diam......."  xxvn.  "   5
 Ditto in areola of nipple, 350 diam......."  xxvn.  "   6
 Ditto of bulb or hair, 670 diam........" xxvm.  "   5

                                      HAIR.
 Bulb of hair, 130 diam........." xxvm.  "   1
 Root of a gray hair, 130 diam........" xxvm.  "  2
 Cells of outer sheath, 670 diam........       " xxvm.  "  3
 Portion  of inner sheath, 350 diam........" xxvm.  "  4
 Stem of gray hair of scalp, 350 diam.......       "  xxix.  "   1
 Transverse section of hair of beard, 130 diam.      .-..."  xxix.  "  2
 Another section of the same, 130 diam......«  xxix.  "  3
 Fibres of the stem of the hair, 670 diam.       ....."  xxix.  "  4
 Apex of hair of perineum, 350 diam.......       «  xxix.  "  5
 Ditto of scalp, terminating in fibres, 350 diam......"  xxix.  "  6
 Ditto of same with needle-like extremity, 350 diam.    ...       "  xxix.  "  7
 Root of hair of scalp, 130 diam........«  xxix.  "  8
 Another form of same, 130 diam........       «  xxix.  "  9
 Hair with two medullary canals, 130 diam......«  xxix.  " 10
 Insertion of hairs in follicles,  100 diam......«   xxvi.   "  3
 Disposition of hairs on back of hand.......«  xxiv.  "   5

                                CARTILAGE.

 Transverse section of cartilage of rib, 350 diam.....       «   XXx.  "   1
Parent cells seen in section of ditto, 350 diam.      .     .    .    .     "   xxx.  "   2
Vertical section of articular cartilage, 130 diam.....       «   Xxx.  "   3
Ditto of inter-vertebral cartilage, 80 diam......«   xxx.  "   4
Cartilage of concha of ear, 350 diam.......       «   xxxi.  "   1 
INDEX  OF  THE  ILLUSTRATIONS.
Cells of inter-vertebral cartilage, 350 diam.
Section of cartilage and bone of rib, 130 diam.
Ditto of one of the rings of the  trachea, 350 diam.
Ditto of thyroid cartilage with fibres, 130 diam.
Cartilage of ossification, 100 diam.
Section of primary cancelli, 350 diam.
Ditto of same, more advanced,  350  diam.
Cartilage of ossification, 350 diam.
Section of cartilaginous epiphysis, 30 diam.
Ditto of same, with bone, 30 diam.
Ditto of same, more highly magnified, 330 diam.
Section of cartilage and bone of rib, 130 diam.

                                     BONE.
Transverse section of ulna, 60 diam.
Cross-section of Haversian canals, 220 diam.
Ditto of same more highly magnified, 670 diam
Longitudinal section of long bone, 40 diam.
Parietal bone of foetus, 30 diam.
Portion of same more highly magnified, 60 diam.
Spicula of bone of fcetal humerus, 350 diam.
Lamina of a long bone, 500 diam.
Cancelli of long bone of fetus,  350  diam.
Section of femur of pigeon fed on madder, 220 diam.
Section of epiphysis  and shaft of fcetal femur,  100 diam
Transverse section of primary cancelli, 350 diam.
Section of cancelli more advanced, 350 diam.
Ditto of epiphysis and shaft of fetal femur, 350 diam.
Ditto of cartilaginous epiphysis  of humerus, 30 diam.
Ditto of same with bone, 30 diam.
The same more highly magnified, 330 diam.
Blood-vessels and medullary cells    ....
Section of shaft of fcetal long bone,  20 diam.
Ditto of bone and cartilage of rib, 130 diam.
                                    TEETH,
Vertical section of incisor tooth, seen with lens
Tubes of dentine near their termination, 670 diam.
A not unfrequent condition of same, 670 diam.
Tubes of dentine near their commencement, 670 diam.
Oblique  section of tubes of dentine, 670 diam.
Transverse section of ditto, 670 diam.  .
Transition of tubes into bone cells, 670 diam. .
Dilatation of ditto into bone cells, 670 diam.
Section of cementum, 670 diam.
Ditto  of same traversed by tubes, 670 diam.
Ditto  of same showing angular cells, 670 diam.
Fungus on section of dentine, 670 diam.
Oil-like  globules on section of same, 350 diam. 
20              INDEX  OF   THE  ILLUSTRATIONS.

Section of secondary dentine, 350 diam......P^te xxxvu. Fig. 6
Ditto of bicuspid tooth, seen with lens only....." xxxvn.
Vertical section of enamel, 220 diam.......       " xxxix.
Enamel cells seen lengthways, 670 diam......" xxxix.
Cross-section of cells of enamel, 670 diam.      .                       '' xxxix.

                            FIBROUS   TISSUE.
Longitudinal section of tendon, 670 diam......" xxxix.
Transverse section of same, 670 diam.     ....." xxxix.      £
White fibrous tissue, 670 diam........" XXXIX-   "  6
Mixed ditto,  670 diam.........      " XXXIX-   "'  ]
Yellow fibrous tissue,  670 diam........"     XL-   '   1
Different form of ditto, 670 diam......."     xi..   "  2
Development of blood-vessels, 350 diam.      ....."     xl.   "  3
Areolar form of mixed fibrous tissue, 330 diam.....       "     xl.   "  4
Blood-vessels of pia mater, 350 diam.    ......"     xl.   "  5
Development of white fibrous tissue, 670 diam.  ....       "   xliii.   "  2
Portion of dartos, 670 diam........."   xliii.   "  3
Section of corpora cavernosa, slightly magnified  ....       "   xliii.   "  4

                                    MUSCLE.
Portion of striped muscle, 60 diam.      ......"    xli.   "  1
Fragment of unstriped ditto, 670 diam.     .....       "    xli.   "  2
Muscular fibrillar of the heart, 670 diam......"    xli.   "  3
Fragment of striped muscle of frog, 350 diam.....       "    xli.   "  4
Fibres and fibrillae of  voluntary muscle,  350 diam....."    xlii.   "  1
Fibres acted on by  acetic acid, 350 diam.   .....       "    xlii.   "  2
Ditto in different degrees of contraction, 350  diam.      ..."    xlii.   "  3
Union of muscle with tendon, 130 diam.   .....       "    xlii.   "  4
Transverse section  of muscular, fibres, 350 diam.   .     .     .     .     "    xlii.   "  5
Fibres of voluntary muscle of fetus, 660 diam.  ....       "   xliii.   "  1
Zigzag disposition of fibres, 350 diam.   ......"   xliii.   "  5
Striped muscular fibre and fibrillae, 670  diam.    ....      "   xliii.   "  6

                                    NERVES.
 Tubes of motor nerve, 670 diam.   ......."   xliv.   "  1
 The same after the action of spirit, 670  diam.   ....       "   xliv.   "  2
 The same after the action of acetic acid, 670  diam.      ..."   xliv.   "  3
 Portion of Casserian  ganglion, 350 diam......       "   xliv.   "  4
 Nerve tubes of cerebellum, 670 diam.  .......   xliv.   "  5
 Ditto of cerebrum, with clear cells, 670 diam.....       "   xliv.   "  6
 Varicose condition of ditto, 670 diam.   ......"   xliv.   "  7
 Filaments of great sympathetic, 670 diam......       ««    xlv.   "   1
 Cells of gray matter  of cerebellum, 670 diam.     .     .     .     .     "    xlv.  "  2
 Ditto of same, inner stratum, 670 diam......       "    xlv.  "  3
 Caudate ganglionary cells, 350 diam......."    xlv.  "  4
       (Spinal cord, Medulla oblongata,  Cerebellum.)
 Ditto from locus niger of cms cerebelli, 350 diam.      ...       "    xxv.  "   5 
INDEX  OF  THE   ILLUSTRATIONS.
Ditto from hippocampus major, 350 diam.
Ditto from locus niger of crus cerebri, 350 diam. .
Pacinian bodies, natural size.....
Ditto, magnified 60 diam......
A single Pacinian body, 100 diam.
An anomalous Pacinian body    ....
Two other anomalous Pacinian bodies
Cells from corpus dentatum of cerebellum, 350 diam.
Plate xlv.
 "    XLV.
 "    XL VI.
 "    XLVI.
 "    XLVI.
 "    XLVI.
 "    XLVI.
 "    XLVI.
                                      LUNG.
Pleural surface of lung, 30 diam........"   xlvh.
Ditto, with vessels of first order, 30 diam......       "   xlvii.
Ditto, magnified 100 diam.........."   xlvii.
Section of lung injected with tallow, 100 diam.....       "  xlviii.
Casts of air-cells, 350 diam.   ........"  xlviii.
Section of lung injected with size, 100 diam.     ....       "  xlviii.
Pleural surface of lung, with vessels of second order, 100 diani.     .     "   xlix.
Section of lung, with air-cells uninjected, 100 diam.   ...       "   xlix.
Capillaries of lung, 100 diam........"   xlix.
                                     GLANDS,
 Follicles of stomach, with epithelium, 100 diam.
 Ditto of large intestine, in similar condition, 100 diam
 Ditto of same, without epithelium, 60 diam.
 Termination of follicles of large intestine, 60 diam.
 Follicles of Leiburkiihn in duodenum, 60 diam.   .
 Vessels of ditto of appendix vermiformis, 100 diam.
 Ditto of same  of stomach of cat, 100 diam.
 Stomach tubes, cross-section of, 100 diam.
 Longitudinal view of stomach tubes, 220 diam.   .
 Ditto of the same, 100 diam.       ....
 Villi of small intestine, with epithelium, 100 diam.
 Ditto, without  epithelium, showing  lacteals, 100  diam.
 Vessels of villi in duodenum, 60 diam.
 Ditto of same in jejunum, 60 diam.
 Ditto of same of foal, 60 diam.  ....
 Solitary glands of small intestine, natural size
 Ditto of large intestine, slightly magnified .
 Aggregated or Peyer's glands, 20  diam.
 Side view of same, 20 diam.    ....
 Sebaceous glands in connexion  with hair, 33 diam.
 Ditto from caruncula Iachrymalis
 An entire  Meiboviian gland, 27 diam.  .
 Illustrations of  Mucous  glands, 45 diam.
Parotid gland  of embryo of sheep, 8 diam.   .
Ditto of human subject, further developed, 40 diam.
Mammary gland, portion of, slightly magnified
Ditto of same, with milk globules, 90 diam.
   L.
 LII.
 LII.
  LI.
  LI.
  LI.
LXU.
  LI.
 LII.
 LII.
LIII.
LIU.
LIII.
LIII.
LIV.
LIV.
LIV.
LIV. 
22
INDEX  OF   THE  ILLUSTRATIONS
 Ditto of same more highly magnified, 198 diam.
 Liver, section of, showing the lobules, 35 diam.  .
 Surface of ditto, showing  the intra-lobular veins, 15 diam.
 Section of liver showing the hepatic venous plexus, 20 diam
 Vessels of portal system, 20 diam.       ....
 Section of liver, showing inter-lobular vessels, 24 diam.
 Surface of liver, showing portal capillary system, 20 diam.
 Ditto, showing both hepatic and portal venous systems, 20
 Ditto, with both systems completely injected, 20 diam.
 Ditto, with portal vein and hepatic artery, 18 diam.
 A terminal biliary duct, 378 diam.  .
 Secreting cells of liver in healthy state, 378 diam
 Ditto, gorged with bile, 378 diam.
 Ditto, containing oil globules, 378 diam.
 Prostate gland, calculi of,  45 diam.
 New tubular gland in axilla, 54 diam.
 Tubulus of ditto, 198 diam.....
 Ceruminous glands, portions of, 45 diam.  .
 Sudoriferous gland, tubulus of,  198 diam.
 Kidney, tubes of, with epithelium, 99 diam.
 Cross-section of elastic  frame-work, 99 diam.  .
 Ditto of frame-work and tubes, 99  diam.
 Section of vessels in tubular part of kidney, 33 diam.
 The same  vessels seen lengthways, 33 diam.
 Tubes with epithelium, 378 diam.  ....
 Corpora Malpighiana of kidney, injected, 40 diam.
 Uriniferous tubes of a bird, 40 diam.
 Corpora Malpighiana of the horse, 40 diam.
 Inter-tubular vessels of surface of kidney, 90 diam.
 Transverse section of injected kidney, 67 diam.
 Uninjected corpora Malpighiana   ....
     With capsule, 100 diam.....
     Without ditto, 100  diam.....
 Malpighian body, more highly magnified, 125 diam.
 Afferent and efferent vessels of Malpighian tuft, 45 diam
 Epithelial cells of the tubes, 378 diam.
 Testis, tubes of, 27 diam......
 Tubes of ditto, more highly magnified, 99 diam.
 Vessels of thyroid gland, injected, 18 diam.  .
 Vesicles of ditto, viewed with a lens only  .
 Ditto of same, magnified 40 diam.
 Ditto of same, showing the  structure of their walls, 67 diam
 Lobes and vesicles of same  in their ordinary condition, 27 di
 Nuclei of vesicles of  thyroid, 378 diam.    .
Follicles of thymus, with vessels, 33 diam.
Capsule of  ditto, 54 diam......
Nuclei and simple cells of same, 378 diam.
Compound  or parent cells of ditto, 378 diam.
Spleen, nuclei and vessels of, 378 diam. .
diam.
Plate liv.		Fig. 6
"	LIV.	" 4
"	LV.	" 1
"	LV.	" 2
(C	LV.	" 3
f<	LV.	" 4
"	LV.	" 5
"	LVI.	« 3
"	LVI.	" 4
t<	LVI.	" 2
"	LVII.	" 1
"	LVII.	"2a
"	LVII.	"2b
"	LVII.	" 2c
U	LVII.	" 3
u	LVII.	"4a
"	LVII.	" 4b
l(	LVII.	" 5
"	LVII.	" 4c
t(	LVIII.	" 1
"	LVIII.	" 2
"	LVIII.	" 3
tt	LVIII.	" 4
(t	LVIII.	" 5
"	LVIII.	" 6
"	LXIX.	" 1
f<	LIX.	" 2
"	LIX.	" 3
"	LIX.	" 4
"	LIX.	" 5
f<	LX.	" 2 " A
"	tc	" B
"	LX.	"3a
It	LX.	"3b
"	LX.	"3c
tl	LX.	" 1
u	LX.	" 4
"	LXI.	" 1
"	LXI.	" 2
"	LXI.	" 3
"	LXI.	" 4
cc	LXI.	" 5
K	LXI.	" 6
«	lxi:	" 7
((	lxi:	" 8
H	lxi:	" 9
«	lxi:	" 10
«	lxii:	" 1
 
INDEX   OF  THE  ILLUSTRATIONS.
Supra-renal capsule, plexus on surface of, 54 diam.  .    .    .     Plate  lxii.
Tubes of ditto, 90 diam........."     lxii.
Nuclei, parent cells, and molecules of ditto, 378 diam.     .     .       "     lxii.
Vessels of supra-renal capsule, 90 diam......"     lxii.
Pineal gland, compound bodies of, 130 diam.....       "     lxix.
Pituitary gland, cells and fibrous tissue of, 350 diam.   ..."     lxix.

              ANATOMY  OF   THE  SENSE   OF  TOUCH,
Epidermis of palm of hand, 40 diam......"     lxiii.
Ditto of back of hand, 40 diam........"     lxiii.
Papillae of palm of hand, 54 diam.......       "     lxiii.
Ditto of back of hand, 54 diam.......          "     lxiii.
Epidermis of palm, under surface of, 54 diam.....       "     lxiii.
Ditto of back of hand, under surface of, 54  diam....."     lxiii.
Vessels of papillae of palm of hand,  54 diam.....       "     lxiii.
Ditto of same of back of hand, 54 diam......"     lxiii.

              ANATOMY  OF   THE  SENSE   OF  TASTE.
Filiform papillae, with long epithelial appendages, 41 diam.     .       "     lxiv,
Ditto, with shorter epithelial processes, 27 diam....."     lxiv.
Ditto, without epithelium, near apex of tongue, 27 diam.  .    .       "     lxiv.
Ditto, without epithelium, near centre of same, 31 diam.     .     .     "     lxiv.
Filiform and fungiform papillae, without epithelium, 27 diam.   .       "     lxiv.
Peculiar form of compound papillae, 27 diam.      .     .     .     .     "     lxiv.
Filiform papillae in different states, 27 diam.....       "     lxiv.
Ditto, with epithelium partially removed,  27 diam.      ..."     lxiv.
Follicles of tongue, with epithelium, 27 diam.....       "     lxv.
Ditto, without epithelium, 27 diam.     ......"     lxv.
Ditto, viewed as an opaque object, 27 diam.....       "     lxv.
Filiform papillae from point of tongue, 27  diam....."     lxv.
Follicles and papillae from side of  ditto, 20 diam.     ...       "     lxv.
Simple papillae, with epithelium, 45 diam......"     lxv.
Filiform papillae, with ditto, 18 diam......"     lxv.
The dame, viewed with a lens only......"     lxv.
Side view of certain compound papillae, 20 diam.    ...       "     lxv.
Simple papilla from under surface  of tongue, 54 diam.   ..."     lxv.
Compound and simple ditto from side of tongue, 23 diam.      .        "     lxv.
A calyciform papilla, uninjected, 16 diam......"    lxvi.
Ditto, with the vessels injected, 16 diam......        "    lxvi.
Filiform  papillae near centre of tongue, injected, 27 diam.    .    .     "    lxvi.
Ditto near tip of tongue, injected,  27 diam....."    lxvi.
Simple papillae, injected, 27 diam......."     lxvi.
Fungiform ditto, injected, 27  diam.......        "    lxvi.

           ANATOMY   OF  THE  GLOBE   OF  THE  EYE.
Vertical section of cornea, 54 diam......."    lxvii.
A portion of retina, injected,  90 diam......       "    lxvii.
Section of sclerotic and cornea, 54 diam......"   lxvii. 
24
INDEX  OF   THE  ILLUSTRATIONS.
Vessels of choroid, ciliary processes, and iris, 14 diam.
Nuclei of granular layer of retina, 378 diam.
Cells of the same, 378 diam......
Ditto of vesicular layer of  retina, 378 diam.
Caudate cells of retina, 378 diam.....
Cells of the membrana Jacobi, 378 diam.
Fibres  of the  crystalline lens; a, 198 diam.;  b, 378 diam.
A condition of the posterior elastic lamina, 78 diam.
Peculiar markings on same, 78 diam.
Crystalline  lens of sheep, slightly magnified
Fibres  of lens near its centre, 198  diam.  .
Stellate pigment in eye of sheep, slightly magnified
Venae vorticosae of eye  of sheep, injected
Conjunctival epithelium, oblique view of, 378 diam.
Ditto, front view of, 378 diam.      ....
Ciliary muscle, fibres of, 198  diam.....
Gelatinous nerve fibres of retina, 378 diam.
Cellated structure of vitreous body, 70 diam.
Fibres  on posterior elastic lamina, 70 diam.
Portion of the iris, 70 diam.     .....
Epithelium  of crystalline lens, 198 diam. .
Ditto of the aqueous humour, 198  diam.
Hexagonal  pigment of the choroid, 378 diam. .
Stellate pigment of same, 378 diam.  ....
Irregular pigment of uvea, 378 diam.
Plate	LXVII.	Fig. 4
"	LXVII.	" 5
* u	LXVII.	" 6
tt	LXVII.	" 7
a	LXVII.	" 8
a	LXVII.	" 9
St	LXVII.	" 10
tt	LXVII.	" 11
tt	LXVII.	« 12
"	LXVII.	" 13
u	LXVII.	" 14
It	LXVIII.	" 1
((	LXVIII.	" 2
(l	LXVIII.	" 3
u	LXVIII.	" 5
"	LXVIII.	" 4
"	LXVIII.	" 6
tt	LXVIII.	" 7
it	LXVIII.	" 8
"	LXVIII.	" 9
it	LXVIII.	" 10
tt	LXVIII.	" 11
si	LXVIII.	" 12
u	LXVIII.	" 13
u	LXVIII.	" 14
                      ANATOMY   OF  THE   NOSE
Mucous membrane of true nasal region, 80 diam.
Ditto of pituitary region, injected, 80 diam."   ....
Capillaries of olfactory region of human fetus, 100 diam.
lxix.  "  1
lxix.  "  2
lxix.  " 12
                        ANATOMY  OF   THE   EAR
Denticulate laminae of the osseous zone, 100 diam.  .
Tympanic surface of lamina spiralis, 300 diam.
Inner view of cochlearis muscle of sheep .....
Plexiform arrangement of cochlear nerves in ditto, 30 diam.

                                     VILLI.
Villi of fetal placenta, injected, 54 diam.      ....
Ditto of choroid plexus, 45 diam......
LXIX.	"	3
LXIX.	"	4
LXIX.	tt	5
LXIX.	tt	6
LXII.	tt	4
LXIX.	tt	9
  Plates VIII., XVIL, and  XXXVIII., omitted  in  the  original edition, are likewise
here omitted.  The same numbers for the other plates are observed, that the figures
in both editions may correspond.
  The Plates added to the American Edition commence at Plate LXX. 
PLATES    ADDED
THE   AMERICAN   EDITION
Corpuscles of lymph, 800 diam.......Plate  lxx.
Corpuscles of chyle, 800 diam.         ......         LXX-
Fat vesicles, injected, 45 diam.  .......           LXX-
Transverse sections of hair, 450 diam......."    LXX-
Cartilage from finger-joint, 80 diam.......           LXX-
Vessels of synovial membrane, 45 diam.......         lxx.
Injected matrix of finger-nail, 10 diam......           hxxi.
Vessels of tendon, 60 diam.........        lxxii.
Ditto nearer muscular union, 30 diam......          lxxii.
Lymphatic gland and vessels, 8 diam.......(  lxxiii.
Capillaries and air-cells of fetal lung, 60 diam.....      "  lxxiii.
Ditto of same of child, 60 diam........'  lxxiii.
Ditto of same of adult, 60 diam.......       '  lxxiii.
Branchia of an eel, 60 diam.........'  LXXI»
Mucous membrane of fetal stomach, 60 diam.       .     .     •         lxxiv
Ditto, showing cells and cap. ridges of adult, 60 diam.   .     .     .       lxxiv
Ditto with cells deeper and ridges more  elevated, 60 diam.  .     .         lxxiv
Ditto showing gastric villi, 60 diam.     .        ....       lxxiv
Villi of duodenum, 60 diam........         LXXIV
Ditto of jejunum, 60 diam.........       LXXIV
Ditto of ileum, 60 diam.   .    .......           IjXXV
Muscular fibre of small intestine, 60 diam......         LXXV
Appendix vermiformis, 60 diam.......
Mucous follicles of colon, 60 diam.......         LXXV
Malpighian bodies with uriniferous tubes, of adult, 100 diam.     .           lxxv
Ditto enlarged as in Bright's disease, 100 diam.....         LXXV
Enlarged veins of kidney, first stage of  Bright's disease, 100 diam.        lxxvi
Ditto of same, another view, 100 diam......          LXXVI
Stellated veins in third stage of same, 100 diam.....        LXXVI
Granulation on the surface of kidn :y, 100 diam.      ...      «*   lxxvi
A tube much dilated, 100 diam........
Sudoriparous glands and their ducts, 70 diam.....         lxx mi
Ditto, more highly magnified, 220 diam...... 
26
INDEX  OF  THE  ILLUSTRATIONS
Mucous membrane of gall-bladder, 50 diam.
Transverse section of muscles of the tongue, 45 diam.
Terminal vessels in cornea, 45 diam.
Cornea of viper, showing its vessels, 45 diam.
Choroid coat of fetal eye, 45 diam.....
Ciliary processes of eye of adult, 45 diam.
Mucous lining of unimpregnated uterus, 35 diam.
Ditto of impregnated uterus, 35 diam.  .
Tuft of placenta, 60 diam......
Papillae of gum, 45 diam......
Ditto of lip, 45  diam.......
Blood-vessels in mucous membrane of trachea, 45 diam.
Ditto of buccal  membrane, 60 diam.
Ditto of mucous membrane  of bladder, 60 diam.  .
Plate	LXX VII
"	LXXVII
"	LXXVIII
"	LXXVIII
tt	LXXVIII
"	LXXVIII
"	LXXVIII
(t	LXXVIII
"	LXXIX
tt	LXXIX
"	LXXIX
(t	LXXIX
"	LXXIX
"	LXXIX
 
INTRODUCTION.
BY THE  EDITOR.
  The object of the present Introduction is to furnish some  practical hints
on Manipulation  in  Microscopic  Anatomy, so that  the student who is dis-
posed to pursue for  himself this subject, and has not at his command other
authorities, may be provided with the information  necessary to commence
his investigations.
  Although plates  and models are useful as companions in study, and as
giving more explicit views of authors than  can be done  in words, yet  as
these, however excellent, can never  make  the  student master of special
anatomy without  dissection, so in the  more intricate department of minute
anatomy,  he who would there become a proficient,  must  investigate for
himself.
  The same remarks apply in a manner to specimens prepared by others:
these seldom receive that close study  and  repeated  investigation which are
willingly given to one's own attempts.   The very  admirable  preparations
of different  tissues by Hett, Topping, Darker, and others, which may now
be purchased of many opticians, should be rather regarded as standards of
success, with which  the student may compare his own efforts, than as sub-
stitutes for his own manipulation.
  For distinctness, it is proposed to treat the subject under three divisions:

            I. Microscopes and their Accessory Instruments.
          II.  The Preparation of Objects.
          III.  The Preservation of Objects.

       I. OF  MICROSCOPES   AND  THEIR ACCESSORIES.
  It will not  fall within the design of this  introduction, to treat either of
the theory of the microscope, or its  construction.   A brief description of
the various forms in present use is all that will be necessary.    k
  Those only who have studied with the microscope, know the comfort and
satisfaction of using a good one;  and  by this is  meant excellence not only 
28
INTRODUCTION.
in object-glasses, although these are the most essential to a good microscope,
but  excellence in  all the details of accessory instruments,  and in nice
mechanical adjustment.
   It is a very common error to suppose that cheap microscopes will answer
as well for low powers as more expensive ones: that, for instance, there is
no difference in a one-inch object-glass and common eye-piece of an ordi-
nary microscope, and the same focus object-glass and  eye-piece of a good
instrument: hence  many persons, about commencing  the  study of micro-
scopic  anatomy, and believing that, for the study of injected preparations, a
power  of one hundred diameters will in most cases answer,  purchase the
cheapest instrument they can  obtain, with that degree of magnifying power,
unaware that penetration and  definition are qualities  that, an object-glass
needs,  even more than mere  magnifying power—qualities  that are rarely
found to exist in any degree in  the cheaper microscopes.
  It is  in these qualities that  the English and American  instruments excel
the French and other continental microscopes: an observer with the former
being able actually  to see more of,  and see better, the  construction of an
object with a glass  of much lower magnifying  power:  the object  being in
the latter case clear and well defined, while in the other, though more highly
magnified, blurred and indistinct with poor illumination.   It is  a great satis-
faction in viewing an object with a microscope to  be  able to see it as well
as any one has hitherto seen it: if not able to do this, one always feels at a
disadvantage.
  An error, somewhat similar, committed by beginners, is in supposing that
a low-priced microscope (and usually therefore a poor one) is sufficiently
good to commence  with, and that a more perfect  instrument with higher
powers  may be purchased when more familiar with its use.  This is not
only poor economy,  but, as already stated, such an instrument gives unsatis-
factory and often false views: it being much better economy where this is
regarded,  and  infinitely more satisfactory, to purchase  a good instrument
with low powers at a fair price, to which the higher powers may be added
as means  allow.  Those who can afford a good microscope, and yet pur-
chase a poor one, commence their  studies under great disadvantages.
  It must not be forgotten, however, that in  microscopic  observation, more
depends on the observer than upon  the  instrument;  more upon the practised
eye, and the analytical mind, than upon the precise  form  of the microscope
or the number of  its accessories.
  The following brief enumeration of the different  prominent microscope-
makers may be of service to  persons at a distance about  to  order a micro-
scope,  and who are embarrassed by the number  of manufacturers, and
uncertain about the  expense.
  At the  present time, the most elaborate and completely furnished micro- 
MICROSCOPES,  ETC.
29
scopes are those of English, and especially of London manufacture.   A full
account of the various forms by the three principal London makers, is given
by Mr. Quekett in his "Practical Treatise on the Microscope."   He, how-
ever, does not give  preference to either.—Mr. A. Ross, No.  2 Featherstone
Buildings, Holborn, London,  is usually considered the most prominent of
the London makers, having done more by his contributions to the literature
of the microscope, and his  various improvements in its form and  accessory
apparatus, than  either of the other makers.   His best or largest microscope
has been  considered to be  unsurpassed by any in the world.  Its price  in
London, when complete, is about $450;  the duty on importation into this
country being 30  per cent,  ad valorem.   As has  been  mentioned  in  the
preface to the  English edition of the  present work, most  of the objects
represented, are engraved  as viewed with one of Mr. Ross's microscopes.
Mr. Ross makes  several  forms  of instruments, among which the most
reasonable in price, and convenient for use,  is one described in the  Penny
Cyclopedia, article "Microscope."
   This instrument, with object-glasses as high as |th-inch,* with the usual
accessory instruments, may be obtained in England for about $175.
   Messrs. Powell and Lealand, No. 4 Seymour-place, Easton-square, Lon-
don, have of late years almost, if not quite, equalled  Mr.  Ross in  the excel-
lence of their microscopes, and also construct several forms.  One  of the
steadiest and most convenient is  the second size described by Mr. Quekett,
on  page 77 (figure 44) of  his "Practical  Treatise."
   The price of this instrument complete is about $350  in  London, and to
those desiring a high-priced instrument the writer can  safely recommend
t,his one, as combining great steadiness, accuracy of  adjustment, and excel-

 ' * Note.—As these fractions of an inch—£th,  ]th,  -J^th, &c.—as applied to the
focus of object-glasses, constantly recur in this introduction and elsewhere, it should
be stated that these measurements do not represent the actual distance between the
object and the object-glass in each  particular case, but are used to  signify what the
distance would be, if a single lens were used possessing the same magnifying power,
instead of a combination (most object-glasses being composed of three lenses instead
of a single one, and called a  triplet) : in other words, a single  lens, to  produce the
same magnifying power as a ^th-inch triplet, would have to be a lens  of Jth-inch
focus.  This nomenclature is unfortunate, because many are  misled by it.  It is,
however, in general use in England and in this country.  The following  table gives
the magnifying powers in diameters of Mr. Ross's  object-glasses with the different
eye-pieces.  The objectives of other makers do not vary much from these:
                          OBJECT-GLASSES.
           EYE-GLASSES.
    A. or long eye-piece, . .
    B. or middle eye-piece, .
    C. or short eye-piece,. .
2-IN.	1-IN.	fnr.	|-IN.	J-IN.	A-»-
20	60	100	220	420	600
30	80	130	350	670	870
40	100	180	500	900	1400
 
30
INTRODUCTION.
 lence in object-glasses.  It is a most luxurious instrument to  use.   Powell
 and Lealand construct another microscope, having the supports of the com-
 pound body and the stage made of iron.  This mounting of course consider-
 ably reduces  the  expense, but does not diminish its value as an efficient
 instrument.  In this form the lever-stage is usually employed, and a micro-
 scope of this description, with object-glasses as high as ith, may be imported
 for about $100; but this sum does not include any of the expensive accesso-
 ries, such as the achromatic condenser or camera lucida.  Powell and Lea-
 land  have sent several of these instruments  to this country, and they have
 given great satisfaction.
   Messrs. Smith and Beck, No. 6 Coleman-street (city), London, though less
 prominent than either of the preceding  makers, construct  several  excellent
 microscopes; one  especially, known as the "Student's Microscope," is highly
 to be  recommended on  account of its reasonable price; being furnished
 complete with all the accessories for about $200, and combines great steadi
 ness and convenience in  use.   The same instrument with plain  stage and
 object-glasses  as high as Ath, but without the accessories,  may be had  in
 London for $75.
   Of the French microscope-makers the most prominent have hitherto been
 M. Chevalier (163 Palais Royal, Paris,) and  George Oberhauser.  Cheva-
 lier's instrument is of the horizontal form, but capable of being  converted
 into the vertical or the inclined one.   Though the microscope-stand  and
 apparatus are of good construction,  the object-glasses  are  usually defective
 in definition: such at least is the character of most of those imported in this
 country.  The horizontal form, recommended by Sir David  Brewster as
 being the best adapted  for accurate  observation, is to many  persons fatiguing
 to the eye; and the image of the object being a reflected one, it would appear
 as if some sharpness of outline must be lost by the reflection.   The price of
 one of Chevalier's best instruments in Paris is about $200.   The accessory
 apparatus is not so complete as with the English instruments.
   A smaller size, similar in construction, and usually  known as the "small
 Chevalier," can be obtained at about half the  price of the preceding instru-
 ments ; it is not, however, so complete in object-glasses or accessories.
   The form that  Mr. Oberhauser (No. 19 Place Dauphine,  Paris,) adopts is
the vertical one1; a form of construction  at once the cheapest and least com-
plicated.   His microscopes, though often ordered from this country, and much
used on the continent of Europe, have two  important faults; the first  in
common with M. Chevalier's, want of definition and penetration in the object-
glasses, and the second, inconvenience of mechanical arrangement, especially
in the means of illumination; the mirror always being too  small, and inca-
pable  of affording oblique light.   M. Oberhauser seems to rely more on his
short  eye-pieces  for increasing the magnifying power, (there sometimes 
MICROSCOPES,  ETC.
31
being five or six of these furnished with his microscope,) than upon his object-
glasses ;  a great mistake, and always attended by loss of light and definition.
The more one studies with the microscope, the more one learns to rely on the
object-glass for power and less on the eye-piece; objects being rarely seen
so clearly, and therefore not so well, with a very  short eye-piece as with one
from two to three inches long.   Views of objects afforded by M. Oberhau-
ser's combination of object-glass and  short eye-piece, producing according
to his own table a magnitude of 900 diameters, are far  less satisfactory, and
show less of minute structure, than the same object seen with an English £th
object-glass and long eye-piece, producing a magnitude of not more than
220 diameters.  A microscope is furnished by M. Oberhauser at about six
months' notice for $100, with a power according  to his own measurement of
900 diameters.
   At present, the best French microscope-makers  are  M. Nachet and M.
Brunner, both of Paris.  The microscopes of Nachet (Rue Serpente, No. 16,)
much resembles in general form and arrangement the large-sized instru-
ments of M.  Oberhauser, their  excellence consisting in  the  superiority of
their object-glasses: they are much employed in microscopic investigations
in Paris, and  are  good working instruments; the prices are about the same
as Oberhauser's,  but the object-glasses are every way superior.
   His largest sized  instrument, complete, is sold in Paris at 650 franes.   His
smallest size, at 100 francs: between  these, are  several intermediate sizes.
   The  microscope  of M. Brunner (Rue des  Bernardins, No. 34, Paris,)  is
also a vertical one, but possesses more advantages  of mechanical arrangement
than any other of the same construction;  indeed, it almost equals the more
expensive form usually  adopted in England, for convenience of arrangement
and facility in use.  The stage is large, and has  not only a circular motion,
but also two lateral motions, made by adjusting-screws; the mirror is large,
and admirably arranged for affording  oblique  light.   The  object-glasses
supplied with this instrument are excellent, and for sharpness of definition
and light, are hardly surpassed by the best English  ones.   M. Brunner
also supplies  the  achromatic condenser, the polarizing  apparatus, and other
accessories, to those who wish them;  and his  prices for his best instruments
vary from $90 to $150, according to  the  powers of  the  object-glasses and
accessories furnished.   The writer has no hesitation in  recommending these
microscopes as the best of the vertical form, possessing, as already mentioned,
more advantages of mechanical arrangement  than any other, and the object-
glasses are not excelled by any of continental make.
  The rapid  advances made of late years  in microscopic knowledge, have
been  owing,  in a great measure, to  improvements  in the construction of
object-glasses.  To this end, perhaps nobody has  contributed so much as
Mr. Charles  A. Spencer, of Canastota, New-York.  The objectives made 
32
INTRODUCTION.
 by this gentleman may safely bear comparison with the best of foreign
 make, and for sharpness of definition, power of penetration, and large angle
 of aperture, are not excelled by  any in the world.  As has been already
 stated, much of the excellence of an object-glass depends on its power of
 penetration:  this, again, depends in a great measure on  the angle of aper-
 ture by which the rays of light from the object enter the glass.   It must be
 evident that the greater the angle, the larger must be  the  pencil of rays.
 Mr.  Spencer has made  some valuable experiments on this subject, and  has
 been enabled to obtain a curve for his object-glasses, by  which in the ^th-
 inch, he can give an angle of aperture of 160°.  This is believed to be the
 largest  angle ever given to an object-glass: the greatest obtained by Mr.
 Ross, was, for a TVth,  an angle of 135°, and the  one usually given to
 object-glasses of the same focus by the best foreign makers, not greater than
 120°.   In  Mr. Spencer's ith-inch  object-glass, the angle of aperture is 85° ;
 in the ith-inch, 135° ; in the objectives of foreign make, according  to Mr.
 Quekett, the angles are  for the ith-inch, 63°,  and the |th-inch, 80°.
   To Mr. Spencer is due the credit of having first resolved, with lenses of
 his own construction, the fine markings on  the  Navicula Spencerii  and
 Grammatophera Subtillissima: these minute shells have  since been adopted
 by microscopists  as test-objects for the  highest powers.   The Navicula
Spencerii, will  exhibit one set of lines with Mr. Spencer's ith-inch object-
glass :  both sets with the |th-inch.  The Grammatophera Subtillissima is
 a good test for a rljih or TVth.
   Of several microscopes made by Mr. Spencer, two or three only will be
here noticed.   His first-class or best instrument is mounted on trunnions,
 and  embraces  all the   acknowledged improvements, in  form and  stage,
 whereby the  greatest steadiness  and freedom from tremour are secured.
The  price of this  instrument,  with all the accessories  and full sets of object-
 glasses, will approach $350.
   The second-class instruments, complete as to object-glasses and accesso-
ries,  but mounted less expensively, cost from $200 to $250.
   A  very efficient microscope, is one known as the " Pritchard form:"  this
instrument has  been somewhat  modified by Mr. Spencer, and where a  less
 expensive  instrument than either of the  others  is desired, this one will be
 found a good working  instrument,  and  available for all purposes of ana-
tomical  study.  The cost of this  form, with object-glasses as high as  the
|th with the usual accessories, is from $125 to $150.
   Mr. Spencer also makes some simpler forms of instruments, and yet very
efficient working ones, with objectives as  high as ith, the price of which
 does not exceed $75.
   Mr. Spencer has experienced some delay in the completion of his establish-
 ment, owing  to the difficulty of obtaining  efficient workmen, the business 
ACCESSORY  INSTRUMENTS.
33
being in  this country comparatively a new one, and for which it was neces-
sary to educate men and invent tools.   These difficulties are now overcome,
and his establishment is in active operation.
  Mr. J. B. Allen, of Springfield, Mass., has constructed several  microscopes
which are said to have  been very good instruments, both as to model and
object-glasses.   The form is somewhat  after the Pritchard model, in which
the body inclines to any  angle: the object-glasses  yet  made have been
chiefly of low and medium  powers, and have performed very satisfactorily.
   Messrs. Pike and Sons, opticians, of New York, construct a  microscope.
stand of  great steadiness and convenience for use, the supports  and  general
appearance  of which much resemble the large instrument of Mr.  Ross.
The stage is large, being nearly four  inches square, and moveable either by
adjusting-screws, and revolving after the plan described by Mr. Legg, or is
made moveable by  a lever, as sometimes employed  by both  Powell and
Lealand, and Smith and Beck.  This latter stage movement is very exact,
and allows of quick or slow motion in any direction.
   The mirror is large, being about three inches  in diameter, and admirably
arranged for oblique light;  the quick motion is effected by rack-work, and
the slow motion by means of a conical-pointed steel screw, pressing against
the top of a slit in an  inner tube, furnished with a  spring: at the end of
this tube, the object-glasses  are adapted.
   The  instrument is of considerable weight, which  adds to  its steadiness,
being at the same time well proportioned. Its  price, with eye-pieces, all the
accessories, and without object-glasses, is about $100.

                    ACCESSORY INSTRUMENTS.
   There are several instruments accessory to the microscope, and most use-
ful in dissection, in addition to those usually furnished with the instrument.

   1.  Scalpels.—The scalpels of the  dissecting-case of the Medical  Schools
will be necessary  in making the ordinary sections, but for very minute dis-
section, much smaller-sized  instruments will be  found useful.   The blades
of these  may be either straight, curved, lancet-shaped, or probe-pointed.  In
default of any  instruments for  this especial purpose, the  small knives fur-
nished with  the case for operations on the eye, may be employed.

   2. Dissecting Forceps.—Small-sized  forceps, both  straight  and  curved,
are  among  the instruments  most often required  in minute  dissections.
Those with  exceedingly fine points, and at the  same  time made true, are
especially useful.   The more serviceable forms  are here represented:
3 
34
INTRODUCTION.
Fig. 1.
  A very convenient form of forceps, is one known  as the cutting-forceps,
and is represented by figure 2:
                               Fig. 2.
  The sides of this  instrument are riveted at the end, as those of the ordi-
nary  forceps, but the cutting  part  consists  of two  scissor-shaped blades,
which overlap each  other, and are prevented from crossing over too far by
a small steel pin; the blades are bent at an angle with the sides, and by this
means the instrument can  be  very conveniently employed  for dissecting
under a lens of half an inch focus.   An instrument somewhat resembling
this, and called the  microtome,  is represented at figure 3:
Fig. 3.
  "It consists of two sides, like a pair of dissecting-forceps, but each terminated by
a scissor-shaped blade, arranged so that its cutting-edge is perpendicular to the broad
surface of the sides, in order to prevent the blades from opening too wide; a screw 
ACCESSORY  INSTRUMENTS.
35
with a fly-nut is attached to one blade, and the other moves freely upon it; the screw
is also provided with another nut, situated between the blades; the latter may be
adjusted so as to prevent the blades from being closed beyond a certain point, while the
former serves to regulate the space, that the blades may be kept open by the spring." *
  This instrument is a very useful one, on  account of the  great precision
with which any tissue or filament may be cut, independent  of any tremour
of the hand, and without deranging the preparation.

  3.  Dissecting Needles.—These instruments are necessary in carrying on
dissection of delicate tissues under the  microscope.   They may be either
curved or straight, and of  different sizes.  Messrs. Pike and Sons, opticians,
of New York, furnish, at  a very small cost, needle-holders, in which  the
needles may be  changed as often as the points become broken, or otherwise
unfit for use.   Straight needles may be curved by heating them in a spirit-
lamp to a red heat, and then giving them the desired curve :  they should be
then again heated, and dipped  in cold water to harden them.

  4.  Valentin's Knife.—This instrument, used in making thin  sections of
soft  animal tissues—like the  liver, spleen, &c.—is a double-bladed knife,
the  flat parts of  the blades being placed against each other, and adjusted by
a screw, placed  below the cutting portion of the blades.   The form of this
knife is given at figure 4, and  is thus described by Mr. Quekett:
                                    Fig. 4.
  "This consists of two double-edged blades, one of which is prolonged by aflat
piece of steel to form a handle, and has two pieces of wood riveted to it for the pur-
pose of its being held more steadily; to this blade another one is attached by a screw;
this last is also  lengthened by a shorter piece of steel, and both it and the preceding
have slits cut out in them exactly opposite to each other, up and down which a rivet,
a, with two heads, is made to slide, for the purpose either of allowing the blades to
be widely separated or brought so closely together as to touch; one head of this
rivet is smaller than the hole in the end of the slit, and can be drawn through it, so
that the blade seen in the front of the figure may be turned away from the other, in
order to be sharpened or to allow of the section made by it being taken away from
between the blades.  The  blades are constructed after the plan of a double-edged
scalpel,  but their opposed surfaces are  either flat or very slightly concave, so  that
they may fit accurately to each other, which is effected  more completely by a steady
pin seen at  the  base of the front blade.   When this instrument is required to be
used, the thickness of the section about to be made will depend upon the distance
the blades are apart; this is  regulated by sliding up  or down the rivet, a, as the
                 * Quekett's " Treatise on the Microscope." 
36
INTRODUCTION.
blades, by their own elasticity, will always spring open, and keep the rivet in  place;
a cut is then  to be made by it, as with an ordinary knife, and the part cut will  be
found between the blades, from which it may be  separated, either by opening them
as wide as possible by the rivet, or turning  them apart in  the  manner  before
described, and floating the section out in water."
   Mr.  Hernstein, cutler, of New York, has made  a  modification of this
instrument,  by making the handle curved instead of straight: this form has
the advantage of enabling the operator to hold it more firmly  while making
the section; it has the disadvantage of not allowing  him to use the cutting-
edges on the concave side of the  curved handle, without bringing the  tissue
to be cut to  the edge of the table, so that the  handle has room to play below
it.  Those who have not at  hand one of these instruments, and cannot pro-
cure one, may make the thin section with a sharp  scalpel or a thin razor.

   5. Troughs.—Many delicate dissections  are carried on under water; for
this purpose, troughs are necessary on which to place the tissue to  be dis-
sected.   The most convenient are those made of a metal frame, about three
inches long, two wide, and one inch deep, with a glass bottom, so as to  trans-
mit the  light when necessary.  If desired, the under surface of the glass  in
one of the troughs may be blackened with sealing-wax-varnish, or a  piece
of black silk or common court-plaster pasted on.
   In default of this form of trough, any small vessel of glass, porcelain,  or
metal may be employed; a small evaporating-dish answers  extremely well.
If it is  necessary to observe the object by  means of transmitted light,  of
course only  a glass trough will  answer  the  purpose.   One larger trough,
four or  six  inches  square, having a  piece of flat cork half an inch  thick,
(covered with black cloth, if desired,) and secured  to the bottom by means  of
the marine glue, or the compound cement, so that the tissue  under dissec-
tion can be  fastened  with pins to the cork, will be found especially useful.
In this form of trough, dissections of entire insects, such as beetles, common
cockroaches, &c, can be carried on.

   6. The Compressor.—This is an instrument by  means of which pressure
may be applied at will to an object under examination with the microscope;
various forms are in use, but the simplest and most effectual is the one repre-
sented in figure  5:
Fig. 5. 
PREPARATION  OF  OBJECTS.
37
  " This instrument consists of a plate of brass, three or more inches long and one
and a half broad, having in its middle a circular piece of plate-glass for an object-
holder; this is  slightly raised above the metal plate; at one end of the latter is a
circular piece of brass, having attached to it another piece of brass, carrying an arm
capable of being moved up and down, by means of a screw at one end,  while at the
other is a semi-circle, supporting by screws a ring of metal, to the under side of
which, a piece of thin glass is cemented." *

   The  use  of the instrument is to produce  a pressure  upon the object
between the plates of glass while  being examined with the microscope; the
compressor being placed upon the stage  of the instrument.   The object is
placed upon the  under plate of glass, the arm being made to turn away for
that purpose.

   7. Pipettes.—These are fine glass tubes, about  eight or nine inches  in
length,  either  straight, and  of the  same calibre throughout, or curved  or
drawn to a fine point by means of heat from a spirit-lamp.   They are useful
in applying the different reagents to the objects under examination, and also
for collecting any required portion of fluid—as urine, pus, &c.—and placing
it in the desired  position for examination.  They are among the most useful
of the minor accessory instruments, and can be fashioned  in  any shape  by
the student himself.
   A few only of  the  accessory  instruments  that  may be  used in minute
anatomy have been here described.  There is much truth in the observation
of Rudolph Wagner, that the  more  one observes with the microscope, the
more he  learns  to  rely on the simplest instruments; the complicated ones
giving usually more trouble than  assistance.   Still, there are  circumstances
in which a timely  use  of the  instruments just described will be found  of
great assistance.

                 II.—PREPARATION  OF   OBJECTS.

   It is designed  to give but  few directions for the preparation of objects for
the microscope in this place:  particular  directions in manipulation, for those
objects  requiring an especial  method  of treatment, will follow the  articles
in the text.
   1. Fluids.—Fluids, such as blood, urine, &c, require but  little prepara-
tion : a small  portion of the fluid to be examined is placed on a plain glass
slide by means of a pipette, and is then covered with a small  piece of thin
glass.   This latter direction should be  always followed, otherwise there will
be the two-fold danger of  soiling the object-glass, if a high  one be used, by
inadvertantly touching the fluid under examination, and also of allowing the
* Quekett's "Practical Treatise." 
38
INTRODUCTION.
 vapour of the fluid to condense on the object-glass, and thereby occasion an
 indistinctness of vision and want of definition.   Care must  be taken not to
 place too great a quantity of the fluid on the slide at first;  one small drop is
 usually  sufficient.   When dilution  is necessary—and  most of the fluids,
 blood, lymph, &c, are better examined when diluted—the serum of the blood
 or albumen,  may be employed; in most  cases, water cannot be employed
 on account of its reacting properties.
  Fluids generally require higher powers for examination than solid  prep-
 arations.  They may be first  viewed with a J-th-inch object-glass and  then
 with a ±th.   Any of the reagents may be introduced, without removing the
 thin  glass, by means of a pipette containing the reagent placed at one edge,
 and  a little of the fluid allowed to escape.  This will be found to insinuate
 itself under the glass by means of capillary attraction, and  the effects should
 be observed with the microscope.

  2. Solids.—These usually require more care in their preparation for
 examination than fluids.   The hard solids, as bone, require to be cut in thin
 sections, and sometimes  polished before  their  structure can be discovered.
 Particular directions for each preparation will be given  at the  close of the
chapters treating of their anatomy.   The soft solids may be examined either
in their recent condition or be treated by various chemical  agents, or be far-
ther  prepared by injection.   The treatment best calculated  to display the
structure of each particular tissue will hereafter be given.
  For making thin sections of the soft solids, the Valentin's  knife or a sharp
scalpel  may  be  used.  The  compressor, the small scalpels, the dissecting
needles,  and the troughs for dissection will be constantly required.
  Objects examined in this  condition require  for the  most  part very low
powers.   If the compound microscope be used, a  one  or  two-inch object-
glass will be  power high  enough.  In many cases, the  simple microscope
will be most efficient.  In some instances, the same parts of the object require
to be examined with successive powers as high as the ith-inch object-glass.
The  most difficult, as well as the most  beautiful method  of exhibiting the
structure of certain tissues, is by fine injection.

  3.  Injections.—The chief objects of minute injections are to determine the
vascularity of a tissue; the relative order, size, and arrangement of arteries,
veins, and often-times lymphatics, and  to  trace  the final distribution of the
larger blood-vessels in the capillaries.  It will be found that different struct-
ures will present different arrangements of these vessels, always coinciding
with the differences of function.
  To demonstrate these variations of structure, it is necessary that the injec-
tion should be perfect and complete.   The operation is  a delicate one, and 
OF  INJECTIONS.
39
to succeed perfectly, requires some practice;  a few attempts, however, will
convince  any one how much may be attained by perseverance.  Experi-
ments may first be made in comparative anatomy, and the  different organs
of sheep, &c,  may be always easily obtained; and  these not only afford
beautiful  specimens of microscopic anatomy,  but  for the most  part are as
difficult to inject as the  same organs in the  human subject, and  are on
that account very good practice.
   That an injection may  succeed well, it is necessary, that some time should
elapse after death before the operation be attempted.  It is  well known that
immediately after death,  a certain contractility of the vessels takes place,
which would prevent the  perfect penetration  of the material injected: we
must therefore wait for the relaxation of this contraction.   The best time
for injecting is in summer, about twenty-four  to thirty-six hours after death,
and in winter,  about three days.   These are general directions, which may
be changed according to the especial  circumstances of the case,  and the con-
dition of  the organ to be  injected.  It would be a still greater error to wait
too  long  a time; for the softened vessels would certainly be ruptured, and
extravasation of the injected material follow.   This, if extensive, would not
only spoil the beauty of the preparation, but completely defeat the object of
the injection.
   A serious obstacle to perfect injection is the presence of coagulated blood
and other matters in the vessels,  more  especially in the veins.   This point
has not been sufficiently  regarded in  minute anatomy, but it must be evident
that if those obstacles which irregularly contract the calibre  of the vessels
could be  removed, the  chance  of  success  would  be much  greater.  A
necessary step therefore,  preliminary to injection,  is to wash out  the  blood-
vessels ;  this may be done by injecting tepid water or sulphuric ether, when
this latter agent enters into the composition of the injecting material.   It is
also of great advantage to place the body or organ to be injected in  a warm bath
for six or seven hours previous to  the operation.   The temperature should
be about  100° to 106° Fahrenheit.   For small organs, when removed from
the  body, less time will be required.
   As there are several points worthy of  being noted in the  injection of arte-
ries and of veins, the two orders  of vessels will be separately noticed.

   Injection of Arteries.—As a general  rule, the  complete injection of the
capillary vessels, by  means of the arterial trunks, is more  difficult than by
the  veins, for the reason that the  arteries are less  numerous and of less cal-
ibre than the veins.   In the lungs, this disproportion does not exist; but here,
according to the experience of Rossignol, mentioned at the end of the article
on the lungs, the best injections  are  made by the pulmonary veins.   The
arteries have the advantage of requiring less preparation than the veins, and 
40
INTRODUCTION.
of being always ready; they are also more empty of coagulated blood, and
less liable td rupture, owing to the greater thickness of their walls.
  Injections by the arteries  should be  made not  by the  aorta, because too
many vessels  would  be divided in reaching it, but by  the large arteries,
which are accessible ;  as the carotid, brachial, crural, &c.  If the injection
be made by the aorta, the visceral trunks should  be first ligatured.

  Injection by the Veins.—On the other hand, the veins present an obstacle
to perfect injection in their numerous valves; it being almost  impossible to
fill  the  vessels by  one operation, owing to  the  repellant valvular  action.
In this operation,  it is sometimes necessary  to inject a very liquid material
first, and after this has somewhat set, as the term  is, then to inject more of
the same material, but thicker.  The proportions  for these  divisions are
about one-third of the solid material to be injected at first, and the remaining
two-thirds in the second operation.
  Another difficulty in injecting by the veins is their tendency to  rupture;
this can only be prevented by using a moderate  degree of  force.   The
existence of the coagulated blood in the veins has been  already alluded to.
Inferior animals, to be injected  by the  veins, should be  bled  to death, and
the veins by which the injection is to be  made, opened.   The veins of the
extremities are usually injected by the superficial lateral internal and exter-
nal trunks;  when the chylo-poietic viscera are to  be injected in situ, the
vessels are to be filled from the vena portae just before it enters the trans-
verse fissure of the liver.
  In either  order of vessels, the  opening  for  the  canula  of the syringe
should  be a  mere slit corresponding to the long  diameter  of  the vessel, and
not transversely.
  A young  and  lean subject will be found the  best for perfect  injection,
where this can be a matter of choice.

                              SYRINGE.
  The first minute injections were made by Swammerdam, who taught the
art to his friend Ruysch, (born in 1638, died in 1731,)  and who  improved
upon Swammerdam's method.
  These injections led to many discoveries, and  propagated  many errors.
The instrument employed by Swammerdam is still in general use  in the
medical schools, and known  as Swammerdam's  syringe.
  For making extensive injections, this instrument will answer every purpose •
for injecting small organs and parts of the extremities, smaller instruments
must be employed.   Swammerdam's syringe consists  of two main parts__
the syringe  proper  and the canula or pipe.  The canula is fastened in
the nozzle of the  syringe by means of a  bayonet-catch, and  is of course 
SYRINGES.
41
 removeable at will.  A modern improvement is to add a flexible tube to the
 canula, so that, in the operation  of forcing the  injection, no injury will
 happen to the vessel in which the canula is fixed, and no derangement of
 the parts  of the subject on the table.  The canulas are of different sizes,
 to correspond with the calibres of the vessels into which they are to  be
 inserted.
   A syringe invented by Charriere, of Paris, which works with remarkable
 ease and exactness, owing to the arrangement of the discs of leather which
 form the piston, is advantageously used in making injections with  smaller
 quantities; with this syringe also are canulas of different sizes.
   These syringes, with other instruments of Charriere's manufacture, use-
 ful  in  microscopic manipulation,  may be purchased  at Mr.  H. Balliere's
 foreign  book-store, No.  219 Fulton-street, New York.   Many other  forms
 of syringe are in  use, and  all have their advocates;  but  in  general, any
 form in which the working of the  piston is perfectly true, and at the same
 time easy, will, with proper care and attention  to the exclusion of air, &c,
 answer  very well.  The writer  has made some  good injections of small
 organs with the ordinary ear-syringe, which is  also capable of havinor can-
 ulas of different sizes  attached to it.   Some of the many forms of patent
 syringes sold at the druggists for making ordinary enemata, may  be advan-
 tageously  employed, especially when  the  material of the injection is very
 fluid, as in the method by  double-decomposition,  hereafter to be noticed.
 These  instruments would all  require certain adjustments  in the arrange-
 ment of canulas  which the student  could himself make.   One form of
 these enema-syringes, in which the jet is continuous, and not saltatim, as in
 the  forcing-pump, is the best, and the syringe  can be  constantly supplied
 with the injecting material,  if necessary, by an assistant, without suspend-
 ing  the  operation.   One objection to this instrument is, that any accident
 that may happen during the operation, such as rupture of a vessel, cannot
 be appreciated as readily as when the piston is guided by the  hand.  In
 ordinary injections, as already stated, the part to be  injected  should be
 placed some hours in warm water,  before the operation be attempted.  The
 syringe, canula, and injecting  material, should  be  moderately heated.   If
 the injection is to be by the veins, and by these we are usually more suc-
 cessful  than  by  arteries, the canula, with the  flexible  tube,  is  to  be
 secured  in the vessel  previously  incised longitudinally, and the  canula
 secured  by a ligature:  a second  ligature should lie loose upon the canula
to secure the vessel when the operation is finished.   The vein may then be
washed out by an  injection of warm water; at least half an  hour  should
elapse, to allow the vessels to empty themselves, before the injection be pro-
ceeded with.  As it is important to exclude all air in the operation, the tube
and canula should be first filled with the  fluid material, the tube be tightly 
42
INTRODUCTION.
 corked, and the canula  secured in  the  vessel.   The next step is  to fill
 the syringe, and secure the tube by the bayonet-catch.  The injection may
 then  be commenced, with a force, depending  somewhat on the thickness of
 the material employed;  the thinner the fluid, the less force will be neces-
 sary.   When it is recollected how slight  is the muscular force of the heart,
 it will  be easy to conceive how little force will  be necessary to fill the ves-
 sels in  favourable circumstances.
   When a rupture of a large vessel occurs during  the injection, and this
 can be  known by the greater ease with which the material enters, the ope-
 ration must be suspended and the vessel secured.   If the vessel itself cannot
 be isolated, a ligature may be applied, including a portion  of the tissue sur-
 rounding  it.   If rupture  of the capillaries takes  place, the operation need
 not be suspended, but  pressure in the neighbourhood of the  suspected rup-
 ture may be applied, and  the injection must be continued rather longer than
 when no such accident has occurred.
   The  injection being finished, time must be allowed for it to set, when the
 dissection may be commenced.   Many patches will be found more perfectly
 injected than others; and the proportionate success can only be known by
 inspection with the microscope.
   When the minutest capillaries are not injected,  the preparation may still
 be useful in displaying the second order of vessels.
   Mucous membranes require to  be soaked in  water or washed with a
 syringe, to free them from epithelium and mucus.
   The  minute dissection  of injected  tissues is best conducted in water, by
 means of the trough and dissecting needles.
   In conclusion, it may be observed that the operation of minute  injection,
 when properly performed, occupies from one to  five hours, according to the
 size of  the specimen and  the quantity of material  required.
  No  haste should be used, for unless the material be properly prepared, and
 the vessels carefully filled, one may be certain of partial or complete failure.

                            MATERIALS.
   Many substances have been employed as the bases of fine injections but
 as the result depends more on the medium by which the  solid  part of the
 injection is  conveyed  into the vessels, the most useful forms will be here
noticed  in turn.

   1. Injections with  Turpentine.—In  this  method,  materials used  as  paints
of various colours, are first finely ground in linseed oil, then largely diluted
with oil of turpentine.  The paints most used for imparting different colours
are: Vermilion,  Chrome  Yellow, Prussian Blue,  White-lead.   In making
injections with these  paints, too much importance cannot be attached to their 
INJECTING   MATERIALS.
43
 being ground to the utmost possible fineness; otherwise the colouring parti-
 cles of the injection cannot penetrate the capillaries.
   These paints, already finely ground, can be procured at the stores where
 "artist's materials" are sold, or they can be prepared in a "paint-mill" or
 on a house-painter's slab.
   The proportion of the  ground paint to the oil,  varies with the intensity of
 of the colour; but the following scale will usually answer: For Vermilion,
 J„th  part of whole mass by weight;  Prussian  Blue, g^th; Chrome Yel-
 low, Ti-th;  White-lead, Ti„th.
   If it be found that the  proportion of blue makes the injection too thin, the
 blue may be first  well mixed with the white-lead, and then a larger propor-
 tion of the mixed  paint employed.   When too much blue is used, the colour
 produced is nearly black, and therefore too strongly absorbent of light.
   These injections require to be but slightly warmed, and  in  summer this
 process may be entirely  dispensed with.
   When injections by this method  are successful, the colours soon  harden,
 and are well  preserved for a long time.   The plan is the only one recom.
 mended by M. Robin, and is much in vogue in Europe.

   2. Injections with Ether.—To Dr. P. B. Goddard, of Philadelphia, is due
 the  merit of having first employed ether in minute injections;  his method is
 described by him in the Medical Examiner of Philadelphia for December,
 1849, and is  here  quoted:

   "For the purpose of making such an injection, the anatomist must provide himself
 with a small and good syringe; some vermilion, very  finely ground in oil; a glass-
 stoppered bottle, and some sulphuric ether.  The prepared vermilion paint must be
 put into the ground-stoppered bottle, and about twenty or thirty times its bulk of
 sulphuric ether added; the stopper must then be put in its place, and the whole well
 shaken.  This forms the material of the injection.   Let  the anatomist now procure
 the organ to be injected, (say a sheep's  kidney, which is very difficult to inject in any
 other way, and forms an excellent criterion of success,) and fix his pipe in the artery,
 leaving the vein open.  Having given his material a good shake, let him pour it into
 a cup, and fill  the syringe.  Now inject with a slow, gradual and moderate pressure.
 At first, the matter will return by the vein coloured, but in a few moments this will
 cease, and notiiing will appear except the clear ether, which will distil freely from the
 patulous vein.   This must be watched, and when it ceases, the injection is complete.
 The  kidney is now to be placed in warm water of 120° Fahrenheit, for a quarter of
 an hour, to drive off the ether, when it may be sliced and dried, or preserved in alco-
hol, Goadby's  solution, or any  other anti-septic fluid.  For glands,  as the kidney,
liver, &c, it is  better  to  dry and mount the sections in Canada balsam: but for
membranous preparations, stomach, intestine, &c, the plan of mounting in a cell,
filled with an anti-septic solution, is preferable." 
44
INTRODUCTION.
   In this method, as in the preceding one, much depends on the fineness of
 the  colour  used.   The writer has examined many of Dr. Goddard's injec-
 tions with ether,  and can bear witness to their perfect success.
   When the ether  injection  is  employed, the preliminary steps of  heating
 the  body and the injection must of course be  dispensed  with.   If the veins
 are  to be injected, they should be washed out by an injection of pure ether.

   3. Injection  by Double  Decomposition.—This method  consists in  taking
 advantage  of the known  power  of certain  substances to decompose each
 other, and form an insoluble compound.   Upon the original method of using
 these  materials,  Henry  Goadby, Esq. (late dissector of Minute Anatomy to
 the Royal College of Surgeons, London,) has made some  important improve-
 ments, an  account of  which  he first published in the London Lancet, and
 which has been republished in the Philadelphia Examiner for March, 1850.
 Mr. Goadby thus describes the original process and his own  experience:

  " M. Gruby has published an account in the Comptes Rendus of some very successful
 injections which he had made by employing certain fluids, which he used separately,
 and  which, when they met,  mutually decomposed each other, and deposited  the
 colouring matter in the Vessels themselves.
  "He used saturated solutions of the chromate or bi-chromate of potash, and of the
 acetate of lead: he directed that equal quantities  of these fluids should be used, first
 injecting all the chromate of potash, to the extent of one-half the quantity of injec-
 tion  supposed to  be necessary, into the vessels, and  subsequently the  same quantity
 of the acetate of lead.
  "As soon  as these fluids meet, they decompose each other; the acetic acid of the
 acetate of lead combining with the potash to form the acetate of potash, which is set
 free, and the chromic acid of the chromate of potash combining with the lead to form
 the beautiful chromate of lead, which is deposited in the vessels.
  " The reports which had  reached me were highly confirmatory of M. Gruby's suc-
 cess  with these fluids, and  having seen Mr. Bowman's  preparations  of the kidney
 injected on this principle, and with the like materials, I determined to employ them.
 My experiments, however,  were  most unsatisfactory;  for, having injected a terrier
 puppy, a dissection of several hours was required to ascertain whether I had succeeded
in injecting any part or not, and  my best  reward consisted in a patch of capillaries
slightly painted of a pale yellow colour, and entirely wanting that roundness and full-
ness, characteristic of a good injection.
  " I next procured a human foetus, and injected it, with precisely the same results.
  "On making inquiry of  Mr. Bowman, touching the ordinary success which had
attended his experiments, and the experiments of  others, so far  as he  knew,  he told
me that I appeared to have  met with fair average results; for that the labour of dis-
secting, consequent on using these fluids, was always great, and that the operator
must consider himself well rewarded for two or three days' work, by finding a micro-
scopic bit well injected.
  "From this narration of failures, it will be evident that the fluids rarely meet in the 
INJECTING  MATERIALS.                    45
vessels, otherwise the colour would be necessarily precipitated.   With a view to see
exactly what  took place, I determined to inject a piece of intestine, in which the
whole process would be under my inspection.  I placed pipes in the mesenteric veins.
and secured all the cut vessels in the usual manner; I then  proceeded to  throw in
the chromate of potash, and found that the potash would not wait for the  lead, but
came out instantly through the parietes of the vessels  as fast as it went in, and  in
one broad stream covered the table.   I repeated this experiment a number  of times,
but with the same uniform result; on some occasions I threw in the  lead  also, and
as the vessels  were moist with the chromate, the slight painting I  have mentioned
took place; but as only equal quantities of the two fluids produce  the best colour,
the excess of the lead  was useless.
   "Having observed, at this stage of my experiments, that the precipitated chromate
of lead is remarkably fine and soft, I determined to use it, in lieu of vermilion,  with
size;  and although the success was far greater than when I used the  fluids separately,
the results were in no way superior  to the old red injection.
   "The principle involved in M. Gruby's use of these fluids—that, namely, of forming
the colour within the vessels themselves—appeared to be undeniably good, notwith-
standing it had so signally failed  in my hands, and, as far as I could learn, in the
hands of all those persons who had hitherto employed it; and I had no doubt that if
I could succeed in giving some consistence to the fluids, the results might prove more
satisfactory.   For this purpose,  size would not do,  as  it is rarely,  when bought,
much too strong for use, and it would not bear  further dilution.  I  therefore  pro-
cured  the highly concentrated  preparat|on employed by pastry cooks, and sold by
by grocers, under the name of gelatine.  The following is my formula for the double
injection with this material:
   "Sat. solution of bi-chromate of potash, eight  fluid  ounces;  water, eight ounces;
gelatine, two ounces.
   "Sat. solution of acetate of lead, eight fluid ounces;  water, eight ounces;  gelatine,
two ounces.
   " Thus, gelatine, two ounces, are dissolved in sixteen ounces of fluid, and kept and
used separately as before; but the success consequent on the addition  of the gelatine
was quite extraordinary;  the  vessels were all full and  round, and  there was no
extravasation; and  for reasons hereafter  to be explained, the microscope revealed
scenes so rich in depth, colour, and  beauty, as to exceed the best  red injections I
have ever seen.
   "With this form of  injection I have never failed;  I have injected  three fetal  sub-
jects so minutely, that the capillaries of the skin, and of every tissue,  were perfectly
injected.  Among the best specimens I  obtained, I may mention injections of the
papillae of the  lips, gums, and tongue;  of the pulps and capsules of  the teeth; of the
conjunctiva and other tissues of the eye;  of the mucous membrane of the  nose and
cellular tissue; fascia; periosteum, &c;  ceruminous glands, lymphatic glands, and
thyroid glands; pericardium,  auricles of the heart, vasa vasorum, particularly of the
aorta and vena cava, and the vessels of all the nerve  sheaths.    In fine, one foetus
occupied me in dissecting, ten hours a day; for two months, and was scarcely half
finished at the expiration of the time.
   "Having described the success attending the use of  these injecting fluids, I must 
46
INTRODUCTION.
 now say how they are to be mixed and used, as every thing depends on care  in these
 respects.
   "Each parcel of gelatine must be dissolved in the water only, (eight ounces,) and
 in a separate water-bath.  The water-baths I employ consist of two earthern pans,
 such as are applied to a child's chair, and capable of containing about one quart each;
 these are fitted to two tin kettles, the broad flange of the earthern  pan resting on the
 rim of the  kettle, the pan covered with a common saucepan-lid.  The kettles should
 be furnished with a bail of iron wire, like that of a glue-pot, or pitch-kettle.
   "The gelatine is to be slowly dissolved in the eight ounces of water; when this is
 accomplished, the eight  fluid ounces of bi-chromate are to be added  to the  gelatine
 in one pan, and the eight fluid ounces of acetate of lead to the gelatine in the other;
 each should be well mixed by stirring with  a  glass rod, a  separate rod  being  used
 for each solution, lest the chromate of lead should be precipitated.
   "The fluids thus prepared, must then be strained through fine flannel  (using a
 piece for  each fluid) into other vessels, the  earthen  pans cleaned, and the fluids
 returned to them.  The injections are now ready for  use, and must be kept  at a tem-
 perature of about 90° by the warm water contained in the kettles.
   " Directions for using the Injection.—The best subject to inject  is a foetus, as there
 are no  cut vessels  by which  the injection  can escape.  A pipe, with a stop-cock
 attached, should be firmly tied in  the umbilical vein, leaving the arteries open until
 the yellow injection makes its appearance, when they should be secured.  It is most
 essential that, for this injection,  the  subject  be warmed  through by  immersion in
 warm water, the temperature of which must not be higher than 90°, or corrugation
 of the tissues will take place;  it will require from  one hour to two hours to accom-
 plish this,  and the temperature must be maintained until the injection be completed.
 The whole sixteen ounces of the potash preparation  of gelatine must now be used,
 care being taken that its temperature never exceed 90°.  Some manipulators deem
 care of little import in the early stage  of injecting, and throw in the first few syringe-
fulls rapidly, and only exhibit caution when the subject begins to  fill.  In my expe-
rience, this is an error; and he who would succeed, must be equally careful and
 patient throughout.   It is my practice to let the piston descend so slowly, that it can
 scarcely be seen to move.
  " Having used the whole of the first preparation, the acetate of lead must  be used,
when the colour will instantly be formed, and give the  operator  some idea  of his
 progress.
  "The temperature of the subject must be kept up,  and a  fresh batch of injection
made and strained as before.   In about half an hour  the injection  may be resumed,
and the bi-chromate again claims precedence; but only half the quantity need be used
now, followed by an equal quantity of the lead.  At  this point the stop-cock should
be turned, and the subject again allowed  to rest for half an hour; the remainder of the
injections may then be used, and after this, in all probability, the subject will require
 another batch.  The manipulator who employs, for the first time, as much injection
for a foetus as I have already directed to be  used, and who  experiences the  great
resistance opposed to the transmission of the last  several syringes-full, especially as
 the body will by this time  be swollen and tense to an amazing degree, will feel
 somewhat surprised to learn, that if he suspend the operation  for an hour, keeping
up the temperature in the meanwhile, he will be able to throw into the subject twenty 
INJECTING   MATERIALS.
47
or thirty ounces more with comparative ease, and have the pleasure of seeing many
isolated congeries of vessels of the skin gradually approaching each other, and finally
anastomosing most perfectly, while the tension of the body will be so great, that if
the piston be pressed completely down, and the hand withdrawn, it will gradually rise,
and the same may, with care, be repeated several times, without causing extravasation.
  " Towards the conclusion of the process, the injections should be thrown in alter-
nately ; and this should be continued, notwithstanding the prodigious distortion of the
body, as long as the injection is felt to flow in the vessels.  To inject a foetus well,
on  this plan, will occupy from four to five hours.  The operation.finished, the body
should  be thrown into cold water, and should not be dissected until the next day.
  " The Dissection,—Will soon reveal wht.t has become of the injection, and is alto-
gether a disagreeable and difficult task.  It will be found that nearly  all the gelatine
and acetate of potash have transuded and  separated the tissues widely from each
other, and that the blood has been diluted, and intimately mixed with the gelatine,
which is coloured by it.
  "The majority of preparations thus injected, require to be  dried, and  mounted in
Canada balsam.  Each preparation, when  placed on a slip of glass, will necessarily
possess  more or less of the coloured infiltrated  gelatine, which, when dry, forms,
together with the different shades of the chromate of lead, beautiful objects, possessing
depth and richness  of colour.  The gelatine also separates and defines the different
layers of vessels.  By this injection, the arteries are always readily distinguishable, by
the purity and brightness of the chromate of lead within  them, while the veins are
detected by the  altered colour imparted by the blood.
  " Those preparations which require to be kept wet, can  be preserved  perfectly in
my B-fluid, specific gravity 1,100; the A-fluid destroys them.
  "The bi-chromate of potash is greatly superior in colour to the chromate, which
yields too pale a yellow; and subsequent  experience has convinced me that the ace-
tate of potash frequently effects its liberation by destruction of  the  capillaries, and
this, even long after the preparations have  been mounted in Canada balsam; perhaps
this may be owing to some chemical  action of the acetate of potash upon them.
  " Although highly desirable, as the demonstrator of the capillaries of normal tissues,
I do not think this kind of injection fitted  for morbid  preparations, the infiltrated
gelatine  producing  appearances of a puzzling  kind, and calculated to mislead the
pathologist.
  "In  preparing  portions of dried, well-injected skin for examination by the micro-
scope, I have tried the effect of dilute nitric acid, as a corroder, with very good  results.
But probably, liquor potassse would have answered this purpose better."

  The writer has inspected  many beautiful injections  in the  possession of
Dr. Goadby, by his chemico-gelatinous  method, and  can  confirm the fore-
going account of his success and the excellence of his  method.
  Dr. Goadby,  in the article referred to, recommended  that the  nitrate of
lead be substituted for the acetate ; on experiment, however, this change has
not been found  to answer, as the colour  after  mounting has  been observed
to fade.
  Other colours may also be obtained by the method of double  decompo- 
48
INTRODUCTION.
sition; thus, a red precipitate, by the iodide of potassium and the bi-chloride
of mercury; blue,  by the ferro-cyanide of potassium and the peroxide of
iron, &c.
  Most of the preceding remarks apply—1st, to cases in which the whole or
large part of the subject is to be injected; and, 2d, to cases in which both
arteries and veins are to be injected by one material.
  The perfect injection of only one set of vessels or the two sets by differ.
ent materials, so as to fill  the  capillaries, and yet not exceed each one's
proper limits, is  one of the most difficult operations in minute anatomy:  it
is comparatively easy to fill  both orders of  vessels by one injection.
  With regard to the amount of force, and quantity of fluid  necessary for
the injection of only one set of vessels, no  directions can be given that
would not require modification according to each particular case; and suc-
cess must depend more on repeated trials than upon any rules.
  In cases  where two or more materials are to be injected, the arteries, on
account of  their lesser volume, should be first filled.   The colours may be
used in the following order:  Arteries, blue; Veins, yellow.
  When red and yellow are used, the two colours meeting in the capillaries,
form an orange tint, making it difficult to recognise each proper colour.
  When the liver is to be injected, its four orders of vessels  may be thus
filled:  Arteries, blue j Vena Portse,  yellow; Hepatic  vein,  red; Hepatic
duct, white.
  When the uriniferous tubes are to be filled, they may be injected with white.
  A few other materials  for fine injections may be here noticed, although
the  best have been already given:

  Pure  Gelatine.—In using this material, Tulk  and Henfrey direct that
seven parts in winter and twelve parts in summer of  dried  gelatine  be dis-
solved to the consistence of jelly in one hundred parts of water.   The jelly
is then to  be made liquid, as flowing as water,  by  gentle heat, and  the
colouring matter added.   The  colouring  particles must be  suspended  in
water: a red  colour may be produced by vermilion  or carmine; blue, by
indigo or Prussian blue; yellow, by gamboge, &c.
  After  the injection has been  strained through a fine cloth, it is ready for
use, and must  be  thrown in while  warm.    This gelatine is  the same
employed by Dr. Goadby in his method by double decomposition, and may
be procured at the druggist's or grocery stores.
  Fresh  milk, used before the cream has commenced  to form, and coloured
by a watery suspension of the finest particles of indigo, carmine,  &c, may
also be used.  When the  injection is  completed, the preparation must  be
deposited in acetic acid, or  dilute hydro-chloric  acid, for  twelve hours to
coagulate the milk. 
PRESERVATION  OF  OBJECTS.
49
   This form of injection is said to be well adapted for organs that have been
 preserved for any time in weak alcohol.  In this fluid, the vessels become
 so contracted, that any thing like minute injection is very uncertain.
    The  ingredients  employed by  Berres  and Hyrtl, of Vienna, whose
 injections have become so famous, are finely levigated cinnabar, copal var-
 nish, and  gum mastich.  For a full account of Berres' method, see his
 " Microscopic Anatomy," fol., published at Vienna, in Dutch and Latin, 1637.
   In conclusion,  the writer would state that, from  personal experience and
 observation, any of the foregoing methods may  prove perfectly efficient and
 satisfactory, if proper time be allowed to make the injection,  due  attention
 paid to  the preliminaries, and sufficient perseverance  exercised  to obtain
 any useful experience.
   The anatomist  will  therefore find  it to  his interest to persevere in any
 particular form of injection  he may select, rather than  make occasional
 trials with different materials.
   In addition to these  requisites, success, in  any given  case, will  be found
 to  depend much  on the peculiar condition of the vessels, a certain willing-
 ness on their part (if it may be so expressed) to be injected.  This  condition
 will be more generally found in animals that have been bled to death.


                Ill,—PRESERVATION OF  OBJECTS.
   To properly preserve objects that have cost much time and labour to pre-
 pare, will be at once acknowledged a most important part of microscopical
 manipulation.  The  different cements  useful  to the microscopist will be
 first described.   Not  to  embarrass the beginner with  too long a list, the
 mo6t useful only  are given.

                               CEMENTS.
   1.  Japanner's Gold-size. — This mixture may be obtained at  almost all the
 varnish stores, and consists of  boiled  linseed  oil, dry red-lead, litharge, cop-
 peras, gum-animi, and turpentine.   Its cost is trifling, but  it  needs to be
 about three years  old before it will dry rapidly.   It should have the consist-
 ence of thick syrup, so as not  to run too much when applied.   If  the gold-
 size be too thin, it may be thickened by being rubbed up with  a little lamp-
 black or  litharge.  This  cement is the  most useful  of all  for  fastening the
 covers of cells, and  may also be employed  for cementing the cells them-
 selves to the glass slides.

  2.  Asphaltum Cement. — This is made by  dissolving asphaltum in boiling
linseed oil or turpentine, and  is of fine jet-black colour.   It may be  used for
cementing cells to slides,  or cementing down the covers  of the cells.  It  is
                                 4 
50                       INTRODUCTION.
 not acted  on by weak alcoholic solutions, and may therefore be used when
 alcohol is  employed as the mounting fluid :  as  a cement for the covers of
 cells, it is by no means equal to the gold-size.

   3.  Sealing-wax Cement. — This is  prepared by dissolving a quantity of
 any coloured sealing-wax in alcohol, sufficient to  produce a cement of the
 consistence of thick syrup.  Its uses are the same as the two preceding
 cements, but inferior to both.

   4.  Canada Balsam, dissolved in ether or turpentine, and evaporated to a
 consistence sufficient to allow its  being  laid on with a  camel's-hair brush,
 has been recommended as a cement for  fastening cells  to the glass slides.
 It needs, however, the addition of a little heat, to render it sufficiently fluid
 to make the union firm, and  free  from air  bubbles.   This heat  may be
 applied by means of a spirit-lamp to the under side of the glass slide, after
 the balsam has  been  put on, and the cell placed in the desired  position.
 When the balsam becomes  fluid, the cell may be   pressed down, and the air
 bubbles will escape.  This cement is apt to become brittle by age.

   5. Marine Glue. — This substance is in most  use abroad for  cementing
cells to glass slides, and is composed of gum-shellac, caoutchouc, and  naptha.
The kind best adapted for microscopic purposes, is that known in commerce,
as G.  K. 4, and  may be procured  from Messrs.  Pike and  Sons, opticians,
of New York, at a small expense.
   The directions given by  Mr. Quekett, and others, for its use, involve  a
long and tedious process, and are here omitted.   A method equally good,
and consuming  much less  time, has been adopted by the writer, and is in
every way satisfactory:   A small tin cup, with a cover, is used, capable of
holding about six ounces; into this is  poured about two ounces of Canada
balsam, and about the same quantity in bulk of the marine glue, cut in
shavings.   These are placed over a spirit-lamp, or in a sand bath, and stir-
red occasionally, until they  begin to boil, when the cement is ready for use.
It is then applied with a brush to the under side of the cell to be cemented
on, and pressed  on the glass slide,  previously warmed.  By  this  method
twenty-five or thirty cells may be cemented in a very few minutes, and the
cement  may be put aside, and will be again ready for use on being heated
to fluidity.

  6. Compound Cement. — This mixture, which  the  writer has  found the
most useful and least troublesome of all cements, is made—first, of gum-shel-
lac dissolved in naptha, and of the  consistence of syrup; this cement__as
it dries very quickly and  is quite hard and firm—would be very useful by 
PRESERVATION   OF   OBJECTS.
51
itself, were it not for its brittleness; this is obviated by mixing it with equal
parts of thick gold-size.  This cement, which  must be kept in a stoppered
bottle, is always ready for use, and may be applied without heat, by means
of a camel's-hair pencil, to the under side of the glass cell.  This is pressed
firmly on the glass slide, and the superfluous cement may be scraped off,
when hardened.  This  cement dries  rapidly, is not brittle, is not acted on
by any of the fluids commonly used for mounting objects, and has the great
advantage of being always ready.  It may  also be  used for  fastening the
covers of cells where a thick cement is needed.  But for this purpose noth-
ing can be better than the gold-size, three or four years old.

   7.  Gum-Arabic Cement. — A very strong cement maybe made by dis-
solving  three  parts  gum-arabic  and one  part  of  fine sugar in  distilled
vinegar.
   The cement sold in the shops as the diamond cement, which depends for
its adhesiveness on the  isinglass  contained  in it, and also the  liquid glue,
which contains a large portion  of gum-shellac, may  be made  use of as
occasion requires.  The best cements, however, are  the first, fifth, and sixth
of those already mentioned.

   Glass Slides and Cells for presenting Objects. — The glass slide, so usefuj
in microscopic examinations, and so necessary in the preservation of objects,
is a plain slip  of thin plate  or flattened crown-glass, three inches long and
one inch wide.  The size is of course arbitrary, but the one mentioned is
that recommended by the London  Microscopic Society, and is in  general
use by English and American  microscopists : it is therefore desirable that in
exchanges and purchases, a uniformity of size should exist.  The  plate or
crown-glass is purchased in sheets;  the  former  being much  the best, but
most expensive, and  is first cut with a  glazier's diamond in  slips three
inches wide; these are again cut in slips one inch in width, which gives
the necessary size: the rough edges are made smooth by rubbing them on
a  cast-iron plate, with  emery-powder wet with water.   It is much better,
however, to'have this  done at a lapidary's or glass-cutter's;  Mr. Isaac Tay-
lor, glass-cutter, corner of Hester and  Elizabeth streets, New  York,  will
smooth any number of slides at the rate of fifty  cents per one hundred.

   Thin Glass. — The thin glass used for covering certain objects, fluids, &c,
while under examination with  the microscope, and for forming the covers of
cells that are  destined to preserve  objects, is manufactured by  Messrs.
Chance  and Company, of Birmingham, solely for this purpose.  It is of two
varieties of thickness, and known as thick and thin glass: in each case it is
sold by the ounce, the thin glass costing about twice as much as  the other, 
52
INTRODUCTION.
 but of course  containing more in  surface.  Messrs. Chance and Company
 have a branch of their house in New York, at No. 42 Cliff-street, and are so
 obliging as to sell any  quantity, however small, at much more moderate
 rates than were formerly demanded by opticians and  others,  who imported
 it themselves.   The plate and  crown-glass for slides may also be procured
 at the same house.
   For use, the thin glass is cut in  squares, about three-quarters of  an inch
 in size, or in circles, a little less in size than the outer circumference of the
 cell to be  covered.  In either  case, the cutting is performed by a writing
 diamond, the glazier's diamond being too heavy.  To  cut  the thin glass  in
 squares is  very easy, care being taken that the  sheet  of glass to be cut is
 made to  lie flat on a hard smooth table, or, still better, on a  sheet of plate
 glass slightly wet.  To cut  circular covers from thin glass, is rather more
 difficult: it may be done  by taking a thin section of glass tube, or a circular
 piece of stout  gutta-percha, of the size desired  for the covers,  and  laying
 it on the thin glass (this having been previously cut in  strips), and then pass-
 ing  the diamond either inside or outside of the circle, according  to the size
 desired.
  For those who prefer this method of cutting circular covers, a most useful
instrument has been devised  by Mr. Wm. E. Johnson, of  Utica, consisting
qf a stout piece of German  silver or other hard metal, about eight  inches
long, one and a half wide, and one-eighth  of an inch  thick.   In this plate
are drilled  circles of different  sizes, from T9y to  |£ of  an inch in diameter.
The circular covers of thin glass can, by  aid of this instrument, be  cut of
any  required size, and the weight of the  metal  makes the instrument  less
liable to  slip, than when a section  of tube or gutta-percha is used.   The
form of the instrument is represented at Fig. 6 :
                                 Fig. 6.
  To cut glass satisfactorily by this method, it  is necessary to use a dia-
mond having  a  true point,  or one that  will cut in any direction.   Most of
the  writing diamonds sold, will  cut but in one  direction.
  Mr. Quekett has described an instrument devised for the purpose of cut-
ting thin circular covers.  A much simpler instrument, however, is repre-
sented in Fig.  7: 
PRESERVATION   OF   OBJECTS.
53
                                  Fig. 7.
   It usually forms one of the instruments furnished in a mathematical instru-
 ment case, and can be readily procured at any store where such instruments
 are sold : It consists of two arms united by a cradle joint;  one arm pointed,
 like the arm of a pair of ordinary dividers.   The other arm  is about one-
 half the length, having a circular opening, divided perpendicularly in  the
 centre.  The two sides of this circle are made to approach and separate by
 means of a small adjusting-screw.  The original design of the instrument,
 is to draw circles on paper, by means of a  lead pencil fastened in the circu-
 lar opening by the screw.   In  cutting glass, the writing diamond is substi-
 tuted for the lead pencil, and after the cutting-point of the diamond is turned
 in the proper direction, the  diamond-holder is to  be secured at the proper
 distance by means of the screw:  as the steel arm of the instrument usually
 terminates in a sharp point, this must be  removed, and a blunt point made.
 This may rest on  a  small  circle  of flat lead or box-wood, or  gutta-percha.
 If it be found this rest is disposed  to slip,  a piece of chamois  leather  may
 be pasted on the under side of the rest;  if necessary, this may be moist-
ened with a little water or a thin mucilage of gum-arabic.
   The instrument having been  adjusted so as to cut a circle of the required
size, is firmly held upon the thin  glass, this having previously been cut in
slips a little larger than the required  circles, and made to  describe a circle 
54
INTRODUCTION.
 in the same manner as if the lead pencil and paper were used.  Sometimes
 it will be found better to turn the slip of glass round, holding the  diamond
 stationary.   The pressure must be light, but steady, and the edges outside
 the circle are easily removed.

   Glass Cells. — For the  preservation of injected  preparations and  other
 thick animal structures,  some kind of cell is necessary in which to deposit
 the object.   This cell may be made of glass, of gutta-percha, or some  thick
 cement, painted on the  slide in  the  desired shape, and allowed to harden.
 Those of glass are  the best, and are of  different kinds.

   1.  The Thin-glass Cell. — This cell,  useful in mounting thin and delicate
 structures, is made  by taking a square inch of the thicker kind of thin glass,
 and drilling  a hole  in it of about half an inch in diameter.   The  glass so
 drilled is then to be cemented to a plain glass slide, by means of the marine
 glue, or the compound cement, in the manner already described.  When the
 cement becomes dry and hard, the cell,  after being properly cleaned, which
 may be done by scraping off the harder  portions of the cement with a knife,
 and then washing the cell with a solution of borax, or some sulphuric ether, is
 ready for use.

  2. The Drilled Cell, is made in the same way, but in this form, plate-glass
of any desired thickness may be employed, according to the thickness of the
object to be mounted.  Hence,  if this form of cell be used, it will be neces-
sary to have  them of different degrees of thickness, as well as of different
sized calibres.  They are to be cemented to the glass slides in the same
manner as thin glass cells.   When these  cells are well made, they are the
best in use;  but, as will readily be  seen, it  is a difficult matter to drill the
holes without fracturing the  glass.

  3. Tube Cells. — These are sections of stout glass tube, of different  cali-
bres, from J-th to Jths of an inch, cut of any desired thickness, and cemented
to the glass slide in  the same manner.  These  sections are readily made by
means of  a lapidary's wheel, charged with diamond-dust;  afterwards the
cut surfaces  must be ground perfectly flat,  but not  polished.   These  cells
are exceedingly neat in  appearance,  and can be obtained at much less cost
than  the drilled cells.  Mr. Mason,  lapidary, No.  156  Fulton-street,  has
made many of these cells for different microscopists in this city, and at much
less price than it  would cost to  import them.   Where only  one size can be
obtained, a cell of about fths of an inch in calibre, and jth of an inch in thick-
ness  and height when cemented, will be  more generally useful than any 
PRESERVATION   OF   OBJECTS.
55
other one size.   It is  better to have them of different sizes, where this is
possible.

  4. Built-up Cells. — When neither of the preceding forms of cells can be
obtained, the built-up  cells will be found a good substitute, and can be easily
made by the student himself.   These consist of four pieces of glass of proper
thickness and width, cemented to a glass slide, so as to form  an  oblong or
square cell.  Take, for instance, a piece of plate-glass, £th of an inch in thick-
ness, one inch in length, and fths of an inch in breadth; then with a glazier's
diamond and rule, cut off strips from each side, ^th of an inch in width,  and
cement these to the plain glass slide, in  the  precise order in which they
were cut off.  This latter step in  the process may be  insured by marking
the different corners with ink or the point of a diamond.  These cells may
be made of any size  and thickness, and  in these, as well as in  the other
forms of cells, the marine glue or the compound cement may be used.

   5. Gutta-Percha Cells. — Another very serviceable kind of cell, which
may be employed  when the drilled or tube cells cannot be obtained, is made
from gutta-percha. Dr. Goddard. of Philadelphia, was the first to adopt  this
form, which is  readily made in the following manner : Take a flat piece of
gutta-percha of about  |th of an inch in thickness, and with a saddler's-punch,
fths of an inch in  diameter, cut several circles from the gutta-percha: then
with a  punch one size smaller, or about fths of an inch in diameter, cut from
these circles a centre piece.   This is to be thrown aside, and there remains a
cell, resembling a glass tube cell, £th of an inch  in depth, and with the sides
ith of an inch thick : this is then cemented with the marine glue and Canada
balsam  to the plain glass slide, in the same manner as the other forms.
Other cells may be made of white lead, melted marine  glue, or gold-size
thickened with lamp-black.   These substances are all to be traced on the
glass slide  when in a  fluid state, so as to form the necessary sized cells,  and
allowed to harden before fit for use.   The superfluous material may be cut
away before  mounting the object.
  Gutta-percha dissolved  in  chloroform, on account of its  quickly-drying
properties,  has been recommended for this variety of cell.   The writer  has
used it,  but does not find it possesses any advantages over the other substances
already named, and indeed is not equal to the cell made with gold-size  and
lamp-black.
  In constructing cells of either of these materials, it has always been found
difficult to draw the cell so true in form, as to have a neat appearance.   The
writer  has adopted a method by which circular  cells may always be
described exactly true, and made of any  desired depth.  For this purpose, 
 56                      INTRODUCTION.

 the little instrument with the writing diamond used in cutting circles of thin
 glass, is employed.
   In the present operation, a camel's-hair pencil, fine or coarse, according
 to the desired thickness of the cell, is substituted for the writing diamond:
 the pencil, having been dipped either in the asphaltum, gold-size, or any
 other cement, is made to describe a circle in  the same manner as the dia-
 mond in cutting the thin glass.   Smaller cells, constructed  in this way, will
 be found very useful  in mounting  minute portions of muscular fibre and
 other delicate structures that require to be viewed with high powers.

                FLUIDS  FOR MOUNTING  OBJECTS.

   These require to be varied according to the nature of  the structure to  be
 mounted: among many that may be used for this purpose, the following are
 the most useful:
   It may be  here  remarked that all the fluids  that  may  be employed  in
 mounting objects, should be prepared sometime  before  required  for use;
 otherwise many of them will be found to contain an infinite number of air-
 bubbles, which will require the object to be remounted before it can  be
 studied  with  the microscope.

   1. Alcohol and Water. — As  in  the  preservation of large specimens  of
general  anatomy, alcohol and  water is  more generally useful  than any
other fluid,  so by the microscopist, this mixture is more to be relied on than
 any other.  The proportions used in ordinary  preparations (equal parts  of
water and alcohol) will be  found too strong for most of the  cements used  in
 microscopic manipulation;  and it has been ascertained that a weaker solu-
tion than the  above will answer  perfectly  well as  a preservative, and not act
on the cement.  The proportion best adapted for this purpose, is  one  part
 alcohol,  about 60° above proof,  to  five  of distilled water:  with this fluid,
the gold-size, or asphaltum, may be safely used in  cementing down the
 covers of cells.

   2. Goadbfs  Solution. — The following formulas are those in use by Dr.
 Goadby, for the second of which he  was rewarded by the "Society of Arts "
 with a gold medal.
   A-l Solution. — Rock salt, 4  ounces; alum, 2 ounces;  corrosive subli-
 mate, 2  grains; water, 1 quart.   Mix.   Very astringent.
   A-2 Solution. — Rock  salt, 4 ounces;  alum, 2 ounces;  corrosive subli-
 mate, 4 grains; water, 2 quarts.   Mix.  Generally  useful, except where
 the carbonate of lime is present.
   B Solution. — Rock salt, 8 ounces; corrosive sublimate, 2 grains; water 
             FLUIDS  FOR  MOUNTING  OBJECTS.          57

1 quart.   Mix.   Specific gravity, 1.100.—Two ounces  of salt in  addition
to each quart of water will make the specific gravity 1.148.
  This solution preserves the transparency of all tissues, and is  used for
terrestrial and  fresh-water animals.  Marine animals require the specific
gravity to be increased to 1.148 or even higher.

  3. Acetate of Alumina.—The famous Gannal process, formerly so much
in vogue in Europe, consists in using one part of acetate  of alumina, with
four of distilled water, either  as an injection, when it is said it will prevent
decomposition, or as a fluid for mounting objects.  Its destruction of bone is
an objection to  its employment under certain circumstances.

  4. Creosote.—This is  an excellent preservative, but requires some care
in its preparation with water.   One of the best methods  is  to mix it with
water, and then distil the mixture.  The  water will come highly charged
with the creosote.  The only  objection to the employment  of this fluid, is its
tendency to turn the  preparation brown.  An excellent fluid, known as Mr.
Thwaite's  fluid, contains creosote  as an  ingredient, and is thus prepared :
To sixteen parts of distilled water add one part of pure  alcohol and  a few
drops of creosote : stir in a small quantity of prepared chalk, and then filter:
with this fluid mix  an equal quantity of camphor-water, and strain through
a piece of fine  linen.

  5. Glycerine.—This fluid,  now to be obtained at most o the drug-stores,
forms with equal parts of water a valuable preservative for delicate tissues,
in which it is important to preserve the bright colours.   Hence, for the deli-
cate colours of living infusoria, it will answer better than any other fluid.
If the glycerine be  used  pure, its highly refracting properties will sometimes
prevent the object from  being well shown.   To the glycerine, salt, corro-
sive sublimate, spirit of wine,  or creosote, may be added, if desirable.

  6. Canada Balsam.—This very useful material is employed when it  is
desired to increase the transparency of an object, as in sections of teeth, bone,
dec, or in some instances, to mount injectings that  have become dried.   It
may be used with heat or without, and  directions will be  subsequently given
for  its  use in both methods.

  7. Salt and  Water.—A solution, containing five  grains of  common salt
to one ounce of distilled water, will  preserve many animal  and  vegetable
preparations.   Mr.  Quekett mentions that the common objection to all saline
preservatives,  viz:  the growth of conferval in them, may be obviated  by 
58
INTRODUCTION.
the addition of a few drops of creosote or camphor mixture.   This, however,
is inferior to Goadby's B-solution.

  8. Naptha. — In the proportion of one part of naptha to seven or eight of
water, a good preservative is obtained for ordinary objects.   It is stated that
this mixture is now generally used abroad  by Messrs. Hett, Topping, and
others, as the  best  preservative of injected preparations.   If this be true,
it is a strong recommendation in favour of  its employment.
  Dr.  Hannover, in Muller's "Archives,"  1840, recommends the employ.
ment of a .solution  of chromic acid  as a preservative fluid, and also, as  a
fluid in which  soft tissues may be hardened for future dissection.   In a weak
state, as one part to twenty of water, pus, mucus, epithelium, blood corpuscles,
and other delicate structures, are  well  preserved :  when the solution is too
strong, the tissues acquire a yellow or even red colour.
  The writer has not used this solution as  a preservative  sufficiently long
to test its merits, but can speak well of its hardening  properties:  brain, liver,
and other  soft  tissues, after being deposited in this solution a short time,
acquire a degree  of hardness sufficient to allow of very thin  sections.
  The following excellent general directions for mounting objects, are given
by Mr. Quekett, in his work already so often quoted:  "For  all  large speci-
mens, such as  injections, the spirit  and water, or Goadby's first solution, may
be used; and for others, either the creosote  or glycerine solutions, as those
containing saline matter, when placed  either between glasses simply, or in
the thin glass cells, are apt to crystallize slowly, and interfere with the objects
that are mounted in them.  Goadby's  solution, containing both salt,  alum,
and corrosive sublimate, will keep  animal structures that have been injected
with size and vermilion, exceedingly well; but  those in which the vessels
are filled with  flake-white will have that substance destroyed  in a few hours*
in these cases, either the arsenical or the spirit  and water  only should be
employed.   The  glycerine fluid, when kept for some time, is apt to become
mouldy, it should, therefore, be mixed in small quantities, and  then only  a
few hours before it  is required.  When objects are to  be mounted in either
of the above fluids, it must be laid  down as a rule, that  they should have
been  soaking  for some hours in the  same  fluid, or in a fluid of a similar
kind ; this  should be more particularly attended to, when the preparation has
to undergo dissection in water, previous to its being  mounted.   It has often
happened to the author to find a preparation that had been dissected in water
and mounted  in  a  cell in spirit and  water immediately after, completely
covered over with small air-bubbles in a few hours, from the slow admixture
of the two  fluids.   With Goadby's solution,  it does not so  often happen ; but
with this, a white sediment will be sometimes deposited in the bottom of the 
FLUIDS  FOR  MOUNTING   OBJECTS.           59
 cell when  the preparation  has  been  soaking  in spirit  for some time
 previously."
   Objects are usually mounted in one  of four ways.  These are—1, the
 dry way;  2, in Canada balsam with heat;  3, in fluid;  4, as opaque objects.

                          l.-THE  DRY WAY.
   This  method  is  adopted  in  mounting  objects  which  show best their
 peculiar structure without the addition  of  fluid or  Canada balsam.  Such
 objects are some thin sections of  bone and  teeth, some kinds  of hairs,
 some  urinary deposits, die.  It  may be stated here, however, that unless
 a particular method is known,  from repeated trials, to be superior to all
 others, the different  methods should be adopted with a view of trial, where
 the specimens are large enough to divide in this way.  Now, although some
 sections of bone and teeth show better for being mounted in the dry way, yet
 some others show better in Canada balsam;  the  choice depending in some
 degree on the thickness of the section, and the density of the structure.  If
 the specimen to be mounted be a rare one,  and the quantity small, it should
 be examined with the microscope before being permanently mounted.  This
 may be easily done, both in the dry  way and in fluid.   Having determined
 to mount an object  in the dry way, the first  step is, to properly cleanse the
 specimen, as it will  be always found, on examination, that, no matter  how
 clean  an object may appear to  the  eye, or even with a  low  power of the
 microscope, numerous particles of dust will be found on it.
   These, if not removed, may not  only prevent the true structure of the
 object from being determined, but by the beginner may be mistaken for part
 of the structure itself.    Indeed, M. Robin  recommends the microscopic
 study  of dust-particles  as a preliminary to the proper  study of animal
 preparations.
   Ordinary  preparations  may  be cleansed  by  soaking them for a  few
 hours, previous to mounting, in distilled water, or by washing them with a
 small  syringe  and water.  Specimens that contain  grease, as sections of
 bone, die, may be cleansed by soaking them in sulphuric ether or spirits
 of turpentine.   After  being properly cleansed, the  specimen  must  then be
 allowed to dry.  If the object be a thin  one, it is to be placed upon a plain
 glass slide, and covered with a square or circular  piece of thin glass, a little
 larger than the object.   The cover is then pressed firmly down, and fastened
 with thick gold-size, or with the compound cement,  or the diamond  cement,
 always being careful to paint on a thin coat of cement, at first,  and a thicker
one afterwards.
   If the object  be  too thick to allow the cover  to  approach the  slide, the
intervening space may be filled up by small pieces of paper, card-board, or
thin  gutta-percha, having a hole punched  out in the centre, a little larger 
CO
INTRODUCTION.
 than the object.   These are first  to be cemented  to the slide;  the object is
 then deposited in its place, and  the cover cemented down as before.
   If the specimen to be mounted  be a section of lung, gland, intestine, dzc,
 and  some of these show their structure very well when mounted in the dry
 way, one of the different forms of cells before described, may be used.   The
 depth of the cell being always proportioned to the thickness of the object, it
 being desirable to have the surface of the object as near the cover  as possi-
 ble, the  more readily to receive the light.  The cover is then to be applied
 and cemented with the gold-size.

                 2.-CANADA BALSAM WITH HEAT.
   This method is adopted in  mounting thin objects that require  to  be made
 more transparent than they are in the dry state, end at the  same time such
 as will not be injured by heat.  Sections of bone and teeth are often mounted
 in this way.  The Canada  balsam, or, as it is sometimes called, balsam of
 fir, used in this manipulation, should be rather old  and thick, as it then
 requires less heat to  harden it than when new and thin.
   The best way of keeping it for use, is a tall vial with a  narrow mouth.
 From this vial the balsam may be dropped on the  plain slide or object, and
 will be found  a better plan of proceeding than  that usually recommended,
 viz: of keeping the balsam in a wide-mouthed jar, and taking  the desired
 quantity by means of  a glass rod.  In this  latter method,  it will not only
 be found difficult to obtain the sufficiently small quantity required, but the
 portion taken will contain a much greater quantity of air-bubbles than when
 the balsam is dropped  from the vial.   The vial should be only  about half-
 full, and allowed to  stand  uncorked  for a day or so, in order that the air-
 bubbles,  may rise to  the surface, and burst.
  The object having  been properly cleansed  and  dried,  as  directed  in
 mounting objects  in the dry way,  it is to be deposited  in the centre of the
 glass slide, and a sufficient  quantity of balsam to  be dropped on it to com-
 pletely cover it.   For most objects, one small drop will answer.   The slide
 is then to be seized by  means of an ordinary wire forceps with  flat blades
 (covered with leather, if desired), and held over the flame of a spirit-lamp;
 care being taken to approach  the  flame  gradually;  otherwise the slide  if
not broken,  will have  an infinite number of fine  cracks in it,  which will
 effectually spoil its further use.   The slide is to be held over the flame  at
short intervals until all traces of air-bubbles are removed, care at the  same
time being taken to prevent the boiling of the balsam.
  When there is no longer any appearance of air-bubbles, the slide  is to be
removed  from the flame, and a square or circular piece of thin glass, previ-
ously cleansed and ready, is  to be gently warmed, not heated, and  pressed
upon the object.   The  superfluous balsam will escape beyond the thin glass 
CANADA  BALSAM.
61
and when cold may be removed with a knife, and  subsequently perfectly
cleansed by means of a rag  dipped  in ether.   A  modification of this plan
of mounting is, to place the slide containing the balsam upon a piece of tin
kept for the purpose, about four inches square, with the edges  bent up, to
prevent the glass from slipping off (a cover to the ordinary seidlitz-powder
box will answer very well), and to hold this over the flame  of the lamp by
means of the  wire forceps.  In this plan, there is less danger of cracking
the glass, but  no other advantage.
   Still another method is, to have a  small table  made of tin, supported by
wire legs, sufficiently high to admit  the spirit-lamp  under it.   The slide is
then placed on the table,  and heated to the  necessary point as before.  A
little experience will  enable  one to  judge how much  heat  ie necessary to
sufficiently harden the balsam and dispel the  air-bubbles.
   Objects may be mounted in Canada Balsam without heat,  by dropping the
balsam on the preparation, as before, and allowing it to remain uncovered
for a day or two.  In this time, the  air-bubbles will usually burst, or will
rise to the surface, where they may  be  broken by means of a needle-point.
When there  are no longer traces of air in  the balsam, which may at any
time be discovered by placing  the slide under the microscope, and examin-
ing it with a low power, the  thin glass is to  be warmed, and pressed  upon
the object, when the superfluous balsam will escape.  The preparation is to
be set aside, and  allowed  to  harden  by drying  before  the  escaped balsam
can be removed.   This method of   course requires a much longer  time,
before the object  can  be properly finished, than when heat is employed, and
is only adapted to cases where heat would injure the,object.
   When injected specimens are to   be  mounted in  balsam, they should be
placed in cells; one of these of proportionate size and  depth having been
selected, and cleaned by means of ether, or a solution  of borax and water,
the object is to be deposited in the cell, and the unoccupied space filled with
the balsam dropped from the vial.  The balsam should not overrun the cell,
but rise a little above the level of its edge.   The slide is to be set aside for
a  day, where  it will  be free from dust, in order  that the air-bubbles may
rise to the surface, and burst.  When there is no longer any trace of air in
the balsam, a  square or circular cover  of thin glass, properly cleaned, and
a  little  smaller than the outer circumference of  the cell, is to be slightly
warmed in the flame of  a spirit-lamp,  and  placed over the cell.  If the
cover  does  not touch the cell at every  point,  gentle  pressure  is  to  be
employed until the superfluous balsam is pressed out.
   A sharp-pointed knife may then be used to remove the balsam outside the
cell, when a thin coat of the gold-size is to be applied around the edges of
the thin glass, so  as  to cement it to the cell.  In  a  few hours or a day, 
62
INTRODUCTION.
another and thicker coat of the size is to be applied, or a coat of the asphal-
tum or sealing-wax cement.
  Should a bubble of air  enter the cell  during the operation of adjusting
the cover or removing the balsam  around its edges, the cover must be slip-
ped half way off the cell, and another drop of the balsam added.
  When the last coat of cement is quite dry, any trace of  balsam may be
removed from the slide or cover by means of a linen rag or old cambric
handkerchief,  dipped in ether, care being taken not to touch the cement, as
all these are acted on more or less by the ether.

                 3.-OBJECTS  MOUNTED  IN  FLUID.
  Objects mounted  in fluid are usually preserved in some  of the different
forms of cells already described ; but some very delicate structures—such as
muscular fibre, fibres of the crystalline lens, die.—requiring high powers
for examination, should be  mounted  as flat  (as  it is termed) as  possible.
With preparations of this order, the  following method may be adopted: A
clean plain glass  slide  having been selected, the object is to be deposited in
the centre:  if there  are  several  specimens of the same objects, as several
fibres of muscle, they should be  slightly separated by means of a needle-
point.   A drop or two of the mounting-fluid is then  to be added by means
of a  pipette, when the thin glass cover, square  or round, is to be  placed
gently on the fluid.   If the object  has escaped to  the edge of the thin glass,
it will be much easier to remove the cover, and begin again, than attempt to
push back the specimen with a needle.   A very good method to secure the
object in any desired position, is to moisten  it  with a little water, or spirit
and water, and allow this to evaporate, when the object will adhere to the
surface of the glass.  The  fluid  that escapes beyond the edges of the thin
glass may be removed  by means of a camel's-hair pencil, when a very thin
coating of the gold-size  is  to he  applied around the edges of the cover.
When this is dry, another, and sometimes a third  coat, must  be added in the
same way.   When  quite dry and hard, the whole slide may  be  cleaned
with a solution of borax  and water.  This solution is at once cheap, very
cleansing, and should be always at hand.
  The  thin glass cell,  or the cell made with any of the  cements, or the
white-lead, die,  as  previously described, may be also used  for mounting
this  description  of objects.   When the thin glass cell can be obtained, this
will  be found preferable to all others.
  Portions of injected preparations—such as sections of kidneys, liver intes-
tines, die—of different degrees of thickness, require mounting  in cells of
proportionate depth.  The  method is nearly the same as in mounting in
cells with Canada balsam.  The object being placed  in the  cell, the fluid is
to be added either from a vial or  by means of a dropping-tube, so as to fill 
OPAQ.UE  OBJECTS.
63
the cell completely full without overrunning it.   The  cover  is then to be
gently dropped upon the cell, and the escaped fluid must be carefully absorbed
by means of thin bibulous paper, or, still better, by a camel's-hair pencil.
If a bubble of air has entered the cell, the cover is to be half drawn off,
and  more fluid added; a thin coat of cement is then to be applied, and the
object finished, as already directed.

                        4.-OPAQUE OBJECTS.
   It has been found  that some objects, although  sufficiently transparent to
allow the  light to pass through them, yet show their structure better when
viewed  upon a dark  ground, or, as it is termed, viewed as  opaque  objects.
Any transparent  object may be made opaque, by turning away the  mirror
from the stage of the microscope, or by interposing a dark stop between the
object and the mirror.  Both these methods, however, may  be troublesome
at times, and objects that require a permanent dark ground may be mounted
opaque by placing a small  circle of black paper or blackened silk (court
plaster will answer very well)  beneath the object, if it be mounted dry ;  or,
if mounted in balsam or fluid,  either the paper or silk may be  pasted on the
under side of the slide.  The  object should be covered with  thin glass,  as
in other methods of  mounting,  to prevent injury from dust.

   Labelling Slides.—The best method  of labelling slides,  is  to write the
name of the object, and the particular point it is intended to exhibit, on the
right-hand side  of the slide, with a  writing diamond,  such as is used  in
cutting  the thin glass.   On the left-hand side of the object  may be written
the  date  of the mounting, the style of the mounting, whether dry or  in
balsam, or the name of the fluid used.  This will be readily seen to  be
desirable  information, as when several hundred objects are collected together,
it is impossible to remember the peculiarities of  each without some  memo-
randum.  The advantages of each different mounting may  be thus compared
when several specimens of the same object are mounted in  different styles,
and  this experience may be a guide in future preparations.
   Some prefer to cover the slides with paper, either plain  or ornamented,
and  write the contents of the slide with ink.   In pursuing  this method,  a
circle is cut  from the centre of the paper by means of a  saddler's-punch a
little larger than the object; the paper is then  pasted  on by  means of the
gum-arabic cement,  and  the edges turned down over the edge of the slide;
another similar piece of paper is  pasted on the  opposite side of the slide,
and  neatly trimmed off.  In this method, there  is  usually less danger of
breaking  the thin glass cover in subsequent handling, but  it will be found to
consume  considerable time, and, unless very well done, does  not  make  so 
 64                       INTRODUCTION.

 neat an appearance as the first method: farther, it cannot be well employed
 when any form of deep cell is used.

   Cabinets.—For the purpose of preserving microscopical objects free from
 dust and  from danger of breakage, cabinets of different construction  are
 employed.  Where  economy in room  is not  consulted, those  made with
 shallow drawers, having a depth of about half an inch, will be found the
 most convenient.   In these the  slides  all lie on their flat surfaces, where
 any particular  one may be more readily reached than when they are placed
 on their edges.   There is also in the former method less  danger of the cells
 leaking or their covers being broken.
  A favourite method with some, and one occupying much less room, is the
 employment of drawers one inch deep, in which racks are placed at proper
 distances  to  receive  the slides on their edges.   This is  the most  compact
 sort of cabinet, and two  or three thousand slides may be thus preserved in
 a very small space.   The objections to  the plan are, the difficulty of readily
 finding any  desired slide, as you only can see  the edges of the glass, and
 not the object, and also the danger of breakage to the cells containing fluid.
 A method, combining safety and compactness, is the employment of boxes
 fitted with racks, and each  box capable of containing  two  dozen slides
 placed on  their  edges.   The  boxes are then placed on their ends  between
 permanent partitions  in  the cabinet;   and   when arranged  and  labelled
 according to subjects, any particular box or object may be readily reached,
 and all the slides while in the cabinet rest on the flat surfaces.
  Still another method  is, to have boxes made in the shape of books, and
filled with racks, so as to  contain two dozen objects.   The cover of the box
 may be fastened by means of a clasp,  and the boxes, when arranged in a
 book-case  or on the mantel-piece, have a neat  appearance.  The objects are
kept in  the  horizontal position, and being arranged  in subjects, are  very
accessible.

  In the preparation  of the foregoing Introduction, valuable assistance has
been derived from the following  works, to which the student is referred for
more complete  accounts  of some  methods of  Manipulation:  "Quekett's
Practical Treatise on the Microscope," "Anatomical Manipulation, by Tulk
and Henfrey," and "Du Microscope and et des Injections, par Ch. Robin." 
                        THE

       MICROSCOPIC ANATOMY

                         OF

THE    HUMAN    BODY.
              PART   I. —THE  FLUIDS.

  The constituents which enter into the formation  of the body, and
by the combination of which the human frame is built up, naturally
resolve themselves into  two orders, Fluids and Solids, the latter
proceeding from the former.
  In accordance with this natural division of the elements which
enter into the composition of the body, it is intended to divide this
work into two parts: the first of which will treat of those components
of our frame-work which are first  formed—the Fluids ; and the
second will be devoted  to the consideration of those  constituents
which proceed from the fluid  elements, viz:  the Solids.
  Of the fluids themselves, it is difficult to  determine upon any sub-
division which shall  be  altogether without objection;  perhaps the
most practicable and useful division  of them which can be made is,
into organized and unorganized.
  To the above arrangement of the fluids the following exception
might be  taken: all the fluids in the animal  economy, it may be said,
are to be  considered as organized, inasmuch as their elaboration  is
invariably the result of  organization.  But it is intended that the
words organized  and unorganized,  when  applied  to the fluids in
this work, should  have a very different,  as well  as a more precise
signification, and that those  fluids only should be called  organized
which contain in  them,  as  essential, or, at all events,  as constant
constituents, certain solid and organized particles; while those liquids
                            5 
66
THE  FLUIDS.
which are compounded of no such solid matters, as essential portions
of them, should be termed unorganized.
  In  the first category, the  lymph, chyle,  blood,  mucus, as normal,
and pus, as an abnormal fluid, would find their  places together with
the milk and semen.   The fluids of this class, it will be  seen, belong
especially to nutrition and reproduction, and admit also, naturally,
of arrangement into two  series:  in the first, those fluids which are
concerned in the nutrition and growth  of the species itself  would be
comprised—as lymph, chyle, and  blood; and in  the second, those
liquids which appertain to the reproduction, nutrition and growth of
the new species, as the milk and semen, would be admitted.
  In  the second category, viz: that of unorganized fluids, the per-
spirable fluid, the saliva, the bile, and the urine, as well as probably
the fluid of the pancreas, and of certain other  glandular organs,
would be found.
  This  arrangement  of the  fluids of the human body  might  be
represented  tabularly, thus:
	FLUIDS.		
ORGANIZED.			UNORGANIZED.
FIRST SERIES. Normal :			Perspirable fluid. Saliva.
Lymph.			Bile.
Chyle.			Urine.
Blood. Mucus. Abnormal :			Pancreatic fluid (?) &c, &c, &c.
Pus.			
SECOND SERIES.			
Milk.			
Semen.			
  If the terms  organized  and unorganized  be objected to,  the
words compound and simple might take their places, and would well
express  the  distinction which characterizes the two series of fluids •
the former appellation  being applied to those fluids which are com-
pounded of both a solid and a fluid element,  and the latter to those
which do not possess this double constitution. 
ORGANIZED   FLUIDS.
          ART.  I.—THE  LYMPH  AND  THE  CHYLE.

  It will perhaps render the description of the lymph and  the chyle
more intelligible, if the observations which we shall have to make on
these fluids are preceded  by a short sketch of the lymphatic system
itself.  This system  consists of vessels and of glands, which are of
the kind, which has been denominated conglobate.  The vessels have
many of the characters of veins, commencing as mere radicles, which
unite with each other to form larger trunks, and their interior surface
is provided with valves: they arise from all parts of the system, even
the most remote;  those of the lower extremities and abdominal vis-
cera form by their union the thoracic duct,  which, running along the
left side  of the spinal column, unites with  the left sub-clavian vein,
near its junction with the internal  carotid, its  contents  becoming
mingled with  the torrent of blood in that  vein.  The lymphatics of
the left side of the head and neck, as well as those of the arm of the
corresponding side, unite with the same thoracic duct, in  the superior
part of  its course.   On the right side, however, a smaller separate
duct, formed by  the union of the lymphatics of the upper part of that
side of the body, is  frequently met with, and this empties  itself into
the right  sub-clavian vein.  All these  lymphatic vessels, in their
course, pass through the glands above referred to, and in which the
fluid or lymph contained by them doubtless undergoes further elabora-
tion.  The lymphatics  are remarkable for their  equal  and  small
diameter, which allows of the passage of the lymph through them by
mere capillary attraction; they are also to  be regarded as the chief,
though not the exclusive,  agents of absorption in the system, the veins
likewise taking part in this process.
  The lymphatics of the upper and lower portions of the body imbibe
and carry along  with them the various effete matters and particles
which are continually being given off" by the older solid constituents
of our frame, and which  are as  constantly undergoing a process of 
68
organized  fluids.
regeneration;  these they redigest and reassimilate, into a fluid endowed
with  nutritive properties, denominated lymph, and which  is poured
into the thoracic duct.
   Those lymphatics, however, which arise on the surface of the small
intestines, and which, passing through the mesentery, join the thoracic
duct, have received a special appellation, being called  lacteals: this
name has been bestowed upon them on  account of  the milk-like
appearance  of the fluid which they  contain, viz: the  chyle, a fluid
derived from the digestion of the various articles  of food introduced
into the stomach, and which also is emptied into the thoracic duct.
   But the lacteals are not always filled with chyle; they  are  only to
be  found  so when  digestion has  been fully accomplished;  when an
animal is fasting, they,  like  other lymphatics, contain merely lymph.
   The contents of the thoracic duct likewise vary:  it never contains
pure chyle, but during digestion a fluid composed  of both chyle and
lymph, the former predominating, and digestion being completed, it is
filled with lymph only.
  It follows therefore  that, if we are desirous of ascertaining the
proper characters of chyle, our observations should not  be conducted
on the fluid  of the thoracic duct, but on that of the lacteals  themselves.
It is a common error to regard and to  describe the contents of that
duct, at all times and under all circumstances, as chyle, and it is one
which has led  to the formation of some false conclusions.
  We will describe first the  lymph,  next  the chyle, and lastly the
mingled fluid presented to us in the thoracic duct.
  The lymph  is a transparent colourless  liquid, exhibiting a slightly
alkaline reaction, and containing, according to the analysis of Dr. G.
O. Rees, 0 120 of fibrin, with merely a trace of fatty matter.
  When collected in any quantity, and left to  itself, the  lymph, like
the chyle,  separates into a solid and a fluid  portion: the solid  matter
consists of fibrin, and contains mixed up with its substance numerous
granular and spherical corpuscles, identical with the white globules of
the blood; the serum is transparent, and contains but few of the cor-
puscles referred  to.
  The chyle is  a  whitish,  opaque,  oleaginous, and thick fluid, also
manifesting  an alkaline reaction, and containing,  according  to the
analysis of the gentleman above mentioned, 0 • 370 of fibrin, and 3 • 601
of fatty  matter*
  * See article u Lymphatic System," by Mr.  Lane,  in Cyclopedia of  Anatomy and
Physiology, April, 1841, 
THE  LYMPH  AND  THE  CHYLE.
69
   There are present in it solid matters of several kinds.
   1st, Minute particles, described by Mr. Gulliver,* and which con-
stitute the "molecular base" of the chyle, imparting to it  colour  and
opacity: their size is estimated from the jjijj to the jT{R of an inch
in diameter; they are  "remarkable"  not only for their minuteness,
but also for "their equal size, their ready solubility in aether, and their
unchangeableness when subjected to  the action of numerous other
reagents which quickly affect the chyle globules."
   Mr. Gulliver  has  ascertained  the interesting fact, that the  milky
appearance occasionally presented by the blood  is due to the presence
of the molecules of the chyle.   This peculiar appearance of the blood,
which so  many observers have  observed and commented upon, but
of which  none  save Mr.  Gulliver  have  offered  any  satisfactory
explanation, is noticed to  occur especially in young and well-fed  ani-
mals  during digestion; as also in the human subject, in certain path-
ological conditions, and sometimes in connexion with a gouty diathesis.
   2d, Granular Corpuscles, similar to those contained in the lymph,
and identical with the white globules of the  blood, but rather smaller
than  those, and  which will be  fully and minutely described in the
chapter on the Blood.   Mr. Gulliver, in  his excellent article on the
chyle, makes the remark  that the magnitude  of the  globules hardly
differs, from whatever part of the lacteal system they may have been
obtained.
   The granular corpuscles are found  but sparingly in the  chyle of
the inferent lacteals, abundantly in that of the  mesenteric glands
themselves, and  in medium  quantity in the efferent  lacteals, and in
the fluid of the thoracic duct.
   3d, Oil Globules, which vary exceedingly in dimensions.
   4th, Minute Spherules,  probably albuminous, the exact size or form
of which it is difficult to estimate, and which are not soluble in aether,
as are those which constitute the molecular base.
   Chyle, when left to itself, like  the lymph, separates  into a solid  and
fluid portion: the coagulum, however,  is larger and firmer than that
of lymph, in consequence of the greater  quantity of fibrin which it
contains;  it is also more  opaque, from the presence, not merely of
the white  granular corpuscles, but principally of the molecules of the
chyle; the serum is likewise opaque, the opacity arising from  the
same  cause, the peculiar characteristic molecules of the chyle.

      * See Appendix to the translation of Gerber's  General Anatomy, p. 89. 
70
ORGANIZED  FLUIDS.
   The lymph and the chyle may now be contrasted together.   Both
 are nutritive  fluids, the  nutritious  ingredients contained  in  the one
 being derived from the redigestion  of the various matters which are
 constantly thrown off from the older solids, those of the other being
 acquired from the food digested in  the stomach:  the one is a transpa-
 rent fluid, containing but little fibrin, a trace only of oil, and but few
 white corpuscles; the other is an opaque, white, thick, and oily fluid,
 more  rich in fibrin, and laden with molecules,  white  corpuscles, oil
 globules, and minute  spherules; the one, therefore, is less nutritive
 than  the other.
   It has been asserted that chyle, until after its  passage  through the
 mesenteric glands, would not coagulate; the fallacy of this assertion
 has been demonstrated by Mr. Lane*, who collected the chyle pre-
 vious to its entrance into those glands, and found that it did coagulate,
 although with but little firmness, less indeed than it exhibited subse-
 quent to its passage through the glands.
   We now come to consider the nature of the contents of the thoracic
 duct.
   These,  as  already stated, vary according to the  condition  of the
 animal;  thus, if it  be  fasting, the  duct  contains  only lymph; if,
 however, the contents be examined soon after a full meal, they will
be found to present nearly all the characters, physical and vital, of
the chyle, and in addition, especially in the fluid obtained from the
upper part of  the duct, a pink hue, said to be deepened by exposure
to the air.
   This red colour has been noticed by many observers, and it is now
generally agreed  that it arises from the  presence in the fluid of the
thoracic duct of numerous red blood corpuscles.
   The question  is not as to the existence of blood discs in that fluid,
but as to the manner in which their  presence therein should  be
 accounted for, whether it is to be regarded as primary and essential,
or as  secondary  and accidental.
   Most observers agree in considering the presence of  blood discs in
the chyle of the thoracic duct as accidental, although they account for
 their existence in it in different ways.
   The distinguished  Hewsonf  detected  blood corpuscles  in the
 efferent lymphatics of the spleen, which empty their contents into the
  * See Art. "Lymphatic System," loc. cit.
  f Experimental Inquiries, part iii.  Edited by Magnus Falkoner.  London, 1777
 pp. 122. 112. 135. 
THE  LYMPH  AND  THE  CHYLE.
71
thoracic  duct, and in this way he conceived that the fluid of that
vessel acquired its colour.
  The accuracy of Hewson's observation, as to the lymphatics of the
spleen containing blood corpuscles, is  confirmed by Mr. Gulliver, of
the fidelity, originality, and number of whose remarks on the micro-
scopic anatomy of the animal fluids, it is impossible to speak in terms
of too high praise.   Mr. Gulliver detected  blood corpuscles  in  the
efferent lymphatics of the spleen of the ox and of the horse.
  Miiller, and  MM.  Gruby and Delafont, attribute the presence  of
blood discs  in  the chyle to the regurgitation of a small quantity of
blood from  the sub-clavian vein: if they are really foreign to  the
chyle, this is the most probable channel of their  ingress.
  Mr.  Lane  thinks that the division of the capillaries, which necessa-
rily takes place in the opening of the duct, allows of the  admission
into its contents of the blood discs, which are there found.  Such are
the several  ways in which it  has  been suggested that  the blood
corpuscles find entrance into the thoracic duct.
   Mr. Gulliver has noticed that the blood corpuscles contained in the
chyle are usually much smaller than those taken from the heart of the
same animal, and also, that not more than  one-fourth of  the entire
number  present their ordinary disc-like figure,  the  remainder being
irregularly indented  on the edges, or granulated.  The first of these
observations, viz:  that which refers to the  smaller size of the blood
corpuscles found in the chyle, might be  explained by supposing that
those corpuscles were in progress of formation, and that they had not
as yet attained their full development;  the  other remark, as to the
deformed and granulated character of the corpuscles, might be recon-
ciled with the  former explanation, by supposing that some time had
elapsed  between  the death of the animal  and  the examination  of
the fluid  of the thoracic duct.  If this manner of accounting for the
condition presented  by the blood corpuscles of the chyle  should  be
proved to be insufficient, which  I myself scarcely think it will, then
the only other  mode  of explaining their appearances is by supposing
that their presence in the chyle is really foreign, and that, soon after
their entrance  into that fluid, the blood  corpuscles  begin to pass
through  those  changes, indicative of commencing decomposition,
of which they are so readily susceptible.
  Leaving, however, for the present the  question of the origin of the
red corpuscles of the blood, which will  have to be more fully discussed
hereafter, we will in  the next place bestow a few reflections upon the 
72
ORGANIZED  FLUIDS.
origin of the white  corpuscles:  into this subject, however, it is  not
intended to enter at  any length at present, but merely to make such
observations  as seem more appropriately to find their  place in  the
chapter on the  Chyle and  Lymph.
   It has been  noticed that the white corpuscles  occur in very great
numbers in the chyle obtained from the mesenteric and lymphatic
glands; this observation has led to  the  supposition that the white
corpuscles are formed in those glands.
   Upon this question, as upon so many others, Comparative Anatomy
throws much light.  It has been ascertained that the glands referred
to have no existence in the amphibia  and in fishes; in birds, too,
they are only found in the neck.   Thus it is evident, that the lymphatic
glands, however much  they may contribute to  the  formation of  the
white corpuscles, are not essential to their production.
   Corpuscles, very analogous to those  of the chyle and the lymph,
are found in vast quantities in the fluid of the thymus gland in early
life: these  corpuscles Hewson  considered to be identical with  the
globules of those fluids,  and therefore he regarded the thymus gland as
an organ of nutrition, and  as an appendage  to the lymphatic system.
In this opinion he has  been followed by Mr. Gulliver.  That it is an
organ of nutrition, adapted to the special exigencies of early life, there
can be no doubt; but that it is an appendage of the lymphatic system,
and that the globules with  which it so abounds are the same as those
of the lymph and chyle, admits of much diversity of opinion.
   The globules of the  thymus have undoubtedly striking points of
resemblance with the corpuscles so frequently alluded to; they have
the same  granular structure; they are, like them, colourless, and to
some extent they comport  themselves similarly under the influence of
certain reagents.
   There are points, however, of dissimilarity as well as of resemblance;
thus they are usually very much smaller than the lymph corpuscles,
they do not undergo any increase of size when immersed in water, and
acetic acid does not disclose the presence of nuclei.
   But, above all, the corpuscles of the thymus differ from those of the
lymph and chyle in their situation; those of the latter fluids are
always enclosed in vessels in lymphatics, or lacteal lymphatics; while
those of the former fluid, that of the thymus gland, are extravascular
lying loosely in the  meshes of the  cellular  tissue  which forms the
foundation of the substance of the gland itself.
   Now, it is impossible to conceive  that solid organisms of such a size 
THE  LYMPH  AND  THE  CHYLE.
73
as the corpuscles of the thymus can enter the lymphatics bodily;  if
they are received into the circulation at all, they must first undergo
a disintegration and dissolution of their structure.
   Both Mr. Gulliver and Mr. Simon* regard the corpuscles of the
thymus as cytoblasts;  the former, however, believes that before their
development as cytoblasts they enter the circulation, while the latter con-
ceives that they are developed in the gland itself into true nucleated cells.
   It is difficult to suppose, With Mr. Simon, that the small and uniform
granular corpuscles of the thymus are developed into the large, complex
and curiously constituted true secreting cells  of that gland.
   Whether  this be  the case  or not,  however, it would appear  that
Mr. Simon has fallen into a certain amount of error in his account of
the structure of the thymus gland, and  also of other analogous glands, as
well as  in the generalizations deduced by him therefrom.
   Thus, Mr. Simon  states, that in early life there  exists in the thymus
gland  " no trace whatever of complete  cells;" that it is only in later
life that nucleated cells are formed, and that these are developed out
of the granular corpuscles already referred  to, and  which  are alone
present in the gland in the first  years of its existence.  The same
statements are  applied to the thyroid body.
   But Mr. Simon does not rest here : he regards  the long persistence
of the corpuscles, which he states are to be  found in all those  glands
which secrete  into closed cavities, in  the  condition of cytoblasts, as
constituting a remarkable and important distinction between the glands
in question  and the true secreting glands which are  furnished with
excretory ducts.
   These observations are to a considerable extent erroneous, as  is
proved  by the  fact  that  true  nucleated cells are to be  met with
abundantly in  the thymus gland of still-born children, and also in
the thyroid body and supra-renal  capsule ; in the last, indeed, almost
every cell is nucleated.
   On this supposed  essential  structural distinction  between the true
glands which are furnished with excretory ducts, and those anomalous
ones which are destitute  of such ducts, Mr.  Simon founds  some
general deductions.
   It is  known that  the functions performed by  the glands without
ducts are of a periodic and temporary character, while those discharged
by the true glands are  of a permanent and constant nature.

          * Prize Essay on the Thymus Gland.  London, 4to., 1846. 
74
ORGANIZED FLUIDS.
  It is also considered by some physiologists that the nucleus of every
nucleated cell is the only true and necessary secreting structure.
  These views  of the  nature  of the  functions  performed  by the
anomalous glands, and of the importance of the nucleus, being adopted
by Mr.  Simon,  he thence  draws the inference that the cytoblastic
condition of the cells of the  thyroid, thymus,  and other analogous
glands, is precisely that  which is required by organs  which are called
only into action periodically, and in which great activity prevails at
certain periods.
  This  theory is ingenious, but it has been seen that the main fact
upon which it rests is for the most  part  erroneous;  and, the basis of
the theory being removed, the theory itself must fall.
  In  order  that it may be seen  that  the opinions entertained by
Mr. Simon, in his Essay on the Thymus, have not been over-stated, I
will introduce a few passages therefrom:

  "Thus, while the  completion of cells, within the cavities of the
thyroid gland, is assuredly a departure from the habitual  state of that
organ, and probably the  evidence of protracted activity therein; it is
yet just such a direction as may serve even better than uniformity to
illustrate  the  meaning of the  structures  which present it; for it
shows, beyond dispute, that the dotted corpuscles are homologous with
the cytoblasts  of true glands."  (p. 79.)
  "In the thymus one  would at first believe a similar low stage  of
cell  development to  be universal;  for in examining  the contents
of the gland in early life, one finds no trace  whatever of complete cells.
The dotted corpuscles are undoubtedly quite  similar to  those which
we  have recognised as becoming the nuclei  of cells in the thyroid
body, and in other organs;  there is  abundant  room  for  conjecturing
them to be of a correspondent function—to be,  in fact, true cytoblasts;
but the arguments for this point cannot be considered quite conclu-
sive, without some additional evidence."
  " The  completion of a cell,  from the  isolation of so   much of the
secreted product as is collected round each cytoblast, is a very frequent
secondary process.  In  the true glands it  is very frequent, in those
without ducts exceptional." (p. 84.)

  With one other remark on the corpuscles of the thymus, we will
conclude  this short  chapter;  mixed up with those corpuscles are
frequently to be noticed many nucleated  globules, in every way similar 
               THE  LYMPH  AND  THE  CHYLE.            1")

to the white corpuscles of the blood, but  very distinct from the true
cell corpuscles of the gland;  the nucleus of these white globules is of
nearly the  same size as the dotted corpuscles  themselves.  Is there
any relation between this coincidence in size ?
   We now pass to the consideration of the most  important fluid in
the animal economy, viz: the blood. 
76
ORGANIZED   FLUIDS.
   [The lacteals have  their origin  in  the villi of the intestines, while the
 lymphatics originate throughout the body in the  various  tissues and organs
 of which it is composed.
    These  latter  vessels are arranged  in  a superficial  and deep  set;  the
 superficial running  underneath the skin, or under the  membranous coats,
 immediately enveloping the organs in which they are found, while the deep
 lymphatics  usually  accompany  the deep-seated  blood  vessels.    They
 usually exceed  the veins in number, but  are less in size, and  anastomose
 more frequently than the accompanying veins.   The origin of the lymph-
 atics may be either superficial  or deep:  in the  first mode, they usually arise
 in  the form of net-works, or plexuses, out of which single vessels emerge
 at various  points, and  proceed directly to  the  lymphatic  glands, or to join
 larger lymphatic vessels.
   These plexuses consist of several strata, becoming finer as they approach
 the surface, both in the calibre of the vessels and closeness of  reticulation.
 When the lymphatics have a deep origin, their precise mode is  not so easily
 made out:  it is probably the same as when they arise superficially.

                             STRUCTURE.
   The lymphatic vessels, in their structure much  resembling  veins, have
 thinner and more delicate coats; some are  quite transparent.*
   For an account of structure  of lacteals,  see page 492.
   The medium-sized and larger lymphatic vessels, according to Mr. Lane,+
 have three coats; viz: an  internal, a middle  or fibrous, and  an external,
 one, analogous to the external or cellular coat of the blood-vessels.
   The inner tunic is thin, transparent, and elastic, but less elastic than the
 others, being the first to give way when the vessel is unduly distended : like
 the blood-vessels, it is lined with a  layer of  scaly or tesselated  epithelium,
 as in the blood-vessels.   The  middle or fibrous  coat is very  elastic, and
 consists of  longitudinal fibres having the characters of the plain  involuntary
 muscular fibres, fre&ly mixed with fibres of cellular tissue.  Herbst, Henlel
 and others  describe, with these  longitudinal fibres, others  of transverse and
oblique direction:  these are very few in number, the great majority beino-
longitudinal.  The external  or cellular coat is  elastic, and composed  of
 interlaced  fasciculi, of areolar tissue, mixed with some  elastic  fibres.
   The lymphatics receive vasa vasorum, which ramify in their middle and
 outer coats; nerves distributed  to  them  have not yet been discovered  al
though their existence  has been inferred on physiological grounds.   The\
 are also endowed with vital contractility.
           * Quain's "Anatomy," 5th edition, by Sharpey and Quain.
           f "Cyclop, of Anatomy and Physiology," art. "Lym. System."
           I Henle, " Algemeine Anatomie," Leipsic, 1841. 
THE   LYMPH   AND  THE  CHYLE.
   The lymphatics and lacteals are supplied with valves in the same manner
as the veins, and for like purposes.  They usually consist of two semi-lunar
folds, but variations occasionally occur.   They  are  altogether wanting in
the  reticularly arranged  vessels, which compose the  plexuses of origin
before spoken of;  but where they exist, they follow one  another at shorter
intervals than in the  veins.
   Mr. T. Wilkinson King (Guy's Hospital Reports, April, 1840,) has calcu-
lated the entire number of  valves in the lymphatic system at 30,000, while
the veins only contain about 5,000.
   The lymphatics of fish and  amphibia are  usually destitute of valves, and
may be injected from the trunks: in birds,  valves are less numerous than
in the lymphatics of the mammiferous animals.

   "No lymphatics have yet been traced in the substance of the brain or spinal cord,
though they exist in the membranous envelopes  of these parts, nor have they been
detected within  the eye-ball, or in the  placenta  or foetal envelopes.   Although  no
absorbent or open orifices have been discovered  in the lacteals  or lymphatics, yet it
is probable, that both the lymph and chyle corpuscles are developed as cells within
the vessels; according  to one view, these  corpuscles  of lymph, may  be developed
from the liquid  part of the lymph, which serves as a blastema.  In this case, the
nuclei may be formed by aggregation of matter  round nucleoli, which  again may be
derived as germs from other  cells; or, as Henle is  disposed to think, two or more
fat particles  may unite to form a nucleus; upon another view, it may be conceived
that these corpuscles are formed on the inner surface of the walls of their containing
vessels, as epithelium or mucous corpuscles are  produced on their supporting mem-
brane, and that  this process may be connected with  the  absorption  of lymph or
chyle with the vessels, in the  same manner as secretion into a gland-duct, or other
receptacle, is accompanied by the formation and detachment of cells."*

                           MANIPULATION.
   To procure lymph and chyle quite pure,  it is necessary to  take  the  first
from the  lymphatic  glands, and  the second from the lacteals  themselves.
Wagner has found dogs the best subjects for such experiments in compara-
tive anatomy, and on the surface of the liver and spleen, are commonly
found turgid lymphatic vessels, from which pure lymph  may  be obtained.
It may also be obtained quite pure  by opening the thoracic  duct of  an
animal that has fasted for some time before  being killed.
   The chemical analysis  of chyle usually  quoted, is that of the ass, made
by Dr. Rees, and  of  the cat, made by Nasse.
   Dr. Rees has  examined the fluid  contained  in the thoracic duct of a
human subject, a criminal,  an  hour  and a half  after execution.  From  the
small quantity  of food  taken for some hours before death, the fluid must
           * Quain's "Anatomy," by Sharpey and Quain, 5th  edition. 
78
ORGANIZED  FLUIDS.
 have consisted principally of lymph.   It had a milky hue, with a slight tinge
 of buff.   Its analysis, compared with  that of the chyle of the ass, given in
 the text, shows less water, more albumen, and much less fat.
   The chyle-corpuscles are most numerous in  the chyle taken  from  the
 mesenteric glands.
   The lymph corpuscles, though closely resembling the colourless corpuscles
 of the blood, hereafter described, are rather less in size, and not so uniformly
 round.
   The globules of chyle and lymph, also, differ in  structure from the pale
 globules of blood :  in the last, two, three or four nuclei are easily seen when
 the envelope is made more or less transparent, by acetic, sulphureous, citric,
 or tartaric acid.  But globules of lymph and chyle, like the  nuclei  of  red
 corpuscles of blood, are only rendered  more distinct, and slightly smaller by
 any  of these acids;  so that  the central parts  present no regular nuclei, or
 divided nucleus, such as are contained in  pale  globules of blood.   In  the
 larger lymphatics  and  thoracic duct,  are found corpuscles identical in size
 and  structure to the  pale corpuscles of blood.  When fresh, the corpuscles
 of lymph and chyle  swell  on being mingled with pure  water, as  does  the
 nucleus  of blood corpuscle.  Mixed  with a  strong alkali, or neutral salt,
 the globule  becomes partially dissolved, mis-shapen, or fainter, forming a
 ropy and tenacious compound with the fluid.  According to  Gulliver,  the
 average measurements of the corpuscles of lymph  and chyle are the same,
viz: TgVo °f an English inch.  Mr. Gulliver measures the colourless cor-
 puscles of the blood  3 oV o °f an inch, or about 1 larger than the lymph and
 chyle corpuscles.*
  For the purposes of examination and  study of the  corpuscles of lymph
or chyle, it is necessary to place a very small drop obtained from  either of
the sources already mentioned, on a plain glass slide, wiped perfectly clean
 and dry, and cover it immediately with  a piece of thin glass.  It is then
 ready for examination with a jth or ith-inch object  glass.   Sometimes the
corpuscles will be better  observed after the lymph is  diluted with serum.
After examination in this way, the different reagents  may be applied  by
introducing any one of them  by means  of a pipette upon the edge of the thin
covering glass ; by means of capillary  attraction, the reagent will gradually
insinuate itself under the glass,  and  its effects must be  constantly observed
 with the  microscope.

  Plate LXX., fig. 1, exhibits corpuscles of lymph.
              Fig. 2, exhibits corpuscles of chyle.
  Plate LXXIII., fig. 1, exhibits  a lymphatic gland, and lymphatic vessels.]

  * Hewson'a Works, edited by Gulliver, published for Sydenham Society, page 253. 
THEBLOOD.                        79
                   ART.  II.—THE  BLOOD.

  Of all the fluids in the animal economy, the most interesting  and
the most important is the Blood: and it is an appreciation of this  fact
which has led to the concentration upon its study, in times past as
well as present, of the powers of a host of able and gifted observers,
whose labours have not been without their reward.
  The knowledge of this fluid  acquired  by the early physician  was
of a very limited character, it being confined to the observance of a
certain number of external  and obvious appearances, such  as • the
colour, consistence, and form of the effused blood.   Limited  as  this
knowledge was, however, compared with that which, in our favoured
day, we enjoy, it was not without its practical utility.
  More  recently,  the chemist, who is  in these times extending in all
directions so rapidly the boundaries of his domain, has cast upon this
peculiar portion of it a flood of light.   Who, to look upon a dark and
discoloured mass of blood,  could imagine that the magic power of
chemistry could reveal in it the existence of not less than forty distinct
and essential substances ?
  Lastly, the micrographer, with zeal unweariable, has even outstripped
the progress of his rival the chemist, and brought to light results of the
highest importance.  It is  these results  that  in this work we  have
more especially  to consider.
  In  the following pages we  shall have  to  treat of the  blood under
various aspects and  conditions; we shall have to regard it alive and
dead, circulating within its vessels, and motionless without them; as
a fluid and as a solid;  healthy and diseased;  or, in other words, we
shall  have to consider the blood physiologically, pathologically, and
anatomically.
  » Those who wish to learn the comparative size of the blood corpuscles in the
different vertebrate animals, may find a very complete table of their  measurements
in the "Proceedings of the Zoological Society, No. 152," carefully prepared by Mr.
Gulliver; or "Hewson's Works," published for the Sydenham Society, and edited by
Mr. George Gulliver, pp. 237—243:  or "Gerber's  General  Anatomy," edited by
Gulliver—Appendix, pp. 31—84. 
80
ORGANIZED  FLUIDS.
                             DEFINITION.
  The blood  may be defined as an  elaborated  fluid, having usually
a specific  gravity of about  1-055,  that  is,  heavier than water;  in
mammalia and most  vertebrate  animals, being  of a red colour, but
colourless in the invertebrata;* circulating in distinct sets of vessels,
arteries, and veins;  holding in solution, all the elements of the animal
fabric—fibrin,  albumen, and  serum, together with  various  salts and
bases, and  in suspension, myriads of solid particles, termed globules.f
  The  blood  would  thus appear  to be  the grand supporter and
regenerator of the system;  in early life,  supplying the  materials
necessary for the  development of the frame, and, in adult existence,
furnishing  those required for its maintainance:  hence  "the blood"
has been figuratively called " the life."

              COAGULATION OF THE BLOOD, WITHOUT THE BODY.
  The  first  change which  the  blood undergoes  subsequent  to its
removal from the  body consists in its coagulation.   This  phenomenon
has been denominated emphatically, "the death of the blood," because,
when it  has once occurred,  the blood is thereby  rendered unfit  to
maintain the vital functions, and there is  no  known power which can
restore to it that faculty.
  Although the word  coagulation is usually applied generally to the
blood, yet it not to be understood that the whole of the  mass of that
fluid undergoes the change of condition implied by the term coagula-
tion, which affects but a single  element of the blood, viz:  the fibrin.
  The precise circumstances to which the coagulation of the blood is
due, have  never as yet been satisfactorily explained and determined.
Some have conceived that it  resulted from the escape of  a vital  air or
essence.  Much has been said and written upon this "vital principle,"
and, it seems  to me, with  very  little profit.  It would be more  philo-
  * Miiller states that the quantity of blood in the system varies from eight to
thirty pounds, and Valentin found that the mean quantity of blood in the male adult
at the time when the weight of the  body is greatest, viz: at thirty years, is about
thirty-four and a half pounds, and in the adult female,  at fifty years, when the  weight
of the body in that sex is at  its maximum, about twenty-six pounds.   According
also to Miiller, the specific gravity of the blood varies  from 1 • 527 to  1 • 057 ; arterial
blood is lighter than venous.
  f In one vertebrate animal,  a fish, Branchiostoma  lubricum Costa, the blood is
colourless, and in the most of Annelida it is red; the  red colour, however exists in
the liquor sanguinis, and not in the  blood corpuscles. 
THE  BLOOD.
81
 sophical, I think, to regard animal life not as an essence, or eether, but
 as the complex operation of nicely-adjusted scientific adaptations and
 principles.   According to this view, the human frame in health would
 be comparable (and yet, withal, how incomparable is it!) to a finely-
 balanced machine, in  which  action and reaction  are  proportionate,
 and  in  disease disproportionate,  the  injury to the machine  being
 equivalent to the disproportion between  the two forces.*
   The coagulation of the blood, in some degree, doubtless depends
 upon the operation of the following causes, each  contributing in a
 greater  or  lesser  degree to  the  result;  namely, the  cessation  of
 nervous influence, the abstraction of caloric, the exercise of chemical
 affinity  between the particles of fibrin, and, lastly, a state of rest:
 between motion and life a very close connexion appears to exist.f

                       Formation  of the Clot.
   A portion of blood  having been abstracted from the system, and
 allowed to remain for a few minutes in a state of quiesence, in a basin
 or other suitable vessel, soon manifests a change of condition.   This
 consists in the separation of the fibrin and globules of the blood, which
 go to form  the clot, from the serum, which  holds in solution  the
 various salts of the blood.  In this way a rude and natural analysis is
 brought about; the fibrin, being heavier than the  serum, falls to the
 bottom,  and, by  reason  of its coherence  and contractility, forms a
 compact mass or clot, the diameter of which is less than that of the
 vessel in which it is contained; while the lighter serum floats on the
 top and  in the space around the clot.
   Now, the only active  agent in this change in the arrangement of
 the different constituents of the blood, is the fibrin;  and although the
 globules of the blood constitute a portion of the  clot, yet they take no
 direct part in its formation, and their presence in it is thus accounted
 for; the fibrin, in coagulating, assumes a filamentous and reticular
 structure, in the meshes of which the  globules become entangled,
 and thus are made to contribute to the composition of the clot, the bulk
 of which  they  increase, and to which they  impart the red colour.
   It was an ancient  theory that the clot was  formed solely by the

  * It is hoped that the preceding brief remarks will not expose  the writer to the
charge of being a Materialist; between animal life and mind an essential distinction
exists.
  t " Fresh blood, if exposed to a very low temperature, freezes, and may in that
state be preserved, so as to be still susceptible of coagulation when thawed."—Mullek.
                              6 
82
ORGANIZED  FLUIDS.
union of the globules with each other.  The fallacy of this opinion is
easily demonstrated by the two following decisive experiments:
  The first is that of Miiller, on the blood of the frog, who separated,
by means of a filter, the globules from the fibrin, the latter still form-
ing a clot, although deprived of the globules.  This experiment is
not,  however, applicable to the blood of man, or of  mammalia in
general, the globules in these being too small to be retained by the
filter.   The second expedient is, however, perfectly suited to  the
human blood.   It  is well known that if blood, immediately after its
removal from  the body, be stirred with a stick, the fibrin will adhere
to it in the form of shreds; the blood being defibrinated by this means,
the globules fall to the bottom of the basin in which the blood is con-
tained, on account of their gravity; but they  do not cohere so as to
form a clot, remaining disconnected and loose.
  It  is difficult to determine the exact time  which the blood takes to
coagulate, because this coagulation is not the work  of a moment;  but,
from  its commencement to  its  completion,  the  process occupies
usually several  minutes.   The first evidence of the formation of the
clot,  is the appearance of a thin and greenish serum on the surface of
the blood,  in  which  may be seen numerous delicate  fibres,  the
arrangement of which may be compared to  that of the  needle-like
crystals contained in the solution of a salt in which crystallization has
commenced.   Estimating, however, the coagulation neither from its
commencement nor from the  complete formation  and  consolidation
of the clot, but from the  mean time between these two points, it will
generally be found that healthy blood coagulates  in from fifteen to
twenty minutes.
  In diseased states of the system, however,  the time occupied in the
coagulation of the blood,  or, in other words, in the formation of the
crassamentum,  or  clot, varies very considerably; and it is of much
practical importance that the principle which regulates this diversity
should be clearly understood.
  In disorders of an acute, active, or sthenic character, in which the
vital energies  may be regarded  as in  excess—as, for  instance, in
inflammatory affections, in pneumonia,  pleurisy, acute  rheumatism,
and  sanguineous  apoplexy: in febrile  states of the system, as in the
commencement of some fevers, as in ague, plethora, and as in utero-
gestation—the blood takes a much longer time  than  ordinary to
coagulate, no traces of this change in the passage of the blood from a
fluid to a solid state being  apparent until  from sixteen  to twenty 
THE  BLOOD.
83
 minutes have  elapsed.  This  length of time may be accounted for,
 by supposing that, in the affections named, the blood is endowed with
 a higher degree of vitality,  and that  therefore a  longer period is
 required  for its death to ensue; or, in other words, if the expression
 may be allowed, that the blood in such cases dies hard.   On the con-
 trary,  in disorders of a  chronic, passive, or asthenic character, in all
 of which there is deficiency of the vital powers—as in typhus, anemia,
 chlorosis—the blood passes to  a solid state in a much shorter  period
 than ordinary, even in from five to ten minutes.   In these cases the
 vitality of the blood is very feeble, and  it may be  said to die  easily.
 A remarkable difference is likewise observable in the characters of the
 clot formed in the two classes  of  disorders named; in the first it is
 firm, and well defined;  in  the second, soft, and  diffluent.*  To  this
 subject we shall have occasion again to refer, more at length.
   Fibrin, if left at rest for a time, undergoes a softening process, and
 breaks up  into an extremely minute granular  substance.    This
 softening of the fibrin has  been improperly confounded with suppura-
 tion;  the softened,  mass,  however, may be distinguished from true
 pus by the almost complete absence of  pus  globules.  This peculiar
 change in the condition  of the fibrin has been  noticed to occur both
 in  blood  contained  within and without the body, and large softened
 clots of it are not unfrequently encountered in the heart  after death.
 The process always commences in the centre of these clots.

             Formation  of the Buffy Coat of the Blood.
   Surmounting the  coloured portion of  the clot is observed, in blood
 taken  from  the system in inflammatory states, a yellowish-green
 stratum; this constitutes the buffy or inflammatory crust, the presence
 of which was deemed of  so much importance by the ancient physician,
 and which is indeed not without  its pathological  value.   This crust
 consists of fibrin deprived of the  red globules of the blood; and its
 mode of formation is thus easily and satisfactorily explained.   Of the
 constituents  of the  blood,  the red  globules  are the heaviest; now,
 supposing that no solidification  of any one element were to take place,
 these, of course, would always be found occupying the lowest position
 in the containing vessel;  the fibrin  would take the second rank, and the
 serum  the third: but such, under  ordinary circumstances, not being
  * It is to be remarked, that  the clot is not of  equal density throughout, but that
its lower portion is invariably  softer than the upper, and this is accounted for by the
fact of its containing less fibrin. 
84
ORGANIZED  FLUIDS.
 the case, and the fibrin coagulating so speedily, the globules become
 entangled in its meshes  before they have  had sufficient  time  given
 them  to  enable them to ottey fully  the  impulse  derived from their
 greater specific gravity; and thus no crust is formed.   In blood drawn
 in inflammations, however, this coagulation, as already  stated, pro-
 ceeds  much more slowly;  and thus time  is  allowed to the globules to
 follow this impulse of the  law of gravity to such an extent, as that
 they fall  a certain distance, about the sixteenth of an inch, usually,
 below the surface of the fibrin, before its complete  coagulation averts
 their further progress; and a portion of which is thus left colourless,
 which constitutes the buffy and so-called inflammatory crust of  the
 blood.  But there  are  other  considerations to which it is necessary
 to attend, and which contribute to the formation of the buffy coat.
   One of  these is  the  greater  relative  amount of fibrin  which
 inflammatory blood contains.
   A second is the  increased disposition, first  pointed  out  by Pro-
 fessor  Nasse, which the red corpuscles have in inflammatory blood to
 adhere together and to form rolls, and  the  consequence of which is
 that they occupy less space in the clot.
   A third additional consideration, to which it  is necessary to attend,
 in reference to the formation of the inflammatory crust, is the density
 of the blood, which bears no exact  relation to the amount of fibrin,
 but depends rather upon the quantity of albumen which  it contains.*
 The greater the density of the blood, the  longer would  the  globules
 take to subside in that fluid; and the less its density, the shorter would
 that period be.  Now, inflammatory blood is usually of high density,
 while with that of feeble vitality, the reverse obtains.   Thus, were it
 not for the fact, that in blood in the first state, coagulation is slow, and
 in the  second quick, the blood of weak vital power would be that in
 which, a priori, we should expect to see the buffy coat most frequently
 formed; but the much greater rapidity in the coagulation of the blood
 more than counterbalances the effect of density.
   The blood, then,  may be so dense, that  although at the same time
it  coagulates very slowly, yet no inflammatory crust  be formed the
patient from whom the  blood is  extracted labouring all the while
under severe inflammation.  An ignorance  of  this fact has been the
source of  many great and  perhaps fatal errors, on  the part of those
  * It has been remarked, that in albuminuria, in which a considerable portion of
the albumen of the system passes off with the urine, the blood possesses a very
feeble density. 
THE  BLOOD.
85
physicians who have been used to regard the presence of the  buffy
coat as an undoubted evidence of the existence of inflammation, and
its absence as indicating immunity therefrom.   It has been remarked
that, in the first bleedings of pnemonic patients, the blood often wants
the buffy coat; this is attributed to its  greater  density, and which is
found  to  diminish with each succeeding  abstraction of blood;  so
that if inflammation be present, the characteristic  coat  is usually
apparent also after the second bleeding.
   The conditions, then, favourable to the formation of the buffy coat,
are a mean density of the blood, slow coagulation,  excess of fibrin,
and increased disposition to adherence on the part of the red corpuscles.
   Other circumstances  doubtless exist, which in a minor degree affect
the formation of the crust: such as  the density of the globules, and
the qualities of the fibrin itself.   Into these it is unnecessary to  enter,
as they do not vitiate the accuracy of the  general statements.

                     The Cupping of the Clot.
   At the same time that the crassamentum exhibits the buffy coat, the
upper surface of the clot is very generally also cupped.   This cupping
of the clot arises from the contraction of that portion of the  fibrin
which constitutes the buffy stratum, and which contraction operates
with greater force on account of the absence in it of the red corpuscles
of the blood.   The  degree to  which  the clot  is cupped, therefore,
probably is  in direct relation with  the thickness  of the  crust.   Its
presence was  also  regarded  as an  indication of  the  existence  of
inflammation,  the amount of cupping denoting the extent  of inflam-
mation.   This sign is not, however, any more  than that  afforded  by
the  buffy  coat,  to be   considered as an  invariable criterion of  the
existence of inflammation.*
  * Professor  Nasse  has pointed out a mottled appearance which  is frequently
observed to precede the formation of the buffy coat, and the existence of which he
states to be quite characteristic of inflammatory blood.  This appearance is produced
in the following manner: after the lapse of a minute  or two, a  peculiar heaving
motion of the threads or rolls formed by the union of the red corpuscles with each
other is observed to take place; this results in the  breaking up of  the rolls, the
corpuscles of which  now collect into  masses, leaving, however, intervals between
them, and which become filled with fibrin; now, it is the contrast in colour between
this fibrin and the masses of  red corpuscles which occasions the blood in coagulating
to assume the mottled aspect referred to. 
86
ORGANIZED  FLUIDS.
         COAGULATION OF THE BLOOD, IN THE VESSELS AFTER  DEATH.
   The coagulation, or death, which we have described  as  occurring
in blood abstracted from the system by venesection, takes place like-
wise—the  vital influence which  maintains  the circulation  being
removed—in that which is still contained within the vessels of the
body, although in a manner less marked and appreciable.
   As also in the case of the  blood withdrawn from the system, the
time occupied in the coagulation of that which is still enclosed in  its
own  proper  vessels,  varies  very considerably.  This   difference
depends partly upon the circumstances under which the patient has
died, whether he has been exhausted or not by a previous long and
wasting illness, and partly upon  temperature  and, perhaps, certain
electric  states of the atmosphere.   In  all instances, however,  a  much
longer period is required for the production of coagulation in blood
not removed from  the body, than in that which has been withdrawn
by bleeding; this change in its condition being seldom effected, in the
former instance, in a shorter period than from twelve  to twenty-four
hours subsequent to decease; although occasionally, but  rarely, it may
occur at periods either earlier or later than those  named.
  Signs of Death.—It has already been stated, that blood once coag-
ulated is rendered  unfit for the purposes of  life, and that  no known
means exist capable of restoring to coagulated blood its  fluid state, so
as to render it once again suited to play its part in  the  maintenance
of the vital functions.   The accuracy of these statements  is  attested
by  physiology, which  demonstrates  to us  that a fluid condition is
necessary to the blood, for the  correct performance of its  allotted
functions.  It follows,  then, from  the foregoing, that  a  coagulated
state of the blood,  not in a single vessel indeed, but in the vessels  of
the system  generally,  affords a  certain indication that  death has
occurred, and that therefore a return to life has become impossible.
   It has ever been an object of the highest importance to  distinguish
real from apparent death; and anxious searches have  been instituted
in the hope of discovering some certain sign whereby the occurrence
of death is at once signalized.  Hitherto this inquiry has been unsuc-
cessful; and it could hardly  have been otherwise;  for  before the
physiologist will be able to determine  the  precise moment when life
ceases, and death begins, he must know in what the life consists for
death is but the negation of life.   It is probable that  the mystery of
life will never be revealed to  man; if, indeed,  it  be any thing more 
THE  BLOOD.
87
than, as already hinted, the result of the combined operation of vari-
ous chemical and physical laws appertaining to matter.
   Although no one single sign has hitherto been discovered indicative
of death at the moment of its  occurrence, yet several appearances
have been remarked some time  after death, all of which are of more
or less value in determining so  important a point.  Independently of
the cessation of respiration and circulation, the presence of muscular
rigidity, some other changes have been noticed to occur in  different
parts of the human body soon after  the  extinction of life; as, for
instance, in  the eye,  and in the skin:  these are mostly,  however,
symptomatic of incipient decomposition, and the time of their  acces-
sion  is very uncertain: they likewise affect parts, the integrity of
which is not essential to life.  A fluid  state of the blood, on the con-
trary, has been shown to be indispensable to  life; so that the change
which it undergoes in the  vessels of the body so quickly after death,
may be employed with much advantage and  certainty in determining,
in doubtful cases, whether life has become extinct or not.
   It is by no means difficult to  establish the  fact of the coagulation
of the blood in the vessels after death.   If a  vein be opened, as in the
ordinary operation of bleeding, in a  person who  has  just died, the
blood will issue in a fluid state,  as in life; but it will not leap forth in
a stream.  If a little of  the blood, thus  procured, be preserved in a
small glass, we shall soon remark the occurrence of coagulation in it,
from which we shall know that  the fibrin within the vessels has not
as yet assumed a solid form.  If we repeat this operation at the end
of about eighteen hours,  we shall obtain only a small quantity of red-
dish serum, in which, on being set aside for a time, no  crassamentum
will be found, the only change occurring in this serum  consisting in
the subsidence of the few red  globules which were previously sus-
pended in it, and which now form, at the bottom of the glass, a loose
and powdery mass.  By this experiment, which may be repeated  on
several  veins, and even on an artery, we have clearly established the
fact of the coagulation of the blood within the vessels of the body,
and  therefore  have ascertained, in a manner  the most satisfactory,
that life is extinct.
  In some instances, the blood  is said to  remain fluid after death:
this statement is not strictly correct, as a careful examination of such
blood will always lead to the detection of some traces of coagulation.
To the subject of the fluid  condition of the blood after death, we shall
have hereafter to return, in treating of the  pathology of the blood. 
88
ORGANIZED  FLUIDS.
  When it is recollected that the heat of some climates, and the laws
and usages  of other countries, compel the interment of the  dead  a
very  few hours  after decease,  the importance of this inquiry will
become apparent; and the value of any  sign which more certainly
indicates  death than  those usually relied upon in determining this
question, will be more fully appreciated.
  It cannot be doubted but that, from the insufficient  nature of the
signs of death usually regarded as decisive, premature interment does
occasionally take place; and it is probable that this occurrence is far
less unfrequent than is generally supposed, and that for each  discov-
ered case, a hundred occur in which the fatal mistake is never brought
to light, it being buried with the victim of either ignorance or care-
lessness.*
  We have now to proceed to the anatomical consideration of the
blood; we have to pass to the description  of the solid constituents of
that fluid, the globules;  to describe their  different kinds, their form,
their dimensions and their structure;  their origin,  their development,
and their destination, their properties, and their uses.

                      THE GLOBULES OF THE BLOOD.
  The blood is not an  homogeneous fluid, but holds  in suspension
throughout its substance a number of solid particles, termed globules.
These serve  to indicate to the eye the motion  of the blood; and were
it not for their presence,  we should be unable to establish,  micro-
scopically, the fact of the existence of a circulation, to  mark its course,
and to estimate the relative speed of the current in arteries and veins
under different circumstances.
  These globules  are  so abundant in the blood, that  a  single drop
contains very many thousands of them, and yet they are not so minute
but that their form, size, and structure, with good microscopes, can
be clearly ascertained  and defined.  They are not all of one kind, but
three different descriptions have been detected—the red globules, the
white, and certain smaller particles, termed  molecules.  We shall
take each of them in order; and notice, in the first place, the red
globules, f

  *  The coagulation of the blood may be retarded or  altogether prevented by its
admixture with various saline  matters: to this point we shall have occasion to refer
more fully hereafter.
  f  Malpighi first signalized the existence of the  red globules in the blood, so far
back as 1665:  he regarded them as of an oily nature.  The words in which this dis- 
THE  BLOOD.
89
                          THE RED GLOBULES.
  The number of red globules existing in the blood surpasses by many
times that of the white.   To the sight, when seen circulating in this
fluid, they appear  to  constitute  almost the entire of its bulk.   We
shall now have to consider their  form, the size, the structure, and the
properties by which they are characterized.
  Form.—In man, and in most mammalia,  the  red  blood corpuscles
are of a circular, but flattened, form, with rounded edges, and a central
depression on  each surface, the  depth of which varies  according to
the amount of the contents of each globule.*   Such is the normal form
of the blood discs, or  the shape proper to them while circulating in
the blood of an adult.   (See Plate I. fig.  1.)  In that of the embryo,
the depression is wanting, and the globules are simply lenticular.f
   The  blood globules, however, like all  minute vesicles, possess the
properties of endosmosis and exosmosis.   These principles depend for
their operation upon the different relative  density of two  fluids, the
one external to the vesicle, the other internal.  When these two fluids
are of equal density, then no change  in the normal form of the vesicles
occurs: when,  however, the internal fluid is  of greater density than
the external, then  an  alteration of shape does take place; endosmosis
ensues, in  which  phenomenon a portion of the liquid without the
vesicle  passes through its investing membrane, and thus distends and
modifies its form.  Lastly, when a  reverse disposition of the fluids
exists, a contrary effect becomes manifested;  exosmosis is the result;
this implies the escape of a portion of the contents of the vesicle into
the  medium which surrounds and envelopes it.  The  operation of

covery was recorded were as follow: "Sanguineum nempe vas in omento hystricis...
in quo globuli pinguedinis propria figura terminati rubescentes et corallorum rubrorum
vulgo coronam aemulantes..."—De Omento et adiposis  Ductibus.  Opera omnia.
Lond. 1686.
  Leeuwenhoek was, however, the first observer who distinctly described the blood
globules in  the different classes of animals: this he did in 1673.  These historical
reminiscences are not without their interest, and further references of this kind will be
introduced in the course of the work.
  * The central depression was first noticed by Dr. Young.  The flattened form with
the central depression  on each surface, and of which a bi-concave lens would form an
apt  illustration, is that which any vesicle partially emptied of its  contents would
assume.
  t Hewson figured the difference in the form of the blood globule in the embryo,
and in the adult, in the common domestic fowl, and in the viper. 
90
ORGANIZED  FLUIDS.
these principles is  beautifully seen, not merely in the blood  globules,
but more especially in those exquisitely delicate formations, the pollen
granules.
  Between the density of the liquid contained within the red globules,
and that of the liquor sanguinis, in states of health, a nice adaptation
or harmony exists,  whereby these globules are enabled to retain their
peculiar form.  There is, however, scarcely any  other  fluid which
can be applied to the globules which does not, more or less, affect their
shape, most of the  reagents employed in their examination rendering
them spherical.   (See plate I. fig. 3.)
  From the preceding observations, therefore, it follows that the red
globules, to be seen  in their normal condition, should be examined
while still floating  in the serum: they are best obtained by pricking
the finger with a needle or lancet.
  Usually, when the  microscope is brought to bear upon  the object-
glass, the globules are seen to be scattered irregularly over its surface,
the majority of them  presenting their entire disc to view, others lying
obliquely, so as to render apparent  the  central depression, and others
again exhibiting  their thin edges,   (See Plate I. fig.  1.)   Not unfre-
quently, however, a number of corpuscles unite together by their flat
surfaces, so as to form little  threads, comparable  to strings of beads,
or of coins, which  are more or less curved, and in whichthe lines of
junction between  the corpulscles are  plainly visible.   These strings
of compressed globules bear also a close resemblance to an Oscillatoria,
and a still closer likeness  to the plant described in the  history of the
British  Fresh-water Algse, under the name of Hamatococcus Hooker-
iana.   (See Plate I. fig. 4.)   The cause which determines this  union
of the cells still requires "to be explained, and would seem to be referable
to a mutual attraction exerted by the globules on each other.  Andral
asserts  that when  the fibrin of the blood is abstracted, they do not
thus cohere.  Professor Nasse, as  already remarked, states that  this
disposition on the part of the red corpuscles to unite together and form
rolls (as of  miniature money in  appearance), is increased in inflamma-
tory blood.   The union does not, however, last long; a heaving to and
fro of the strings of corpuscles soon taking place, and which terminates
in their disruption.*
  * In reptiles, birds, and fishes, the red globules are elliptical, a form possessed also
by some few mammalia, chiefly of the family Camelidce. This fact was discovered
by Mandl, in the dromedary and paco; and subsequently by Gulliver, in the vicugna
and llama. The oval  globules of these animals, however, could not be confounded
with those of reptiles, buds, and fishes, than the corpuscles of which they are  so 
                             THEBLOOD.                         91

   Size.—The size of the red corpuscles of the blood, although more
 uniform than that of the white, is nevertheless subject to considerable
 variation.  Thus, the globules contained in a single drop of blood are
 not all of the same dimensions, but vary much.   These variations are,
 however, confined within certain limits: the usual measurement in the
 human  subject is estimated at about the 35V0 of and inch; but, occa-
 sionally  globules are met with  not  exceeding  the xj\j) and,  again,
 others are encountered of the magnitude of the  3 2V 9 °f an mcn '> these
 are,  however, the  extreme  sizes  which present  themselves.*   The
 difference in the size of the red  corpuscles, which has been indicated,
 is a character common to them in the blood of all  persons, and at
 every age.   Another variation  as to  size  exists, which is,  that the
 corpuscles are larger  in  the embryonic and fcetal than  they are in
 adult existence.f  This observation is important, inasmuch as it seems
 to prove that the blood does not pass directly from the maternal system
 into the fcetal circulation, but that the corpuscles are formed independ-
 ently in the foetus.   In  states of disease, also, it has been remarked by
 Mr. Gulliver  that  there is even a still  greater  want of uniformity in
 the measurements presented by  the red corpuscles.

 much smaller, and, further, are  destitute of the central nucleus, which characterizes
 the blood globules  of all the  vertebrala,the  mammalia alone excepted.  The long
 diameter of the  blood  corpuscles of the  dromedary, Mr. Gulliver states to be the
 g-Jjy of an inch, and its short the -g^r > the first of these measurements exceeds but
 little the diameter of the human blood corpuscles.
  Among fishes, one exception to the usual oval form of the blood corpuscle has *
 been met with: this occurs in the lamprey, the blood disc of which Professor Rudolph
 Wagner observed to be circular; in form  then the blood corpuscles of the lamprey
 agrees with that of the mammalia, but in the presence of a nucleus, the existence of
 which has been  recently ascertained by Mr.  T. W. Jones, it corresponds with the
 structure of the blood discs of other fishes.
  * The first measurement given is that which is  usually adopted by writers; the
 last two are those made by Mr. Bowerbank for Mr. Owen, and which are to be found
 in the latter gentleman's paper on the Comparative Anatomy of the Blood Discs,
 inserted in the Lond. Med. Gazette for 1839.  The measurements which I have made
 of the human blood corpuscle do not accord with those which are generally regarded
 as correct: thus I find the average diameter of the blood globule of man to be, when
 examined in the serum of the blood, about the ^wrr of an inch, and in water in which
 the corpuscles are smaller, as  a necessary consequence of the change of form, the
3^.  The micrometer employed by me is a glass one, precisely similar to that
made use of by Mr. Gulliver, being furnished to me by the same eminent optician,
Mr. Ross, from whom his own was obtained.
  f  This is the opinion of Hewson, Prcvost, and Gulliver, and I have myself to some
extent confirmed its accuracy. 
92                   ORGANIZED  FLUIDS.
  •A  careful examination of the  elaborate tables of Mr. Gulliver on
the measurements of the blood corpuscles, appended to the translation
of Gerber's Minute Anatomy tends to show that  a general though not
a very close or uniform relation, exists between  the size of the blood
corpuscles  among the  mammalia, and that of the animal from which
they proceed.  These tables furnish more evidence in favour of this
co-relation than they do in support of the assertion that has been made,
that the dimensions  of the corpuscle depend upon  the nature of the
food.   It would appear, however, nevertheless, that  the corpuscles of
omnivora are usually larger than those of  carnivora, and these, again,
larger than those of herbivora*  In a  perfectly natural  family of
mammalia,  as the rodents or the ruminants, there is also an obvious
relation  between the size of the  corpusucle and that of the animal.
Gerber  states  that there  is an exact relation  between  the size of the
blood globules  and that of the smallest capillaries.   This observation
is doubtless strictly correct.
  Structure.—Much diversity of opinion has, until recently, prevailed,
and does still  obtain, although to a less  extent, in  reference to the
intimate structure of the red globule.  This diversity has arisen partly
from the imperfections of the earlier microscopic instruments employed
in the investigation, and in part is due to  the different  circumstances
in which observers have  examined the blood corpuscle.  Thus, one
micrographer would make his observations upon it in  one  fluid, and
another  in some other medium, opposite results and conclusions not
unfrequently being the  results of such uncertain proceedings.  These
discrepancies it will be the writer's endeavour, as far  as possible, to
reconcile with each  other, as well as to point  out those observations
which are entitled to our implicit belief, and those which yet require
confirmation.  This  being done, we  shall be in a  position  to  form
some  certain conclusions.  The earlier microscopic observers believed,
almost without exception, in the existence of a nucleus in the centre
of each  blood  corpuscle.   Into this belief they were  no doubt led
  *  The  largest  globules which have  as yet been discovered, are those of the
elephant;  the next in size, those of the capybara and rhinoceros; the smallest,
according to the observations of Mr. Gulliver, are those of the napu musk-deer.  The
corpuscles of the  blood of the  goat were formerly considered to  be the smallest.
The following are the dimensions given by Mr.  Gulliver of some of the animals
above named.  Diameter of corpuscle of the elephant, the ^Vt oi> an inch; of capybara
the 3^-8 5  0I" g°at>tne tfsW; and of naPu musk-deer y^y.  The white corpuscles
of the  musk-deer are as large as those of a man; a proof that the red corpuscles are
not formed, as many suppose, out of the colourless blood globules. (See the figs.) 
THE  BLOOD.
93
more from  analogy than from actual observation.   Now, analogy,
although frequently useful in the elucidation of obscure points, affords
in the present instance but negative and uncertain evidence.  In the
elliptical blood  discs of reptiles, birds, and fishes, a solid granular
nucleus does undoubtedly exist;  but the best optical  instruments, in
the hands of the most  skilful recent micrographers, aided by the appli-
cation of a variety of  reagents, have  failed, utterly, in detecting the
presence of a similar  structure  in the blood  globule of the human
subject in particular, and of mammalia in general.  I therefore do not
hesitate to join my opinion to that of those observers who deny the
existence of a nucleus in the blood discs of man and mammalia.*
   The  appearance of a nucleus is,  indeed, occasionally presented;
but this appearance has been wrongly interpreted.   An internal small
ring, under favourable circumstances, may be seen  in the  centre  of
each blood corpuscle:  this ring is occasioned by the central depression,
the  outer margin of which  it describes;  and it was the observance
of it  that gave to Delia Torre the erroneous impression,  that each
globule had a central perforation, and therefore was of an annular form;
and further, probably induced Dr. Martin Barry to describe it as a fibre.
   The very existence, on both surfaces of  the blood disc,  of a deep
central depression, together with its little  thickness, almost preclude
the possibility of the presence of a nucleus.
   An endeavour to account for the absence of a nucleus in the blood
corpuscle of the human adult has been made by supposing that it does
really exist in the  blood of the embryo.  The answer to this supposi-
tion is, that no nucleus is to  be found  in embryonic blood, and that if
it were, it would be no reason why the nucleus  should not also  be
met with in the blood  of the  adult, seeing that the blood disc is not a
permanent structure, as an eye or a limb, but one which is perpetually
subject to destruction  and renewal.
   Having then arrived at the conclusion that no nucleus exists  in
the blood corpuscle of man, we have now to ask  ourselves  the ques-
tion, what, then, is really the constitution of the red blood globule?
   Some observers have compared it to  a vesicle.  This  definition
does  not  seem to  be  altogether satisfactory;  for  although each
corpuscle possesses the endosmotic  properties  common to a vesicle,

  * Among those who have asserted their belief in the presence of a nucleus, may
be mentioned Hewson, Miiller, Gerber, Mandl, Barry, Wagner, Rees, Lane, and
Addison; and of those who have held a contrary opinion, Magendie, Hodgkin, Listen,
Young, Quekett, Gulliver, Lambotte, Owen, and Donne. 
94                   ORGANIZED  FLUIDS.
 no membrane, apart from the general  substance of the  globule, (I
 speak more particularly of the human  blood disc,) has been demon-
 strated as belonging to it.
   Each globule in man  may therefore be defined to be an organism
 of a definite form and homogeneous structure, composed chiefly of the
 proteine compound globuline, which resembles albumen very closely
 in its properties;  its substance  externally  being more dense than
 internally, it being endowed with great plastic properties, and, finally,
 being the seat of the colouring matter of the blood.
   The extent to which the red globule is capable  of altering its form,
 is  truly remarkable.   If it be observed  during circulation, it will
 be seen  to undergo an endless variety  of shapes, by  which  it
 accommodates  itself to the  space through which it has to traverse,
 and to the pressure of  the  surrounding  globules.   The  form thus
 impressed upon it is not, however, permanent;  for as soon as the
 pressure is removed, it again ■ instantaneously resumes its  normal
 proportions.  On the field of the microscope, however, the  corpuscles
 may be so  far  put  out  of form, as  to be incapable of restoration to
 their original shape.
   Some  observers have assigned to  the  red globule  a  compound
 cellular structure, comparing it to a mulberry.  It  need scarcely be
 said that such a structure does not really belong  to it.  A puckered
 or irregular outline is not unfrequently presented by many globules;
 this is due sometimes to evaporation, and then arises from the presence
 around the margin of the  disc,  and  occasionally  over the whole
 surface, of minute bubbles of air;* and at other times it is the result
 of commencing decomposition,  or the  application  of some  special
reagent, as a solution of salt, in which cases a true  change in the form,
but not in the structure  of the globule, does really occur;  its  outline
becomes irregular, and the surface presents numerous short and obtuse
points or spines.f  Globules in this state bear some resemblance to the
pollen granules of the order Compositae.%   (See Plate I. fig. 5.)
  * This vesiculated appearance of the blood corpuscles may  be produced at once
by pressure.
  f Mr. Wharton Jones says, "the granulated appearance"  seems to be owing to a
contraction of the inner and a wrinkling of the outer of the two layers of which he
conceives the wall of the corpuscle to be formed.
  I The opinions promulgated by some observers in reference to the intimate struc-
ture of the blood corpuscles are singular, and are  rendered interesting mainly by
reason of the ingenuity of the views expressed. Mr. Addison remarks:1 "Blood
    1 Experimental Researches, pp. 236, 237.  Transactions of Prov. Med.  and Surg. Association. 
THE  BLOOD.
95
   Colour.—The hcematine,  or colouring matter of  the blood, seems
in  the  red  corpuscle  of  the mammalia  to be  diffused  generally
throughout its substance; in the oviparous  vertebrata,  however, it is
confined to that portion  of each  corpuscle  which corresponds with

corpuscles, therefore, appear to consist of two elastic vesicles, one within the other,
and  to possess  the following structure:  1st, an external and  highly-elastic tunic,
forming  the outer vesicle;  2d, an inner elastic  tunic, forming  the interior vesicle;
3d, a  coloured  matter,  occupying the space between the  two  tunics; and  4th,
a  peculiar  matter, forming the central portion  of the corpuscle."  Mr.  Wharton
Jonesl ascribes a somewhat similar constitution to the blood corpuscle:  " The thick
wall of red corpuscle," he says, "consists of two  layers.  The outer is  transparent,
colourless, structureless, and resisting, and constitutes about one-half of the whole
thickness of the wall.   The inner layer is softer and less resisting;  and is  that
which is the seat of the colouring matter."  Dr. G. O. Rees and Mr. Lane 2 describe
the blood corpules as containing a fluid, and provided with a nucleus composed of a
thin and colourless substance.  The views of Dr.  Martin* Barry are, however, the
most peculiar of any ever yet published in reference to the blood corpuscle; when first
they were announced  in the pages of the Philosophical Transactions, the scientific
world were taken by surprise and wonderment.   Microscopes, which had long been
suffered to remain undisturbed on  their  shelves, were immediately had recourse to,
and  many scientific men, who previously had never employed the instrument in their
investigations, were induced to procure it, in order that they might themselves bear
ocular witness of the  astonishing  facts related by Dr. Barry in reference to blood
corpuscles.   A short abstract of  Dr. Barry's views will be read by some with interest.
Dr.  Barry considers  that the molecules, the red corpuscles, and  the white globules,
are different states of the development of the same structure, the true blood globule.
(This  is also the opinion of Addison  and Donne.)  The  first he denominates a
"disc," and the last a "parent cell."   These different stages in the development of the
blood globule, Dr. Barry compares  with similar conditions of the germinal vesicle of
the ovum.  "The disc," he says, "is the most primitive object  we are acquainted
with;" that it is synonymous with the "nucleus" of most authors, and  the "basin-
shaped granules" of Vogel; that it "contains a cavity, or depression," "the nucleo-
lus," which " is the situation of the future orifice," which he says the blood corpuscle
in certain states  exhibits, and "by means of which there is a communication between
the exterior of the corpuscle and  the cavity in  its  nucleus;"   lastly, the disc is
regenerated by fissiparous divisions.   These discs are also denominated, " primitive
discs," "foundations of future cells."  The "parent cells" he conceives to be made
up of an assemblage  of  these discs.  Again, Dr. Barry states,  "The  nuclei of the
blood corpuscles furnish themselves with cilia, revolve, and perform locomotion;"
"the primitive discs exhibit an inherent contractile power."   And of the corpuscles
themselves, he remarks, "Molecular motions are discernible within the corpuscles of
the blood,"—"changes  of form are observed under  peculiar circumstances in  the
corpuscles of the blood."   These are, however, only the beginning of wonders related.
Dr. Barry elsewhere goes on to observe:  "In the mature blood corpuscle (red blood
      1 See British and Foreign Medical Review, No. xxvm.   2 Guy's Hospital Reports, 1840. 
96
ORGANIZED  FLUIDS.
  the  blood  disc  of  the  mammiferous  vertebrata,  viz:  the outer  or
  capsular portion of it—the nucleus  which alone exists in the blood
  corpuscles  of birds, fishes, and  reptiles,  being entirely destitute  of
  colouring matter.
    The  colour of the  blood,  it  has long been believed, is  intimately

  disc), there is often to  be seen a flat filament or  band already formed within the
  corpuscle.  In Mammalia, including man, this filament  is frequently annular;  some-
  times the ring is divided at a certain part, and sometimes one extremity over-laps the
  other.  In birds and amphibia the filament is of such length as to be coiled.   This
  filament is formed of the discs contained within the blood corpuscle...  "The fila-
 ment thus  formed w7ithin the  blood corpuscle has a structure which is very remarka-
  ble.   It is not only flat, but deeply grooved on both surfaces," in an oblique manner.
 "It is deserving of notice," continues Dr. Barry, "that in the first place, portions of
 coagulum of blood sometimes consist of filaments  having a structure identical with
 that of the filaments formed within the blood corpuscle; secondly, that in the coagu-
 lum I have noticed the ring formed in the blood corpuscle of man, and the coil formed
 in that of birds and reptiles, unwinding themselves into the straight and often parallel
 filaments of the coagulum, changes which may be  seen  also taking place in  blood
 placed under the microscope before  coagulation;  thirdly, that  I  have noticed similar
 coils strewn through the field  of view when examining various tissues, the coils here
 also appearing to be altered blood corpuscles and unwinding; lastly, that filaments
 having the  same structure as  the foregoing, are to be met with  apparently in every
 tissue of the body."  These filaments Dr. Barry conceives finally to constitute "fibre,"
 whenever this elementary structure is encountered.
  These multiplied and extraordinary observations of Dr. Barry, it is now necessary
 to observe, remain unconfirmed in all the most essential particulars up to the present
 time.  Shortly after their  promulgation, Dr.  Griffiths,1  and Mr. Wharton Jones,2
 objected  to the statement of Dr. Barry, that there exists in the blood corpuscle a pri-
 mordial fibre, observing that the appearances relied upon were due to decomposition.
 In connexion with the subject of fibre in the blood globules, the analogy referred to
 by Dr. Willshire, 3 between a dark line observed in the starch vesicle, and Dr. Barry's
 alleged fibre, may be noticed, as well as the affirmations of Dr. Carpenter, 4 that Dr.
 Barry had shown him, among  corpuscles of the blood of the newt, preserved in its
 own serum, many of a flask-like figure, and which  might be compared to  a pair of
 bellows, and the projecting portion of which  appeared to Dr. Carpenter to be a fila-
 ment having a much higher refracting power than the general  substance of the cor-
 puscle. Dr. Barry also showed Dr. Carpenter, in blood preserved in corrosive sublimate,
a corpuscle which was evidently destitute of the ordinary nucleus, and which contained
what  appeared to be a  filament, presenting transverse oblique markings  which
resembled those of the fibrillae of a muscle.  The observations of Dr. Barry, and the
confirmatory statements  of  Dr. Carpenter, will at least  be possessed of historical
interest, if any real and intrinsic importance be denied to them.  The views of  Dr.
Barry are given at length in the Philosophical Transactions for 1840__1843.
  1 Annals of Natural History February, 1843.  2 Transactions of the Royal Society, December 1842.
  3 Annals of Natural History, 1843.          * Annals of Natural History, 1842. 
THE  BLOOD.
97
connected with the presence of iron in the blood corpuscles: from the
fact, however, that iron exists in the chyle,* and in the colourless
blood of certain animals, f it is clear that the mere presence of iron is not
in itself sufficient to account for the colour of the blood;  this depends
most probably upon the state of combination of the iron  in the blood.
   Liebig  states, as will  be shown immediately, that  the iron  in the
blood  exists in  the varying  conditions  of  peroxide,  protoxide,  and
corbonate of the protoxide of iron.

                     OSES  OF THE  RED CORPUSCLES.
   In  connexion with Respiration.—Observation  has taught us the
fact that the colour of the blood changes considerably, according as it is
exposed to the influence of oxygen and carbonic acid gases;  it becom-
ing bright red under the influence of the  former, and dark red, almost
black, under that of the latter gas.
   Now, the microscope has revealed to us the additional fact that the
colouring matter of  the blood resides within the red corpuscles;  and
hence we are led to infer that the changes of colour alluded  to are
accompanied by alterations  in the condition of the colouring matter
contained in those  corpuscles.
   Further,  the alterations  of colour which have been mentioned take
place not  only in blood withdrawn  from the system, but also in that
which still  circulates in the living body, the vital  fluid being exposed
in the lungs to the influence of the oxygen contained in the atmosphere,
and to carbonic acid in  the capillary system of vessels.
   But it is  not merely a change of colour which the blood undergoes,
or rather  the coloured blood corpuscles undergo, on exposure to either
of the gases particularized, but they also experience at the same time,
as might  easily be  inferred,  a positive change of condition, a portion
of one or other of the gases to  which the  blood corpuscles are exposed
being imbibed by them.
   That it is really the red  corpuscles which  absorb the oxygen, or the
carbonic  acid, as  the case may be, admits  of demonstration, and  is
proved by the fact  that these gases lose but little volume  when placed
in contact with the liquor sanguinis, or  serum of the blood.

  * See article " Lymphatic System," by Mr. Lane.  Encyclopardia of Anatomy and
Physiology,  April, 1841.
  f "The Blood Corpuscle considered in its different  Phases of Development in the
Animal Series," by J. W. Jones, F. R. S.  Transactions of the Royal Society, part ii.
for 1846.
                              7 
98
ORGANIZED FLUIDS.
   It is clear, then, that the coloured corpuscles are the seat in which
these changes  occur.  Again, from the fact that  the  blood becomes
bright red or arterial on exposure to oxygen, as in the  lungs, and dark
red or venous  on being submitted to the action of carbonic  acid, as in
the capillaries, it has  been inferred  that they are, first, carriers of
oxygen from the lungs to all parts of the system, and, second, vehicles
for the conveyance of carbon back again to the lungs.
   This inference is correct  as far as it goes, but it fails  to explain
why  the  imbibition of oxygen or carbonic  acid gases should be
accompanied by changes in the colour of the  blood;  and it also fails
to show why those gases themselves should be imbibed.
   From the constant presence of iron in the coloured blood corpuscles,
it has been inferred that this is the base with which the oxygen and the
carbonic acid gases combine,  but  the exact nature of the combi-
nations thus formed it was reserved for the illustrious  Liebig to make
known.
   Liebig declares that, in arterial blood, the iron is in the  state of a
peroxide, and in venous blood in the condition of a carbonate of  the
protoxide.
   To this conclusion Liebig has arrived  by observing the manner in
which the  above-mentioned  compounds of iron comport themselves
when not in connexion with the blood, but when exposed to the same
influences as the blood  itself is subjected to.
   Thus, he says, " The  compounds of the protoxide of iron possess  the
property of depriving other oxydised compounds of oxygen, while  the
compounds  of peroxide of iron under other circumstances give up
oxygen with the greatest facility."
   Again, " Hydrated peroxide of iron, in contact with organic matters
destitute of sulphur, is converted into carbonate of the  protoxide."
   Lastly, "Carbonate of protoxide of iron in contact with water and
oxygen is  decomposed, all the carbonic acid is  given off, and  by
absorption of oxygen it passes into the hydrated peroxide, and which
may again  be converted into a compound of the protoxide."
   Now, the above-described changes, which the compounds of iron
when exposed to the same  influences as the blood  corpuscles are
themselves submitted to, precisely correspond  with those alterations
which it is  known and ascertained that the blood corpuscles do them-
selves experience, and therefore there is every probability in favour of the
strict accuracy of Liebig's explanation of the chemical  changes which
the blood corpuscles pass through during respiration and circulation. 
THE  BLOOD.
99
   Thus, it has been long known, that in the lungs the coloured blood
 corpuscles give off carbonic acid, and imbibe oxygen: and it has also
 been ascertained that during  their circulation they lose a portion of
 their oxygen, and acquire carbon.
   Venous blood, then, exposed to the air, gives out carbonic  acid, and
 absorbs oxygen; but arterial  blood, submitted to the same influence,
 gives out oxygen, and acquires carbonic acid; the seat of these changes
 being the red corpuscles.
   It will be  seen, on reflection, that, according to the views  just pro-
 pounded, the surplus amount of oxygen which exists in  the  peroxide,
 becomes  disengaged in the reduction of that oxide to the state of
«protoxide: during circulation in the capillaries, this surplus  is  chiefly
 expended in the elaboration  of the  different secretions  which  are
 continually being formed in the various organs of the body.
   Such is the corpuscular theory of respiration.  Hereafter we shall
 have to  speak of a  corpuscular  theory  of nutrition,  growth, and
 secretion.
   In connexion with Secretion.—It is very probable that the use of
 the  red corpuscles is not limited to the mere office of carrying oxygen
 from the lungs to be distributed to all parts of the system, and of carbon
 back again to the lungs to be eliminated, but  that they have an ulterior
 and additional function to discharge.   Thus, some observers suppose
 that they exert some influence over the constitution of the blood itself,
 elaborating, from the materials continually thrown into it by the tho-
 racic duct, a further quantity of fibrin.  There is more reason to believe,
 however, that it is the white corpuscles which are principally concerned
 in this process of elaboration, seeing that their structure agrees with
 that which is generally possessed by true secreting cells.   I  therefore
 myself would be inclined to attribute to the  red corpuscles  but little
 influence over the constitution of the blood.
   It may be stated that both  Wagner* and Henle are of opinion that
 the  red corpuscles are connected with secretion, and the latter, in his
 "General Anatomy," calls them "swimming glandular cells."

                        Effects of Reagents.

   The blood  globules are much modified by tne application of numer-
 ous  reagents, and which, therefore, may be employed with advantage
 in their investigation.
*  Physiology, by Willis, part ii. p. 448. 
100                  ORGANIZED  FLUIDS.
   Serum.—It has already been observed  that, in the serum of the
 blood,  their natural element,  the. globules preserve  unaltered, for a
 time, their normal form.
   Water.—The  application of  water  causes the  globules  almost
 immediately to lose their flattened and discoidal character, the depres-
 sions on their surface are effaced, and  they become spherical.  This
 change in the form of the corpuscles is  necessarily accompanied by a
 diminution of their size.   (See Plate I. fig. 3.)
   Spirits  of  Wine, Mther, Creosote.—The  same results follow  the
 use  of a variety of liquids, as spirits of wine, aether and creosote.
 These  agents, however, in addition, render the globules  exceedingly
 diaphanous, so much so indeed as  that  they are often with difficulty ,
 to be discovered.  In the globules rendered thus transparent, no traces
 of granular contents can be detected.
   Acetic acid.—This preparation first deprives the globules of their
 colouring  matter, thus rendering them  exceedingly transparent, and
 subsequently  dissolves the human blood corpuscle, without residue,
 but  not that  of  a frog, &c, the nucleus  of which  remains entire.
 (See Plate II. fig. 5.)
  Ammonia.—This alkali acts in a similar manner.
  Nitric Acid,  Muriate  of  Soda.—These   reagents  contract the
 globules, and render their outline more distinct.
  Iodine.—This  likewise renders the outlines more distinct, without
 at the same time deforming and otherwise altering the globules.
   Corrosive Sublimate.—In a strong solution of this liquid, the outlines
 of the globules are more defined, and the globules may be preserved
 for examination for a considerable length of time.
  We shall next  pass to the consideration of  the white  globules, and
 show in what particulars of form and structure they differ from the red.
                           WHITE  GLOBULES.
  The white globules of the blood are by far  less numerous than the
 red; they nevertheless are more abundant than a superficial observer
 would suppose: this arises from the fact that many of them are con-
 cealed from view on  the field of the microscope by the red globules,
 which so greatly  outnumber them.  The white corpuscles differ from
 the red  in several particulars: in  size, in colour, in  form, in structure,
 in their properties, and doubtless  also in their uses.*
  * Spallanzani was the first to  notice the existence  of  two forms of globules in the
blood of salamanders; Miiller verified their presence in that of the frog, and M. Mandl
detected them in man and mammalia. 
THE  BLOOD.
101
  Size.—In man and the mammalia the white globules are generally
larger than the red: like those, also, their dimensions vary very con-
siderably in the blood of the same individual abstracted at any given
time, and even to an extent still greater.   Their average  size, when
contained in  the serum of the blood, may, however, be estimated at
about the -^iis °f an inch* (see Plate I. fig. 1): when immersed in
water, however, they swell up, and increase very considerably in size,
in this liquid sometimes measuring the ttVo oi" an inch.   (See  Plate I.
fig. 6.)   In the blood of reptiles,  especially in that  of the  frog, a
contrary relation between the size of the red and white globules exists;
the latter in these, instead  of being larger than the red corpuscles,
are two or even three times smaller.  This fact it is important  to bear
in mind, in considering the question of the transformation of the white
globules into red.
   Form.—Instead of being of a  flattened and disc-like form, as are
the red globules, the shape of the white corpuscle, when free, is in all
classes  of the  animal  kingdom  globular.  This  particular likewise
throws  much light upon  the  disputed point as to whether the white
globules become ultimately converted into red  corpuscles,  and which
we shall have to treat of more fully hereafter.
   Like  the red corpuscles, however, although to  a less remarkable
extent, the white globules, when subject to pressure, undergo a change
of form: this change is frequently well seen when viewing the circu-
lation of the blood in the capillaries, the white corpuscles often  becom-
ing compressed between the walls of the vessels and the current of
red blood discs, and by which compression they are made  to  assume
elongated and oval  forms; like the red corpuscles, also, they immedi-
ately regain their normal  form, the pressure being removed.
  Structure.—In almost  every relation which can be named, the
white globules would appear to be the antagonists of the red;  for,
instead  of being of a homogeneous texture, they are of a granular
structure throughout, each full-sized white globule  being constituted
of not less than from twenty to thirty distinct granules, the presence
of which imparts to it  a  somewhat broken outline: these granules
are often seen, especially after the addition of water, and some other
reagents, to be in a state of the greatest activity in the interior of the
corpuscles.  It is only in  the  blood globule of mammalia, however,
that we find this antagonism to prevail.  The blood corpuscle of the
  * Mr. Gulliver gives the -^^ of an inch as the average measurement of the human
colourless blood corpuscle. 
102
ORGANIZED  FLUIDS.
frog, and doubtless of other reptiles, as well as birds  and fishes, is
assuredly a compound structure, the investing or transparent part of
each being in no way, as regards structure, distinguishable from the
substance of the human blood disc,  and  the nucleus also being iden-
tical in composition, though not in origin, with the white globules of
the blood,  not  merely of mammalia, but likewise  of reptiles, birds,
and fishes.   (See Plate II. fig. 5.)   The form of the  nucleus, in the
frog, &c., corresponds with that of the globule;  that is,  it is elliptical
(see  Plate  II. fig. 2):  water, however, affects  the nucleus, as  first
observed by Mandl, in the same way as it acts upon the corpuscle
itself, rendering both perfectly spherical.   (See Plate M.figs. 3 and 4.)
If to globules in this condition acetic acid be added, the capsule will
be dissolved, leaving intact the nucleus, between which and a white
globule I have not been able  to detect, although using an instrument
of the very best description, the slghtest structural difference:  a dif-
ference does certainly exist, but it is one of size, and not of structure,
the nucleus being three or four times smaller than a white globule of
ordinary dimensions.   (See  Plate II. fig. 5, and Plate  II. fig.  1.)
This identity  of organization between the  white globule and the
nucleus of the blood disc of the frog, furnishes the strongest evidence
with which I am acquainted  of  the convertibility of the white glob-
ules into red, evidence which, nevertheless, I regard as  wholly inade-
quate to  demonstrate the reality of the conversion.
  Nucleus.—The white corpuscles, under some circumstances, would
appear to be nucleated; thus nuclei are  evident in  corpuscles which
have been immersed in water, or even in serum, for any length of
time, although they are not usually  seen in those of that fluid imme-
diately after its abstraction from the system.   I am inclined to regard
their formation as resulting partly from  the operation  of endosmosis,
whereby a portion of the contents  of each corpuscle becomes con-
densed in the centre.
   The nucleus occupies  sometimes the  entire of the  interior of the
corpuscle, a narrow and colourless border destitute of granules, alone
indicating the extent of the corpuscle; generally, however, it is about
the one-third of its  size, and is more frequently eccentric than centric.
It is usually darker than the  rest of the  corpuscle, and  would appear
to contain a greater number of molecules.   (See Plate  I. fig. Q)
Sometimes it presents  to the eye of the observer the appearance of
an aperture; this appearance, although very striking, is most probably
fallacious. 
THE  BLOOD.
103
   Mr. Addison regards the nucleus presented by the white corpuscles
as primary, an opinion in which I concur.
   Properties.—The white corpuscles of the blood differ not less in
their properties from the red than they do in form  and structure:
thus, acetic acid, which dissolves the latter, contracts  somewhat the
former, and renders the contained granules more distinct; in water,
the red globules become globular and smaller in size, while the white
increase considerably in dimensions in the same liquid (see Plate  I.
Ug. 6), and finally burst in it, their molecular contents escaping.  In
liquor potassa, both the red and white corpuscles are  destroyed and
dissolved;  previous to which, however, in the white  globules,  some
interesting changes are seen to take place; immediately on the appli-
cation of the alkali, the  molecules contained in their  interior are
observed to be in  active motion, and in a short  time  the  corpuscles
burst  open, or explode, discharging numerous granules,  amounting
sometimes to  thirty or forty;  and which, together with  the  transpa-
rent matter of the corpuscles, finally becomes dissolved.—"Frequently,
when the liquor potassae  is acting with  diminished energy, the  cor-
puscles give a sudden jerk, and in  a  moment  enlarge to double or
three times their  former  size, without losing their circular outline:
the molecules and granules within them are more widely separated
from each  other, but not dispersed;  and they are seen held together,
or attached to the tunic of the corpuscle, by delicate connecting fila-
ments.   This singular and instructive change does  not,  of course,
last long; the alkali, continuing its action, ruptures the  tunic of the
corpuscle, dispersing and  dissolving its contents."—Addison.
   When examined  in the living  capillary vessels, they are seen to
manifest different properties to the red, and also to have a very different
distribution in those vessels.   Thus, the white corpuscles  frequently
adhere to the  inner wall of the capillaries, which the  red  rarely do;
and while the  red globules, in  circulating, occupy the centre of each
vessel, the  white corpuscles are placed between this and the walls of
the vessel.
  A difference may  also be observed in the relative speed with which
the two kinds  of corpuscles circulate, the red flowing onwards with
greater rapidity than the white.   The forces which  determine the
circulation in  the vessels would appear to act only on the red cor-
puscles, the motion of the  white globules being entirely of a secondary
and indirect character, it being communicated to them  by the  edge
of the current in the axis  of which the red corpuscles move, in the 
104
ORGANIZED FLUIDS.
same way as the stones at the bottom of a stream are rolled over and
borne onwards by the superincumbent water.
  The  cause of the  slower motion of the white corpuscles in the
capillaries may be thus explained.   A greatly retarded motion of the
fluid circulating in any vessel or channel is always observed towards
the periphral border of the current.   This  retardation would  appear
to arise from  the  resistance which the circulating  fluid  encounters
by  coming in contact with  the walls of the vessel or sides of the
channel through which it flows.
  In what way, however, is the difference in the position in the ves-
sels occupied by the red and white corpuscles to be  explained?  why
do the former always circulate in  the  axis of the vessel, while the
latter are constantly placed outside  this? and what is the inferenbe to
be deduced from this difference in their situation ?
  The red corpuscles, as we know,  are flattened discs, constituted of
an elastic and yielding material; and  the white, on the contrary, are
globular bodies of a more dense composition and of but little elasticity.
Now, it is very probable that  the peculiar  form and properties pos-
sessed by the coloured corpuscles of the blood may result  in such  an
adaptation and arrangement of them,  the one with the  other, that a
physical impossibility  is presented to  their indiscriminate admixture
and circulation in the same vessel with the white corpuscles.
  But there are other facts which will serve to explain the difference
of position:  Thus,  the  red  corpuscles have  an attraction  for  each
other, as is manifested on the field of the microscope by the formation
of the strings of corpuscles already referred to, where also it is  seen
that they have  no such  affinity for  the  white corpuscles,  which
usually lie detached and isolated from the  red.   On  the other hand,
however, the white, as before stated, have an attraction for the walls
of the vessels through which they pass, and which is declared by
their frequent adhesion thereto.
  The question may be asked, have these attractions any thing to do
with electric conditions?  All the inquiries which have been under-
taken, with the view of proving that the blood is possessed of electric
properties, have hitherto signally failed to demonstrate the existence
of any.
  Lastly, what inference is to be deduced from the different positions
occupied by the two kinds of blood corpuscles, and from the different
rates of their circulation in the capillaries ?
  The rapid passage  of the red corpuscles through the  capillaries, 
THE  BLOOD.
105
 together with their central situation, would lead the observer to infer
 that they had but little  direct relation with  the  parts outside those
 capillaries; that the office discharged  by them was one of  distribu-
 tion ; whereas the slow progress of the white corpuscles  through the
 capillary vessels, as well as their  peripheral position, would lead to
 the conclusion  that a close relation existed between them  and the
 parts adjacent and external to the vessels.  Now, these deductions
 are precisely those which other facts and observations tend to con-
 firm and establish, as we have already seen  in reference to the red
 corpuscles, and as we shall immediately proceed  to show in relation
 to the white globules.
   While viewing the capillary  circulation,  it is easy to  convince
 oneself that no contraction of the  parietes of the capillaries occurs,
 and that,  therefore, the motion  of the blood is  independent of any
 action of those vessels themselves, on their contents.

                    USES OF THE  WHITE  CORPUSCLES.
   The uses of the white corpuscles have not as yet oeen fully deter-
 mined;  enough, however,  of their nature  has  been  ascertained to
 show that they are closely connected with the functions of Nutrition
 and Secretion.   We shall here invert the natural order in which the
 description of  these subjects should be entered upon, and speak first
 of secretion.
   Uses in  connexion  with Secretion.—It would  appear that, for the
 most part, secretions  are formed in cells:  the  correctness of this
 statement is, in some degree, proved by the fact that the lower classes
 of the vegetable kingdom are entirely constituted of cellular tissue.
   It is also further  supported by the fact, that the essential  structure
 of all glands in the animal frame is that of cells.
   It would appear, also, that the cells, entering into the  composition
 of a single organ, have the power  of producing more than one kind
 of secretion.   This  is witnessed in the  petals of many flowers, the
 cells of which frequently elaborate  fluids  of several distinct colours.
   There is much reason  to  believe, that  the granules, which are so
 constantly associated with the cells, are the active agents engaged in
 the production  of the secretion, the exact constitution of these granules
 determining the character of the  secreted product.
  Now, in  the  white  corpuscles of the blood we have precisely the
same granular constitution which is seen  to belong to cells which are
indisputably engaged in the process of secretion. 
106
ORGANIZED  FLUIDS.
   From the observation of these and other facts, Mr. Addison has
 been led to entertain  the opinion, that the white  corpuscles of the
 blood " are very highly organized cells, from which the special tissues
 and the secretions are elaborated."*   In continuation of this subject,
 Mr. Addison goes on to remark: "And it appears that the renovation
 of these tissues and secretions from the blood  does not take place by
 the  cells discharging  their  contents into  the general  mass of the
 circulating current, to  be  separated  therefrom  by some  peculiar
 transcendental and purely hypothetical selective process of exudation,
 through a  structureless  and transparent tissue,  but by being them-
 selves attached to,  incorporated with, and performing their special
 function in the structure."
   Thus, Mr. Addison conceives  that the fibrillating liquor sanguinis
 is formed  and elaborated in the  white corpuscles of the blood, and
 that it never exists in  that fluid in a  free state, and  that its presence
 in the crassamentum, and especially in that part of it which consti-
 tutes the buffy  coat, arises from the rupture  and destruction of the
 white corpuscles, and the escape  of their contents.   This  opinion  he
 supports by a series of ingenious experiments, one of which may  here
 be referred to.   The  tenacious  property belonging to mucus is  well
 known, in which respect, as well as in the smaller number of globules,
 similar to the  white corpuscles of the blood contained in it, it differs
 mainly from pus.  Now, by the addition of a drop of liquor potasses
 to a little pus, which wras previously white and opaque, and in which
 the  presence  of a  considerable number of white  corpuscles  was
 ascertained by means of the microscope, its appearance underwent a
 complete change, the pus became transparent and tenacious, presenting
 precisely the characters of mucus.   The fluid being  again examined
 microscopically, it was found that most of the globules were ruptured
 and  dissolved, and that the liquid portion of it fibrillated in the same
 way as  that of mucus, and that of the liquor sanguinis; from  this
and other analogous experiments  Mr.  Addison formed the conclusion,
that  the fibrillating liquor sanguinis  was derived  from  the white
corpuscles,  and that it  does not exist in the  blood  in a free condition.
  According to  Mr.  Addison, the secretions, "milk, mucus, and bile,
are the visible fluid results  of the   final  dissolution of the  cells."
 Hence,  therefore,  a secretion  is  the  result of the last sta^e of the
process  of  nutrition.   And, again, " If, therefore, the colourless blood
  * "Experimental Researches," Transactions of Prov. Med. and Surg. Association
 vol. xii. p. 260 
THE  BLOOD.
107
corpuscles be termed "parent  cells,"  they must  be considered as
pregnant with the embryo materials of the tissues and secretions, and
not with "young blood cells."        «
  It is scarcely necessary to observe that these highly ingenious
views of Mr. Addison are by no means established.  That the cells
of glands and their contained granules are intimately connected with
secretion, there are many facts to prove;  but that  the white corpus-
cles of the blood  are, in the animal economy, the special organs of
secretion, and also that the  secretions said to be elaborated by them,
escape from them, not by transudation  through their  membranes, but
are set free by the entire and final dissolution of  the corpuscles, are
views which cannot be safely adopted until much additional evidence
is adduced in support of them.
  The opinion entertained by Dr. Barry, that the colourless corpuscles
are "parent cells," seems to me to be purely hypothetical.
   Let us now bestow a few reflections upon Nutrition:
   Uses in connexion with Nutrition.—That the white corpuscles are
concerned in the process of nutrition, there is more evidence to show
than there is in favour of their connexion with that of secretion.  The
question to be solved, however, is, in what  way do these  corpuscles
administer to  nutrition ? do they contribute to  nutrition and growth,
by  their  direct  apposition  to  and incorporation  with the different
tissues of organs?  This is the opinion of Mr. Addison, who says of
them,  that  they are the "foundations of the tissues and the  special
secreting cells, the link  between the  blood and the more solid  struc-
tures, the unity from which the pluralities arise."
  Dr.  Martin Barry also adopts the notion that tissues are  formed by
the direct apposition of the blood  corpuscles.   Dr. Barry makes no
exact distinction  between  the red and the colourless  globules; but
from the fact of his calling the latter "parent cells" filled with "young
blood discs," it would appear that he considered that the red corpuscles
gave origin to the different structures of the body by their direct union
and incorporation with each other.   This view is far less tenable than
that of Mr. Addison, and neither is supported by a sufficient number
of facts to render its accuracy any thing but exceedingly problematical.
  That the white  corpuscles of the blood are engaged in the process
of nutrition is proved by the fact, that they are found in  increased
quantities in vessels which are actively administering to that function.
This  accumulation is witnessed also in the capillary vessels of any
parts  which are  subjected to irritation of  any sort, and in which, as a
consequence of  that irritation, there is augmented action. 
108                  ORGANIZED  FLUIDS.
  The gradual collection of the white  corpuscles of the blood in the
capillary vascular  net-work, may  be seen  to  the  greatest possible
advantage in the tongue of the  frog, as  also in the web of the foot ot
that coveniently-formed creature, as the result of continued exposure
of the parts to the action of air.*
  But it is not alone the aggregation of the colourless corpuscles that
may be seen in the  minute vessels; their  escape from those vessels
may likewise be determined by a prolonged examination of them.   If,
after  the continuance of this  congested condition of the vessels for
twenty-four or  thirty-six  hours, they are  again examined,  it will be
obvious that certain of the corpuscles have  become entangled in the
fibres which form  the walls of the vessels, and that  certain others
have  altogether  passed the boundaries of the  vessels,  and now lie
external to  them.
  Again, it is asserted, that the epithelial  cells are derived from the
white  corpuscles of the blood.  If this be  correct, it would  appear
that the escape of these  corpuscles  is a perfectly normal and natural
occurrence.
  Thus far, then, the endeavour to prove the transformation of the
colourless corpuscles of the blood into tissue cells, would appear to be
successful;  but it is here  the chain of evidence breaks; and beyond
the fact,  which is by no  means established,  of  their constituting
epithelial cells, we have no further proof to adduce of  their structural
incorporation with the living tissues.  Of this occurrence it would, of
course, be difficult  to procure  satisfactory demonstration, on  account
of the  opacity of the parts on which our examination would have to
be conducted.   It may be remarked, however, that, if founded in fact,
we should  expect  to find a greater correspondence  in  the size  and
form, &c,  of the elementary tissues, with that of the corpuscles from
which, according to some observers, those tissues are derived.f
   The corpuscular theory of nutrition, then, proposed by Mr. Addison,
  * Mr. Addison states  that, in order to insure a satisfactory exhibition of this
important and curious phenomenon, the parts should be irritated in some manner, as
by immersion for a minute or two in warm water at a temperature of 95° Fahrenheit,
or by permitting a few crystals of common salt to  dissolve upon it.  These
methods I have tried, and have found that they have usually resulted in the entire
cessation of the circulation in the capillaries, and this has been also the case even
when a weak solution of salt in water has been applied.
   f The cells of the liver and spleen resemble closely in appearance the white cor-
 puscles of the blood; between them, however, well-marked differences  exist, so that
 it is by no means to be inferred that the former are derived directly  from the latter. 
                          THE BLOOD.                       109

in the present state of our knowledge, can only be sustained by having
recourse to a certain amount of theoretical reasoning or to particular
assumptions.
   The fact, however, still  remains to  us, that the white corpuscles
are concerned in nutrition,  although the precise manner in which they
are so is still open to investigation, and this fact is strengthened  and
confirmed  by  the phenomena  of disease.   Thus,  there  is  much
evidence to show that, wherever  nutrition is impeded, the  colourless
corpuscles accumulate in increased quantities in the vessels; and it is
by this  accumulation,  also, that we are  enabled to account for the
critical  abscesses and discharges which characterize some affections,
and to recognise the importance which ought to be attached to their /
occurrence.
   That the  colourless  corpuscles are really  present in  increased
numbers in the blood, in disease, is attested by the evidence of numer- ""
ous observers: thus, Gulliver,* Davy,f and Ancell,J have  observed
them in unusual quantities  in inflammatory affections,  and  especially
in such  as  are attended with suppuration.   Mr.  Siddall  and Mr.
Gulliver have repeatedly observed them in vast numbers in the horse,
especially when the animal  has been suffering from influenza.   Donne
has likewise  recognised their  presence  in  increased quantities in
disease; and Mr.  Addison finds  them to  abound in the hard and red
bases of boils  and pimples, and in the  skin in scarlatina  and in most
cutaneous affections.
   Several processes may have been pointed out by which the white
globules may be separated from  the red, and  thus be brought in  a
manner more satisfactory under view.   1st. Acetic acid dissolves the
red corpuscles, leaving the white  almost unchanged.  2d.  A drop of
water, floated gently across a piecs of glass, on which a small quantity
of blood has been  placed, will remove the red corpuscles, the white
remaining adherent to the surface of the glass.  This ingenious method
was, I believe,  first indicated by Mandl.   3d.  The third process
depends for its success upon the defibrination of the blood by whipping,
and which has  already been alluded to.  If blood thus defibrinated be
set aside for a time, the red globules will subside to the bottom of the
containing vessel, forming one stratum, and the serum will  floa&uptna
the top, constituting a second layer; but  between these two layers  a
              * Appendix to  Gerber's General Anatomy, p. 20.
              f Researches, Phys. and Anal., vol. ii. p. 212.
               \ Lectures in the Lancet, 1839-40, vol. ii. p. 777. 
110
ORGANIZED  FLUIDS.
third exists; this is very thin, and is formed by the  white globules,
which may be reached after the removal of the serum by means of a
siphon.*  Donne points out this  method in his  excellent  "Cours de
Microscopic"  4th. A fourth means  of procuring the white globules
is described by Mr. Addison.  If a portion  of fluid fibrin be removed
from beneath the pellicle which is first formed over the clot, it will be
found to contain numerous white globules.
  The observer, having satisfied himself of the accuracy of the various
facts brought  under his notice, in the next place will be prepared to
enter into the important questions as to the origin and destination of
the globules of the blood.   We will  consider  first  the origin of the
white globules.

                 ORIGIN OP THE GLOBULES OF THE BLOOD.
  The origin and end  of the blood globules! Whence do they come,
and whither do they go?  These are questions of the highest import-
ance ;  and it could be  wished that the replies to them were of a more
satisfactory and definite nature than those which  we are about to
make will, it is feared,  be considered.
  Origin of the White Globules.—Various  opinions have been enter-
tained in reference to  the nature and origin of the white  corpuscles
of the blood, the principal of which we will now  proceed to notice.
  One of the earliest notions formed  respecting the white  corpuscles
was that of Hewson, who believed that they were to be considered as
the nuclei of the red blood corpuscles, and hence he denominated them
"central particles:" to this conclusion Hewson was doubtless led by
observing the great and remarkable resemblance which exists between
the nuclei  of the blood globules  of  certain animals and  the white
corpuscles themselves.
  Two facts, however, are known, which satisfactorily prove that the
denomination  of central particles is not applicable to the white cor-
puscles, and that they do not form the nuclei of the red blood discs ■
the first of these is, that no nuclei exist in the true blood globules of
the entire class of mammalia in which white  corpuscles are abundantlv
encountered, and the  second is the great difference  in size observed

  * The position occupied in this  case by the white corpuscles shows that they are
of lighter specific gravity than the red, a reference  to which fact will also account for
their presence, in such quantities, in the buffy coat of the blood, and will  likewise
explain the reason why they first come into focus  when mixed with the red globules
in a drop of water. 
THE  BLOOD.
Ill
between the nuclei and the white corpuscles in those animals in which
the two organisms exist together in the blood.
  An opinion  somewhat similar to the above has been held by some
observers, viz:  that  the  white corpuscles  are to be regarded  as  the
"escaped nuclei" of  the red blood  corpuscles.  The facts adduced to
disprove the former notion respecting them, are likewise sufficient to
show the fallacy of that just referred to.
  By Dr. Martin Barry the white corpuscles  are considered to be the
last  stage of  the development  of the  red blood disc,  and he  has
assigned to them  the designation of "parent cells," under the impres-
sion that the granules, of which many are contained in each corpuscle,
become developed into  new  blood discs;  this idea of Dr. Barry is
purely hypothetical,  and  its accuracy is but little probable.
   Mr. Addison also believes  that the white  corpuscles represent  an
advanced condition of the growth  of the red blood disc, but he differs
from Dr. Barry,  however, in not considering them to be parent cells,
filled with  young embryos, designating the white  corpuscles "tissue
cells,"  under  the belief that they become  incorporated with,  and
constitute an integral portion of the solid structures of our frame-work.
The value of this theory has already been discussed.
   Mandl denominates the white corpuscles "fibrinous globules"  and
he  conceives  that the nuclei, which he states  belong to all red cor-
puscles of  the  blood, as  well  as the white globules, are  not primary
formations, but secondary; that these  structures do  not exist in the
blood while circulating within the body, but that they are formed after
its abstraction  therefrom;  and M. Mandl further states, that the steps
of  the formation of  the white globules  may be witnessed on the port
object of the microscope.  That this view is incorrect, not the shadow
of doubt can be entertained.   The regular form and size of the white
globules, their presence in the blood the moment after their abstraction
from the system, but especially the fact that they may be seen in vast
quantities  in  that fluid  while still circulating  in the capillaries, all
negative  the  idea of the formation of  the white globules out of the
system, in obedience to a mere physical law.
   Mr. Wharton  Jones, in a recent communication made to the Royal
 Society, has bestowed upon the white  corpuscles the appellation of
 '■granule cells,"  and that  gentleman considers them to  represent an
early stage in the development of the red blood globule.   The peculiar
 views entertained by Mr. Jones  will, however, be referred to more
 fully under the head of the origin  of the red blood disc. 
112                 ORGANIZED  FLUIDS.

  The white corpuscles are also synonymous with the "exudation
corpuscles" of many writers, and especially of Gerber, who has under
this denomination assigned to them  a false value; the presence oi the
white  corpuscles in  the  plastic fluid  of exudations  being rather
accidental  than essential.
  We come  now to refer to the  opinion  entertained respecting the
white corpuscles by Miiller, who denominated them "lymph corpus-
cles," conceiving them to be identical with the granular  corpuscles
encountered in the  lymphatic fluid.  Of all the opinions and theories
of the nature of the white corpuscles alluded to, that of Miiller  is
probably the  only correct  one; Miiller, however, was not acquainted
with their  existence in the blood of mammalia, but merely in that of
frogs  and other analogous  animals.
   The opinion that the white corpuscles are red blood globules in pro-
cess of formation, is one which is maintained  by many observers, and
nevertheless I regard it as erroneous.  In the truth of this view, Wagner,
Baly, Gulliver, Professor H. Nasse, and, above all, Donne, are believers.
From the excellent work of the latter writer I introduce the following
remarks in relation to this point:

   "About two hours  after injection (with  milk), rabbits, dogs, and
birds have been opened.   I have collected the blood in the different
organs, in  the  lungs, the  liver, and the spleen; every where I have
found the blood  in the  state in which  I have described it above,
 containing a certain number of white globules in all stages of formation,
 and of red globules more or less perfect: invariably the  spleen has
 presented  to me special circumstances so established and so  constant
 that it behooves me to mention them, and especially since they mav
 throw light,  at length, upon the true functions of this organ, so lonn
 and so vainly sought.   I  do not dare flatter myself with having com-
 pletely resolved this problem, and it is but with reserve that  I express
 myself in  this particular.
   "The  blood contained in the  large vessels of  the spleen  offers
 nothing very remarkable; but, in  expressing  that which  is  enclosed
 and, as it  were, combined with the tissue of this organ, one finds in
 it a composition well  worthy of fixing the attention.  In a word, this
 blood is  so rich  in white globules,  that their number  approaches
 nearly to that of the perfect blood globules; but,  further,  the white
 globules which  are  there, present  in as evident  a  manner all  the
 degrees of formation and  development, and  the examination of this 
THE  BLOOD.
113
blood does not appear to me to leave any doubt upon the transition
which I have  pointed out above of white globules to red  corpuscles,
and upon the successive phases through which the white globules pass
to arrive at the state of perfect blood globules.   This phenomenon is,
above all,  striking, after injections of milk,  and  during the  work,
which is accomplished in the  space of four-and-twenty hours, of the
transformation of the immense quantity of milk globules into blood
globules.  One cannot believe that this is not really the point—the
laboratory, if  one may  so  speak—in which this  transmutation is
effected, and that the spleen is not the  true organ of this important
function.   But I know how like  facts, and how  the theory which
results from them, have  need  to be confirmed  by the researches of
other observers, to be definitively adopted with confidence."*

   In  answer to these observations of M. Donne,  I would remark, first,
that I have never seen the different stages of formation of the white
corpuscles, and of transformation of these into  red, described by M.
Donne; and, second, that I believe that he has totally misinterpreted
the appearances presented by  blood pressed out of the spleen.  The
cells or  corpuscles, of which that organ is itself constituted, so closely
resemble the white globules of the blood, that I feel  assured that M.
Donne has failed to discriminate between the two, and that many of
his progressive stages of development  are  to be referred to the splenic
cells or  corpuscles, numbers of which are always contained in every
drop of blood procured from the spleen.
   Having now noticed the various  opinions held by different observers
in reference to the  nature of the white  corpuscles, we will next pass
to the consideration of their origin or mode of formation.  The idea
that the white corpuscles are elaborated by the lymphatic  glands, has
already been referred to; and,  from the absence of these glands in the
lower oviparous vertebrata, it is evident that they cannot be regarded
as essential to  their formation.
   It has been stated that, in addition to  the white and red globules,
numerous  smaller particles, termed  molecules, exist in the blood.
The white  globules, in all probability, derive their origin  from these
molecules, a number of them going to constitute a single white globule.
This  aggregation of  the  molecules into  masses, or globules, would
appear to result from the operation of a general  law of the economy,
under the influence  of which  the  globules  unite  with  each other,
                  * Cours de Microscopie, pp. 99, 100.
                             8 
114
ORGANIZED  FLUIDS.
 and become invested with a coating, or membrane, probably of an
 albuminous nature.
   Donne believes also that he has traced, by direct observation and
 experiment, the transformation of the minute oily and fatty particles,
 found in the milk, into white globules.   He injected numerous animals,
 birds, reptiles, and mammalia, with various proportions of milk, and,
 strange to say, the creatures thus experimented upon experienced  no
 injurious effect beyond a momentary shock, with, however, the single
 exception of the horse, to which the experiment proved fatal in seven
 different cases.  If, almost immediately after the injection of the milk,
 a drop of blood be withdrawn from the system at  a distance from the
 point where the milk was introduced, a number of the globules of the
 milk may be detected quite unaltered, and which  may be recognised
 by  their general appearance, their smaller size,  and, lastly, by the
 action of acetic acid, which dissolves the red globules, renders apparent
 the granular texture of the white, but leaves untouched the molecules
of the milk.  If the blood be again examined at about the expiration
of two hours, the smallest milk globules will be seen to have united
themselves with each  other by three's and four's, and to have become
enveloped, by circulating in the blood, in an albuminous layer, which
forms around them a vesicle, analogous to that which  surrounds the
white globules.   The largest remain single, but are equally enveloped
in a like  covering.  These soon break up into granules, in which state
the milk  globules bear a close resemblance  to the white globules  of
the blood, from which, finally, they are not to be distinguished.   " The
blood," Donne* remarks, "then shows itself very rich in white globules;
but, little by little, these undergo modifications  more and more pro-
found ;  their internal molecules become effaced, and dissolve in the
interior of  the vesicle,  the globule is depressed, and soon it presents a
faint yellow colouration:  they yet resist  better the  action of water
and acetic  acid than the fully-formed blood globules, and it is by this
that they are still to be distinguished.  At  length, after twenty-four
hours, or, at latest, after forty-eight, matters  have returned to their
normal state; no more milk globules are to be found  in the blood, the
proportion between the white globules and the blood globules, between
the imperfect and the perfect globules, has  returned  to  what it  is
ordinarily: in a word, the direct transformation of the milk globules
into blood globules is completed."
  In the  opinion that the milk globules are convertible into the white
globules of the blood,  Donne" is probably correct, although it must be 
THE  BLOOD.
115
an inquiry of much delicacy and  nicety to determine this point by
direct  observation.  The evidence, however, in favour of his latter
position, viz :  that  the white globules become ultimately  converted
into  red corpuscles, is much  more  defective,  and  the  facts upon
which  he relies to sustain this view are open to question, as we have
already seen.
  The view, then, of the transformation of white corpuscles into red,
I consider to be erroneous,  and that the  white corpuscles, as they
differ from the red, in  form, structure, and chemical composition, so
they also differ in origin; and that the two  forms of corpuscles are
in every respect distinct, as well in function as in  origin.
  From the fact of the white corpuscles of the blood being encoun-
tered in considerable quantities in  the lymph and  chyle, which is in
truth  blood in its primitive form, it is in  those  fluids, doubtless, that
they take their origin,  and it is in  them that they are best studied.
   Origin  of the Red Globules.—It has  already been shown that
Donne and others  consider that the red  globules  are formed out of
the white, which  they view as  true  blood globules which have not
reached the last degree of elaboration.  Donne  sustains  this  opinion
by reference to the following particulars:  First, that among  the red
globules contained in a single drop of blood, all are not affected to the
same extent by  the use of the same reagent; that some resist  its
influence for a much longer  period than others; Secondly, he states,
that he  has  observed  in some  true blood  globules traces  of a slight
punctuation, similar to that  which is seen in the  white  corpuscles;
and, Thirdly, in certain white globules he has noticed the compressed
form common to  the red corpuscles.  From the observation of these
facts, he draws the conclusion that the white globules are transformed
into red blood discs.  The first particular alluded to, viz:  that the
same reagent does not affect equally all the red globules of the same
blood, is doubtless to some extent  correct, and  may be explained by
supposing  that the red  corpuscles are not all of the same age, and
therefore are of different degrees of consistence.  The remarks as to
the granular texture of true blood corpuscles, and the compressed form
of certain white  globules, it has never happened  to me to be able to
verify in a single instance; and, for my  own  part, therefore, I am
inclined to allow to them but  very little weight  in determining the
question of the origin of the red  corpuscles of the blood.   To the
views  of M. Donne on  this point a high degree of plausibility and
ingenuity must certainly be accorded; but in considering this question, 
U6
ORGANIZED  FLUIDS.
not merely the doubtful and even  debateable nature of the evidence
adduced by M. Donne must be taken into consideration,  but also the
following  fact, viz: that no  definite relation  exists  in  the  animal
kingdom between  the size of the red and white  globules compared
together.   In man, and most mammalia, the white globules are larger
than the red (see Plate I. fig.  1); in most reptiles,  and  particularly in
the blood of the frog, they are very much smaller (see Plate 11.^. 1):
from whence it would result  that the process adopted by nature for
the conversion of  the white  globules into red,  would,  in  the two
classes of the animal creation cited, be of a character wholly different
the one from  the other.   In the  first-mentioned, the   transmutation
would  be  a work of decrease; in the second, of  increase, or  super-
addition; and  this supposition, I  conceive, would be  tantamount  to
charging nature with  the commission of a gross inconsistency.
  There are other observers, again, who believe in the formation of
the coloured blood corpuscles out  of the colourless ones, in a manner
totally  different from that described  by M. Donne.
  Thus, Mr.  Jones, in a communication  recently made to the Royal
Society, and entitled "the Blood Corpuscle considered in  its different
Phases of Development in the Animal Series," states  that the blood
corpuscle presents throughout the  animal  kingdom at least two phases
of development:  in the first of these, the corpuscle is granular, and in
the second, nucleated: when in the former phase, it is denominated
"granule  blood cell" and in the  latter,  "nucleated blood cell;" the
first condition, or that of granule  blood  cell, is synonymous with the
colourless corpuscle of the blood.
  But  each of these two phases presents likewise two stages in their
growth or formation; thus  the granule blood cell may be  either
coarsely granular, or  it may  be finely granular; and the nucleated
blood  cell  may be  either  uncoloured or coloured.  The first  three
stages  are encountered, according to Mr. Jones, in the whole  animal
series,  but not the fourth stage, the coloured condition of the nucle-
ated blood cell, which  is wanting in most of the Invertebrata, and in
one of the series of Vertebrate animals, a fish, the Branchiostoma
lubricum Costa; in  all the other divisions of the animal kingdom it is
present, as  in the Oviparous Vertebrata and the Mammalia.
  In the latter class,  the Mammalia, a third phase is super-added  to
the other two, that of a, "free cellceform nucleus;" this  appellation
expresses the usual condition in which the blood disc in the mammalia
is encountered, and in which  no nucleus can be discovered. 
THE  BLOOD.
117
  This third phase Mr. Jones  considers  to  be  derived  from  the
nucleated blood cell in its second stage;  the "free cellseform nucleus"
being the escaped nucleus of the nucleated blood cell.
  The facts by which this view is supported  are, first, a relation in
size between the  nucleus of the nucleated blood cell and the ordinary
blood disc, or "free cellseform nucleus," and second, the occurrence,
which is, however, very rare, of nucleated cells from which the nuclei
themselves have escaped.
  The "nucleated  blood cell" Mr. Jones  found abundantly in  the
blood of an embryo ox, an inch and a quarter long; very sparingly in
that of the elephant and horse, and not at all in the blood of the human
subject;  he encountered them, however, freely in the chyle of man.
  Such is a brief statement of the  views of Mr. Jones in reference to
the blood corpuscle, and of the chief  facts by which those views are
supported.  Without taking  upon myself  to pronounce upon them
decidedly, I yet must confess  that they carry  with  them  but  little
conviction to  my mind, and  that  the facts adduced to sustain them
are open to considerable discussion.
  If the  blood corpuscles of animals in general, and of the mammalia
in particular, pass through the successive phases and stages described
by Mr. Jones, how  happens it, I would ask, that in the blood of mam-
malia, and especially in that of man, while we meet with so abundantly
the  first stage of the first phase,  that of granule  blood corpuscle, viz:
the  coarsely granular stage, and also the last phase indicated by Mr.
Jones, that of free cellasform nucleus,  we do not frequently encounter
the  intermediate stages and phase, through which, according to Mr.
Jones, the blood corpuscles pass?  To this question I do not think it
easy to give a satisfactory reply, consistent with the opinions of Mr.
Jones.  The explanation which  I would give of the absence of these
transition forms is, that they have no real existence.
  According to Mr. Jones, the nucleated blood cells of the Oviparous
Vertebrata are of a nature totally distinct from the ordinary blood
cells of the Mammalia, which  have no nuclei, but that the nuclei of
the  blood cells of the former are  the analogues of the latter; this
opinion is  scarcely  consistent with the difference of  structure  and
chemical  composition observed between the  two.   Opinions  very
analogous to those  of Mr.  Jones in reference  to  the  nature of the
blood corpuscles of  the mammalia,  viz: that they are escaped nuclei,
appear to have  been entertained by Mr.  Gulliver from observations
made on the horse;  this gentleman supposing that  the  red corpuscle 
118
ORGANIZED  FLUIDS.
was the escaped nucleus of the white granular corpuscle, while Mr.
Jones conceives that the red blood disc is the liberated nucleus of the
same body, only in an advanced condition of its development, in the
stage of coloured nucleated blood cell.
   To the appellations by which Mr. Jones designates two of his phases
of the development  of  the blood corpuscle, an exception may fairly
be  taken.   The "granule blood cell" is frequently nucleated, even
while it still retains its granular structure,  and therefore the term
selected by Mr. Jones to indicate a condition of the  blood corpuscle
distinct from its granular state, viz: that of nucleated blood cell, is
inappropriate, and calculated to lead to the inference that the granule
blood cell is not a nucleated body.
   I reiterate then the opinion, that the white and red globules of the
blood are wholly distinct  from  each other—distinct in origin,  in
structure, and in function.
   The strongest fact with which I am acquainted (but it is one which
is not employed by M.  Donne) in favour of the transmutation of white
globules into red, is this, viz:  that the nucleus which exists in the blood
discs of the frog, and reptiles in general, is of a granular structure, in all
respects similar to that of a white globule, with the differences only of
size and form, the nucleus being four or five times smaller than the true
white globule, and of an oval instead of a circular outline.   (See Plate
ll.fig. 5.)   One of these differences, as already stated—viz: that of form
—is effaced by water, which renders the nucleus circular (see Plate II.
fig. 4), in which state the only distinction between it  and a white cor-
puscle, which can be detected, is the single one of size.  (See Plate II.
fig. 1.)  This difference, however, is so great, and coupled with the fact
that no  white globules have ever been detected in the frog, putting on
the characters of a true red blood corpuscle, that the opinion that the
white globules  are  transformed into red blood discs, must again be
abandoned.  The existence of a granular nucleus in the blood discs of
reptiles, &c, revives again the old notion, that the white ^lobules are
the escaped nuclei;  that they are not so, is proved by the fact that no
such nuclei exist in  the true blood globules of man and the mammalia,
in the blood of which white corpuscles abound.*  The blood discs, it

  * The following interesting remarks of Mr. Gulliver tend to confirm somewhat the
views of M. Donne; they are by no means  conclusive, however:—" White globules
about the same size as those in  the blood of man, and probably identical with the
proper globules of chyle and lymph, are common in the blood of birds, and particu-
larly abundant after a full meal in the  vultures and  other  rapacious families. 
THE BLOOD.
119
has  been  observed,  first make  their  appearance  in  the chyle: any
inquiries,  therefore, instituted with  the view of  determining  their
origin and development in  man, would be  more likely to prove  suc-
cessful if directed to the rigorous examination of that fluid.*
   In the last place, it remains to treat of the end or final destination
of the red globules of the blood.

             THE END  OR FINAL CONDITION OF THE  RED GLOBULES.

   Every where throughout the solid constituents of the animal organ-
ization, cellular tissue abounds;  it forms the basis of every texture and
organ of the  body.   It is, therefore, scarcely to  be wondered at that
the opinion should have been adopted, that the globules which exist
in such vast numbers in the blood were to be regarded as the primary
and even parent cells, out of which  all the solid structures of our
frame  took their origin.f   This  theory, to  the mind of the earlier
micrographer, must have appeared  very rational and  seductive; and
so great,  indeed, is the  plausibility with  which, even in the present

Some of the red discs, too, instead of the oval form, are often nearly or quite circular
in figure.  Hence the blood of these birds would appear especially favourable to
observe any changes in the white globules; and it seemed highly probable that these
might be transformed into the blood discs in the manner mentioned by Dr. Baly; but
although I made many observations with the view of determining this question,
nothing but negative results were obtained."—(Appendix to Gerber's  General Anato-
my, p. 24.)  This observation is satisfactory in one respect, viz: that it shows clearly
the connexion, which  has  already been  dwelt upon, of the  white  corpuscles with
nutrition.
  * For further  observations on the  development of the red blood disc,  see the
remarks on the circulation in the embryo of the fowl.
  f Among those who regard the blood corpuscles as cells, may be named Schwann,
Valentin, Addison, Remak, and Barry.  Schwann describes the  blood globule as a
'nucleated  cell," while Valentin considers it  to be a nucleus, and that which is
usually  held to  be a nucleus he regards as a nucleolus.  Remak states, that  he
has witnessed  the development of the globules as parent cells, not within the blood,
but within the cells which line the walls of the  blood vessels  and lymphatics.  The
views of Addison are confined chiefly to  the white globules, which he conceives to
be the fully-developed nuclei of the red blood corpuscles, and which he believes to
be transformed into epithelial cells, &c, &c.  Dr. Barry goes further than this; for
he states that every structure which he has examined arises out of the blood corpus-
cle, "the crystalline lens itself, and even the spermatozoon and the ovum."  The
opinions entertained by Gerber  seem to be of a nature  somewhat similar to the
foregoing.  It is difficult to understand, however, what his exact sentiments are:  they,
at all events, go to the extent of  supposing that all the  solid structures of the body
are derived from preexisting germs, contained in the chyle and blood. 
120                 ORGANIZED  FLUIDS.
day,  it is  frequently invested, that it  is  still able to  claim a few
adherents.
   If we regard with the utmost patience and  attention the beautiful
spectacle of the capillary circulation in any of the more transparent
parts of animals, but especially in the tongue of the frog, we  shall in
vain look for the escape from their containing vessels of even a single
red blood corpuscle, independent of a rupture of those vessels.   In a
normal state,  therefore,  the blood globules are  never free,  but are
always enclosed in  their own proper receptacles.
   A  communication,  however,  between  the  fluid contents of the
blood vessels and the  tissues lying external and  adjacent to them, is
doubtless established, through the operation of the principle of exos-
mosis, whereby a slow exudation  of the fluid fibrin of the blood  is
perpetually going forward.  Now, it is the opinion of most of the
German physiologists, and it is the view best supported by facts, that
this fluid fibrin is to be regarded as the true blastema, out of which
all the different elementary tissues  and structures of the body proceed,
and this not by any power  inherent in  itself, it being,  as respects the
final form which it is made to assume, totally inert and  indifferent,
and which  form  is impressed upon it  by a  vis  insita, or peculiar
power  and  faculty belonging to  each  organ and structure of the
animal fabric.
  While the fibrin circulates in  the blood it retains  its fluid form;
soon after  the cessation of the  circulation, and whether within or
without the system, it passes from the fluid state to the condition of
a solid.  Now, on  the principle  of endosmosis, which has to be so
often  referred to  in the  explanation of numerous phenomena, in the
solidifying power of the  fibrin, and in the vis  insita of the different
tissues,  we recognise the chief and  fundamental causes which regulate
nutrition, growth, and secretion.
  It would thus appear that the globules of the blood (the red globules
are more particularly alluded to) are  not to  be regarded as either
cytoblasts or primary  cells, forming by direct apposition the solids of
the body, and  that  therefore they do not express the  last degree of
elaboration of which the fibrin of the blood is susceptible.
  Again, then, we have to ask ourselves the question, what is the end,
or final condition, of the red blood globules?   Direct  observation  is
wanting to  aid us  in the  solution of  this difficult inquiry,  which,
however, admits of an indirect reply being  given: we  have seen that
no means of egress from the blood vessels is, under ordinary circum- 
THE  BLOOD.
121
stances,  permitted to the red blood  globules, and therefore we are
driven to the  conclusion that, having performed the important func-
tion to which we have already alluded, viz:  that of carriers of oxygen
from the lungs throughout the system, and of carbon from the latter
back again to the lungs, they become dissolved, increasing by their
dissolution the amount of fluid fibrin circulating  in  the blood,  and
which is deemed  to be the true blastema.

                        MOLECULES OF THE BLOOD.
   In addition to the red and the white globules, there exists, as already
mentioned, in  the blood a third description  of solid  constituent, the
"molecules:" these are synonymous with the "basin-shaped" granules
of Vogel,  the "globulines"  of Donne, and the "primary discs" of
Martin Barry.
   The  term  molecule, or granule, is well  suited to designate these
particles;  for either appellation will  serve  to convey  some idea of
their exceeding  minuteness,  and which is computed rarely  to exceed
the  30 ^ oo °f an  inch.  They occur  in great quantities in the  blood,
either scattered singly throughout it or agglomerated into  small  and
irregularly shaped masses.   (See Plate I-fig- 6.)  The molecules are
usually regarded  as the elements out of which the blood  corpuscles
are formed :  on this point, however, direct observations are still want-
ing.  It  is more  probable that the white globules  are developed out
of them  than  the  red,  and this simply by their union or aggregation.*

                    PECULIAR CONCENTRIC CORPUSCLES.
  Besides the red  and the white globules and  the molecules, which
we have described as present in the  blood, a fourth species of solid
corpuscle has  been observed to occur in  its  fibrinous  constituent.
These corpuscles  have been repeatedly encountered by Mr. Gulliverf
in clots  of  fibrin in man and other  mammalia, and are alike to be
found in  them, whether the clots are  formed in the body after death,
or in blood abstracted from the system during life.
  * Since the above few lines were written on the "molecules" of the blood, I have
repeatedly remarked that in blood, on its first abstraction from the system, but few
molecules  were  present, while in that which has been withdrawn from the body
for some time, they have always abounded.  This observation has led me strongly to
suspect that the molecules do not exist in the  blood in a free state, but that wherever
and whenever they are encountered, save only in the chyle, they are to be considered
as derived  from the rupture and destruction of the white corpuscles.
  f See translation of Gerber, p. 31, and Appendix, p. 16. 
122
ORGANIZED  FLUIDS.
   These  corpuscles, of a  very peculiar  structure, as will be seen
hereafter, Mr. Gulliver has described and figured with extreme accu-
racy; and he has styled them "organic germs," "primary or nucleated
cells," and  as  capable of  further development  if placed in circum-
stances favourable to their growth.   Mr.  Gulliver, however,  would
appear to have been quite  undecided as to their real nature, and
whether  they were not to be regarded as identical with the "fibrinous
globules " of Mandl.
   These peculiar bodies I have myself met with  in fibrinous clots
which were found in the heart  after death; and I have no hesitation
in asserting that they differ, in every essential  particular,  from the
fibrinous globules of Mandl, which are  identical with  the colourless
corpuscles of the blood.
   The size  of  these  corpuscles  is subject to the  greatest  possible
variation; they are frequently smaller than the white globules  of the
blood, but very generally  three  or four times larger;  their form  is
also irregular, but inclining, in those I have examined, to the spherical.
They consist of two parts, of nuclei and  envelopes:  the  nucleus  is
of an irregular outline, and  not usually  well  defined without the aid
of reagents; its bulk is about the one-fourth or one-fifth of that of the
entire corpuscle; the envelope, in all the globules which have  fallen
under my observation, has been compound, that is, made up of several
vesicles  concentrically  disposed, the one within  the  other.   (See
Plate IV. fig. 3.)
   The appearance presented by these objects bears a close resem-
blance to the  vesicles  of  certain  species of Algae, of the  genus
Microcystis or Hcematococcus, these being likewise each composed
of several concentrically arranged membranes or vesicles.
   Now, what is the opinion which ought to be entertained in reference
to the nature  of these  corpuscles?   Do   they  really constitute  an
integral portion of our organization? and do they circulate in the
living blood ? or are  they formed in it after death ?   The opinion of
Mr.  Gulliver that they are primary, or nucleated cells, has already
been referred to: my own  impression as to them is,  that they do not
constitute an integral  portion of  our frame;  and that, whether they
exist in the living blood, and circulate in it, or are formed in the clot
subsequent to decease, they are to be regarded as extraneous forma-
tions, probably of an entozoal character.
   It does not appear that the envelopes of all the corpuscles met with
by Mr. Gulliver exhibited concentric  striae, although he  describes 
THE  BLOOD.
123
some of them as  possessing  this  striated  structure:  Mr. Gulliver
speaks also of cells three or four times larger than the corpuscles, and
capable of containing the latter as nuclei.   These I have not  myself
encountered.
  The corpuscles  are not usually scattered equally  throughout the
fibrinous clot, but frequently occur in groups, parts of each clot being
altogether free from the corpuscles.
  Acid reagents, especially the sulphurous acid, will be found useful
in their examination.*

               BLOOD GLOBULES OF REPTILES,  FISHES, AND BIRDS.
  The red globules of the blood of the  reptile, the fish, and the bird,
have all  certain characters in  common with each other, which serve
to distinguish them from those of man and the  mammalia in general.
The  chief  of these  characteristics  are their  form, their  size, the
presence of a nucleus, and, lastly, their  greater consistence.   The
compressed form belongs to the red blood globules of all animals;  in
the  three classes of reptiles, fishes, and  birds, however, although the
globules  possess this flattened  figure, instead of being circular, as  in
man  and the mammalia, they are in outline elliptical;  and, in place  of
having a central depression, this part of each globule is slightly pro-
tuberant.   This  prominence  is  due to the  presence of  a nucleus,
which in the  mammalia we have seen to be absent.
  The size of the red globules is  as distinctive as their form, it usually
exceeding, in reptiles, three or four times that of the majority of the
blood corpuscles of mammalia.   The blood disc of the frog equals in
length the yyVj OI" an inch, while its traverse measurement is  not less
than the reVs  of an inch; now the corpuscle of the elephant, the
largest known among mammalia, reaches only the 2?Vs °f an mc^ m
diameter.f
   It  has already been remarked that most of the animals of the order
Camelida are possessed of  blood globules of -an elliptical  form, con-
stituting  in this respect  an exception  in the  class to which  they
belong.   These  oval corpuscles are,  however, so small, that  they
  * Since writing the above description, I have met with these concentric corpuscles
in connexion with the thymus  gland which had been allowed to remain in water  for
a few hours.
  t The largest blood corpuscles hitherto discovered in the animal kingdom are those
of the Siren and Proteus.  In the Siren, according to Mr. Gulliver, the long diame-
ter of the  blood discs is the 435th, and the short the 800th part of an inch, while
in the Proteus they are stated at about the 350th part of an inch in length. 
124
ORGANIZED  FLUIDS.
could not be readily confounded with the elliptical globules  of  the
frog, &c.; they therefore agree in size, as well as in the absence of a
nucleus, with the blood corpuscles of other  mammalia, although  not
in form.  While  every  possible  care  has  failed in  satisfactorily
demonstrating the presence of a nucleus in the blood of mammalia,
not the slightest difficulty is experienced in detecting it in that of the
frog and  most of the animals belonging to the classes just mentioned,
and  therefore  its  presence is generally  recognised;  although  one
excellent observer, M. Mandl, is of opinion that its formation takes
place subsequently to the removal of the blood  from the system:  this
idea  is doubtless erroneous,  as  we have seen to be  the case with
respect to the  white corpuscles of  the blood, regarding which  M.
Mandl entertained a similar  notion.   In blood corpuscles  immersed
in their own serum, and examined immediately after their abstraction.
the nucleus may be seen with a sufficient degree of clearness to enable
the observer to pronounce with confidence upon its presence.   After
the lapse of a few minutes,  it becomes  much more apparent, so that
its composition is easily  to be discerned: this  arises, most probably,
from the discharge of a portion of the  colouring  matter of each
globule.   The form of  the nucleus is seen to correspond with  that of
the blood corpuscle itself, and to be oval, presenting a granular struc-
ture precisely resembling that of the white globules of the blood, from
one of which it is  only to be  distinguished by  its  much smaller  size
and oval form.   (See Plate  11. fig. 2.)
   Owing to  the firmer  texture and greater size  of the blood globules
of the frog, their  structure  can be well studied,  and  the effects of
reagents  more easily determined.
   In water, the red corpuscles lose their colour, and become circular,
and indeed globular, a change of form which the  nucleus is likewise
seen to undergo.  (See Plate II. figs. 3  and 4.)   These alterations
ensue almost immediately  on the application of the water;  its con-
tinued action produces an effect still more remarkable; the nucleus,
which at first occupied a central position in the globule, is soon seen
to become eccentric, and finally, rupturing the pseudo-membrane of
the corpuscle, escapes into  the surrounding medium; the nucleus  and
the outer portion of each  globule are then  observed as two distinct
structures, lying side by side (see  Plate II. fig. 4);  the latter is at
length absorbed, and then nought remains but the nucleus, which is, as
already remarked,  under  the influence of water  rendered of a globular
form, and which is in no way distinguishable from a white corpuscle 
THE  BLOOD.
125
of the blood, save in the  single particular of size, the nucleus being
several times smaller than the globule.
   Acetic  acid dissolves  (if strong,  almost  immediately)  the outer
tunic,  without  occasioning the prior  extrusion  of the nucleus, the
form of which is not materially affected, the contained granules merely
becoming more clearly defined.   (See Plate II. fig. 5.)
   The white globules  in the blood of the frog  are  very numerous;
they bear no similitude of form or size to the elliptical red blood cor-
puscles, being usually perfectly  spherical, and scarcely more  than a
third of the dimensions of the oval  corpuscles.  Thus, between the
white  globules in  man  and the  mammalia and  those of reptiles, an
opposite relation of size in reference  to the red blood discs exists; for
while, in the former, the white corpuscles are larger  than the red
globules, in the latter they are generally much smaller.   (See Plate I.
fig. 1, Plate W.fig. 1.)
   The plastic property possessed by  the  blood globules of all animals
belongs especially to that of the frog.   The globules, if trailed or drawn
along  the  surface  of a piece of glass, may be  elongated  to thrice
their original length, and made to assume such forms as are  altogether
inconsistent with  the existence  of  a  thin  and  distinct  investing
membrane.*   (See Plate W.fig. 6.)

                         CAPILLARY  CIRCULATION.
   We  have  now considered the  blood, both  physiologically  and
anatomically, out of the system, at rest and  dead.   We have, in the
next place,  to treat of it within the body, living and circulating.
   The  beautiful phenomenon of the  capillary  circulation may  be
witnessed in  the more  transparent parts of  several  animals; as, for
example, in the extremities of young  spiders,  fins  of fishes, in the gills
of the tadpole  and the newt, in  the tail  of  the water  newt, in the
web of the frog's foot, and in the mesentery of the smaller mammalia.
But it is seen to the greatest possible  advantage in  the tongue of the
  * The extraordinary  elongation of which  the blood globules of the frog are
susceptible, may be seen to  very great advantage by adopting the  following little
expedient:—A drop of blood  being placed upon  the object-glass previous to its
coagulation, and allowed to remain there for  a few seconds, until symptoms of con-
solidation have manifested themselves, it is  then to be extended gently with two
pins in  opposite directions;  if now the  microscope be brought to  bear upon it,
elongated corpuscles will be seen in it in vast quantities. In the production of this
change, it is the fibrin which is mainly concerned; for it is through it that the exten-
sion is communicated to the corpuscles. 
126
ORGANIZED  FLUIDS.
frog; an organ peculiarly adapted for the representation of the cir-
culation of the blood, from its extraordinary elasticity and transparence.
For a knowledge of this fact, science is indebted to a neighbour and
friend of mine, Dr. A. Waller, and  by whom  it was communicated
some years ago to M. Donne.  For the exhibition of the circulation
in the tongue of the  frog, in a satisfactory manner, it is  necessary
that the animal should be secured in the following way:—A bandage
having been passed several times  around the body of the frog, so as to
secure effectually the  anterior extremities, it is next to be fastened to
a piece of cork by additional turns of the bandage;  this piece of cork
should be very thin, six or  seven inches  in length, by about ten in
width,  and  perforated  at one  extremity by a square  aperture, the
diameter of which should not be less than two-thirds of an inch.  To
the margin of this aperture, the mouth of the frog, in binding it  to the
piece of cork, should  be brought.   The frog having been thus effect-
ually secured, the soft and  pulp-like  tongue should  be drawn out of
the mouth by means of a'pair of forceps, and  being spread over the
surface of the aperture, should be retained in  position  by from four
to six pins, the elasticity of the tissue of the  tongue  allowing of its
extension  into a thin  and transparent membrane with but little risk
of a rupture of the organ; lastly, the piece of cork should be fastened
to the  stage of  the microscope, in  such a position that the tongue
rests over the opening in the stage.   These preliminary arrangements
being effected, and  a low power of the microscope  being brought to
bear upon it, a spectacle of the highest interest and beauty is revealed
to the sight of the beholder.  We have displayed before us, in action,
almost every tissue of the animal organization,  in its  simplest and
clearest form and disposition—arteries, with their accompanying veins
and  nerves;  muscular  tissue; the  blood, with  its red  and  white
globules; epithelial cells; glands of the smallest possible complication
of structure; and these several  parts are not merely visible, but their
form, disposition, construction, and  normal mode of action, are  all
distinctly apparent; the blood ever flowing, the muscles contracting,
and the glands secreting.
   The circulation in  the tongue of the frog is best seen, in the first
instance, by means of low powers, a larger surface of the organ being
thus brought  under view, and a more exact  idea obtained of the
relative size  and  disposition  of  its numerous  constituents.   The
arteries may be  distinguished from the veins by their  fewer number
smaller  calibre, and  by the fact  that, while  the veins increase in 
THE  BLOOD.
127
diameter, in  the  direction of the  course which the blood contained
in them  pursues, the  arteries decrease  in  the  course which the
current follows in them.   The arteries, from their origin, diminish
in size and multiply in number, by the constant giving off of second-
ary branches; the veins,  on  the  contrary, become enlarged during
their  progress,  and lessen in number,  by the continual addition of
subsidiary veins.   These  differences, as well as the circumstance that
the velocity of the blood  in the arteries is greater than in the veins,
are abundantly sufficient to distinguish the two orders of vessels from
each  other.  If,  now, a somewhat higher  power be  applied to the
objects, we shall be  able to  dive  still further into the  mysteries of
organization; we shall not merely perceive the general motion of the
blood, but also that nearly the entire mass of that fluid consists of red
globules.   We shall  be able to recognise  clearly their  form, and to
see the different  modifications of shape which  they undergo in passing
by each other,  and in escaping any impediment which presents itself
to impede their  progress.  We shall perceive, likewise, that, in the
smaller capillaries, the globules circulate in single series, and mingled
with  them will be noticed  occasionally a colourless globule, which, in
the blood of the  frog, is not  more than half the size of  the elliptical
corpuscle.  (See Plate  V. fig. 2.)   Furthermore, it will be remarked
that the circulation does not  flow on in an uninterrupted stream of
equal velocity, but that certain arrests of its motion occur.  These are
but momentary,  and  after each the current again quickly flows on
with  the same speed  as before'; with each action of the heart,  also, a
slight impulsion of the blood  in the capillaries may be  clearly seen.
   This instructive sight of the capillary circulation  may be viewed
thus for hours, during the whole of which time the blood will be seen
flowing  on with undiminished force.   In certain vessels, however,
after a very long exposure of the tongue  to the  action of the air,
whereby  its moisture  is  continually  abstracted, and  which  acts,
doubtless, as a source  of irritation,  a number of the colourless globules
will  be seen to have  collected in  the capillaries;  these  adhere prin-
cipally  to the sides  of the vessels  and  to  each other,  thus leaving
the channel  still  free for  the  passage of the red  globules, which in
their  course sometimes rush  against the white  globules with such
violence as to detach one  or  more of them from time to  time from its
adhesion  to the walls of the vessel, and which, rolling over once or
twice, joins the  general current of the vessel, and is quickly carried
out of view.  It would   appear  that  any irritation affecting the 
128
ORGANIZED  FLUIDS.
capillary  vessels, even  when applied to them outwardly—as,  for
example, weak chemical solutions—gives rise to the phenomenon in
question.   It is to be observed, however, that at all times considera-
ble numbers of white  corpuscles circulate in the  larger capillaries:
these do not occur mixed up with the  red blood corpuscles; but, as
already remarked, are situated externally between them and the  inner
wall of the capillaries.   (See Plate V-fig- 1.)
   In the plastic power  with which the red corpuscles  are  endowed,
we recognise a beautiful and important organic adaptation  of matter
to the  fulfilment of a special purpose.  Were it not for this plastic
property, and were the red corpuscles of  the blood, on the  contrary,
of a. solid  and  unyielding  texture, it would  follow, as an inevitable
consequence of the solidity of the globules, combined with  their vast
number, that frequent interruption and stoppage of the circulation in
the capillaries would ensue, and which would, of course, result in  the
complete derangement of the functions of the entire economy.
  I come now to record an observation which, so far as I am  informed,
is without parallel.  On one  occasion, in examining the tongue of a
frog, a portion of it broke  away from  the remainder; this I placed
between two plates  of glass, and submitted to examination,  when,
extraordinary to say, it  was perceived that  the circulation was still
vigorously  maintained  in the majority of the  vessels.   Anxious  to
know how long this circulation would be continued, but fully  expecting
to see it cease every moment, myself and  a friend, John Coppin, Esq.,
of Lincoln's Inn, watched it for upwards of an hour, at the end  of
which  time the blood  still flowed onwards  in many of the vessels,
with scarcely abated vigour,  though in others,  often the larger  ones,
the motion  had  altogether ceased.  The mutilated  portion  of the
tongue was  then  placed  in water, in which  it  remained during the
whole of the night; the next  morning it was again examined, when
it was found that a tolerably active circulation still existed in several
of the smaller vessels.  After this observation, the further examination
of the  fragment was abandoned.   The almost immediate  cessation
of the circulation,  which  occurred in some  of the  larger vessels
admits of explanation in the following way:—In  some  vessels the
blood globules were seen escaping from their open  extremities • this
effusion of the globules frequently continued for two or three minutes
until the entire  contents of such vessels became poured out, when of
course the circulation within them ceased, the circulating fluid being
expended;  in other capillaries, the  current  was seen to stop  long 
THE  BLOOD.
129
before their contents had been exhausted, in which case it was usually
to be remarked that some of the blood corpuscles contained in the
vessels had collected around their orifices,  thus producing an impedi-
ment to the further maintenance of the current.
   The foregoing observation is one of much interest and importance;
for it seems  to prove that the  capillary  circulation  is in  a  great
measure independent of  vital influences, and that its persistence is
mainly due to physical agencies.
   With a few observations on  the  mucous  follicles situated on the
upper surface of the tongue of the frog, we shall conclude our relation
of  the  capillary circulation,  as witnessed in that organ.   These
follicles are glands reduced to the simplest  possible amount of organ-
ization: they are  of a  regularly spherical  form,  and transparent
texture; they are situated in the mucous membrane of the tongue, to
the  thickness of which they are entirely confined, as  proved by the
fact that,  when that membrane is dissected off, by means of a needle
the glands are raised along with it.   Into each of these glands may be
seen entering it on one side, and quitting it usually on the opposite, one
of the smallest of the capillary vessels,  in which the blood corpuscles
pass usually in single series; this vessel in its passage through the gland
describes usually a tortuous course;  and within it the blood corpuscles
are seen to be in a state of increased  and incessant activity, appearing
to move, as it were, in a vortex, this appearance resulting from the
curvatures described by the vessel.  (See Plate VII. figs. 1, 2.)
   It might be expected that, in a gland of such simple constitution,
the exact  process of secretion would be rendered apparent; in this
expectation, however, we are doomed to disappointment, no action
beyond that which  we have already related being visible within it.  An
endosmotic action does doubtless take place between the contents of
the gland and those of the vessel which permeates it, whereby a peculiar
product is obtained from the  blood, to  be fashioned and assimilated
by certain powers inherent in  the gland itself, and the precise nature
of which  powers is unknown to us, and it is probable that  it never
will  be revealed.   Pass we now to the description of the circulation
in the embryo of the chick, which possesses points of interest distinct
from those observed in the tongue of the frog.

               CIRCULATION IN  THE EMBRYO' OF THE CHICK.
   The process  by which the circulation in the embryo of the chick
is displayed is one  which requires considerable delicacy of manipu-
                                9 
130
ORGANIZED  FLUIDS.
 lation;  the  care, however, which it  is necessary to bestow upon it,
 for its successful exhibition, is amply repaid by the surpassing beauty
 of the spectacle which presents itself to the beholder.  It is best seen
 in the third, fourth, and fifth days of the incubation of the egg.
   For the purpose of showing it satisfactorily, the egg should be broken
 at the side, and a portion of the shell cautiously removed, without at
 the same time raising with  it the subjacent membrane (membrana
 testce);  this should next be peeled off with the same degree of caution
 as that with which the shell itself was previously raised.
  Immediately beneath  this  membrane, the yolk itself will be seen
 floating in the midst of the colourless albumen, and sustained in posi-
 tion by the beautifully spiral chalaza, which, proceeding from the
 yolk,  are fastened into that portion of the membrana testce which cor-
 responds with the poles of the egg-shell.
  Imbedded in the surface of the yolk of an egg, on the third, fourth,
 and fifth days of its incubation, the embryo will be visible, and issuing
 from  its umbilicus will  be  seen the vessels  which  ramify  in  such
 graceful order through the membrane of the allantois.
  The embryo is almost invariably placed uppermost in the yolk, so
 that it most generally presents itself beneath, whatever part of the shell
 has been broken.  This position results from the lighter specific grav-
 ity, and is, moreover, facilitated by the spiral formation of the chalazae.
  The purposes fulfilled by this position of the embryo  are obvious
 and striking, it being thus so placed as to receive directly the caloric
 which is continually emanating from  the parent hen, and being also
 more  immediately submitted to the influence of the oxygen of the air.
  In an embryo then thus placed in situ, in the third, fourth, and fifth
days of its development, and with the unaided  sight, the rudiments of
 almost all the organs and members may be clearly  recognised, the eye
 and the regular contractions of the  heart, together  with the vessels
departing from it to ramify through the area vasculosa being particu-
larly conspicuous.  With a low power of the microscope, the course
of the blood in the vessels, together with the form and size of the white
 and red corpuscles, may be clearly distinguished.
  The ramifications of the vessels in the area vasculosa present  an
 arborescent distribution;  their entire  course may be traced from their
commencement in the aorta to their termination on the border of the
membrane of the area vasculosa.
  Now, the  great point of interest in the circulation of  the  chick is
that the passage of the blood  may be witnessed throughout.  Thus 
THE  BLOOD.
131
the blood expelled from the heart by the contraction of the ventricle
into the aorta, may be traced through  this vessel, and all its subse-
quent divisions and sub-divisions, until it reaches the ultimate arterial
radicles, passes from these into the corresponding radicles of the veins,
and from  these again into  the  larger venous trunks, by which it is
reconveyed to the heart,  the circle  of the  circulation  being  thereby
completed.
   There are two ways in which the circulation in the embryo of the
fowl may be viewed, either while it is still occupying its natural posi-
tion on the surface  of the  yolk, (and this I think is by far the most
preferable  method,) or the embryo  may be altogether detached from
the yolk by means of an armed  needle, and subsequently placed on a
watch-glass filled with warm water at a temperature of 96°.   During
the operation of detaching the embryo, the egg itself should also be
immersed  in water at the temperature just mentioned.   This latter
process is one, however,  of much nicety, and frequently fails in con-
sequence of the rupture of some of the finer vessels, the blood becom-
ing effused, the different parts of the embryo obscured, and a stoppage
put to the  circulation.
   But it  is not alone the  contemplation  of  the circulation in  the
embryo of the chick which is so interesting and instructive; the study
of the entire development of the ovum, from its commencement to its
termination, reveals facts of the highest importance, and full of wonder.
   The examination  of the blood of the  embryo fowl is especially
instructive, the mode of formation of the red corpuscles admitting of
determination in a manner the most satisfactory.
   In the red corpuscles  contained  in the blood of the embryo in the
first days  of its development, a remarkable variation of size will be
detected, some of them being three or four times  larger than others,
and the smallest consisting almost entirely of a nucleus surrounded by
a faint and delicate  envelope.   Between  the  two  extremes  of size,
every possible gradation is presented.  (See Plate IX. fig. 1.)
  This variation in the dimensions of the corpuscles becomes scarcely
less apparent if they be immersed in water, in  which  they become
perfectly spherical.   (See Plate IX. fig. 2.)
  A diversity of size, almost as remarkable as  that which exists
between the red blood corpuscles of the embryo fowl, will be observed
also in those of the young frog which has but just  emerged from its
tadpole state.   If a drop of the blood of  this young frog be compared
with that  of  a full-grown frog, the  corpuscles in the former will be 
132
ORGANIZED  FLUIDS.
remarked to vary greatly in dimensions, while in the latter they will
be seen to present a much greater uniformity of size.   (See Plate IX.
figs. 4, 5.)
  Now, the inferences to be deduced from this great diversity of size
are palpable, and are, first, that the red blood corpuscle is at its origin
small, and only attains its full dimensions after a given period; and,
second, that the nucleus is  the part of the corpuscle which is  first
formed, the coloured investing and perfectly smooth portion of it being
gradually developed around this  subsequently.   This view is incon-
sistent with the notion entertained by many, that the red blood cor-
puscles result  from the gradual assumption by the white globules of
the characteristic  distinctions of the red blood discs; for were  this
really the case, we should be at  a complete loss  to account for the
remarkable differences of size to which we have adverted.
  A similar mode of development to that which has been described as
belonging to the red blood corpuscles of the embryo fowl, appertains
also, I believe, to that of all  the Oviparous Vertebrata.
  The development of the coloured blood  corpuscle of the Mammalia,
I conceive to agree also with that of the other Vertebrata in the  fact
of its being small at first, and subsequently and gradually attaining its
normal proportions, but to differ  from that  of  the  Oviparous Verte-
brata in not being developed around a central nucleus.

                    DISSOLUTION OF BLOOD CORPUSCLES.
  But if the blood of the embryo  fowl is well adapted for the study of
the origin and development  of red blood corpuscles, that of the adult
fowl is no less fitted for ascertaining their end and final destination.
  Some observers have entertained the idea, already expressed in this
work, that the older blood discs become  melted  down in the liquor
sanguinis, and thus, by their dissolution, increasing the amount of
fibrin held dissolved in that liquid.   To the  adoption of this notion
they were driven, because  they  were unable to dispose  of the red
blood disc in any other way, and which other facts had made apparent
to them could not be regarded as persistent structures.
  In proof of  the  accuracy of this statement respecting the melting
down of the corpuscles, they had  not, however, a particle of direct
evidence to adduce.  I will  now  proceed  to show that the view refer-
red to may be substantiated by positive observation.
   In almost every drop of the  blood  of  an  adult fowl,  a number of
certain pale and usually colourless corpuscles will be seen, having a 
THE  BLOOD.
133
nucleus of the same size and  structure as that of the ordinary red
blood disc distinctly visible in the midst, the investing portion of each
corpuscle at the same time being invariably smooth and destitute of
granules.
   These  corpuscles vary in size, in form, and in colour; the larger
ones, which are equal in dimensions to the fully-developed blood discs,
usually retain a faint colouration, and are invariably of an oval form;
while the  smaller ones, many of which consist  of merely a nucleus
and a closely-fitting  envelope, are perfectly  colourless, and for the
most part, although not always, spherical.  (See Plate IX. fig. 3.)
   Now, there is  no difficulty whatever in detecting these pale and
mostly spherical  corpuscles with a good instrument, nor is there the
slightest danger of confounding them with the white corpuscles, which
are also to be seen retaining their uniformly molecular aspect.
   The corpuscles just described exist not merely in the blood of the
adult fowl, but they may be detected, with similar facility, in every
Oviparous Vertebrate animal the blood of which I have  examined;
and they  abound in  the blood of  tritons and frogs.  (Plate IX. fig. 5.)
   But further, there  may be detected in the blood of adult Oviparous
Vertebrata, not merely the delicate and pale corpuscles referred to,
but also numbers of naked  nuclei—that is, of nuclei deprived of all
trace of investing membrane.   (See Plate  IX. figs. 3 and 5.)
   These  nuclei should, however, be examined with care, and a nice
adjustment of the object-glass; for it will be found, on close  examin-
ation, that many of them, though appearing at first sight to be naked,
are not really  so,  but are invested by a scarcely-perceptible envelope.
   Now, these large and slightly-coloured oval corpuscles, the smaller
perfectly colourless and mostly spherical ones, and the  naked nuclei,
represent  progressive states of the dissolution of the red blood disc.
   When  first  I noticed these pale  corpuscles and nuclei, I  was dis-
posed to think that they represented  stages in the upward  develop-
ment of the red blood disc: this opinion was, however, dispelled, by
observing  that the  pale  and colourless  corpuscles  often exceeded
greatly in size the smaller true and coloured blood corpuscles.
   There is one circumstance  connected with these  pale  corpuscles
which does not appear to  admit of any  very satisfactory explanation,
viz : their occurrence on the field of the microscope in groups.
   A word or  two as  to  the  seat  or  locality in which the  work of
development of blood corpuscles, and subsequent dissolution  of them,
is  conducted.   Physiologists appear always to have been on the look- 
134
ORGANIZED  FLUIDS.
out for some organ of the body, the  especial purpose of which in the
animal economy they conceived should be the elaboration of the blood
corpuscles;  and some of them, as Hewson and Donne, not knowing
well what office ought to be assigned to that  much-discussed organ,
the spleen, have on various grounds  considered it to be the laboratory
in which the work of development is carried on.   Of the dissolution
of the red blood discs, no definite or decided observations hitherto
appear to have been made by any observer.
   Observation has convinced me that the  development of blood cor-
puscles is not assigned to any particular organ  of the body, but that it
occurs within the blood-vessels during the whole course of the circu-
lation  and of life.   During the  first  formation of  the  blood in early
embryonic life, the  corpuscles  are  said to be  formed in the cells,
which by their union  with each other give  origin to the capillary
vessels.
   Further, it is probable  that,  while it is  in  arterial blood that the
work of  development of blood  corpuscles is most  active, it is in the
venous fluid that the converse work of dissolution is mainly effected.
   The development of blood corpuscles is also  most  active in very
early life, when growth is rapid;  and it is likewise more active than
ordinary  in adult existence, after haemorrhages, and in  persons of the
plethoric  diathesis.   In like manner it may be  presumed  that the dis-
solution of red blood corpuscles  proceeds  more quickly in anaemic
conditions of the  system, and in old age, while at  the  same time, at
the latter period, development of new corpuscles is more  tardy.
   It  is now hoped  that a more satisfactory explanation of the origin
and end of the red blood disc has been given than it was feared, when
the writer first approached the consideration of these difficult, though
most  important, questions, it would have been in  his  power to have
afforded.
                     VENOUS AND ARTERIAL BLOOD.
   Venous and arterial blood differ in certain important respects from
each other;  arterial blood is of a brighter colour,  and coagulates more
firmly than that which  is venous.  The difference  in colour is due to
the presence in the former of oxygen, and in the  latter  of carbon in a
state of combination not yet well determined.    Venous blood, when
exposed to the action of oxygen, soon acquires  the vivid red colour of
arterial blood, and this, when submitted to the  influence  of carbonic
acid, as speedily assumes the dark hue of venous blood.
   The greater or less firmness  in the  clot formed is owing to  the 
THE BLOOD.
135
different amount of fibrin  contained in the two fluids, and which is
greatest in that which is arterial; the coagulum of which, therefore,
possesses  the greatest  density.   The  differences detected by the
microscope in  the  blood corpuscles of arterial and venous blood are
scarcely appreciable.   Gerber states that the " tint of colour exhibited
is various; bright in the globule of arterial blood, dark red and some-
what streaky in that of venous blood:" this difference of colour, which
doubtless exists, it is easier to infer than positively to  demonstrate by
means of the microscope.   While arterial blood is  richer in  salts,
venous blood contains a greater proportion of fatty matter.
  There are several substances which  effect a change in the colour
of the  blood: thus, oxygen, the  concentrated solutions of salts with an
alkaline base, and sugar, turn dark venous of a bright  florid or arterial
red; this reddening being accomplished by the salts and sugar,  even
when the blood is placed in a vacuum, or an atmosphere of hydrogen,
nitrogen, or carbonic acid gasses.
  Newbigging* hath also  remarked that  venous blood takes the tint
of vermilion  in a cup, at those situations at which it is painted with
the green oxide of chrome; and Taylorf  has  confirmed the observa-
tion that the  colours which contain the oxide of chrome brighten the
tint of blood.
  On  the other  hand, bright or arterial  blood is darkened, or  even
blackened, by  contact  with carbonic  and oxalic acids,  and by its
admixture, according to Henle, with distilled water.
  Sulphuric  acid, and  other acids which are agitated with the blood,
change its colour from red to blackish brown.
  The nitrous and  nitric oxides cause vermilion blood to  take a deep
purple tint.J
  The power possessed by those substances which brighten the colour
of dark  venous blood,  is supposed  to  be derived from the oxygen
which  they contain, and by means of which a chemical transforma-
tion in the condition of the red element of the blood,  the hematine, is
effected, a portion of oxygen being absorbed during the change of
colour.  Those substances, however, which cause arterial blood to
assume the tint of venous blood, are presumed to exert their influence
by means of the carbon of which they are compounded, and a portion
of which becomes imbibed during the work of transmutation.
           *  Edinburgh New Philosophical Journal, October, 1839.
           f Lancet, February, 1840.
           I  Henle, Anatomic Generate, tome premier, page 471. 
136
ORGANIZED  FLUIDS.
  Henle,  nevertheless,  considers that these several alterations of
colour arise rather from  mechanical than chemical causes, and that
they depend upon the state  of aggregation  of  the particles  of  the
colouring  matter, these being differently  disposed  according  to  the
nature of the reagent employed.
  Thus, Henle remarks*, " It is evident that the colour of the blood
is brightened under the influence of substances which oppose the dis-
solution of the hematine in the serum, and maintain or reestablish  the
flat form of  the corpuscles, as the concentrated solutions of salts and
of sugar;  while pure water, which dissolves the colouring matter, and
causes the corpuscles to swell, deepens the colour of the blood."
  Hamburgerf,  according to Henle, has even  observed that weak
solutions of  the chlorides render the colour of the blood deeper, while
their concentrated solutions make it pass to vermilion.
  Again, according  to the observations of Schultz, it would  appear
that the red blood corpuscles are flattened by the  action of oxygen,
while the  effect of the application of carbonic acid is to cause them
to swell up,  and assume a more or less globular figure.
  On this fact, Henle reasons thus:  Accompanying these changes of
form there are alterations in  the state of aggregation of the colouring
matter of the corpuscles;  thus, in oxygen, or in any saline solutions,
the plasma  remains  clear and  colourless, the blood discs being flat-
tened, and the colouring  matter contained within  them condensed;
while in carbonic acid or water the plasma becomes coloured,  by  the
escape of a  portion of the hematine from the corpuscles,  which swell
up, and assume a form approaching more or less the globular.
  Now, the difference in colour between  venous and arterial blood
Henle maintains may be accounted for by reference to  the form of
the corpuscles, and the consequent condition of the  particles of  the
colouring matter.
  And it is  also by reference to the  state of the colouring matter that
Henle accounts for the fact that blood which has  once acquired a very
dark  colour is thereby rendered incapable of reassuming the bright
hue of arterial blood on the application of oxygen or saline solutions,
because, he  says, that the pigment which had escaped into the plasma,
under the influence of the carbonic  acid, cannot be made to enter
into the corpuscles again, when by means of oxygen they are again
flattened.
        *Loc. cit. page 471.
        f Hamburger, Exp. circa Sanguinis Coagulationem, pp. 32. 42. 
THE  BLOOD.
137
  The colour of the blood, then, according to Henle, depends upon
the single fact of the form of the corpuscle, and that this colour is so
much the more bright as these are flat.
  Finally, in support of his theory, Henle refers to changes of colour
presented by certain inorganic substances  from an  alteration in the
state of aggregation of its constituent particles: thus, it is well known
that the ioduret of mercury recently sublimed is yellow; in cooling,
its colour passes to scarlet, and pressure determines this change in an
instantaneous manner.
  Such is Henle's mechanical theory of  the changes of colour expe-
rienced by the blood on the addition of reagents;  a  theory which,
however ingenious it may be, I deem to be insufficient to account for
the very remarkable alterations  of colour to which  the vital fluid is
subject.
   The changes of colour of dark blood to a vermilion hue, and of this
again to the  deep tint of venous blood, admit of a chemical  explana-
tion being given, the essential element  of the former change being
oxygen gas, and of the latter carbonic acid gas.  Thus, even  the
remarkable effect of the application of the chlorides may be accounted
for by reference to the well-known operation of chlorine as a bleach-
ing agent, viz:  through the power  which it  possesses of depriving
water of its  hydrogen, and  altering the  state  of combination of  the
oxygen.
   With respect to the observations of Schultz on the effect of carbonic
acid and of oxygen  in altering the form of the red blood corpuscles,
and on which fact the entire of Henle's theory rests, I would observe
that, in conjunction with Mr. Miller, the gentleman who manifests so
much of patience, skill, and  intelligence in the execution of the draw-
ings of this work, and who  is moreover an excellent chemist, I have
made many  experiments, with the  view of ascertaining the power
possessed by the former reagent in modifying the form of the elliptical
corpuscles of the blood of  the frog, the blood being in  some cases
submitted to the direct action of the gas, and in others the  animal
itself being subjected to  its influence.
   The result of these experiments, on my mind, is the conviction that
the effect of this gas on the  figure  of the corpuscle is not appreciable.
I am, therefore, disposed to  allow but little weight to the mechanical
theory of the changes of colour experienced by the blood.
   Venous blood does not present precisely the same tint of colour, or
the same characters in all parts of the system: thus, the blood found 
138
ORGANIZED  FLUIDS.
in the vena  portae is deeper in colour than any other venous blood,
and, according to Schultz, it does not redden either on the application
of oxygen gas or of salts, and does not coagulate, or gives but a divided
clot; it is richer in water, in cruor, and in fat, and  poorer in albumen,
than ordinary venous blood.
   It would be a point of much interest to determine whether arterial
or venous blood  contains the greatest number  of blood  corpuscles.
The experiments which have hitherto been made, with the view of
determining  this question,  are most unsatisfactory, and contradict
each other.

MODIFICATIONS OF THE BLOOD CORPUSCLES THE RESULTS OF DIFFERENT EXTERNAL AGENCIES.
  Peculiar Modification of the Effect of commencing Desiccation.

  If the  red corpuscles  be  examined  a few  minutes  after their
abstraction from the system, in a drop of blood which has been spread
out between  two plates of thin glass, it will be seen that many of
them, and especially those which are situated near the margin of the
drop, present an  appearance very different from that which  belongs
to them in their ordinary and natural condition.   They now no longer
exhibit the flattened form with the central depression, but have become
converted into little spheres,  the surface of which, instead of being
smooth, is now rough and tuberculated.   (See Plate I. fig. 5.)   Blood
corpuscles thus changed have been compared to mulberries in  appear-
ance.  This  alteration is  supposed  by Donne to depend  upon com-
mencing desiccation, and  to  arise from deficiency of  serum,  the
mulberry-like globules being but imperfectly bathed in that  liquid.
No very satisfactory explanation of the exact nature of the  change
has as yet been given.   MM. Andral and Gavarret* suppose that the
mammillated  appearance of the corpuscles arises from the adherence,
to the surface of the globules, of a number of the exceedingly minute
molecules of  the  fibrin; this explanation is probably more ingenious
than correct. If a number of the  altered globules be carefully and
closely examined, it will be remarked that they  do not all exhibit
precisely similar  appearances; that  in  some globules, for  instance, it
will be observed  that the  contour is but slightly broken or indented;
that in others the indentations of the surface are more considerable,
and the small spaces between them consequently more  prominent;
and  again, in other globules, and which  are  indeed by far the most
          * Essai d'Hemalogie Pathologique, par G. Andral, page 23. 
THE  BLOOD.
130
 numerous, it will be obvious that the whole surface has become dis-
 tinctly tuberculated, each tubercle, of which there are several to each
 globule, appearing to be of a spherical form, and resembling a minute
 bubble of some  gas, probably of oxygen, or carbon, according  as the
 blood is arterial  or venous.   That they are really of a gaseous nature
 is proved, I think, by the  fact of their  gradual  formation  as well as
 dissipation.  M. Andral states, that in blood which has been deprived
 of its fibrin, the corpuscles never exhibit the peculiar  granulated or
 tuberculated aspect which we have described; and this fact he adduces
 in support of the opinion  entertained by him, that this  peculiar con-
 dition of the  globules is due to  the accumulation on their surface of
 the molecules derived from the fibrin.
   Mr. John Quekett is also of the opinion that this peculiar condition
 of the blood globules of which we have been speaking,  is occasioned
 by the adherence to their edges  of granules which he considers to be
 derived from the interior of the corpuscles themselves.  See "Observ-
 ations on the Blood Discs and their Contents," Microscopic Journal,
 vol. i. p. 65.   For further observations on this granulated appearance
 of the corpuscles, see Part I. p. 31.

 MODIFICATIONS THE RESULTS OF DECOMPOSITION OCCURRING IN BLOOD ABANDONED TO ITSELF
                         • WITHOUT THE BODY.
   In blood abandoned to itself, and exposed to atmospheric influences,
 changes of form  and appearance speedily begin to manifest themselves
 in the red corpuscles.  These changes occur in regular order; they
 first become wrinkled, deformed, and tuberculated; they  next lose
 their flattened and disc-like  shape, becoming globular  and  smooth;
 their colouring  matter escapes  from  them, and they present a livid
 hue.   In this condition they are with difficulty discoverable in the
 blood;  finally, they dissolve, and  all traces of them disappear. These
 successive changes are all produced in the course of a very few hours:
 the exact period, however, varies with the temperature of the atmos-
 phere and actual condition of the blood when extracted from the system.

 MODIFICATIONS THE  RESULTS OF  DECOMPOSITION  OCCURRING IN BLOOD  WITHIN  THE
                         BODY AFTER DEATH.
  The  changes  which we  have described as  occurring in  blood
abandoned to itself without the system, take place likewise in  the red
corpuscle of that which is contained within the body after death, and
this even with a greater degree of quickness than in the  former  case; 
140
ORGANIZED FLUIDS.
the time, however, bears a relation  to  atmospheric conditions,  to
temperature,  as  well  as, especially, to the nature of the  malady  to
which the patient has succumbed.   If the affection which has occa-
sioned death  be of a nature to exhaust  profoundly the vital powers
—if it be a chronic disease of  long duration, as a typhoid  fever—the
period requisite  for the production of these  changes will be very
short; so  brief, indeed, that the alterations may be  detected  in the
corpuscles almost immediately after the  extinction of life.  It is of
much importance that the changes resulting from decomposition, and
which occur  in the dead body, should not be confounded with  real
and pathological alterations of the red corpuscles.

                       CAUSES  OF INFLAMMATION.
                        Exciting Cause.

  The fact which has been alluded to in the preceding pages, of the
accumulation of the white and  red corpuscles in the tongue and web of
the frog, as a  consequence of the application of irritation, bears a close
relation to the phenomena of inflammation, and shows that the exciting
cause of  inflammation, whatever it may be—such as a blow, exposure
to cold, burns,  scalds, or the  application of  irritating substances—
acts usually through the medium of the nervous system, the  impression
produced  on  it impinging upon the structures to which the ultimate
nervous fibrillae are distributed, viz: the vessels in the which a series of
results ensue which together constitute the condition of inflammation.

                        Proximate Cause.
  When the white and the red  corpuscles of the blood accumulate
in the capillaries of a part in  normal  quantity, those vessels may be
considered to be in a state of " vital turgescence;" when, however, they
are present in those vessels in  abnormal proportion, then the capilla-
ries may  be said to be in a state of "inflammatory turgescence."
  Now, the term "congestion" indicates a condition of  the vessels
intermediate between  vital and inflammatory turgescence,  and which
may be denominated "congestive turgescence."
  In vital turgescence, a phrase which indicates the condition  of the
vessels in a  state of normal  nutrition,  the  capillaries are slightly
increased in calibre, and are pervaded by an unusual, though perfectly
normal number  of  corpuscles, both red and white, but  especially  of
the latter, some of which adhere to the walls of the vessels. 
                          THE BLOOD.                       j^j

  In  congestive  turgescence,  or  in congestion, the calibre  of  the
capillaries  is more considerably increased in size, and a greater and
abnormal number of white and red corpuscles, especially the former,
are collected in the vessels.  These corpuscles, if the turgescence ter-
minates in resolution without advancing to the condition of inflamma-
tion, do not undergo any structural changes, but enter again into the
circulation, their  removal being determined by the discontinuance of
the exciting cause, and by the vis a tergo  of the circulation, which
drives the corpuscles onward.
  Lastly, in inflammatory turgescence, the diameter is very  con-
siderably enlarged, and their  interior is  filled  with a very greatly
increased and abnormal quantity of white  and  red corpuscles, these
accumulating to  such an  extent  as either to  seriously obstruct, or
altogether  destroy, the circulation in those vessels.   This condition
of the vessels is always accompanied by certain structural alterations,
which effect not merely the corpuscles themselves, but also the vessels
and parts adjacent to them; these alterations being merely attributable
to the impediment presented  to the onward progress of the blood in
the capillaries by the accumulation in them of  the blood  corpuscles.
  We now know that the proximate cause of inflammation consists
in an abnormal accumulation of the corpuscles of the blood  in  the
minute capillary  vessels, and which accumulation we  perceive must
inevitably impede the function of the part  in which the vessels  are
thus surcharged,  alter its structure, and finally tend to a sympathetic
disturbance of the  entire economy.   For this  discovery we  are
indebted to the microscope.   It will thus  be seen that some of the
ancient hypotheses in reference to the proximate cause of inflammation
were  not so very far wrong, and that most of them recognise  the
fact, that it is the capillary vessels and blood  corpuscles which are
mainly concerned in the production of the phenomena of inflammation.
  Finally, inflammation may, like congestion, terminate in resolution;
but, unlike  congestion, it always leaves  permanent  traces  of its
visitation, the resolution being but  incomplete.   It may terminate,
also, in "hepatization," or  in "purulent  infiltration."   The fibrin of
the  blood is the  chief agent in producing  the  consolidation  of the
structure known by the term  hepatization, while it is the white cor-
puscles analogous to those  of the blood, as will be seen  hereafter, that
give rise to  the purulent formation. 
142
ORGANIZED FLUIDS.
                      PATHOLOGY OF THE BLOOD.
   We now come to the consideration of the most important division
of our Chapter upon  the Blood, viz: that which treats of the patho-
logical changes which that fluid  undergoes,  and  a full and clear
understanding  of which  is so  necessary  to the safe and successful
treatment of disease.
   These  pathological alterations are  numerous,  and  engage not
merely the solid constituents of the blood, the white and red corpus-
cles, but also  its fluid elements, the fibrin  and  the  albumen; the
abnormal conditions of each of which principles of the blood we shall
find to be accompanied  by a  distinct  train of morbid, phenomena.
It may be said  that the fibrin  and the  albumen being entirely of a
fluid  nature, and  not holding  solid particles of any  magnitude in
suspension, they ought  not to be considered in a work devoted to
microscopic anatomy.  We shall find, however, that  these  several
constituents of the blood  are so intimately associated, that, in order
to understand  any one of them fully, it is necessary that we should
possess a knowledge of the others also, and therefore I consider that
their discussion comes within the legitimate scope of this work.
  For much of our knowledge of  the pathology of the blood we are
indebted  to the united researches  of MM. Andral  and  Gavarret, to
whose valuable essay we shall have occasion hereinafter to make
frequent reference.

          Pathology  of the Red Corpuscles of the Blood.
  The scale of the red corpuscles of the blood, relative to that of the
other elements, varies considerably, even in states of health.  The
mean proportion of red corpuscles is estimated by MM. Andral and
Gavarret at 127 in every  thousand parts of the  vital fluid.  This
scale  may, however, be elevated to 140, or  depressed  to  110; the
variations in the quantity of the red globules within these limits being
compatible, however, with a physiological or healthy condition of the
blood, although the higher  scale,  140, is allied to a state of plethora,
while the lower, 110, borders upon the opposite state, of anaemia, and
both of which  may be regarded, if not as diseases in themselves, at
least as powerful, auxiliary, and predisposing causes of  many morbid
conditions of the system. 
THE  BLOOD.
143
     Increase in the Number of the Red Corpuscles.—Plethora.
   An increase in the number of the red corpuscles of the blood exists
in that condition of the system which has been  denominated  the
plethoric,  and which  increase  constitutes  its chief element.   The
authors already cited found the mean  proportion of the red globules
in the thirty-one cases in which the blood was submitted to examin-
ation, to be in every thousand parts 141; the minimum 131,  and the
maximum  154.  With this  increase in the  number of the red cor-
puscles, it was not found that  any other  element of the blood had
become either augmented or diminished.
   The  symptoms which  indicate the  existence of plethora, whether
they be organic, or  functional and mental, all  admit of a ready and
satisfactory explanation  by a reference to the increased quantity of
the red corpuscles.
   The  existence of a  state of plethora  implies high vital powers;
there seems to be in the plethoric, as it  were a super-abundance of
life, and which is imparted to all the parts and organs of the system
alike.   The  plethoric  diathesis would appear to be more frequently
hereditary than acquired, and no degree of high and  nutritious feeding
will induce  it in the system of some persons, although an opposite or
anaemic state may be produced in all by the abstraction of a proper
quantity of suitable nourishment.
   The general symptoms which  characterize the plethoric diathesis,
are a well-developed muscular  system, voluminous thorax, a  deep-
coloured  skin,  and  a ruddy  complexion;  coinciding  with  these
physical and outward appearances, we find much functional activity
to exist, the respiration is free and unembarrassed, the digestion  quick
and active, the pulse is full and  strong, and the motions of the body
are performed with  celerity and power.   This functional  activity
appertains  also  to  the operations  and emotions of the mind;  the
plethoric is quick in thought, hasty and violent  in temper.
   The injected skin, the brilliant complexion, are to be explained by
reference to the increased quantity of the red corpuscles which cir-
culate in the blood, and which alone are the seat of colour, while the
great organic development  and the functional  and mental activity
depend  partially upon  the greater amount of oxygen  of which the
blood corpuscles are the carriers to all  parts of the system, and which
is so essential to the vigorous performance of the vital processes and
manifestations. 
144                 ORGANIZED  FLUIDS.

   The characters exhibited by blood which has been withdrawn from
the system are likewise consistently explained by reference to  the
augmented quantity of the red  blood  corpuscles; thus the blood in
plethora, immediately on its abstraction, is observed to be of a deeper
colour, and the clot formed subsequently by its coagulation of a larger
size; this, although voluminous, is of mean density, and never exhibits
the buffy coat, which  circumstances are accounted  for by the fact
that, as already remarked, in the blood of plethoric persons there
exists necessarily no excess of fibrin.
   Accompanying the plethoric  condition, and dependent upon it, we
have frequently a number of grave pathological manifestations, apo-
plexies, haemorrhages, congestions, vertigos, noises in the  ears, and
flashes of light before the eyes; all of which are most generally greatly
relieved by venesection, which withdraws from the system a portion
of the super-abundant red blood  corpuscles.

    Decrease in the Number of the Red Corpuscles.—Ancemia.

   The term anaemia indicates a  state of  the system the  very reverse
of that which obtains in plethora:  in  it the  red blood corpuscles,
instead of being in excess, are greatly below the physiological stand-
ard.   The authors  quoted found, in sixteen cases of  commencing
anaemia, the mean of the red globular element of the blood to be 109;
and in twenty-four examples of confirmed anaemia, 65; that is, almost
one-half less than the standard which belongs to health.  In one case
of anaemia in the human subject, M. Andral found  the  scale to
descend so low as 28; a depression which one would scarcely suppose
to be compatible with life.
   In spontaneous  anaemia it  is stated, that  it is  the  globules alone
which  are affected, and that  in it, as in plethora, the  other elements
of the blood undergo neither  augmentation nor diminution; in acci-
dental  anaemia,  however, resulting  from direct  losses  of the vital
fluid, the normal standard is of course disturbed; for in haemorrhages,
and especially in first bleedings, it is chiefly the globules which escape,
and this would lead to the relatively higher scale for the  fibrin.
   As anaemia depends upon a condition of the blood the very opposite
of that which exists in plethora,  the symptoms also in  these two
constitutional conditions are  the reverse of each other; instead of
the vascular and injected skin, we find it  to be livid and exsanguine,
these  appearances extending also to  the  mucous membranes; in 
THE  BLOOD.
145
place of the accelerated functions, we notice that  the vital actions
are sluggishly performed, and that the mental powers are feeble.
  The blood  abstracted from the system exhibits a  paler tint than is
usual, and the clot  is  small, and floats in the midst of the serum,
which is  very abundant;  small, however, as the crassamentum is,
it  is yet  of  considerable  density, as might  be expected from the
remark which has already been made, viz: that the fibrin exists in its
normal  proportion,  and therefore is in  excess  over the  globular
element  of the blood which is deficient;  it is  for  the same reason
also that we frequently  notice upon the surface of the clot the buffy
coat; the density of the clot, and of the crust which covers it, are so
much the more marked as  the anaemia is considerable.
   The existence of the miscalled inflammatory crust  in anaemic states
has long been known, although not satisfactorily accounted for.
   The  pathological disorders  to which  anaemia gives origin are
numerous: the general  debility, the disordered digestion, the difficult
respiration,  the palpitations of  the  heart,  the  faintings,  are  well
remembered.
   There  is a state  of  the system, well described by Andral, which
stimulates plethora,  but which  is really  allied  to  anaemia, and to
which the term false plethora might be given; in  this  we have the
injected  skin  and many other indications  of plethora;  it is to  be
diagonosed,  however, by means  of the  constitutional disturbances
which coincide with those  of ordinary anaemia.
  It is in anaemic conditions of the system  that we detect the remark-
able bruit de soufflet, in reference to which Andral in his essay on
the blood has instituted some useful researches, the chief result of
which is the establishment of the fact, that the intensity and persistence
of the bruit is in exact proportion to the severity of the anaemia.
  In pregnancy we have a slight  example of an anaemic  condition of
the blood, and in  chlorosis we see anaemia to prevail with various
degrees of severity.   In phthisis  the scale of the red corpuscles is
likewise  much reduced, but not to the extent to which its  reduction
is witnessed in chlorosis; and this is  the  more  remarkable from the
circumstance  that in the former  disease it is those organs which are
affected, between which and the red  corpuscles  a  close connexion
exists.    In  cancer  also the number  of  the  blood  corpuscles is
reduced:  in  phthisis the  diminution  precedes  and  accompanies
the whole course of the affection, while in cancer it occurs only at
an  advanced  period of the disease, and arises  principally from the
                             10 
146
ORGANIZED  FLUIDS.
continual  losses of blood to which cancerous patients are so subject.
In disordered states of the system, purely nervous, we  find also  the
red element of the blood to be deficient.  The scale of the red globules
in a number of cases in which the blood of phthisical patients was
submitted to  examination oscillated between 80 and 100.

Increase in the  Number of the Red  Corpuscles under the Influence
          of  Recovery and of certain Medicinal Agents.
  Under the influence of recovery the red blood corpuscles increase
in number, and have a tendency to attain  to  their  physiological
standard, which, when reached, they may even exceed, until  at length
they mount  up to  the scale which denotes the  existence  of  the
plethoric condition.
  Certain  medicinal substances exhibit likewise much influence in
increasing  the number of the red  corpuscles; of  these  the most
remarkable is iron, under the effect of which remedy the pale com-
plexion of the chlorotic will be seen gradually to acquire the  tone and
colour indicative of health  and strength.

          Effect of Disease upon the White Corpuscles.
  The white corpuscles of the blood have not hitherto received that
amount of attention  which has been bestowed by so many observers
upon their associates the red  corpuscles; indeed, it is only in these
latter times  that  their investigation has been  pursued with that
degree of care which, from their importance, they so well merit, and
observations are still wanting upon their condition in states of disease.
It has  already been  remarked that an increase in their  number  has
been frequently observed to occur in various diseases, and especially
in such  as  are accompanied by suppuration  and great exhaustion of
the  vital powers.   Of the precise cause of this  increase, no'very
satisfactory explanation has been offered, and the  following attempt
at an explanation is presented to the consideration of the reader with
much hesitation.  In most serious disorders, the function of nutrition
and assimilation is more or less impeded.   Now, supposing that these
white corpuscles are essentially connected  with  nutrition,  and that
while the  cause which determines  their  formation still  continues
in operation, that which  regulates their assimilation  is suspended,
there would result, as an inevitable consequence, an accumulation of
the white corpuscles in the blood. 
THE  BLOOD.
147
Deficiency of Fibrin in Fevers, as in  Typhus, Small-pox, Scarlatina.
                            Measles.

  The important researches of MM. Andral  and Gavarret establish
the fact, that, in that  much-debated  class of maladies, fevers, there
is a deficiency in the blood of its spontaneously coagulable element,
the fibrin.  In the Essai d'Hematologie no scale of the diminution in
the amount of fibrin is given;  it is  shown, however, that  in some
fevers, and especially in the  commencement, the deficiency of fibrin
may be but small; and that in others, particularly when symptoms of
putridity  have  manifested  themselves, and  which  may ultimately
complicate all fevers, the loss  of fibrin is considerable,  and  further
that the intensity of symptoms is in direct relation to this loss, being
great when the diminution of fibrin is also great.
   It is  not to be understood, however, that the deficiency of fibrin
constitutes the  essence or real and specific cause of fever;  for this
we must look to some  other agent or fact, probably to the contami-
nation of the  general mass of the blood  by  the  imbibition  of some
deleterious and subtle miasma.   That  the deficiency  in  the amount
of fibrin is not the cause of fevers, we find to be  proved  by the facts
that this class of maladies attacks persons of every possible variety
of habit and  constitution, and in many of whom, at the onset  of the
disorder, no deficiency of fibrin can be detected; and the same view
is likewise confirmed by the circumstance which must have attracted
the attention of every physician, viz:  that the primary condition  and
inherent powers of the system determine and control  but to a com-
paratively slight extent  the course which  the malady may take, and
which course seems  to be dependent upon  the nature and quality of
the infecting  agent itself.   The inference,  then, which may be derived
from the fact that a deficiency of fibrin exists in the blood of persons
afflicted with fever, is, that the tendency of the cause  of fever, a
miasma, or whatever else  it may be, is to occasion a depreciation of
the physiological standard of the fibrin in the blood, and not  that the
deficiency is in itself the exciting cause of fever.
  Between this diminution in the normal proportion of the fibrin and
the various hemorrhages, which are so often  observed to complicate
fevers of all kinds, a corelation doubtless exists, although the  precise
manner in which this deficiency leads to such a frequent recurrence
of hemorrhage is not clearly understood, and the only way in which 
148                 ORGANIZED FLUIDS.

this can be explained is by the supposition that in fevers from the
cause assigned, viz: the small quantity of fibrin, the solids generally,
and the blood-vessels in particular, lose a portion of their solidity, and
readily give way to the force of the fluid contained within them.
  The hemorrhages referred to are frequently observed in  small-pox,
in which the blood is effused into the pustules;  in scarlatina, in which
fluxes take place from various parts of the  body; and in  typhus, in
which we have frequent buccal hemorrhages, and the formation of
petechiae.
  Cotemporaneous with this diminution in the amount of fibrin, we
do not find that any other element of the blood is constantly affected,
although  it occasionally happens that the red globules are in excess.
  The clot in  typhus, in which, of course, the deficiency of fibrin is
considerable, is large, filling almost the entire of the vessel which con-
tains it;  is soft, being readily broken up on the slightest touch;  it is
flat, and  ill-defined, and the serum in which it floats is of a reddish
colour.
  The flat form and softness of the clot is to be explained by reference
to the diminished amount of fibrin, while its great size is accounted
for by the imperfect expression of the serum from the crassamentum,
as well by the fact that the red  corpuscular element of the blood exists
usually in its normal proportion, and is not unfrequently found to  be
even in excess.
  The important distinction which exists between  symptomatic or
organic fevers, and idiopathic, or non-organic fevers, is very essential
to be borne in mind, for in the former no such deficiency of the fibrin
exists as  we have seen to belong to the latter; the blood in inflamma-
tory affections, as will  be shown hereafter,  exhibiting a state of its
spontaneously  coagulable element  the  very reverse of that which
belongs to the  blood of idiopathic febrile disorders.   It must  also  be
recollected, that an idiopathic fever may, during its progress,  become
complicated with organic  lesion, a  circumstance which would affect
materially the  amount of fibrin in the blood, its effect being to increase
the  proportion of that constituent.

Increase  in the Amount of Fibrin in Inflammatory Affections, as in
    Pneumonia, Pleuritis, Peritonitis, Acute Rheumatism, Spc.
  While in the class of febrile disorders, of which we have just spoken,
a deficiency of the fibrin  in the blood exists, in another series of
affections, the  inflammatory, this element is found to be in  excess 
THE  BLOOD.
149
To constitute an  inflammation, however, two concurrent circum-
stances are required; it is not alone necessary that the proportion of
the fibrin  should be increased, but also that an organic  lesion  should
have occurred, these two pathological alterations bearing a close and
constant relation with each other.
   Since, then, the spontaneously coagulable element of the blood  in
the one class of disorders, viz: fevers, is deficient, while in the other
class, inflammations, it is super-abundant, it  follows that the specific
cause which gives origin to these two orders of maladies operates  in
two opposite directions;  its tendency in the one being to  diminish,
and in the other to augment the quantity of fibrin.
   The law of the increase in the  quantity of fibrin in  inflammatory
disorders manifests itself under  very remarkable circumstances; such,
indeed, as one would imagine to be but little favourable to  its mani-
festation:  thus, in the case of an inflammation supervening on  typhus,
in which we have seen that the normal scale  of fibrin undergoes  a
depression, a disposition to the  augmentation of that scale will become
apparent.   In the example of typhus complicated with local lesion, we
have two forces in  operation; the tendency  of one of which  is to
diminish the amount of fibrin, and of the other to increase that amount;
and the result of which forces operating at the same time is the pro-
duction of a mean effect.
   The proportion of fibrin in man in a state of health is estimated at
3  parts in every 1000 of the blood.   In a case  of inflammation occur-
ring in the course of typhus, the scale was found to be 5|  in  persons
affected with chlorosi^, in which we have seen that it is the globular
element of the blood which is  deficient, and attacked with capillary
bronchitis, acute  articular rheumatism, erysipelas, and pneumonia,
the proportion varied from 6  to  7 and 8; in acute inflammations
occurring in  healthy individuals, it oscillated  between 6 and 8; and
in  a  less  number of cases, between 7 and 10.   The highest  scale
recorded  by M. Andral is 10;  and this was met with  only in pneu-
monia,  and  acute rheumatism, while the  lowest was only  4: this
scale borders upon that which  is  regarded as normal, and is encoun-
tered only in sub-acute inflammations.
   It is not merely, however, in  pure and extensive cases of inflamma-
tion that  the proportion  of fibrin in the blood becomes augmented,
for we find it also  increased  in every organic  affection which  is
accompanied by even a slight degree of inflammation: thus in phthisis,
at the period of  the elimination of the  tubercle, as well as in  cancer, 
150
ORGANIZED  FLUIDS.
in which  there is inflammation of those portions of the organs, the
seat of the disease which  immediately surround the tuberculous, or
cancerous deposit, we  have also an  increased  amount of fibrin in
the blood.  This  increase,  even in the last periods of the  disorder
in phthisis, rarely exceeds 5 parts in the 1000.  The blood in con-
sumption  exhibits then not merely an excess of  fibrin, but also  a
depreciation in the proportion of its red element to the extent shown
under the heading Ancemia.
   There  is one condition of the system compatible with  a  state of
health,  under  which  also the proportion of the fibrin in the blood
is augmented, and  that is gestation.  It is  stated,  however, by
M. Andral, that this  increase manifests itself only in the three last
months of pregnancy, previously to which the scale of the  fibrin is
found to be slightly depreciated.   This augmentation goes on increas-
ing from the sixth to the ninth month, and is greatest at the  comple-
tion of  the  term  of utero-gestation, which fact offers a satisfactory
explanation of the reason of the liability to inflammatory attacks on
the part of women recently delivered.   The condition of the blood,
therefore,  in the last periods of pregnancy is allied to that state of the
vital fluid which is especially indicative of the existence in the system
of an  inflammation.
   The characters  presented by the clot in inflammation are almost
the reverse of those which distinguish it in fevers.   It is of moderate
size, of firm texture, frequently cupped, and its surface usually  covered
with the buffy coating  of a variable thickness.  The theory of the
formation of this  peculiar layer has already been entered into, and
the various circumstances under which it has been encountered have
now been noticed; we have seen that if occurs in two very different
states of the system, that it is present on the clot of blood abstracted
in anaemic conditions, as well as on that formed in blood withdrawn
in inflammatory states; in  the  first of these there is, in comparison
with the red corpuscles, a relative  increase in the proportion of the
fibrin, and in the  second, a  positive  augmentation of that important
element of the blood.
   The fact of  the existence of a super-abundance of'fibrin in the blood
in inflammatory states may be in some measure inferred from the
circumstance of the escape in inflammation of a portion of its fibrin, and
which doubtless is attended with a certain degree of relief to the organ
affected.  In many cases, however, it  is not alone the fibrin which
escapes, and which is  liable to become  organized, but also  the other 
THE  BLOOD.
151
constituents of the blood, its red and white corpuscular element, (the
latter probably constituting the pus which in certain  severe cases is
met with,) and the serum:  these  constituents, however, are not sus-
ceptible of organization, and are, where recovery takes place, removed
from the situation of their effusion by absorption.
  The discovery of the fact, that in inflammatory disorders an excess
of fibrin is formed, explains  the exact manner in which blood-letting
proves so  serviceable, viz r by removing from the system directly a por-
tion of its super-abundant  fibrin; so powerful, however, is the cause
which determines the formation of this excess of fibrin, that in spite
of the most energetic and frequent use of the lancet, the scale of that
element of the blood will frequently, and indeed does generally, ascend.

              Condition of  the Blood in Hemorrhages.
  Reference has been made to the frequent occurrence of hemorr-
hages in  two very distinct  classes of disorders, the plethoric and the
febrile.  In the first, we have  seen that it is  the red  element of the
blood which is absolutely in  excess over the other constituents of that
fluid, while, in  the second, it is  the fibrin which is deficient, the
globules being unaffected, and  existing  usually in their normal pro-
portion.   Thus, relatively to the fibrin in both series of affections, the
globules are always in excess, in reference to the first series, the pleth-
oric, being absolutely so, and to the latter, relatively super-abundant.
  While  it  is this excess of the red globules which  probably deter-
mines the occurrence of hemorrhages, the  nature and degree of these
losses  of  blood are modified by the amount of fibrin which that fluid
contains.    Thus, the character  of the hemorrhages occurring in
plethoric  individuals is very different from that encountered in persons
labouring under  fever  in most of its  forms; in  the first, we have
copious epistaxes and the effusion of blood into  the substance of the
brain, constituting  sanguineous apoplexy; in  the second, almost any
tissue of the body may be the seat of the effusion; the blood may escape
from the nose, the  gums, the  throat, or  the bowels, or it may be
poured out  beneath the skin in patches, constituting petechias, which
we meet with so frequently in  severe cases of typhus, and in scurvy.
The hemorrhages to which the plethoric are liable are for the most
part salutary, while those which take place in fevers  are as generally
prejudicial.   The treatment to be  adopted in the two cases is very
different; in the  one, it may be necessary to have recourse to vene-
section, with  the view of lessening the scale of  the red globules, and 
152
ORGANIZED  FLUIDS.
in the otner, such a mode of proceeding would in all probability be
fatal, the object in it being to restore to the blood its normal proportion
of fibrin.
   The distinction  which  has here been dwelt  upon between the
hemorrhages to which the plethoric are exposed, and those to whicli
the system is obnoxious in febrile disorders at an advanced period of
their attack, corresponds with the division of hemorrhages into active
and  passive; the former, or sthenic type, denoting the active, and the
latter, or asthenic, the passive hemorrhages.
   In disorders in which usually we have no excess of the red globules,
but in which the fibrin  invariably exceeds its usual quantity, as the
inflammatory, and in affections in which the red  element is constantly
deficient, but in which the red fibrin retains its proper proportion, as
in anaemic states, and especially chlorosis, we  find that hemorrhages
are of very rare occurrence, and hence again we are led to recognise
the  accuracy of the statement, that the  essential conditions for the
occurrence of hemorrhages are an excess of the red corpuscles, as
well as in certain cases a deficiency of the spontaneously coagulable
element of the bloed, viz:  the  fibrin.
   Between the condition of the blood, in  which there is a deficiency
of fibrin, as in most fevers, and that state of the system which occupied
so much of the attention of the ancient humeral pathologist, and which
has  been  denominated  the putrid, an  exact  identity exists, and the
greater  the  depression  in the scale of the fibrin,  the more manifest
does the putridity become.   While the blood is still circulating within
its vessels, we can scarcely conceive of its becoming putrid;  never-
theless, so great  in some cases is  the  deficiency of fibrin, and  so
proportionate the consequent  tendency to putridity, that even durinc
life certain symptoms indicative of this condition become manifest, as
the extreme prostration of the strength, the foetor which belongs to all
the excretions, and the vital  principle having escaped, the external
signs of decomposition almost immediately appear.
  The characters of the blood in hemorrhages  scarcely  differ from
those which we  have  pointed out as  belonging to it in fevers;  from
the small  quantity of fibrin, and  the excess of red globules, we find
that  the clot is large, ill-formed, very soft, and never covered with the
buffy coating, and  that finally, in a very short time,  it  undergoes
almost entire dissolution, the  only trace  of solid matter in the blood
consisting of a few shreds of fibrin.
   There is  one  disease, viz:  scurvy,  in  which a condition  of the 
THE  BLOOD.
153
blood, as regards  its fibrin, exists analogous to that which character-
izes fevers, and in which also the same tendency to repeated hemorr-
hages and to the formation of petechias belongs, as is witnessed in fevers.
  It is  a question for  consideration whether  the  deficiency of the
fibrin referred to is the real cause of  the  proneness of the blood to
decomposition and dissolution; and whether, if this be the case, there
is not some other prior cause which leads to and regulates the extent
of the diminution of the physiological standard of the  fibrin.
   The  experiments of Magendie  show that the mixture  of certain
alkaline substances with the blood not merely preserve it in a fluid state,
but restore it to the fluid form, even after it has once coagulated.  M.
Magendie injected into the veins of living  animals a certain quantity
of a concentrated solution of the sub-carbonate of soda, and found  that
in the dead bodies of these animals the blood was almost entirely  in a
fluid state, and  that even  during life they presented many of the
symptoms which are acknowledged to  denote  a  state of dissolution of
the blood.
   The alkaline condition of the blood in scurvy, in which the prone-
ness to  hemorrhage is so great, is well known.
   A fluid state of the  blood is said to exist in  those who have died
from the bite of serpents, and it is most probable that in like manner
the  effect of the imbibition of  a poisonous miasma  is to cause the
blood to retain its fluidity.
   The  deplorable effects which  sometimes ensue from a  dissection-
wound are most  probably  due to the  entrance  into  the  blood  of a
poisonous matter, and in fatal cases we have all the signs indicative
of a dissolution of the blood.
   It is  likewise  asserted, that any violent impression made on the
nervous system,  either through the influence of some strong  moral
emotion, or as the result of a blow, especially on the pit of the stomach,
an electric shock, as of lightning, retards, or altogether prevents, the
coagulation of the blood, while at the same time it destroys life.  That
the same effect is likewise produced, though in a manner less obvious
and  less sudden, by the slow and continued  operation of any cause
which depresses  the  power of the nervous influence, so  as at length
to effect the health prejudicially, cannot be doubted.
   The proneness of children to hemorrhages,  their  liability to febrile
disorders, and the difficulty of restraining the bleeding which flows
from any breach  of continuity  which  the skin  may  have  suffered,
especially that of a leech-bite, in infants, are well known.    The state 
154
ORGANIZED  FLUIDS.
of the blood in children is  not commented  upon by the talented
authors to whom we have had such frequent occasion to refer in their
important pathological  essay on  the blood;  it is  most  probable,
however, that while its  globular element is somewhat in excess, that
in fibrin it is equally deficient.
   With one other remark we will bring this short chapter on hemorr-
hage  to  a  conclusion, and  proceed in the next place to consider the
effect produced upon the economy by the deficiency of another element
of the blood.  The statistical and historical details of epidemics clearly
prove that those dire forms of disease, of which extensive and alarm-
ing hemorrhages  were  such frequent complications, have in  these
latter times become much more rare.  This happy result is doubtless
due to the advances made in  the arts and sciences, and to their more
extensive application in the  improvement of the hygienic condition of
mankind.

         Decrease in the Normal Proportion  of Albumen.
   It is now generally known,  that the majority of cases of dropsy
depend upon a pathological  alteration of some solid organ of the body,
as the heart and the liver;  most persons  are also aware of the fact
that other cases of dropsy  occur, which do not arise from  any such
morbid organic condition,  but  have their  origin, according to MM.
Andral and Gavarret, in a  pathological degeneration of one of the
elemental constituents of the blood.
   In the  dropsy which attends the advanced stages of  the affection
known by the name of Bright's disease of  the kidney, in that which
supervenes upon scarlatina, in hydropsies arising from insufficient and
improper diet, as well as in  those which occasionally follow suddenly
suppressed perspiration,  it has been observed that the urine  is always
albuminous,  and  the  writers just mentioned  have ascertained the
existence of a fact which stands in  close relation with the albuminous
excess in the urine in the instances enumerated, viz: that the blood
is  itself in these cases, on the contrary, deficient in albumen.   The
knowledge of these two facts, therefore, and the observation  that their
occurrence is so generally associated with dropsical effusion, has led
MM. Andral and Gavarret  to entertain the  opinion that a close con-
nexion exists between the  deficiency of  albumen in  the blood and
the forms of dropsy alluded to, and which  is probably that of cause
and effect.
   In speaking of non-organic  dropsies it has, until recently, been con- 
THE  BLOOD.
155
ceived sufficient to say that they depended as a cause upon impover-
ishment of the blood; but this expression we now know to be vague,
inasmuch as it does not convey any exact notion of the real changes
which the blood may have undergone: we have  seen  that the blood
may be rich in its red globules or in its fibrin, and also that it may be
poor in these  elements in almost  every proportion and degree.  Let
us see whether a deficiency  of either of the two  constituents  just
named predisposes  to dropsies.   In anaemic states, and  in  chlorosis
especially, we  have an impoverished state of the blood, and in these
we know that it is the red  corpuscles which are deficient;  and yet
daily experience shows us that dropsy in such states, and particularly
in chlorosis, even in its most severe forms, is  a very rare termination.
In febrile disorders again, we have, for the most part, an impoverished
condition of the blood, arising from the depression in the scale of the
fibrin, and yet of these we do not find dropsical effusion to be by any
means a frequent result.
   It is not excess of water in the  blood which  gives rise to dropsy,
for, if that were the case, then would it frequently occur in the dis-
order  to which we have referred, chlorosis, in which a greater
proportion of  water than is normal  exists in the blood.
   The causes of impoverishment of the  blood enumerated therefore
do not act as  exciting causes of dropsy :  there remains but one other
element of the blood, the  albumen,  for our consideration, and this we
have  seen to be constantly deficient in the blood in certain  forms of
dropsy, and we are therefore constrained to adopt the conclusion that
this depreciation in the scale of the albumen is intimately associated
with the occurrence of those forms.
  It does not appear, according to M. Andral, that the albumen can
undergo a spontaneous depreciation in the blood, similar to that of which
we have seen  that the red globules and the fibrin are susceptible;  this,
if correct, is very remarkable, and  hence it would follow that when-
ever a deficiency of the albumen of the blood exists, invariably, at the
same  time, the urine would  be  found  to be albuminous,  provided
always that no dropsical  effusion existed, the effect of some organic
malady.
  In most organic dropsies the diseased organs act as exciting causes
of the serous effusion by the mechanical impediment which their altered
structure and  enlarged size  present to the circulation in the vessels,
and which, therefore, relieve themselves by permitting the escape of
a portion of their contents.  In Bright's disease, although the kidney 
156                 ORGAEIZED  FLUIDS.
 is affected, that organ does not concur in the formation of the dropsy,
 except in a manner altogether indirect, and to such an extent only, as
 that the  pathological alteration which its substance undergoes is of
 such a nature, as  to afford greater  facility to the passage  of  the
 albumen through it.
   The serosity effused in cases of dropsy is not identical in its con-
 stitution with the serum of the blood; it contains usually far less of
 the inorganic constituents which are held in solution in healthy serum,
 as well as a far less proportion of albumen, than  that which  belongs
 to serum in its  normal  state.  The physiological  standard  of  the
 albumen in the blood  is eighty in every thousand parts; in sixteen
 cases in which the  serous effusion was analyzed by M. Andral,  the
 scale was found to  oscillate between 48 and 4, these two numbers
 representing the highest and the lowest proportions.   In six cases  of
 hydrocele, the amount of albumen was, as represented in the following
 figures, 59, 55; two of 51; 49, 35.   It should be remarked that none
 of these  analyses refer to cases of dropsy connected with excess of
 albumen in the urine.  It would be interesting to ascertain the amount
 of the albuminous element contained in the serum effused in such cases.
   MM. Andral and Gavarret state that  they did not find that either
 the  cause of the hydropsy, or its seat, excited any influence over the
 quantity of albumen of the effused serum; but they remarked that the
 amount did in some degree depend  upon the  condition of the consti-
 tution, and that the more robust its state, the greater  the proportion
of the albumen: in this way the higher scale exhibited in the six cases
of hydrocele may be accounted for, their occurring in persons all of
whom were  young  and strong;  and thus, also, the  great depression
of that scale may be explained in those whose  constitutions have been
weakened by repeated tappings.
  Two explanations may be given of the reason why blood less rich
than ordinary in albumen should give rise to serous effusion.  The
first is, that the abstraction of the albumen may alter the density of the
serum, and thus permit more readily its escape  through the walls of
the vessels;  the second is, that blood deprived of its albumen becomes
less yielding, and so glides less easily along  the walls of  the capillary
vessels, thus occasioning in them an obstruction to the circulation
and consequent effusion of serum.  Of these explanations, the former
is perhaps the more probable.
  The proportion  of water in all serous  effusion is, of course, con-
siderable, and  is greatest  in those cases  in which  there  is least 
THEBLOOD.                     157
albumen.   The mean proportion of water in the serum of the blood
is 790 in 1000 parts; in the fluid of dropsies the highest scale hitherto
observed is 986, and the lowest 930.
  The fluids effused in  burns and  scalds, and as the result of  the
application of a  blister, and which  are always preceded by some
degree of inflammation, are also rich in albumen.  The very curious
observation is  made  by M. Andral, that  in cases  where dropsical
effusion exists in  more than one  situation in the same individual, that
in each locality the fluid effused may exhibit a very different propor-
tion of  albumen.  Thus,  in  a woman attacked with  an  organic
affection of the heart, there were thirty parts of albumen  in the fluid
of the pericardium, while there were but four parts in the  serosity of
the cellular tissue of the inferior extremities.
  In having thus ascertained the  different modifications  in quantity
which the three great elements of the blood may undergo—the globules,
the fibrin, and the albumen—it yet must be confessed that the patho-
logical history of the blood  is still very  far from being rendered com-
plete.   It is more than  probable that rigorous chemical analysis  will
disclose  the fact, that  the  several  extractive as well as inorganic
substances which exist  in  the blood, vary greatly in amount in  the
numerous disorders  to  which the  human  body is liable.   From  the
great quantity of these substances  which  are found in the urine, it
would appear that the grand purpose fulfilled in the economy by  this
excretion is that of regulating  their amount in the blood,  and of
reducing it to a standard consistent with a physiological condition of
the system.
  Into this branch of the pathology of the blood inquirers have as yet
scarcely entered; and there can be no doubt but that investigations
instituted in this  direction would be  attended by the  development of
many important facts.

                  Therapeutical Considerations.
  The practical value to be attached to the various particulars related
in the preceding pages on the pathology of the blood, is  so obvious
that it needs not  to be illustrated at any great length.
  The knowledge of the particular element of the blood which in  any
state of the system or disease may be affected, inasmuch as it discloses
the chief cause of such condition or malady, furnishes the practitioner
with an unerring principle upon which the nature and the extent of
the treatment  adopted should be founded.  Hitherto, the chief guides 
158
ORGANIZED FLUIDS.
in practice have been based upon experience and clinical observation;
both,  doubtless,  of  high  importance; but  still not in many  cases
sufficient to detect the cause of a malady, and therefore not in them-
selves equal to the determination of the exact line of treatment to be
pursued, or of the extent to which that line  should be followed.
  We are now not merely acquainted  with the bare fact, derived
from experience, that in anaemic conditions of the system the different
preparations of iron are  useful, but we  have dived deeper into the
mysteries  of organization, and we now know the reason why iron is
necessarily so beneficial in the disorders to which such a condition
of the system gives rise.
  The precise objects to be held in view, in the employment of every
remedial appliance  in the treatment  of inflammatory affections and
fevers, we are now acquainted with; and by our present knowledge we
can judge of the propriety  and extent  of  usefulness of the various
plans  of treatment which in times past have been had  recourse to, or
which still continue to be applied; and we can detect the reason why
one particular mode of treatment should have been more successful
than another.

   Becquerel and Rodiers Pathological Researches on the Blood.
  MM. Becquerel and Rodier* have traversed the same ground  as
MM. Andral and Gavarret in reference to the blood, which they have
examined both in health and disease.
  These authors confirm many of the more important results obtained
by antecedent observers, but question the accuracy of some of those
results, and  add new facts in  relation to the normal  and abnormal
composition of the blood.
  The results which confirm those which had been previously obtained
are the following:
  1. The augmentation of the  fibrin in inflammations, the establish-
ment  of which fact is especially due to MM. Andral and Gavarret.
  2. The diminution of the globules in chlorosis, in the condition
denominated the anaemic, and under the influence of fasting; a fact
stated by  M.  Lecanu, and confirmed  by MM. Andral  and Gavarret.
  3. The diminution of the globules  from hemorrhages and anterior
bleedings; a result which, signalized for the first time by MM. Prevost

  * Gazette Medicate de Paris, 1844.  "Recherches  sur la Composition du Sang
dans l'etat de Sante et dans l'etat de Maladie." 
THE  BLOOD.
159
and Dumas, has been confirmed in the numerous analyses of MM.
Andral and Gavarret.
  4. The little influence of bleedings upon the scale of the fibrin.
  5. The diminution of the albumen in the  malady of Bright, as
indicated by Gregory, Rostock, Christison, Andral and Gavarret.
  Of the results which differ from, and perhaps invalidate those of
antecedent observers, the principal are—
  1. That the scale TWo> given  as representing the mean of the
globules in  a  state of health, is too low, and is not the same in man
and in woman.
  2. That the scale representing the fibrin as T/TJ is too high.
  3. That  there is not alone in  plethora an augmentation  of the
globules, as signalized by M. Lecanu, and as has been admitted by
MM. Andral and Gavarret.
  4. That the scale of the globules is not preserved in its normal
proportion in the majority of acute affections.
  5. That the depression in the scale of the fibrin in severe fevers
is but little constant.
  The more important of the new  results are the following:
  1. That the scale 141 expresses  the mean number of the globules
in man in a state of health, and that of 127 represents the average in
woman.
  2. That the ordinary scale of the fibrin is 2 • 2, and the mean 3.
  3. That in  plethora there is an augmentation of the quantity of
the mass of the blood.
  4. That the influence of  disease upon the  composition of the
blood is to  occasion from  the  commencement a diminution  in the
proportion of the globules, and this diminution continuing during the
progress of the malady, ends in the production of the anaemic condition
of the system.
  5. That there is an absolute excess of  fibrin  in many \?ases of
chlorosis and of pregnancy, and that its diminution is far less constant
than has been considered in fevers.
  6. That the albumen of the  blood diminishes under the influence
of illness; that it is more considerable in inflammations;  and further,
that the diminution is in direct relation with the augmented amount
of fibrin, which it may be presumed is formed at the expense  of the
albumen; that there is not only a very great diminution of albumen
in the  malady of Bright, but also  in certain affections of the heart,
accompanied by dropsy, and in certain severe forms of puerperal fever. 
160
ORGANIZED  FLUIDS.
   7.  That  the  amount of cholesterine  and of acid fats increases as
 we advance in age; but  that this increase is not felt until  from  the
 fortieth to the fiftieth year; that it is also found in augmented quantities
 in the blood in constipated states of the system, and in jaundice, with
 retention of the bile and decoloration of the faeces.*

                 The Blood in the Menstrual Fluid.
   The menstrual fluid contains all the elements of the blood, especially
 the red and white corpuscles, and  it is therefore in the same manner
 as the blood itself susceptible of coagulation.   In addition to the con-
 stituents of the blood, we find the  uterine discharge to be composed
 of vaginal mucus, mixed up with numerous epithelial  scales, which it
 has acquired in  its passage along the  vagina.
   Unlike, however, in one respect the blood itself, which in a state of
 health is alkaline, the menstrual fluid is acid,  its acidity arising from
 its admixture with the vaginal secretion.

                     Transfusion of the Blood.
  It has been stated, and the statement is most probably correct, that
 between the size of the blood corpuscles and that of the capillaries
 of the same animal, an exact relation exists, and it  is by reference
 to this fact that  the fatal effects which have so often ensued, from the
 transfusion of the blood of one animal into the vessels of another, have
 been  apparently so  satisfactorily  explained.    The  little vessels, it
 has been said, are too  small to admit the  larger globules of the new
 blood; a mechanical impediment is thus offered to the circulation of
 the blood in the capillaries, which stagnates in them, giving rise to
 constitutional disturbance, and ultimately to death.   This explanation,
 plausible as it appears, has been shown by  recent experiments to be
 erroneous, and that the true cause of the fatality which has so often
 attended the operation of transfusion, depends upon the difference
 which exists in the qualities of the fibrin in  the blood of two different
 animals,  or  even of two distinct individuals; this  is shown  by  the
fact that the transfusion of blood deprived of its fibrin is never followed
by the serious results to which reference has been  made.   Notwith-
 standing this fact, it is yet very evident that if the blood of an animal.
 the corpuscles of which are much  larger than the human blood disc,
  * The above remarks are abbreviated from an abstract of MM. Becquerel  and
 Rodier's work on the blood, by MM. Millor and Reiset, contained in the " Annuairr
 de Chimie," for 1846. 
THE  BLOOD.
161
and at the same time are of a different form and structure—such as,
for instance, those of some birds—be introduced into the vessels of
man, a very serious and probably fatal mechanical impediment would
be presented to their circulation through the capillaries.   Blood  cor-
puscles of a circular form, and but little larger than those of man,
might indeed make their way through the vessels in consequence of
the plastic nature of the globuline which composes them.
  The new globules thrown into the  system  by the  operation of
transfusion, although they would circulate for a time with the other
blood globules, would doubtless all become destroyed and removed in
the course of a few days, and this especially if the blood corpuscles
were different from those of  the animal upon which  the  transfusion
had been practised.

                   The Blood in an Ecchymosis.
  When a part is bruised to such an extent as to  occasion the  rup-
ture of the minute capillaries and  vessels contained in  it, blood is
effused, constituting an ecchymosis.  The same effect sometimes takes
place, not as the  result of the  application of  external violence, but
from disease, the solid tissues, and that of the vessels especially, giving
way through debility, and permitting the escape of their contents, as
occurs in malignant and putrid fevers, in  Purpura  Hcemorrhagica,
in scurvy, and in bed-sores.
  If a portion of the effused blood be removed from the  bruise, and
examined microscopically, the globules will be observed to be wrinkled
and irregular in form; corresponding with and depending upon internal
changes in the  condition of the blood effused, and which are indicative
of the occurrence of  decomposition,  certain  external appearances
will be noticed; the skin will appear mottled, different hues of black,
green, and yellow being intermixed, and  varying in intensity  until
the period of their total disappearance.
  The phenomena of decomposition precede  the disappearance of
the red corpuscles which are removed from the seat of injury, and
are returned to the circulation in a state of solution.   Now, were the
opinion true that the blood corpuscles are applied directly to the for-
mation of new tissue, a very different result to the decomposition and
solution of the globules, to  which we have referred, would be antici-
pated, and we should expect to find that the extravasated blood had given
rise to  an  adventitious and organized product, an  event to which
ecchymoses never lead.
                             11 
162
ORGANIZED  FLUIDS.
The Effects of certain remedial Agents upon the Constitution and
                  Form of the Blood Corpuscle.
  We have seen, in the remarks on the effects of reagents, that many
solutions and substances applied to the corpuscles, after their abstrac-
tion from the system,  modify their form, appearance, and properties.
  Thus we have seen that in water, as in any other analogous liquids
of less specific gravity than the serum of the blood, that the corpuscles
lose their normal form, and  become  circular, their  colouring  matter
passing at the same time into the  fluid.
  We have likewise observed that in liquids of an opposite character,
and the density  of which equals  or exceeds that of the blood, their
form is  preserved, and even rendered  flatter than ordinary: thus,
their shape is well maintained or but slightly affected in  the  white of
egg, urine, the saliva,  concentrated solutions of sugar, of the  chlorides
of sodium,  and  of ammonium, and  the carbonates of potassa and
ammonia.
  The blood corpuscles likewise preserve their form  in  the  solutions
of other substances, the density of which would not appear to be very
great, but which are possessed of very strong and decided properties:
thus, they maintain their shape well in a solution of iodine, and become
but slightly contracted in that of chloride of sodium; while, according
to Henle, the  primitive flattened  form of corpuscles, swollen  by the
imbibition of water, may be restored to them by the application of
the concentrated saline solutions.
  Nitric acid produces an irregular contraction of the corpuscles.   It
has been remarked  in like manner that a  host  of substances  affect.
the colour of the corpuscles.
  But it is  not  alone the form and colour of the  blood corpuscles
which are affected by the  contact of reagents;  their properties also
are modified by them.
  Thus, the corpuscles to which iodine has been added are so hardened
by it, that they experience little or no change of  form on the addition
of water.
  The same is the case, according to Henle, after treatment by nitric
acid.
  The acetic, and one or  two other acids, it is  known, dissolve  the
corpuscles of the mammalia without  residue, but leave  almost unaf-
fected the granular nucleus contained in the red  blood corpuscles of
oviparous vertebrata. 
THE  BLOOD.
163
   The above are some of the more striking effects produced in the
 form, colour, and constitution of the blood corpuscles out of the sys-
 tem, on their treatment by reagents.
   Now, there is evidence to show that blood corpuscles, while they
 are circulating in  the body,  are  likewise  affected,  although  to  an
 extent less considerable, and therefore less appreciable, by substances
 and solutions introduced into the system through the medium of the
 lungs or of the stomach.
   Thus, we know that the blood changes its colour in the lungs and
 during its circulation through the  capillaries, and that these changes
 are dependent upon the relative  amount of oxygen and  of  carbon
 contained in the corpuscles.
   Again, it has been asserted by Schultz, as already  mentioned, that,
 accompanying these alterations of colour, there are also changes  of
 form, the corpuscles becoming more or less circular in carbonic acid
 and hydrogen gases, and flat in oxygen gas.  This assertion  I have
 myself failed to verify.
   It cannot be doubted, however, but that the form of the  red blood
 corpuscle must vary according to the variations of density experienced
 by the liquor sanguinis, and further but little  hesitation can  be felt
 in admitting that  this alteration of density does  really  attend upon
 particular conditions of the system; thus, in inflammatory affections,
 the liquor sanguinis is assuredly more dense than it is  in  states in
 which an  opposite condition of the  blood exists, that  in which the
 watery element abounds.
   After very copious imbibition  of  water,  also,  it can scarcely be
 doubted but that the density  of the blood is lessened,  and that  the red
 corpuscles are modified in  shape in consequence.
   Thus much for colour and form; let us see if we  are acquainted
 with any fact capable  of proving that the constitution  of red blood
 corpuscles is also influenced by the introduction into the stomach  of
 remedial agents.
  Schultz  relates  the  fact that the  corpuscles of the  frog,  in  the
mouth of which during life  iodine had been placed, resisted  for  a
longer time the action  of water.*  The truth of this most interesting
and important observation  I have myself verified.
  The blood  corpuscles of a frog, which were subjected to the vapour
of iodine, underwent  no appreciabe change of form in water for
nearly an hour during  which  they were observed,  a time more than
           *  Das System der Circulation.   Stuttgard, 1836, p. 19. 
164                 ORGANIZED  FLUIDS.
sufficient to ensure the complete change of shape  and subsequent
disintegration of the blood discs of a frog not similarly treated.
  It may be observed that in the case related,  starch failed to detect
the presence of iodine, although  this was  set free by previously dis-
solving the corpuscles by means of acetic  acid.
  After the relation  of the  above facts, it is  evident  that  remedial
agents do affect in several important particulars the blood corpuscles
of the living  animal, and it is further probable that a considerable
proportion  of their remedial influence is dependent upon the nature
and extent  of their power in modifying the red blood disc.

The Importance  of  a Microscopic  Examination of the  Blood  in
                        Criminal Cases.
  In criminal cases it is sometimes a matter of the highest importance
to the furtherance of the ends of justice,  that  the nature of certain
stains, observed on the clothes of an accused person, should be clearly
ascertained.
  The fact usually to be determined is, whether the stains in question
are those of blood or not.   Now, in  the  decision of this important
matter, the microscope comes to our aid in a manner the most deci-
sive and convincing.
  If the stain be a blood stain,  and if  its examination be  properly
conducted,  the microscope will lead to the detection  in it of the blood
corpuscles themselves, both white and red.
  The inquiry having been proceeded  with thus far,  and the stain
having been proved to be  one formed  by blood,  it still remains  for
decision, whether the blood thus detected is human or not.
  In the solution of this difficulty  the  microscope  likewise affords
considerable assistance, and this of a kind  which can be obtained  in
no other way.  Although by this instrument we are not able to assert
positively  from an examination  of the  blood  stain  itself, free from
admixture with any other organic material, that  the blood  is really
human, we yet shall have it in our power  very frequently to declare
the converse fact, viz:  that  a certain blood stain is constituted  of
blood  which is not human, a particular on  the knowledge  of which
the life of an accused  individual might depend.
  Thus, if we find that the  blood globules  are of a circular form, and
destitute of nuclei, we may safely conclude  that  they belono-  to
an animal of the class Mammalia, although, at  the same time, we  in
all probability should not be able to pronounce upon  the name of the 
THE  BLOOD.
165
mammal itself; if, on the contrary, the blood corpuscles are elliptical,
and provided  with a granular nucleus,  we  may  be equally certain
that they do not appertain to that class, but either to the  division of
birds, fishes, or reptiles.'
  By the size  also as well as the  form of the corpuscles, some idea of
the animal from which the blood was derived might be formed;  and
if we cannot  pronounce with certainty  upon this,  we shall  at all
events, and at all times, be able to go the length of affording negative
evidence, and  of asserting  that the  corpuscles do  not  represent the
blood of certain animals which might be named, and a knowledge of
which fact might prove of extreme importance.
  To show the valuable  nature of the  evidence which it is in the
power of a medical  man who  makes a right use of the  microscope
frequently  to afford, in criminal inquiries, we will suppose the follow-
ing case:
  A person is apprehended on the suspicion of having been concerned
in a murder.   On his clothes are observed certain stains; upon these
he is questioned; he admits that  they are blood stains, and states that
he had been engaged in killing a fowl, and that in this way his clothes
had acquired  the  marks.   The stains are now submitted to micro-
scopic examination; the blood of which they are constituted is found
to belong to an animal of the class Mammalia, and not  to that of
Aves; discredit  is  thus  thrown upon   the party suspected,  fresh
inquiries are instituted, fresh discoveries made, and the end of  all  is
the conviction of the accused of  the crime imputed.
  But a  third  question presents itself, to  which it  is very necessary
that a satisfactory reply should be made,  viz: did the blood, of which
the stain is constituted, flow from a living or dead body?  This query
we will  proceed to answer.
  If a vessel be  opened during life, or even a few minutes after death,
the blood which issues  from it in a fluid state will quickly become
solidified from the coagulation  of the fibrin.
  But if, on  the other hand,  a  vessel be opened some  hours  after
death, the fluid blood which escapes will not solidify because it con-
tains  no fibrin,  this  element of the blood  having already become
coagulated in  the vessels of the body in which it still remains.
  Now, this act of the solidification  of the fibrin is deemed by many
  * The  only animals of the class Mammalia which have blood corpuscles of an
elliptical form, are those of the order Camelidct; they are, however, very small, and
destitute of nuclei. 
 166                ORGANIZED  FLUIDS.

 to be a vital act, and to be the last manifestation of life on  the part
 of the blood.
   It would appear, however, that the coagulation of the blood  should
 not be regarded as a vital act, seeing that blood which has been kept
 fluid for some time by admixture with saline salts will coagulate when
 largely diluted with water, and also, that blood which has been frozen
 previous to coagulation will undergo the process of solidification after
 it has been rendered fluid again by thawing.*
   Presuming, then, that the coagulation of the blood is not an act of
 vitality, the inference to  be deduced from the presence of coagulated
 fibrin in blood stains,  in which the corpuscles may be  detected, is
 scarcely weakened thereby, since the finding of such fibrin in such a
 situation, and in connexion with the blood corpuscles, scarcely admits
 of a rational  and probable explanation of its  occurrence  being given
 apart from the idea that the blood had issued from a body either liv-
 ing or but just dead, and in which  coagulation of the fibrin in  the
 vessels had not occurred.
  The blood stains, therefore,  which  contain  coagulated fibrin in
 them, it is but little doubtful, must have proceeded either from a liv-
ing individual, or from one but just dead; while, on the contrary, it
is as little to  be doubted, but that those stains which do  not contain
solidified fibrin, must have emanated from a body dead some hours,
or from blood which had already been deprived of its fibrin.
  From the disposition and form also  of the blood spots, some idea
can be formed as to whether the blood had sprit out of a living  body
or not.
  A few observations may now be made, first, on the length of time
after the formation of  blood stains at which the corpuscles can be
detected;  and second, on  the best  mode of proceeding in the exam-
ination of those stains.
  From observations which I have made, it would not appear that it
is necessary that the blood stain should be recent.   I am  inclined to
think that the period scarcely admits of limitation.
  Thus in blood stains six months old, I have  observed  the  corpus-
cles presenting very nearly Jhe form and appearance proper to  them
when recently effused,  and previous to their becoming dried up.
  In the blood of the frog, six months after  its abstraction from the
  * Dr. Polli has related a case in which the complete coagulation of the blood did
not take place until fifteen days after its abstraction.—Gazzetla  Medica di Milando,
 1844. 
THE  BLOOD.
167
 animal, I have observed  the  corpuscles, both red and white, and  in
 the former, the characteristic granular nuclei with so much clearness,
 that it would have been an easy matter to have  studied upon  them
 the development of blood corpuscles.
   The  observance of one  precaution, at least, is necessary for the
 successful exhibition of the microscopic characters of blood stains.
   Thus, water should never be applied to them, nor indeed any other
 fluid, the density of which is less than that of the serum of the blood,
 for all such liquids will occasion the discharge of the  colouring mat-
 ter of the blood corpuscles and an alteration of their  form; thus the
 circular but flattened corpuscles of the Mammalia will assume a glob-
 ular shape, as will also the  elliptical blood discs  of birds, fishes, and
 reptiles;  one of the greatest points  of difference  between  the  blood
 corpuscles of the former and latter classes being thereby effaced.
   Blood stains, therefore, should be moistened, previous to examina-
 tion, with some fluid, the density of which nearly equals that of the
 liquor sanguinis;  and I have found the albumen of the  egg to pre-
 serve the form of the corpuscles excellently well.
   Failing, however, in detecting the blood corpuscles, a result scarcely
 to be anticipated,  assistance may be  derived  from  a  toxicological
 examination of the blood.
   The only tests peculiar to the blood are those which have relation
 to the haematine.  This  principle it  would,  however, be difficult  to
 obtain from blood stains in sufficient quantity for the purposes of
 copious chemical analysis.
   Nevertheless, corroborative evidence of the suspected character of
 a stain might be obtained by its general chemical analysis, and which
 should be treated as follows:
   The stain should first  be  moistened with cold distilled water;  as
 much of the  matter  of it should  then be  removed as possible, and
 placed in a test  tube with an additional quantity of water.   This
 being agitated, the colouring material, if the stain be  a blood stain,
 will be dissolved by the water, imparting to it a pinkish colour, while,
 provided the blood flowed from the body during life, or at all events
 within a few minutes of decease, suspended in the liquid, will be seen
shreds of fibrin.
  This solution, when heated to near the boiling  point, will become
turbid, and deposit flakes of albumen.
  The same thing will occur when it is treated with nitrate of silver
or bichloride of mercury. 
168                 ORGANIZED  FLUIDS.
   The addition of a strong acid or alkali  turns the colouring matter
of a brown tint.
   These results, however, are common to other mixtures of animal
substances in combination with colouring matter besides the blood,
and no one of them is perfectly characteristic.
   It would therefore appear that the microscope is capable of reveal-
ing evidence much  more satisfactory in  reference to the nature of
blood stains, than that which it is possible  to derive from  chemical
examination.
   Finally, it may be observed, that during the examination of blood
stains, other substances may be detected in  connexion with them, the
presence of which would reveal not merely  their nature, but also the
seat from which the  blood forming them had flowed;  thus, some of the
various  forms  of epithelial cells and  of hairs, may occasionally be
encountered in them.
  We now bring to  a conclusion this long article upon the grand for-
mative fluid of the system, the blood, and pass to the  consideration of
other  fluids of the economy, viz: pus  and mucus. 
THE  BLOOD.
169
                           PREPAEATION.
   [Fresh  blood  may be  examined by placing a very small  quantity on a
plain glass slide, thinning it with a little serum, and quickly covering it with
a piece of thin glass.   The object is then ready for examination, and will
require a power of 600 to 650 diameters, to well define its corpuscles.  The
different reagents may  then be introduced by means of a pipette: the most
striking in their effects, are water, acetic acid, nitric acid, and alcohol.
  Perhaps the  most  marvellous sight  that the microscopist  can behold, is
that of the  circulation of the blood.   For this purpose, the frog is  usually
selected, and instructions have already been given for preparing the tongue,
so as to show this phenomenon.
  There are other portions of the  frog in which  the circulation  may be
readily seen ;  one of these is the transparent part of the  web of the hind
feet.  In this  manipulation, the body  of the frog is to be secured to  the
frog-plate, by  means of a narrow bandage or piece  of tape.  Those who
do not possess a frog-plate, may readily make one by taking a piece of thin
board about six inches long, and three inches wide; in this, a hole an inch
square is to be cut near  one end.  The frog, secured in the bag, is tied to
the solid part of the  thin board, in such a manner  that the web of the  foot
may be brought over the hole.   The foot is then stretched out to the utmost,
and  fastened  in  this condition by means of strings  tied  to the toes,  and
secured to small pegs, or tacks, driven in at the  margin of the board.
Another method  of securing the web in a state of  tension, is by means of
pins run through the toes, and fastened to the board.   The plate, when ready,
is placed upon the stage of the microscope, and the web may be examined
by means of a power  from 50  to 100 diameters.   Any  very transparent
part may be examined with a much  higher power,  even to 670 diameters.
The web should be kept  moist with clear water.
  Mr. Quekett observes, (page 339) " A frog so mounted, is capable of exhibit.
ing many of the effects of inflammation ,• if, for instance, a spot in  the web
be touched with the point of a needle,* or a small drop of  alcohol, or other
stimulating fluid be placed upon it, the circulation will stop in that part for
a longer or shorter period, according to the amount of injury inflicted ;  the
vessels in the neighbourhood will soon become turgid, and even sometimes be
entirely clogged up with blood;  if no further stimulus be applied, they  will
be seen to rid  themselves of their contents as easily as they  became full,  and
after a time, the circulation will be restored in every part.   For those who
are unacquainted with the parts which may be observed  with  the micro-
scope, in the foot of the frog,  it may be  as well  here to  state,  that  the
majority of vessels in which the blood is seen  to circulate,  are veins  and
capillaries;  the former may be known by their large size,  and by the blood
moving in them from the free edge of the web towards the leg; also,  by their 
170
ORGANIZED   FLUIDS.
 increase in diameter in the direction of the current;  the latter are much
 smaller than the veins, and  their size is nearly uniform;  the blood also cir-
 culates in them more quickly.   The arteries are known by their small size,
 and by the great rapidity with which the blood flows in them; they are far
 less numerous than either of the other vessels, and, generally speaking, only
 one can be  recognised in the field of view at a time; in  consequence of
 their being imbedded deeper in the tissues of the web than the other ves-
 sels, the circulation cannot be so well defined as in the latter.  The black
 spots of peculiar shapes that occur in all parts of the web, are cells of pig-
 ment, and the delicate hexagonal nucleated layer, which, with a power of
 one hundred diameters, can be seen investing the upper surface of the web,
 is tesselated epithelium."
   If the lung or mesentery of the frog be  desired  for exhibition,  and they
 will both be found to display the most beautiful sight that  can be conceived,
 the following method  must be adopted: The frog must be dipped in water,
 at about 120° temperature; this heat will destroy muscular action, but will
 not suspend the circulation.   The animal is then to  be opened, and  the lungs
 full of air will protrude;  one of these is bent over on a  plain  glass slide,
 and may be then viewed with a low  power.  The mesentery may be  dis-
 sected out, and viewed in  the same way.
   When the tad-poles of the water-newt and frog can  be found, and  they
 are abundant in the latter summer and early fall months,  the tails of these
 little creatures afford beautiful views of the circulation.    No further prepa-
 ration is necessary than  enveloping their bodies  in bibulous paper, leaving
 their tails to project;  they are then placed  on the stage of the  microscope
 in a watch-glass or live-box, and without any pain or injury to the animal,
 may be  observed for hours, by keeping the  bibulous paper moistened with
 water.
                          PRESERVATION.
   The blood corpuscles may be readily preserved for future  examination,
by placing a small quantity of fresh blood on a plain glass  slide, and rapidly
passing the slide backwards and  forwards, so as to dry the blood as soon  as
possible.  The corpuscles will then be found to be but little altered in form •
they are then to be covered with a piece of very thin glass, which must be
cemented  down with  gold size, taking care to paint on a very thin layer at
first, and a thicker one afterwards, when the first has become dry.  Blood
corpuscles, so preserved, will keep for years.   They may  also be preserved
in the flat cell, with Goadby's A-2 solution, or in a weak  solution of chromic
acid, care being taken that the cell be tightly sealed.
   Specimens of the blood of many birds, fishes, reptiles, and mammalia,
may  be readily  procured,  and   when  preserved in the  manner  already
described, will form objects of great interest.] 
MUCUS.
171
                     ART.  III.—MUCUS.

  We have seen that the blood consists of two parts, the one  fluid,
the liquor sanguinis, the other solid, the globules;  the same constitu-
tion belongs also to  mucus as well as to  some  other of the animal
fluids, as, for example, pus and milk.
  Mucous globules find  their  analogue in the white corpuscles of the
blood, while the fluid portion  of mucus resembles closely the fibrin of
the blood, fibrillating or  resolving itself into fibres in the same manner
as the fibrin.   From this fact there  can  be no doubt but  that the
transparent or fluid constituent of mucus is mainly composed  of fibrin.
  It is probable that the fluid portion is the only essential constituent
of mucus, and that the globules  are connected with it merely in an
indirect and secondary manner, notwithstanding that their presence
is all but constant.   The correctness of this view is in some  measure
sustained by the fact, observed first by M.  Donne, that the mucus
obtained from  the neck of the  uterus, in  young girls, is invariably
free from corpuscles.
  It is with the solid particles of the mucus that we shall be chiefly
occupied, for they  more properly enter into the domain of the micro-
scope ; the fluid element eludes to a great extent  the power of this
instrument, and the detection of its properties enters  principally into
the province of the chemist.

                        GENERAL  CHARACTERS.
  Healthy mucus,  in  its fluid state, is a transparent, viscid and jelly-
like substance,  which does not readily become putrescent; in its dried
condition, it assumes a dark appearance, and a  horny and  semi-
opaqe texture;  in  water it swells up, reacquiring most of the  prop-
erties which characterized it when recent.  It sometimes exhibits an
acid,  and sometimes  an alkaline  reaction, according to the  exact
structure of the mucous membrane  by which  the mucus  is  itself
secreted.
  Mucous membranes, therefore, as might be inferred from the con-
cluding passage of the  preceding paragraph, do  not all present a
constitution precisely similar  the one to the other;  and on their differ-
ences of organization a division of them  into three  classes may be
instituted, as has been pointed out by M. Donne. 
172
ORGANIZED  FLUIDS.
  The first class of mucous membranes  comprises  those which are
contiguous .to the outlets of the body, and which  are  to be  regarded
as extensions of the skin, participating in  all  its properties:  thus, the
fluid secreted by this class of mucous membranes manifests, like that
of the skin, an acid reaction, and the same epithelium which invests
the  latter belongs also to the former; in other respects the corres-
pondence  is likewise exhibited, the membranes under consideration
manifest the  same sensibility,  the  same  freedom from hemorrhage,
which characterize the skin; they in like manner ulcerate less readily,
and are never furnished with the vibratile cilia which belong to the
second class of mucous membranes, viz: the true.  This first-described
class of membranes may be denominated false mucous membranes;
and, as an example of it, the vagina may be cited.
  The membranes which belong to the second class are  situated
more internally than  the last, and have scarcely any thing in common
with those of the first class:  the mucus secreted  by them constantly
exhibits an alkaline reaction, and the epithelium which invests them
is of a totally different structure, the cells which constitute it  being
cuneiform, and in some situations provided with numerous vibratile
cilia: the general  properties of this class  of membranes are also
opposed to those of the  previous  division:  thus, they are  but little
sensitive to the touch, are frequently the seat of hemorrhages, and
ulcerate with much facility.  The membranes of this class are  to  be
considered as the true mucous membranes, and that which  lines the
trachea and bronchi  may be instanced as the type of this class.
  The third  class is more artificial  than  the two preceding ;  the
membranes which it comprises exhibit in a greater  or less degree
the  characters  of each of the divisions  already described, between
which they are intermediate in situation, as in structure, participating
in the characters of the false or true mucous  membranes more or less
according to  the  preponderance of either  of these classes.   The
membranes  of this division may be called mixed, and those  of the
mouth and nose may be regarded as typical.
  Now, however useful for the purposes of description the  above
classification may be, it must still be remembered that it is, to a very
considerable degree, arbitrary; the membranes which we have described
as false mucous membranes belong rather to  the skin than to true
mucous structure, while the mixed  membranes exhibit only the grad-
ual transition from the external skin to  the  internal true mucous
membrane:  thus, strictly speaking, there  is but one  class of mucous 
MUCUS.
173
membranes, and that  the  true.  Corresponding with the differences
which have been pointed out as characteristic of the three classes of
mucous membranes,  there are others appertaining to  the  mucus
secreted by each of these orders of membranes,  and which arise from
their diversity of structure, and which serve to distinguish the mucus
of the one class  from that of each of the other classes.
   1st.  The mucus proceeding from true mucous membranes is vis-
cous and  alkaline, containing, imbedded in its  substance, numerous
spherical,  semi-transparent,  and granular  corpuscles of  about the
22Vo  °f an mch in diameter (see Plate XI. fig.  1),* having  a  some-
what broken  outline, as well as occasionally epithelial cells more or
less cuneiform,  and sometimes provided with cilia.  These corpus-
cles are for the  most part  nucleated, they are not at first soluble in
water, but swell up in  that fluid to two or three times  their former
dimensions (see Plate  XI.  fig.  3), and, like the white globules  of the
blood, to which  they bear  the closest possible resemblance, they con-
tract somewhat  under  the  influence of acetic acid, and are soluble in
a concentrated solution of ammonia.
   2d. The mucus secreted by false mucous membranes, or those which
are analogous to the skin,  although more or less thick, does not admit
of being drawn  out into  threads, is acid,  and,  in place of spherical
globules, contains numerous scales of  epithelium, which differ from
true mucous  globules in their much larger  size, flattened form, and in
their irregular and very frequently oval outline: these scales, like the
true mucous  corpuscles, are nucleated,  and the nuclei comport them-
selves with chemical reagents,  in the same manner as the globules of
mucus.
   Example:—the mucus of the vagina.  (See Plate XII. fig. 1.)
   3d. The mucus proceeding from the mixed or  transition membranes
is  sometimes  acid, sometimes alkaline, at others neutral,  and contains
a mixture of true mucous corpuscles and epithelial scales, the relative
proportion of each of which varies according  to the exact structure
of the membrane by which it is furnished.   (See Plate XII. fig. 2.)
   These divisions of the mucus into three  different kinds, although to
some  extent artificial, as already observed, are yet not without their
practical utility.

  * A law having reference to  size, and the importance of which will be hereafter
demonstrated, may  here he announced.  It is that the several structures, especially
the corpuscular ones, entering into the composition  of the animal organization, bear
a near  relation of size the one to the other. 
174
ORGANIZED FLUIDS.
  The microscopical and chemical characters of mucus likewise vary
much, not merely according to the general organization of the  mem-
brane by which it is secreted, but also in accordance with the condi-
tion of the membrane itself, with  the degree of irritation or inflam-
mation  to which it is subject, and with the precise  nature  of  the
disorder by which it is affected;  thus, sometimes, the mucus secreted
by the  lining membrane of the nose is thin and watery, the fluid
element being in excess, and at others it is thick and opaque, its solid
globular constituents super-abounding.   Its  colour also as well as its
consistence  exhibits  various  modifications  in pathological  states,
being sometimes white, greenish  or yellow.
  The description of the different forms of epithelial cells alluded to,
and which are occasionally encountered in the mucus  mixed up with
true mucous  corpuscles, belongs not to  the fluids, and will be  given
in detail under the head of Epithelium,  in  that division  of the work
which  is devoted to  the consideration  of the  solids  of the human
body;  the structure,  form, size, properties and nature  of  the true
mucous corpuscles may here be described with advantage.

                    MUCOUS  CORPUSCLES,
  Structure.—The  mucous corpuscles,  which  are colourless, and
mostly of a circular form, are each constituted of a nucleus, an envel-
ope,  an intervening fluid substance, and numerous granules, which
are diffused generally  throughout the entire of the  corpuscles, being
contained within the cavity of the nucleus, in the space between this
and the outer envelope, and, lastly, in the substance of the envelope
itself; this  arrangement  imparting a granular  texture to the entire
corpuscle.  (See Plate XI.)
  The nucleus, like the corpuscle  itself, is  a circular  body of  about
one-third, or one-fourth its size: it sometimes occupies a central,  but
very frequently an eccentric position in the mucous globule: it is not
at all times visible, although very generally so, without the  addition
of reagents, the best being water and acetic acid.
  The  addition of water to  mucous  corpuscles  discloses, in  the
majority of them, but a single nucleus (see Plate XI. fig. 3); in some,
however, two and even three or four nucleoli appear,  these resulting
from the division of the substance of the single primary nucleus.
  The effect  of a weak solution of acetic acid is the same as that of
water, except that an  additional number of corpuscles  are seen after
its application to possess the  divided nucleus, while  in others  the 
mucus.                         175
single nucleus is observed to be oval, and occasionally contracted in
the centre—this form being the transition one from the single to the
double nucleus.   (See Plate XI. fig. 4.)
  If undiluted acetic acid be used, then all the corpuscles will present
a compound nucleus, consisting of two,  three, four, or five  nucleoli,
the usual number being two or three; the investing membrane at the
same time under its influence loses its granular aspect, and appears
transparent  and smooth.  (See Plate XI. fig. 5.)
  The formation of these nucleoli maybe thus explained:—The effect
of acetic acid is  to  contract the  entire  corpuscle; on the  nucleus,
however, it  would appear to operate with such  force  as  to  occasion
a complete division of its substance.
  The divided nucleus has been observed by many observers in the
pus globule, but its occurrence in the mucous corpuscle has  not been
generally noticed; this division of the nucleus has been considered to
constitute an exception to the law of the development  of a cell around
a single nucleus;  whether it ought to be so regarded is doubtful, see-
ing that these multiplied nuclei are usually the result of the operation
of a powerful reagent, and  are but rarely visible, unless as the conse-
quence of the application of some  reagent.
  Mr. Wharton  Jones has endeavoured to meet   this  conceived
exception, by supposing that the nucleoli are all enclosed within the
membrane of the nucleus.  I have myself, however, failed to detect
the existence of any envelope surrounding the nucleoli.
  Form.—The form of the  mucous corpuscle,  although usually
spherical, is subject to considerable variety, this depending frequently
upon the density of the  fluid in which it is immersed, but occasionally
also upon the amount of pressure to which it may be  subjected.
  Thus, in fluid which is very dense, the operation of exostosis is set
up between the corpuscle and the  fluid medium which surrounds it,
whereby a portion of its contents passes into that medium, as a con-
sequence of which its investing  membrane  collapses,  and exhibits a
variety of forms.   (See Plate XI. fig.  2.)
  Corpuscles thus affected nevertheless retain the power of reassuming
the form which properly belongs to them when  they are immersed in
water or any other liquid, the density of which  is less  than that of the
fluid contained within the cavity  of the corpuscle itself.  (See Plate
XI. fig. 3.)
  The form of the mucous corpuscle is also subject to alteration from
another cause, viz: pressure.  Thus, it is often seen to be of an oval 
176
ORGANIZED  FLUIDS.
form in thick and tenacious  mucus;  this shape results from the pres-
sure exercised upon the corpuscles by the almost invisible fibres into
which  the fluid part of mucus resolves itself, and which often become
drawn out in the adjustment of the  mucus on the port-object of the
microscope.  (See Plate XII. fig. 3.)
  The oval shape thus impressed upon it is permanent, because  the
pressure of  the fibres of the solid mucus ceases not to  act: if the
pressure, however,  be direct, and the corpuscle be immersed in  a
thinnish  fluid,  it will  resume  the spherical form, the compressing
force being removed, owing  to the elasticity with which it is endowed.
  Size.—The size of the corpuscle is also liable  to  much variation,
this resulting mainly from the condition of the fluid, as to density, in
which  it is immersed.
  Thus,  in  water, or any other fluid, the density of which is less
considerable  than that  of its  contents, the  corpuscle  imbibes by
endosmosis the liquid by which it is surrounded, to such an extent as
to cause  it to exceed, by two  or three times, its former dimensions.
(See Plate XI. fig. 3.)
  By reference, then, to the  two particulars  referred to, viz:  the
density of the medium in which it dwells,  and pressure, we are enabled
to explain all the varieties of form and size which the mucous  cor-
puscle  presents.
  Properties.—From  the preceding remarks  on the  structure, form,
and size of the mucous corpuscle, we perceive that in all these  par-
ticulars,  it  accords  closely with the white corpuscles of the blood;
we shall  now proceed  to show that there are  other points  of resem-
blance between the  two organisms.
  Thus reagents affect mucous corpuscles in a manner  precisely similar
to that in which they act upon  the white globules of the blood; water
causes them to increase in size, acetic acid contracts  them somewhat,
and renders the nucleus and the molecules more  distinct.   Between
mucous corpuscles and the white globules of the blood there  is, then,
a structural identity;  but let us see if there be not also a functional
correspondence.

                    NATURE  OF  MUCOUS CORPUSCLES.
  Mr.  Addison* conceives " that mucous and pus globules are altered
colourless blood-corpuscles," from which opinion it is  evident  that
gentleman believes that the white corpuscles of the blood pass normally
       * Transactions of Prov. Med. and Surg. Association, vol. xii. p. 255. 
MUCUS.
177
through the walls of the blood-vessels, although he does not appear
satisfactorily to have witnessed the exact manner of their escape.
  The perfect identity of organization existing between the colourless
corpuscles of the blood and mucous and pus globules, would predis-
pose the mind to  adopt that view as  sufficient and correct, which
endeavoured to prove that they all had a common origin in the blood.
  It must nevertheless be remembered that the notion of the identitv
in origin of  the mucous and pus globule  with the colourless blood-
corpuscle, rests upon  the single supposition that the latter does really
escape from the blood-vessels, in which originally it is formed.
  It seems to me, however, that this statement, to which I was myself
at one time disposed to attach some importance,  may be fairly chal-
lenged, seeing that the direct passage of the white corpuscles of the
blood appears  never to have been clearly witnessed.
  Moreover, the idea of any such escape of the white corpuscles is
opposed to that view which reasoning alone would lead one to enter-
tain; thus, if  the  colourless corpuscles of the blood  possessed the
power of escape from their vessels, no good reason could be advanced
why the red globules should not also pass  through them.
  If the capillary vessels terminated by  open mouths, which we know
that they do not in their normal state, then indeed it would be highly
probable that  mucous and pus corpuscles were the white 'corpuscles
of the blood, escaped  from the vessels.
  I am disposed, then,  to question  the  accuracy of the view enter-
tained by Mr. Addison, and to believe that the globules of mucus are
formed externally to the blood-vessels; the mucous glands or crypts
which are  scattered so  abundantly over  the  surface of all mucous
membranes, having a  considerable share in their formation.
  That the mucous-bearing glands are intimately connected with the
development of mucous corpuscles seems proved by the fact, that the
fluid expressed from them  is  filled  with corpuscles of a smaller size
than ordinary  mucous  globules, and destitute of any admixture with
epithelial scales;  these  corpuscles certainly could not  have found
entrance into the cavities of the glands from  without.  (See Plate
XI. fig. 6.)
  The opinion that the  mucous corpuscles are formed externally to
the  blood-vessels, is also supported by the  observations of M. Vogel,
ivho remarked that the plastic exudation which covers  the surface of
a recent wound contains, at first, only minute granules: these after a
time become  associated in  two's and three's, and surrounded by a
                              12 
178
ORGANISED  FLUIDS.
delicate envelope; finally,  fully-formed  mucous or  pus corpuscles
appear in the liquid.             »•
  Henle believes that the white corpuscles of the blood, of lymph
and of chyle, as well as those of mucus and pus, are elementary cells;
and he  says of the  pus  corpuscles that they are nothing else  than
elementary  cells   in process of being  transformed  into those  of
the tissue which the organism regenerates in the injured part; and of
the white globules of the blood he writes, they are, without the least
doubt, transformed into blood corpuscles.
  This opinion of Henle accords closely with that of Addison, who
believes, as already stated, that out of the white globules of the blood,
all other  corpuscles met with in the body are formed, the  former
escaping from the blood-vessels.
  I also regard the  white corpuscles  of  the  blood  as elementary or
tissue cells, although at the same time the views entertained by myself
respecting them differ from those both of Henle and Addison.  Thus,
I do not consider, with the former, that the colourless corpuscles are
transformed into red blood discs, nor with the latter, that every other
cell met  with in  the  animal  organism, proceeds  from the white
corpuscles of the  blood.
  The white corpuscles of lymph, chyle, and blood, I conceive to be
transformed into the epithelial cells, which constitute the epithelium
with which the internal surface of the vessels of the entire vascular
system is provided.
  The corpuscles of mucus  I  conceive  to  have an origin distinct
from the colourless globules of the blood; but in like manner I regard
them  as elementary or tissue  cells, believing  that they are  finally
developed into the different forms <of epithelium encountered upon the
surface of mucous membranes.
  The corpuscles of pus  are also elementary  cells and mostly altered
mucous  corpuscles.
  The view just expressed as to the nature of the white corpuscles
of the blood, is one which has but recently impressed itself upon my
mind.  It is not opposed, however, to the opinion previously put forth
of the connexion existing  between these corpuscles  and nutrition,
seeing, that, whether in their early stage of development as colourless
blood  globules, or in the  more mature condition of their growth as
epithelial scales, they are doubtless to be regarded as secreting organs,
and as  effecting  some important change in the constitution of th-
liquor sanguinis. 
MUCUS.
179
  The only respect in which the opinion that the colourless globules
of the blood are converted into the scales which constitute the lining
epithelium of the  vessels is at variance with a previously-expressed
view, is in relation to the escape of those globules as a usual occur-
rence; an opinion of Mr. Addison, in which I was formerly disposed
to concur, but which I am now inclined to reject.
  A final reason which may be stated for disbelief in  the identity as
regards  the  origin  of the  colourless corpuscles of the blood and
mucous globules, is the difficulty, not to say impossibility, of explaining
how these colourless corpuscles, having precisely the same form and
origin in the commencement, should, in one situation, be developed
into a shape and a structure so totally dissimilar to that which the
same corpuscles in another position exhibit, the varieties of form and
structure of epithelial  scales  into  which  the  white corpuscles are
supposed to be developed being so considerable.
  Mucous globules,  then, are to be regarded as young epithelial scales,
as are also the colourless globules of the blood; they both have a like
structure and a corresponding function to perform, but they have a
different origin; thus, the mucous globules  are developed externally to
the lymphatics and blood-vessels,  while the colourless blood corpuscles
are formed within those vessels.
  The further consideration of the ulterior development of mucous
corpuscles,  or  young epithelial cells,  will come  more appropriately
under the head of Epithelium.
  Blood corpuscles  not unfrequently  occur mixed  up with mucous
globules, as in the mucus thrown off during  parturition (see Plate
XII. fig. 1), and as in the rust-coloured expectoration of Pneumonia.

                    THE MUCUS  OF  DIFFERENT  ORGANS.
  After the threefold division of mucus which we have given, founded
upon the structure of the membranes by which it is secreted, and
after the description which has been entered upon of the peculiarities
appertaining to the  mucus  of each  of those divisions, it will  be
unnecessary to enlarge at any length  upon the characters presented
by  the  mucus secreted by the  membrane  which  belongs to  each
particular  organ  or  part; it will be sufficient just to  enumerate the
names of the membranes by which each description of mucus is fur-
nished, and to point out any peculiarities which the mucous secretion
of any particular organ may present: this  having been done, and the
distinctive  characters  of the three  forms of mucus  having  been 
180
ORGANIZED FLUIDS.
recalled to mind, we shall then be in a position to assign to the mucus
of each locality its principal characteristics.
  Thus,  the mucus furnished by the nasal  and bronchitic  mucous
membranes, and which may be called nasal and bronchitic mucus, as
also that of the digestive tube, from the pyloric orifice of the stomach
unto near the termination of the rectum (the  caecum alone excepted),
of the  urethra,  prostatic gland,  vesiculae  seminales and the  uterus,
belongs to the first division  of mucus, viz: that which is secreted by
the true mucous membranes.   (See Plate XII. fig. 3.)
  The mucus of the vagina presents the best example  of the mucus
of the second class, which is secreted by the false mucous membranes.
(See Plate XII. fig. 1.)
  Lastly.  The mucus of the mouth, rectum and bladder, appertains
to the third description of mucus, and which  is supplied by the mixed
mucous membranes.   (See  Plate XII. fig. 2.)

                Vaginal and Uterine Leucorrhea.
  One practical result arising from the discrimination of mucus into
different  kinds may here be alluded to; thus, by means of the differ-
ence in the microscopic characters  of the  mucus  secreted by the
uterus  and that furnished by the  vagina, it is in our power to decide,
in cases of leucorrheal discharge, whether  the  affection has  its seat
in the mucous membrane of the uterus or in that of the vagina.   The
mucous membrane of the uterus, as we have  seen, belongs to the
class of true mucous membranes;  that  of the  vagina, on the contrary,
to the false mucous membranes.   Now, if the leucorrhea be uterine,
the discharge will present the globules  characteristic of the secretion
produced by the class of true  mucous  membranes;  if,  on the other
hand, it be vaginal, the mucus will contain the epithelial scales which
belong to the  mucus of false mucous membranes; moreover, the
former mucus will be alkaline, and the latter  acid.

              Effect of Acid Mucus  on  the  Teeth.
  The degree of acidity presented by the mucus of the mouth varies
considerably, according to the  relative proportions of mucus and
saliva which exist in the mouth  at the time  at which the reaction  of
its secretions is tested, and which proportion differs both at differeiv
times of  the day and in different states of the  system, and especially
of the  stomach.   The  mucus of the  mouth  we know  to exhibit  ii
states  of health an  acid reaction, while the saliva, on the contrary, 
MUCUS.
181
manifests an alkaline  constitution; the tendency of these two fluids
is therefore to produce a neutral secretion, and this explanation will
account for the opposite results which have been obtained by different
observers.  The  best time to ascertain the chemical reaction  of the
buccal mucus is in the morning, when there is an accumulation of it
on the tongue and around the gums; and the best  method of deter-
mining the acid or alkaline qualities of the saliva, is first to  scrape
the tongue well, and as far as possible  free the mouth of mucus, and
then proceed to test the saliva as it issues from the orifices of its ducts.
  A highly acid condition of the  mucus of the  mouth is assuredly
productive of injurious effects  upon the teeth.   Although this state
of the buccal mucus cannot be regarded as giving rise to the peculiar
caries  to  which the teeth are so  remarkably liable; nevertheless, it
cannot be doubted that it predisposes the teeth to this affection, and
that it hastens greatly the  progress of the decay when once this has
commenced.  To correct the condition of the stomach, if it be faulty,
the internal administration of alkalies should be had recourse to;  and
to remedy the  local acidity, tooth powders, composed principally  of
of some alkaline carbonate, should be employed.

                   The  Vaginal  Tricho-Monas.
  M. Donn£ has discovered in the vaginal mucus of women labouring
under discharges, either specific or  otherwise, a new species of human
parasite  belonging  to  the  order  of Infusoriae.   This  animalcule,
owing  to its resemblance to the spherical mucous globules with which
it is constantly associated, is  with difficulty  discoverable by those
who are not practically familiar with its appearance, and the mode of
detecting  it.   Thus, it presents nearly the same size, form, granular
structure, and colour as the mucous corpuscles alluded to; it is to be
distinguished from these, however, by the  independent locomotive
power  which  it possesses, the  movements which it performs being
produced  principally by means of a long lash or cilium with  which
its anterior extremity is furnished,  and the presence of which causes
the animal to lose somewhat its circular  contour, and assume a form
approaching  the oval; in addition to this long  cilium, three or four
other shorter cilia exist, which surround the mouth, and which  can
only be satisfactorily detected when the motions of the animalcule
become somewhat retarded.  (See Plate  XII. fig. 6.)  In order that
it may be seen alive and in active movement, it is necessary that the
mucus containing it should be submitted to examination as soon as 
182
ORGANIZED  FLUIDS.
possible after its removal from the vagina; the  animal once dead, it
is then almost impossible to distinguish it from a mucous corpuscle.
  M. Donne, on first discovering this parasite, was for some time in
doubt as to whether its occurrence was to be regarded as having any
connexion with the specific disorders of which the vagina is sometimes
the seat, and he has at length arrived at the conclusion that no such
relation as that suspected  exists, and that any inflammation, specific
or  otherwise,  sufficiently  active to give rise  to  the secretion of
puriform matter, may be accompanied by the  tricho-monas which has
been described.
  In addition to the positive  characters which have been indicated,
denoting the presence of this animalcule, there is another altogether
indirect which serves to signalize its existence in the vaginal mucus,
and this is the presence in it of air-bubbles, which are not encountered
in healthy mucus.

                        Vaginal Vibrios.
  The tricho-monas is  not the  only animalcule which lives in the
mucus of the  vagina; there are frequently  met with in it minute
vibrios, which, to be satisfactorily seen, require to  be viewed with a
magnifying power of not less than the Ti? of an inch.
  In the same manner as the tricho-monas, they always occur  in
connexion with pus globules; they are not, however, any more than
the  tricho-monas, to be regarded as indicating the existence of specific
or venereal  affections, although  they are not unfrequently met with
in the secretion of chancres of an undoubtedly specific character. 
PUS.
183
                         ART.  IV.  PUS.

                         GENERAL CHARACTERS.
   Healthy, phlegmonous, or laudable  pus, is  a fluid of the colour
and consistence of cream, readily miscible with water, in which after
a time it sinks;  it does not admit of being drawn out into threads,
and exhibits usually an alkaline, though sometimes an  acid, reaction.
   Like mucus, which  it resembles so closely, pus is made  up of two
constituents, the one fluid, the other solid; these, if allowed to stand
at rest for a time, will undergo  a spontaneous  separation  from each
other, the corpuscles subsiding to the bottom, and the fluid or serum
floating  upon  the top; this also will be frequently observed to be
covered with  a delicate  film  composed  of oil  globules.  The fluid
portion of pus, as of mucus,  is probably the  only  essential, as it
certainly is its  only distinctive constituent; but while  the  latter is
sometimes free from globules, the former is never  without a greater
or less amount of corpuscles, on the presence and numbers of which
its opacity,  its colour,  and its consistence mainly depend.
   The general characters of pus, however, undergo many changes in
disease; thus its  consistence,  colour, smell, and all  other sensible
qualities, vary greatly  in pathological conditions.

               IDENTITY OF THE PUS AND MUCOUS CORPUSCLE.
   The globules of pus resemble in all essential particulars those of
true mucus, the characters of  which have been already described;
thus, they present the  same form, the  same constitution, and they
comport themselves in a manner almost identical  with  chemical
reagents.   (See Plate XI. fig. 1, and Plate XIII. fig.  1.)
   In one respect only can a difference in the effect of reagents on the
pus and mucous corpuscles be detected; this difference is, however,
one of  degree, and  not of kind; thus, the mucous corpuscle is less
readily acted upon by  the acids  than the  pus globule; in the former,
a solution of acetic acid, not too concentrated, will often disclose  but
a single, although large, nucleus; while the same solution applied to the
latter, will  render apparent seldom less  than three or four nucleoli.
(See Plate XIII. fig. 2.)  This is, however, by  no means a constant
result, and the  effect of the application  of strong  acetic acid to  the
mucous globule is  almost invariably to render apparent three or four 
184
ORGANIZED  FLUIDS.
nucleoli; so that,  from the  circumstance of the number ot nuclei
disclosed by acetic acid, no  opinion  can be formed as to the nature
of the corpuscle, whether it be a mucous or a pus corpuscle.   Of the
accuracy  of this view, notwithstanding that a contrary opinion is
held by many  observers, not  a doubt can be entertained.
   It is not in every example  of pus that we find the well-formed and
spherical corpuscles, which characterize healthy and normal pus.   In
the pus which has been long  secreted, as in that of old abscesses, we
find but few corpuscles, the majority being broken up and reduced to
their elementary particles.   (See Plate XIII. fig. 5.)
'   The best examples  of pus corpuscles are seen in pus which has
been  recently  secreted,  as  in  that  just  formed  on  some  healthy
granulating surface.   (See Plate XIII. fig. 1.)
   When, therefore,' pus and  mucous  globules are spoken of, it is not
to be understood that  these  terms indicate two  distinct  structures,
but merely the occurrence  of the  same solid  element in  two fluids,
which, although usually presenting some points of difference, are in
all probability  not essentially distinct.

          THE  NATURE, ORIGIN, AND  FORMATION OF PUS CORPUSCLES.
   In having indicated the nature of mucous globules, we  have also,
to a very great extent, pointed out that of pus corpuscles, seeing that
the corpuscles of both  have an organization precisely similar.
   One of  the earliest opinions  formed in reference to the nature of
pus was, that it was constituted  of  blood  deprived  of its colouring
matter, a view  which was  entertained even before the discovery of
the blood corpuscles  themselves.
   Subsequently to the  period of the detection  of the red  corpuscles ■
in the  blood, many observers have  conceived that pus consists of
these corpuscles altered merely in colour.
   A third  opinion in reference to the formation of pus and mucous
globules is  that of Vogel, who maintained that they arose out of a
transformation of the epithelium, the nuclei of which constituted the
corpuscles.  This view, although not without ingenuity, has but little
even of probability to  recommend it, and it will be perceived  that it
is the very reverse opinion to that which is  maintained in these pages,
and which  is, that the  epithelium  is itself derived from mucous and
pus globules.
   We  have already,  under the head  of Mucus,  adverted to the
opinion of Addison, that mucous and pus globules are altered colour- 
PUS.
1S5
less blood corpuscles, an opinion which we have also endeavoured to
refute, principally by reference to the impossibility, save from lesion,
of the escape of the white corpuscles from their containing vessels.
   Reference has  also been made to the view entertained by Henle
respecting the nature of pus corpuscles, who  says of them that they
are nothing else  than  elementary cells in process of being trans-
formed into those of the tissue,  which  the organism  regenerates in
the injured part.
   I  also  agree  with Henle  in considering pus  corpuscles to  be
elementary cells, but I differ from  him in not  regarding  them  as
representing the cells of the tissue in which the pus is formed.
   Pus corpuscles I conceive to be identical with mucous corpuscles.
and these again are to be regarded as representing an early stage in
the development of epithelial scales.
   Further, it is here supposed that  the formation of pus  is to  be
viewed in the light of a salutary  process, and  as indicating the effort
on the part of the organism, where suppuration occurs as the result of
lesion of any kind, to  repair the mischief sustained, and which it
does by the elaboration of pus corpuscles capable of being transformed
into a protecting epithelium.
   In  support of this view, reference may be made to the fact that it is
by no means uncommon to encounter epithelial scales mixed up  with
the ordinary pus  corpuscles contained within the  cavity of an
abscess, or covering the surface of an old ulcer.
   But, it may be asked, how happens it  then  that all pus corpuscles
do not become converted  into epithelial scales, and that so many of
them  are discharged or thrown off from the system without attaining
to the higher degree of development of which they are stated  to be
susceptible?
   This arrest of development  doubtless arises from the rapidity with
which the pus corpuscles  are  formed, and which is indicative of the
strength of the Vis medicatrix naturce, the result of which is that the
earlier formed  corpuscles  become  displaced  by  the  more  recently
developed ones, and are thus removed without the sphere of  growth,
in consequence of which they perish.
  Having thus considered the  nature  of  pus corpuscles, we will next
endeavour to form some opinion in reference to their origin and mode
of formation; in these  respects  also an  essential  correspondence
doubtless exists between pus and mucous globules.
  Mandl attributes to the pus globule  the same mode of formation 
166
ORGANIZED FLUIDS.
which he has described as  belonging  to  the  white corpuscles of the
blood, that is, that they are formed  external to  the vessels  by the
aggregation of molecules precipitated from  the  fibrin, and  hence
Mandl terms both the white and pus corpuscles " fibrinous globules."
  This view of the formation of pus  corpuscles is supported also by
the observations of Vogel (already cited) made upon abraded surfaces.
  Mandl, therefore, is  most probably  correct in his opinion as to the
mode of formation of pus corpuscles,  viz: by precipitation; but it is
at the same time almost certain.that they are not constituted of fibrin,
as supposed  by that micrographer: this may be  inferred  from  the
different  manner  in  which  acetic acid  acts  upon  fibrin and pus
corpuscles;  thus,  the former swells up, and is rendered soft and friable
by its application,  while the latter under its influence become smaller,
and their contained molecules more distinct.
  Donne dissents from Mandl's view altogether.   At page 191 of the
Cours de Microscopie,  M. Donne expresses himself as follows:—
"Thus I do  not  admit that  the globules of pus are formed  at  the
expense of the fibrin of the blood;  that they ought to be considered
as a sort of precipitate of the fibrinous part of the fluid blood;  and in
spite  of their analogy  of structure and  composition with  the white
globules of the blood, I nevertheless do not admit that they have any
thing  in common  in their  origin and in their  intimate  nature with
these  last.   I regard  the  globules of pus as a product of special
secretion direct from the pus  forming membrane."
  There appears to me to be much of  error in the preceding observa-
tions: there is doubtless very much in common between the white
corpuscles of the  blood and  pus globules, viz:  a common mode of
formation and a common function to perform.
  At  the same time it must be admitted, with  Donne, that the surface
or membrane, from which the pus proceeds, is also intimately associated
with the development of the pus corpuscles.

             DISTINCTIVE  CHARACTERS OF  MUCUS AND  PUS.
  We have now to ask ourselves the question, which doubtless many
have  applied to themselves  before, viz:  what  are the distinctive
characters between mucus and pus revealed to us by the  microscope,
and the satisfactory recognition of which  has been deemed to be of so
much importance ?
  To this inquiry no sufficient answer has as yet been returned: this
difficulty the microscope has failed to solve; and this, in all probability, 
PUS.
1S7
for the very adequate reason, that  between  the  fluids  in  which  a
distinction has been sought, no microscopic difference exists.   The
inquiry has been made on the false assumption  that mucus and pus
are really essentially distinct; and its importance has been magnified
by the idea that it would impart, as indeed it  undoubtedly would do,
if real, increased assistance  in the diagnosis of disease.
   Since, however, the establishment of the  fact that pus may be
formed independently of any appreciable structural lesion,  much of
the interest which was supposed to  attach  to this inquiry has  been
lost, and that which still appertains to it has been further lessened by
the demonstration at which  we have arrived by  means of the  micro-
scope, of the perfect identity of pus and mucous  corpuscles.
   Now,  the manifestation of this identity by the microscope is not
less a triumph of that instrument than if it had really proved that the
notion of physiologists was actually founded on  fact, and that there
does really exist a tangible difference in the microscopic characters
of the two fluids.
   Notwithstanding the  absence of any positive known  microscopic
character,  whereby at all times, and  in all conditions,  pus may be
discriminated from mucus, this want of knowledge, arising from the
very  sufficient fact to which allusion has  already been made, viz:
that no such character really exists,  the  two fluids under discussion
may frequently be distinguished, at a glance, by  certain outward and
physical  properties and appearances, and this is especially the case
when they occur without admixture  with each other.
   These differences in the outward  character of the two fluids are
not always, however, equal to their discrimination, and which  arises
from the fact, that they are all of them subject to the greatest possible
variation, so that there is not one which can be regarded as  truly
distinctive.  Thus, in morbid conditions, the  one fluid will pass by
insensible degrees into the other, or they will both be mingled together
in such proportions as to set at defiance all physical means employed
to distinguish them.
   But it  may be said that the chemist can at all  times distinguish pus
from mucus: there can be no doubt  but  that, when  all other  means
have failed, he can occasionally arrive at a tolerably accurate  con-
clusion, but it is conceived that  his powers in this respect are also
limited.
   Now,  the physical and chemical  difficulties  encountered in  the
endeavour  to discriminate pus from mucus arise in all probability, 
188
ORGANIZED  FLUIDS.
from the same cause which rendered it microscopically impossible so
to do, viz: that no constant or essential difference does really belong
to these fluids, whereby at all  times they may be characterized.
   Normal mucus and  pus may be contrasted as follows: Mucus is
a  thick,  tenacious, and  transparent  substance,  easily admitting  of
being drawn out into  threads, not readily miscible with water, in
which it floats, not so much from its less specific gravity as from the
circumstance of its great tenacity, allowing it to retain in its substance
numerous air globules, which thus render it specifically lighter than the
water: it  exhibits sometimes an acid, and sometimes an alkaline reac-
tion, according to the nature of the surface from which it proceeds;
and it contains imbedded in its substance solid particles of two forms,
globules and  scales:  the former are present in alkaline mucus, the
latter in that which manifests  an acid reaction.
   Pus, on the contrary, is a thick, opaque, somewhat oily substance,
which  does not admit of being drawn  out into threads, is readily
miscible with water, in which it sinks; its  chemical reaction varies,
being sometimes alkaline, at others acid: the solid particles which it
contains  are mostly of one kind, globules:  these are always very
abundant, and float freely in the fluid portion of the pus, while in that
of mucus  they are unable to do so on account of its tenacity.
   Healthy mucus and  pus, when  thus contrasted, may frequently be
distinguished from each  other, but it is  in unhealthy  conditions of
these two fluids, and especially  when  they occur mixed together in
variable proportions, that the  difficulty of  discrimination  is felt, and
that  the   want of a certain  and positive character, whereby the
diagnosis may be always established, is experienced.
   This mixture of mucus and pus may actually exist,  or it may not,
in cases of suspected phthisis, in which sputa are present.   Now, it is
in cases of this description that we recognise the importance of the
discrimination of these substances, and it  is precisely in  these  and
similar instances that the microscope utterly fails us, for the want of
an ascertained and tangible difference in  the two fluids submitted to
the test of its powers.
   Even the most marked physical qualities of pus, such as its opacity
and tenuity, may all be  effaced  by the employment of certain reagents,
and converted into those which are characteristic of mucus; thus,
pus, by the addition to it of liquor potasses or of ammonia, is rendered
transparent, and is transformed into a thick and tenacious  substance,
resembling mucus closely.  This  singular fact has been  noticed by 
PUS.
189
both Addison  and Donne, and on it the  former clever observer has
built a theory remarkable for its ingenuity, but which is here, never-
theless, deemed to be incorrect.
  The change of pus, from an opaque substance to a transparent one,
doubtless  results  from the solution  of the pus corpuscles, and to the
presence  of which  the  colour and opacity of pus is due; of the
increased density and tenacity of the pus thus treated, it is less easy
to afford a satisfactory explanation.
  Addison thus accounts for it: The mucus and pus globules, he says,
contain filaments  imbedded in a fluid; these the liquor potasses sets
free by dissolving the envelopes of the corpuscles, and it is upon these
filaments  that the  tenacity of mucus,  and  of pus  so  acted upon,
depends.   Mr. Addison,  however, carries his reasoning upon the  fact
of the conversion of pus  into a fibrillating substance similar to mucus
still further.  The  white corpuscles of the  blood, he states,  also
contain fibres, and that these corpuscles, immediately on their abstrac-
tion from the system, burst, giving issue to the contained filaments.
   These filaments  he conceives  to  constitute  the fibrin of the blood,
which he  declares does not exist in that fluid as fibrin, but is only
liberated from the corpuscles  after the  abstraction of the blood from
the system.
   The entire of this theory is here conceived to be erroneous, and
this for the following reasons:
   1.  The existence  of such filaments in the white corpuscles has not
been  proved.
  2.  The  bursting of these corpuscles, referred to by Mr. Addison,
is an  occurrence which  is rarely, if ever, seen  to  take place while
they remain imbedded in the liquor  sanguinis.
  3.  The actual consolidation of the fluid fibrin may be witnessed to
occur on the field  by the microscope in a drop of blood, and wholly
independent of any rupture of the  white corpuscles, which remain
without appreciable alteration.
  There is some  consolation,  however, in knowing that this inquiry
is not of so much importance as it  would appear; for even were we
able to make the  distinction which  has  been the subject of  so many
anxious thoughts, and decide that pus did exist in the sputa, yet this
fact, viewed separately, would not prove that disease of the lungs did
really exist, since it is ascertained that pus may be  formed without
any structural lesion; and, further, if lesion  were really  present, it
would not necessarily follow that this had its  seat in the cells of the 
190
ORGANIZED  FLUIDS.
lungs, for it might be situated either in the bronchi or larynx.  Thus,
even in this supposed case, the diagnosis would be subject to consider-
able uncertainty.
  Various  opinions  have been  expressed  by different observers in
favour of the possibility of distinguishing pus from mucus.  To some
of these we will now refer.
  There is always met with in pus, in greater or less quantity, globules
of oil; the presence of these was conceived by Gueterboch to afford
a sign, absolutely distinctive, between  pus and mucus;  that they are
not so, however,  is proved by the  fact  that similar globules are
occasionally encountered in normal mucus.
  Weber conceived the idea that the fluids might be distinguished by
the size of the globules contained in them, the pus globule being twice
as large as that of mucus: this  character  is likewise  too uncertain,
and too variable for the purposes of discrimination.
  Lastly, Gruithuisen  indicated, in  solutions of pus and  mucus in
water,  certain  animalculae;  those  generated  in  the  former being
different from those formed in the latter solution.   By means of these
he  asserted that pus might always be known  from mucus; but the
infusoria described by him are not confined to the fluids in question,
but are such as are formed  almost  indifferently in any solution of
animal matter.  It would appear, then, that up to the present time no
satisfactory and direct means of distinguishing  pus from mucus have
been detected, and this for the reason assigned, that the two fluids are
essentially identical.

          DISTINCTIONS BETWEEN CERTAIN FORMS OF MUCUS AND PUS.
  Although it  is impossible to discriminate between true mucus and
pus by  means  of the microscope  in  a positive manner, we are yet
enabled to distinguish with that instrument false mucus  from pus,
because in  this mucus the corpuscles exist in their fully  developed
form of tesselate epithelium.  Now, this power of discrimination is
not without importance, as will be perceived immediately.
  Many persons on arising in the morning  are in the habit of  expec-
torating more  or  less  of a substance  bearing  much resemblance to
pus.  This habitual occurrence is not  unfrequently a source of much
uneasiness, not merely to the person the  subject of it, but also to his
medical adviser whom he is led to consult upon it.
  Now, in such cases as these, it is often in our power to  dispel the
anxiety of our patient and our own  at the  same time; for the  solid 
PUS.
191
constituents of such  sputa  are frequently found  to  consist  almost
entirely of epithelial  cells, in which  case  we may safely pronounce
that they are not purulent; if, on the contrary, the  sputa contain only
globules, the evidence which this fact would furnish, although appar-
ently, and indeed most probably, unfavourable, would still be but of a
doubtful nature.
  Again, the microscope  will frequently determine the nature of a
suspected  fluid, by indicating in it the existence of shreds of cellular
tissue, muscular fibrillae, and a variety of other organisms which enter
into the formation of the  human body; and by the presence of one
or more of which, not merely the nature of the puriform matter may
be  ascertained, but also  the locality  from which  the  pus had itself
proceeded.

                    DETECTION OF PUS IN THE BLOOD.
   From what has been said in reference to the structural identity ot
the white corpuscle of the blood with that  of mucus and pus,  we  are
prepared  for  the  announcement  that  no  known characters exist
whereby the presence of  pus in  the blood may be established by the
microscopic examination of that fluid.
   That the elements  of pus in some cases are really present in the
blood, circulating with it, scarcely admits of a single doubt, since it
is  not  unfrequently met with in situations, such as on the  lining
membranes of the  vessels,  where  it is utterly impossible  for it to
remain without some portion of it becoming commingled with the blood.
   The  same  fact is  also proved by the  spontaneous absorption ot
large collections of matter,  an  occurrence  which is not unfrequently
witnessed, and which is  only to be accounted for on the  assumption
that  the  elements  of pus are again absorbed  into the  blood from
which originally they were  derived.
   There  can  scarcely be a question, then,  that pus  is occasionally
contained  in  the living blood, although   we possess  only  indirect
means  of establishing this  fact; and according to the  views here
entertained, it may be present in the  blood in two ways:  thus, as we
have seen, it may be  formed in the  blood-vessels themselves, or it
may  be formed without those vessels, and  again reabsorbed into the
blood from which in every case it almost immediately proceeds.
   But pus, as  we know, is composed of two elements, the one fluid,
the other  solid, the globules.   Now, we must not expect to see  pus
circulating in  the blood as pus, although that liquid may contain all 
192
ORGANIZED FLUIDS.
the elements of pus: the fluid portion of course, as soon as it enters
the circulation, is dissipated, the solid alone remaining, and this  does
not constitute pus, but is  only  one element in  the constitution of
that fluid.
  In certain states  of disease,  the presence in  the vessels of  an
unusual number of white  corpuscles has been observed;  now  it is
but little  probable, that these are derived from  the reabsorption of
pus, which had been previously formed  without  those  vessels;  it is
more natural, and  more consonant with known facts, to suppose, that
this accumulation is to be regarded as an indication that the disposi-
tion to  the formation  of pus, on  the  part  of the blood and of the
system,  exists to an unusual extent, and that such a condition of the
vital fluid always precedes sudden and extensive purulent collections.
  Except in  the  case of the  formation  of pus  in the  blood-vessels
themselves, it is scarcely possible to suppose that the pus corpuscles
are taken bodily  into  the circulation again; but it would rather
appear, from the condition of pus in most abscesses, that the corpuscles
become disintegrated and  reduced to their elementary particles, and
that thus they enter the circulation again in a fluid state.
  The artificial admixture of pus with  the  blood  immediately  after
its escape from a vein, and before its coagulation has commenced, is
productive of somewhat singular results.   The clot formed in blood,
which has been mixed with one quarter part of its own quantity of
pus, is soft, diffluent, and dark coloured, sometimes  almost livid, and
the red corpuscles are found to be wrinkled and deformed, part of
their  colouring  matter  having  escaped  from  them  and  passed
into the serum.
  These changes ensue in  from  twenty-four to forty-eight hours, and
possibly result from the state of decomposition in which the pus  itself
might have been when introduced into the blood, and which condition
it communicated to the mass of  the blood itself.

                            FALSE PUS.
   There are many substances and fluids having resemblance to pus
which  are not really purulent;  thus,  softened clots of fibrin, which
are so frequently encountered, especially in phlebitis, bear the closest
possible similitude to true pus in general appearance, and yet in  their
intimate  structure  they  are totally  dissimilar, as may be clearly
determined by means of the microscope.
   If a portion of softened fibrin be examined microscopically, it will 
PUS.
193
be found  to be made  up of a granular material, from  which pus
corpuscles, or corpuscles similar  to  them, are either entirely absent,
or in which they occur  but in very small numbers.  Now, with true
pus,  the reverse is the case; the corpuscles  are  its chief and most
conspicuous element.
   It is only by means of the microscope that the nature of softened
fibrin can be ascertained;  until within the last few years it has always
been mistaken  for true  pus, and  the occurrence  of masses of fibrin
thus  altered in the  blood-vessels has led to the opinion  that the
formation of pus in them is not an unfrequent event.
   On the  other hand, fluids are sometimes  met with which look very
unlike proper  pus, and which are yet found on  examination to  be
veritable pus.   These facts show the necessity of a careful microscopic
examination in all important and doubtful cases.

                        METASTATIC ABSCESSES.
   Another  notion, the erroneousness of which  has  been  rendered
manifest by means of the microscope, is that which has been  enter-
tained in reference to the removal of an abscess seated in one part of
the body, and its subsequent deposition in another situation.
   The  knowledge of the existence  of pus corpuscles in the fluid of
abscesses, and  the  fact that no channels exist by which they can be
conveyed bodily from one part of the system to another, clearly show
that  any  such translation  of  the  matter of  an abscess  as that
presumed is an occurrence beyond the range of possibility.
   Abscesses may  indeed be  reabsorbed into the system, as daily
observation teaches us  to be the case, and other purulent depositions
take place subsequently to the resorption of the  matter of the first
abscess; but the elements of pus, and assuredly its solid constituents,
are not carried into  the  constitution bodily and  without alteration;
the corpuscles  doubtless become  disaggregated, and in all probability
reduced to a fluid state previous to  absorption, so that it cannot be
the  same  purulent  matter which constitutes the pus  of supposed
metastatic abscess.
   The  simultaneous  or   consecutive  occurrence of abscesses  in
different parts of the body, may be satisfactorily explained by reference
to the condition of the  system, or perhaps  more  immediately  of the
blood itself, which is evidently charged with purulent  matter,  and of
which it relieves itself by the formation of abscesses.
                           13 
194
ORGANIZED  FLUIDS.
                          VENEREAL VIBRIOS.
   M.  Donne  has  discovered  in the pus  of syphilitic  primitive
 ulcerations, and of chancres which have not been treated with topical
 applications, numerous  vibrios  of excessive  tenuity.  (See  Plate
 XIII. fig.  6.)
   These  vibrios  are  not  encountered in  the  pus  of secondary
 chancres,  nor  even  in  that of  buboes,  which,  according  to  the
 experiments of M. Ricord, is capable  of giving origin to a chancre
 by inoculation.
   Neither are they  to be  met  with  in the  pus proceeding from
 wounds, nor in foetid pus altered by the contact of the air.
   Again, in the instances  in which suppuration has been artificially
 excited around the edge  of the glans penis, the ordinary situation of
 primary syphilitic ulcerations, the  vibrios  are invariably found to be
 wanting in the discharge thus created.   This experiment proves that
 locality has nothing to do with the development of the vibrios.
   Finally,  if inoculation be practised with  the  pus  of  a  chancre
 containing the vibrios, the  matter  of the pustule  resulting from  the
inoculation will also be found to contain the animalcules.
   Now, the inference  to be deduced from these  several facts and
experiments is, that  if  the vibrios in  question be  not  intimately
connected with the propagation of the syphilitic virus, that the matter
of syphilis is at least peculiarly fitted for their development.
   It  is probable  that the presence of  these  vibrios accounts, in a
great measure,  for  the beneficial effects  of topical  applications,
which act by killing the animalcules. 
MILK.
195
                        ART.  V. —MILK,

  The general aspect and qualities of milk are known to all; they
need not therefore be here detailed.
  Healthy and fresh milk, when submitted to the action of test paper,
exhibits an alkaline reaction: in states of disease, however,  and some
time  after its  removal  from  the  mammary  gland, it frequently
manifests more or less of an acid reaction.
  Like  the other fluids  which have as yet been described in  this
work, milk is made up of two distinct elements, the one  fluid, the
serum—the other solid,  the  globules; these, a few hours  after its
abstraction from the system,  and when left at rest, undergo to a
certain  extent  a spontaneous  separation from  each other, the larger
globules, ascending to the  surface, forming a scum or cream, while
the smaller remain diffused through the subjacent serum.
  The  following analyses  will  serve  to give  an idea  of  the
composition of milk.
  The relative proportions of the organic constituents of human
milk are thus estimated by  Simon:
                      88' 06 water.
                      3 • 70 caseine.
                      4 • 54 sugar.
                      3 • 40 butter.
                      0 • 30 salts, extractives, &c.
  The inorganic components  of the  milk  of the cow are computed
as follows by Haidlen:
           Chloride of sodium       -      - 0 • 024.
           Chloride of potassium    -      - 0 • 144.
           Soda      -      -       -      -0-042.
           Phosphate of  lime        -      - 0#231.
           Phosphate of  magnesia   -      - 0" 042.
           Phosphate of the peroxide of iron - 0*007.
  From the above brief sketch of the constitution of the milk, it  will
be seen  that  a very close  analogy exists  between that fluid and the
blood: like it, the milk is made up of two  parts—the one solid, the
other liquid;  like  it,  too,  it  contains all the elements  requisite for
nourishment and development, it serving for both during a very long
period of the  life of the human species. 
196
ORGANIZED  FLUIDS.
                       THE SERUM OF THE MILK.
 ' The separation of the serum and the globules, accomplished in an
imperfect manner  naturally,  is more completely effected  artificially
by filtration; the  serum, by means of the ordinary filtering paper,
may be obtained transparent and colourless, almost free from globules,
these being for the most part retained upon the filter.
  It may, however, be observed,  that the  first portions of serum
which  pass through the paper will be more or less coloured in conse-
quence of their containing a certain number of the  smaller globules,
which  had  escaped through the  interstices . of the  paper;  these
coloured and semi-opaque portions of serum should be rejected.
  The serum contains dissolved in it  the sugar, and  the principal
portion of the cheese of milk, as  well  as certain salts,  the principal
of which are pointed out in the analysis of Haidlen.
  The cheese or caseine is an animal principle, which in its proper-
ties  approaches closely fibrin: it is precipitated by the mineral, the
acetic, and the lactic acids.
  Although the greater portion of the  caseine exists in the milk in a
fluid condition, M. Quevenne appears  to  have established the fact,
that  it  is also present in a solid  state in the form of globules, these
being exceedingly  small, and refracting but slightly the  light; the
same globules  may  also be detected in recently precipitated cheese.
(See Plate XV. fig. 5.)
  M. Donne has shown that these  cheese globules may be demon-
strated by the process of filtration; thus, the first few  drops of the
milk of the  cow, the ass, or  the  goat, which pass through the filter,
and which are generally white and  opaque, being rejected, and the
second portion of filtered milk being preserved, and allowed to remain
undisturbed for a few minutes, it will be seen to separate into two
parts,  the inferior  of  which is  clear  and  transparent,  while  the
superior  is somewhat  opaque.  Now,  if a drop of  the  fluid of this
inferior layer be examined  with the microscope, it will be found to
contain an innumerable quantity of globules of exceeding minuteness,
and  refracting the light but  feebly, as well as occasionally  other
globules  more rare, larger, and refracting the light very strongly; the
former are the  cheese globules, and the latter the proper milk globules. 
MILK.
197
                             THE  GLOBULES.
   It is to the presence of the globles which occur in such vast quan-
 tities in each drop of healthy milk that the colour and opacity of that
 fluid" is due.*
   These globules are of perfect rotundity, their surface being smooth,
 presenting a pearly aspect, and refracting the light strongly;  the cir-
 cumference of each globule is dark and the centre light:  the globules
 vary greatly in size; the  smallest, which  are in  active  molecular
 movement, being  reduced to  mere  points,  and  not exceeding the
 nlo o °f an inch, the largest frequently attaining the -$ oVo of an inch,
 and the medium size ranging between the 4 0V0 of an inch in diameter
 and the 4jVo-   (See Plate XIV. fig. 1.)  In milk which is  healthy,
 the  globules float freely in the serum, and do not adhere to each other.
   Such is the  form, appearance,  and variety of size exhibited by the
 milk globule;  much difference of opinion has existed in reference
 to its organization, some observers conceding to  it a very complex
 structure, others denying it even the most simple organization.
   Some of the  more remarkable of the opinions entertained by the
 more noted investigators may here be referred to.
   According to Turpin, "the structure of the milk globule  consists
 of two spherical vesicles, fitting the one into the other, and enclosing
 in their interior very fine  globules and  buttery oil."f
   Mandl says, " the globules  of milk ought then to be considered  as
 organized corpuscles, composed of a membrane probably formed  of
 cheese, and of contents which constitute the butter." J
   Henle writes, the  globules of  milk  "are  not simple molecules  of
 grease,  and  have  an independent  membrane surrounding  them ;"§
 this  he elsewhere states to be probably composed of caseine, in which
 respect there is an agreement of opinion between Henle and Mandl.
   The complex structure ascribed to the milk globule by Turpin it is
 altogether impossible to demonstrate; and the experiments and obser-
 vations which have hitherto been  made in reference to its constitution

  * Leeuwenhoek first clearly indicated  the existence of these globules in  the milk
in the following terms: " Vidi multos globulos, similes sextae parti globuli sanguinei;
et etiam alios, quorum bini terni aut quaterni se invicem modo attingebant, fundum
versus descendere; et  multos variae magnitudinis globulos in superficie fluitantes,
inter quos posteriores adipem sive butyrum esse judicabam."
  t Annates des Sciences Naturelles.       ■           \ Anal. Micros, p. 53.
  J Anal. Gen. t. vii. p. 522. 
198
ORGANIZED  FLUIDS.
 are entirely opposed to his view, which may safely, therefore, be con-
 sidered to be incorrect.
   Mandl founded his belief of the existence of a distinct membrane
 enveloping the  globules mainly on the following observation: He
 remarked that if a little drop of milk be compressed strongly between
 two plates of glass, the upper  plate at the same time being drawn
 over the surface of the other in a straight line, the milk globules will
 be broken up by the compression, and drawn out into a certain form:
 if a magnifying-glass be applied to the globules thus compressed, they
 will be seen to present the appearance of long pale and straight lines,
 with smaller straight lines placed usually at right angles to the  larger
 ones.  "These little lines," he says, "are nothing else than the curled
 membranes of the globules, the contents of which, the butter, consti-
 tuting the long streaks: we may easily convince ourselves of this  by
 adding a little water.  The streaks  disappear, and we see in their
 place oleaginous drops of different forms, while the little  membranes
 remain either attached to the glass or indifferently curved, swimming
 in the serum.   These  membranes are insoluble in ether, which dis-
 solves the drops."
   These observations  of Mandl, presuming for a  moment that they
 are  accurate in  every particular, are  yet insufficient to prove the
 existence of a distinct  membrane surrounding  the globules, although
 they certainly would be so, if correct, to establish the fact that  they
 are constituted of two  different substances, the one of which is soluble
 in ether and the other insoluble.  Had iodine been employed, and
 had it been imbibed by the supposed membrane, and turned of a deep
 brown, the reality of the existence of the membrane in question might
 have been considered as demonstrated: but we know that iodine does
 not affect the colour of the milk globule in  the least.
   I am far, however, from attaching the smallest importance to the
 experiment of Mandl, because I conceive that he has misinterpreted
 the appearances which he noticed.   The larger streaks are  not con-
 stituted of a single elongated  globule, but are made up by the  union
 of several milk  globules,  as  is  evident—first,  from  the size of the
 streaks, and, second, from the traces which they bear of such a com-
 position in themselves; as, for example, the occurrence of contractions
 at certain intervals, while the  smaller lines,  and which are most
 generally absent,  are formed usually by other globules of less size
joining at an angle the larger streaks.   The  solubility of  the one  in
 ether and the insolubility of the other in that reagent, I have not been
 able to observe. 
MILK.
199
  The opinion of Henle, that the milk globule is furnished with an
envelope, rests chiefly upon  the  manner in which acetic  acid  acts
upon it.
  Henle thus  describes the effects of the application of acetic acid:
  "Treated by dilute acetic acid, the globules of milk  undergo, little
by little, a remarkable change;  some of them become oval or take the
the form of a biscuit; upon others, appear gradually on one or many
points a smaller globule, which rests upon the  margin, and  increases
in an insensible manner."   *   *   *  "If more acetic acid  be added,
the milk globules appear, as it were, melted down with smooth  but
irregular borders: they approach the one to the other, and unite into
large masses,  which resemble  perfectly melted  fat  which has run
along in an irregular manner.  When to  a drop of milk are added
two drops of concentrated acetic acid, and the mixture then placed
under the microscope, we no longer perceive any regular globule of
milk, or, at least, we  discover  but very few:  the most are reduced
into one or several irregular particles, which, with the naked  eye,
may be distinguished upon the surface of the drop, which otherwise
has become clear.   The same changes are produced in the space of
a few days, when the milk, abandoned to itself, becomes acid by the
metamorphosis of its sugar."*
  These ingenious  observations  of Henle, like  those  of Mandl, are
yet insufficient to demonstrate the existence of a  distinct and organ-
ized membrane surrounding the milk globule, although they would be
assuredly so, if correct, to render it quite certain that it is enveloped
with a coating of a  material very distinct from  fat, and probably of
the nature  suggested by Mandl and Henle
  Here, again, however, it becomes a question whether the appear-
ances noticed  by Henle have not been misinterpreted, and whether
the internal buttery substance does really protrude through  apertures
in the envelope of the globule occasioned by the action of acetic acid:
in the first place, it seems to me that the milk globules are too small to
allow of the determination of the point in  question with any degree
of certainty;  and, secondly, that in those instances in which  observers
might fancy that an escape of the included substance of the globule
through its envelope had really occurred,  such an appearance  is, in
all probability, due to the adhesion together and partial fusion of two
or more globules.  (See Plate XV. fig. 4.)
* Henle, Anat. Gen. p. 521, 522. 
200
ORGANIZED  FLUIDS.
   There  are  other  observers   again—as  Wagner,  Nasse,  and
Quevenne—who would deny to the milk globule all organization, and
who regard it as of  a perfectly homogeneous  nature.
   The  truth in this instance, as in so many  others, would appear to
lie in  the mean.  That  the milk globule is not provided  with a
distinct  and separate membrane, similar to that of  the mucous
corpuscle, is proved by the impossibility of demonstrating the existence
of any such  structure, as well  as by the absence  of a  double line
around  its margin, the non-effect  of iodine, and  the  coalition of the
globules resulting from pressure, first observed by Dujardin.
   That  it is not constituted  of  a single  perfectly  homogeneous
substance, is also demonstrated  by the  observations  of Mandl and
Henle, and  especially  by those of the  latter  observer on the  effects
produced by acetic acid.
   That the milk globule is  not  wholly  composed of fatty matter, is
shown by its insolubility in boiling water raised to a very high tempera-
ture, in  boiling  alcohol,  in  the  alkalies,  and by the effects  of the
application of acetic acid.  Ether  dissolves the  milk globules: their
solution, however, it does not entirely accomplish on its first applica-
tion, although the ether,  the moment it comes in contact with the
globules, causes  them to lose  their rotundity, to fall down,  and to run
together into masses  of various sizes, but most of which still present
a circular outline.
   If a drop of milk be examined  microscopically, after its treatment
by ether, a hasty observer might conclude, from noticing so many of
the circular masses alluded to, that the reagent had not exerted any
influence  on the milk globules,  and that these  masses  were the
unaltered globules.  This view,  however,  a  little reflection  would
soon show to be  incorrect;  for  many  of the circular bodies now
noticed on the field of the microscope are larger than even  the largest
milk globules, and all  of them are flat  and semi-fluid.   (See Plate
XV. fig. 3.)
   The  several  facts  now adduced, while they prove that the milk
globule is not organized in accordance with the interpretation of the
word organization usually given, yet seem sufficient  to establish the
fact  that  it  is composed  of  two  distinct organic products—the one
internal and fatty, and the other external, and  possessed of properties
distinct from fat.
   This explanation of the constitution of the milk globule serves to
explain also satisfactorily  the facts above alluded  to, viz:  the non- 
MILK.
201
action of boiling water, alcohol, and alkalies, all of which affect more
or less  fat, as also the slower operation of the ether: it also shows
why boiling  alcohol should immediately dissolve the milk globules,
to which a  little acetic acid had  been previously added, this latter
reagent first removing their outer coating, which is insoluble in alcohol.
   Between  the globules of the previously-described  fluids—those of
the lymph and chyle,  of the  blood, mucus and pus, and globules of
milk—no structural or functional relation whatever exists; the former
being  complex  and definite  organizations or cells,  and  the latter
constituted of two distinct  substances  indeed, yet want entirely the
attributes of cells, being destitute of nucleus and cell wall.
   It is of the globules just described  that the cream is constituted,
their  accumulation on the surface of the milk  being due to  their
lighter  specific gravity; it  is also  by their incorporation  with each
other, and which is effected by the  operation of churning, that butter
is formed.

                             COLOSTRUM.
   The milk which is secreted the first  few days  after child-birth has
been  denominated colostrum:  it  differs  very  considerably  from
ordinary milk,  being  of a  yellow  colour, of a viscous consistence,
and containing a very large proportion  of milk globules, which give
rise to the formation upon it of a thick layer of cream; when  treated
with ammonia, it becomes glairy and tenacious.
   Corresponding with the outward  characters of the colostrum, there
are others indicated by the microscope not less remarkable: thus, the
larger true milk  globules which occur in  it are but ill-defined, being
irregular in form  and size,  appearing as though they were but imper-
fectly  elaborated, and presenting rather  the aspect  of oil globules,
while the smaller ones  are like a fine powder  strewn through the
serum, and adhering to the  surface of the larger globules, which also,
in place of floating freely and separately in the serum, are agglomer-
ated together as if held in union  by some viscous  material.   (See
Plate  XIV. figs. 4 and 5.)
   But besides the state of the ordinary milk globules just described,
there  are found  in the colostrum peculiar corpuscles of a totally
distinct structure:  these were first discovered and described by M.
Donne, who has denominated them " Corps granuleux."
   These corpuscles are mostly  several times larger than the milk
globules, are  less regular  in form,  although usually more  or less 
202
ORGANIZED  FLUIDS.
spherical in outline, and present a uniformly molecular aspect and a
yellow coloration;  the edges of  the  corpuscles  sometimes  appear
smooth, as if possessed  of an envelope; at others, their margins are
rough, and convey the impression  that  they are destitute  of any
external covering.  See Plate XIV. figs. 3 and 4.)   Occasionally one
or more  milk or oil globules are imprisoned in the substance of the
corpuscles, which then occupy the  position,  although they  do  not
discharge the office, of a nucleus.
  Some  difference of opinion is entertained respecting their intimate
structure:  Gueterboch,  and  probably Donne,* conceive that they are
furnished with an investing membrane, and therefore  that they are
veritable cells, while Henlef regards them as masses or aggregations
of granules agglomerated together in  an amorphous and mucoid
substance ; an opinion in which I concur.
  Donne states that the colostrum corpuscles are soluble in ether, and
therefore that they are of  a  fatty nature:  the  fact of their solubility,
however, seems to me to be  difficult  to verify; and from observations
which I have made, I cannot help thinking that this point is scarcely
as yet established.  Certain  it is that corpuscles larger than mucous
globules,  and in every way  similar to the colostrum corpuscles, save
that traces of nuclei  may be detected in them, appear in colostrum
treated with ether.
  The " Corps granuleux " are insoluble in the alkalies, J are coloured
brown by iodine, and the substance which unites the granules is
dissolved by acetic acid.§
  The state  of  the milk  just described does not  continue without
alteration,  each  condition which has been alluded to undergoing a
daily modification:  thus the milk globules from day to day acquire
greater uniformity of size  and shape, they no longer adhere together,
but float  freely and singly  in the  serum, which does not become viscid
on the addition  of ammonia,  the  smaller dust-like globules also
altogether disappearing; at the same time the number of the colostrum
corpuscles diminishes  until  at length  none  exist.   (See  Plate
XIV. fig. 1.)
  These several changes are all  accomplished  in the course of a few
days, so that by the end of the twenty-fourth day, the  milk  has
usually entirely passed from the  condition of colostrum, and presents
only  its  ordinary characters.   The colostrum, however,  does  not
       * Cours de Microscopie, p. 401.    jAnal. Gen. t. vii. p. 525.
       J Donne, loc. cit. p. 401.          J Henle, loc. cit. t. vii. p. 525. 
MILK.
203
always pass through its various modifications in the time specified; it
may do so in either a shorter or a longer period  than that stated:
thus, the existence of the milk in the form  of colostrum can scarcely
be regarded  as affording any very certain test whereby the age of
the milk may be determined.
  The colostrum corpuscles would appear to be almost peculiar to
the human subject, for while their presence in the milk of woman is
almost constant, their occurrence in that of animals—as the cow, the
ass, and the goat—is rare and exceptional.
  Professor Nasse states that they disappear sooner in women who have
borne many children than in those who have had  but a single  child.
  Mucous corpuscles are also occasionally encountered in the colos-
trum.   They are, however, neither very  generally present, nor do
they occur in any very great numbers.
  The colostrum, or first milk, is possessed of purgative qualities.

                 PATHOLOGICAL ALTERATIONS OF  THE MDLK.
      Persistence of this Fluid in the condition of Colostrum.
  It has been stated, that  usually by the end  of the  twenty-fourth
day after child-birth, and  frequently at a much  earlier period, the
colostrum  has lost all  its  distinctive  characters, and  the  milk  has
arrived at its perfect condition.
  This  transformation of the colostrum into fully-elaborated milk, it
has been observed, is not always effected in the time named: it may
be accomplished in either a shorter or a longer period;  thus, the milk
in some cases loses the chief characters  of colostrum in as short a
space of time as three or four days, while in others it retains them for
months after the birth of the child, and even until the end of lactation.
  This  persistence of the  milk  in the  state of colostrum may be
present without any suspicion  of its existence being entertained, the
milk exhibiting its ordinary outward appearances.
  It is, therefore, only  by means of the  microscope  that its true
condition  can be ascertained.   Examined with this instrument, the
characteristics of colostrum will be detected; thus, the globules which
do not float freely in the serum, and which are  large and  ill-formed,
will be seen to adhere together in groups, as though held in union by
some viscous substance, and intermixed with them will be noticed
numerous colostrum corpuscles.
  It cannot  be doubted but that such persistence of the milk  in the
form ui colostrum exerts a most injurious effect upon  the child: the 
 204                 ORGANIZED FLUIDS.

 colostrum is, as we  know, possessed of purgative  properties; these,
 during  the first days of the life of the  infant,  are necessary;  their
 continuance cannot  but impair its strength and health.

                    Recurrence of Colostrum.

   M. Donne has established the interesting fact that milk which has
 entirely lost the  character of colostrum, and which has reached its
 perfect  maturity, may again pass into the state of colostrum at any
 period during the course of lactation.
   Thus, the milk which had at one time  presented the constitution of
 perfectly formed milk has been seen by M. Donne to acquire gradually
 that which is indicative of the colostrum, it becoming viscous, and
 the globules contained in it, instead of  floating freely  and singly in
 the serum, uniting  with  each  other,  forming irregular masses, the
 granular and mucous corpuscles at the same  time being present in it
 in considerable quantities.
   In  the  instances  in  which  the recurrence  has  been observed,
 engorgement of  one or both of  the mamary glands  has usually
 preceded it.
   When but one gland is affected, the milk of that gland only presents
 the characters  of colostrum, that of the opposite  side retaining  its
 usual properties and  constitution.
   The recurrence of the colostrum would  appear to depend,  as a
 cause, either upon lesion of  the mammary gland, or upon a deranged
 or vitiated condition  of the health.

  Influence of prolonged Retention of the Milk on its Constitution.

   M. Peligot has made the observation, important in a practical point
of view, that the milk which has been allowed to remain  for a long
 time  in the breast  becomes thin  and   watery, an effect which  is
 contrary to that which  occurs in reference to most other  secretions
of the economy, the urine and the bile, the density of which  is
heightened by retention.
   Thus, if the  milk  abstracted at one time, and which has been lono-
secreted, be divided into three parts, each being received successively
into a distinct vessel, the first milk will seem to be  poor and watery,
the second more rich, and the third the  most so of the  entire.   The
first portion is to be regarded as that which has been longest formed,
and the  third as the most recently Secreted. 
MILK.
205
  The knowledge of the above fact leads to one practical result in
the  case in which the milk is too rich for the digestive powers of the
child ;  thus by allowing such milk to remain for a longer period than
usual in the breast, a fluid of lighter quality and less abounding with
nutritive principles will be obtained.
  A second effect of prolonged retention or engorgement of the milk
in the breast is  to  occasion the aggregation of the  globules into
masses.  (See Plate  XIV. fig. 6.)

                   Pus and Blood in the Milk.
  Having now described those constituents by the  combination of
which  milk is formed, as well as the  several conditions  in which
these  may be encountered,  we may next  refer  to those  structures
which  occasionally occur in milk  as  the result  of disease.
  Thus,  the  corpuscles  of  both  pus and  the blood are  sometimes
encountered  in the milk, those of the former fluid occurring much
more frequently than those of the latter.
  The puriform  matter  which issues  from  the  breast in cases of
abscess of that gland  is  made up of a mixture of pus  and milk glo-
bules, with occasionally blood discs.   (See Plate XV. fig.  1.)
  But  both pus and blood corpuscles, the latter very rarely, may be
contained in the milk which issues from the breast through  its natural
channels.
  I was so fortunate as to meet wilh an excellent example of blood
in the  milk, the occurrence of which is so rare that Donne, at the
period  of the publication of the " Cours de Microscopie," and  with
all his researches on the milk, had  never encountered a single instance
of such pathological alteration in the human subject.   The case in
which  this occurred was  that of a young woman confined of her first
child;  the milk not appearing at the usual  time, the  friends became
anxious, and  one of them, more officious and more ignorant than the
rest, had the nipples drawn with such vigour and effect as to cause
the  extraction of a liquid half blood and half milk.   (Plate XV. fig. 2.)
The occurrence of blood corpuscles in the milk can only  take place
as the consequence of a rupture of some of the smaller blood vessels
which  are distributed through the mammary gland.
  The above facts clearly show the impropriety of applying an infant
to the breast  in cases of inflammation and suppuration in that organ.
  Not the least difficulty need be  experienced  in the detection of pus
and blood corpuscles in  the milk, their form  and structure being so 
206
ORGANIZED  FLUIDS.
totally dissimilar to those of the proper milk  globules.  Reagents
also affect the different  kinds of corpuscles differently.  Thus,  the
milk globules  are soluble in ether, which does not materially affect
the pus and  blood  corpuscles, the latter of which is  dissolved by
acetic acid, and the former only  by the caustic alkalies.

                 The Milk of Syphilitic Women.
  M. Donne  has made repeated attempts to discover in the milk of
women  labouring under syphilis, in  different forms, some element
which would account for the transmission of the affection from  the
mother  to the infant.  These endeavours  were, however, entirely
fruitless; nor  is this result other than what might have been antici-
pated, for it is scarcely to be supposed that  the venereal virus  exists
any where in a tangible form; and if it really does so, it would still
be a matter of impossibility to point out  the channels by which any
solid matter could make its way  through the system and  mingle with
the secretion  of the mammary gland.

The Milk of Women in the Case of the premature Return of their
                        Natural Epochs.
  The milk of women in whom the natural periods  have returned
during the course of lactation, has likewise been carefully examined.
Except in a single instance, however, it has not been found to present
any thing remarkable in its characters.   In the  case referred to, it
had degenerated to  the  condition of colostrum,  and  contained the
granular colostrum corpuscles.

                    THE MILK OF  UNMARRIED WOMEN.
  The breasts of many  women who have not been married are fre-
quently  found to contain an abundance of  milk,  and  from those of
most, more or less of a milky fluid can be obtained.
  This milk exhibits all the characters of colostrum, containing even
the peculiar corpuscles which distinguish that condition of the milk;
it is therefore, like the first milk, to be regarded as  an  imperfectly
elaborated substance.

              THE MILK  OF WOMEN  PREVIOUS TO CONFINEMENT.
  The breasts of most women during the last few weeks  of gestation
contain  more or less  milk, which  also presents all the characters of
colostrum. 
MILK.
207
   The  quantity of milk contained varies greatly; in some cases  a
few drops  of a milk-like fluid  only can be obtained;  in others it is
more abundant; and again, in other instances, it is still more plentiful,
and rich in quality.
   The question may be asked, does there exist any relation between
the quantity and condition of the milk before confinement, and its
state when it has arrived at perfection after this event has occurred ?
In other terms, can one pronounce, by the milk in the breasts, before-
hand, whether  a  woman will have  a sufficient  quantity of milk to
nourish her infant?
   This question, which so  often presents itself  to the consideration
of the" medical practitioner, M. Donne has discussed at some length,
and to it he replies thus :
   " The secretion  of the mammary gland," he  says, " is after con-
finement in constant relation with the state which it  presents during
gestation, so that it is possible to know in advance, by the observation
of  its characters during the  last months of pregnancy,  what its
condition will be when it  shall  have acquired all its  activity after
parturition."*  This  law, he states, is so general, that in  the  sixty
observations which he has  made on women of all ages  and  tempera-
ments, he has met with but two or three exceptions.
   Pregnant women Donne  divides into three  classes, founded upon
the characters  presented by the colostrum during the last months of
gestation:
   1st.  Those in whom the secretion is small, and the viscous  liquid
contains scarcely any milk  globules, mixed with a very few colostrum
corpuscles.
  2d. Those in whom  the  colostrum  is more or less abundant, but
poor  in  milk globules, which  are small, ill-formed, and  containing
also colostrum and mucous corpuscles.
  3d. Those in whom  the  colostrum  is very abundant, rich in milk
globules, which are of good size, and  unmixed with  any other cor-
puscles save those proper to the colostrum.
  Now, the indications  to be deduced  from the different states of the
colostrum just described are—
  That the first state appertains to women in whom the secretion of
milk after child-birth  is either  very little, or in whom  there is pro-
duced but  a serous milk, poor in nutritive elements, and therefore
insufficient for the nourishment of the  child.
                    * Cours de Microscopie, p. 406. 
208
ORGANIZED  FLUIDS.
  That the second condition  indicates those in whom tne secretion
of milk after confinement is either small or abundant in quantity, but
which is always poor and serous.
  That the third  state of the colostrum belongs only to such women
as have an abundant supply of milk of good quality.

  THE MILIT.  OF WOMEN WHO HAVE BEEN DELIVERED, BUT WHO HAVE NOT NURSED
                         THEIR OFFSPRING.
  The mammary gland of women who have borne children, but who
have not  nursed them, is frequently found to  contain milk  many
months after confinement.
  This milk always presents the characters of colostrum.

                  MILK IN THE BREASTS OF CHILDREN.
  A milk-like fluid can frequently be expressed from the breasts of
infants and young children, both male and female.
  This fluid, examined microscopically, has been found to exhibit all
the  characters of ordinary milk; and, in some cases, the  colostrum
Gorpuscles have even been detected in it.

                      DIFFERENT KINDS  OF MILK
  The milk of one mammiferous animal resembles so closely that of
another that it is often a matter of impossibility to distinguish,  either
with the naked eye or by means of the microscope, the different kinds
of milk.
  The milk of the ass may, however, be generally known by  its
watery aspect, its bluish tint, and its lightness;  that of woman by the
promptitude with which the layer of cream is formed upon it;  but it
is, above all, by the taste that the several kinds  of milk are charac-
terized: thus, the taste of the milk of the cow can scarcely be con-
founded with that of the ass or goat, nor can the flavour of the milk
of woman be mistaken for that of any of these.
  The microscope aids but little in the discrimination of the different
kinds of milk: the globules  of the milk of the goat are certainlv
smaller than those of the other species named, and those of the  ass
are  less numerous; nevertheless, these characters  are so  little con-
stant that  they are not, in many instances, sufficient to  distinguish
them from the milk of the cow or of woman.
  The number of globules contained in  the milk of different animals
doubtless varies considerably; but there is as much variation in this 
                              MILK.                          209

respect as in those just  referred to; and, therefore, this difference is
not sufficient to distinguish the several kinds of milk.

             RELATIVE PROPORTIONS OF  THE ELEMENTS OF MILK.
  Chemical analysis indicates a very great  variety in the relative
proportions of the different nutritive ingredients of milk; and this, not
merely with respect to the milk of different animals, but also in refer-
ence to that of the same species,  and even of the same individual, at
different times.
  The truth of these remarks will be evident from an examination of
the following analyses:

                Analysis  of tlie Milk of Woman, by Peyen.
        Butter,         -       -       -      -       5-16
        Sugar and cream,      -       -      -       7' 80

                   Analysis of the same, by F.  Simon.
        Water,         ....
        Caseine,        ....
        Sugar,          ....
        Butter,          -
        Salts, extractive matter, &c,
Analysis of the Milk of Woman, the Cow, the  Goat, and the Ass, by Meggenhqfen,
             Van-Stiptrian, Liuscius, and Bonpt, and Peligot.*
                         Woman.     Cow.      Goat.      Ass.
        Butter,     -     8 97    2*68     4 56     1-29
        Sugar,      -      120    5  68     9 12     6 29
        Caseine,    -      193    8  95     4 38     1'95
        Water,     -    87 90   84'69   81 '94    90'95

  It will be seen from the above analyses that the milk of woman is
the richest in butter, while that of the  ass  contains  the  smallest
amount of that element.
  The  assertion made by Donne, that  the quantity of butter in the
milk of the same species  stands in relation  with that of the  other
essential ingredients of the milk, although supported by the  researches
of Peyen and Peligot, is contradicted by those of F. Simon.  Accord-
       * This analysis is copied from the Cours de Microscopic of Donne.
                             14
88	06
3	•70
4	54
3	40
0	30
100	00
 
210
ORGANIZED FLUIDS.
ing to the analyses of Simon, the quantity of sugar is greatest imme-
diately after delivery;  a few days  being passed, this diminishes, and
the amount of caseine, which was at first  very small, undergoes a
gradual augmentation.  The butter Simon considers to be the  most
variable  element of the milk, its  variations not being reducible to
any law.
  The relative proportion of the different  ingredients of the  milk of
animals may be modified, and almost altered, at will, by the adoption
of a certain regimen.

                            GOOD  MILK.
  The purity and the richness of milk were formerly estimated by its
specific gravity, which is about 1 '032; if the milk was poor in cream,
or if it was diluted with water, it was supposed that the gravity of the
fluid would be in the first case increased, and in the second lessened.
  The cream being the lightest element of the milk, its deficiency or
its abstraction would, of course, increase the density of the remaining
fluid, and the addition of water, after the removal of the  cream, which
is also of less weight than  milk which is even pure and rich, would,
of course, raise the gravity of the milk either up to or even  beyond
its natural weight.
  Now, the abstraction of the globular element of the milk and the
addition of water are the two frauds most frequently had recourse to;
and they are of such a nature as  to  elude detection by reference to
the specific gravity of the  milk, when they  are both put in practice
in combination.
  The specific gravity test  of the purity and  richness of milk is, then,
one which is fallacious, and therefore but of very little value.
  It has been proposed by M. QueVenne, not merely to estimate the
specific gravity of milk, but also to  measure the layer of cream which
forms upon it by repose.  This ingenious method is scarcely more to
be depended upon than  the preceding, and is put at fault by the fact
that the addition of water favours  the ascension of the cream.
  Thus, the layer of cream formed on milk to wrhich water has been
added will be thicker than that of unadulterated milk, this effect being
the consequence of the lessened specific gravity resulting  from the
addition of the water.
  Donne has made the statement, which is borne out by the analyses
of MM. Peyen and Peligot, that the globular or buttery element of
the milk stands in relation, in the milk of the same species of  animal, 
MILK.
211
though not in different species, with the other nutritive ingredients of
milk, the cheese  and the sugar.  The analyses referred to  are the
following:

                 Milk of Woman,  analyzed by M. Peyen.
            Butter,    -    -     5-16   5*18    520
             Sugar and cheese,   7 • 80   8 • 10    9 • 80

                 Milk of Asses, analyzed by M.  Peligot.
     Butter,   -     -    155   1-40    1*23    1*75   1-51
     Sugar and cheese,  10*11   7-97    7  34    8 '25   7 -80

   Donne, therefore,  proposes to  estimate the purity and the richness
of milk by means of the globular element contained within it.  The
eye  alone will, in some measure, indicate the number of globules con-
tained in the milk; for, since the opacity of milk is due to the presence
of the globules, it may be  concluded that the milk which is white and
opaque is rich in globules, while  that which is watery and transparent
is poor in the same.
   The microscope, however, is a more certain means  of determining
the number of the globules, although by means of this instrument we
can  only arrive at an approximative knowledge of their amount.
   In order to estimate as  nearly as possible  the  number of globules
existing in the milk,  M.  Donne has invented an  apparatus which he
has termed a lactoscope.   By  means of this  instrument, the milk can
be examined in very thin layers; and in proportion to the opacity of
the milk  spread out in such layers, so will be its richness—the deeper
the stratum, the  richer the milk.
   There  is  one  fallacy  attending  the use of this  instrument which
requires to be noticed; this, however,  is one which  has reference to
its employment in testing the quality of the milk  of the cow, the  ass,
and the goat, and not of the milk of woman.
   The milk of commerce is frequently adulterated with substances,
such as chalk and flour, which  are intended to heighten its colour
and opacity; the  presence of these then in the milk would, to a cer-
tain extent, lessen the value of the opinion  to be deduced from  an
examination of the milk with the lactoscope  of Donne.
  The effect, however, of the admixture of chalk  and flour, in height-
ening the opacity  of milk, is not so considerable as might be supposed,
and this is especially  found to be  the case when it is spread out in thin 
212
ORGANIZED  FLUIDS.
layers, as in the lactoscope.   Moreover, the presence of an insoluble
substance in the milk might be detected by means of the microscope.
  Applied to the examination of the  milk  of woman, the  lactoscope
would not be subject to the  above fallacy.
  Having now shown that  the globules constitute an important ele-
ment of the milk, and  the methods by which their  number may be
ascertained, we may, in the  next place, describe more particularly the
qualities of good milk.
  Healthy milk may be defined to be  an alkaline fluid, having a spe-
cific gravity of about 1 • 032, holding in suspension numerous perfectly
spherical and discrete globules, soluble  in ether, and therefore of a fatty
nature; and, in solution, cheese and sugar, together with  various salts.
  If, on the contrary, the milk be viscous or  acid—if the globules be
ill-formed or few in number—if they adhere together in masses, and
do not roll freely and separately  in the serum—if also this contain the
colostrum corpuscles—then  the milk  is either imperfectly elaborated
or diseased.
  Whenever the proper globules of the milk occur abundantly, are of
the  usual size,  and are  equally diffused throughout the serum, we may
conclude that the other nutritive elements of the milk  are likewise
present in due proportion.   (See Plate XIV. fig. 1.)
  It must be held in mind, however, that the milk  of different animals
does not contain  normally  the  same relative  amount  of  nutritive
ingredients: thus,  the  milk  of woman is  especially rich  in cream,
while that of the goat and ass is  but poor in that element.

                            POOR MILK.
  Not unfrequently the milk is found to contain a  less quantity of
globules than ordinary: the  milk in which a deficiency of its globular
element exists  appears  watery and transparent, and is also  usually of
greater specific gravity than good milk.   (See Plate XIV. fig. 2.)
  This condition of the milk is one of its  most common  as well as
most serious states in its consequences to the child.
  At the same time that the milk is poor in globules or in cream, the
serum may be either deficient in quantity, or it may be in excess.
  In either case, such milk,  whether it be human  or  not, is  deficient
of the amount of the nutritive ingredients  necessary for the growth
and development of the child, which, instead of increasing in size,
daily diminishes, becoming faded and  emaciated.   In the instances in
which milk containing  a super-abundance of serum is received into 
MILK.                         213
 th ■ stomach,  that  organ becomes distended and weakened by its
 engorgement with a fluid, the digestion of which brings with it  little
 or no nourishment.
   An  infant whose strength  is reduced  by the  poverty of the milk
 given to it, is not  unfrequently the subject of diarrhoea, which still
 further lessens its powers.

                             RICH MILK.
   An opposite condition of the milk to that just described frequently
 exists, viz: that in which its nutritive principles are in excess, a fact
 which is most readily ascertained by an examination of the  state of
 the globular element of the milk: this  being super-abundant, it  may,
 as already shown, be concluded that the sugar and  cheese  likewise
 occur in unusual quantities.   (See  Plate XIV. fig. 5.)
   This condition of the milk  is not to be regarded as an alteration
 of its qualities, but merely as an exaggeration of them; nevertheless,
 it is one which is often incompatible with the well-being of the child.
 This  rich  milk  is often too strong for the  digestive  powers of the
 child, whose  nutrition in consequence suffers: it, moreover, is some-
 times the occasion of colic and diarrhoea.
   The state of the milk just noticed, and its consequent effects  upon
 the child, may be modified, and even entirely remedied, by a judicious
 regulation  of the diet, as well as by permitting the milk to remain in
 the breast for a considerable time, the effect of which  retention  is to
 render it more watery; the infant, also, should not be allowed to take
 the breast except at long intervals.
  At  the same  time  that  the  globules are more numerous  in  milk
 which is rich, they are also larger.  The size of the  globules is  like-
 wise found to undergo an  increase from the first days of lactation,
 and this increase continues for some  months afterwards: thus, the
globules of the third month are larger than those of the first month,
 and those  of the sixth month still larger, the  number of the  very
small  globules having  diminished very considerably.  The increase
in the size of the globules referred to, is not, however, so uniform or
so constant as to allow of the determination from it of the age of the
milk.
                       ADULTERATIONS OF MILK
  There are but few articles of general consumption more adul-
terated, and on which more frauds are  practised, than the milk.
  The more usual substances employed for  the purpose of adultera- 
214
ORGANIZED  FLUIDS.
tion are water, flour or starch, chalk, and the brains of sheep; of
these, water is the one which is most frequently had recourse to, and
which is the most difficult to detect.
   The  effect  of water in  altering the specific gravity of milk has
already been referred to; and it has been shown that the result of its
addition to milk, a portion of the cream of which has been abstracted,
is to restore the specific gravity which usually belongs to it.
   Donne has shown that, however much the gravity of milk may
vary, the density of the serum of the milk is almost constant.   This
fact is interesting and important; for, by a knowledge of it, the dete-
rioration  of milk by its  admixture with  water, or with some other
substance of  the same density with it, may be  ascertained.  The
serum is  constantly heavier than water; adulteration with it would
then cause  the serum to exhibit a less  specific  gravity  than that
which should  properly characterize it;  the conclusion to be deduced
from  this circumstance being that the milk has  been deteriorated,
most probably, by the addition of water.
   The adulterations with flour and sheep's brains are readily detected
by means of  the microscope.  The fraud by  the former may  be
recognised by the peculiar  form of the flour granules, as well as by
the action of iodine upon them (See Plate XV. fig. 6); and that by
the latter may be distinguished by the detection, in the fluid, of more
or less of cerebral structure, and especially of the nervous tubuli.
   The chalk in the  milk is readily revealed by its effervescence with
hydrochloric acid, as well as by its weight, which causes it to subside
at the bottom of the vessel containing the milk.

                       FORMATION OF BUTTER.
   Several explanations have been proposed with the view of deter-
mining the exact cause of the amalgamation of the cream globules
with each other, and the formation of butter.
   Some have supposed that  the trituration to which the globules are
subject  in the churn, determines their union and incorporation with
each other;  but it is known that the amalgamation is not a gradual
process, as it would  be were their union to depend upon trituration
but that it takes place in a manner almost instantaneous: moreover
agitation might fairly be presumed to have a contrary effect  on the
globules, which participate  in the properties of oil, and that it would
cause their further sub-division.
   A second hypothesis conceives that  a chemical  alteration in the 
MILK.
215
condition of the globules  is determined  by the  presence of the air:
this has been shown to be  erroneous by the fact that butter will form
in vacuo.
   A third theory presumed that an acid state  of the  milk  alwavs
preceded  the formation of the butter: this notion is disproved, since
butter is  formed of cream, the alkalinity of which is purposely  pre-
served by the addition of soda or any other alkali.
   Donn&  thus  explains the formation of butter: "The butter glob-
ules," he  says,  "are surrounded in the cream by cheese in a viscous
state:  this matter isolates the globules the one from the other,  and is
opposed  to their union.   The churning coagulates  the  cheese in
which the globules  are  imbedded, and, once separated from this, the
grease globules unite and agglomerate together easily."
   It is doubtful  how far this  explanation,  though  more satisfactory
than its predecessors, really accounts for  the instantaneous formation
of  the butter.           ✓
    MODIFICATIONS EXPERIENCED  BY  MILK ABANDONED TO ITSELF, AND IN WHICH
                     PUTREFACTION  HAS COMMENCED.
   The  first  change which  the  milk  undergoes, subsequent  to its
abstraction  from the system, is that which  has already been referred
to,  and which  consists in the separation of the globular or buttery
element of the milk  from its other constituents, and its ascension to
the surface of the  fluid,  where  it forms the layer of cream;  this
change in the  arrangement of the components  of the milk is deter-
mined by the  lighter  specific  gravity of the proper milk  or  butter
globules.
  All the  milk  globules do  not, however, ascend  and join those  which
constitute the  cream: it is chiefly the larger ones which  do so, the
smaller remaining diffused  through the subjacent milk, to which they
impart the degree of opacity which belongs to it.
  These smaller globules are not,  however, equally scattered through
the skimmed milk, the greater portion of them being spread through
the upper stratum  of it, and  the  lower appearing almost  clear  and
transparent, containing but few butter globules, and these the smallest,
as well as the minute cheese globules already described.
  These changes consist  merely  in  a different disposition  of  the
normal constituents of milk, and are unaccompanied by any alteration
in the constitution of its elements.  The next  series  of alterations
have reference to the decomposition of the milk,  and are attended by
changes in the actual state and composition of the milk. 
216
ORGANISED  FLUIDS.
  The first change experienced by the milk, indicative of  com-
mencing decomposition, is that from an alkaline to an acid condition.
This acidity, slight at first, goes on  increasing, until at  length  other
alterations  are  produced; thus, the  layer of cream becomes  thicker
and thicker, condenses itself into a mass, and finally presents almost
the appearance of butter; at the same time the cheese is coagulated,
and precipitates itself to  the bottom of the  liquid: a portion  of it,
however, frequently remains suspended  in the  milk, in  consequence
of its retaining a number of butter globules, which lessen its specific
gravity.  Soon, however, other changes show themselves, still  more
indicative of putrefaction: the layer of cream swells  up, becomes
more yellow, and a fungus springs up upon its surface, the Penicillum
glaucum.  This at first presents the appearance of white velvet; but
afterwards, as  soon as the fungus has reached the period of fructi-
fication, it assumes a green colour.
  The idea of M. Turpin, that this fungus had its origin in, and was
developed from, the milk globule, scarcely requires a serious refutation.
  At  the same time, the odour of the milk  undergoes a  complete
change:  sweet when it is fresh, it becomes acid as it decomposes, and
gives out more especially the smell of cheese.
  Examined with the microscope, in addition to the fungus alluded to
above, numerous infusory animalcules will likewise be detected.
  Now, the changes above described, and which are experienced by
the milk  of every animal, will be more clearly understood if the milk
be previously filtered, and the butter  and the serum being obtained
separately,  those alterations which ensue in each be noticed.
  It will be observed, that it is the butter, or non-azotised substance,
which  undergoes the acid fermentation, and on which the  fungi are
principally  and most generally developed.
  The serum,  on the contrary, becomes alkaline,  and  exhibits the
ammoniacal or putrid fermentation, this  depending upon the azotised
principle which it holds in solution, viz:  the cheese.
  It will be remarked, also, that the serum, in changing,  does not
exhibit the  striking odour of cheese which  the milk itself  gives out
under the same circumstances, and from which it may be concluded
that a  certain  amount of  butter is necessary  to produce the peculiar
smell of cheese.
  The phenomena to which the putrefaction of milk give rise result,
then, from two kinds of fermentation; the acid, in which the buttery
element of the milk is concerned, and the alkaline, resulting from the
decomposition of the caseine. 
MILK.
217
             THE OCCURRENCE OF MEDICINES, ETC., IN  THE MTLK
  The  extreme  rapidity with which the  formation of milk from the
blood is effected  is most surprising, and is  only equalled in the animal
economy  by that with which the urine is itself secreted.
  The  rapid  secretion of milk  from the  blood  serves to explain the
almost immediate appearance in the former fluid of various chemical
reagents  and articles  of food introduced into the system through the
medium of the stomach.
  Thus,  many articles taken  as food, or  as  medicine,  have been
detected in the milk a few minutes after they have been received into
the  stomach.  The colouring  matter  of madder-root,  the odorous
principles of garlic, turpentine, &c.—neutral  salts, nitrate of potas-
sium—have all been encountered in the milk.
  These  particulars  show the  necessity of great precaution  in  the
prescribing of remedies for a nursing mother, and explain the great
susceptibility of children at the breast to the influence of  the medicine
administered  to the parent.
  [Farther than the directions already given for the examination of Lymph,
Chyle and Blood, it is not thought necessary to add any instruction  for the
study of the fluids  just treated of,  the manner of preparation and examina-
tion being precisely the same, and the  different reagents most striking in
their effects having been fully indicated in the text.
  The preservation of most of the fluids will  be found a difficult matter, as
most of the preservative solutions employed would so act on the constituents
of each fluid, as  to  render them comparatively useless.   The corpuscles of
the blood are easily preserved in the manner  indicated at the close of the
chapter on that subject.
  Those of lymph, chyle, mucus, pus, and milk, are best preserved in the
flat cell with the  naphtha-water, or with Goadby's B-solution, in the manner
already indicated in the chapter on preservative fluids.
  With all possible care, however, these  preparations will soon lose  their
value, as the  corpuscles will undergo more or  less change, and therefore
cease to have the same characters, as fresh specimens of the same fluid.] 
218
ORGANIZED  FLUIDS.
                   ART.  VI. — THE  SEMEN.

  The  seminal fluid, arrived at its perfect state, as when it is ejacu-
lated, is not a simple liquid, the secretion of a single organ, but is
compounded of the several products furnished, though not in an equal
proportion, by  the testicle, the epididymis, the vas deferens, the pros-
tate  gland,  the glands of  Cowper, the  vesiculae seminales, and the
follicles of the urethra.
  But the spermatic  fluid is also in  another sense a compound pro-
duct ; thus,  like the fluids which have  already been described, it is
made up  of a  liquid and a solid element,  the latter  consisting of
numerous organized particles suspended in and diffused  through the
former; these particles are of more than one kind, and may be divided
into  those which  are  essential and  those which are non-essential:
those which belong to the first category are the spermatozoa, the  sem-
inal granules, and  the sperm atophori; and those which  appertain  to
the second, are the mucous corpuscles and epithelial scales: these last
constituents occur but seldom, and are difficult to discriminate  from
the seminal  granules and the spermatophori.
  The spermatic fluid, resulting from the above combination of solid
and fluid elements, is then usually a thick semi-opaque and gelatinous-
looking substance, of a grayish, whitish, or yellowish tint, and endowed
with a peculiar and penetrating odour, which Wagner states does not
belong to the sperm previous to its departure from the testicle itself.
  It  is, above all, the  spermatozoa, from  the liveliness  of their
motions, the variety of their forms, the peculiarity of their develop-
ments, and their functional importance, which  impart interest to the
study of the spermatic fluid, and which the microscope has shown to
occur in it in such vast numbers.

                            SPERMATOZOA.
  The  spermatozoa* are the most distinctive, as  well  as the most
interesting, constituent of the semen, and  once detected, the nature
of the fluid under examination can no longer be doubted.

  *In reference to the discovery of the spermatozoa, the following passages are con-
tained in  Leeuwenhoek (Opera, t. iv. p. 57) : "N. Hartsoeker (Prccven der Doorsich-
ikunde, s. Specimina dioplrices, p.  223) says that he made known  the spermatic
animalcules in 1678,  in the "Journal des Savants."  I attribute the discovery to 
THE S E M EN .
219
   Each spermatozoon consists of two  portions, an expanded part, to
which  has  been assigned the several  names of "disc," "head," and
"body," and an attenuated extremity, which is called "tail."
   The  spermatozoa present great varieties in size  and form:  these
variations  are, for the most  part, constant in  a natural family and
genus, and  are  always so in a simple  species:  thus, a knowledge of
the particulars  of form and  size of the seminal  animalcules is fre-
quently sufficient  to distinguish many groups, genera, and individuals
from  each  other:  spermatozoa  are, therefore, capable of affording
assistance in classification.

                              Form.
   In  the class Mammalia especially, with which, in this paper, we are
chiefly  concerned, the spermatozoa vary greatly in shape; but in sev-
eral of the  more natural groups of that class, one determined form and
magnitude  may be detected  throughout the different species consti-
tuting such groups.
   In  man,  and in  some animals which  approach near to man in their
organization, the spermatozoa are small, the head or disc is ovate, the
narrow extremity forming the  summit of the  disc,  and the  tail, pro-
ceeding from its broader end, diminishes in size from its origin to its
termination, which is  so  fine, that  its  extreme point can with diffi-
culty  be discerned.  (See Plate XVI. fig.  1.)
   In the rat and in the mouse the seminal animalcules are large, and
their form peculiar; the head is half sagittate, and moveable upon the
tail, which  is long, and attached not  to  the base of the  arrow-like
head,  but to its side:  frequently the head is curved,  in which case  it
resembles the blade of a curved cimeter.  (See Plate XVIL)
   In the guinea-pig, also, the magnitude of the spermatozoa  is great,
and the shape remarkable: in this animal the head is large, ovate,
concave on one side, and convex on the other,  the tapering and elon-
gated cauda arising from  the narrow end of the oviform head, which
may be compared in form to a mustard-spoon.   (See Plate XVIL)
Hamm.  He brought  me, in 1677, some gonorrheal matter, in  which he  found ani-
malcules  with a tail, which, according to him, were produced by the effect of decom-
position.  I afterwards examined fresh human semen, and I then perceived the same
bodies.   They were in motion, but in the liquid portion; in  the thick part they
remained immoveable.  They were smaller than the corpuscles of the blood, rounded,
obtuse before, pointed behind, with a tail five  or six times as long as the body."
The description of Leeuwenhoek appeared for the first time  in the Philosophical
Transactions, December, 1677, and January and February, 1678. 
220
ORGANIZED  FLUIDS.
   In birds, two singular  types  occur, the one characteristic of the
order Passeres, the other typical of the Rapaces, Scansores, Gallina;,
Grallce, and Palmipedes.   In the first, the head of the spermatozoon
is elongated and spiral, resembling a corkscrew; the number of coils
and  the  acuteness of the  angles vary in different species; usually
two, three, or four turns are described;  the attenuated  and greatly
produced tail proceeds from the  finer end  of the spire, and between it
and  the body no exact line of demarcation exists.  (See  Plate  XVI.
fig. 2.)   In the second, there is a distinct division into head and tail,
and  the former is elongated, as in the order Passeres; but, in  place
of being spirally coiled, is  straight; the tail, arising abruptly from the
body, is of great tenuity, of equal diameter, and the length exceeding
but little that of the body.
   The various forms assumed by the spermatozoa among  the  other
vertebrate and invertebrate animals, it is unnecessary here to describe:
the shape of those, however, belonging to  the Tritons and  Salaman-
ders, from  their great peculiarity, may  be  briefly noticed.   At the
junction of the body and tail of each spermatic animalcule an enlarge-
ment exists, the excessively attenuated caudal extremity being curved
spirally round the  body.
   The effect of water in modifying the form of the  spermatozoa is
remarkable, it frequently causing them, when applied  in  large quan-
tities, to coil up and form themselves into  rings:  this effect of the
application of water is supposed to depend  upon some hygroscopic
property possessed by the  spermatozoa.
   Frequently the spermatozoa are seen to occur on the  field of the
microscope, grouped together in  bundles, the bodies all lying one way,
and fitting by their concavities into each other.  (See Plate XVIL)
This arrangement, as will  be  seen hereafter, is connected with  the
evolution of the spermatozoa.
   Occasionally, in man and other animals, the head and tail are sepa-
rated from  each  other, and lie  apart;  this  separation is  doubtless
either the result of violence or the effect  of  decomposition.   Henle*
states that  he has seen the tail move independently of the head.

                              Size.
   Much diversity exists in the  size of the  spermatozoa  in  different
animals, although but little difference  can be detected in those of the
same individual.   Wagner, however,  has  made the  observation that
                        * Anat. Gen. p. 534. 
THE  SEMEN.
221
their  magnitude varies greatly in different  individuals of the same
species.  These variations are, however, of course,  confined within
certain  narrow  limits.   In  the  Mammalia,  the  spermatozoa  of
man are among the smallest, while  those of the guinea-pig and rat
are among the largest hitherto discovered.  In the birds the seminal
animalcules of the order Passeres are very large, and especially those
of the chaffinch.

                            Structure.

  When first the  spermatozoa were discovered,  and their  lively
motions observed, much  reluctance  was entertained to regard them
as independent animals or beings; and upon this point, even among
modern physiologists,  there  is still  an absence of  accord, some  of
them attempting  to  explain the  movements  exhibited on purely
physical principles.
  Not many years ago, a celebrated and talented continental observer
thus expressed himself, in  terms more ingenious than accurate,  in
reference to the nature of the spermatozoa:

  "When  we place upon  the object-glass  of  the  microscope  the
semen of a  subject who enjoys all the energy of his generative
faculty, we there see corpuscles more or less rounded or oval, having
a sort of caudiform appendix: some have made animalcules of these
little bodies, since they have seen that they move, and have believed
to have recognised  in their movements a  determined direction, a
character  which  they thought could only  appertain  to animated
beings.  And  as  among the  microscopic animalcules which they
knew there are those  which  are provided with a tail more or less
prolonged  and more or less dilated, they have assimilated to them the
little animalcules of the semen, and have made them Cercarice.
  "But you are about to see that  the conformation and the move-
ments of  the  corpuscles in  question may  be explained  naturally,
without our being obliged to have recourse to the hypothesis of which
I have spoken.  It is certain that we find in the sperm little gelatini-
form  masses,  more  or  less  rounded, oval,  and having one part
prolonged  into the form of a tail, like,  in a  word,  to the drawings
which Buffon  and many other observers have  given us of the pre-
tended spermatic animalcules.  These little masses float in a material
less consistent than  themselves, and  even fluid.  But at first their
oval form results evidently from the manner in which they reflect the 
222
ORGANIZED FLUIDS.
light, and afterwards as the fluid in which they are suspended—a fluid
which is itself more or less viscous—attaches  itself strongly to them,
it results that in the microscO-chemical movements which take place
in the sperm, the corpuscles which it encloses seem to have a tendency
to escape from the kind  of glutinous material which contains them.
This material, seeking,  if we may express it thus,  to  retain them,
accompanies them to the situation only where they find themselves to
be arrested by a filamentous prolongation, which presents sufficiently
well the appearance of a tail,  and  even of a flexible tail, by reason of
the lateral movements which  the little body makes in its progression.
There is merely in all this, as  you  see, a mechanical phenomenon, and,
in the movement which  there takes place, but a physical effect of the
contact of  two materials of different densities;  contact which pro-
vokes these materials to mingle  together and to  form but  one, as
arrives at the end of a time more  or less long.  Abandon the semen
to itself, taking care that its watery part cannot evaporate by placing
it in an atmosphere saturated with humidity, at the end  of a  certain
time the mixture of the  two materials will be complete, and you will
perceive no longer any thing  but a homogeneous fluid; the pretended
animalcules have disappeared.
  "If we wish to show you at the  same time veritable microscopic
animalcules and the little gelatiniform  masses which move  in  the
vehicle  of  the sperm, you will  find a great difference between  the
first and these  last.  I may fortify my opinion on this  subject with
that of Buffon and Spallanzani,  who have denied that the masses  of
which I speak were animalcules.
  "Among the persons  who  have  admitted  the existence  of these
beings, there are those who have carried their pretension so far as to
class them in genera and species  by taking the form of the  dilated
extremity for the principal zoological character. Some micrographers,
also, remarking the differences  in the corpuscles  of the  sperm,
according as one procures this liquid from  the testicle, the  vesiculse
seminales, or after its ejaculation,  have pretended,  from that  circum-
stance, to describe a series of evolutions in the development of these
so-called Cercarice.  They have  told us that these  animals  do  not
exist in the product which occupies our attention at the moment that
it is formed; that they appear but in the vesiculse  seminales;  that in
these  they  are as  yet but simple  globular animals; that in their
progress they become developed  by the production  of their caudal
prolongations.   Lastly, it has been pretended—doubtless with  the 
THE  SEMEN.
223
 design of marking with ridicule the opinions which we have reported—
 it has been pretended,  I say, that the spermatic infusorias became
 among us, for example, veritable homuncules, having  little arms,
 little legs, &c.  But this is sufficient in itself to put us on our guard
 against an  optical illusion which has unfortunately seduced  a great
 number of persons, from Leeuwenhoek, one of its first favourers, even
 to MM. Prevost and Dumas, who in these latter days have still main-
 tained the existence of the spermatic animalcules."

   In the  present day, it is needless to enter into any refutation of the
 above views;  it cannot, however, fail  to be observed by the reader,
 that they are weakest just where they should exhibit the most strength,
 that is, in the explanations given as  to the  form and motions of the
 spermatozoa.
   Those  physiologists who deny the animality  of  the  spermatozoa
 would, of course,  be very reluctant to admit of the  existence of  any
 thing like organization in them; while those, on the other hand, who
 entertained a belief in their animal nature, would be most anxious to
 establish  the fact of such organization.
   The greatest possible difference of opinion, then, exists as to whether
 the spermatozoa are organized or  not, ^.nd, if organized, as to the
 extent to  which they are so.
   In  the  centre of the  disc of the spermatozoa of man and some
 other animals a light spot has been observed; this some have imag-
 ined to be a stomach;  others, again, have rejected this idea, and thus
 account for its presence: the disc, they say, is not ot equal thickness,
 and, like the red blood corpuscle, is thinnest in the centre, and which
 part, therefore, exhibits a lighter tint  than  the remainder: this latter
 view  is most probably the correct one.  The first  opinion  is enter-
 tained by  Valentin, and the second by Dujardin and Henle.   Miiller
 conceived the spot in question to be a nucleus.*
  Leeuwenhoek remarked upon the spermatozoa of the ram two
 clear  spots; at another time, numerous little  points in the interior;  a
 third  time,  two semi-lunar striae, united  by a longitudinal line; he
 figures also  in  those of the rabbit a multitude of little globules—one
 of them, larger than the  rest, being placed near the tail.
  Gerber  assigns a most  complex structure  to the spermatic animal-
cules  of the guinea-pig,  describing stomachs similar to those of  the
polygastric infusoriae, an anus and sexual apparatus; and  conceiving
*Miiller's Physiology, p. 635. 
224
ORGANIZED  FLUIDS.
 the existence of these several parts to have been established, he thus
 expresses himself in reference to the nature of spermatozoa in general:
 "The compound  organization of the seminal animalcules  and their
 production by  no  equivocal  generation,  but in  particular  sexual
 organs, and by the  means  of ova, to all appearance proclaim their
 affinity to the Entozoa."*
   Valentin f has described  an almost similar amount of organization
 in the spermatozoa of the bear:  "The clear spermatozoa of the bear,"
 he  writes, "which  in external form approach  those of the rabbit,
 present distinct traces of internal organization, to  wit, an anterior
 and posterior haustellate mouth, and internal cavities or convolutions
 of an intestine."
  Again,  Dujardin J has described and figured certain irregular knots
 and lobular enlargements at the root of the  tail of the human sperma-
 tozoa; these  have  been  noticed by Wagner,  who believes  that they
 occur only as the  effects of certain alterations  experienced by the
 animalcules in consequence of their long stay  in urine, and especially
 when this fluid has contained at the same time a quantity of puriform
 sediment.
  Wagner likewise points out, as occurring now and then, but by no
 means constantly, a small prominence or trunk-like  process  situated
 on  the anterior part of the body of human spermatozoa: this, or  a
 similar  projection, he also states to be much more regularly present
 in the seminal animalcules of the bat, in which they occur as pointed
 spines.  The same observer has, moreover, noticed upon one or two
 occasions  the caudal end of the body  to be double, bifid, or forked,
 and once  too  the  body appeared to be double, as in a  bicephalous
 monster.§
  The above  comprise all  the particulars which have hitherto been
promulgated  in  reference to the organization of the spermatozoa;
scarcely any one of them has, however, been sufficiently  established:
we  are  therefore not authorized to receive them as proved, and to
build  any reasoning upon them: the most which we  are warranted
in deducing from them amounts  to this, that  traces  of organization
have  been discovered in the spermatozoa, the  precise  nature and
extent of which have not as  yet been satisfactorily determined.

         * Gerber's  General Anatomy, translated by Gulliver, p. 337.
         t Repertorium, 1837.
         J Ann. des Sciences Nat. viii. p. 293. plate 9. 1827.
         § Elements  of Special Physiology, pp. 10.16. 
THE  S EME N.
225
  Notwithstanding his  observations, given above, Wagner* states
that  he has been utterly unable, after varied,  repeated, and  long-
continued examination, to discover true internal organs in the sperma-
tozoa.   Sieboldf has also been equally unsuccessful in his endeavours
to detect such, as also HenleJ and Koelleker.
  The determination of the fact that the spermatozoa are possessed
of even  the smallest amount of  organization, would  involve their
classification  in  the animal kingdom,  and the  description of the
different forms which occur as so many distinct species.
  The view of the animal  nature  of the spermatozoa would appear
to gather strength, and to admit almost of positive demonstration, by
reference to their very remarkable motions.

                    MOTIONS OF THE SPERMATOZOA.
  It is impossible that any  thing can convey a more  just idea of life
than  the  spectacle  of  a drop of the  seminal  fluid in  which the
spermatozoa are in active and ceaseless motion.
  Sometimes, indeed,  when the  semen is thick  and tenacious, the
movements of the contained spermatozoa are but feeble, the density
of the liquor seminis presenting too great an impediment to the free
motion of these minute creatures.
  Often, however, in such cases, when the fluid has been diluted with
water or  with some other  liquid, as serum or milk, of less  density
than itself, the spermatozoa, being now set at liberty, will frequently
be seen to resume their locomotive powers, and to move about with
the greatest activity.  All the spermatozoa, however, contained in a
drop  of  semen which  has undergone  dilution  will not start  into
motion  at once;  many  of them  will remain for a time perfectly
motionless, and then suddenly, and, as it were, by an act of volition,
begin to move themselves in all directions.

                      Mode of Progression.
  The motions of the spermatozoa are effected principally by means
of the tail, which  is moved alternately from side to  side, and during
progression the head is always in advance.
  The strength of the spermatozoa is considerable, it enabling them,
when they are immersed in either blood or milk, to  cast aside, with

    * Loc. cit. p. 17.               f Siebold in Weigman's Archiv. 1838.
    | Anatomie Gcn».rn!<>, t. vii. p. 531.
                          15 
226
ORGANIZED  FLUIDS.
the greatest  ease, the globules which  may present themselves to
impede their progress.
   The spiral spermatozoa  of the Passeres advance by a movement
of rotation of the body,  the tail remaining extended and motionless,
acting rather  as a rudder than  as  an organ of locomotion.  The
spermatozoa of  the  other  orders of birds,  and which consist of a
cylindrical body to which a short  and attenuated tail is  attached,
"scull themselves forward with  their  tails, either striking them slowly
and with  wide sinuosities, or more quickly and shortly, as when a
whip  is shaken; they thus  advance  in  circles with a quivering
motion, holding  the body extended in a straight line, although they
also now and then bend this in various directions from side to side."*
   The spermatozoa of the tritons and salamanders  usually lie coiled
up in the  form of a ring,  and seem to spin round as  upon a pivot; at
the same  time a second wavy and tremulous  motion,  like  that pro-
duced  by  cilia,  is observed;  this arises from  the rapid  rotatory or
spinning movement of the very delicate tail with which the sperma-
tozoa of these animals are furnished, and which is wound spirally
round the  body.   Wagner at one  time entertained the notion, which,
however, he subsequently discarded, that  the wavy motion  referred
to was produced by a  ciliary apparatus.  Sometimes  the coiled
spermatpzoa have been seen to unrol  themselves and to cross the
field of the microscope with slow serpentine motions.
  Furthermore, in the various motions executed by  the spermatozoa,
they exhibit all the characters of volition; thus they  move sometimes
quickly, at others slowly, alter their course, stop altogether for a time,
and again  resume their eccentric movements.  These movements it
is impossible to explain by  reference to any hygroscopic properties
which  may be inherent in the  spermatozoa, they appear to be  so
purely voluntary.  A strong argument, therefore, in favour of the
independent  animality of the spermatozoa may  be  derived from a
consideration of  the nature of their motions.

                      Duration of Motion.
  The length  of time during which the motions of  the spermatozoa
continue,  either  after the escape  of  the seminal  fluid, or after the
dgath of the  animal, varies very considerably; thus it is maintained
for "a longer period in warm weather  than in cold, and when the
semen is  retained within  its  natural  reservoirs than when  it is
                     * Wagner's Elements, p. 18. 
THE  SEMEN.
227
removed from those receptacles.  The spermatozoa of some animals
also  preserve  their powers  of locomotion for  a longer  period than
those of others; thus, the seminal animalcules of birds die very soon
after the death of the bird; according to Wagner, frequently in from
fifteen  to twenty minutes;*  occasionally, nevertheless, the sperma-
tozoa have been found moving in birds which have not been opened
until some hours have elapsed after death:  those of the Mammalia
have been observed in motion for a very long period after  the removal
of the  semen  from the testicle, and after the  death  of  the animal;
but it is in fishes that the spermatozoa retain their powers of locomo-
tion out of the body for the longest period, even for many days.
  According to Dujardin,f the spermatozoa live thirteen hours in the
testicles of the mammalia after the death of the animal.
  LamperhoffJ  has found living semen in the vesiculse seminales of
dead men, in which the spermatozoa retained the power of locomotion
for twenty hours.
  Wagner§ has observed them  exhibiting  motion at  the end of
twenty-four hours.
  Donn6|| states that he has watched their movements for an entire
day, and that he has observed them in motion even on the  second day.
  It is,  above  all, in the place of their final destination that the
spermatozoa live for the longest period;  thus,  Leeuwenhoek  first,
and  other  observers subsequently, have discovered them in a living
condition in the uterus  and Fallopian  tubes of a bitch seven days
after connexion, TI and Bischoff** has found  them alive eight days
after intercourse in the rabbit.
  The  great length of  time during which,  under certain circum-
stances, the spermatozoa retain the faculty of locomotion, furnishes
another strong argument in favour of their independent vitality.

                       Effects of Reagents.
  The seminal animalcules retain their locomotive powers for a very
long time in fluids of a bland nature; for example,  in  blood, milk,
mucus, and pus; on the contrary, in reagents of an opposite character,
and  in  those  possessed of poisonous properties, they soon cease to
move:  thus, in the saliva and urine, unless these fluids be very much
    * Wagner, loc. cit. p. 21.                f Annates des  Sciences Nat.
    I Diss, de Vesical. Semin.                $ Loc. cit. p. 22.
    || Cours de Microscopie, p. 284.           II Opera Omnia, 1.1. b. p. 150.
    ** Miiller, Archiv. p. 16. 1841. 
22S
ORGANIZED  FLUIDS.
diluted, their motions are soon destroyed, and immediately cease in
the acids  and alkalies, in alcohol, iodine, strychnine, and the watery
solution of opium.
  The addition  of water to  the  spermatic  animalcules  usually pro-
duces a remarkable effect, increasing greatly for a time  the rapidity
of their motions, which  after the lapse of a minute  or two entirely
cease; this reagent, as  well  as the saliva, exerts  a  further peculiar
influence upon them, causing them to curl up into circles or rings.
  Poisons introduced into the system, and destroying  the life,  are
stated not to affect the motions of the spermatozoa; an  assertion to
be received  with some degree of  hesitation: in cases of poisoning by
prussic acid, I have usually found the spermatozoa to  be motionless,
even when viewed immediately after death.
  The urine has the property of preserving the spermatozoa entire for
weeks and months; and Donne- has detected them in that fluid after
an interval of three months.
  The result, then, of the application of reagents, furnishes an addi-
tional argument in favour of the animality of the spermatozoa,  and
one which it would be  difficult, if not  impossible,  satisfactorily to
controvert.

                          SPERMATOPHORI.
  The only essential  solid elements contained in the seminal fluid
arrived at its perfect  state, as in the vas deferens, and when  ejacu-
lated, are the spermatozoa; occasionally, however, there  are encoun-
tered in it, as non-essential constituents, mucous corpuscles, epithelial
scales,  and  the  seminal granules:  the  spermatic liquid, however,
obtained from the body of the testicle, contains not only the several
structures already named, but also  minute  and bright granules, and
the compound cells or  spermatophori, the  bright granules  and  the
seminal corpuscles probably represent stages in the  development of
the spermatophori.
  The several structures now named are all occasionally met with in
the ejaculated semen; their occurrence in it is  to be  regarded  rather
as accidental than  as  essential; the spermatophori belong to the tes-
ticle, the tubuli  seminiferi of which in many cases are almost filled
by them.
  The spermatophori differ greatly from each other, both as respects
size  and the number of secondary cells or  nuclei contained within
them;  the smaller parent cells are about T¥V7 of an inch  in diameter 
THE  SEMEN.
223
in man,  and contain usually but a  single nucleus, while the larger
ones attain  the  magnitude of ?£^ of an inch in breadth, and include
not unfrequently as many as  six or eight nuclei, or, more  properly
speaking, secondary cells.  Between the two extreme  sizes given,
every gradation  presents itself, and many spermatophori contain but
one, two, three, or four nuclei, which are the numbers most frequently
encountered.
  The secondary cells, like the primary or parent ones, are  globular,
and those contained within the same parent  cell are  usually of the
same  dimensions; the centre of these  cells occasionally presents a
bright spot.   (See Plate XVI.^g-. 1.)
  Not unfrequently certain large and perfectly transparent cells are
encountered;  these  are, in all probability, the  older spermatophori,
the contents of which have been discharged.
  It would appear, therefore, that the development and dissolution of
the spermatophori are effected entirely within  the tubes of the testes.
  Cells, which Wagner has denominated  seminal granules, occur, as
already remarked, mixed up with the undoubted spermatophori; these
first are smaller, and do not contain nuclei; whether they are really
distinct from the latter, it is not easy to determine.  If but  one kind
of cell occurs in the testicle, then a double function must be assigned
to it:  thus, in the first place, the secretion of the liquor seminis must
be effected by it; and, in the second, the development of the sperma-
tozoa  occurs  within  its cavity;  in which case the  spermatophori
would be the homologues of the cells of other glands, only in so far as
they discharge an analogous function, and are  secreting organs; in
the ulterior office allotted to them, that of being receptacles  in which
the spermatozoa are evolved, they stand alone in the animal economy,
and are certainly without analogues  in any other gland of the body.
  It is most probable, however, that two kinds of cells coexist in the
testes—the  one  secreting  and  corresponding with the cells of other
secerning organs; the other kind, of a peculiar nature, without par-
allel in the animal economy, and devoted to the  development of the
spermatozoa.
                   DEVELOPMENT  OF THE SPERMATOZOA
  Not the least interesting part of the  history of the spermatozoa  is
that having  reference to their development.
  Wagner was the  first to state that the spermatozoa  are developed
within  the spermatophori just  described. 
230
ORGANIZED  FLUIDS.
   This interesting  discovery of Wagner has been amply confirmed
by the extended observations of Kcelliker, Siebold,  Valentin,  and
Lallemand.
   Wagner thus describes the evolution of the spermatic animalcules
in the  spermatophori of a bird:  " In the course of their development,
a fine granular precipitate is observed to form between the included
nuclei, by which these are first obscured and then made to disappear,
and linear groupings are produced, which  anon proclaim themselves
as bundles of spermatozoa, already recognisable by slight traces of a
spiral  formation of one extremity.  (See  Plate  XVI. fig. 2, g.)  It
were  hard to  say  whether the  fine  granular  precipitate  is  to  be
regarded as the product of a process of resolution occurring to the
nuclei, or a new formation; as, also, whether the spermatozoa spring
out of or only in and amidst the yolk-like matter, or matter that is at
all events comparable to the yolk of eggs in general.   The vesicles
now assume an oval form (see Plate XVI. fig. 2,  h),  the globules dis-
appear, the granular contents diminish; the seminal animalcules are
well grown,  and lie bent  up within the cyst; their spiral ends  are
more   conspicuous.    The  delicate covering  (involucrum) is now
drawn more closely around the bundle of spermatozoa it includes, and
where  it covers their spiral ends anteriorly  it assumes a pyriform out-
line (see Plate XVI. fig. 2, i), and at the opposite extremity is perhaps
at this time open; but it is difficult to speak decisively on this point.
The cysts are now very commonly bent nearly at right angles or like
knees,  but at length they appear stretched out and straight, and have
attained their full size.   (See Plate XVI. fig. 2, k.)   The capsules of
these vesicles are at all times, and especially towards the end of their
existence, highly hygroscopic; the addition of a little  water causes
them to burst, the masses of spermatozoa  rolled up like a little skein
of thread or silk escape, and occasionally at this stage exhibit motions
individually, which, however, while the animalcules  continue  in  the
ducts of the testes,  are  frequently not to be observed,  and are never
either general or remarkable.   The spermatozoa,  after the rupture of
the cyst, advance in freedom to the vas deferens."*
   The process  Wagner states subsequently to be precisely similar in
man and the Mammalia, although it  is more  difficult  to follow it in
them.
   The  accuracy of the above account of the  development of  the
spermatozoa has been admitted by most other observers in all respects
          * Translation of Wagner's Elements, by Willis, pp. 25, 26. 
THE  SEMEN.
231
save one important one:  thus, Kcelliker has shown that the evolution
takes place in the included or secondary cells, and not, as Wagner
describes it, in the spaces between these, a single  spermatic animal-
cule being  formed within  each;  the  granules enclosed in  these cells
disappear gradually as the spermatozoon assumes a definite form, and
Kcelliker further supposes that these granules constitute, by their union
with each other, the substance of the spermatozoa which escape from
both the secondary and primary cells by the rupture of their investing
membranes.   When the spermatic  animalcules have escaped from
the secondary cells, and these have disappeared, the spermatozoa form
a bundle which is still included within the larger primary cell; some-
times the  seminal animalcules  are  irregularly disposed within its
cavity, but  more frequently they are applied directly to each other,
the heads lying one way, and the tails in the opposite direction.  This
disposition of them is often preserved even after their escape from the
spermatophori, during their  stay in which the spermatozoa usually
remain quite motionless.
   The interesting and  important fact of the development  of  the
spermatozoa in  the secondary cells, or ova, as they should now be
called, Kcelliker first ascertained by the study of  their evolution in
the guinea-pig;*  subsequently,  he  extended  his  observations,  and
found that  the spermatozoa in man were evolved  in  a  manner  pre-
cisely similar.
   Valentinf during his inquiries observed masses of filaments in  the
mother cells of the rabbit and bear, and Hall man J noticed the same
thing in those of the rays;  he does not, however, speak of the trans-
formation of the included  nuclei or ova.
   In the class of invertebrate animals, it is most probable that a  sim-
ilar method of development prevails.
   The spermatozoa are not encountered in equal numbers in all parts
of the testicle, the more remote convolutions of the tubuli  seminiferi
containing  chiefly the  simple granular cells and  the spermatophori,
while it is only in those which approach near to the epididymis  that
they occur in  any numbers; in this situation they  usually lie immedi-
ately beneath  the membrane of the seminiferous tube, and external to
the spermatophori, their long axes being disposed in the direction of
that of the  tube itself.  In the vas deferens the  spermatozoa are pres-

    * Beitrag. p. 56.  tab. 11.  fig. 20.              \  Repert. p. 145. 1837.
    \ Miiller, Archiv. p. 471.  1840. 
232
ORGANIZED  FLUIDS.
ent in vast numbers, and with  scarcely any admixture  of the other
solid elements of the testes.
  It is in the epididymis that the different stages  of development of
the seminal animalcules are best seen side by side.
  The spring is by far the most suitable  period for the  study of the
development of the spermatozoa, and birds, especially those of the order
Passeres, present the best examples in which to trace their evolution,
because in them the seminal animalcules  are large, and the reproduc-
tive function is excessively active for a brief and determined period.
  Wagner* has shown that from the commencement of the time of
moulting, and through the entire winter, the testes of birds undergo
an  extraordinary degeneration, the spermatozoa  and the  spermato-
phori being entirely obliterated, and the volume of the testes reduced
to at least the twentieth or thirtieth of  the  size to which  they attain
in spring.   Thus, the testis of the common chaffinch is in winter not
larger than a millet-seed, while  in spring  it exceeds a pea  in size.
  The same degeneration is doubtless  experienced  during winter,
although to a less extent, by most animals of the class Mammalia.

               THE SPERMATOZOA  ESSENTIAL  TO FERTDLITY.
  The spermatozoa do not  exist in the testes of mammalia at all
periods of life: thus, they do not make their appearance in that organ
in man until the period of puberty, and  they disappear gradually as
old age advances.  It is impossible, however, to determine the  time
at which they are first developed, or at which  they cease  to exist in
that organ, because the period of puberty differs in different individ-
uals, and  some men are  aged in constitution when others of the
same years *re hale and robust.  Certain it is, that some men retain
the power of engendering until a very advanced age, of which  fact
the celebrated Parr presents a memorable example, he having become
a father at the extraordinary age of 142.
   The number also of the spermatozoa contained in the seminal  fluid
varies  in  different individuals,  and is  usually in  proportion to the
activity of the reproductive function, and this again is dependent  to
a great extent upon the constitutional powers as well as upon the
mode of life.
   The activity, then, of the  reproductive faculty in man is in many
cases a good test of health.
   The above few facts  favour the idea of the  essentiality of the
                      * Elements, pp. 28 and 29. 
THE  SEMEN.
233
spermatozoa; others, however, of a stronger  kind, still  remain  to be
mentioned.
   Wagner has instituted some most interesting inquiries in reference
to the condition of the spermatozoa in male hybrids, and especially in
male hybrid birds, and he finds, that in them the characteristic ani-
malcules are either altogether wanting, or occur but in small numbers,
and are ill-formed and ill-conditioned;  the hybrids in which the sem-
inal animalcules have been thus  found to be absent  or degenerated,
have been ascertained to be incapable of having offspring.*
   Again, Leeuwenhoekf discovered living seminal animalcules  in the
uterus and Fallopian tubes of bitches seven days after  connexion.J
   Prevost and Dumas§ have  more  recently made the same observa-
tions at the same length of time  after intercourse.
   Siebold|| has detected the spermatozoa in a living state in the uterus
and Fallopian tubes eight days after connexion.                   sm
   Lastly,  BischofFH and Martin  Barry** have observed the sperma-
tozoa not merely  in the uterus and  Fallopian tubes, but also on  the
ovary itself.
   From these facts it is therefore evident that the  spermatozoa  are
essential  to  fecundity,  although  the precise manner in which they
are so is still involved in the  greatest  obscurity.   It is supposed by
some observers, that they make their way into the ovum  itself: this
notion is as yet without evidence to support it.
   It would be most interesting  to  determine whether impregnation
could be procured by the artificial introduction of semen, the animal-
cules of which were dead;  there  is every reason to believe that  in the
many cases in which the artificial injection  of the  seminal fluid  has

  * Loc. cit. pp. 30—34.                       t Opera Omnia, p. 150.
  I Leeuwenhoek signalized the discovery of the living spermatozoa in the  uterus
and Fallopian tubes, in the following words: " Nudo conspiciens oculo, nullum mas-
culum semen canis in ea esse dicere debuissem; at eandem mediante bono micro-
scopio, summse  mese voluptati immensam viventium  animalculorum multitudinem;
semen nempe canis masculum contemplabar. His peractis, dictam aperiebam  tubam,
in fine suae crassitudinis, ac ibidem quoque  magnam seminis masculi canis contem-
plabar copiam, quod semen illic vivebat, et hoc modo quoque cum dextra egi tuba,
ac in eadem quoque immensam seminis viventis canis masculi copiam observavi.  . .
Materiam qua matrix concita est, observans, majorem adhuc viventium animalculorum
copiam deprehendebam."
  J Annates des Scien. Nat.  t. iii. p. 122.
  || Miiller, Archiv. p. 16. 1841.               IT Wagner's Elements, p. 66.
  ** Researches in Embryology, Second Series, Phil. Trans, p.  315. 1839. 
234
organized  fluids.
been successful, the contained spermatozoa were in a living condition;
and from all that is yet known in relation to the animalcules, there is
strong presumption to believe that the experiment referred  to, viz:
the introduction of semen, the animalcules of which were dead, would
be unattended with success.
  One remarkable experiment of Spallanzani, however, deserves to be
referred to.   Most observers agree in saying, that the spermatozoa of
the frog die after  some hours of immersion in water.   It is  known,
however, that Spallanzani  succeeded in fertilizing the  ova of frogs
with spermatized water, containing three grains  of seminal fluid to
eighteen ounces of water, thirty-five hours after the mixture had been
prepared, and this, in a chamber with the thermometer at from seven-
teen to nineteen degrees;  and again, that in an ice-house, the ther-
mometer being three degrees  above zero, the  spermatized water
preserved its prolific power for fifty-seven hours.
  Now, the  tendency of  this  interesting experiment is certainly to
prove the possibility of fertilization occurring with  semen, the sper-
matozoa of which are dead: this inference would  appear, however, to
be negatived by another ingenious experiment of MM.  Prevost and
Dumas, who filtered the seminal fluid, and found that the fluid portion
which passed through the filter would not vivify the eggs, while  the
more solid  part, consisting of the spermatozoa, produced  the  results
peculiar to the seminal fluid.
  Jacobi succeeded in fertilizing the ova of a carp with  semen which
had been contained within the body of the fish for four  days;  but it
is well ascertained that the spermatozoa of fishes in general live for a
much  longer period than that  named.*   Some have supposed  that
the only use of the spermatozoa is by their movements to  hasten  the
advance of  the semen towards the Fallopian tubes.

                   PATHOLOGY OF  THE  SEMINAL FLUID.
  The quantity of seminal fluid  secreted varies greatly  according to
the age and constitution  of the individual.  In young men, and in
those whose health is vigorous,  the secretion is rapid  and  abundant;
in the aged, and in those whose vital powers are feeble,  it  is but slow
and scanty.   It is, however, in severe states of disease that the amount
of seminal fluid secreted is greatly diminished, if the formation of it
be not in  some cases altogether suspended for a time.  Under  the
  * Several most interesting particulars in reference to artificial impregnation are
given in Wagner's Elements, chap. iii. 
THE  SEMEN.
235
 influence of recovery, the quantity of semen formed again undergoes
 an augmentation.
   An inordinate secretion of the seminal fluid, as  also its prolonged
 retention in the testes, are sometimes the causes of involuntary sem-
 inal discharges, which, however, are far more frequently occasioned
 by organic weakness, the result of over-indulgence.
   If these emissions  be  very frequent, the ejaculated semen will be
 found  to be thin and  watery, and  to  contain  comparatively few
 spermatozoa.
   It is unnecessary to describe here the destructive  effects  of these
 emissions on the constitution.
   It is often a matter of great importance to determine, independently
 of any revelation on the part of the patient, whether in any particular
 case seminal effusions exist.
   This fact, it is in the power of the  microscope, according to some
 observers, in all cases to declare with the most absolute  certainty.
   After each effusion of semen, in whatever way  occasioned, a cer-
 tain amount of that fluid will  still remain behind,  adhering to the
 surfaces of the urethra;  this, of course, contains the  seminal animal-
 cules, which will be washed away on the first passage  of the urine
 through the urethra.
   The great object, then, is to  establish the fact of the  existence of
 spermatozoa in  the urine: this maybe  accomplished in two ways;
 either by filtration or decantation, the latter being perhaps the pref-
 erable method of the two; the  spermatozoa, being heavier  than the
 urine itself, always subside  at  the  bottom of the vessel, and where
 they may always be found, if present in even the smallest numbers.
   The urine, as already  mentioned,  has the property of preserving
 the seminal animalcules, which may be detected in  it months after
 their discharge  from the urethra.
   M. Donn6* states, that he has never  succeeded in detecting the
 seminal animalcules  in the urine, unless as the consequence of an
 emission of semen, and which may have occurred either during con-
 nexion, in an involuntary manner, or through masturbation.  Now,
 if  this be true, the occurrence of the spermatozoa in the urine declares
positively the fact, that a discharge of semen has been sustained, and
this particular is often in itself sufficient to enable a medical man to
form an opinion of the case.
   It seems to me, however, by no means sufficiently  proved, that an
                    * Cours de  Microscopic, p. 318. 
236
ORGANIZED FLUIDS.
 escape of the seminal fluid with the urine does not take place inde-
 pendently of any distinct emission.  I am inclined to think that such
 escape is an habitual occurrence even with the most healthy, especially
 with the continent, and that by it  the surcharged testes are  relieved
 whenever requiring such relief.
   This view is to some extent supported by the observations of Dr.
 John Davy*  and Wagner :f  the former  excellent observer  states
 that on examining the fluid from the urethra  after stool in  a healthy
 man, he had always detected spermatozoa.
   In connexion with the above few remarks on the pathology of the
 semen, we may refer to the observations of Donne" on the  effects of
 an exceedingly acid  condition of the mucus of the vagina, and  a
 very alkaline state of that of the uterus itself, on the vitality of the
 spermatozoa.
   The mucus of  the vagina, in its normal  state, is  slightly acid,  this
 degree of acidity  being perfectly compatible with  the life of the sem
 inal animalcules; but Donne"  has  shown that  under some  circum-
 stances—as from  congestion, irritation, or inflammation—this mucus
 becomes  so strongly acid as to destroy in a few seconds the vitality
 of the  spermatozoa.
   Again, the mucus of the uterus in its healthy state is slightly alka-
 line, but not so much so as  to  exert any injurious  effects  upon  the
 spermatozoa;  in conditions of derangement and disease, however, it
becomes so alkaline, as Donne" has  shown,J that in like manner with
the acid mucus of the vagina, it kills the seminal animalcules in a
very short space of time.
   Now, after  what has  been said and detailed in reference to  the
essentiality of the  spermatozoa,  it  can  scarcely be  doubted  that
women whose vaginal and uterine secretions are so disordered,  are
inapt to conceive, and this from the effect of their vitiated secretions
upon the  spermatozoa.
   It would be interesting to determine whether the spermatozoa  are
ever entirely absent from the semen of man:  it is  very probable that
in certain rare cases they are so, and from the facts  already ascer-
tained there can be  no doubt that  those individuals whose spermatic
fluid is devoid of  its characteristic living element, would  be wholly
incapable of having offspring.
   It is  probable that in the impotent the  spermatozoa are almost, if
not entirely, extinct.
    * Edin. Med. Surg. Jour. vol. ii. p. 50.              J Loc. cit. p. 21
    t Cours de Microscopic,  p. 292. 
THE  SEMEN.
237
 APPLICATIONS  OF  A  MICROSCOPIC EXAMINATION OF  THE  SEMEN TO LEGAL  MEDICINE.
  The detection  of the spermatic animalcules is frequently a matter
of high interest and importance in a  medico-legal point of view.
  There are three  classes of cases  in  which  the  microscope, by
revealing the presence of spermatozoa, is  capable of forwarding the
ends of justice, and of bringing conviction home to the guilty.
  1st.  In cases of suspected violation.
  2d. In determining the nature  of doubtful  stains observed on the
bed-clothes, &c.
  3d. In unnatural offences.
  With respect to those cases which come under the first division, it
may be  observed that the medical  testimony on which these  are
usually decided is too often of such a nature as to lead to the acquittal
of a really guilty individual; the  medical man, judging merely from
external appearances, being compelled to give evidence either directly
favourable to  the prisoner, or which is  at best but of a  doubtful
character.
  In suspected violation,  then,  when  the evidence to be deduced from
an outward examination is  insufficient for  the  formation of a  satis-
factory  and decided  opinion,  the  microscope  may frequently be
employed with the greatest advantage.
  If the offence imputed has been committed, and if connexion has
really occurred, then by means of this instrument, provided  too long
a time has not  elapsed from the period of the occurrence, that is to
say, a period not exceeding from twenty-four to forty-eight hours, the
spermatozoa will be detected in  the  mucus,  properly examined, and
obtained from the upper part of the vagina: now, the detection of these
in such a situation is a demonstration  that intercourse has taken place.*
  The examination of the urine  of women whose persons are sus-
pected to have been violated would also  frequently furnish  evidence
of the fact by manifesting the presence in it of the spermatozoa, which
in its passage through the vagina  it had washed away from its walls.
  With  reference to the second class  of cases mentioned,  those
requiring for their satisfactory elucidation  the  determination  of the
nature of suspicious stains, here again, by means of  the  microscope,
evidence the most conclusive may frequently be obtained.
  * Donne, in the Cours de Microscopic, states that he has detected the spermato-
zoa in the vaginal mucus of women admitted into the hospital, in which instances it is
most probable that connexion had occurred at least some hours previous to admission. 
238
ORGANIZED  FLUIDS.
  Now, if the stains in question be formed by the seminal fluid, and
if they be not too old, the microscope applied to them will detect in
them the spermatozoa.
  With regard to the length of time  at which the spermatozoa may
be detected in the matter of a stain, I have reason to  think that this
has scarcely a limit:  I have myself noticed them in the semen several
weeks  old, and they then  appeared  to  have  undergone scarcely a
single appreciable change, the spermatophori contained in the seminal
fluid being equally well seen.
  In examining stains occasioned by the seminal fluid, it is advisable
to use the same  precautions as  those which were  pointed  out in
reference to blood stains, and to moisten them with either serum or
albumen.
  The reader's imagination will suggest to him numberless cases in
which the determination of the nature of  suspected stains would be
a matter of the utmost importance, and would lead to the production
of evidence  of the  greatest consequence, and  in   no other wray
obtainable.
  Lastly, with reference to the third class  of cases, those of unnatural
offences: here also the microscope, by revealing the presence  of the
spermatozoa in the rectum, or on  some other  part of  the body, may
throw great light  on occurrences which otherwise would in all proba-
bility be buried in complete oblivion and mystery.
  An examination of this  kind was  assigned by the  magistrates in
France  some years ago to two physicians, on the occasion  of  an
assassination in a hotel.   A traveller  having been  killed  by a  young
man whom he had received into his chamber during the night, justice
was interested to  know whether semen would be found in the rectum
or not.*
  It  is known that in death  by hanging, an emission of the  semen
usually  occurs, and this, in the absence of other  proofs, has  been
adduced as a sign of death by suspension.  It would appear, however
that such an indication is not without its sources of fallacy.
  It is thus apparent that in the cases here  referred to, the microscope
is capable of affording positive evidence  of a most  important and
conclusive kind; on the  other hand,  the negative testimony deduci-
ble from its application in these cases is not without its value.
  * See Annates d'Hygiene Publique et de Medecine Legale, Paris, 1839, t. xxi  pp.
168 and 466. 
THE SEMEN.
239
                                SEMEN.
  [In making examinations of the seminal fluid, the purest  and most  con-
centrated will be found in the vas deferens or  epididymis  The sooner this
is examined after the death of an animal, the less change will be detected,
and the motions of the spermatozoa will be most active.   If a small  drop of
the fluid is placed on a plain glass slide, covered with thin glass, and placed
in  the field of the microscope, many of the spermatozoa will be seen in active
motion, with  a }th-inch object-glass.   It  will be found  better to dilute the
fluid before covering it with the thin glass.   For this purpose,  albumen, or
a little water which has J^th part of salt or sugar dissolved in it, will  answer,
or, still better, a little serum of the blood.   When properly  diluted, the
thin glass is  applied, as before,  and the  seminal animalcules will be much
better defined than without this dilution.   The reagents most striking in  their
effects have already been pointed out.


                           PRESERVATION.
   The seminal animalcules may be preserved, either in their own fluid, or
in a weak solution of salt  and water, or of chromic acid.  In  either case,
the flat cell, or the thin glass cell, is to be employed, and the cover cemented
with gold-size.  In this condition, they will keep for many years.] 
UNORGANIZED   FLUIDS.
       ART.  VII.—SALIVA,  BILE,  SWEAT,  URINE.

  The fluids comprised under the heading of Unorganized  Fluids
differ from those of the  first division, viz:  the  Organized, in that
they do not contain, as  essential elements, organized structures;  solid
organic particles are indeed usually to be encountered in them, but
these are to be regarded either as accidental, or at all events as non-
essential  adjuncts, and  which appertain usually  to  the structure of
those organs from which the fluids have themselves  proceeded.
  The presence and nature of the solids contained in the Unorgan-
ized Fluids serve to indicate, to a considerable extent, the condition
of the glands by which they have been secreted,  and thus frequently
throw great light upon  their pathology.
  There  is, however, one kind  of solid constituent which is found
almost constantly in these fluids, viz: the crystals  of various salts:
these being, however, unorganized, their consideration does not prop-
erly  belong to  a work devoted  to  descriptions and delineations of
organized tissues.
  It is proposed, therefore, in  order to render the application of the
microscope to human physiology and pathology as complete as possi-
ble, to prepare a separate treatise on the subject of the crystallizations
formed in  the  various  fluids, &c.,  of  the body,  under  the title of
Human Crystallography.
  We will now pass in  review the fluids comprehended in the division
of Unorganized Fluids.  In reference to some  of them,  but  little
remains to be  said, as  will have been  inferred from a knowledge of
their structureless character.   In  the  treatise on  Crystallography,
however, many interesting and important details  will be given.
  The Unorganized Fluids comprise  the saliva, the bile, the sweat,
the urine, and  the gastric, pancreatic,  and lachrymal fluids; these 
THE  SALIVA.
241
several  fluids  especially deserve the name of secretions, since th^v
are elaborated by large and complexly organized glands.

                            THE SALIVA.
  The saliva is a peculiar fluid secreted by the parotid, sub-maxillary
and sub-lingual glands, from which it  is conveyed by certain ducts
into the mouth, where it  becomes  mingled with  the buccal mucus.
The amount of saliva secreted during the day is estimated at from ten
to twelve ounces;  during salivation, either spontaneous or induced
by  mercury, the quantity may exceed two  or  three quarts.  It is
worthy of remark, however, that in these latter cases the mercury has
never been  detected in the saliva.
  Mitscherlich* made the following observations  on a person having
a salivary fistula, and in whom the  saliva could be  collected directly
as it flowed from Steno's duct.  He found that there was no flow of
saliva while the muscles of mastication and of the  tongue were in
complete repose, and all nervous excitement avoided.  He observed,
also, that during the  acts  of eating and drinking, especially at  the
commencement, the secretion wras most abundant, and in proportion
to the stimulating nature of the food and the degree to which it was
masticated.   From two to three  ounces of saliva flowed  from  the
duct in the  course  of twenty-four hours.
   The solid constituents of the saliva are composed of fat, ptyalin,
watery and spirituous extractive matters, a  little albumen, certain
salts, a trace of sulphocyanogen, mucous corpuscles, epithelial scales,
and, lastly, corpuscles  resembling mucous globules, which have been
termed salivary corpuscles, and which  are  probably nothing more
than epithelial cells in progress of development.
   The salts of human saliva are, according to Mitscherlich, chloride
of calcium, lactates of soda and potash, soda, either free  or combined
with mucus, phosphate of lime, and silica.
   In certain pathological states Simon  detected in the  saliva acetic
acid, and a  considerable quantity of a substance  resembling caseine.
   The saliva is with difficulty to be obtained in a pure state, it being
generally intermixed with a greater or less quantity of buccal mucus;
now the normal reaction of the saliva is alkaline, that of mucus acid;
it therefore follows, the fluids in question being thus intermingled in
variable proportions, that the reaction presented by the fluid obtained
varies according to the relative quantity of each ingredient; thus.
                       * Rust's Magaz. vol. xl.
                               16 
2*2
unorganized  fluids.
 sometimes the saliva, when tested, will appear to be acid, alkaline, or
 neuter, and the same will be the case with the buccal mucus.
   The true reaction of the saliva, then, can  be ascertained only by
 obtaining it unmixed with  the  mucus of the mouth, and then testing
 it;  this may be effected by first washing the mouth with water,  and
 then applying the  test-paper to the saliva as it flows from the orifice
 of its ducts.
   The fact referred  to of the admixture of the two fluids, saliva and
 mucus, will serve to explain  why test-paper, applied  to the  upper
 surface of the tongue, exhibits frequently an acid reaction, while that
 placed beneath it manifests the presence of an alkaline  fluid.
   In morbid states the  normal  reaction of the saliva may undergo  a
 complete  change, and  it may  become either neuter  or acid:  this
 alteration has been especially observed to occur in deranged condi-
 tions of the stomach, in acute rheumatism, in cases  of salivation, and,
 according  to  Donne\ in pleuritis, encephalitis,  intermittent  fevers,
 uterine affections, and amenorrhea.
   Acid saliva doubtless exerts  a very injurious effect upon the teeth.
   The admixture of the saliva with mucus is readily shown by means
 of the microscope, which reveals  the presence of  mucous epithelial
 scales  in  all stages  of their development; as the scales found in the
 sweat  are  derived from the desquamation  of the epidermis, so  are
 those of the saliva and mucus from that of the epithelium.
  The saliva, as well as the sweat, yields  on evaporation crystals of
 the various salts referred to in the  analysis.
  Blood corpuscles are sometimes present  in the saliva and mucus;
 these proceed usually from the gums.
  The uses of the saliva in the  animal economy  are classified by Dr.
 Wright as follow:
  Active.—1. To  stimulate the stomach and excite it to activity by
contact.   2. To aid the digestion  of food by a specific action upon
the food itself.   3. To neutralize any undue acidity of  the  stomach
by supplying a proportionate alkali.
  Passive.—1.  To assist the  sense  of taste.   2.  To favour  the
expression of the voice.  3. To clear the mucous membrane of  the
 mouth, and to moderate thirst.

                            THE  BILE.
  The bile, like the unorganized fluid  already described, presents but
little of interest to the microscopist in its normal state. 
THE  SWEAT.
243
  It happens, however, occasionally, when it has been retained in the
gall-bladder for a long time, in consequence of which it has become
inspissated, that it does contain solid and coloured particles.
  These particles have been noticed by Scherer* and also by Dr.  H.
Letheby of the London Hospital, who was so considerate as to trans-
mit, for my examination, a  portion of  inspissated bile, containing
them, as also plates of cholesterine, in great numbers.
  The  bodies in question consist of two parts, an external colourless
investing portion, and an internal coloured and granular matter; this
disposition of the colouring matter  imparts to them the aspect of
" pigment cells," which, in  fact, Scherer considers them to be.
  There are but three kinds of cells, which, if cells at all, they could
be by any possibility,  viz:  liver,  epithelial,  or  pigment cells.   Now,
they are certainly neither of the first  two  mentioned, as  may be
inferred from the dissimilarity of size, appearance, and structure with
these;  and  they are as surely  not  "pigment cells," because such
structures do not enter into the organization of the liver.
  It is, then, conceived  that these cell-like bodies are not true cells,
but are to be regarded as masses of concrete mucus, enclosing more
or  less biliary colouring matter;  the great  differences  observed in
their form, size, and general appearance, are all opposed to the notion
of their being definitely  organized cells.
  The  meconium of  infants very  generally contains  the  cell-like
bodies described, together with intestinal mucus, cuneiform epithelium,
and occasionlly cholesterine in a crystalline form.

                            THE SWEAT.
  The  sudoriparous glands, distributed over the whole surface of  the
body,  constantly  secrete a very considerable quantity of  watery
fluid: this fluid passes off usually in the form of an insensible vapour;
in some cases, however, as under high external temperature, active
exercise, and in certain stages and forms of disease, it collects on  the
skin in  the form of drops, which, in drying  up,  deposit  their solid
constituents over the whole extent of the cutaneous surface: it is
then more particularly termed sweat.
  Many attempts have  been  made to determine  the amount of fluid
passing off by the skin;  the average quantity, according to Seguin
amounts to  about twenty-nine ounces of fluid, the maximum to five
* Untersuchungen, &c, p. 103. 
244                unorganized  fluids.

pounds, and the minimum  to  one pound,  eleven  ounces, and four
drachms.
   The  amount  of solid constituents  carried off with the fluid  is,
comparatively, very small, not exceeding in the twenty-four  hours
seven or eight scruples; the remainder being merely water, retaining
in it carbonic acid and nitrogen, the quantity of the former gas  being
increased by  vegetable diet,  and  the  amount of  the  latter by an
animal regimen.
   Simon has established the existence, in normal sweat, of—■
   1. Substances soluble in ether: traces of  fat, sometimes including
butyric acid.
   2. Substances  soluble  in  alcohol: alcohol extract, free lactic  or
acetic acid, chloride of sodium, lactates, and acetates of potash and
soda, lactate or hydrochlorate of ammonia.
   3. Substances  soluble  in water:  water extract, phosphate of lime,
and occasionally an alkaline sulphate.
   4. Substances  insoluble  in  water: desquamated epithelium,  and,
after the removal of the free lactic acid by alcohol, phosphate of lime
with a little peroxide of iron.

   The quantity  of fluid  exhaled is subject  to very great variations;
thus, it is increased by a dry and light atmosphere, while it is dimin-
ished by a damp and dense condition of the air.   It is at  its minimum
at and  immediately after meals, while it is at its maximum during the
actual period of digestion.  The cutaneous perspiration  is in antago-
nism with  the urinary secretion;  thus, an excessive  secretion of
urine diminishes  that of the skin, and a diminution of the activity of
the kidneys  is usually followed by  an augmentation  of that of the
sudoriparous glands.
   But little of interest, in a microscopic  point of view, attaches to
this fluid; the only solid organic constituent  contained in it being
detached scales of epidermis, which is  ever  undergoing a process of
destruction and renewal;  these  scales, therefore, do not  form part of
the sweat, but become mixed up with it in a  secondary manner.
   The copious formation and discharge of the cutaneous fluid which
occur under certain circumstances, thus do not merely afford a relief
to internal organs, but serve, also, by detaching and  washing away
the older and useless cells, to cleanse the epidermis, and to render this
more efficient as an evaporating surface.
   The crystals formed on  the  evaporation of the sweat, in states  of 
THE  URINE.
245
 health and disease, have been  but little studied; it is probable that a
 knowledge of them would lead to the discovery of some facts of interest.
   The cutaneous fluid, it is known, is in health acid;  there are some
 situations, however, in which it is  constantly alkaline, as in the axillae,
 about the genital organs, and between the  toes; this, probably, arises
 from its admixture with the secretions of the small  follicles which
 are situated in those parts.
   The  sweat, like the  urine, is to be regarded  as a cleansing fluid,
 the  system  being through  it relieved  of  certain surplus and effete
 matters.
   The pathology of the sweat is but little  known; albumen has been
 observed in  it by Anselmino, in a case  of febris  rheumatica, and
 Stark states, that it may be met with in the sweat in  gastric, putrid,
 and hectic diseases, and also on the approach of death.   The amount
 of acetic acid, ammonia, and the  salts, may all  be increased.  Uric
 acid and quinine have been found in the sweat, the latter preparation
 being of course at the time administered medicinally.

                             THE  URINE.
   Few fluids have been more studied  of late years  by the micro-
 scopist  than  the  urine; this has arisen from the elegance of form,
 variety of composition, and important character of  the numerous
 crystalline deposits which are formed  in  it in states of health  and
 disease, and which can be  satisfactorily determined only by the aid
 of the microscope.
   The great advantage of  the application of the microscope over
 that of chemical tests to the study of the urine  is, that  the indications
 which it affords are not merely certain, but also prompt and facile,
 while the results  obtained through the agency of chemistry, although
 not less certain, are often tedious and difficult.
   The description of the various crystals  formed in the urine is
 reserved for  another  occasion;  in this place will be noticed only the
 organic constituents which occur in normal and abnormal urine.
   In  order that  the pathological  alterations to which  the  urine is
liable may be more clearly understood, it  will be advisable,  first, to
describe the appearance and  the constitution of healthy urine.
   Healthy urine, when  first passed, is  a  limpid  fluid of an amber
colour, emitting  a peculiar odour, exhibiting an acid reaction,  and
having a specific  gravity of about  1011.
   Abandoned to  itself, it soon loses  its limpidity, becomes troubled, 
246
UNORGANIZED FLUIDS.
and putrefies more or less quickly, according to its chemical consti-
tution and the state of the temperature.
  The following is  Berzelius'  analysis of healthy urine, and  with
which  all other subsequent analyses have been found to agree to a
very considerable extent: 1000 parts contained—
Water,	-	933•00	
Solid residue,	-	67 00	
Urea,	-	3010	
Uric acid,	-	100	
Free lactic acid, lactate of	ammonia, alcohol		
and water extract,	-	1714	
Mucus,	-	0 32	
Sulphate of potash,	-	3 71^	
Sulphate of soda,	-	316	
Phosphate of soda,	-	2 94	Fixed
Biphosphate of ammonia,	-	165	> salts, 1529
Chloride of sodium,	-	445	
Chloride of ammonium,	-	150	
Phosphate of lime and mag	nesia,	100	
Silicic acid,	-	0 03.,	
  It will be seen from the above analysis that healthy urine does not
contain the nitrogenized principles albumen, fibrin, or caseine, which
are encountered so frequently in urine voided in disease.
  The only solid organized constituents which are constantly encoun-
tered in healthy urine, are mucous corpuscles and epithelial  scales;
these do not form  part  of the urine, but belong  to the structure of
the mucous membrane of the bladder and urethra, and both of them
may be detected  with the greatest facility by the microscope.   On
account of their  greater specific gravity, they subside at the bottom
of the vessel containing the urine, where they may, at most times, be
procured for examination.
  Occasionally, however, in the urine of man,  under the circum-
stance already referred to in the article on the semen, the sperma-
tozoa are present in the urine also.
PATHOLOGY OF THE  URINE.
  The organic principles contained in diseased urine may be divided,
firstly, into those which are usually encountered in  that fluid in a 
THE  URINE.
21?
 state of  solution, but  which  do yet,  under certain circumstances,
 assume the solid form; and, secondly, into those which, being definite
 organisms, occur only in a solid condition.   Albumen, fibrin, caseine,
 and fat, belong to the first, and the  blood and pus corpuscles to the
 second division.
                        Albuminous Urine.

   Albumen is frequently present in the urine in disease; it has  been
 noticed to occur especially in Bright's  disease of the kidney, and in
 the urine passed after scarlatina.
   If the albumen be present in any considerable quantity, nitric acid
 or bichloride of mercury will cause a precipitate, and the urine will
 become  turbid on  the  application of heat,  and deposit flocculi of
 coagulated albumen.
   The colour, specific gravity, and  reaction of  albuminous urine are
 various;  thus, it may be  either light or dark coloured, it may be of
 high or  low  specific  gravity, it may exhibit either an acid or an
 alkaline reaction, or it may be neutral.
   When  the albumen is  small in quantity, heat is the most efficient
 test for its detection; it is only when the urine manifests a decided
 alkaline reaction, that nitric acid is preferable, the albumen being
 held in solution by the free alkalies.
   Urine may, however,  become turbid from the application of  heat,
 even when no albumen is present;  this arises from precipitation of
 the earthy carbonates;  in these instances, the addition of nitric acid
 will immediately disperse the cloudiness, and the reapplication  of heat
 will not occasion any further precipitation.
   Dr. G. O. Rees has observed that the urine  of persons who  have
 been  taking cubebs or balsam of copaiba is rendered turbid by nitric
 acid,  although it contains  no  albumen;  this urine,  however, is not
 affected by heat.
   From  the  facts  contained  in the two  preceding  paragraphs, it
 follows that  a precipitate might possibly ensue on the application
 of heat, and  by the addition of  nitric  acid, and yet no  albumen be
 present in the urine.
   If the precipitate yielded by nitric acid, added to urine impregnated
with the active principles of cubebs or copaiba, be examined with the
microscope, it will be found to consist of minute oil bubbles, which
are of course readily soluble in ether. 
248
UNORGANIZED  FLUIDS.
                         Fibrinous Urine.
   Fibrin  has been encountered in the urine independently  of  the
other constituents  of the blood: Zimmerman* has described seven
cases of fibrinous urine.
   Such  urine, if the fibrin  existed  in  it in any quantity,  would
coagulate or form a clot.
   It is  necessary in these cases not to confound mucus with fibrin;
the former, under  the microscope, exhibits the well-known mucous
corpuscles,  while the latter  appears  either  filamentous  or  simply
granular.
                           Fatty Urine.
   The urine may  contain  fat,  either separately  or  conjointly with
albumen, or with caseine, and probably also sugar: the urine holding
fat in a free state  may  be called fatty;  that in combination with
albumen, chylous;  and lastly, the urine in which fat  occurs in con-
nexion with caseine and  sugar may be denominated milky urine.
   Fatty urine has been observed to occur frequently in persons labour-
ing under phthisis;  the fat, as the liquid  cools, forming a thin pellicle
on its surface, the nature of which may be at once ascertained  by the
microscope, which, if it  be really fatty, will reveal the  presence of
innumerable fat globules.
   Cases have been  recorded in which the quantity of fat has been so
considerable that it could be detected with the naked eye.

                         Chylous  Urine.
   Chylous urine  is a white semi-opaque fluid, and contains both  fat
and albumen; the former may  be  detected by means of the micro-
scope, and the latter will be coagulated by heat, by nitric acid, and
the bichloride of mercury.   Examined  microscopically, the coagu-
lated albumen exhibits a  granular texture.
   This form of urine has been observed principally in cases  of gout.

                          Milky Urine.
   True milky urine is of very rare occurrence, there being but two
or three well-authenticated cases of it recorded; urine containing the
constituents  of chyle  having  doubtless  been described, in  many
instances as milky urine.

  * Zur Analysis und Sunthesis der pseudoplastischen Prozesse, Berlin, 1844, p. 129. 
THE  URINE.
249
  The fat in milky urine occurs in combination  with caseine, and
probably with sugar also.
  The fatty constituent may be detected as in the previously-decribed
urines, the fatty and the chylous, by means of the microscope, and the
caseine will  be precipitated by the addition of a little acetic, dilute
sulphuric, or hydrochloric acid, the  flocculi of which, examined micro-
scopically, will exhibit a granular, and even in many cases a globular con-
stitution ;  they will contain also a greater or less number of fat globules.
  Urine  containing caseine in solution may be distinguished from
albuminous urine by the  application of heat, which in the latter will
occasion a precipitate, none being formed in the former, unless, indeed,
a considerable  quantity  of nitric  acid be also present in the urine,
when a temperature of 104° Fah. will be sufficient to occasion the
precipitation of the caseine.
  It is not to be  supposed, by the use  of the term milky urine, that
the milk, as such, ever  exists  in  the urine, and that  it finds its way
there from the  mammary gland by metastasis; the utmost that is to
be inferred, from the existence of the principal elements of milk in the
urine, is, that the kidney,  in place of the mammary gland,  has  sepa-
rated those elements from  the blood.

                 Excess of Mucus  in the  Urine.
  In catarrhus vesica, an affection to which old persons are particu-
larly liable, mucus is secreted in considerable quantities, and is voided
with the  urine.
  This mucus subsides  to the  bottom of the vessel,  is semi-opaque,
thick, and ropy;  examined with the  microscope, mucous corpuscles
and epithelial scales are encountered in it.
  In those cases  in which the urine is very alkaline, the  mucus is
observed  to  be particularly tenacious  and  thready;  this  condition
results from the action of the free alkalies contained in the urine upon
the constitution of the  mucus.

                       Blood in  the  Urine.
  Blood is frequently contained in the urine, and voided with it; thus,
it is frequently encountered, in greater or less quantity, in the follow-
ing cases: in inflammation of the kidneys, in injuries of those organs,
or of the bladder itself, in cases of stricture from the introduction of a
catheter, from the passage of renal  or urinary calculi, and, lastly, from
chronic disease of the kidneys and bladder. 
250
UNORGANIZED  FLUIDS.
   The  best  test of the existence  of the blood  in  the  urine is the
detection of the blood corpuscles by the microscope; blood, however,
may exist in the urine, and yet no corpuscles be detected,  these having
been dissolved by the acids of the urine.   Failing, however, to detect
the blood discs, if blood  really be  present,  then  the albumen, fibrin,
and hematin  will  still remain, and  may be  distinguished by suitable
reagents.
   From the  colour of urine, no  conclusion can  be  formed as to the
existence of  blood in it,  as urine  of a deep blood-colour is some-
times met with, which  on examination is found  not to  contain any
trace of blood.

                       Pus in the Urine.
   It has already been stated in these pages that no absolute distinction
exists between  mucus and pus;  and, therefore, it follows that it is in
most cases impossible  to determine, with any degree of certainty,
whether pus exists in the  urine or not.
   If, however, the  sediment rendered with the urine want the tenacity
of vesical mucus,  and  contain the granular corpuscles  common  to
mucus and pus, there is reason to suspect that the fluid in question is
really purulent.
   The diagnosis will, however, be greatly assisted  by reference to the
history  and symptoms of the case;  thus, if there be rigors and hectic
fever, the probability of the existence of pus will be  much strengthened.
   There is one circumstance which requires to  be mentioned, and
which greatly increases the difficulty of discrimination between mucus
and pus.  In some cases  of purulent urinary deposits, the urine  is
alkaline; now, the effect of the action of alkalies on pus is to convert
it  into a transparent  and tenacious substance in every respect resem-
bling mucus, and which, therefore, cannot be distinguished from it.

   There are but few details interesting to the microscopist connected
with the Gastric, the Pancreatic, and the Lachrymal fluids;  it will
therefore, be unnecessary  to treat of them at any  length.   It is to the
chemist  and physiologist  chiefly  that the  gastric fluid is interesting.
They all, however, but especially the gastric  and the lachrymal secre-
tions, contain mucous corpuscles and epithelial  scales, derived from
the desquamation of the epithelium of the surfaces by which they are
secreted, and over  which  they pass. 
THE  URINE.
251
  Obs.—At page 135, the opinion is attributed to Mr. Addison, that
the white  corpuscles of blood,  mucus, and pus contain filaments;
whereas it  would appear, from a closer examination of the text, that
the statement of that gentleman only goes to the  extent of asserting,
that the fluid enclosed in those corpuscles  resolves itself in its escape
into the filaments, of which the fibrinous portions of blood, mucus, and
pus are under certain circumstances observed to be constituted. 
252
UNORGANIZED  FLUIDS.
                               URINE.
  [In the pathology of the urine, the microscope has now become of equal
value with chemistry;  a proper consideration of this whole subject would
require a volume of  the size of the present one, and therefore it is not here
attempted.  For reference on this  subject, especially on the microscopical
characters of urine, the student may consult "Simon's Chemistry of Man,"
" Bird on Urinary Deposits;" " Practical Manual on the Blood," by John Wm.
Griffith; "On the Analysis of the Blood and Urine," by G. Owen Rees;
"A Guide to the Examination of Urine," by Alfred Markwick; "Frick on
Renal Diseases;"  "Prout on do."
  Those who wish to study the pathology of the  urine, with  the microscope,
will find the following hints useful.   After allowing the urine to stand for a
little time, more or less  sediment will take place.  This is  to be drawn  up
by means of a pipette, and a drop placed on a plain glass slide, and covered
with thin  glass.  It  is then ready  for examination,  first with a one-fourth
inch object-glass,  and  afterward with a one-eighth.   This high  power is
necessary to recognise the  presence of blood, mucus, or pus corpuscles, or
the minute crystals of oxalate of lime.
  When the presence of an undue quantity of  lithate of ammonia is sus-
pected,  the test-tube or  other  glass  vessel containing the  urine must  be
heated gently, when  the  supernatant  fluid, with the  lithate,  may be poured
off, or removed with  a pipette.   Most  of the urinary sediments can be well
preserved;  the most transparent,  such as oxalate of  lime, &c., are best
mounted in fluid.   For this they are prepared by being repeatedly washed
in distilled water, until  all  trace of gummy matter,  so often combined with
urinary deposits, is removed.  They are then placed  on a plain glass slide,
or in a thin glass cell, mixed with a little water by means of a pipette, and
the  water  allowed to evaporate.   A  drop or two of alcohol and water, of
Goadby's solution, or of the creosote-water, is to  be added, and the thin glass
cover applied  and cemented with gold size, care being  taken that no air-
bubbles are present.
  Other urinary deposits, requiring to be rendered more transparent, are
best  preserved  in  Canada  balsam.   The  deposit must  be well washed  as
before, and after being placed on the glass  slide, and the water allowed to
evaporate, must be mounted in balsam with  heat, as  directed in the chapter
on the  Preservation of Objects.  Certain deposits are best preserved in the
dry way,  such as uric acid, &c.
  Other sediments, and  these  are  chiefly salts, are best mounted in syrup,
made thick, and mixed with  a little  gum.  This is to be used in the same
way as the balsam  without heat,   and the sediment deposited in the thin
glass cell, or that made with  asphaltum or other cement.   Castor oil has
been successfully used as a medium for mounting urinary deposits.   In this
method, no heat is necessary.] 
PART   II.—THE   SOLIDS.
  The division of the various constituents of the animal fabric into
the two orders of Fluids and Solids, although a very ancient one,
is yet, to a certain extent, arbitrary and artificial.   The truth of this
observation is rendered apparent on reference to the several  fluids,
the description of which has just been brought to a  conclusion, and
all  of which contain  suspended in  them, either  as  essential  or  as
accessory elements, various solid and organized particles:  the  liquid
portion  of some of these compound fluids exhibiting also a distinctly
organized constitution; as, for example, the liquor sanguinis  and the
fluid parts of mucus  and of pus.
  The distinction referred to is  not,  however, without its use, and is
sufficiently well founded to serve the purposes of classification.
  Of the Solids themselves it is unnecessary to make any formal sub-
divisions :  they will simply be treated of in the order of their natural
relationship with each other.
  Thus, the various  solid structures  entering into the constitution  of
the animal  organism will be described  consecutively as follows, each
forming the subject of a distinct article: Fat, Epithelium, Epidermis,
Pigment Cells, Nails, Hair, Cartilage, Bone, and Teeth; the  vari-
ous Tissues, the Cellular, under which head Ligaments and Tendons
will  be  described, the Elastic, the Muscular, and the Nervous,
including the description of the  Brain and Nerves;  the Glands, Ves-
sels, Membranes; and, lastly, the Pathology of  the Solids, will  be
treated of. 
254
THE  SOLIDS.
                       ART.  VIII. —FAT.

  The transition from the fluids to  the solids would appear to be  a
very easy and natural one through the substance about to be described:
thus, fat bears an evident relation to both the former and the latter,
remaining during life in a soft  and semi-fluid state, and after  death
becoming hard and solid;  it is,  however, to  the milk globules among
the fluids that it manifests the closest  affinity, the fat  vesicles, espe-
cially those of early life, and the milk globules resembling each  other
in form, in  appearance, and in the manner  in which reagents act
upon them.
  Fat is made up of the aggregation of a number of globules or ves-
icles, which some deem to be true cells, and which are held in juxta-
position by intersecting bands of cellular tissue; these vesicles have
a smooth surface, semi-opaque  texture, and  they reflect the light in
the strongest manner.
  Contents.—The contents of fat vesicles usually present a homoge-
neous  appearance;  sometimes  nevertheless—as when undergoing
decomposition, and when they have been subjected to pressure—they
exhibit a granular aspect; these contents are  of an  oily nature, and
chemists have detected in the lard  of the pig the organic products,
oleine, stearine, margaric acid, a yellow colouring matter having the
odour and the nauseous taste of bile, and the chemical salts, chloride
of sodium, acetate of soda, and traces of carbonate of lime and  oxide
of iron.  It is probable that of  these constituents the presence of the
chloride of sodium depended on the mode of preparation of the lard.
  Form.—The form presented  by the  fat vesicles is various, but is
usually either globular, oval, or  polygonal.  The first shape is encoun-
tered in the  fat of young animals especially (see Plate XVIII. fig. l) ;
the second in that of adults (see fig. 2);  and the third in situations
where the fat is subjected  to considerable pressure, and on solidifica-
tion after death.  The fat vesicles of the pig are described as  being
elongated and kidney-shaped.  This shape, however,  is  of rare occur-
rence, and cannot be regarded as the ordinary and characteristic  form,
which  is most  generally more  or less spherical  or oval.  Raspail,
observing this exceptional form, was led to institute from it an  erro-
neous  comparison between  fat vesicles  in  general  and  the starch
granule. 
FAT.
255
  Size.—The fat vesicles of the adult are usually several times larger
than the solid corpuscles of any of the fluids described—the blood,
mucus, and milk;  the  size of the  fat vesicles in any given quantity
of fat is not uniform;  but, like the globules of milk, varies exceedingly,
the dimensions of the larger vesicles surpassing several times those
of the smaller.
  One exceedingly interesting law has been observed in reference to
the size  of  fat vesicles;  thus, it  has been  ascertained  that their
average magnitude increases from  infancy up to adult age: in  accord-
ance  with this  law,  the fat  cells of  an infant will be  found to be
several  times smaller than those of a full-grown person, and those of
a child again of an intermediate size.   This law will be  apparent from
an examination of the figures given.   (See  Plate XVIII.)
   Colour.—The colour of fat is  subject to considerable  variations,
but it usually exhibits a tinge, more or less deep, of yellow.   The fat
of young animals is  usually of a  lighter colour than that of the full-
grown and aged;  this may be seen by a comparison of the fat of an
infant with that of an adult, or of the fat of the calf with that of the
ox;  in the former it is almost white, while in the latter it frequently
exhibits a deep and golden hue.  The differences of colour referred to
doubtless denote differences in the relative proportion of the different
constituents of fat.
  In  some animals, also, fat of various bright colours is encountered,
especially in  Birds, beneath  the skin of the beak and of  the  feet;  in
the Crustaceae and in some of the Reptilia.  In the Triton, the fat is
of a deep orange-colour, approaching to red.   The coloration of the
iris of birds  depends, according  to  Wagner, upon a fat which is
accumulated in drops, and perhaps also in cells.
  Consistence.—The  consistence of fat  is  different in different
animals,  and also varies  in  accordance  with the  temperature; thus,
the fat of the pig is softer than that of the  ox or sheep; that of the
human subject is intermediate between  both in its consistence, and
all kinds of fat are harder in cold than  in warm weather.   The varia-
tion in the solidity of fats depends upon the amount of stearine and
oleine which they  contain; the hard fats containing a greater quantity
of stearine than the soft fats, in which the oleine is greatest.
  Structure.—Most observers agree  in assigning to each fat vesicle
a distinct investing membrane, notwithstanding which fact the proofs
adduced by  them  of the existence of such a structure  are  by no
means so decisive as to render such a conclusion any  thing  more 
256
the  solids.
than doubtful:  thus, micrographers, hitherto, have been unable  to
demonstrate the presence around normal fat vesicles of an enveloping
tunic, but have  been contented to rest their opinion upon the indirect
and uncertain evidence to be derived from a knowledge of the action
of reagents;  upon testimony,  in fact, analogous to that upon which
Henle and Mandl  decided in favour of the existence of a membrane
surrounding the milk globule.
  Schwann, indeed,  states that he found the membrane of the fat cell
to be almost as thick as the blood globule of man in an infant affected
with mollities ossium*
  Henle also has observed around the obscure periphery of  a fat cell
a strait and  clear  band, but could not  assure himself that  this was
not the result of an optical illusion.f
  The above are the only trustworthy observations of a direct char-
acter recorded in proof of the existence of a distinct tunic to the fat
vesicle, and they are evidently not of a satisfactory or decisive nature.
  The indirect testimony procured from a knowledge of the action of
reagents is as follows:  Ether is stated to render the contents of the
fat vesicle fluid and transparent, without, at the same time, diminishing
its size, as  is proved by the  fact that on the resolidification  of  its
contents, the vesicle presents the same form and dimensions as at first.
  Again, acetic acid, according to  Henle, acts upon  the fat vesicle
as upon the milk globule, destroying the membrane in different places;
it permits the escape of a number of globules of oil or grease, which,
like pearl-drops, remain attached to the larger vesicle.
  Ether, however, produces other effects than those usually described,
and  which  are mentioned  above;  thus,  when applied to the fat
vesicles of the pig, many of them will be seen  to burst, and to collapse
frequently to less  than the  fourth of their original size, losing, at the
same time, all definite form; and, in proportion as the vesicle collapses,
one large circular  drop, or  two or three smaller ones, will  be  seen
gradually to form  around and envelope the shrunken vesicle, which
is, however, never entirely dissolved.
  There are other observers  again, as Schwann and Henle,  who
consider that fat vesicles are not merely provided with an envelope,
but that they are true cells, possessing both cell wall and nucleus.
   Thus, Schwann noticed in the wall of the fat vesicles of  the child
already  referred  to, a nucleus  of  round  or  oval form,  sometimes
flattened, and sometimes  not so.
      * Mikroskopische Untersuchungen, p. 140,       f Anal. Gen. p. 422. 
FAT.
25?
   Furthermore, Henle writes, "very frequently the wall presents a
salient point on some  part of its extent, and  in that position exists a
nucleus, or  a trace  of a  nucleus.  Sometimes there are two nuclei,
and in very many cases they cannot  be observed at all."*
   Again, Mandl has made the observation in  examining the fat tissue
of young rabbits, and especially  in  taking the little masses  of fat
which lie along the vertebral column in the interior of the pectoral
cavity, that the vesicles appear but half filled,  and that they consist of
two parts, an inner one conveying the  aspect of a drop of oil, and an
outer membranous portion.f
   Such  are the facts hitherto recorded in favour of the presence of a
nucleus  in the fat vesicle: it will be seen that although they are more
definite and satisfactory than those adduced in proof  of the existence
of an investing membrane, yet that they are scarcely in themselves
sufficient to set at rest the question of its cellular  nature.
   The observations, then, cited above,  while  they fail to demonstrate
sufficiently  the true  organization of the fat vesicle, yet  render it
extremely probable  that it is really cellular.   In favour  of this view,
a few additional  observations have  occurred to myself,  which  are
conclusive on one of the two  debated points of the organization of
the fat vesicle.  The first have reference to the outer membrane.   If
a thin slice of  any  of the softer  fats  placed between  two  plates of
glass  be pressed  firmly,  though  not With too great violence, and
subsequently be examined with the  microscope, it will  be seen that
the vesicles  have not run into each  other,  but  still preserve their
individuality.             \
   Again, ether applied to  the fat vesicle does  not entirely dissolve it;
even when it causes  it  to burst and collapse, a  residue always remains,
and this  probably is membranous.
   Furthermore, if a  thin slice of fat be placed between two plates of
glass, and having been forcibly compressed,  be examined with  the
microscope, it will be seen that  some of the  vesicles have  burst,
discharging a portion  of their  contents, the membrane  of the  fat
vesicle then becoming visible, and declaring  its existence by certain
folds and markings, into which  it falls on the escape of its contents,
and by the jagged outline  of the  rent  through which those contents
passed.   (See Plate XIX. fig. 2.)
   Finally, decomposition  produces an  effect  somewhat analogous to
that occasioned by pressure; the fat vesicles burst, and  their fluid
     * Anal.  (ir.n. p. 422.              f Analomie Micmscnj>iqif\ p. 141.
                               17 
258
THE  SOLIDS.
contents escape, leaving the membrane in most cases entirely empty,
and which, as well the aperture in its parietes, may be easily detected
with the microscope; the soft contents of the vesicles break up, and
resolve themselves  into globules  of an  oil-like appearance.  (See
Plate XIX. fig. 4.)
  The second set of observations relate to the nucleus.
  If a thin slice of the fat of the pig be pressed as before between
two  slips  of glass  with a moderate degree of pressure, and  then  be
submitted to the  microscope, in  very many of the cells will be seen
a dark nucleus-like body. This experiment will not, however, always
succeed.   (See Plate XIX. fig. 1.)
  A body of a similar description, but of a more defined form, is very
frequently encountered in the decomposing cells of marrow fat; this
nucleated condition of the cells preceding their rupture.  (See Plate
XIX. fig.  3.)
  Again,  in some fat  cells  contained  in a small  encysted tumour
removed  from  over the nasal bones, and kindly sent to me  for
examination by W. H. Ransom, Esq., of University College Hospital,
(to  whose zeal and intelligence  I  am indebted for many interest-
ing specimens of morbid structure,) nucleoid bodies were distinctly
visible even without pressure, although they became more apparent
after a gentle degree  of compression had been  applied.  (See Plate
XIX. fig. 6.)  The apparent nuclei in the cases related differed from
each other somewhat, being more defined  and  darker in the two
latter than in the former; the cells themselves too were not identical
in appearance;  thus, the  margins  of  those of the  pig  and of  the
human marrow fat were smooth and distinctly defined, while those from
the tumour were less regular and distinct.  (See Plate XIX. figs. 1.3.6.)
  Now these  nucleus-like  bodies in the several  cases  mentioned,
although occupying the position  of nuclei and presenting the appear-
ance of such, it is very possible were  not in reality true nuclei; it
seems to me that their formation might be accounted for without any
reference to a nucleus.  Thus with respect to the nucleod  bodies  in
the cells of the pig produced by pressure, their formation  might  be
explained as follows:  the mutual compression of the fat vesicles upon
each other would tend to occasion a condensation  of the semi-fluid
contents  in the centre of each, and in  this way the appearance of
nuclei would be produced.
   Again, the semblance of a nucleus in  the decomposing cells mi<mt
be  supposed to depend upon the partial escape by endosmosis  of  the 
                              FAT.                           259

contents of those cells, the portion remaining in them representing a
nucleus merely from the position occupied by it in the centre of the cells.
  The formation of the nucleated bodies in the third case would seem
to point to and to require a different explanation.   Decomposing fat
frequently  exhibits  a crystalline  arrangement;  now, it is  conceived
that the outer part of each vesicle had  become  softened and  broken
down,  in consequence of commencing decomposition or of disease,
preparatory to its  assuming  the  crystalline form, the central part at
the same time remaining unaffected.
  It will be seen that the preceding observations, in relation to  the
presence of a nucleus in fat vesicles, are not decisive, although they
add weight to those of anterior  observers, and render it still more
probable that  they are really nucleated  cells.
  The  facts adduced, however, in reference  to the existence of an
investing membrane are quite conclusive.
  On the vesicles of decomposing human fat, it is a common occur-
rence  to meet  with stelliform  figures, each being composed of a
number  of delicate  striae radiating from a central point.  On  the
smaller vesicles but a single figure of this description will usually be
met with, but on the larger there may be three  or four.  When but
one is present, it usually covers about a third  of the surface of each
vesicle.  (See Plate XIX. fig. 5.)
  Henle* observes of these that they might be metamorphoses of the
nuclei  of the cells;  "nevertheless," he says, "they have more analogy
with crystalline deposits."
  The occurrence  of two, three, or four of these on the same cell is
opposed  to the idea of their connexion with  the nuclei; and  the
observation of Mandl, who noticed their formation on butter,  is con-
clusive on  this point.f
  Vogel,J  as also Gerber,§ regard the figures in question as  groups
of crystals  of margaric acid.
  Distribution.—The fat vesicles are distributed in groups, which lie
near to and follow the course of the blood-vessels.   (See Plate XVIII.
fig. 1.)   This arrangement is particularly evident in  the  mesentery
and omentum, and may be compared to that of a bunch of grapes, the
fat vesicles representing the grapes, and the vessels  the stalks  of the
bunch:  in  one particular only does the comparison fail;  thus, each
       * Loc. cit. p. 423.               f Anat. Mic. f. 143.
       \ Anleitung zum Gebrauche des  Mickroskops, p. 289. tab. 111. fig. 2.
       § Gerber's General Anatomy, translated by Gulliver. 
260             .         THE  SOLIDS.
grape of the bunch receives and is  attached  to a separate pedicle,
which is not the case with the fat vesicles, although one observer has
asserted that a separate vessel is distributed to each vesicle.  The groups
of fat vesicles occurring in young animals, in which each globule is
circular, may be compared to heaps of shot piled up upon each other.
  In those situations in which the fat occurs in thick and dense masses,
the arrangement referred to is somewhat different.   The  fat vesicles
are still parcelled out  into groups by means of intersecting cellular
bands; but the several groups lie in close contiguity, instead of being,
as in the former case, separated from  each other by distinct intervals.
Throughout these masses, too, but few blood-vessels are distributed.
  The intimate arrangement of the fat vesicles having been thus
briefly sketched, it remains to describe the general distribution of fat
throughout the body.
  In man, fat is developed principally in the loose cellular tissue; it
is encountered forming a layer of variable thickness in that which is
situated immediately beneath the skin; in  the serous membranes, as
in the omenta, the mesenteries, and  the  epiploa; on the  surface of
the heart, and around the kidney.
  In  certain situations the sub-cutaneous fatty layer experiences an
increased development designed  to fulfil certain peculiar intentions;
thus, in the  soles of the feet, the palms  of the  hands, in  the female
breast, in the  region of the pubis, and over the glutei muscles, espe-
cially over those of the Hottentot women, fat is developed usually in
considerable quantities.
  This  superficial layer of fat is also generally thicker  in children
and in women than in men.
  Again, there are other peculiar situations in which fat is almost
invariably encountered, as in the orbit, in the articulations, where it
constitutes  the glands  of Havers,  in the shafts of the  long  bones
forming  the marrow,  in  the  vertebral  canal,  and in many other
localities where vacancies  occur which require to be filled up.  The
marrow differs only from ordinary fat in that the cells composing it
are more circular, with but little admixture of cellular tissue.
  On the other hand, there are situations in which, under no circum-
stances,  is fat developed, as in the eyelids,  in the  axillee, between
overlapping  muscles, and in the genital  organs.
  Quantity.—The amount of fat varies greatly in different species of
mammalia,  in different individuals of the same species,  and  in the
same animal at different times. 
FAT.
201
   Thus, certain animals  seem  to  have a peculiar aptitude  for  the
formation of fat, as the pig.
   Again, the various members of one family are sometimes observed
to be remarkable for the constitutional predisposition exhibited to the
formation of fat.   Again, other families are met with equally remark-
able for their indisposition to fatten.
   Lastly, in  some animals the  fat accumulates at particular  periods
in greatly increased quantities, as in  the hibernating mammalia, and
in the larvae of insects.  In man  the fat usually undergoes  an aug-
mentation after the meridian of life has been passed.
   Castration peculiarly predisposes the system to the formation of fat.
   Occasionally, also,  fat is secreted in vast and abnormal  quantities:
where this augmentation is general, it constitutes the diseased condi-
tion of obesity; and  where it is only partial, it gives rise to tumours,
often of great magnitude.
   In general, a certain degree of fatness argues a healthy and vigorous
condition of the system, while  its excess or inordinate accumulation
denotes either a degree of weakness of constitution or a peculiar and
unexplained state of the system.
   Disappearance.—Of all the solids in the body, fat is developed and
destroyed with the greatest rapidity:  in illness, it disappears with sur-
prising quickness, and is formed again, under the influence of recovery,
with almost equal celerity.
   The exact changes which occur during the disappearance of fat
are  unknown;  whatever  they may be, they  doubtless  affect each
individual fat vesicle  throughout  the body, and their nature being
ascertained in a single cell would serve to explain the disappearance
of fat over the entire  body.   It is uncertain whether the contents of
the vesicle disappear, the membrane remaining, or  whether both  are
effaced together.  B6clard says that the fat vesicles themselves disap-
pear.*  Hunter, on the contrary, assures us that they may be distin-
guished even when they are empty.f  Gurlt states that they contain
serosity in place of grease in lean animals. J
   The immediate cause of the disappearance of fat most probably
depends upon interrupted nutrition ;  the contents of the cells escaping
through  their walls become absorbed by  the  lymphatics, and thus
removed into the circulation.   This view is supported by the observa-
  * Analomie Genirale, p.  163.
  f" Remarks  on the Cellular Membrane," in Med. Obs. and Inq., vol. ii.,Lon., 1757.
  I Physiologie, p. 20. 
262
THE  solids.
 tion of Henle, who states that, after repeated losses of blood, the quan-
 tity of grease in the blood augments considerably, on the  surface of
 which it is often seen swimming as a cream or pellicle.
   Uses.—The uses of fat are manifold  and important.
   1st. It serves to impart softness to the texture of the skin.
   2d.  It adds grace and symmetry to the outlines of the body.
   3d.  In certain situations, as in the  soles of the feet, in the palms of
 the hands, and over the glutei muscles, it serves as a protection against
 the effects of pressure.
   4th. Being a bad conductor  of caloric,  it prevents the  too rapid
 dissipation of the heat generated in the system.
   5th. It is  to be regarded as a reserve  store of nourishment set apart
 by the system  during the  period of  its  health  and strength,  and
 designed to meet certain exigencies, when the inherent powers of the
 constitution  are called  into requisition, as in  times of hunger  and
 sickness.
   Distinctive Characters of Oil Globules.—The contents of fat ves-
 icles are, as  already stated, of an oleaginous nature, which, when they
 escape from the vesicles, assume the form of oil drops; these are often
 met with in the various fluids and solids of the system apart from the
 fat vesicles,  from which  it is necessary  that they should be  discrimi-
 nated.  There are several  characters by which oil globules may be
 distinguished  from true  fat vesicles;  thus,  they are of a fluid nature,
 are usually  perfectly spherical,  and,  on account of their fluiditv, in
place of being globular, are generally flat;  they are  seen sometimes
to alter their shape,  as  when they roll over on the surface of the
object-glass, or come  in contact with obstacles; they reflect the light
less  powerfully, and,  lastly, the  slightest degree of pressure causes
them to coalesce.
   There is but little probability of confounding oil globules with air
bubbles;  these have a different colour, reflect the light differently, and
are perfectly globular.
   See Appendix, page 538. 
FAT.
263
                                  FAT.
  [No farther hints are necessary on the preparation of fat for examination,
or the use of reagents while under examination, than those given in the text.
In order to display the  blood-vessels of the fat  vesicles, their injection is
necessary.  These vessels are represented in Plate LXX., fig. 3, and their
existence is referred to in the Appendix, page 538.
  These vesicles can only be injected when the injecting material  is very
fine, and the operation is perfectly successful.  In those instances in which
the  papilla?  of the skin are well injected, the fat vesicles will also be  found
more or less  completely injected;  the injection  must be  made  from  the
main vessel, usually the vein, that supplies the part.] 
264
THE  SOLIDS.
                   ART.  IX. —EPITHELIUM.

   As the external surface of the body is invested with a cuticle which
has received the name of Epidermis, so are its internal free surfaces
in like manner clothed with a delicate pellicle which has been denom-
inated Epithelium. ■"
   Both the epidermis and epithelium are constituted of cells:  there is
this difference, however, between them, that while the former, by the
intimate union and super-imposition of its cells, exists as a distinct and
continuous membrane, the latter,  owing to the feeble  cohesion of  its
constituent cells, can scarcely, except in certain situations, be shown
to exist as a united and extended  structure.*
   The epidermis and epithelium are, therefore, hardly to be regarded
as distinct structures, but rather as the same, the differences observed
between them  being merely  modifications, the result of the different
circumstances  to wrhich they are  each subject.
   The essential identity of the two may be shown by an examination
of the epidermis at the outlets and inlets of the body, where, by gradual
transition, it may be traced inwards into the condition of epithelium;
and this, also, traced from within outwards, will be observed gradually
to acquire the  characters of  epidermis; so that, within a certain dis-
tance of  the  termination  of the  cavities of the body, which open
externally, the epithelium  may also be demonstrated as  a  distinct
membrane;  this membrane may be followed  in man from the lips  as
far backwards as the posterior part of  the mouth, also passing over
the tongue;  and in the horse and in birds it may be shown to  exist in
the stomach and gizzard.
   The epithelium will be first described, inasmuch as its organization
would appear to be more simple than that of the epidermis, which, by
modifications of its cells, is converted into so many apparently  distinct
structures.
   It has been remarked that the internal free surfaces of the body are
covered  by  epithelium:  these surfaces comprise those of both the

  * Leeuwenhoek first discovered in the mucus of the vagina little scales,  which he
presumed formed the internal membrane of that canal, and from which he conceived
they become detached by coitus.  (Opera, t. i. p. 153.155.)  He likewise noticed that
the mucus of the mouth contained scales, (Ibid. t. iii. p. 51,) and  he saw also the
cylindrical epithelial cells of the intestinal cavity.  (Ibid. p. 54. 61.) 
EPITHELIUM.
265
 open and the closed cavities, the former of which include the aliment-
 ary canal from mouth to anus, the genito-urinary organs and passages
 of both the male and female, and  the respiratory track, consisting of
 the  trachea, bronchi, cells of the lungs, and  nares;  the latter consist
 of the great serous sacs of the head, chest, and abdomen, and the lesser
 ones of the pericardium, tunica vaginalis, the cavities of the  joints,
 and of the lymphatic and blood vessels, including the heart.
   Thebursae are said by Henle* not to be furnished with an investing
 epithelium—a statement to be received with some degree of hesitation.
   It would appear, therefore, that, with the single doubtful exception
 alluded to, every free surface  of the  body is  invested with its own
 appropriate epithelium, the ventricles of the brain even  being lined
 with an epithelium proper to them, and the surface of the cornea being
 covered with one also.   The existence of an epithelium in this latter
 situation  may be directly proved by means of the microscope:  and it
 may be inferred from the  observation of the fact, that in the general
 casting of the epiderm  of snakes and  other reptiles, a delicate  film is
 likewise thrown off from the surface of the cornea.
   The epithelium has  not the  same  character in the different situ-
 ations in  which it is encountered, but the cells of which it is composed
 differ in form and size, according to age and the locality occupied by it.
   The several varieties of epithelium  may be reduced into two prin-
 cipal types, in the first of which the cells are more or less circular or
 polygonal, and in  the second are  elongated and  conoid.  These two
 forms  may be distinguished by the appellations of Tessellated or Pave-
 ment Epithelium, and  Cylindrical  or Conoidal Epithelium.   (See
 Plate XX. figs. 1  and 2.)
  The Conoidal  Epithelium  admits of sub-division  into  Naked
 Conoidal Epithelium and Ciliated Conoidal Epithelium.

                        TESSELATED EPITHELIUM.
  Form.—The cells of this description of  epithelium form  many
layers, are flattened, and either  circular, polygonal, or irregular in
outline: the younger cells  are  mostly of the  first shape,  and are
thicker than the  older  ones, which are irregular in  form, thin  and
membranaceous,  while the  polygonal cells  are encountered  more
particularly in certain situations,  as on  the  choroid  plexus, pericar-
dium,  and serous  membranes in general.   The polygonal shape is
* Anal. Gin. vol. vi. p. 225. 
266
THE  SOLIDS.
 produced by the mutual  compression exerted by the cells upon each
 other, and consequent adaptation.
   Size.—The  size of the cells of pavement epithelium varies both
 according to age  and locality;  the younger  and deeper seated cells
 are of course smaller than the older and more superficial ones; the
 larger cells are met with  in those situations where the epithelium is
 continuous with the epidermis, as in the mouth  and oesophagus, the
 vagina, urethra,' and  bladder,  the  commencement of the rectum, the
 inferior  division  of the nares, lining the eyelids, and  covering the
 cornea.   (See  Plate  XX. fig. 1.)  On the contrary, the epithelium
 of the pericardium, ventricles, aorta, and of most of the closed cavi-
 ties, is composed of cells  which are  very much smaller in  size than
 those of the localities previously enumerated.  (See Plate XXII.)
   Structure.—Epithelial cells illustrate faithfully the doctrine of cell
 development, each consisting  of a nucleus,  cell wall, and intervening
 space enclosing fluid, both the nucleus and the cell wall exhibiting a
 granular composition.
   It has been observed, that  the  younger  cells are thicker than the
 older and fully developed  ones, which become reduced to mere mem-
 branous  expansions, from  which it follows that the space intervening
 between the nucleus  and cell wall is greatest in the younger cells,
 while it  is almost obliterated in the older.  The smaller  cells are also
 more granular than the larger:  now, these two facts stand in close rela-
 tionship  with the function discharged by these cells,  and which is  so
 much the more active as the cavity is large and the granules numerous.
  The nucleus is likewise best seen in the younger cells:  in the older
 ones it becomes either entirely obliterated,  or it escapes  from the
 cavity of the cell, the position which it previously  occupied in it
 being indicated by a depression; it is for the most part circular; but
 occasionally, and particularly  in certain localities, it  is  found to be
 oval, as  in  the epithelium of  the  lower two-thirds of the uterus,  in
 that  of the pericardium,  and  also in that  of the blood-vessels, the
 aorta excepted; it sometimes occupies a central position in each cell •
 at others it is eccentric.
  The properties  of pavement epithelial  cells, as well as their form,
 size and  granular texture,  alter also with age: thus the younger cells
 are dissolved, with the exception of the nucleus, by acetic acid, while
the same reagent  applied  to  the older ones produces scarcely  any
 appreciable effect.
  Epithelial cells, on  the  addition of water, or after  death, become 
EPITHELIUM.
267
 white and opaque—a  common  effect of water on all animal struct-
 ures.  The change in the case of the epithelial cells probably depends
 upon the coagulation of their fluid contents; and to it the character-
 istic dulness of the eye after death is due.
   Distribution.—This form of epithelium is  more extensively dis-
 tributed than the conoidal variety: it is encountered on the free and
 serous surfaces of all the closed cavities, as of the cranium, thorax
 and pericardium, abdomen and  tunica vaginalis, lining the lymphatic
 and blood vessels; even the ventricles  of the brain itself, in which it
 rests immediately upon the cerebral substance, are not free from it:
 it is met with likewise  near the terminations of those cavities which
 open externally, as in the mouth, where it extends as far backwards
 as the cardiac extremity of the stomach, in the lower portions of the
 nares, whence it passes into the frontal sinuses, in the vagina and uterus,
 the lower two-thirds of which it lines, as also the urethra.   In the male
 subject it passes over the glans  penis, and then enters the urethra.
   The epithelium of the urinary apparatus should perhaps be referred
 to the pavement epithelium:  its cells, however, vary very consider-
 ably in form:  thus, many of them decidedly resemble the variety of
 epithelium under discussion ; others, however, are clavate, the narrow
 or fixed extremity being often produced into a long thread or filament;
 and again, others imperfectly represent the conoidal variety of epithe-
 lium; these last, as well as  the clavate cells, are met  with in the
 greatest quantity in the upper part of the bladder, and in the ureters.

                         CONOIDAL EPITHELIUM.
   Form and Size.—The  cells of this form  of epithelium are  much
 more regular in size and shape  than those of the tesselated or  pave-
 ment kind:  the term cylindrical usually applied to them is, however,
 far from accurate, since they do not  possess, even in a slight degree,
 the outward form of a cylinder: the word conoidal, here used, serves
 to express much more  closely  the real form of the cells of this variety
 of epithelium, although it fails to give an exact idea of their shape:
 thus, the cells in question are  not merely conical with flat summits,
but each cone is flattened at the sides,  so that  when the bases of the
cones are  seen directly, they exhibit  the  appearances of ordinary
polygonal tesselated epithelium; the side view of the  cells  will at
once make manifest their distinctness.   (See Plate XX. fig. 2.)
   Conoidal epithelial cells are usually disposed more or less vertically
 to the surface upon which they rest, their narrow extremities  being 
268
THE  SOLIDS.
turned downwards, and attached to that surface, and the broader and
free ends being directed upwards.
  Structure.—The cells of conoidal epithelium have  precisely the
same  structure as those of the previously  described  kind;  that is,
they consist of nucleus, cell wall,  granules, and  fluid  contents: the
chief difference is one of form and  not of structure.
  The nucleus is almost invariably  oval, the long axis  corresponding
with that of the cell itself:  it is often so large as to  occasion  the cell
to assume a ventricose form, it being contracted  immediately above
and below the part in  which the nucleus is situated.   Some observers
speak of  two nuclei  in a single  cell:   this, however, must  be an
exceedingly rare  occurrence, as I have  never  yet met  with a single
example of the kind.
  The  conoidal epithelium is, as  already remarked,  divisible  into
two kinds.

                  Naked  Conoidal Epithelium.
  Distribution.—This sub-division of epithelium, to which the des-
cription just given more  immediately applies, is  met with investing
the  mucous  membrane  of the alimentary canal, extending from the
cardiac  extremity of the stomach to »within two or three inches of the
rectum; it is encountered likewise lining the several ducts and prolon-
gations  which communicate with  this:  thus, this form  of epithelium
exists in the  gall-bladder, where it  is of a deep yellow colour, in the
ductus  communis choledocus, in  the  pancreatic duct,  and in the
mucous crypts or follicles imbedded in  the mucous membrane.  It is
found also in the upper portion of the nares,  in the salivary ducts, in
the  appendix vermiformis, and in modified form in the vas deferens.
  In the stomach, the naked conoidal epithelium does not exist in an
unmixed form; it  occurs intermixed with pavement epithelial cells,
probably derived from the oesophagus, and  carried  down during
deglutition.
  It is  in  the  gall-bladder, the small  intestines  and  the appendix
vermiformis, that  the naked conoidal epithelium exists in the greatest
perfection,

                  Ciliated Conoidal Epithelium.
  The cells of this variety of conoidal  epithelium agree  precisely in
form,  size,  and arrangement with those of  the first described sub- 
EPITHELIUM.
269
division, the only difference  being, that they  are possessed of the
singular addition of vibratile cilia.*   (See Plate XXI. fig. 3.)
  The cilia taper from base to apex, and are attached  to the thick-
ened  margins of the  summits of  the  cells, ten or  twelve of  them
belonging to each.  In the frog they would appear to be not merely
attached to  a circular line, but  also to  the segment of  the cell
described within this.   (See Plate  XXI. fig. 1.)
  During life, the cilia are in a constant state of activity:  the power
by  which  their  motions are effected  is, however,  involved in the
greatest obscurity: it can scarcely  be the result of muscular structure,
as some have supposed, since the entire cilium is many times smaller
than  the  smallest muscular fibre.   The idea has been put forth that
the cilia  are hollow;  that  they communicate with a vessel which
runs  along their bases, containing  fluid;  and that they are moved by
the successive injection and expulsion  of this fluid.
   One fact has been observed, which  affords countenance to the
above  explanation of  the motion of  the cilia, viz:  that  this  takes
place in  a determined direction:  commencing in the  cilia on one
side,  it runs along them to the opposite, the several cilia being thus
successively called into action.  It is this peculiar character of the
motion of the cilia which has led  to its comparison with the waving
of a corn-field over which the wind passes in successive gusts.   The
motion, in whatever way effected,  is singularly beautiful, and, strange
to say, exhibits  many of the characters of volition: thus, it will some-
times cease altogether for a time, and then suddenly commence again.
It is also sufficiently powerful to effect the entire displacement of the
cell or  corpuscle to which the cilia are attached, and many of which
may  frequently be seen moving freely and quickly about, usually in
circles, in the  field of the  microscope.   This curious spectacle  is
most readily witnessed in the ciliary cells of the trachea of  the frog,
which  are  of a different form from  those of the mammalia,  being
rounded in place of elongated and  conoidal.  (See Plate XXI. fig. 1.)
   The  combined motion of the cilia is also  capable of putting  in
movement either fluids or solid particles which may come into contact
with  them.  This fact those who are given  to  microscopic investi-

  * To Purkinje and Valentin especially belong the honour of making known in all
its extent the phenomenon of ciliary motion, and which before that time had been
observed only in some few of the lower animals, and concerning the nature of which
many  errors prevailed. They discovered it in the respiratory and female  genital
organs in 1834. (Miiller, Archiv. 1834, p. 391.) 
270                      THE SOLIDS.
gation will have had many opportunities of verifying, and one may
easily at any time acquire the proof of it by mixing with the fluid in
which the cilia are acting some fine powder, as, for example, of carbon.
  The motion of the cilia, when acting in combination, is stated to
take place always in a determined direction from  within  outwards.
It would appear,  however,  from  the observations  of Purkinje and
Valentin*  that  the  direction is  capable of reversion:  thus,  these
observers saw the accessory branchiae of the anodon vibrate during
from  six to seven minutes  in one direction, and afterwards, during
the same lapse of time, in an opposite.
  The influence of physical  and chemical reagents upon the vibratile
movement has  been carefully examined.   Thus,  if a portion of
vibratile epithelium be touched or scraped, the motions of the cilia will
become more active, and sometimes commence  again even  after they
had become extinct.   They cease at a temperature below the freezing
point, and at a degree of heat sufficient to  occasion the coagulation
of the animal  fluids.  Galvanism  destroys their action, but in a local
manner—a fact which a reference to  the constitution of epithelium
by the union of separate cells may serve to explain.  Among chemical
reagents, narcotics are without  influence; acetic  and the  mineral
acids  destroy the motion, as  also caustic ammonia, nitrates  of potash
and of silver.  The serum of the  blood prolongs its duration.  Urine
and white of egg are without effect upon it.  Bile instantly destroys
the activity of the cilia.
  The ciliary motion soon ceases after death in  the mammalia, but
continues in many of the invertebrata,  and especially in several of
the mollusca, as, for example, in the river muscle  and the oyster, for
days after the  death of the animal.
  It would appear, therefore, that  each  ciliated corpuscle bears the
closest possible  resemblance to many of the infusory animalcules,
and it is questionable whether its claim to be regarded as  a distinct
entity be not equally strong.
  Distribution.—Ciliated epithelium has not been as yet discovered
among the mammalia in any closed cavity,  but  always in situations
which communicate with the air;  thus, it is met with, as is  generally
known,  lining the  trachea  and  bronchi,  extending even   to  their
minutest ramifications; again, it  is  encountered in the  Fallopian
tubes, and lining the upper third of the cavity of the uterus of  adult
animals,  but not that  of young  mammalia.  There is yet another
                       * Motus Vibrat., p. 67. 
EPITHELIUM.
271
locality in which I believe it also to exist, viz: in the convolutions of
the tubuli seminiferi of the epididymis.
   On the other hand, there are many situations in which it has been
repeatedly asserted to exist, but in which patient and repeated inves-
tigation  has failed  to reveal  its presence;  as, for example,  in the
ventricles of the brain,* covering the pia mater, and lining the eyelids
and frontal sinuses.f
   The epithelium of these several parts, on the contrary, is pavement
and not ciliated epithelium.  (See  Plate  XXIV.)
   Purkinje.J in describing the epithelium of the ventricles, does so
most  circumstantially, and states that he followed the vibratile move-
ment in  the  sheep  from the  lateral ventricles  through  the third
ventricle, and  by the aqueduct of Sylvius into the fourth.
   Valentin§ confirms the accuracy of this description as regards man.
   We find Henle|| describing the epithelium of the ventricles as a
cuneiform ciliated epithelium;  and in  Gerber's General Anatomy,
we remark that it is stated to be a tesselated ciliated epithelium. It is
singular how so great an error could have originated, and still more
so how it could have been so long perpetuated.

              DEVELOPMENT AND MULTIPLICATION OF  EPITHELIUM.
   Each  epithelial  cell is first detected as  a nucleus without any
appearance of cell wall  around it:  this, however, may exist, closely
embracing the nucleus, even from  the  earliest  period at which this
can be  observed.    After a  time, however, a  transparent  border
becomes visible, surrounding the nucleus: the width of this goes on
gradually increasing, until at  length  the full  dimensions of the cell
have  been attained:  now, the outer limit of this  border doubtless
indicates  the cell  wall, the clear space between it  and the nucleus
being in the younger epithelial cells filled with fluid.  In the  conical
epithelium the  cell wall is not developed  equally around the nucleus
as in  the pavement epithelium, but chiefly in two opposite  directions.
   It has been  observed,  that young epithelial cells are thicker and
rounder than the older ones; it has also been remarked, that they are
more  granular; facts which stand in close relation  with their func-
tional activity.
   It has been  noticed likewise, that  the nucleus in the progress of
      * Purkinje in Miiller, Archiv. 1836, p. 289.
      f Henle, Anal. Gen. t. vi. p. 252.          J Miiller, Archiv. 1836.
      5 Reperlorium, 1831, p. 158. 278.         || Anal. Gen. t.vi. p. 253. 
272
THE  SOLIDS.
development becomes either obliterated, or that it escapes from  the
cell.  Now, it has struck me that this disappearance  of the granular
nucleus  and granules of the cell  wall might possibly  be connected
with  the reproduction or multiplication of epithelial cells, as well as
of cells  occurring elsewhere than  in the  epithelium, and that each
granule might in reality  be an epithelial cell in  embryo.  This is of
course but a conjecture: it is one, however, which would appear not
to be contradicted by any other known fact, and to have analogy in
its favour;  the  mode  of reproduction  among the lower algae being
precisely similar.
  The occurrence of two nuclei in the same cell has been recorded
by some observers, and who have from this fact drawn  the inference,
that epithelial  cells  are multiplied  by division.  This method of
increase cannot, however, be presumed to prevail to any extent, since
it is a circumstance  of extreme rarity to meet with two nuclei in the
same  cell.

                      NUTRITION OF EPITHELIUM.
  The epithelium has no immediate or structural connexion with the
parts  which lie immediately beneath it, neither does it receive blood-
vessels and nerves from those parts; it is simply  dependent upon them
for the supply of nourishment, of which it is the  recipient, and which
is derived from the blood-vessels distributed throughout the tissue of
the true skin lying beneath it, and from which vessels the plasma is
continually escaping by transudation or exosmosis.

                DESTRUCTION AND  RENEWAL OF  EPITHELIUM.
  The epithelium in  every part of the body is continually undergoing
a process of destruction,  and consequent renewal.
  It  is less  easy to  establish the fact of the  destruction of the epi-
thelium  in the closed  cavities than in the open; nevertheless, that it
really does take place even in these, may be inferred from the observa-
tion of the fact  that the cells of epithelium encountered in such local-
ities represent every  degree of development, many of the older ones
also being destitute of nuclei, and more or less broken into fragments.
It is probable, however, that the process of destruction  is slower in
the closed than  in the open cavities.
  In the open cavities, the destruction of epithelium is doubtless more
considerable  and more rapid; it is also more easy to  determine in
these; thus,  during mastication, deglutition, and digestion, a consider- 
EPITHELIUM.
273
 able amount of epithelium becomes disturbed, removed from the sur-
 face to which it was attached, and mixed up with the saliva, mucus,
 gastric fluid, food, &c, and finally is discharged from the system with
 the faeces, in which, by microscopic examination, it may readily be
 detected.
   The fact of the gradual and continual destruction  of epithelium
 may likewise  be ascertained by an examination of  the several fluids
 discharged from the system,  as  the  saliva,  the  mucus, from either
 mouth, nose, lungs, urine, seminal or menstrual fluids, in all of which
 the microscope will  reveal an abundance of epithelial cells.
   The same fact may also be determined by a microscopic examina-
 tion of the scum which collects during the  night on the  lips and
 around the base of the teeth of many persons.
   In certain situations the epithelium undergoes not merely a gradual,
 but also  a periodical  destruction,  as  in the uterus  at  the  monthly
 periods and after parturition.
   The continual destruction of epithelium having been  thus rendered
 manifest, its renewal follows as a matter of necessity.
   In irritation of the mucous membrane of the bronchi, nose, and
 alimentary canal, it  is possible that the  epithelium, during the period
 of the continuance of the irritation, is entirely  destroyed.

                         USES  OF EPITHELIUM.
   The first use of the epithelium  is a passive one, it serving like the
 epidermis as a protection to the more delicate parts which lie imme-
 diately beneath it.
   The second use is active, the epithelium doubtless being an import-
 ant agent in secretion.
   Each epithelial cell may be regarded as a gland reduced to its most
 simple  type or  condition, it  embodying all  that is essential in the
 largest  and most complex secreting  organ,  viz:  the true secreting
 structure.
   The  nature of the  fluid secreted by epithelial cells  is not every
 where  identical,  but varies according to their exact structure and the
locality in which they are found: thus, in some situations, they secrete
serum, as  in the serous sacs:  in others mucus, as in the mouth, nose,
alimentary canal,  &c; in others synovia,  as  in the joints; in the
stomach and in the duodenum, they assist in the elaboration of the
fluids which are there found.
   That the epithelial  cells are the real agents engaged in the pro-
                              18 
274
THE  SOLIDS.
duction of the several fluids named, is rendered certain by the facts
that they correspond precisely with the undoubted secreting structure
of true glands; and  further,  that  in the situations where they are
found,  no other organization exists to which the function of secretion
could with any degree of probability be assigned.
  The  importance of the office discharged by the epithelium explains,
then, the universality of its distribution.
  The  diffusion of epithelial  or secreting cells over the surface of
membranes which require to be kept continually moistened by a suit-
able fluid, affords a beautiful example of the wise adaptation of means
to an end: by no other  means than  that employed could the  end in
view be so surely accomplished, or with so great an economy of space.
  The above-described uses of epithelium are common to it wherever
encountered: the third use is mechanical, and accomplished only by
the  ciliated form of epithelium.
  It has  already been observed that the force of the combined action
of the cilia is so great as to enable them to carry along with or drive
before  them fluids, and even solid particles which may happen to come
in contact with them: it has likewise been remarked that the direction
of their united action is  invariably from within, outwards or towards
the  outlets of the body; at least it is so among the mammalia.   From
a knowledge of these facts it  is not difficult to suggest the probable
use  of vibratile epithelium in  the localities  in which it has  hitherto
been discovered in man and the mammalia.
  Thus  in  the bronchi  and  trachea,  it may be presumed  to be
designed to facilitate the escape from  those passages of any foreign
particles which may have  found entrance to them.
  Again, in the Fallopian tubes and upper portion of the uterus, it can
scarcely  be questioned, but that its use is to hasten the progress of
the  ovum from the ovary to the uterus; and, presuming that the
direction of the action of the cilia may be, and is sometimes reversed,
the  vibratile  epithelium of these parts may be further intended to
ensure  the more speedy transmission of the seminal fluid along the
Fallopian tubes to the ovary, upon which it has been detected by more
than one observer. 
EPITHELIUM.
275
                            EPITHELIUM.
  [Microscopic  examination  has  revealed the  fact that many tumours
supposed to be cancerous, especially certain tumours about the lips, were
composed of degenerated epithelium.  Ecker* has described these tumours
of the lip, and denominated them  bastard  cancer of  the  lip.   It is now
ascertained that these tumours are not confined to the skin, but occur  in the
mucous membranes.  Rokitansky has found them on the lining membrane
of the larynx, trachea, stomach, intestines, and  bladder.  They may be also
met with on the dorsal aspect of the hand, on the cheeks, scrotum, prepuce,
and  it may  be  the chimney-sweep's cancer is but  an epithelial  tumour.
Lebert regards them as benign, since they contain no cancer-cell.   Roki-
tansky and Bruck consider them malignant.  Dr. Gorup  Bezanes regards
the important question to be, not whether these tumours may be benign, but
whether  they are  altogether exempt from malignity:  his observations con-
firm the opinion of their malignity.
   See Archiv. Gen. de Med. torn xxm.  p. 76,  Mai, 1850.
   See also Dublin Quart. Jour. August, 1850, p. 255.

                           PREPARATION.
   The text has already indicated  the  different localities from  which the
various forms of epithelium may be obtained.
   The pavement or scaly epithelium may be best studied  by scraping any
of the serous membranes gently with a knife, and examining the particles
removed.   Many of the cells after removal will be  found to adhere together.
The  addition  of a  little weak ascetic acid will  render the  angles of the
scales more apparent.
   The conoidal variety of epithelium is easily obtained by macerating any
of the mucous membranes, as, for instance, a portion of the alimentary canal.
By this process, the epithelium becomes  detached, and may be collected and
viewed with the microscope.   The  ciliated  variety possesses most interest.
The cilia  may be seen in motion  by taking a  small piece of the mantle of
an oyster  or  mussel, folding it upon itself,  and placing it  under the micro-
scope so  as to allow the cilia to project.  The edge of the  beard will also
show the cilia in motion.  The fragment should be moistened with water,
and covered with thin glass;  a power of about 250 diameters is necessary
for good observation.   The  currents caused  in the water by the cilia in
motion may be readily detected by the suspension of fine particles of car-
mine or charcoal  in the water. These  particles are first seen attracted by
the ciliary motion, and then repelled.
* Archiv. fur Physiol. Heilkunde, 1849. 
276
THE SOLIDS.
  In quadrupeds the  ciliary motion may be observed  by taking a small
portion of ciliated mucous membrane from an animal recently killed, and
folding it in the manner already indicated.
  In man the cilia may be seen in motion in recently detached nasal polypi.
They may also sometimes be discovered in mucous discharges.
  The ciliary motion may be studied on a larger scale in many of the fresh-
water infusoria, so abundant during the summer and fall months in small
ponds and stagnant pools.
  Epithelial cells may be preserved in the flat or thin glass cell, suspended
in a weak solution of chromic acid, or Goadby's B-solution.] 
EPID ERMIS.
277
                    ART.  X.—EPIDERMIS.

  The entire of the external  surface of the body is invested with a
membrane which has been denominated epidermis, formed of super-
imposed layers of nucleated cells  (see Plate XXIV. fig. 3), and the
number of which layers is greatest in those situations in which the
membrane  is  subject to the most  pressure, as  in  the palms of the
hands and soles of the feet, in which the epidermis sometimes attains
the thickness of the T\, or even the } of an inch.*
  The form, structure, and development of the  cells  composing the
epidermis are in every respect identical with  those of the tesselated
variety of epithelium already described; thus, first, the younger and
deeper-seated cells are spherical in outline, and almost globular, while
the older and more superficial cells become irregular in form, expanded,
thin, and membranaceous;  secondly, like those of the  tesselated epi-
thelium, the cells consist of a nucleus, cell-wall, cavity, and granules;
it  is,  however, worthy of remark,  that the nucleus,  as  well as the
majority of the granules contained in the epidermic cells, disappear
at an  earlier period of development than do  those of the epithelium—
facts which will be explained when  the uses  of the epidermis come to
be treated of; thirdly, the plan of development is the same in  the two
cases, the cell-wall being developed around  the nucleus, which  is the
part first formed.
  Thus far, then, there is  a close correspondence between the epider-
mis and epithelium;  so close, indeed,  as to  make it apparent  that the
two are but modifications of one and the same structure.  The chief
respects in which it differs from the  epithelium are in the compact
and firm union of the cells with each other, whereby it forms a distinct
and continuous membrane,  and in the paucity of granules dispersed
throughout the cells.
  The epidermis also  stands in precisely the  same relation with the
parts  beneath it as  the epithelium; thus, it has no structural con-
nexion with those parts, and receives neither blood-vessels nor nerves
from them, but is simply dependent upon them for  the plasma which
is continually escaping from the blood-vessels  of the true skin.  This
  * Leeuwenhoek first observed that the epidermis was composed of scales placed
one against the other, and also that, after a certain lapse of time, they were cast off,
and their place supplied by others. 
278
THE  SOLIDS.
 want of structural  connexion is  shown by the fact that a portion of
 the  cuticle may be detached without its  removal occasioning either
 pain or haemorrhage.
   This separation of the epidermis from the  dermis  frequently takes
 place during life, as from a burn, scald, or blister, or from the effusion
 of serum, the result, not of injury, but of disease.  After death, and
 on   the  commencement of  decomposition,  the  epidermis  may  be
 detached in large masses, the prolongations sent down to the sebace-
 ous  and sudoriferous glands also coming away with it.
  The  epidermis does  not  merely cover the whole  external surface
 of the body, but sends processes into its various outlets, as the mouth,
 nose, rectum, vagina, and male urethra; these prolongations soon lose,
 however, the characters of epidermis, and  acquire those of epithelium.
  The  epidermis likewise  sends  down processes into the sebaceous
 and  sweat  glands, and which, forming a perfect tube, serve to convey
 the secretions of those glands to the surface,  on which they open  as
 raised  and rounded  papillae, with central  depressions and apertures.
 (See Plate  XXIII. figs.  1 and 2.)
  A sheath of epidermis likewise encircles the base of each hair.
  The number of these  infundibuliform processes and salient papillae
 which  open on the surface is immense, and  may  be  stated at about
 3,000 to the square inch,  which,  computing the number of square
 inches of surface  in a  man of average  size at 2,500,  would give
 7,500,000 for the entire  surface of the body.
  In addition to the papillae, we observe on the surface of the epider-
 mis a great number of lines or furrows which map it  out  into a net-
 work of small polygonal and lozenge-shaped spaces; these are of two
 kinds, the one large and coarse, and corresponding with  the flexures
of the joints; the others smaller, occupying the interspaces between
 the larger, and also  being generally distributed over the surface of the
 epidermis, where the articular furrows have no existence.  The plan
of arrangement of the smaller lines is as follows: A number of straicmt
lines, usually from six to ten, radiate, like the rays of a wheel from its
centre, from each hair-pore;  these  usually come in contact with the
lines proceeding from other hairs.  These radiating lines thus mark
out the surface  into triangular spaces, between  which  are  usually
situated two or three other pores, those of the  sebaceous and sweat
glands;  from each of these also similar radiating lines proceed; these
unite with the coarser lines  given off from the hair follicle, and occa-
sion  a still  further  sub-division of the surface of  the  epidermis into
triangular spaces. The result of this minute sub-division is to occasion 
EPIDERMIS.
279
the whole surface of the epidermis to assume a minutely and beauti-
fully reticular appearance.  The coarser lines are best seen in the
palms of the hands and soles of the feet, while the smaller and finer
lines may be readily traced, following the disposition just described on
the back of the hand.
   The effect of water in rendering the cells of tesselated epithelium
white and opaque has been referred to:  its long-continued application
to even  the living epidermis  produces a similar result, which  most
persons must have observed, although some would be  at a loss to
account for it; thus, the skin  of the fingers  of those who have been
engaged in  washing for some hours becomes of a pearly whiteness.
   It sometimes happens that epidermic cells are developed in increased
and abnormal quantities, giving rise to tumours, and which are by no
means of uncommon occurrence.
               EPIDERMIS OF THE WHITE AND COLOURED RACES.
   Between the epidermis of the white and the coloured races there is
a perfect identity of structure; the only difference is, that the young
epidermic  cells  of whites contain little or no colouring matter, or
pigment granules, except in certain situations, while those of blacks
are filled with them; this difference can scarcely be  regarded as per-
manent or structural;  it is one rather of degree than kind, and over
which, moreover, climate exerts an all-powerful influence.
   We have continual opportunities of witnessing the effect of climate
in increasing the amount of pigmentary matter in the skin.  All have
noticed that after a few years' residence in a hot country, the skin of
many individuals becomes several shades  darker than it was pre-
viously, and that  even  the inhabitants of the same country are darker
during the summer than in winter.
   It would appear, therefore, to be very possible  that climate  alone,
operating through many ages, would be sufficient to change the colour
of the skin from white to all the varying shades of red, olive, and  black,
met with among the different families of the human race.
                 DESTRUCTION AND RENEWAL OF EPIDERMIS.
  The  epidermis,  like  the   epithelium,  is constantly undergoing
destruction  and renewal; the evidences of this  are, however, more
obvious and striking in the case of the epidermis, than were  those
adduced in proof of the destruction of the epithelium.
  Thus the destruction of the epidermis is proved by a variety of facts:
  By the gradual disappearance from the skin of indelible stains, such
as those produced by nitrate of silver or nitric acid. 
280
THE  SOLIDS.
  By scraping the soles of the feet  after immersion  in warm water;
the white and powdery material which is  obtained, often in  large
quantities, examined with the microscope, will be found to consist of
epidermic scales.
  By the use of the warm bath; floating on the surface of the water
will  be observed, more  or  less of  a thin  and  whitish  scum; this
consists of desquamated epidermis.
  By rubbing the moist skin with  a rough  towel; a considerable
amount of epidermis, visible to  the naked eye, will be removed.
  The  skin  of new-born  children  is frequently  observed  to be
covered with a white  and  soap-like crust;  this,  examined  with the
microscope, will be found to consist of epidermic scales mixed up
with sebaceous matter.
   The last proof to be adduced of the desquamation of the epidermis
is one derived from disease; after  inflammation of the skin, whether
that of erysipelas,  scarlatina or measles, the epidermis  peels  off,  a
new one being previously formed beneath the old.
  Among  many of the  amphibia  and reptiles, the casting of the
epidermis is a periodical occurrence; in man, on the  contrary, it is
a constant and  gradual process  normally, although it is also occasion-
ally periodic  from disease.

                       USES OF THE EPIDERMIS.
  The principal uses of the  epidermis are threefold.
  The first and  chief use  is  to serve as a protection to the  more
delicate parts which lie immediately beneath it.
  The second is to prevent the  too rapid dissipation of the caloric of
the system.
  The third use has reference  to secretion.  It is evident, however,
that the importance of the epidermis as a secreting organ  is not  con-
siderable,  seeing that the external surfaces of the body do  not require
to be kept moist, to the same extent as the internal.   That the epider-
mis does not very actively administer to secretion might  be inferred
from the  transparency of the fully-developed  cells, the faintness of
the nuclei, and  the paucity of the granules contained within them.
   Epidermic cells are also  capable of absorption, a fact which their
change of  colour after long  immersion in water testifies.
   By far the best description of the anatomy of the  epidermis which
has fallen under my notice is that contained in the admirable chapter
on the Anatomy and Physiology of the Skin attached to the second
edition of Mr. Wilson's work on the Diseases of the Skin. 
EPIDERMIS.
281
                              EPIDERMIS.
   [In the paper by Mr. Rainey, referred to in the Appendix, he divides the
 epidermis into two layers, the superficial layer or cuticle, and the deep layer
 or rete-mucosum of other authors.   The deep  layer rests on the basement
 membrane covering the papillae, and fills up the grooves between them: this
 layer is  composed of  nucleated  cells, in different stages  of development:
 those  below being very small, probably only cell  nuclei, those in the  centre
 are  most perfect, and those above approaching the  condition of epidermic
 scales.
   The superficial layer, or cuticle, extends from a little beyond the  apices
 of the  papillse  to the  surface, and  consists of flattened cells, which have
 become converted into scales.  These scales are not affected by action of
 acetic  acid,  or  strong  solution of  potassa, while  by  these reagents, the
 nucleated cells are entirely destroyed.
   In the Appendix, already alluded to, the author has referred to the state-
 ment made by Mr. Rainey, that no true duct from the sudoriparous glands
 exists  in either  layer  of  the  epidermis, the passage being a spiral  one
 through the epidermic  cells and scales.   ( Vide Plate LXXVIII., figs. 1, 2.)
 The lining of  the sudoriparous duct, separated  with the  epidermis after
 maceration, is the epithelial lining  of the duct, and not  the entire  duct, as
 stated by some writers.
   The epidermis may be readily examined in thin vertical sections made
 with the  Valentin's knife, or  sharp  scalpel.   The fresh  skin will be found
 best for this purpose,  and those  portions from the  heel or palm of the hand
 show the structure  best: these maybe farther dissected with the  needles
 under the microscope and  in water, and other sections may be treated with
 acids and alkalies.   In some  instances, thin sections can  be better made
 when  the skin  has been  hardened,  and rendered  more firm  than  in  its
 natural state.
   For this purpose, a strong solution of carbonate of potassa, diluted nitric
 acid, or sulphuric ether, may be used.   When sufficiently thin sections can
 be obtained without  this process, the  structure  is more  readily made out,
 and  with  a good Valentin's knife, this is not usually difficult to do.  By
 continued maceration, the epidermis may be separated in  layers; this pro-
 cess  is necessary to exhibit well the  deep layer or rete-mucosum.
   When desired,  sections of epidermis may be mounted in fluid for preser-
vation : but in this condition they will be of little service, unless to show the
spiral  passages and external orifices of the sudoriparous ducts.  The rete-
mucosum is also best preserved in fluid.] 
282
THE  SOLIDS.
                     ART.  XI. THE  NAILS.

  The horny appendages of the feet and  hands,  the  nails, do not
constitute a distinct  structure or type of organization in themselves,
but are merely modifications of one which has already been described,
viz: the  epidermis.
  Nails,  therefore, consist  of cells similar to those  of  which the
epidermis is itself constituted, with the difference that they are harder,
drier, more  firmly adherent  to each other,  and that in the majority
the nucleus is obliterated.  (See Plate XXV.)
  To display the  cellular constitution of nails, some little nicety  is
required; it  may  be shown, however, in the  thin scrapings of any
fragment of  nail submitted to  the microscope, as also by soaking the
nail in a weak alkaline solution, and which, acting upon and dissolv-
ing the inter-cellular and uniting substance, sets free the cells.
   The cellular  structure of nails may also be shown, even without
previous preparation, by a careful examination of the root and under
surface of the nail, in which situations young and nucleated cells may
usually be detected.
   The younger nail cells, like those  of the  epidermis in the coloured
races, contain pigmentary matter.
   Nails/however, are  not simply constituted of super-imposed and
adherent cells,  but  these are regularly  disposed in layers or strata,
each of  which probably indicates a  period of growth.
   These layers, marked by  striae, may  be  clearly seen on  any thin
section of nail, whether longitudinal  or transverse;  they do not appear
to  follow  any very definite course; usually in a longitudinal slice,
 they run from above, downwards and forwards; sometimes they are
 horizontal, but I have seen instances in which  the striae were directed
 obliquely backwards, in place of forwards.   In the transverse section,
 the strias are less  strongly marked, and run usually more horizontally.
 (See Plate  XXV.)   Occasionally they are seen  to pass  in opposite
 directions, and  to decussate.   I am  disposed to think that  the  one  set
 of strias visible  are rather apparent than real, and are produced by the
 knife employed in making the section.
    It is usually  easy to distinguish the superior from the inferior edge
 of a slice  of nail;  the former will generally appear  quite  smooth,
 while the latter will be rough and uneven.   (See Plate XXV.) 
THE  NAILS.
283
   Such is a brief sketch of the structure of nails:* their form, posi-
 tion, and mode of connexion, may next be considered.
   Each nail may be said to be  quadrilateral and convex from side to
 side, as  it is  also very generally from  before  backwards; the  three
 posterior margins are received  into a groove formed by a duplicature
 of the dermis and epidermis, the  anterior margin alone being free.
 The root and sides of the nail, the former consisting  of about one-
 fifth  of its extent,  are intimately attached to  both  surfaces  of  the
 groove; the inferior aspect of  the body of the nail is likewise firmly
 adherent to the derm beneath it, except for a  small distance at its
 anterior part.
   The nail,  then,  is  attached  to  the  dermis by its root, and by a
 portion of its inferior  surface; this  attachment, however, is scarcely
 to be considered as structural,  since it consists  of a mere adaptation
 of the opposing surfaces of the dermis and nail.   The surface of  the
 dermis upon which the nail rests, it is  known, is not smooth, but is
 raised into papillae; to these the nail adapts itself, and in this way the
 two become intimately united.
   It is  in this  manner, also, that the longitudinal  lines observed on
 most nails are produced, and the  appearance of which has induced
 some observers to entertain the idea that  they are of a fibrous, and
 not a cellular constitution.
   Nails are, to a considerable  extent, hygroscopic, becoming by  the
 imbibition of fluid soft  and yielding.

                         DEVELOPMENT OF NAILS.
   Nails are developed somewhat differently from the epidermis, of
 which we have stated that they are a modification; thus,  they do  not
 increase by the equal development of new cells on the entire of their
 under surfaces, but they grow  from a point, from the base or root of
 the nail.
   The reality of this mode of development becomes evident  from  the
following considerations:
   1st. That  the younger nail  cells are found principally at the root
of the nail.
   2d. That  if  the  relative situations  of  two  spots  or stains  be
                                            •
  *The first exact description of the  nail and of the disposition of the derm which
supports  it was  given by Albinus (Adnotat. Acad. lib. ii.  1755, p. 56), but Schwann
showed that the  nail had a lamellated  structure, and that the lamellae are composed
of epidermic scales. (Mikroskopische Untersuchungen, 1839, p. 90.) 
284
THE  SOLIDS.
 observed; it wjll be  seen that  during the  growth of  the nail, they
 preserve precisely  the  same relation with each other, only that they
 gradually approach the end or free  margin of the nail, which  at
 length they reach, and from which finally they are worn away.  This
 observation proves the  absence  of interstitial  growth, and shows that
 the nail increases in length by additions made to the root.
   Although it is  certain that the longitudinal growth  of nail occurs
 by the development of cells at  the root, yet it is also evident that its
 thickness is increased  by the  formation of new cells on its under
 surface, where they may usually be  detected with the microscope  in
 a partially developed state.  This double development explains why
 the nail is thinnest  at the root, where only a single method of growth
 prevails.
   The junction  of the root with the body of the nail is indicated by
 a semi-circular line, and the former is not  merely thinner than the
 latter, but it is also softer and whiter;  whiter in consequence of the
 subjacent dermis containing in that situation fewer blood-vessels, and
 its papillae being  smaller.
   From the preceding account of the development of nails, it follows
 that when these sustain any loss of substance on their upper surfaces,
 this  loss is  never repaired, but remains without  alteration  until  it
 reaches the  free margin of the nail.
   Epithelium, epidermis, nails, and some other structures of the body,
 never seem to attain to a stationary state;  they are throughout  the
 whole of life undergoing a process  of  development; this, in the case
 of the nails  of man, renders the interference of art  necessary  to
 remove from time to time the redundant growth.
   It is probable,  however, that if the nails were not cut, but  allowed
 to grow at will, they would not  exceed a certain length;  among  the
 Chinese,  who do not pare their nails, they are usually  about two
 inches long.
   Nails doubtless sustain a loss of substance beyond that which they
experience  from  occasional  cutting, as from friction and  the des-
quamation of the cells from the inferior and anterior portion  of each
nail,  and  which may be inferred  to take place from the fact that  the
matter which accumulates beneath the  extremities of the nails is to a
great extent made up of epidermic or nail cells.
   It  has been estimated that the  entire  body of a nail, from the root
to its free margin, is developed in from two to three months.
   The third month  of intra-uterine life is the earliest period at which 
THE  NAILS.
285
the nails can be detected; they  then consist  of nucleated cells, and
rather resemble soft epidermis than the hard and horny texture of
fully-developed nails.
  A nail  which has been once  entirely destroyed is always  regen-
erated  in  a very  imperfect  manner,  it  being usually seamy and
irregular  in consequence of the disturbance and injury sustained by
the adjacent dermis, and the markings of which are  impressed upon
the nail.
  Nails are subject  to deformity in  certain chronic  maladies  of the
heart and lungs, especially  in cyanosis and  phthisis.   It has been
suggested  that this  may depend upon  the state of the circulation in
the vessels of the dermis.
   The  various modifications of nail met with throughout the  animal
kingdom, the  claws of birds and carnivora, the hoofs  and horns  of
ruminants, have  essentially  a  similar structure to  the  nails of man.
The  hoof of  the horse and of some other animals is traversed from
above downwards by the spiral ducts of the sebaceous glands.
                              NAILS.
  [The structure of nails is examined in thin sections and scrapings, placed
in the  field of the microscope, and covered with a drop of water, or oil of
turpentine.
  The secreting vessels of the nail, so well described by Mr. Rainey in his
paper quoted  in the Appendix, can only be seen  after injection, and the
removal of the nail.   A fcetal subject is well adapted for this injection.  A
hand or foot of an adult may  sometimes be so well filled as to exhibit these
vessels.
  The sections or scrapings of the nail, may be  preserved  dry, in fluid, or
in balsam, the choice depending on the thickness of the specimen.  The
injected matrix, dec, is best preserved  in fluid; for this  purpose, alcohol
and water, or  Goadby's B-solution, may be employed,

  See  Appendix, page 541.

  Plate LXXI. represents the different vessels as described by Mr. Rainey.] 
286
THE  SOLIDS.
                ART.  XII. —PIGMENT  CELLS,
   Colouring matter  is  found in  the  animal  organization  in two
states, either diffused throughout the fluid contents of colourless cells,
as in fat cells generally, but especially in those of the iris of birds,
and  as in the liver cells, and  red blood discs, or it is limited to the
granules contained in  certain peculiar cells, the  parietes of which are
also colourless, which have received the name  of pigment cells, and
which we are now about to describe.
   Pigment  cells  have  precisely  the  same  structure  as those  of
epithelium and epidermis,  the description  of which  has  just been
brought to  a conclusion; that is, they  consist of cell  wall, nucleus,
cavity, and  granules;  the only difference between the two is, that the
granules  in the one case are coloured", and in  the other colourless:
as may be  inferred from their similarity  of organization, a similar
mode of development  prevails  in both.*
   All  the varieties of colour of the eye and of the  skin, observed
among the different members and families of the human race, depend
upon the number of pigment cells and the shade and intensity of  the
colouring matter enclosed within the pigmentary granules; the deeper
the colour, the more abundant the pigment cells, and the greater  the
depth  of colouring  contained  in the granules;  thus, of course,  the
pigment cells scattered  beneath the epidermis of the  Ethiopian  are
far more numerous than those found beneath that  of the white race,
and  the colouring  matter of the granules is doubtless also darker.
   In the white, however, a greater or less number of pigment cells is
almost  invariably  found  in certain situations, as in the  eye, on  the
internal surface of the choroid, and the posterior  aspect of  the  iris
and  ciliary processes, also between the sclerotic  and choroid; in  the
skin at  certain localities where it is  placed  beneath the  dermis and
epidermis, as  in the areola round the nipples, especially of women,
and  about the perinseum and genital organs.
   In the  black races, pigment cells follow  a similar distribution  in
  * Mondini (Comment. Bonon, t. vii. 1791, p. 29,) was the first observer who made
accurate  microscopic observations on the pigment of the  eye. He stated that the
pigment is not simply mucus, but a true membrane formed of globules disposed in
quincunx.  The son all but completed the work which the parent began: he found
that each globule is made up of little  black points.  Finally, Kieser (De Anamorphosi
Oculi, 1804, p. 34,) described the pigmentary membrane as a cellular tissue containing
corpuscles. 
PIGMENT  CELLS.
2S?
the eye;  but beneath  the  epidermis, as also  under the nails,  they
form a continuous stratum composed of super-imposed layers of cells.
   There  are yet other situations in  which pigment cells have been
encountered: thus, Valentin* has signalized the occurrence of pig-
mentary ramifications in the cervical  portion  of the pia mater, to
which they impart a blackness perceptible to the unaided sight.
   Again, Wharton Jonesf has described a thin  but  evident layer of
brown pigment in the membranous labyrinth of the  ear  of  man.  It
has  been observed  in other mammalia, in. which it  is still more
marked, in the same situation, by Scarpa, Comparetti, and Breschet. J
   The brown spots,  known  by the name of freckles,with which the
faces of most persons are  more or less covered in summer, are due to
a development of pigment cells.
   A development of pigmentary matter frequently takes place as the
consequence of disease;  thus, it is of common occurrence to meet
with growths either  entirely or in part composed of pigment cells, the
tumours,  with  the proper structure of which  it usually thus inter-
mingled, being those of cancer or medullary fungus.
   The  nature  of  the pigment-like matter  found in the lungs and
bronchial glands of aged persons and  animals has been the subject of
much discussion;  nor has  it been as yet decided whether it be true
pigment, or merely  a deposition of carbon.   Pearson§ maintained
the opinion that the  colouring matter  is the powder of carbon, since
neither chlorine nor  the mineral acids act upon it.
   In those remarkable lusus natural, Albinoes, there would appear to
be an absence of pigmentary granules in all parts of the body, even
in the eye: the pigment cells themselves are stated to exist,  but to be
wanting in their characteristic coloured contents.
   Pigment cells do  not present the  same size, form, and  character
wherever  they are encountered.
   Thus, those of the choroid are adherent, large, flattened, polygonal,
mostly hexagonal, with clear nuclei and margins; occasionally, how-
ever, it happens that both nuclei and cell wall  are  obscured by the
number and disposition of the contained granules: the cells are mostly
of uniform size as well as shape, in consequence of which regularity
they form a very beautiful microscopic  object;  sometimes, however,
  * Verlaufund Enden der Nervev., p. 43.
  f Article Hearing in the Cyclopaedia of Anatomy and Physiology, t. il p. 529.
  \ Richerches sur TOrgane de  TOuie de VHomme, Paris, 1836, in 4to.
  { Philosophical Transactions, 1813, pi. ii. p.  159 
288
THE  SOLIDS.
one cell is observed to be larger than the rest, octagonal, and  sur-
rounded by  a number of  cells of smaller size than ordinary,  and
mostly pentagonal.
   According  to Henle,* the contained granules are  situated in the
posterior part of each cell, while the nucleus is placed in its anterior
division;  it is this arrangement which allows of the nucleus being so
clearly  seen;  in  those cases,  however,  in which  the nucleus  is
obscured, acetic acid  will frequently bring it into view; this, if con-
centrated, will dissolve the cell wall, set free the granules, and leave
the nucleus.
   Schwann states that he has  seen the  pigmentary granules in the
cells of the choroid in active motion.
   The cells of the  choroid form by their adherence a membrane resem-
bling the most regular and beautiful mosaic pavement in miniature.
   The  pigment cells  of the  posterior face of the iris  and ciliary
processes are  smaller than those of the choroid, are for the most  part
round, or approach that form, and so filled  with the corpuscles  that
the nucles and margin of the cell is not usually visible.
   In the skin, the pigment  cells are placed between the dermis and
epidermis; they do not there form a layer of equal  thickness, but
accumulate in the depressions left between the  papillae, forming many
super-imposed layers, while  on these they are  spread  out in a single
thin layer, and are often much scattered.   It is to this circumstance,
as well as the  thickness of the epidermis, and the state of repletion of
the cells,  that the varying shades  of the colour of the skin of the
same  individual depend.   In the negro, the cells resemble much in
form those of the choroid, being either perfectly hexagonal, polygonal,
or irregularly  rounded; the  nucleus can be well seen in those cells
which are less filled.
   Among the white race, the  pigment cells in those situations in
which they occur beneath  the  skin are fewer in  number, smaller,
more rounded, and frequently  resemble little  masses of corpuscles
rather than distinct cells;  nevertheless it  is  even  here sometimes
possible to distinguish the nucleus and cell wall.
   There exists between  the internal face of the sclerotic and  the
external of the choroid a fibrous tissue of a brown colour; this, when
these two coats of the eye are separated, remains attached in part to
the one, and in part to the  other; that, however, which adheres to
the sclerotic has received a distinct name, and is called  lamina fusca.
                      * Anat. Gen. vol. vi. p. 295. 
PIGMENT  CELLS.
289
Now, the colour of this layer is due to the presence, scattered among
the fibres, of pigment cells of a very peculiar form and construction;
they are mostly very irregular in size • and shape,  are marked with a
clear central spot, which indicates the locality of the  nucleus, and
from the margin of many  of them proceed filamentous processes of
variable number and size, and the extreme points of which are mostly
colourless, and  are not dissolved by acetic acid.
   Pigment cells of analogous construction exist on the external surface
of the choroid, and also on the cervical portion of the pia mater.
   Mixed up with perfect  pigment cells a greater or less number of
pigment granules are always observed; these are among the smallest
objects in nature, and, on account of their minuteness,  it is in them
that molecular action in all its activity is  best seen:  they  are  not
spherical in form, but are flattened, so that they appear as discs, lines,
or points, according as the surface, side, or  end presents itself to the
eye of the observer.
   It is probable that  it is  by means of these granules  that pigment
cells are multiplied.
   Climate, and particular  states of the system, as pregnancy, have
much effect in  increasing the amount  of pigmentary  matter beneath
the  skin;  from  the   latter  cause, the  areolae around the  nipples
frequently become of a deep chocolate colour.   Of the influence of
the  former, it  is scarcely necessary to cite examples: it may  be
remarked, however, that freckles are due to the development of pig-
ment cells, brought about by the action of the summer's sun.
   This augmented development of pigment cells may be rationally
explained by the increased determination  of blood to the  dermis of
the breast from increased activity of function in that  organ during
pregnancy, and to the general surface from the effect of the sun's heat.
   It is questionable whether all the varieties of colour of the human
species have not  originated in climateric causes, operating through
many ages.
   It may also be questioned whether pigment cells are not susceptible
of being developed  into those of the epidermis.   If the epidermis of
a negro,  raised  from the surface by means of a vesicatory, be exam-
ined with the microscope, it will be noticed that the most external cells
contain  a considerable amount of colouring matter,  which, as this
resides in solid granules and not in  a fluid, it is difficult to suppose
had entered  the cells by endosmosis.
   Pigment cells are capable of regeneration, in a part in which they
                            19 
290
THE  solids.
have  been destroyed: it is  necessary,  however, that the subjacent
dermis be not too deeply injured; the cicatrices remain for a consid-
erable time nevertheless without colour.
   The skin of the children of negro women does not acquire its full
depth of colouring for some days after birth.
   Pigment cells are developed at a very early period of intra-uterine
life.   The uses of pigment in the skin are not well understood;  that
in the eye is doubtless of importance in the discharge of the functions
of that  organ: it is known  that the Albinoes, in whom it  is either
absent or exists but in small quantities, are incapable of supporting a
strong light.
   Pigment cells of particular forms  occur among some of the lower
animals.   Those of the  internal surface of the choroid of fishes and
birds, situated in front of the ordinary coloured cells, have the form
either of short sticks  or clubs.  The argentine  pigment  of the iris
and peritoneum of fishes is composed of elongated corpuscles.   The
pigment  cells  placed beneath the epidermis of the frog  are for the
most part stellate.
                        PIGMENT  CELLS.
  [Pigment  cells are most readily studied on being detached from the
choroid coat of the eye, by means of a fine needle.   On rupturing the cells,
the pigmentary matter escapes;  and with a high  power of the microscope,
numerous black or brown molecules will be observed.  These molecules
measure from niR to gt^oo oi" an inch in diameter.
  These cells may  also  be  studied  with advantage in the  cuticle of the
negro, which may be detached after slight maceration, and also in  the skin
of the frog.
  The pigment cells in the frog, will be found to consist of long, irregular,
jagged processes.
  Cells containing pigmentary matter  are well preserved in the flat cell
with fluid.] 
HAIE.
291
                     ART. XIII. —HAIR.

  We now come to the  description of another  epidermic modifica-
tion, viz:  hairs; these, however, are much  more complex in their
structure  than  any which  have been hitherto described, and are less
obviously  derived from the epidermis.
  As in the case of most of the solids described in this work, we shall
first discuss the different particulars  relating to form and size, and next
proceed to the description of structure.

                          FORM OF  HAIRS.
  Hairs consist of two  parts, a root and a stem: in speaking of the
form of hairs, reference is made to  the latter.  Hairs, then, are elon-
gated, and more or less cylindrical developments of the epidermis.
They depart, however, in most  cases, from the character of  a true
cylinder in two respects;  first, they are not perfectly spherical, but
are  seen  to be, when viewed transversely, either oval, flattened, or
reniform  (see Plate XXIX.); and  secondly, they are not  of equal
diameter throughout, being thickest at about the junction of the lower
and middle thirds of the stem, of smaller diameter from this part down-
wards towards the root, and still more  reduced in  size as the  free
extremity  is approached, and  which, in a hair which has not been
recently cut, terminates in a point, the diameter of which is frequently
several times  less  than that of the more central parts of the shaft.
(See Plate XXIX.)
  This form is best seen in hairs of medium length, as those  of the
whiskers, eyebrows, axillae, and pubis, in which also the flattened and
oval shapes are principally detected.
  The hairs which approach most closely the cylindrical, are those of
the scalp.
  Henle*  makes  the interesting statement, that the curling of hair
depends upon its form, and that the flatter the hair, the more it curls,
the flat sides  being directed exactly towards  the  curve described.
From this it follows, that the hair of negroes would exhibit in a very
marked manner this flattened form.
* Anal. Gin., vol. vi. p. 314. 
292
T HE  SOLIDS
                           SIZE  OF. HAIRS.
  Hairs differ remarkably in size, both as regards length and breadth:
they differ not merely in  different individuals, in  different localities
in tfie same person, but also in any one given  situation, as the scalp
or pubis.
  The hairs of the scalp are the longest;  those of the scalp of women
are many times longer than those of the same part in man, and accord-
ing to the measurements of Mr. Wilson, they are also thicker.   Next in
length come the hairs of the chin of man.   Among women, instances
have been known of the hair extending from the  scalp to below the
feet,  and the beard of man not unfrequently reaches to the waist.
  The shortest and smallest hairs are those covering the general sur-
face  of the body, and which are reduced to mere down (lanugo).
  The thickest hairs of the body are those of the whiskers, chin, pubis,
and axillae; the finest, those distributed over the general surface;  the
hairs of the scalp are of intermediate diameter.
  The hairs of children are finer than those of adults, and those of
the head of men than those of women.
  It  cannot be doubted but  that frequent cutting and  shaving of the
hair tends to increase its thickness.

                       STRUCTURE OF HAIR.
  Each hair admits of division into two parts, the root and stem;
and each of these, again, allows of still further sub-division :  thus, the
root  consists of the prolongation of the hair proper, or  stem, termi-
nating in an expanded portion, which has been termed the bulb, and
of a double sheath; the stem also is divisible into cortex, medulla, and
intervening fibrous  portion, which constitutes the chief bulk of the
hair.  (See Plates XXVIII. and  XXIX.)
  These divisions of the root and stem of hairs suggests its comparison
to a  tree, the stem of which also resolves itself into cortex, medulla,
and intervening woody or  fibrous substance.  The  comparison is also
heightened by the  similar relation in which  both  stand  to the parts
around them, viz:  the soil in the case of the  tree,  and the dermis in
that  of the hair.
                           ROOT OF HAIR.
  We will first describe the root, because it is the  source from which
the hair is  developed:  this, as already noticed, consists of two parts,
the sheath and the bulb. 
HAIR.
•293
   The Bulb.—The bulb is the expanded and basal portion of the stem
 of each hair: it is usually two or three times the  diameter of the hair
 itself,  and is sometimes excavated below: it is constituted of granular
 cells, which are  either circular, angular, or  elongated in form; the
 spherical cells, form the extremity of the bulb, the polygonal ones its
 surface, and the elongated cells  are placed above the spherical  ones,
 of which  they are modifications, and  beneath  the angular cells of the
 surface of the bulb.   Acetic acid will be found useful  in displaying
 the cellular structure  of the  bulb.
   In healthy hairs this bulbous portion of the stem is always coloured,
 which is not the case  with gray hairs.  (See Plate XXVIII.)
   The part of the stem of the hair immediately above  the bulb, and
 included within its sheath, exhibits  the  structure of the body of the
 stem itself, being  divisible into scaly  cortex, fibrous intervening sub-
 stance, and granular medulla.*
   Sheath.—The  bulb and  lower portion of the  stem of the hair is
 included in a sheath consisting of two distinct  layers, an outer and an
 inner.  (See Plate XXVIII. fig. 1.)
   The outer layer is  an inversion of the epidermis: it  first merely
 encircles  the portion of  the stem of the hair beneath the level of the
 epidermis: it next surrounds the inner layer of the sheath, to which it
 soon becomes intimately adherent; finally, it forms a cul-de-sac around
 the bulb of the hair.
   The fact of the inverted  sheath of  the epidermis forming a pouch
 around the bulb of the hair, may be inferred from the  circumstance,
 that when the epidermis peels off as the result of decomposition, the
 hairs usually come away entire with it; its continuation, moreover,
 around the bulb may be shown in transverse sections of the skin  of
 the axillae  and whiskers, in which the hairs penetrate into the  sub-
 cutaneous  fatty substance.   (See Plate XXVIII. fig. 1.)
   This outer layer is colourless, is possessed of considerable thickness,
 and is  evidently made up of granular cells similar to young epider-
 mic cells.
   In most  hairs, whether coloured or uncoloured, which  have been
forcibly removed from the skin, this outer layer is usually torn across,
the rupture occurring almost invariably at a little distance from the
bulb of the hair: the root of the hair, then, below this breach of con-
tinuity, consists only of the inner layer of the sheath and of the stem
of the hair; and at this situation the root, to the  naked eye, appears
                       * See Appendix, p. 549. 
294
THE  SOLIDS.
 contracted:  this is, however,  but an appearance, the result  of the
 absence of the outer layer, and of the expansion of the stem into the
 bulb.   (See  Plate XXVIW. fig. 2.)
   The inner layer of the  sheath is an eversion or  revolution of the
 epidermis, and is  an offset or continuation of the outer layer, com-
 mencing  at  the lower part of the  bulb: it is colourless, possessed of
 considerable thickness, its diameter being about one-third of that of
 the stem of the hair in its thickest part:  it tears  readily in  the longi-
 tudinal direction with a somewhat  uneven fracture;  and hence  may
 be inferred to be of a fibrous constitution, as may be shown to  be the
 case:  its inner surface is marked with reticulated lines, the impressions
 of the cortical scales of the shaft of the hair.
   This inner layer is not of equal diameter throughout, but  tapers
 gradually from below upwards: it  is well defined both internally and
 externally, except  where it comes in contact with the bulb internally,
 with which its inner edge or surface becomes incorporated;  above, it
 terminates in a thin border at a little distance below the level  of the
 skin.   (See Plate  XXVIII. fig. 1.)
   The outer layer, although adherent to the inner at its  lower part,
 does not become incorporated with it: the latter, except at  the point
 indicated, preserves every where its independence and  individuality.
 The two layers, it will thus be seen, might with much convenience
 have  been described, as two distinct sheaths,  an inner and an  outer:
 to do  so, would be, however, to lose sight in some  measure  of the
 similar origin and  nature of the two.
  In the fact, however,  of the inner sheath exhibiting a fibrous  struc-
 ture, and  of  its  incorporation with the bulb, it would appear to have
 more structural affinity with the fibrous portion of the stem of the
 hair itself than with the outer layer or cellular sheath.
  This inner layer might be  appropriately termed  the  "modelling
 sheath" since it doubtless regulates the form  and dimensions of the
 shaft  of the  hair, the substance of which when first developed  is  soft
 and plastic.  Henle describes  the inner layer  as  fenestrated:  this
 structure I have never seen exhibited.

                        Shaft of the Hair.
  The stem or shaft of the hair is divisible, as already observed, into
cortical, medullary, and  fibrous portions.
  Cortex.—The cortical part of the hair consists of a layer of scales,
imbricated upon each other after the manner of tiles upon the roof 
HAIR.
295
of a house.  (See Plate XXIX.)  These scales are best seen in the
larger hairs of the whiskers and pubis, and in the small downy hairs
they are smaller than the ordinary cells of epidermis, and are rarely
seen to  be nucleated.   Maceration  of the hair in sulphuric  acid
causes them to fall off, and in this way their size, form, and structure,
may be satisfactorily studied.
  The scales are absent from the points of the finer hairs.   In  con-
sequence of their imbrication upon each other, their little thickness.
and  of  the  double  contour  presented  by  their  free  edges,  they
frequently convey  the appearance  rather of  anastomosing  fibres
running round the hair than of distinct scales.
  A hair rolled  between  the  fingers always  advances  in  a  given
direction, viz:  towards the apex: this results in part from the taper-
ing form of the hair, and partly from the more or less spiral disposition
of the scales.
  Fibrous  Layer.—The  fibrous  portion of the stem  of the hair
constitutes  its  chief substance  and bulk, forming  two-thirds of the
entire diameter, one-third on each side of the medulla.  In hairs which
are not too dark, the constituent fibres may be seen in situ:  they are
most palpably  brought into view either  by scraping  the hair with a
knife or by crushing it after masceration in sulphuric acid:  they are
also best seen in  the larger hairs and near the centre  of the shaft.
  Henle describes the fibres as flat, with  uneven edges, and  is in
doubt  as to whether  they are branched or not.  To my observation
they appear much smaller than  they are stated to  be by Henle, and
are spherical and simple.   (See Plate XXIX.)
  These fibres  have a cellular origin, and are formed by the elongation
of the inner cells of the bulb, in which  their gradual extension into
perfect fibres may be traced.
  They are stated by most observers not to  extend  to  the  extreme
point of the hair; and the same statement is likewise made in refer-
ence to  the medullary canal and  cortical scales.  Of what, then, it
may be fairly asked, is the point of the hair constituted, since  every
structure entering into the formation of the shaft is denied  to  it?
The assertion  that the fibres do not extend to and form the apex of
the hair is  evidently erroneous.  In the examination of the  points
of a number of hairs which have not been recently cut, fibres,  often
separated from each  other and loose, will frequently  be detected.
(See Plate XXIX.)
  The whole of  the  fibres of the  stem, however,  do not extend its • 
296
THE  SOLIDS.
 entire length, the majority terminating long before the extremity is
 attained; and it is to this fact that the attenuated form  of the  hair
 is  attributable.   In some hairs  the fibres are seen to terminate at
 regular distances, their points describing transverse lines on the stem
 of the hair.
   The splitting, of such common occurrence in hairs which are
 allowed  to  attain an  excessive  length, is due to a separation  of the
 fibres from  each other.
   The fibrous portion in young and healthy hairs is coloured.
   Medullary Canal and Medulla.—In most  hairs which are  not of
 too deep a colour a medullary canal may be detected running up the
 centre.  This  commences  in the upper  portion  of the bulb, runs
 along, the shaft, but ceases as it approaches the apex:  its diameter
 varies with that of the hair itself, but  usually bears the proportion of
 a  third of its thickness.   (See Plates XXVIII. and XXIX.)
   Henle is uncertain whether this  canal  is lined by a distinct mem-
 brane or not, but inclines to the opinion that it is so.
   The medulla or contents of this canal exhibit a granular appear-
 ance, and are made up of pigment granules, a few perfect pigmentary
 cells, and particles of coloured oil;  it  is therefore in the medulla that
 the greatest amount of colouring matter of the hair is situated.  (See
 Plate XXVIII. fig. 1.)
   At the very commencement in the  bulb of the hair, the  medulla
 has distinctly a  cellular origin.
   In young and healthy hairs it is also continuous throughout  the
 entire  extent of the medullary canal;  in old and  discoloured  hairs,
 on the contrary, its continuity is  frequently interrupted by distinct
 intervals,  and it only partially fills  the cavity of the  canal  even
 where  it  is present.
   The medullary canal  and medulla is best seen in the larger  hairs,
which  are  not  of too  deep a colour, and  in gray hairs: in the fine
and downy  hairs of the  general  surface of the body, the canal and
its contents, as a necessary consequence, are almost entirely absent.
   In some rare  instances, two medullary canals have been observed
in  the  same hair.  In the sable, the medulla has a distinctly cellular
structure throughout.*

 * The first accurate observations on hair were made by Hook, Micographia, 1667,
Obs. 32. tab. v. fig. 2., and Leeuwenhoek, Opera, t iv. p. 46. 
HAIR.
297
                        FOLLICLE OF THE HAIR.
   Each  hair is implanted in a distinct depression in the dermis, the
base of which  especially is freely supplied with nutrient vessels: this
depression is  also lined by an  invagination of the epidermis, and
which becomes ultimately the outer layer of the sheath of the root
of the hair as already described.  (See Plate XXVI. fig. 3.)
   Between  this layer, however, and the shaft of the hair for a short
distance before it  rises above the level of the skin, a space or cavity
is left; into this space  the  canals of one or more  sebacious  ducts
generally open, and in it also entozoa frequently develope themselves.
   It sometimes happens that two or more hairs are  contained in the
same follicle (see  Plate XXVI.j^g". 3): in these cases, however, each
hair has a distinct modelling sheath.  In  some animals,  the location
of a number of hairs in one sheath is the ordinary mode of arrange-
ment; in the pig,  for example, the hairs are usually thus associated in
three's, as also occasionally in man.
   The hair follicle or crypt  is best seen by  examining thin vertical
slices of the skin.
   The length of the hair follicle and the consequent depth of implant-
ation of the hair  varies, but is often equal to the twelfth or sixteenth
of an inch; the hairs of the head, of the whiskers, of the pubis, and
of the axillae, penetrate into the sub-cutaneous cellular tissue; those of
the eyelids and ears,  to the subjacent cartilages:  the  roots of hairs in
general,  however,  do not penetrate beyond one-half the depth of the
corium, in the substance of which they are buried.
   It is usually stated that the bottom of the follicle  is occupied by a
papilla furnished with blood-vessels and nerves, on which the bulb of
the hair immediately rests;  and that it is owing to this papilla that
the base  of the bulb, when removed, exhibits a concavity.  This
description,  in the case of tactile  hairs, may be correct, but is surely
not so when applied  to hairs in general.   Each hair does indeed rest
upon a papilla, but it is  one which  is destitute of blood-vessels and
nerves, and  which is cut off from all direct vascular communication
by the cul-de-sac  formed by the  outer lamina of the  sheath.  This
papilla  may be described  as a compound  cellular vesicle, and is
probably the true  germ of the hair; it  is on  it that the bulb of the
hair  is situated,  and which occasions  the  depression which this
generally displays  when  it has been  forcibly  extracted.  This  germ
is best seen  in gray and  light-coloured hairs. 
298
THE  SOLIDS.
                          GROWTH OF HAIR.
  The growth of hair takes place at the root, and is the effect of the
development of new cells, which is continually in progress in the bulb,
and which afterwards become modified into those of the scaly cortex
and fibrous stem;  these new cells, coming behind the older ones, contin-
ually press them forwards, and thus occasion the elongation of the hair.
  But the elongation of each hair takes place in a manner very differ-
ent from that just mentioned, not from the development of  new cells,
but by the  gradual  elongation  and extension  of the cells already
formed after they have quitted the bulb, and when they come to form
the shaft of the hair.   This mode  of  elongation—it can scarcely be
called  development—is proved by the gradual tapering  of the  hair
which takes place after the point has  been removed:  of  the truth of
this fact, not the slightest doubt can be entertained.
  At  the period of puberty, a growth of hair takes place in certain
situations in  which previously it was not  apparent, as on the chin,
cheeks, in the  axillae, and on the  pubis, abdomen, and chest;  this
development is an effect of the great functional activity which exists
at that period, and which is the  occasion of  the increased  and rapid
growth of the several constituents of the body which then takes place.
  The earliest periods  at which the rudiments of hairs in the human
foetus have been observed is from the  third to the fourth  month:  the
hair follicle is formed  in the  first  place, next the bulb, and then the
sheath and stem of the hair, which,  in the early period of its develop-
ment, is curved upon itself.
  Hairs are occasionally developed  in certain peculiar situations, as
on the mucous membrane of  the conjunctiva, the intestines, and  gall-
bladder, in the ovaries, and in steatomatous and encysted tumours.
  Hairs  may be  transplanted, and, it is said,  will grow after such
transplantation in consequence of the  adhesions and organic connex-
ion established between them and the  adjacent tissues—a fact of
which practical advantage  might be taken if correct.
  When a hair has obtained the  full term of its development, accord-
ing to the researches of Eble, it becomes contracted  just above  the
bulb: this change probably announces its death and approaching  fall.

                       REGENERATION OF HAIRS.
   Hairs are peculiarly susceptible  of  being affected by the condition
of the health, even more so than the epidermis.   If this be vigorous, 
HAIR.
299
 as a rule to which there  are  many exceptions, it will be found that
 the hairs themselves are thick, and firmly set in  the skin: if, on the
 contrary, the powers of the system be debilitated from any cause, the
 hairs will either fall off spontaneously, or a very slight degree of force
 will serve to dislodge them from their connexions.
   If the bases of those hairs which fall out of themselves be examined,
 or which are removed by combing and  brushing, it will be seen that
 the bulb alone has come away, the entire sheath  and germ remaining
 behind.   In such cases, the hair is doubtless regenerated, and after
 its regeneration, is usually stronger than it was previously.   (See Plate
 XXIX.)
   It has not yet  been ascertained by positive experiment whether the
 hair is capable of reformation in those instances  in which both bulb
 and sheath have been removed:  it is  most probable, however, that
 where  they have been entirely abstracted, no  renewal  of the hair
 could ensue.
   It is possible that in some cases  the  apparent  regeneration  of the
 hair arises, not from the development of new hairs in the primitive
 sheaths and upon the old germs, but from the  formation  of new hair
 follicles and germs:  of this, however, no proof has as  yet been given.
   That a regeneration of new shafts of hair is continually in progress,
 whether from new germs or the older ones is not known, is proved by
 the detection of  small and pointed  hairs just emerging from the skin
 in the scalp of even old persons.

                         NUTRITION  OF HAIR.
  Hairs are nourished in the same  way as the epidermis  itself; that
 is, they do not receive into their own structure either blood-vessels or
 nerves,  but derive their nutriment from vessels which are so distrib-
 uted as  to come into close  contact with the  tissues to be nourished.
  This  indirect reception  of the nutrient plasma explains the very
 great susceptibility of the epidermis and its  several modifications to
 be influenced by causes affecting  the general health, and in conse-
 quence the circulation and the qualities  of the circulating  fluid.
  The epidermic tissues being placed in situations  the most remote
from  the  centre  of the circulation, are endowed with but a  feeble
degree of vitality, and which is readily destroyed by causes affecting
the  amount and nature of the circulating fluid received by them.
  The nutrient vessels and sentient nerves of each hair are distributed
around and outside the sheath, and not in a raised papilla, as generally 
300
THE  SOLIDS.
 described, although this may really be the case in the large hairs of
 the whiskers of some animals, as, for example, the tactile hairs of the
 seal, &c.  The fact of the hair usually penetrating below the level of
 the true skin  and into the sub-cutaneous  fatty tissue seems to  dis-
 prove the notion of a distinct and vascular papilla.

                        DISTRIBUTION  OF  HAUIS.
   Hairs are distributed over the entire surface of  the body, with the
 exception of the palms  of the hands, soles of the feet, and last phalanx
 of the toes and fingers: there  are, however, situations in which they
 are developed in  increased quantities, as on  the  integument of the
 scalp, on that  of the eyebrows, on the margins  of  the ciliary cartil-
 ages, and after the period of puberty, on the chin, cheeks, axilla, pubis,
 abdomen, chest, and at the entrance of the nares and ears.
   The number of hairs found in these  several situations differs very
 considerably in different  individuals, according to age  and condition
 of health.
   Individuals  of the male  sex  also are generally more hairy than
 females, in whom also no development of hairs takes place on the chin,
 cheeks, chest, and abdomen.
   Of the number of hairs which exist on  the entire surface of  the
 body, some  idea may be  formed from  the measurements of Withof.
 The quarter of a square inch furnished 293 hairs at the synciput, at
 the chin 39, at the pubis 34, on the fore-arm 23, at the external border
 of the back of the hand 19, and on the anterior  surface of the thigh
 13.   Upon  the same extent of  surface, Withof counted  147 black
 hairs, 162 brown, and 182 flaxen.
   Hairs of great length  and strength are often developed in  consider-
 able quantities in different parts of the  body, in moles and naevi.

                         DIRECTION OF HAIR.
   The hair follicles are not placed vertically in the skin, but obliquely,
 and the hairs which issue  from them consequently themselves run in
 the same oblique direction.  (See Plate XXVI. fig. 3.)
   The apertures of most of the follicles look  downwards, and hence
 we find in most cases that the points of the hairs, when fully devel-
oped, are similarly directed.
   In addition,  however,  to this general arrangement and distribution,
it  will be seen that in early life the hair follicles are disposed in lines,
 the apex of one follicle nearly touching the base of the next: the lines 
HAIR.                          301
 thus  described  are not straight,  but are more or less curved, and
 divergent or convergent, after the manner of the lines upon  the case
 of an engine-turned watch: the hairs which issue from  the follicles
 thus take particular and determinate sweeps, which it is unnecessary
 to describe in detail.
   It occasionally happens,  from some  cause or other, that  the hair
 follicles are implanted in a manner the  reverse  of that which should
 obtain: this is especially seen  in those of  the scalp of children, in
 whom frequently  certain tufts of  hair grow  up, and incline in  a
 direction opposed to that of the contiguous hair.  This mal-disposition
 of the hair is  the source of much trouble  and annoyance to anxious
 nurses and mothers, who spend much time in endeavouring to bring
 the refractory lock into order.
   In this endeavour there can  be no question but that it is possible to
 succeed, as is proved by the very different  arrangement  which the
 hair of the head is made to  follow in accordance with the manner in
 which it is dressed.

                          ERECTION OF HAIR.
   Man, to a certain extent, and many animals in  a considerable degree,
 possess the power of erecting the hairs.   This power in man is limited
 to the hairs of the head, in many animals it is much more general.
   Most persons, on sudden exposure to cold, and on experiencing of
 any emotion of fear or horror, feel a creeping sensation pass  over the
 head:  this  sensation is accompanied by  a certain  degree of  erection
 of the hair, but not indeed to such an extent as  to cause it "to stand
 on end."  Now, this erection is the result of the distribution  of fibres
 of elastic and contractile  tissue  throughout the  substance of the
 corium, and which, interlacing among the hair follicles, occasion the
 erection of the hairs themselves.
   The distribution  of these fibres, and their connexion with the bases
 of the hairs, are well seen in the skin of the hog.

                          COLOUR OF HAIR.
   The colour  of the hair depends upon  the same cause as that of the
skin and eye, and is due to the presence of pigment granules and cells;
these  are  contained principally in the medullary canal, but  are also
interspersed between the fibres of the stem;  they  first become manifest
in the upper portion of the bulb of the hair.
   The depth of the colour of the hair very generally bears a relation 
302
THE  SOLIDS.
 to the development of pigmentary matter in other parts of the system,
 as  in  the  eye and beneath the skin.   To  this rule, however, some
 remarkable exceptions are occasionally encountered.
   The colour of the lighter hairs, as the red and flaxen, would appear
 to depend less upon the number and depth of colouring of the pigment
 cells  and granules, than  upon the presence of minute globules  of a
 coloured oil.
   In the hair of Albinoes but little colouring matter is present; and in
 gray hairs, also, the colour has deserted the pigment cells and granules.
   Hair is decolorized by long contact with chlorine.
   It is generally  stated as an undoubted fact,  that the hair may turn
 white, or become colourless, under the influence of strong and depress-
 ing mental  emotions, in the course of a single night.   This singular
 change, if  it does ever occur in  the  short space of time  referred to,
 can only be the result of the transmission of a fluid possessing strong
 bleaching properties along the entire length of the hair, and which is
 secreted in  certain peculiar states of the mind.

                             GRAY  HAm.
   If a gray hair be contrasted with an unaltered one  from  the head
 of the same person, the following differences will be noticed between
 the two.   The gray  or  white  hair will  be  observed to be  almost
 colourless, the bulb and fibrous portion will be  destitute of colour, the
 medulla alone retaining a slight degree of coloration:  this, however,
 is collapsed, and in place of being continuous  throughout its length,
 will be seen to be interrupted at intervals.  (See Plate XXVIII. fig. 2.)
  The unaltered  hair, on the contrary, is distinguished  by characters
 the reverse  of those exhibited by the gray hair; thus, the bulb, stem
 and medulla are all deeply  coloured, and the latter  fills the entire
 cavity of the medullary canal, and is continuous throughout.   (See
 Plate  XXVIII. fig.  1.)
  Gray hair retains a considerable degree of vitality, as is proved by
 its growth continuing for many years after its loss of colour.

                         PROPERTIES OF HAIR.
  Hairs  are remarkable for their strength, their elasticity, durability,
 and for the difficulty with which  they undergo the process of decom-
position: their strength results probably from their fibrous constitution;
in  their elasticity and durability, they partake of the character of all
 horny  structures. 
HAIR.
303
  The strength of hair  is proved  by the fact that a single hair will
bear a weight of 1150 grains.
  Its elasticity is shown  by the readiness with which each hair, when
extended, returns to its original size and shape, as well as by the  fact
that the numerous  hairs forming  a curl or lock will  recover  their
ordinary form and disposition after extension.
  Its durability is shown by the persistence of hairs throughout many
years of life.
  Lastly, its indestructibility is proved by the occurrence of hairs in
the tombs of persons buried for ages.
  A  hair, however, which has been  very forcibly extended, will not
return to quite its  original length, but will  remain a certain degree
longer  than it was previous to  the  extension.   A  hair  may be
extended a third of  its length without breaking; elongated a fifth, it
remains a seventeenth longer than  it was before; it continues a tenth
longer after having been  extended a fourth, and a sixth only  after
having been drawn  out as  much as possible.
  Hairs, when they are dry, become electrical by rubbing, and emit
sparks: this  is well  known with respect to  the coat of the  cat, and
Eble has observed the same thing to occur in man.
  Hairs are also eminently  hygroscopic, and  imbibe moisture  from
the air and  from the skin, in consequence of  which they lose  their
set  or curl, and become flaccid and straight.
  Nitrate of silver blackens the  hair, a sulphuret  of silver being
formed, and it is of this  ingredient  that the majority of hair dyes are
chiefly constituted.  The concentrated mineral  acids,  especially the
nitric, dissolve  the hair, as  does also caustic potash.
  When heated, hairs take  fire, and burn with a fuliginous flame,
emitting the odour  of bone, and leaving a  residue of carbon.  To
dry distillation, they yield a quarter of their weight of carbon, which
is difficult to incinerate, the products  being empyreumatic oil, water
charged  with ammonia,  and combustible gases,  which comprise sul-
phureted hydrogen.  The ashes contain oxide of iron, traces of oxide
of manganese and silica,  and of sulphate, phosphate, and carbonate of
lime.
                    THE  HAIRS OF DIFFERENT  ANIMALS.
  The precise structure  of the hairs  of different animals varies con-
siderably: those of the mammalia resemble the hairs of man, or differ
only  in the  degree of  their development, as the  whiskers of the
carnivora and rodents, and manes and tails  of horses, the bristles of 
304
THE  SOLID.
pigs, &c: it is in these largely developed hairs that the structure can
be best determined:  thus, in  the  majority of them it is stated to be
easy to detect the vessels and nerves of the papillae  on which the
bulb rests, and which penetrate into it:  nerves have been detected
by Eble in the cat,* by Rapp in the seal, porcupine, and many other
animals, f and by Gerber in the pig4
  In  the  hairs of the musk-deer, there  seems to  be  no separation
of parts  into  scaly cortex, fibres and  medulla, the  entire hair being
uniformly cellular.
  In that of the sable, the fibrous portion is absent, and there is only
scaly cortex and cellular medulla.
  In the hairs of most rodents, the medulla is divided by dissepiments,
and  in other  animals, as the sable, it is composed of large and dis-
tinct cells.
  The hairs of the mouse, bat, and martin, are branched or knotted.
  In the spines of the porcupine and hedge-hog, the inner bark pene-
trates in longitudinal bands into  the  cavity of the medullary canal,
and  thus  divides the medulla itself into incomplete  segments ;  the
transverse view of such spines represent a starred or rayed figure.
  In  birds, hairs are replaced by feathers, which  are to be regarded
as modified hairs.
                          THE  USES OF  HAD?.
  The uses of hair are manifold.
  In  certain  situations, as on the head, it is to  be regarded as an
ornament.
  In other localities, as on the cheeks and chin, it imparts character
and expression to the face.
  In others again, as on  the  pubis  and about  the  genital organs, it
serves the purpose of concealment.
  The general use of hair, wherever encountered, it being  a  non-
conductor of caloric, is to preserve the warmth of the system.
  Those situated at the entrance  of the nares and meatus auditorius
externus, are placed there to prevent the  entrance  of foreign  bodies,
insects, &c.
  It is difficult to assign any use to the hairs of the axillae.
  It is very probable  that hairs have other uses, and that they exert
some influence in regulating the electric condition of the body.

  * Von den Haaren, t. 11. p. 19.   f Verrichtangen desfreuflen Nervenpaares, p. 13.
  J Allgemeine Anatomic, p. 79. 
HAIR.
305
                                HAIR.
  [Plate LXX., fig. 4, represents transverse sections of the human hair.
  Transverse sections  of the hair,  sufficiently thin to show  the  cellular
structure, are somewhat  difficult to make.  When an instrument  can be
obtained, such as is used for making thin sections of wood, they  can be
prepared by taking a number of hairs, and gluing them together by means
of some adhesive material, so as to form  a solid mass.   This bundle is then
placed in the machine,  properly wedged,  and the transverse sections  readily
made.
  Another method, is to puncture a cork with a fine  needle, and insert or
drive hairs in it; when a sufficient number of hairs have been thus intro-
duced, thin sections of  the cork may be made with a sharp scalpel or razor.
In these sections will be found some  of the hairs cut transversely, and suffi-
ciently thin to show their structure.
  Sections of the beard  may be  obtained  by repeating  the operation of
shaving a couple  of hours after the beard was  first cut; on the razor will be
found minute points of  hair.  Some of these, when separated and spread out
with the needle, will exhibit transverse, others longitudinal sections.
  When these are sufficiently thin to show their structure, they should be
mounted  dry; but if too  thick to  show  well in this condition, they may be
rendered more transparent by being mounted in balsam.
  The hairs of different  animals  present  great varieties  of structure,  and
their study will be found replete with interest.]
20 
306
THE  SOLIDS.
                   ART.  XIV. —CARTILAGES.

   Cartilages are among the most solid structures entering into the
constitution of the animal^organization; they are, however, not less
remarkable for their elasticity and flexibility than for their solidity.
   The  essential  element of the several  fluids and  solids  hitherto
described in the course of this work, we have  seen to be cells:  this
cellular composition is exhibited in a high degree by cartilages.
   The texture and colour of the cartilaginous tissue varies consider-
ably: it presents  either a white or bluish-white  semi-transparent and
homogeneous appearance, or it is yellow, and exhibits a fibrous texture.
   These differences of texture and of colour indicate a difference of
structure, upon which a division of cartilages into the true and fibro-
cartilages has been based.

                          TRUE CARTILAGES.
   True cartilages  consist  of cells, contained in cavities, which are
themselves formed in a solid and hyaline inter-cellular substance.
   They comprise all those cartilages which cover the articular extre-
mities of the bones (that of  the glenoid  fossa and of the head of the
inferior maxilla alone excepted), the cartilages of the entire respiratory
apparatus (with the exception of the epiglottis and the  cuneiform car-
tilages), those cartilages which are to a considerable extent free  and
independent, and  which have been denominated figured cartilages, as
those of the ribs,  the ensiform cartilage; the trochlea  of the eye, the
nasal cartilages, and the Corpuscula triticea in the lateral hyo-thyroid
ligaments.   (See  Plate XXX. figs. 1  and 2.)
   The true cartilages are distinguished from the fibro-cartilages by
their  bluish and transparent aspect.

                  Structure of True Cartilages.
   True cartilages consist, as already mentioned, of hyaline  matrix,
cavities, and cells; each of  these constituents  will be described in
succession.
   Hyaline Matrix.—The inter-cellular  substance, or hyaline matrix,
although it does not usually present any distinct traces of organization,
yet contains, scattered through it, numerous granules of different sizes,
and many of which are to be regarded as the cytoblasts from which
new cells are continually being developed. 
CARTILAGES.
307
   The amount of this inter-cellular substance varies in different car-
tilages, and is greater in fully-developed than in very young cartilage.
   Cavities.—The cavities of true cartilages vary both in size and form;
in shape they are irregular, although for the most part elongated.
   They are,  in  most cases, to be regarded as simple excavations or
fossae in the hyaline matrix;  in others, however, it would appear from
the observations of Henle,*  Bruns,f and Schwann,J that they are
lined  by a distinct  membrane, and which is  indicated  by a  double
contour, by the difficulty experienced in  setting free  the  contained
cells,  and by the fact that, by boiling, the inter-cellular  substance is
dissolved, while the  cavities remain as distinct corpuscles.
   Such  cavities would stand in  the relation of parent cells to those
which they include.
   Cells.—The cells of cartilages are very different from  those occur-
ring elsewhere in the animal  organization; they are distinct in their
form  and in the character of  their contents.
   Cartilage cells, like  the cavities  in which  they are enclosed,  are
irregular  in  size and shape;  they are, however, generally elongated,
sometimes flattened and compressed; at others, they are perfectly
spherical: these several shapes depend upon the degree of pressure to
which the cells are subject, and which is greatest at the free margins
of the cartilages where the compressed form occurs, and least in  the
centre where the spherical cells are chiefly encountered.   Each  cell
contains a nucleus,  which is  either smooth or granular; it includes
also very generally  one or more shining  and globular  bodies  of an
oleaginous or fatty nature,  and  which,  in many  cases, are  to  be
regarded as transformed nuclei.
   The cells usually lie as it were scattered irregularly throughout the
inter-cellular substance; in some cases, however, they are arranged in
definite order; thus, in  the condensed margin of all the true cartilages
the cells are compressed, and  lie  with their long axes disposed parallel
to the surface.  (See Plate XXX. fig. 1.)  Again, in the ribs, they
radiate in straight lines from the  centre towards the circumference:
this disposition of them accounts for the fibrous fracture which they
exhibit when broken across, as also for the fact of their  being  divis-
ible into thin transverse layers.  The linear arrangement of the cells
in the fully-developed cartilages  of  the  ribs  is very frequently  not
perceptible.
   In very thin cartilaginous laminae,  as those forming the alae  of  the
* Anal. Gin., vol. vii. p. 364.     t  Allg. Anat., p. 215.    \ Mikrosk. Untersuch 
308
THE  SOLIDS.
nose, the difference in the form of the central and* peripheral cells
does  not exist, the entire inter-cellular substance  being filled with
small and rounded cells.
   The  cells  usually occur  singly  in the hyaline matrix; they are,
however, frequentlv encountered in groups of two, three, or four cells,
each  of which is distinct, and describes a  more or  less regular seg-
ment of a circle:  this disposition of the cells is  connected with their
mode of multiplication, as will be seen hereafter.
   Again, groups of secondary cells sometimes occur, especially in the
inter-vertebral fibro-cartilages, included in the membrane of the pri-
mary or parent cell.   (See Plate XXXI.)
   Moreover, Henle* has  noticed a peculiar arrangement of the cells
of the cartilages which cover the articulating surfaces of the  larger
bones.  On the free surface, the cells are as in most cartilages  small,
flattened, and disposed horizontally; the deeper seated  cells  become
larger and  longer; their axes, on the  contrary, being directed  either
vertically or  obliquely to  the  surface;  sometimes also  the  cells,
although separated by  distinct intervals, are arranged the one  above
the other in such a manner  as that the superior appears to be a con-
tinuation of the inferior;  at others, an inferior cell appears to divide
into two others, placed above it, and thus  represents  a bifurcation.
Henle also states, that  he  has seen not unfrequently the outline of a
cavity prolonged from  one longitudinal series of cells to a neighbour-
ing series.   It is very possible, Henle goes on to  observe, that  these
cavities form part of a system of elongated  canals, which, taking  an
undulous course,  and  sometimes bifurcating, traverse  the cartilage
from its inferior to its superior surface,  and which, when one makes
a section, are divided  into  two portions, the one remaining in one
segment, the other in the  other segment.  This structure, he proceeds
to remark,  explains sufficiently why articular cartilages  exhibit  a
fibrous fracture, and why the earlier  observers  believed them  to  be
composed of fibres which ran perpendicularly to the thickness.
   This  ingenious notion of Henle, although it serves to  account for
some hitherto unexplained phenomena  connected with  the articular
cartilages, is yet of very doubtful application even to them, and cer-
tainly no such arrangement of the cells and cavities  as that just
described belongs to the majority of true cartilages, or  to any of the
fibro-cartilages.
   Near the surface, the articular cartilages  are  more laminated, and
may be separated into  thin lamellae.
                     * Anal. Gin., vol. vii. p. 366. 
CARTILAGES.
309
   In the smaller articular cartilages, the number of cavities and cells
is more considerable, and the superficial layer of cells is not so well
marked: the peripheral cells are small indeed, but  for the  most part
rounded;  a few are found in the neighbourhood of the bone, of an
elliptical figure, but the middle layer presents circular cavities, with
cells which are either single or multiple.
   Nuclei.—The nuclei contained in cartilage cells are mostly granular,
but sometimes  present a smooth aspect, and then are scarcely to be
discriminated from particles of oil or fat: in form they are sometimes
rounded, but in general they are irregular in  shape, and follow more
or less  closely the contour of the cells  in  which they are enclosed;
they also frequently enclose  a nucleolus.
   Usually but a single nucleus is contained in each cell; occasionally,
however, two, three,  and  even  several are included within it; and
sometimes it happens  that  one or more of these is  invested by a dis-
tinct cell-membrane.   (See Plate XXXI.)
   The  cells also  include,  as already remarked, particles  of oil of a
globular form  and of a shining aspect; it has been suggested that
these may probably in some cases be transformed nuclei.
   The distinction of cartilages into  true and fibro-cartilages, although
useful  for  the  purposes  of classification, is to some extent artificial;
since,  on the  one hand,  some  of  the true  cartilages, as old age
approaches, become converted  into  fibro-cartilage, and on the other,
the fibro-cartilages themselves,  in the early period of their develop-
ment, do not contain fibres, the  cellular substance being hyaline, and
identical with that of true  cartilages.
   The conversion of hyaline cartilage into fibro-cartilage has been
observed  to occur only in those  cartilages  which  are  subject  to
become ossified, as those of the ribs, the thyroid, &c.
   Where  ligaments are inserted  into true cartilaginous tissue, this in
the neighbourhood of such insertion always  exhibits  a fibrous struc-
ture, in consequence  of the fibres of the ligament penetrating into
the inter-cellular  substance.   These fibres  are of a nature  totally
distinct from proper cartilage fibres, as will be seen hereafter.

                          FD3RO-CARTILAGES.
                                                                 <
   Fibro-cartilages  differ chiefly from true or hyaline cartilages,  in
that the homogeneous inter-cellular substance is replaced in them by
fibres  endowed with  elasticity;  a transformation of structure  of
which we have seen  that  certain of the  true cartilages are  suscep-
tible.   (See Plate  XXXI.) 
310
THE  SOLIDS.
  The fibro-cartilages include those of the articulations which are
united by synchondrosis, as the intervertebral cartilages, and that of
the symphysis pubis; the epiglottis and the cuneiform cartilages; the
articulating  cartilages of the glenoid cavity, and  of the head of the
superior  maxillary-bone; the  inter-articular cartilage of the sterno-
clavicular articulation; the cartilages of the ear, of the Eustachian
tube,  of Santorini, and those of Wrisberg.
  There are,  however, other differences besides  the structural  one
alluded to;  thus, fibro-cartilages  are more opaque than the true, are
of yellow colour more or  less deep, and are endowed with a higher
degree of elasticity and'flexibility.
  The fibres  do not follow  the  same  distribution in  every  fibro-
cartilage: thus, in the tube of Eustachius, in the  symphysis pubis, in
the inter-articular  cartilage of the  sterno-clavicular articulation, in
those of the tempero-maxillary articulation they  are placed nearly
parallel to each other; in  the inter-vertebral cartilages, they ascend
vertically from one osseous surface to the other; in the  cartilages of
the epiglottis and ear, they are curved and interlacing.
  In  the outer part of each inter-vertebral cartilage,  the fibres form a
distinct and compact stratum of a yellow colour, no  cartilage cells in
that situation  intervening between them; the number of fibres, how-
ever, gradually diminishes  towards the centre of the cartilage, which
at the same time becomes  less and less dense and firm, until at length
in the very  axis it is semi-fluid.
  The cells  of fibro-cartilages do not differ very materially in form and
structure from those of true cartilages; they usually, however, contain
more fat, are more readily separable from the fibrous base in which they
are lodged, and oftener encountered in the condition of parent cells.
   The cells of the inter-vertebral  cartilages and  of the  epiglottis
present some interesting  forms  and  modifications: thus,  the  cells
which are situated  in the harder parts of those  cartilages are, on a
vertical section, seen to be narrow and much elongated; while  many
of those imbedded in  their soft  and central parts are large and per-
fectly globular;  many others of  these,  again,  are  in  the  condition
of  parent cells, and enclose either  numerous nuclei  or else  many
perfectly-formed secondary cells; lastly, cells occasionally present
themselves  made up of concentric vesicles  enclosed one within the
other.   Groups  of adherent  nuclei  are also frequently  met  with
deprived of an investing  membrane."  For  representations of these
several forms of cells, see the figures. 
CARTILAGES.
311
  Henle*  describes  as occurring in  the  epiglottis  certain  large,
spherical, or oval cells, presenting  in  their interior an oblong cavity,
from which proceed little branched tubes, which extend in  all direc-
tions, even to the surface of the cells. These cells would appear to have
some analogy with the osseous corpuscles.  I have made diligent search
for them in  the epiglottis, but hitherto have failed to meet with them.
  The fibro-cartilages are not soluble to the same extent in boiling
water  as  the  true, which  are almost entirely so, and  therefore yield
less chondrine or jelly.  The cells  of  these cartilages  also resist the
action of the  water for a longer period than the inter-cellular sub-
stance, f
                        NUTRITION OF CARTILAGE.
  Cartilages are among the number of non-vascular substances—that
is, they  do not, in general,  receive  into  their own  tissue distinct
blood-vessels,  but derive  their nourishment from those which are
distributed  to the parts adjacent to them.
  Thus, the articular  cartilages are supplied with nutriment from the
vessels which are so freely distributed to the extremities of the bones;
in young children, and sometimes even  in adults, the synovial mem-
brane  which  covers  the free  surfaces of the cartilages also carries
vessels which assist in their nourishment.
  The independent or figured cartilages, as the  ribs, &c, are sur-
rounded by a  membrane, composed of condensed cellular  tissue,
called  the perichondrium:  in this membrane the vessels which afford
nutriment to  the enclosed cartilages, ramify.  The  ribs,  moreover,
contain grooves or canals, which, commencing  on  the inner edge
of the rib,  first run towards the centre, and then continue to pass
forwards for some distance: these  canals also contain blood-vessels.
  In the  centre of ribs about  to  ossify, a distinct  medullary canal,
containing blood-vessels in abundance, is clearly perceptible.
  Vessels are also contained  in the  fatty masses  enclosed  in some
of the  joints, and  called the glands  of Havers; from  these the
adjacent cartilages  doubtless imbibe a portion of nutrient plasma.
  Among  fibro-cartilages,  the  synchondroses  are  stated to receive
vessels.   Nerves  have  not, as  yet,  been discovered  in  cartilages,
which may be irritated for any length of time without  the slightest
pain being occasioned.
  * Anal. Gin., vol. vii. p.  370.
  f Meckauer (Carlilag. Structura, 1836,) appears to have  been the first to give,
under the direction of Purkinje, a complete and accurate description of the cartilages
of the human body. 
312
THE  SOLIDS.
  During ossification, between the cartilage  to  be converted  into
bone and that which is to remain as the articular cartilage, a layer
of vessels passes, which, as the ossification advances, gradually retire,
and wholly disappear soon after birth.
  As cartilages  do not contain vessels, they are not subject to those
disorders which  depend upon errors of the circulation; that  is, they
are not  liable  to  inflammation and its  consequences.  Ulceration
of cartilages is indeed described by writers; but this term is wanting
in accuracy when applied to the erosion of which cartilages are
susceptible,  and  which  is effected not through any operation occur-
ring in the cartilage itself, but through the action of vessels  which,
proceeding from the synovial membrane, dip down into the cartilage,
and occasion its partial absorption.  For  the same reason,  cartilages
do not readily become atrophied by pressure: thus, when an aneurism
destroys  the bodies of the vertebrae, the inter-vertebral cartilages are
not at the same time removed, but resist for  a long period the con-
tinued compression to which they are subject.
  There is, however, one description of cartilage in which blood-
vessels regularly appear, viz:  cartilages of ossification, in which may
be included the costal and thyroid cartilages, their presence proceed-
ing and accompanying the process of the formation of bone.
  Cartilages, like all  the  extravascular tissues, imbibe  fluid readily:
thus, when immersed in a coloured solution, they assume the  tint of
the liquid in  which they are  placed.   In  jaundice,  according to
Bichat,*  they present a greenish yellow tint, from the imbibition of a
portion  of the bile  with which, in this  disorder, the  system is so
pregnant.

                GROWTH AND DEVELOPMENT OF CARTILAGES.
  Cartilages, as already observed, consist of cells imbedded in a  hyaline
or fibrous base.  In considering, then, the development of cartilages,
the growth of both the cells and the inter-cellular substance must be
discussed.
  We will first describe the multiplication of cartilage cells.
  The Ce//s.—Cartilage cells are multiplied in two ways.
  1st. By the division of a single cell into two or more parts, each of
which becomes,  when the separation is completely effected,  a distinct
cell.  The reality of this method of increase in the number of cells
will become evident, on the attentive examination of almost any thin
                       * Anal. Gen., t. iii. p. 192. 
CARTILAGES.
313
section of cartilage, in the cells of which, but especially in those placed
near the  natural border, the  several stages of their division  may be
clearly and satisfactorily recognised.   (See Plate XXX.)
  2d. By the development of cytoblasts either in the inter-cellular
substance, or else in parent  cells.   This mode of increase  is a true
reproduction,  new cells  being  continually formed  and  developed.
The first process of  multiplication is of a nature totally distinct from
reproduction; for although by it the cells are multiplied, no new ones
are developed.   There is the same  difference  between the two forms
of cells, that having  its origin in the division of a single cell, and that
developed from a cytoblast, as there is  between  a slip and a seed.
(See Plates XXX. and XXXI.)
   The parent  or  primary cells,  filled with the  second or even the
third generation of new cells, may be detected in abundance in almost
any cartilage,  but especially in the inter-vertebral cartilages.   It is
worthy of notice, that the parent  cells  are usually situated near the
centre of each cartilage, while the single cells, in which the process
of division is best seen,  are  mostly found outside  these.   From this
arrangement we may infer that the deeper-seated cells are older than
those of the circumference.   Whether the latter are derived from the
former, or whether  they are  formed on the  external margin of the
cartilage, it is not easy to decide;  it is most probable, however, that,
from the circumstance  that the parent cells are principally found in
the centre of the thicker cartilages, and that it is in this situation that
ossification commences,  that the second conjecture is the correct one.
   It is a singular fact, that the development of cartilage cells may be
as readily followed out in old cartilages as in young, numbers of cells
in process of division and in  the stage of parent cells being readily
distinguished in each.   As after maturity cartilages do not undergo
any increase  in size, and as from the preceding observations it would
appear that new cells are continually being evolved, it must be pre-
sumed that the very old  cells are absorbed and then place supplied
by tfie younger ones.
  In the  multiplication of cartilage  cells  by division, a correspondence
may be traced between cartilages and  many of the»lower tribes of
animals and vegetables, especially with the  majority of the algae; and
in the  development  of secondary cells in parent cells, they exhibit a
still closer analogy with certain algae of the genera Hcematococcus and
Mycrocyslis, the cells of some of  the  species  of  which it would be
impossible to distinguish from the isolated cartilage corpuscles of the
epiglottis and inter-vertebral cartilages. 
314
THE  SOLIDS.
   In these methods of multiplication,  cartilage cells would appear
 almost to stand alone in the animal economy: thus, it is certain that
 the  red blood corpuscles, epithelial cells, and their various  modifica-
 tions into epidermis, nails, pigment cells, and hairs, are not multiplied
 either by division or by the  development  of secondary, enclosed in
 primary or parent cells.
   The analogy existing between the cells of cartilages and those of
 certain algae has been  noticed by Dr. Carpenter, in the third  edition
 of his "Principles of Human Physiology."
   The Inter-cellular Substance.—Very young cartilages, and also the
 smaller ones of adults, are constituted almost entirely of cells, with but
 little admixture of inter-cellular substance.  As, however, these young
 cartilages grow in size, the relative amount of this substance increases,
 and  the space between  the cells becomes greater.
   The augmentation of the inter-cellular substance takes place prin-
 cipally by a deposit  of new layers on the exterior  surface during the
 period  of the  development of cartilages;  this  mode  of increase is
 proved by  their separation after long-continued maceration into dis-
 tinct laminae.
  A second mode of increase of the inter-cellular substance has been
 stated to exist by Henle,*  principally in the cartilages of ossification,
 and  under no circumstances in the fibro-cartilages, viz:  by the thick-
 ening of the walls  of the  cells, which become  confounded with  or
 melted down into the inter-cellular substance, the cavity in which  the
 cells are lodged being diminished, or this also augmenting at the same
 time.  The proofs adduced in favour of this method of increase  are
 not convincing.
  It  has already been  stated  that  in  the  true cartilages which  are
 subject to ossification, fibres appear; these fibres, as well as the anal-
 ogous ones of fibro-cartilages, are probably of a nature wholly distinct
 from those  of ordinary cellular tissue, and which  have their origin in
cells; under no circumstance can either cells or nuclei be discovered
in the fibres of cartilages.
  Cartilage is not capable of regeneration: when it has been frac-
 tured, the union of the surfaces is very incomplete, and principally by
means of cellular tissue.
  The formation of cartilage almost invariably precedes the develop-
ment of bone, of which  we shall shortly have to  speak  more particu-
larly in the  Chapter on  Bone.
                     * Anal. Gen., vol. vii. p. 376. 
CARTILAGES.
315
  Masses of cartilage are also occasionally produced upon the exter-
nal surface of the  synovial  membrane of joints;  these  are  at  first
peduncated, but at length cease to have any connexion with the organ-
ization, and move freely about in the cavity of the joints.
  Occasionally, though rarely, cartilage is developed in  the  cellular
tissue of glands, forming a solid tumour, which was first described by
Miiller, under the name of Enchondroma, and of which I recently had
the pleasure of receiving a very excellent example from Dr. Letheby.

                         USES OF CARTILAGES.
  The uses of cartilages are of a mechanical nature,  depending upon
certain physical properties.
  Thus, we  find them  to  be situated in localities where solidity is
required in combination with flexibility and elasticity.
   In the larynx, the flexibility and elasticity of cartilages assists in the
modulation of the voice.
   In the  nose,  so liable to injury,  their flexibility often  allows this
organ  to sustain severe blows without detriment.
   The articular cartilages  protect the bones from injury to which they
would be otherwise so subject in the sudden and violent  exertions of
the body, as in jumping, on account of their solid and unyielding nature.
   The inter-vertebral  cartilages are exceedingly elastic  and  flexible,
and permit  the free movement of the spinal column  in almost any
direction, and which is so necessary in the execution of the various
motions of the body.
  The  articulations united  by synchondrosis, as that of the pubis,
are remarkable for their strength, although at  the same  time it admits
a slight degree of extension and compression.
   Lastly, the epiglottis is  enabled  to preserve the erect position so
essential to the  maintenance  of life in consequence  of its exceeding
elasticity. 
316
THE  SOLIDS.
                             CARTILAGE.
  [For an elaborate and complete  account of "the intimate structure of
articular cartilage," see a paper on that subject, with plates, by Jos.  Leidy,
M. D., of Philadelphia, published in vol. xvii. (new series) of the American
Journal of Medical  Sciences, pp. 277-294.
  The development of cartilage is of course best studied in the fcetal subject.
  In  the  adult, cartilage  may be  examined  in their  vertical  sections.
Articular cartilage is easily separated from bone,  after slight immersion in
acid.
  Preparations of cartilage should be preserved in cells with fluid.

  Plate LXX., fig. 5, Cartilage from the finger-joint, showing terminal loop-
                      ings of vessels.] 
BONE.
317
                        ART.  XV.—BONE.

   The next tissue to be considered is the osseous.
   Bones  are  divided after their form into long, flat, and irregular:
 long bones consist of a body or shaft termed diaphysis, hollowed out
 in the centre  into the medullary canal, and of two extremities called
 Epiphyses, and which in early life are distinct from the shaft; each
 long bone, moreover, is made up of two  modifications of bony struc-
 ture,  the cancellous  and the tabular; the former is loose and reticular,
 the  latter hard and  compact:  of the  one, the great  bulk  of the
 epiphyses are  constituted;  of the other, the diaphysis is chiefly formed:
 in flat and irregular bones, the  medullary canal is wanting; the first
 consist of an  inner and outer table of compact bony tissue, enclosing
 a thin plate of cancellous structure, termed Diploae, and the  latter
 are composed principally of cancelli, enclosed in thin and irregular
 osseous laminae.

                         STRUCTURE  OF BONES.
   The two elements into which all bones  resolve themselves  are
 osseous corpuscles and laminae; the latter, according to the plan of
 their  arrangement and development, give rise to the cancelli, medul-
 lary canals, and plates of which bones are constituted.

                      Cancellous  Structure.
  The cancellous structure of bone is made  up  of  thin and inoscu-
 lating plates of bony matter, which enclose spaces between them, and
 all of which freely communicate with each other : these spaces are
 called  medullary cells.   Each  plate is also compounded of several
 laminae, in the intervals between which a few bone corpuscles exist.
  The fact of the free communication of the medullary cells is proved
by the two following experiments :
  Thus, when mercury is poured into a hole made in the exremity of
a long bone, or on the surface of a  flat or short  one, it will traverse
all the  medullary cells,  and escape by  the apertures which  exist
naturally on the exterior of bones.
  Again, if a  bone  be cut  through at  one of its extremities,  the
natural openings on its surface being at the same time closed, and if 
318
THE  SOLIDS.
 then the bone be exposed  to the action of heat, all the marrow will
 escape slowly by the cut extremity.*
   The spaces described by the  medullary cells are irregular in size
 and form, those which are  first developed being smaller than those of
 older formation (see Plate XXXIV. fig. 3, 4):  they are usually of
 an elongated shape, their long axes being parallel to that of  the bone
 itself:  when viewed  transversely, they  are seen to  be more or less
 rounded, but irregular in outline: it is in the transverse sections that
 the bone cells and lamellae  are best seen.
   Medullary cells in the recent  state are filled with fat vesicles, with
 blood-vessels, and with granular  nucleated  cells analogous to those of
 epithelium: these last occur in considerable quantities in the cancelli,
 and especially in those of foetal  bones, in which  the  fat  vesicles are
 for the most part absent.   (See  Plate XXX. fig. 4.)
   They inosculate freely with  the medullary  canals situated in the
 outer and compact plates of bone.

                      Canalicular  Structure.
   The compact tissue  of  bones is  traversed  by canals,  which have
 been termed medullary from the fact of their being  in communication
 in the long bones with  the great central medullary cavity, and from
 the circumstance of their being  partly occupied with medullary
 matter.   They are also called Haversian, after their discoverer.
   These canals are  situated between the laminae  of which bone is
 composed, and take  a course in the long bones, in which  they are
 best seen, parallel  to their  axes, being also joined  together  by short
 transverse branches:  they  thus  form a net-work of tubes analogous
 to that exhibited by the minute  vessels which they convey and pro-
 tect; the form and sizes of the  meshes vary:  in the long bones they
 are elongated.  (See  Plate XXXII. fig. 4.)
   They communicate, in. the long bones, with the  medullary cavitv,
dilating into cells or vesicles,  from which a short tube  proceeds
previous  to their entrance into  it;  they also open  upon the  external
surface of all bones by somewhat expanded apertures, and inosculate
freely with the medullary cells.
   Medullary canals  are not all of equal diameter throughout  the
compact  tissue of a bone;  those situated between the external plates
are two or  three times smaller than  those which  are placed more
internally.   (See Plate XXXII. fig.  l.)
                *Bichat, Anatomic Generate, t. 111.  p. 25. 
B O N E .
319
   In a  transverse  section, the canals are seen to be either circular,
 oval, or rarely angular.
   In the flat bones, the course of the medullary canals is more irreg-
 ular  than in  the  long  bones; in the parietal  bones they  proceed
 diverging from the parietal protuberance towards the margins of the
 bone; and  in  the  frontal from the supra orbitar  ridge  towards the
 coronal  suture.
   In the long bones, near their extremities and  in the vicinity of the
 articular cartilage, these  canals  end in blind or cascal extremities, a
 single canal passing  up into each of the prominences, into a number
 of which the articular surface of bone is elevated.*
   It is these canals, which impart the striated structure presented by
 bone,  and  which  is visible to the  unassisted  eye;  in  longitudinal
 sections, they  are frequently cut through, and their cavities exposed.
   The contents of medullary canals are similar to those of the medul-
 lary cells, of which they are to  be regarded as a modification, there
 being an insensible transition from the one to the other.
   Drs. Todd and Bowman recognise two forms of Haversian canals,
 one of which  carries veins, the  other arteries, a single vessel being
 distributed to each; those canals which  contain the  veins are stated
 to be larger  than those which convey the arteries, and to be dilated
 into a pouch or sinus at the situation where two or more  canals unite
 to form a single larger tube.

                            Lamella.
   The more essential constituents of true and  fully developed bone
 are, as already observed, lamellae  and bone cells; the medullary cells
 and canals just described are merely definite spaces existing between
 the lamellae, the arrangement and ultimate structure of which we shall
 in the  next place proceed to notice.
   It is principally by the successive development of new lamellae that
 bones increase in diameter; these are usually deposited in the direc-
 tion of the  axis of the bone;  if, therefore, a transverse  section of a
 long bone be made  and examined  with the  microscope, the lamellae
 will be seen  to be arranged as follows:  First,  several layers will be
 observed  to pass entirely round the bone; secondly, others  will be
 noticed encircling  each  Haversian canal; and  lastlv,  irregular and
incomplete lamellae occupy the angular spaces  intervening between
* See Med. Chir. Rev. No. x. p. 528. 
320
THE  SOLIDS.
 the sets of lamellae concentrically disposed around each canal.   (See
 Plate XXXII. figs. 1, 2, 3.)
   The number of layers  which  pass  interruptedly around the  bone
 are not very numerous, being generally less than twelve; the amount
 of those  which encircle each Haversian  canal varies  from two or
 three to upwards of twelve, the smallest  number of lamellae usually
 appertaining to the smallest canal.   (See  Plate  XXXII. fig.  1.)
   Examined with an object-glass of the fourth of an inch focus, the
 lamella, after the separation of its earthy matter by means  of dilute
 hydrochloric acid, exhibits a delicate structure,  the precise nature of
 which it is not easy to determine;  its surface will be seen to be marked
 out into innumerable lozenge-shaped spaces, one side of each of which
 is concealed by a dark shadow, and the divisions between which are
 without shadowr.   (See Plate XXXIII. fig. 4.)
   This interesting  structure was first distinctly pointed out by Dr.
 Sharpey,* who  conceives that it arises from the  crossing and union
 of fibres; these, however, cannot be traced out and displayed as sepa*
 rate  fibres, owing,  it is  presumed,  to their being united or fused
 together at the points where they cross each other; it sometimes  hap-
 pens, however, that at the torn edge of a lamella a short projecting
 process may be seen, which presents much the aspect of a true fibre.f
   The appearance presented by a lamella thus figured might  be com-
 pared to the engine-turned  case of a watch, and  it might also be con-
 ceived that it  was  produced by the union of a  number of diamond-
 shaped cells, and not by the crossing of fibres.
   One argument in favour  of the fibrous constitution of the lamellae
 may be derived from the fact that the  cancelli of bone in process of
 development clearly exhibit a fibrous structure.
   Cross sections of the lamellae may also sometimes be observed to be
 marked with short and radiating  lines, which most probably  depend
 upon the structure already noticed.
   The osseous  lamellae  are  likewise  perforated  necessarily with
 numerous minute  apertures occasioned by the canaliculi of the bone
 cells, and which, when seen with a low power, appear like so many
  * Quain's Anatomy, 5th edition, part ii. p. cxlii.
  f It would appear to be probable, from the  following quotation, that Henle had
 seen the structure above described.   " The lamellae examined on their flat side  have
appeared to me to be generally hyaline or finely dotted, but sometimes also fibrous;
the fibres are either pale, and as though composed of grains, or obscure and rugged;
one never succeeds in isolating them for a certain space, because  they are branched
interwoven, and, in a word, perfectly identical with the fibres of fibro-cartilages." 
BONE.
321
 small dots;  they contain, also, scattered  throughout their substance,
 multitudes of granules of earthy matter.
   The only really necessary constituents of bone would appear to be
 the cellular  tissue and earthy matter.   The combination of these two
 forms bone in its simplest condition.   The medullary cells, Haversian
 canals, and bone cells, are connected only with the growth and nutri-
 tion of bone, and occur seldom, except  where the size of the bony
 formation renders their presence necessary for its growth and support.

                           Bone  Cells.
   Distributed throughout the cancellous and compact portions of bone,
 cells of a peculiar structure occur in considerable quantities.
   Concerning  the nature of these  cells, much difference of opinion
 prevails; by some they are described as mere vacuities existing in
 the tissue of the bone; by others  as  hollow  cells, as nuclei of cells,
 and as  true nucleated corpuscles.   That the bone cells take their
 origin in nucleated cells, cannot be doubted.
   The circumstances which have given rise to the notion of their
 being mere vacancies or lacunae,  are the passage of fluids through
 them, their infiltration with solid matter, and the optical appearances
 sometimes presented by them.  All these circumstances admit, how-
 ever, of explanation on the supposition of their corpuscular origin.
   That they are derived from granular cells may be proved, it seems
 to me, by the study of the development of bone, they being in growing
 bones first traceable  as  nucleated  corpuscles, a  condition  to  which
 they may be again reduced in  an adult bone by the removal  of the
 earthy matter.   This appearance is best seen in the large bone cells
 of the Siren, Proteus, or Menobranchus.
   The bone cells, which are very numerous,  are situated between the
 osseous laminae already described, and by which they are compressed;
 they thus present in all sections of bone an elongated or flattened form,
 and in transverse cuttings those facing the Haversian canals  appear
 not merely elongated, but also  slightly curved, the concavity  of the
 arc being directed inwards towards the canals, and the convexity out-
wards in the contrary direction.  (See Plate XXXII. figs.  1, 2.)
  When viewed as transparent objects, they  appear black, and when
as opaque, they are of a pearly whiteness.
  From the  margins of each bone cell proceed a number of branched
canals, which, passing through the lamellae situated on either side of
the cell,  inosculate freely with  the  canaliculi given off by the bone
                           21 
322
THE  SOLIDS.
cells of the contiguous lamellae (see Plate XXXII. fig. 3); this pro-
cess of inosculation being frequently repeated between the cells of
each lamella, a communication is thus established between the  me-
dullary cavity  on which the canaliculi of  the  first  series of cells
opens,  the  Haversian canals, and  the  external surface of the bone.
The reality of this communication  may be  attested,  by applying a
drop of oil of turpentine to a section of dry bone placed beneath the
microscope, when the passage of the fluid through the bone cells may
be followed with the eye.  This experiment was first suggested by
Drs. Todd and  Bowman.
  The canaliculi of bone cells treated with  acid usually disappear, the
body of the cell alone remaining.
  The size of the bone cell throughout the whole of that osseous ver
tebrate series, stands in relation to that of the red blood disc; and Mr.
Quekett, who has instituted  an inquiry into their form and size in a
great variety of animals, has arrived at the conclusion that the class
to which any animal belongs, whether  that of Beasts, Birds, Reptiles,
or Fishes,  may be determined by the two  particulars referred  to.
This discovery  is likely to be especially useful in the determination of
the  true position in the animal series of many fossil bones,  which but
for  it,  would have continued to be enveloped in uncertainty  and
conjecture.
  In many osseous fishes, the bone cells appear to be wanting, they
having merged  into canaliculi, which are often of considerable size.

                       Marrow of Bones.
  The medullary cavity of adult long bones, the medullary cells, and
the larger medullary canals, all contain a loose cellular tissue, in  the
meshes of which a greater or less  amount  of marrow or fat cells is
enclosed.   (See Plate XXX.^s. 3,  4.)
  In fcetal  and very young bones  the fat vesicles  are wanting in  the
three situations named, the place of fat being  supplied by immense
numbers  of the small granular nucleated  cells, which have already
been referred to.   (See Plate XXXIII. fig.  5.)
  It has been stated that the medullary cavity, cells, and  canals  all
communicate freely; the marrow therefore and its enclosing cellular
tissue are every where continuous.

                          Periosteum.
  The external surface of all bones, with the exception of their artic- 
BONE.
323
 ular  extremities, is covered with  a dense membrane composed of
 fibrous tissue, which is very rich in blood-vessels, and which is called
 the periosteum.
   The internal  surface  of the  medullary cavity, cells, and larger
 Haversian canals, is also lined by a vascular membrane  much more
 delicate in structure, which may be regarded as an internal periosteum.
   It  is by means of the vessels  which ramify  through  these mem-
 branes that the nourishment of the bone is secured.

                          Vessels of Bone.
   Bones are richly supplied with blood-vessels, which penetrate every
 part  of their structure.
   Thus externally, branches,  principally  arterial, proceed from the
 periosteum, enter the  numerous apertures of the Haversian canals,
 and,ramifying through these, form a capillary net-work; these external
 periosteal vessels may be  seen with the unaided eye, extending into
 the bone like so many fine threads, on the  cautious detachment of the
 periosteum.
   Again, in the long bones, a  large artery penetrates by an  oblique
 canal situated  at the junction of their upper  and middle thirds, into
 the medullary  cavity, and sends  branches upwards and downwards,
 which ramify  on the  membrane  of the  medulla or internal perios-
 teum; some of these proceed onwards into  the  medullary cells, and
 others inosculate with the capillaries of the Haversian canals  already
 referred to.
   The flat and irregular bones are furnished not  with  a single vessel
 of large calibre, but with several of smaller size.
   These larger arteries are accompanied by veins, whereby a portion
 of the venous blood is returned from the bone.
   Breschet,* moreover, has described in the flat bones, and especially
 in those of the cranium, a  system  of osseous canalc,  which contain
 only veins, and which are furnished with valves, which is not the case
 with the other veins of bones.
  The walls of these canals, which ramify after the manner of vessels,
 are pierced with  apertures, by which they receive small  capillaries:
 they traverse principally the spongy portion of bones, afterwards they
pass through the compact part, and  finally terminate on the external
surface of the bone.
  * N. A. N. C. xxiii. P. i. p. 361.; Richerches Anat. Physiolog. el Pat. sur le  Sys-
teme Veineux, Paris, 1829. fol. 
324
THE  SOLIDS.
   These canals are best seen in the flat bones of the cranium, which
should be dried, and the outer table of compact substance removed.
   Lymphatics have been observed in some few instances in bone.

                        Nerves of Bone.
   Nerves have not hitherto been  satisfactorily traced  into bones;
nevertheless, the  great pain experienced in diseased conditions of
them proves incontestably the existence of nervous fibrillae.

                  GROWTH AND DEVELOPMENT  OF  BONE.
   Growth of Bone.—The situations in which the chief increase of
bone occurs are commonly stated to have been accurately determined
by means of the different madder experiments instituted by numerous
observers.
   If an animal be  fed for a short time with  the root of madder, its
bones will become tinged  with the colouring matter of that plant,
between which and the phosphate of lime of the bone a great affinity
exists.
   On a close examination of sections of a growing long bone it will
be observed, however, that  the tissue of the bone is not uniformly
coloured, but that in a transverse  cutting the colour is principally
situated in the outer part.  The same fact is shown also in longitudi-
nal sections, which, however, if they embrace the entire length of the
bone, will also be  observed to be tinged with the colouring matter
towards either extremity.
   Again, if a magnifying glass be applied to a thin transverse section
of the growing bone of an animal fed  upon madder, each Haversian
canal will be seen  to be surrounded by its ring of colour.  For  this
beautiful illustration of the effects of madder we'are indebted to  Mr.
Tomes.  (Plate XXXIII. fig. 6.)
   These several observations have been presumed to prove that bones
increase  in  length principally by additions of new  matter to their
extremities,  and in breadth by the deposition of new laminae of bone
on their outer surface, as well as  by the formation of fresh lamellae
in each Haversian canal,  which last grow and expand in size simul-
taneously with the laminae  placed external to them  after their  first
formation.
   Now, although it is very probable that bones increase in  diameter
to a great extent by the addition of  new matter on the external  sur-
face, and although it is quite certain that they become elongated by 
BONE.
325
 the  formation  of bony matter at their extremities, it appears to  be
 most clear that we are not justified in coming to any  such conclusion
 from the results of the experiments with madder.   All that these cel-
 ebrated experiments really seem to prove is, that bones in contact
 with blood-vessels containing the colouring matter of madder, readily
 imbibe and retain that principle in common with the liquor sanguinis.
   The bones of old animals are coloured with  much  more  difficulty
 than those of young;  a few hours in very young animals being suffi-
 cient to ensure their colouration.
   Development of Bone.—We come now to  consider the exact pro-
 cess of the development of bone.
   Bone is developed either in membrane or in cartilage; when in the
 former, it  may be  termed intra-membranous, and  when in the latter,
 intra-cartilaginous ossification.
   Intra-membranous Form of Ossification.—We  will consider, first,
 the intra-membranous form of ossification.  Dr.  Nesbitt* was the first
 to distinguish between the two types of ossification.  More recently
 Dr.  Sharpeyf  has described clearly  and satisfactorily the steps of the
 intra-membranous development.   This form  he considers  to belong
 to certain flat bones of the cranium, as the parietal and portions  of
 the frontal and occipital bones, as well as to the outer surfaces of the
 long bones.
   The first perceptible ossification of the parietal bone, which  may be
 selected as one of the best examples of this form of osseous develop-
 ment,  consists  of  a net-work of spicula  of  bone, the outermost  of
 which radiate in lines  towards the circumference,  and are connected
 by short transverse branches.  (See Plate XXXIII. figs. 1, 2.)
   As the ossification proceeds, the first formed spicula, in the centre
 of the bone, become greatly increased in thickness,  and the spaces
 between  them  much diminished in  size; the ossification  continues
 thus to spread and consolidate until the parietal meets the neighbour-
 ing bone, with  which it is at length united by suture.
  If, however,  the microscope be brought to bear upon one of the
 newly-formed spicula  before the entire bone has  attained any con-
 siderable development, it will be  seen that the  ossific deposit takes
place in  the fibres of fibro-cellular  tissue, intermingled with which
numerous granular and nucleated cells occur; these fibres, which are
disposed in bundles, invariably precede the deposition  of bony matter,
  * Human Osleogony, Lond. 1736.
  f Dr. Quain's Anatomy, edited by Mr. Quain and Dr. Sharpey,  5th edition. 
326
THE  SOLIDS.
 and mark out the course of the future spicula.   (See Plate XXXII.
 fig- 3.)
   The granular cells just noticed have been observed by Dr. Sharpey,
 who remarks upon  their distribution in the direction of the future
 spiculae, and who considers that  they are connected in some way or
 other with the process of ossification.
   There can  scarcely be a question but that they are  the bone cells
 in a rudimentary state, their conversion into which it is not difficult
 to trace.
   Now, it does  not  appear that  cartilage is at all  concerned in  any
 one stage  of the development of the parietal bone  of the  human
 embryo.  In that of the sheep, and some other animals,  a lamina or
 cartilage is present in connexion with  the parietal bone;  but this takes
 no part in the process  of ossification, but merely serves as a support
 to the newly-developed bone, and extends beneath the  first-formed
 portion of it alone.
   As the ossification advances  still  further, the interstices between
 the first-formed  spicula  become filled up, grooves appear on the sur-
 face of the bone; these radiate from the centre towards the circumfer-
 ence, and ultimately become converted into canals, which, being lined
 with a number of concentric laminae, at length constitute the com-
 plete Haversian canals.  The bone is then completely formed.
  Intra-cartilaginous  Ossification.—It has, until recently, been sup-
 posed that the formation of bone always takes place in cartilage; this
 notion, as we have seen, is erroneous.
  Ossification is also usually described- as the conversion of cartilage
 into bone;  this idea will be presently  shown to be equally erroneous,
 and the fact demonstrated that the intra-cartilaginous ossification does
 not differ essentially from the intra-membranous form.
  If the microscope be brought to bear upon a thin longitudinal sec-
 tion of an  ossifying  fcetal bone, in connexion with its  cartilaginous
epiphysis, the following particulars will be noticed:
  First, it will be observed that the cartilage cells in the neighbourhood
of the bone, instead of being scattered irregularly throughout the inter-
cellular substance, are arranged in several consecutive and alternating
rows or files,  the lowermost of which dip into and are surrounded by
osseous cups  and septa; that the  cells forming the lower portion of
the lowest tier are larger, and less compressed, than those which enter
into the formation of the upper part of  each lower series, and that they
are separated from each other by distinct portions  of  inter-cellular 
BONE.
327
 substance.  Secondly, it will be remarked that the extremities of the
 still soft bony spicula invade and extend into the spaces which inter-
 vene not merely between the rows of cells, but also between the indi-
 vidual cells,  and further, that granular  and probably cytoblastemic
 particles are  deposited in  this inter-cellular substance,  particularly
 where this comes into contact with the cartilage  cells themselves.
 (See Plate XXXIV. figs. 1. 4.)
   As the process of ossification advances, the cell-wall of the cartilage
 cells becomes absorbed; granular corpuscles  are next generated in
 the primary cancellus;  after which  the  nuclei of the cartilage cells
 (which are observed to become smaller, the  deeper they lie in  the
 bone) are removed by absorption;  finally, the small septa intervening
 between the individual cartilage cells are removed, the larger medul-
 lary spaces being thus formed.  (See Plate XXXIV. fig. 4.)
   Furthermore, in  these precursory and even in the  older spicula,
 fibres analogous to those in which the spicula of the  parietal bones
 are developed, may be abundantly detected.
   Such is a brief sketch of the several steps of the intra-cartilaginous
 form of ossification.
   Now, the process which we have just described, is constantly in
 progress;  cartilage cells on the one side  are continually being devel-
 oped in the epiphysis; they are also constantly marshalling themselves
 into rows or columns, the lowermost cells of which  dip into the can-
 celli and become absorbed ; on the other side, the cancelli of the bone
 are continually invading the inter-cellular spaces of the cartilage.
   It is thus that a bone grows in  length.  Each epiphysis of a long
 bone, however, after  a time,  becomes a centre  of ossification; this
 proceeds to meet that of the shaft; a layer of  cartilage usually, how-
 ever, intervenes between the two, until the period of the full develop-
 ment of the osseous system, when this layer becomes absorbed, and
 the shaft and the epiphysis become consolidated by bony union.  The
 first trace  of  ossification of  the epiphysis in the human  subject is
 usually apparent at about the ninth month.
   We have now  to ask ourselves the  question, how does the bone
 increase in diameter?  We have shown that it is generally considered,
 as proved by the madder experiments already referred to, that a long
bone increases in  breadth by the deposition of  new lamellae  at  the
circumference, as well as in the cavities  of the medullary and Haver-
sian canals; but we have seen also from what has been  already said
in reference to the different sizes of the external and internal Haver- 
328
THE  SOLIDS.
sian canals and their mode of formation, that each of these canals is
continually  undergoing a  process  of expansion, and  it is by this
expansion that the chief increase of the diameter of a bone takes place.
It was formerly supposed that a layer of cartilage existed in all grow-
ing bones on their external surfaces, but we now know that  such is
not the case, and that  the  new osseous deposit  takes place in fibres.
If it were necessary that a  layer of  cartilage should exist in the situ-
ation named, it would be equally requisite that  it should  be present in
each medullary cell, and in each Haversian canal.
  The small granular  corpuscles already referred to as occurring in
the cancelli  of all bones, but especially in those of the foetus, it would
thus appear are  developed in considerable quantities at a very early
period of the development of bone; they are generally apparent in the
third or fourth tier of  the first formed and small cancelli,  and while
the nuclei of the cartilage cells yet exist.  (See Plate XXXV. fig. 3.)
  It will now be  perceived that  the intra-cartilaginous form of ossifi-
cation is  identical with the  intra-membranous  type in  all essential
particulars.
  It will also  readily be  seen that  this view of the  process of ossifi-
cation differs  very considerably from the more recently  expressed
opinions on  the subject; those, for example, of Drs.  Todd  and Bow-
man, and  of Mr.  Tomes.
  The authors of the "Physiological Anatomy" consider  that  the
nuclei of  the  cartilage cells  become developed  ultimately into  the
bone cells.
  There are many considerations which would lead to the conclusion
that such a transformation is but little  probable, the  following of
which may be referred to:
  The formation of bone,  independent of cartilage,  as  in the intra-
membranous type of ossification.
  The small number of the  cartilage cells, compared with the vast
quantities of bone cells which exist in even a young  bone.
  The  impossibility of  explaining  why  the  permanent  cartilages
should not, like the temporary, be constantly  subject to ossification,
since they are both organized in precisely  the same manner.
  The proof that cartilage cells have no further stage of development
to pass through, manifested by the fact of the occurrence  of parent
cells in all cartilages, whether temporary or permanent.
  The chief new points contained in Mr. Tomes's views* are  the
       * See Art. "Osseous Tissue,"  Cyclop of Anatomy and Physiology. 
BONE.
329
ossification of the walls of the several cartilage cells which form each
roll or column, and the  conversion of a  number of these, by the
absorption of the contiguous walls of the cells into a single cavity or
tube, which becomes filled with a granular blastema;  this tube Mr. T.
considers  to be  an Haversian  canal, and its wall  to  constitute  ulti-
mately the outer lamina of such canal.
  The arguments adduced in  disproof of the opinion that the nuclei
of the cartilage cells become  converted into bone corpuscles, apply
with equal force against the idea  of the calcification  of the walls of
the cartilage cells.
  Bone Cells.—Bone cells, then, according to the views of the author,
are not transformed  nuclei of cartilage corpuscles,  but take their
origin in  distinct granular cells, which may be clearly seen in the
growing spiculae of bone dispersed among the  fibres in which the
earthy matter of bone is first deposited, and which at length become
entirely imbedded in the earthy deposition.
  As, however, it is most probable that a  development of bone  cells
and new laminae of bone  are ever  in progress  even  in  adult bones,
we should expect  to encounter in the cancelli of bones of every age
fibres of cellular  tissue and granular cells;  both  these  do  occur  in
them, and especially the latter, which are met with in great numbers.
  These granular nucleated cells  are more numerous in foetal and
young bones  than in those of older formation;  in  the former, indeed,
they almost entirely fill up the cavities  of the cancelli: in the latter,
although they  are still numerous, their place  is supplied  with fat
vesicles, which are not present in the former.
  It seems to  me to be  not  improbable  that two kinds of granular
cells may  exist in  the medullary  spaces, &c, one  consisting of rudi-
mentary bone cells, and the other connected with the elaboration of
marrow,  which occupies  the  medullary cavity, medullary cells, and
larger Haversian canals.
  It might be supposed that these  granular cells were the white cor-
puscles of the blood escaped from the ruptured vessels, the red blood
discs having been absorbed; this  notion is,  however, disproved by the
fact that many of them are much  larger  than the colourless corpus-
cles of the blood.   (See Plate XXXIII. fig. 5.)
  The existence of a granular  blastema in  the cancelli, &c., of bones
was first observed by Drs. Todd and Bowman,*  who considered that
it was concerned in the development of blood-vessels.
                    * Physiological Anatomy, chap. v. 
330
THE  SOLIDS.
  Presuming it to be proved that the bone cells are derived from true
corpuscles, we  have yet to decide  whether we  are to believe with
Schwann,*  that they are complete  cells, and  that the  canaliculi are
prolongations of the walls of these cells;  that,  in fact, they possess a
structure conformable  with that of  the  stellate pigment cells of the
skin of the frog, or of the lamina fusca of the eye;  whether we are
to consider with  Gerber,f  Bruns,J and E. H.  Mayer,§ that they are
the  nuclei  of primitive elementary cells, and that  the  canaliculi are
prolongations of these; whether, again, we are to  regard them with
Henle||  as  the cavities of  cells,  the walls  of which  have  become
thickened, and the canaliculi of which proceed from the  central cavity
through the thickened  walls of the  cells, as  do the porous canals of
many vegetable cells;  lastly, whether  we are  to believe, with Todd
and Bowman, that the canaliculi proceed from  the nucleus, which
afterwards becomes absorbed, and that thus the lacuna is left.
  That the  first view is the correct  one, and  that  the  bone cells are
to be regarded as  complete corpuscles, the  canaliculi  of which are
formed by the extension of the cell wall,  is, I think, proved by watch-
ing the formation and  development  of bone cells in growing spiculae
and by the action  of dilute hydrochloric acid, which, by removing
the  earthy matter, allows the granular texture,  which originally char-
acterized them, to be again seen.
  The last points left  for consideration  in reference to the develop-
ment of bone are,  the modes  of  formation  of the medullary cavity,
medullary cells, and Haversian canals.
  Formation  of Medullary Cavity.—Traversing  the  substance of
each cartilaginous  epiphysis, a number of large and branched canals
may be seen in both transverse and longitudinal sections.   (See  Plate
XXXV. figs.  1, 2.)
  The majority of these proceed*directly  from the ossified  part of
the shaft in connexion with the epiphysis; in  this  situation they are
of larger size, and  are also fewer in  number, than they are higher up
in the epiphysis, not exceeding usually five or six, but becoming multi-
plied, by the giving off of branches, to as many  as fourteen or sixteen ;
others, however, enter the epiphysis  from the sides,  near the junction
of  the bone and cartilage.
  The  interior of  these canals is occupied with  blood-vessels and
  * Mikroskopische Untersuchungen, pp. 35.  115.
  f Allgemeine Anatomic, p. 104.                J Ibid. pp. 240. 252.
  5  Miiller, Archie. 1841, p. 210.                1| Anal. Gin. t. vii. p. 409. 
BONE.
331
with  granular  nucleated cells,  precisely like  those  existing in the
medullary cells of bone.  (See Plate XXXV. fig. 3.)
   The cartilage cells in a transverse section of the canals immediately
surrounding their orifices are disposed in a rayed manner.
   Having  thus  described the structure, contents, and distribution of
these canals, we will  next inquire  their use.  (See Plate XXXV.
fig. 3.)
   If a number  of transverse sections be made, not merely of the
cartilaginous epiphysis, but also of the  bone in connexion  with it,
and if these be examined in the order of their removal, it will be
observed, first, that in those sections which are made from the cartil-
aginous  epiphysis most removed from  the  bone,  the  apertures  of
these canals are  small and numerous (see Plate XXXV. fig. 1);
second, that in the sections taken from the proximal end  of the epiph-
ysis the canals are fewer in number and their orifices larger (see
Plate XXXV.); thirdly, that in other slices, which include a portion
of both  cartilage  and  bone, the  latter  always  commences  on the
circumference  of the  section,  proceeding  gradually  inwards, the
portion of cartilage surrounding the canals in question being  the last
to  become  ossified   (see  Plate XXXV. figs.  2,  3);  fourthly, in
cuttings made below the cartilage and through the bone, spaces four
or five in number, filled with granular cells corresponding in situation
with  the afore-described canals, will be observed; fifthly, in others
carried still  deeper into the bone, these several  apertures will  have
coalesced into one large space—the rudimentary  medullary cavity.
   From  these several particulars, I therefore  infer that the canals in
question are intimately connected with the formation of the medullary
cavity; and that the absorption  of the cancelli situated between each
of them is brought about by the vessels contained within them, aided
also probably by the granular cells.
   Were  the  canals merely destined to  convey  to the  cartilage the
nourishment necessary for its transformation into  bone, it might be
expected that they would serve as so many centres from which the
ossification would  proceed; we have seen, however, that  the cartilage
in their immediate vicinity is the last to  be removed,  and its place
supplied  by bony cancelli.
  Medullary Cells.—The  primary cancelli  are  small,  studded  with
granules, form closed cavities, and do not contain bone cells.  (See
Plate XXXIV. figs. 2, 3.)  The secondary and larger cancelli are
formed  by the  absorption  of  the numerous  septa  of  the  primary 
332                      THE  SOLIDS.
cancelli; they do not form closed cavities,  but communicate freely
together, and contain bone cells  imbedded  in  their parietes.  (See
Plate XXXIV. fig. 4.)*
  Haversian Canals.—The Haversian canals are generally described
as being formed by the filling up of certain of the medullary  cells, in
consequence  of the successive deposition of new laminae of bony
matter.   It seems to me, however, to be very  questionable whether
they are formed in the manner indicated, and if so, such is assuredly
not the  general mode of their formation.
  I am  induced to take a  different view of their formation, and con-
sider they originate as follows:
  The surface of all bones, whether long, flat, or irregular, is observed
to be marked with  numerous grooves  of different sizes and depths.
In the  recent state, these are occupied  with blood-vessels, and it is
around  them  that  successive layers of bone are deposited, until at
length  the vessels  become entirely included, and a perfect  canal is
formed.
  In transverse sections of long bones, grooves and partially developed
canals may generally be seen along the outer margin of the  cutting.
  This  view  of the formation  of  the Haversian canals also  accords
well with other characters presented by transverse sections of bone.
Thus, in all such, it will be seen that the smallest Haversian canals
are situated  in the external part, while the larger canals  are placed
internal to these: it will also be observed, that the smaller canals are
surrounded by the  fewest number of concentric lamellae, and  the
larger by the greatest number.   (See Plate XXXII. fig. 1.)   Now, the
fact of an additional number of lamellae  encircling the larger canals
proves two things: first,  that these large Haversian channels are of
older formation than the small; and second, that  each lamella grows
or expands after its deposition, whereby the calibre  of such canals
becomes increased,  which is contrary to the  generally  entertained
notion of the formation of the Haversian canals, viz: by the filling up
of the large  cancelli, brought  about by  the continual deposition of
new osseous lamellae, the outermost of  which, for  such  a result to
ensue, must remain stationary in  point  of size.
                         «
                       ACCIDENTAL OSSIFICATION.
   The abnormal growth and development of bone is a very common
pathological occurrence.   Thus, we have it occurring on the surface
                   * See No. x. Med. Chir. R. p. 528. 
BONE.
333
of the bones themselves in the form of exostoses, in the permanent
cartilages, in the cellular tissue of muscles, glands, the ovaries, mem-
branes,  as  the  coats  of the arteries, and probably occasionally also
in that of every other tissue and organ of the body.
  It is  not,  however, every ossific deposit  which presents all  the
characters  of bone:  thus, those  contained  in  the  ovaries, in  the
mesenteric glands, and in the  coats of the arteries, usually want the
more  conspicuous  elements  of bone, the bone cells and  lamellae,
although these have been met  with in ossific  depositions remote from
all connexion with bone.
  In the reparation of fractures, we have a development of true bone
preceded by the formation  of cartilage. 
334
THE  SOLIDS.
                                 BONE.
   [Longitudinal and transverse sections of bone, to display the true struct-
ure, require so much time  and trouble in the preparation, that when it is
possible to purchase them, this course will be  found to be more advisable.
For those who desire to make their own preparations, the following  instruc-
tions are added:
   A section, either longitudinal or transverse, having been made as thin  as
possible with a fine saw, it must be reduced still farther by  a flat file.
   When this process cannot be farther carried on, the section is to be placed
between two hones, and being  kept moistened with water, the  honing is to
be pursued until the section becomes sufficiently thin to show the structure.
This point should be ascertained by occasional observations with a low power
of the microscope.   When sufficiently reduced, the section may be polished
by  carefully rubbing it on a strip of chamois-leather with putty-powder.
  If it be very thin, it should be mounted dry;  in this condition, a good pol-
ish will much increase  its value; but if the section be not very thin, it
should be made  more  transparent by being  mounted  in balsam;  in this
method, no polish will be necessary.
  Mr. Quekett  has observed that in some instances  when the bone was
deposited  in balsam, and heat then applied until the  balsam has boiled, the
structure  of the bone has been  beautifully displayed.
  Sections of bone, before being mounted, should be cleansed  from  grease
and dirt by being soaked for some hours  in sulphuric ether.

  "The vessels of bone may be recognised while it is yet fresh by the colour of the
blood contained in them, but they are rendered much more conspicuous by injecting
a limb with size and vermilion, depriving the bones of their earth by means of an
acid; then  drying  and putting them into oil of turpentine, by which process, the
osseous tissue is rendered transparent, while the injected matter in the vessels retains
its red colour and opacity."*

  As already stated in the text,  the lamellae are easily separated by macera-
tion in dilute hydro-chloric acid.]
* "Quain's Anatomy," by Sharpey and Quain, 5th ed. 
TEETH.
335
                  ART.  XVI. — TO  TEETn.

   The  tissue of the  teeth is to be regarded rather as a modification
of the osseous, than as a distinct type of structure: the truth of this
remark is especially apparent on an examination of two of the three
substances which enter into the formation of each tooth,  viz: the
cementum and dentine; the third constituent, the enamel, is more
nearly related in its organization to  the epithelium, of which indeed
it is a condition.
   Each tooth consists of two parts:  the body or crown, and the root
or fang;  the  limits of these are indicated by a  slight  contraction
called the neck; the crown is  either  simple or divided*, and the same
is the case with root also: those teeth which have a simple crown are
called incisors and canines, those with a double crown bicuspids, and
those with  the  crown quadruply  divided  molars.  Again, the  sub-
stance  of each tooth is  divisible into three portions, each of which
presents characteristic differences; these have received the names of
dentine, cementum, and enamel.
   The dentine, also called the ivory, forms the chief bulk of the tooth,
occupies a central position, and its interior contains the pulp cavity.
   The enamel forms a layer of compact substance, which immediately
surrounds that portion  of the  dentine  of  which  the crown of the
tooth is made up.
   The  cementum, also  called  crusta petrosa, has a  distribution the
very reverse of the enamel, and  extends principally around the fangs
of the teeth, and  terminates at the  neck  of the  tooth, in fact, just
where the enamel commences.

                      STRUCTURE OF THE TEETH.
  Having thus sketched the general position of the three constituents
of the teeth, the consideration of the intimate structure of each may
next be entered upon.
  Dentine.—The dentine is constituted of numerous tubes imbedded
in an inter-tubular substance; these tubes commence at the pulp
cavity, on the surface of which they open, and  from which  they
proceed  in  a radiate manner,  terminating  on the borders of the
dentine; those arising from the upper part of this cavity ascend almost
vertically, those from the sides more obliquely, and those from the lower
portion  pass either horizontally outwards, or else descend somewhat. 
336
THE  SOLIDS.
   These  tubes  diminish in size  from their commencement to their
 termination: they are branched;  at first they divide in a dichotomous
 manner;  their  subsequent ramifications are numerous, minute and
 arborescent, and they inosculate freely with  the  similar branches
 proceeding  from the  adjacent tubes:  those  tubes which proceed
 towards the cementum are remarkable for  the very great number of
 branches  into which they divide.
   The tubes of  the dentine in their passage outwards do not run in
 straight lines, but describe  in their transit two or three large curves,
 and each of these primary curves, when examined with a  higher
 power of  the microscope, will be observed to be made up of numerous
 smaller and secondary curves;  both  the large and  small  curvatures
 of one tube correspond with those of another.
   Such is the usual course and distribution of the tubes of the dentine:
 several modifications of them, however, still remain to be noticed.
   Thus, sometimes  a tube in  its passage will dilate into a bone cell,
 and again proceed onwards to its destination as a tube;  at others, a
 number of them, even in the centre of the dentine, will break up and
 form a  cluster of bone cells;  again, at others, the  tubes  frequently
 become transformed  into, or terminate on the margin of the dentine
 in bone cells.  This gradual transformation of the dentinal tubes into
 bone corpuscles, and their termination in the same, is especially seen
 in that portion of the dentine contiguous to the cementum.
  The usual method of termination  of the dentinal tubes, is in fine
 and inosculating branches on the surface of the dentine.  Sometimes,
 however, the tubes anastomose in a peculiar manner, and form distinct
 loops; at others, the terminal branches pass out of  the dentinal sub-
 stance, and  extend either  into the cementum or the enamel; this
 extension  into the former is a very frequent occurrence.
  For  illustrations of these several modifications,  the  majority of
 which have been pointed out by Mr. Tomes, in his excellent lectures,*
 sqe the figures.
  The surface of the  dentine presents many elevations and depres-
sions : to these the enamel is accurately adapted; it also exhibits the
 hexagonal impressions of the enamel fibres.
  The substance of the dentine is seen  also occasionally to be trav-
ersed with canals for  blood-vessels, analogous to the Haversian canals
of bone.
* See "Lectures" in Medical Gazette. 
TEETH.
337
   The pulp  cavity of the teeth of old persons frequently becomes
filled up, and even obliterated, by a secondary formation of dentinal
substance, and which may  be called the secondary dentine.  This
dentine results from the ossification of the pulp by the vessels of which
it is traversed, and from  the margins of the canals containing which
the dentinal  tubes proceed  in a radiate  manner.   (See the figures.)
   Mr. Nasmyth regarded this  secondary dentinal formation  as dis-
tinct from the other  structures of the tooth,  and  called  it  the fourth
dentinal  constituent.
   The dentinal tubes form but one  element of the  dentine; the other
is the inter-tubular substance.
   This is described by Mr. Nasmyth as constituted of elongated cells,
in the form of bricks placed end to end, and a tier of which exists
between every two tubes: Henle, on the other hand, declares it to be
fibrous.   It would appear not to present any regular tissue, but to be
simply granular.
   Occasionally, I have  encountered in  it globules of various sizes
refracting the light strongly, and presenting the appearances of oil or
fat vesicles.   It  has  occurred  to  me  that  these  might be fat cells
which had become included in consequence of  the ossification of the
pulp, and  which always contains  a greater or less quantity of fat
cells.  (See figure.)
   Some  sections  of dentine which I have examined have exhibited
numerous  reticulated markings, the results of  fracture of  the inter-
tubular tissue,  and occasioned  probably by  the  preparation of  the
section.   Fracture of the dentine is capable of reunion.
   Cementum.—Of the cementum it will not be  necessary to say very
much, it  possessing the  structure of bone, and  containing both bone
cells and Haversian canals; the latter, however,  but seldom.  (See
the figures.)
   The quantity of cementum differs in different teeth;  in many cases
it is very inconsiderable,  but it usually increases with age.
   In  those cases  in  which there  is but  a slight  development  of
cementum, a layer of considerable thickness, formed of numerous more
or less hexagonal cells, and extending over the whole of that portion of
the dentine not covered by enamel, may, in most  cases, be clearly seen.
   This layer, Mr. Tomes speaks  of as a granular layer;  it is, however,
distinctly and regularly cellular.  It is  not  easy to decide whether it
should be regarded as a distinct and permanent structure of the tooth, or
                             22 
338
THE  SOLIDS.
whether it merely forms the basement substance in which the cementum
is developed; my own impressions incline to the former view.*
  A layer of granules,  having the aspect  of imperfectly developed
bone cells, is  usually situated apparently between  the  dentine and
cementum, but really in the substance of one or other of these; this
layer might well be called the granular layer, and to it the description
of Mr.  Tomes seems more applicable.
  Mr.  Nasmythf describes the cementum as passing over the entire
surface of the enamel of  the tooth; this would appear, so far as the
human  tooth is concerned, to be an error.   A  cellular lamina, how-
ever, does really invest the enamel in very young teeth, but this  is
soon worn away: this layer,  however, has nothing to  do with the
cementum, but is  considered by Mr. Tomes to  be derived from the
inner surface of the membrane of  the tooth sac.  It may be  seen  in
the teeth of the calf and horse.
  Cementum is rarely, if ever, developed in the  pulp cavity, although
it has been stated to be so by many  observers.  The cementum is not
unfrequently traversed by tubes, similar to and derived from those  of
the dentine.
  It will now be  very  evident  that dentine and cementum  do not
differ essentially from each other, and that both  are but modifications
of ordinary bone.
  Enamel.—Examined with an object-glass of  one-fourth of an inch
focus, the enamel exhibits a fibrous  appearance.
  The fibres radiate outwards from the surface  of the dentine, some-
what in the same  manner as do the dentinal tubes themselves; they
are simple, short, somewhat attenuated towards either end, and pass
towards the margin of the  enamel in  a  waved manner,  sometimes
decussating, forming plaits or folds, and this occurs especially  when
the surface of the dentine is concave.  Viewed with a glass  of the
eighth  of an inch focus, they present the appearance of elongated and
many-sided crystals, and  in transverse sections they are seen to  be
hexagonal or polygonal; in  some instances, however, and especially
  * The  following is  Mr. Tomes's description of this layer: " In the inter-tubular
tissue, hemispherical or elliptical cells are  found, especially near the surface of the
dentine  of the fang, where they form a layer joining the  cement.  This, in a paper
read before tbe Royal Society, I described as the granular layer; on the coronal sur-
face of the dentine they are not numerous.  With these cells the dentinal tubes com-
municate, as do others coming from the cemental cells."
  f Memoir read before the Medico-Cbirurgical Society, by Alexander Nasmyth, Jan.
22d, 1839. 
TEETH.                         339
 in  the  enamel fibres of young teeth, a minute canal may be traced
 running along each fibre.  (See the figures.)
   It is  uncertain whether each fibre is constituted of a single cell, or
 whether several unite to form  it:  the  appearance,  in some cases, of
 faint transverse markings would  render it probable that the latter
 opinion is the correct one.
   Near the surface of the dentine, linear interspaces may sometimes
 be  noticed between the enamel fibres;  with  these spaces the tubuli
 of  the  dentine frequently communicate, and when they exist in any
 number, or extend nearly through its  entire thickness, they produce
 a pearly appearance of the enamel, and render it brittle.
   Thin longitudinal sections of the enamel,  in  connexion with the
 dentine, generally  exhibit numerous  linear fractures, which extend
 through its entire thickness, and which most probably arise  from
 their mode of preparation.  Sections  of enamel  also usually present
 numerous  wavy lines, and which are occasioned by the instrument
 employed in making the cuttings.

                       Structure of the Pulp.
   The  centre of the dentine  of all teeth is hollowed out  into a cavity;
 this is  occupied with a soft and reddish mass, easily separable  from
 the walls of the  cavity, the pulp.
  The  pulp is made up of numerous blood-vessels, the walls of which
 are constituted of delicate and nucleated cells, of nerves, or ganglionic
 cells, and larger  granular cells placed principally on the surface of the
 pulp, external to the other structures which  enter into its formation.
  These external  granular cells are supposed to play  an important
 part in  the development of the dentine, and  to which more particular
 reference will be made hereafter.
  The pain experienced in tooth-ache arises  from  inflammation of the
 nerves of the pulp, and which is frequently left  exposed to the contact
 of the air in consequence of the removal of  the dentine, by which in
 sound teeth it is  enclosed, as  the result of caries.

                     DEVELOPMENT OF THE TEETH.
  The  subject of  the  development  of the teeth  may be  considered
under two heads: under the first, the general development of the teeth
will be  briefly noticed; and  under the second, the special develop-
ment of their several constituents will be treated of.
  Into  the various  particulars  in reference  to the general develop- 
340
THE  S O L I D ii .
ment of the teeth as organs, it would be inconsistent with the design
of this  work to enter at any length.   It will be  sufficient to observe,
that preparations are made  for the formation of the  milk teeth at a
very early period of intra-uterine life ;  that the first trace of the future
tooth is manifest in the form of a papilla placed in the primary dental
groove, and consisting of granular and  nucleated cells; that around
this papilla a membrane is developed, with an open mouth, thus form-
ing  a follicle;  from the  margins of  this aperture  processes  of the
mucous membrane, of which the follicle is constituted, are developed,
and  these uniting with each other close  the opening, and convert the
follicle into a sac.   With the closure of the mouth of the follicle, the
first or  follicular stage of  the development of the teeth is terminated,
and  the second or  saccular stage commences.   The number of oper-
cula developed from the margins of the  follicles is determinate, being
two  for the incisives, three  for the canines, and four or five for the
molars.   In the second or saccular stage, the papilla takes  the form
of the tooth, of which it is the representative, the base dividing in the
case of the molars into fangs, and its apex assuming the  shape of the
crown of the  tooth, in the place of which it stands:  in this stage also
a blastemic matter, consisting of plasma and nucleated cells,  is devel-
oped in the space  intervening between  the  papilla  and the  sac, and
adherent to the inner surface of the membrane of the latter, by which,
indeed,  it is generated; lastly, the papillae become capped  with tooth
substance or dentine.
   With the passage of the teeth through the gums the saccular stage
terminates, and the third or eruptive  stage is entered upon.
   The second or permanent teeth pass through  stages precisely sim-
ilar to those of the first or milk teeth, the papillae  and follicles  being
developed in crescent-shaped depressions placed in the posterior walls
of the follicles of the milk  teeth,  and which  together constitute  the
secondary dentinal groove.*
   Having now obtained  a  general idea of the development  of the
  * For further particulars relating to the general development of the teeth, consult
the admirable paper of Mr. Goodsir, contained in the Edinburgh Medical and Sur-
gical Journal.  From the researches of that gentleman we learn that the papilla of
the teeth appear in the upper jaw before the lower; that those of the milk teeth are
developed in three distinct divisions—a molar, a canine, and an incisor; that the molar
is the first formed, the canine the second, and the incisor the third; also, that the first
molar is developed before the second, and the first incisor before the  second.  In the
permanent teeth the papillae, with the exception of the anterior molar, appear at the
mesial fine first, and proceed backwards. 
TEETH.
341
 teeth, we shall be prepared to understand the mode of development of
 the  individual tissues of the teeth, a subject which has been  studied
 more particularly by Mr. Nasmyth, Professor Owen, and Mr. Tomes.
   Formation of the Dentine.—It would appear to be a universal law
 of development, that all animal and vegetable tissues should take their
 origin in cells; of this law  the teeth present a striking and beautiful
 example.
   Thus, the dentine is formed out of the cells placed on the formative
 surface of the papilla or dentine pulp.   This view of the formation of
 the dentine originated  with  Mr. Nasmyth,* and its accuracy has been
 confirmed by the investigations of subsequent writers, and especially
 by those of Professor Owen and Mr. Tomes.
   Mr.  Owen, in his  work, "Odontography,"  describes with great
 minuteness the several steps of the conversion of the cells of the pulp
 into dentine, and also  enters upon the consideration of the develop-
 ment of the other tissues of the teeth.
   According to Mr. Owen,  the cells of the pulp, which are larger and
 more numerous on  the surface, become arranged in lines which are
 placed vertical to that surface; subsequent to  this arrangement, the
 nuclei are seen to divide, first  longitudinally into  two  portions, each
 of which  becomes a perfect cell,  also provided  with a nucleus; these
 again divide, but in a contrary direction, viz: transversely; thus, four
 secondary cells are formed within the cavity of  the primary cell, and
 out  of its single nucleus.   The  number is not, however,  limited to
 four, but each nucleus  may give origin to many secondary cells.  The
 primary cells  are placed end to end, as are also the  secondary cells;
 these last elongate considerably,  until  at  length  they coalesce, thus
 forming the tubes of the dentine;  the primary cells remaining as such,
 and  in some  adult human teeth being faintly visible.  The primary
 and  secondary cells, however, although placed end to end,  do not
 form straight lines, but describe greater and lesser curves, the greater
 being formed by the primary cells, and the lesser by the secondary;
 these are  the curvatures to which reference has  been made in the
 description of the tubes of the dentine.
  The views of Mr. Tomes, f although not essentially at variance with
those of Professor Owen, yet differ from them in some important par-
ticulars.  Mr. Tomes describes the primary cells themselves as dividing
  * " Memoir on the Development and Organization of the Dental Tissues," by Alex-
ander Nasmyth, August, 1836.
  f Medical Gazette, Lecture V. 
342
THE  SOLIDS.
longitudinally into two or more secondary cells, but not transversely;
subsequent to  this division, each  cell elongates,  and at length unites
with those above and below it; thus forming the dentinal tubes.  Some-
times two cells unite with but a single cell placed beneath it, and it is
in this way that  the  branches  of the dentinal tubes are produced,
Thus, according to Mr. Tomes, the wall of the primary cell, as well
as its nucleus,  enters into the formation  of the  dentinal tubuli; while,
according to Professor Owen, the nuclei alone give rise to these tubes,
the walls of the parent cells not undergoing elongation, but remaining
to constitute a considerable portion of the  inter-tubular tissue.
   In the human tooth I have been unable  to detect  the existence of
the primary cells  of the dentine.
   Covering the dentine pulp,  a thin transparent membrane exists;
this,  on its outer surface, is marked with numerous hexagonal depres-
sions, into which the enamel fibres are received.
   Formation of the Enamel.—Reference has been made to a blastemic
matter, consisting of nucleated cells imbedded in a granular  matrix,
and situated between the dentine pulp  and the inner surface of the
sac of the tooth;  this is the enamel pulp.
   The cells of which this is formed are larger than those of the den-
tinal pulp, more  transparent, and  with nuclei which  are less distinct;
they adhere to the inner surface of this sac, which is formed of a pro-
cess  of the mucous membrane of the mouth  itself, and from which,
indeed, they are evolved.
   This membrane, like all mucous membranes, consists of two layers,
an outer basement of fibrous and vascular layer, and an inner  colour-
less and blastemic layer; and it is from this last that the enamel cells
proceed.  It is marked with depressions similar  to those  existing on
the surface of the membrane of the dentinal pulp, and into which the
terminations of the fibres of the enamel are received.
   It  is out of the cells just described that the enamel fibres are formed,
and this in a manner almost similar to that in which the tubes of the
dentine are themselves developed; thus the cells  are first arranged in
vertical lines;  these  commence in the depressions on the inner sur-
face  of the tooth sac, and proceed from  without inwards.   The cells
next elongate  until they touch  each  other by either  short or  oblique
surfaces;  some of them coalesce by  their  extremities, and thus form
fibres in which earthy matter is deposited, and which at length ter-
minate in the hexagonal depressions  situated on the outer surface of
the membrane of the pulp of the dentine. 
TEETH.
343
   The nuclei elongate with the cells, and either disappear altogether,
or else remain as minute cavities running down the centre.
   At first the union between the fibres is but slight, so that in newly-
formed  enamel they may be easily separated from each other when
placed in water, to which they will impart a whitish  appearance, in
consequence of their separation  and diffusion through  the fluid.
   According to Mr. Tomes, also, numerous spaces exist between the
fibres in newly-formed  enamel; and it  is owing  to the presence of
these that young  enamel owes its opacity and brittleness.
   We thus perceive  that the enamel is to be regarded  rather as a
modification of the epithelium than  of bone.
   The development of both dentine and enamel may be well studied
upon the teeth of young pigs, or kittens, at  the birth.
   Formation of Cementum.—The  cementum pulp is formed between
the external surface of  the dentine  and the internal of the sac  of the
tooth, it being intimately united to both.
   It consists, like the pulps of the other tissues of  the teeth, of nucle-
ated cells imbedded in  agranular  matrix:  these  cells are described
by Mr. Tomes* as resembling those of temporary cartilage, being oval
in shape, and having their long axes placed transversely, and at right
angles, to the length of the tooth.
   The cells nearest the  surface of the dentine are  the first  to become
ossified; and when their  ossification  and development is completed,
they form the stellate or bone cells of the cementum.   Some consider
that the  nuclei of these cells alone give  origin to the  bone cells, and
appearances may be observed, even in adult  cementum, which are
favourable  to this opinion.
   The cementum is often seen to be traversed by  fibres derived from
the outer layer of the membrane of the tooth-sac,  as well as by tubes
prolonged into it from the dentine.
   Notice has  already been  taken  of the small hexagonal cells con-
tained in the cementum,  and situated principally upon the outer surface
of the dentine, and a doubt was  expressed  whether these were to be
regarded as forming  a  part of the structure of  the  cementum,  or
whether  they constituted a distinct organization.
   The cementum is particularly liable to an increased and abnormal
development constituting exostosis.
   It would  thus  appear, on the one hand, that the cementum and
dentine  are but modifications of  each  other, and also of one  and the
                         * See Lecture V. 
344
THE  SOLIDS.
 same tissue, the osseous; while, on the other, it is  evident  that the
 enamel is a modification of the epithelium.
   Mr. Nasmyth describes the cementum as  passing over the crown
 of the tooth and surface of the enamel, in  a thin layer composed of
 hexagonal cells and fibres; this layer  exists only on the surface of
 the enamel of the young teeth  of the  human subject, and it is not
 composed of dentine, but consists of either a few of the unelongated
 cells  of the enamel pulp, or, as Mr.  Tomes  considers,  of the inner
 surface of the sac of the tooth.

                  Nature of Caries of the Teeth.
   Various opinions have been entertained in reference to the nature
 of the peculiar decay  denominated caries,  to which the teeth are
 so liable.  Some  have  supposed that it is  a vital process resulting
 from  inflammation.   The fact that dead  teeth, that  is,  teeth which
 have  been removed from the jaw and are again employed as artificial
 teeth, undergo a similar decay to  that which  affects the living teeth,
 proves that it is not essentially a vital  action, although  it cannot be
 questioned but that the condition of vitality and the state of develop-
 ment of the teeth must exert a powerful influence over the progress
 of the decay.   Other observers regard  the decay of  the teeth  as a
 purely chemical phenomenon, the earthy matter of the teeth being
 removed by the action of free  acid in the saliva: this view of its
 nature certainly explains many of the circumstances connected with
 dental caries, and is supported  by the  fact already cited, viz:  that
 dead teeth are susceptible of the change.
   Two  facts, however,  require to  be determined before the chemical
 theory of  the decay of the  teeth  can  be  considered  to be proved;
 first, that the saliva is in every case of dental caries really acid;  and
 second, that the portion of  the  tooth which is subject to the carious
 action is really dead: upon both of these  points considerable doubts
 may be entertained.
   For myself, I have long entertained the idea that the real and proxi-
 mate cause of the decay of the teeth was to be found in the presence
 of some parasitical production, and that the condition of vitality of
 the teeth and of the states of the saliva were to be considered merely
 as predisposing causes to the affection.
   This idea  acquires  some confirmation from an  examination of  the
carious matter of a tooth; in it  vast quantities of minute threads or
filaments, possibly those of a fungus, are invariably to  be discerned, 
TEETH.                         345
as well as numberless  dark granules and irregular masses, bearing in
some cases the aspect of true cells.
   The question may be asked, are these threads, granules, and cell-
like  masses any thing more than the decomposing elements  of  the
dentine,  in  which  tissue  it is  that  the chief ravages of the decay
occur ?   The answer  is, possibly not; but the surprising numbers of
these filaments and the testimony of Mr. Tomes are opposed to  the
idea that they are the remains of the tubes of the dentine.   Mr. Tomes
thus writes in his tenth  Lecture in reference  to the tubes of  the
dentine:  " A transverse section  of carious dentine, rendered soft like
cartilage from the loss of its lime, presents a  cribriform appearance.
The tubuli seem enlarged and rather irregular, quite unlike the figure
they present in healthy dentine: this would  indicate that the solvent
enters and acts upon the parietes  of the tubes previous to affecting
the inter-tubular  tissue, and that the parietes of the tubes are there-
fore the first to  disappear.  I feel quite certain  that in the cases I
have examined, and they are numerous, the  parietes of the tubuli, so
distinguishable in healthy dentine, have almost, if not wholly, disap-
peared with the removal of the  lime."

                 Nature of Tartar on the  Teeth.
   Tartar of the  teeth consists  of phosphate of lime mixed up with
the mucus of  the mouth and epithelial scales: it  contains also occa-
sionally animalcules and vegetable  growths, which find in the  animal
matter of the tartar a  convenient  nidus for their development.  The
accumulation of tartar around the necks of the teeth results from an
opposite  condition  of  the saliva  to  that to  which chemists ascribe
dental caries,  viz: an alkaline state of it.
                             TEETH.
  IThe substance of the teeth being harder than that of bone, thin sections,
which should be made in different directions, must be first cut by means of
a lapidary's wheel charged with emery or diamond-dust.   These  sections
are then farther reduced in the same manner as those of bone—first, by the
files, next by the hones,  and lastly polished.  Like bone, they  may be
either mounted in balsam or dry; the latter method is preferable when the
section is sufficiently thin to show well the  structure.] 
346
THE  SOLIDS.
        ART.  XVII.—CELLULAR  OR  FIBROUS  TISSUE.

   The  truth of the scientific dictum, that every living thing proceeds
from a germ or ovum, is now generally admitted, and so also it may
be said  that each portion of the fabric of such living entity takes its
origin in a  cell, the early and embryonic condition  of every  organ
and  structure  being reducible to that of a cell.
   It was not, however, this consideration  that induced the older
anatomists  to apply the term cellular  to  the  tissue about  to  be
described, they having but little knowledge  of the  structure of the
elementary cell, or of its universal presence.
   They were led to denominate  the  tissue, into the description  of
which we are about  to enter, cellular, in consequence of observing
the areolae or  spaces left between  the fibres of which it is composed,
and  which  they  erroneously considered  to  be cells.  The cellular
tissue, then,  though like all  other tissues, taking its  origin in cells,
inasmuch as in its fully developed state it  consists of fibres, would  be
more accurately  denominated  the fibrous tissue, as indeed  by  many
modern anatomists it really is: the term  cellular tissue is, however,
one of so ancient a  date, and one, moreover, in such general use, and
so well understood,  that it seems to be  scarcely advisable to abandon
the use  of it altogether.
  The cellular Or fibrous tissue, however, as  ordinarily encountered,
is constituted not of a single  description of fibre, but  consists of two
kinds intermingled  in different proportions,  and each of which  is
possessed of distinct characters and properties.
  The  most remarkable difference between the two descriptions  of
fibrous tissue is,  that the one is  white and inelastic, and  the  other
yellow and elastic:  each of these  will be described under  different
heads, and the former before  the latter.

            INELASTIC OR WHITE CELLULAR OR  FIBROUS TISSUE.

              Tendons, Ligaments,  Membranes, fyc.
  The inelastic fibrous tissue  is very generally distributed throughout
the body: it constitutes the principal portion of tendons,  ligaments,
and fasciae:  of the fibrous membranes, the dura mater, pericardium, 
              CELLULAR  OR FIBROUS  TISSUE.          347

 periosteum,  perichondrium,  tunica albuginea of  the  testicle,  and
 sclerotic coat of the eye; also, of  the serous, synovial and  mucous
 membranes, as well as of the skin, and it forms likewise the principal
 constituent of the loose cellular tissue which is so  abundantly devel-
 oped throughout every tissue  and  organ of the body, but which is
 invariably present in large quantities wherever motion is necessary,
 as in the axilla, between the  fasciculi of muscles, and in the course
 of the vessels.
   When endowed with a distinct form, as in the case of the tendons,
 it may be called morphous inelastic cellular tissue, and  when it has
 no  circumscribed shape, the term  amorphous may be applied to it:
 when constituting membrane,  it  exists in  the state  of condensed
 fibrous tissue ;  and when it merely  binds organs together, or allows of
 the motion of parts, it maybe called loose or reticular cellular tissue.
   There  is,  however,  a form  of  the inelastic fibrous tissue which
 requires not merely  a separate name, but  a distinct notice.   This
 form is met  with in the great omentum, and consists in the fact of
 spaces of  irregular size and form  being left between the fibres, and
 hence it may be termed areolar cellular tissue.  The best examples
 of it are met with in the omenta of children and lean persons, which
 contain but little fat.   (See Plate XL. fig. 4.)
   The inelastic cellular tissue is made up of innumerable unbranched
 threads or fibres of equal calibre, of great tenuity, which appear
 white to the  unassisted sight, but  of a yellow colour when viewed
 under the microscope, and which have a great disposition to assume
 a waved or zigzag arrangement, the folds formed being comparable
 to those in which a loose skein of silk is  often observed to fall. '  (See
 Plate XXXIX. fig. 6.)
  When dried, the inelastic  cellular tissue  assumes the transparent
 appearance and consistence  of horn; in water, the  fibres swell up
 somewhat, become opaque and white, but  still preserve their form:
 in acetic  acid, they swell up  greatly, become  indefinable,  soft and
 gelatinous: the addition of a mineral acid  will, however,  bring the
 fibres again into view.
  The remarkable effect of acetic acid on the inelastic fibrous tissue,
 has suggested the idea to Mr. Bowman that "it is rather a mass  with
longitudinal parallel streaks (many of which are creasings), and which
has a tendency to slit up almost  ad infinitum  in the  longitudinal
direction."
  There are  several  considerations which may be  urged in disproof 
348
THE  SOLIDS.
of this view; the first is, the mode of development belonging to this
tissue; the second, the fact that the  fibres  are  all of nearly an  equal
diameter; and  the third  is, that the tissue still retains  its fibrous
constitution even after the application of acetic acid.
  The  white fibrous tissue  is  employed wherever a  strong and
inelastic material occupying but little space is required.
  A degree of elasticity not unfrequently appears to belong to this
tissue; but this  is rather apparent than real, and depends upon the
extent of its admixture with  the next form  of fibrous  or  cellular
tissue to be described, viz: the elastic.   (Plate  XXXIX. fig. 7.)

                  ELASTIC  CELLULAR OR FD3ROUS TISSUE.
  The elastic cellular or  yellow  fibrous  tissue  is distinguished from
the inelastic form by its branched filaments, the diameter of which is
unequal, its elasticity,  its deeper colour, and the  absence  of any
appreciable effect on the addition of acetic acid.   (See Plate XL. fig. 1.)
  Like  the  inelastic  fibrous tissue,  it rarely occurs in an unmixed
form, being mostly intermingled with it in variable proportions: thus,
it is encountered in tendons, ligaments, and, indeed, in all forms and
conditions of the inelastic cellular tissue; it constitutes the principal
portion of the ligamenta sub-flava and nuchae, of the  transverse fascia
of the abdomen, of the  crico-thyroid and thyro-hyoid membranes, of
the chordae vocales, of the internal lateral ligament of the lower jaw,
of the stylo-hyoid ligaments, of the  middle coat of the arteries, and
of the membrane uniting the rings of the trachea and  its ramifications.
It is also met with  in  considerable quantities  beneath the mucous
membrane of the oesophagus, at  the base  of the  epiglottis, in main-
taining which in the erect position it is probably mainly instrumental,
in the lungs and in the integuments of the penis.
  The elastic cellular tissue presents some differences of  appearance
and structure, in certain of the situations in which it is encountered:
thus, in the tendons and in the  smaller blood-vessels  (Plate XL. figs.
1, 2, 3. 5) the fibres are very slender,  appear to be but little branched,
and  contain at intervals  nuclei in the same manner as do the  fibres
of unstriped muscles; in  the reticular cellular tissue again, they are
slender, unbranched, and without nuclei (see Plate XXXIX. fig. 7);
in the ligamenta flava and  nuchae, in the crico-thyroid and thyro-hyoid
membranes, the fibres are thick, much branched, curled, and  inter-
woven, but they do not present nuclei (see Plate XL. fig. 1);  in the
larger arteries, the fibres are slender, and are united together so as to 
             CELLULAR  OR riBROUS  TISSUE.          319

form areolae (see Plate XL. fig. 2), while in the smaller blood-vessels
they are distinctly nucleated, as already observed.
  There is little doubt but that the several forms of elastic tissue just
described do really represent different  stages and  states of the  same
structure;  and it will be observed, that some of them, and especially
that of the small blood-vessels, approach  very closely  in  structure
and appearance to that of unstriped muscular fibre: the fibres of the
former  differ,  however,  in  being sparingly branched, and  in  their
more slender diameter.
  It is not easy, without the addition  of reagents, to distinguish the
two forms of fibrous or cellular tissue from each other when mixed
together:  nevertheless, when the two  are  well  separated, the elastic
fibres may be frequently singled out from the inelastic, in consequence
of their presenting a darker and stronger  outline, as well as  of their
following a more curled and tortuous  course.  (See Plate XXXIX.
fig. 7.)  Acetic  acid  applied to a portion  of mixed cellular tissue,  at
once allows the elastic fibres to be clearly seen, rendering  the inelastic
fibres transparent, and almost invisible.
   There are several parts  of  the human  organization described by
modern minute anatomists and physiologists as being in part  com-
posed  of unstriped muscular fibre;  these are the skin, dartos, nipple,
clitoris, penis, the ducts of the  larger glands, as  the ductus communis
choledochus, the ureters, and vasa deferentia.  Now, I find  that all
these parts, which I have examined with care, owe their contractility,
and their power of erection, to the presence of the nucleated  form of
the elastic  tissue which has been described as existing in  tendons and
the smaller blood-vessels, and not to any form of muscular fibre; and
further, that in the  majority of them, and especially in the dartos,
penis, clitoris, and nipple, this elastic tissue is confined almost  entirely
to the blood-vessels, the  walls  of which it  constitutes: this fact may
be readily ascertained in the instance  of the dartos by taking a small
fragment of that membrane when in  a fresh condition, and having
spread it out on the  surface of a piece of  glass without  the  addition
of any  fluid, then submitting it to the  microscope, when  the number,
size, and course of the blood-vessels may be traced, and the disposition
of the intervening fibrous inelastic tissue  recognised: in the recent
state, however, the vessels are filled with blood, the presence of which
prevents the satisfactory detection  of the  elastic  constituent of the
blood-vessels:  if now, however, acetic acid be applied to the fragment
of membrane thus spread out, the inelastic fibrous tissue  will  become 
350
THE  SOLIDS.
 indistinct, the red  blood  corpuscles contained  in  the vessels will be
 dissolved,  and the tissue of the blood-vessels clearly brought  out.
 (Plate XLIII. fig. 3.)
   The extent of contraction of which the dartos is susceptible is very
 great, and the act of contraction  must of course exert a very powerful
 influence over  the circulation of the blood in its  vessels.   In the
 contracted state of this membrane, the slender fibres of the elastic
 tissue, as well as their nuclei, are frequently curled up in  a spiral
 manner, an arrangement by which any amount of shortening may be
 secured.
   The contraction of the tissue of the dartos, and indeed of all elastic
 tissue, is evidently not a  physical, but a vital act: this  is shown  by
 the  relaxation and contraction  which  it experiences  in sympathy
 with the condition  of the  vital powers, as well as with any causes, as
 heat and cold, which affect these powers.
   The corpora cavernosa penis and corpos  spongiosum  urethrae are
 almost entirely  composed  of blood-vessels, and  the peculiarity  of
 these parts consists in  the large size  of the  vessels,  and  in  their
 repeated inosculation.   (Plate XLIII. fig. 4.)
   In the lungs, the blood-vessels  are so  numerous, that they, in this
 case, also constitute the  principal portion of the  fabric of  these
 organs:—this  may be beautifully seen in  the lungs  of the lower
 reptiles, as the triton and frog.
   Henle has described a peculiar arrangement of the fibres of elastic
 tissue.  "I have already  said," he remarks, "that the  fibres of the
 cellular tissue are for the most part united into a number more or less
 considerable, and  thus form  flattened bands of different thickness.
 These bands unite in their turn to produce others larger, or even
 membranes, and thus, sometimes they apply themselves parallelly to
each other;  at  others, they  cross  each other  in the  most varied
directions.   When  the  cellular tissue fills the  interstices of organs
under  the  form  of a soft mass, easy to  displace, and extensible, the
bundles may be perceived without the least  preparation, seeing  that
they cross  and interlace in all directions, and that  even  to the naked
eye,  they represent, a net-work of delicate fibres.   The size of the
bundles,  which I call  primitive  bundles, or afte* their origin,  the
fibres of  the cells of cellular tissue vary from the 0 • 003 to the 0 ■ 006
of a line.  The majority of the primitive  bundles are deprived  of
special envelope: the fibres may easily be detached, the one from the
other, and separate, when one bends a bundle strongly.  But in many 
             CELLULAR  OR FIBROUS  TISSUE.          351

 situations  they are interlaced, and held together by filaments, which
 differ from the fibres of cellular tissue by their chemical and micro-
 scopical peculiarities, while in certain respects  they approach the
 fibres of elastic tissue; of which we shall give a description further on.
 They are almost still finer than the fibres of cellular tissue, quite flat
 and homogeneous, but with outlines much more obscure, and they are
 distinguished, above all, by the considerable folds, which they describe
 when they are in a state of separation.   In order  to recognise them,
 it is necessary to place the cellular tissue in contact with acetic acid:
 in this acid the bundles of cellular tissue  become  transparent, swell,
 and cease to appear fibrous, while the filaments which envelope them
 undergo no change.  In this manner it happens that a bundle, which
 appears to be composed of the  ordinary  interlaced fibres  of cellular
 tissue, comports itself after having been treated with acetic acid,  as a
 transparent cylinder divided by contractions often very regular, and
 which  one soon observes  to  be caused  by a filament which runs
 spirally around the bundle; or also by separated  rings placed at a
 greater or less distance from each other   I have rarely succeeded in
 reducing  the turns to a single  filament, and I am obliged  in conse-
 quence to leave undecided the question, whether it does not sometimes
 happen that many filaments are rolled spirally around a bundle.  The
 formations which I have described show themselves  in no part  in a
 more beautiful manner than  in the delicate and firm cellular tissue,
 which is  situated at the base of the- brain beneath  the  arachnoid,
 between the vascular trunks  and  the nerves, and which becomes
 distended into isolated filaments, on extension, as, for example, in  any
 part of the circle of Willis.   There I have never sought the spiral
 filaments  in  vain; nevertheless, analogous bundles, encircled with
 spirals, may be seen also upon other parts of the economy, in serous
 membranes, in the sub-cutaneous cellular tissue, in  the skin, and even
 in the tendons."*
   It appears  to me that Henle has  misunderstood the  structure,  and
 consequently the nature of the formations noticed by him: there  can
 be little doubt but that these, in place of being bundles  of filaments
composed of inelastic fibrous tissue  encircled with a spiral coil  of
elastic tissue, are in reality hollow cylinders, vessels in fact in progress
of formation, consisting  of, in the stage described by the German
physiologist, an inner transparent and apparently structureless tunic,
enclosed in a coil of elastic fibrous tissue.
                    * Anal. Gin. vol. L pp. 377, 378. 
352
THE  SOLIDS.
  The correctness of this view is established by the very convincing
fact, that the tubular formation in  the condition just described may
be traced up to the state of perfect blood-vessels, some of which may
also now and then be seen dividing into  branches, and containing,
moreover, blood corpuscles.  Several of the stages of the development
of these vessels are seen in Plate XL. fig. 3.

                   DEVELOPMENT OF  CELLULAR  TISSUE.
  Exact observations are still required on the subject of the develop-
ment of both the elastic and the inelastic forms  of the cellular or
fibrous tissue, and especially of that of the latter form.  Schwann and
all  other observers after  him have  described the  cellular tissue as
taking its origin in cells of an  elongated form, from  the extremities of
which fibres, mostly branched, proceed, the cells themselves ultimately
becoming absorbed: microscopists,  however, have not as yet attempted
to point out the differences which doubtless exist in the development
of the two forms of cellular tissue, but have  for the most part con-
tented themselves with the above general description.
  It appears to me that the observations already made on the devel-
opment of the cellular tissue apply only to the yellow or  elastic kind;
and to this conclusion I am led  by the fact  that observers describe
the  elongated nuclei as giving origin  to branched filaments;  and we
know that the fibres of the inerastic fibrous tissue are simple, and not
branched.
  According to my observations, both forms  of cellular tissue origin-
ate  in cells.
  The cells of the white fibrous tissue exist  first as rounded  nuclei,
around which the cell wall gradually makes its appearance, and these
cells when  fully formed are  large, granular,  elongated, fusiform, and
from each extremity at length proceeds a single unbranched  thread,
which gradually becomes extended into a filament  or fibre, which  is
produced by the growth and extension of the cell wall itself, and the
extremity of which unites for  the production  of an elongated  thread
with that proceeding from the other cells placed above and below it:
finally, the process terminates by the  absorption of  the nuclei.   (See
Plate XLIII. fig.  2.)
  The cells of the yellow fibrous tissue also  exist, at first as  nuclei,
then as fusiform cells, but differ from  those of the white fibrous tissue
in the  subsequent steps of their development,  in that the cells are dis-
posed in lines, each fibre being formed, as is the case with the unstriped 
          DEVELOPMENT  OF CELLULAR  TISSUE.      353

muscular fibre, by the union of the filaments, proceeding from each
series of linearly disposed cells, and in that the filaments  proceeding
from the cells are very frequently branched.   (See Plate XXXIX. figs
1,2.  Plate XL. figs. 3. 5.)
  The above-described mode of development may be followed out in
longitudinal and cross sections of tendon treated with acetic acid; also,
in the smaller vessels of the pia mater, and in those placed  in  the
mixed cellular tissue which separates the different striped muscular
fasciculi:  we  thus perceive, that in the case of the yellow fibrous
tissue, many nuclei are required to form a single filament; and further,
that there is a strong analogy in the mode of its development with
that of  muscular fibre, as also in the physical properties of the two
tissues.
  In the fibrillation of the fibrin of the blood we have an example of
the formation of filaments independently of any development from
cells, and  at one time I conceived that the fibres of "the white fibrous
tissue might possibly originate in a similar manner.
23 
354
THE  SOLIDS.
                   ART.  XVIII. —MUSCLE.

  Few of the animal  tissues  have been more extensively examined
than the muscular:  the multiplied observations made on its structure
have, however, led neither to that uniformity of opinion respecting it,
nor, indeed, to that accurate knowledge of its minute anatomy, which
might have been anticipated; of the truth of this position, evidence
will be shortly adduced.
  Muscles admit of division  into the voluntary, or those which  are
under the  control Of the will, and the involuntary, or those of which
the action takes place independently of the will;  the former consist
of the muscles of animal life—those, for example, of locomotion—and
the latter embrace those of organic life, as the muscles of the aliment-
ary canal  (the sphincters of the oesophagus and anus  excepted, which
are to a certain extent voluntary), the heart, the uterus, the bladder, &c.
  It  will  be  observed,  that  the involuntary  muscles, or those  of
organic life, usually encircle the hollow viscera; there are some other
situations,  however,  in which involuntary muscular fibres  are met
with, as in the trachea and  its  bronchial ramifications, the iris,  the
sarcolemma, and, according to some observers, as Bowman, they  are
also encountered in  the dartos and covering the  excretory ducts  of
the larger  glands, as the ductus  communis choledochus, the ureters,
and vasa deferentia; and it is with  them  a  matter of question how
far the contractility of the skin, and the erection of the penis, clitoris
and nipple, may be dependent upon the presence of involuntary mus-
cular fibrillae.   In the preceding article I have, however, shown that
the contractility of these parts depends upon the presence of a nucle-
ated form  of elastic tissue, allied to unstriped muscular fibre in  many
of its properties, but yet distinct  therefrom.
  Corresponding with the division of muscles into voluntary and invol-
untary, there exist differences of structure:  thus, the muscles under
the control of the will are all  striped, while those which are not under
its influence are unstriped.   To this  rule, however, one remarkable
exception  may be mentioned,  viz: the muscles of the heart, the action
of which is to a great extent involuntary, and which are yet striped:
this exception is rather apparent than  real, as will be seen hereafter. 
MUSCLE.
355
                         STRUCTURE  OF  MUSCLE.
   A striped muscle is made up of a number of unbranched fibres, each
 of which is included  in a distinct sheath, the sarcolemma, and consists
 of a number of threads or fibrillae:  the fibres again are collected into
 sets or bundles called lacerti; these are held together, and yet separ-
 ated by a mixed form of cellular tissue, which also contains fat vesicles,
 blood-vessels and nerves.
   An unstriped muscle consists of fibrillae, intermingled with  fibrous
 tissue:  these  do not  form  fibres, and  consequently there  is  no
 sarcolemma.
   Between striped and unstriped muscle there is no essential  or spe-
 cific  structural difference: the one is not to be regarded as typically
 distinct from the other, but both should rather be considered as differ-
 ent conditions in the development of one and the same tissue.   Of
 this position, evidence will be hereafter  adduced.
   According to the above view, muscular fibre presents two grand
 stages  of development;  the first  of which is represented  by the
 unstriped fibrilla, and the second by the striped muscular  fibre.
   We  shall first describe the  structure of the unstriped  muscular
 fibrilla, because it represents an earlier condition of development than
 the striped.
   Structure of Unstriped Muscular Fibrilla.—Unstriped muscles
 consist of fibrillae which are  unbranched, rather broad, somewhat flat,
 and which contain, imbedded in their substance, elongated and gran-
 ular nuclei.  (See Plate XLI. fig.  2.)
   The  fibrillae  usually run parallel  to each other, and form thin layers
 and fasciculi, which are separated  from  each other by  cellular  tissue,
 and frequently interlace.
   The  nuclei are sometimes imbedded in the substance of the fibrillae,
 without at the  same  time  increasing their  diameter:  at others, they
 render the fibrillae ventricose from their great size;  and again, in other
 cases, they protrude from their sides.   (See Plate XLI. fig. 2.)   They
 are best seen after the addition  of acetic acid.
   Unstriped muscles  are doubtless  freely supplied  with blood-vessels
and with nerves.
   The unstriped muscle is called into action with greater  difficulty
than the striped; its action is also slower, and of a  peculiar kind, giv-
ing rise to the vermicular and  peristaltic motion, seen especially in
the intestines. 
356
THE  SOLIDS
   This slower and less energetic action results from its lower degree
of organization.
   The muscular structure of the heart, the action of which is  to a
considerable extent involuntary, requires a special  description.   The
muscular tissue  of this organ has been usually supposed to constitute
an exception in  its structure to that of other involuntary muscles, and
that while it  performed the office of an involuntary muscle, it yet
possessed the  structure of a  voluntary muscle, its fibres being striped.
  Mr. Bowman, one of the  very best authorities on the structure of
the muscular  fibre, gives the following description of the tissue of the
heart: " 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."*
  This description is very imperfect,  and in some respects, according
to my observations, incorrect.   Thus, the muscular substance of the
heart does not form fibres at all, but consists simply of fibrillae, which
agree in every respect  with  those of other involuntary muscles, save
in their transverse striation: thus  they have  the same  considerable
diameter: they  are, in like  manner, abundantly nucleated (see Plate
XLI. fig. 3), and  they have the  same arrangement, interlacing with
each other, and not forming  fibres included in  a sarcolemma, as is the
case with the  voluntary muscular tissue.  The transverse striae, too,
have  not the deep and  permanent character belonging to  the fibrillae
of ordinary striped muscle, as is evinced by the fact that acetic  acid
effaces all vestige of striation.
  It thus appears that the  muscles of the  heart agree in  structure
much more closely with that of other involuntary  muscles, which  is
contrary to what is generally supposed, than they do with that of the
voluntary muscles.
  Thus,  then,  the  structure  and the function  of the  muscles of the
heart are in accordance, and  not in  antagonism, as  is usually con-
ceived, the single point of difference between its fibrillae and  those of
other involuntary muscles consisting in the feeble  transverse striation,
the presence of which  evinces a somewhat higher degree of develop-
ment, as well as a greater power of contractility.
                   * Physiological Anatomy, p. 161. 
MUSCLE.
357
   Structure of Striped Muscular Fibre.—The striped muscle consists
 of fibres:  each of these is included  in  a  distinct  envelope, termed
 Sarcolemma, and is made up of a number of lesser fibres or fibrillae.
 (See Plate XLII. fig.l.)
   The fibres vary very considerably in size, not merely in different
 animals, but also according to the age of an animal, and even in a
 single bundle  of the same animal, some of them being three or four
 times larger than others, and  the  smaller being usually adherent to
 the larger fibres;  a fact which has reference to the development of
 muscular tissue,  and which will be explained when  we arrive at  the
 consideration of that portion of our subject.  (See Plate XLII. fig. 4.)
 The  difference in the  size of the fibres  according to  age is very
 remarkable,  those of the foetus being several times smaller than the
 fibres of the adult.  (See Plate XLII. fig. 1, and Plate XLIII. fig. 1.)
   They differ also to a very considerable extent  in  form as well as
 magnitude:  thus, in a cross-section and in a recent state,  they  are
 seen  to be more  or less angular and compressed, but still preserving,
 in most cases, much of  the character of cylinders.   In the  dry con-
 dition, this angularity is greatly increased,  and  to  this state of  the
 fibres the  representations hitherto given chiefly refer.  (See Plate
 XLII. fig. 5.)
   The fibres, both great and small, are, as already observed, arranged
 in bundles or lacerti, of variable size; those of the same bundle run
 parallel to  each other, and the different bundles are separated, and  yet
 held together by  mixed fibrous tissue.
   Examined with a moderate power of the microscope, each fibre
 is seen to exhibit numerous  transverse  striae,  which are placed at
 tolerably regular distances from each other: some  fibres,  also,  and
 especially  such as have been  preserved  in spirit, present numerous
 fainter longitudinal striae.
  When viewed  with a somewhat higher object-glass, and when each
 fibre has been torn into pieces by needles, its entire bulk will be seen
 to be  made  up of a number of slender  threads  of equal diameter,
 which present a distinct transverse striation.
  It was formerly very generally supposed  that the transverse lines
on the striped muscular fibre  were produced by a filament which
wound spirally around  it: this notion is, doubtless, erroneous,  as
indeed it is now generally allowed to be.
  It has been observed,  that the fibrillae are themselves marked with
 transverse striae:  now, it is not difficult to convince one's self that the 
358                      THE  SOLIDS.
striation of the fibre is produced by the striae of the fibrillae, the striae
of one fibrilla corresponding with that of another, and  thus giving rise
to a line which extends entirely across the diameter of the fibre.
  The correctness of this explanation might  have been easily inferred
from a knowledge of the composition of the striated muscular fibre
of banded fibrillae, and from the  aspect of the  transverse  line itself,
which, when examined with a high power  of the microscope, does
not present the appearance of an uninterrupted and continuous line,
such as would be produced by the winding of a filament around it,
but rather of a line  formed by the apposition of a series  of dots or
shorter  lines;  in which manner, indeed, it is that the striation of the
fibre is really produced, as  we have seen.
  The  fibrillae contained  in  each fibre are unbranched, of great
tenuity, of nearly equal diameter  (see Plate XLII. fig. 1), and their
number varies greatly, amounting in the larger fibres to as many as
fifty or sixty, while in the  smaller they may not exceed from one to
five and upwards, according to the breadth of the filament.
  The striae present a very uniform and strongly marked  character:
the spaces between them are not, however,  equal: thus, they are
sometimes rather longer than the diameter of the fibrilla: at other
times, they are shorter, and when the striae are very close, the fibrilla
becomes ventricose or moniliform.
  Much difference of opinion prevails as to the nature of the striation
exhibited by the  fibrillae.   Drs. Sharpey* and Carpenterf incline to
the opinion that each fibrilla consists of a series of particles or cells
cohering in linear  series,  and that  the lines  indicate the point of
junction of these;  Mr. Erasmus WilsonJ  attributes a  still more
complicated structure to the  striated fibrilla.  He believes that two
kinds of cells exist in each  fibrilla; a pair of light cells, separated by
a delicate  line, being interposed between each pair of dark ones.
  Lastly,  Bowman  considers that the  lines  indicate  the divisions
between particles, which he denominates "sarcous elements."
  My own view of the nature of these lines differs  from that of all
the gentlemen named.  I  consider that the lines in question are
produced  by the  simple corrugation or wrinkling  of the  threads at
regular  distances: a view,  the accuracy of which  is all  but  proved
by a consideration of the development  of muscular fibre, and by the
               * Quain's Anatomy, 5th edition, vol. ii. p. 168.
               f Human Physiology, p. 176.
               I Manual of Anatomy, 3d edition, p. 16. 
MUSCLE.
359
 action  of acetic  acid on  the  fibrillae of the  heart, the transverse
 markings of which it entirely obliterates.
   The  fibrillae are, as already stated, included in a sheath, the sarco-
 lemma  of Bowman, both together constituting the fibre.   The sheath
 cannot  at all times be seen:  it may, however, frequently be so, and
 especially when the fibrillae have been torn across, the sheath at  the
 same time  not having been divided, its greater elasticity enabling it
 to  resist  the  force which was sufficient to rupture the muscular
 fibrillae.  It is in such cases that the  best view of this membrane is
 obtained.   (See Plate XLII. fig. 1.)
   Treated  with  acetic  acid, each  fibre discloses most  distinctly a
 considerable number  of elongated and granular nuclei,  the outlines
 of  which are in some cases visible, even without the application of
 the acid.   (See Plate  XLII. fig. 2.)
   Of these nuclei, Mr. Bowman remarks: "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 surface.   They are oval  and flat, and of so little
 substance, that  though many times larger than the sarcous elements,
 and lying among them, they do not interfere with their mutual apposi-
 tion and  union."   "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 depos-
 ited, since their absolute number is  far greater in the adult than in
 the foetus, while their  number relatively  to  the  bulk of  the fibre at
 these two epochs remains nearly the same."*
  The  above description  is in part only correct.  Thus I find, first,
 that the nuclei are invariably situated on the external surface of  the
 fibre, the majority within the sheath, and either adherent to this, or to
 the exterior fibrillae, some also being placed on the outer surface of
 the sarcolemma; facts which throw much light upon the development
 of the  muscular fibre; secondly, that the  nuclei  are not usually free
 nuclei, but are contained in most cases  in  filaments in  every way
 similar to  those of unstriped muscle, and with which they are identical.
  Were the nuclei really  scattered  throughout  the substance of a
 muscular  fibre, they would infallibly  destroy the  parallelism of  the
striae, and greatly interfere  with its contractile power.
  The  interpretation  to be given of the location of the  nuclei and
fibres of unstriped  muscle in the situations indicated, will be explained
              * Physiological Anatomy, vol. i. pp. 158,159. 
360
THE  SOLIDS.
 when the subject of the development of muscular fibre is considered ;
 at  the same time,  also, the  point raised by Mr. Bowman, as to the
 persistence of the nuclei, will be discussed.
   The fibres of the  upper part of the oesophagus are striped, while those
 of  the lower half are unstriped.  It has been considered a matter of
 uncertainty whether the two  pass by insensible gradations of structure
 into each other, or  whether they terminate abruptly.   I believe, after
 careful examination, that the latter supposition is the correct  one.
   With a few remarks  upon the peculiar views entertained  by Mr.
 Bowman, in reference to the structure of the striated muscular fibre,
 the  discussion of  the  structure of  muscle  may  be  brought to  a
 conclusion.
  "It was customary,"  writes Mr. Bowman,* "both before and since
 his time (the time of Fontana), as at the present day, to regard  the
 fibre as a bundle of smaller  ones,  whence the term primitive fasci-
 culus, first given to it by him, and adopted  by Miiller; 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 fibrillae;  but it is  by a fracture  alone that such fibrillae  are
 obtained.   They do not exist as such in the fibre.  And further, it
 occasionally happens that  no disposition whatever is  shown to  the
 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 cleavage, discs,
 and not fibrillae,  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 fibrillae: but, in
fact, it is neither the one nor  the other, but a mass in whose structure
 there is an intimation  of the existence  of both, and a tendency to
 cleave in the two directions.  If there was 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,  the  union of which  constitutes  the  mass  of the fibre.
 These elementary  particles  are  arranged and united together  in
two directions.   All the resulting discs, as well as fibrillae,  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
* Physiological Anatomy, vol. i. pp. 151,152. 
MUSCLE.
361
fibre is therefore uniform, and is equal to the diameter of any one of
its fibrillae, and is liable to the greatest variety."
  This view of the  structure of the  striated  muscular fibre is inge-
niously conceived and well expressed; nevertheless, it can be shown,
I think, notwithstanding its ingenuity, to be incorrect.
  There are two considerations which  appear to me to be sufficient
to disprove the view just propounded.  The  first is, that the rudi-
mentary muscular fibre  consists  of one  or more  threads  or fibrillae,
containing imbedded in them a number of elongated nuclei, which,
however, have  no correspondence with the transverse markings; and
the second is,  that, while any  muscular  fibre may  at  any time be
readily separated into its component fibrillae, the  simultaneous trans-
verse cleavage  spoken of and figured by Mr. Bowman is an occurrence
of extreme rarity, and one, moreover, of which I have never been able
to perceive the slightest trace in any  muscular fibre which has fallen
under my notice.
  It would thus appear that the older  view is the correct one, and
that the  striped muscular fibre is made up, as already described, of a
variable  number of fibrillae enclosed in a tubular sheath.*
  Blood Vessels of Muscles.—Muscles  are  copiously supplied with
blood-vessels;  the larger vessels are  contained in the cellular tissue
separating the fascicles or lacerti of the  muscles, and which serves to
support and to conduct them; the smaller vessels or capillaries are
not encircled by cellular tissue, but  penetrate between  the  fibres,
forming numerous capillary loops and meshes, having their long axes
disposed  in the direction of the  length of  the  fibres.  This arrange-
ment of the capillaries is shown in Plate  XLI. fig. 4.
  Much  of the colour  of a muscle arises from  the  blood enclosed in
the vessels, but  not all, a portion of it being contained in the muscular
fibres themselves.
  It is evident that the contraction  of the  fibres exercises  much
influence  upon the capillary circulation, reducing  the calibre  of the
capillaries  to such an  extent as that  the  blood-corpuscles can  pass
through them only in an elongated  form.
  In the  course of the  larger vessels, imbedded in  the inter-fascicular
cellular tissue,  fat corpuscles  are  often abundantly  distributed, as
represented in Plate XLI. fig. 1.
  Nerves of Muscles.—Muscles are  also  abundantly supplied with
nerves, principally those of  locomotion.  Burdach has figured and
                      * See  Appendix, page 548. 
362
THE  SOLIDS.
described the nerves in muscles as forming loops, which  either joni
other neighbouring loops or else return into themselves.   The figure
and  description  given by Burdach have been  adopted by almost all
succeeding anatomists; notwithstanding which, I would observe, that
I have never seen the nerves  terminating in muscle in the  manner
indicated;  not, however,  that I  doubt the fact of their doing so,
because such a mode of termination is common to nerves; but would
simply infer from this, that the loop-like arrangement is neither very
general nor very obvious.
  According, then, to  the latest physiologists, nerves, strictly speaking,
really  have no  termination whatever  in muscles:  an opinion, the
accuracy of which is  more than doubtful.
  I find  that the nerves, after branching in a dichotomous manner,
have a real termination, and that from  time  to  time certain tubules
leave the main  trunks, and end  in  the formation of elongated and
ganglioniform organs situated  between the fibres of  muscle.  (See
Plate XLI. fig. 4.)
                    UNION OF MUSCLE WITH TENDON.
  The unstriped muscular fibrilla is rarely, if ever, attached to tendon
or aponeurosis:  the striped fibre, on  the  contrary,  is almost con-
stantly so.
  Two errors have prevailed in reference to the union of the striated
muscular fibre with tendon.
  The first has reference to the form of the  extremity of  the fibre in
connexion with the tendon;  the second to the precise mode of junc-
tion between the  two.
  Thus,  most observers have described and  figured the fibre  as
terminating in a conical point, from  which the  fibres  of  the fibrous
tissue of the tendon proceed in a straight line.
  This description  is contrary to fact, both  as respects the form of
the fibre and its  mode of union with the  tendon:  muscular  fibre is
rarely, if ever, inserted vertically into a tendon or aponeurosis; but in
all the instances which have fallen under my observation, the insertion
has been either oblique or occasionally at right angles  with the tendon;
the extremity of the fibre being in the one case also oblique, and in
the  other truncate: this termination  is the very  opposite  of  that
usually attributed to it.  Let us next see in what way  the two struc-
tures are  united.  In no one  instance have I ever seen the fibres of
the  fibrous tissue of the tendon unite themselves  directly with  the
muscular fibre: on  the contrary, the mode of junction  has  always 
MUSCLE.
363
been  effected in the  following manner:—the sheath of each fibre is
prolonged upon the surface of the tendon where the union is oblique,
and certain of the fibres of the tendon are extended upon and inter-
lace  with  the  terminal portions of  the muscular fibres and their
investing sheaths.   (See Plate XLII. fig. 4.)

                        MUSCULAR CONTRACTION.
  Many attempts  have been made to determine the exact changes
which the muscular  fibre undergoes  in its passage to a state of con-
traction; these attempts do  not appear to me to be altogether satis-
factory and successful.
  The earliest  opinion formed, in reference to muscular contraction,
supposed that during contraction the fibres  and fibrillae of muscle  are
disposed in a zigzag manner, such a disposition of the fibres of course
having the effect of materially shortening the muscle.  (Plate XLIII.
fig- 5-)
  The advocates of  this view seem to have overlooked the fact that
fibres thus disposed, having  no fixed  or direct  points from which to
act, would have their power by such an arrangement rather diminished
than  increased: this idea has therefore been  justly discarded, and an
account of the  nature of muscular contraction, much more closely
approximating to the  truth, substituted in its place.
  Mr. Bowman, who  has written by far the best account of muscular
contraction which has yet  appeared, discriminates between passive
and active  contraction of muscle: the former he conceives to be a
uniform act, involving  and  affecting  equally the entire  mass of the
muscle: the latter, on the other hand,  he considers to be a partial act,
implicating, first, a particular part  or parts of a fibre; subsequently
leaving these, and  advancing to other and  neighbouring parts of  the
same  fibre.
  This view is founded principally  upon  the experiment detailed
below, made upon a fibre of the claw of a  crab, which still retained
its contractility.   "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 con-
tracted 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  transverse stripes.   These contractions pull 
364
THE  SOLIDS.
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 station-
ary, but oscillate from end to end, relinquishing 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 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.  At a subsequent stage, the ends
of the fibre commonly cease to be fixed, in consequence of the inter-
mediate portions, by their contraction, receiving some of  the pressure
of the glass.  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."*
  To this experiment, which I have never been  able successfully to
repeat, some exceptions  may be taken.   Thus, it is known that water
has a powerful and remarkable effect in exciting muscular fibre which
still retains  its  irritability to contraction, and the nodulated aspect of
the fibre mentioned, may have been due to the fact that the  fibre was
not entirely  immersed  in water  (the piece of mica being merely
moistened), but only touched by that fluid at certain intervals, which
most probably corresponded  with the bulgings of the fibre referred  to.
This  explanation  is supported by the effect of water on  recent mus-
cular fibre,  entirely immersed in that liquid.   Thus, on  the moment
of immersion,  the fibres contract greatly in length,  increase in a
corresponding  proportion in bulk, become irregularly  bulged and
nodulated:  the  transverse lines  on the fibres disappear,  the longitu-
dinal  lines  at the same  time becoming  more strongly marked than
usual.   (See Plate XLII. fig. 3.)  These several effects are due to
the extraordinary, unequal, and doubtless, also, abnormal contraction
induced by the stimulus of water.  Presuming, therefore, that in the
experiment  referred  to,  the  phenomena occur in the order described,
yet it would not be safe to adopt the conclusion, from this, that they
represent the several stages of the normal contraction of a  muscular
fibre. Again, it might be argued, that the nodular condition described
as belonging to a muscle in a state  of active contraction would  be
most^infavourable for the full  exercise of the power of  contraction,
                  * Physiological Anatomy, pp. 180,181. 
MUSCLE.
365
 seeing that the nodules of one fibre would necessarily interfere with
 those of the contiguous fibres, and  thus  impede its  own as well as
 their contraction.
   For the above reasons, therefore, I would  place but little reliance
 upon#ie experiment quoted, and prefer to adopt an explanation more
 simple in  its character,  and yet entirely sufficient to explain the
 condition of a muscle  during its state of most active  yet entirely
 normal contraction.
   I  conceive that no  distinct  line of demarcation exists whereby
 active and  passive  muscular contraction can  be discriminated: the
 two are but different degrees of the same power, and manifest  them-
 selves  by phenomena which differ not in kind, but simply in extent.
   If a muscle of the leg of a frog be isolated  from  its fellows, or if
 the tongue of the same animal be extended and pinned to the margins
 of an aperture  made in  a piece of cork, the only change which can be
 observed  to take place in the  muscular fibre, when stimulated to con-
 traction, consists in an approximation of its  striae, neither waves nor
 nodules manifesting themselves in its course.
   Again; immersion of muscular fibre, which has almost lost its con-
 tractile power in water, will be followed by an approximation of the
 striae, and a proportionate increase in the diameter of the filament.
   Now, the approximation of the striae is the  only visible  sign which I
 have ever been able to detect in natural muscular contraction; and it is
 amply sufficient to account for the shortening and increase in diameter
 which a muscle undergoes during its state of most active contraction.
   The distance between the striae in a fibre placed somewhat on the
 stretch, as are  all  muscular fibres in their natural state, and in that
 which  is  in a state of contraction, varies greatly, and is very evident,
 the striae  in the contracted  fibre being often one-third or even one-
 half closer together than they are in the fibre in its ordinary state
 of tension.  The approximation of the striae to the  extent just men-
 tioned, presuming the entire length of the fibres to be in a contracted
 condition, would reduce the length  of the muscle in the same pro-
 portion, viz:  to the extent of a third  or even  one-half.
  Muscular contraction, then, I would define to be a simple shorten-
ing of  the fibres of a muscle, accompanied  by an  increase in  their
breadth;  this shortening  in the striped muscular fibre being evinced
by an approximation of the transverse striae, as well as by an increase
in its diameter, while in  the unstriped fibre it is manifested solely by
an increase in the  thickness of the fibrillae.  (Plate XLII. fig. 3. a, b.) 
366
THE  SOLIDS.
   Whether, in muscular contraction, the whole length  of the  fibres
 of a muscle is engaged, or part only of their length, or whether, during
 the continuance of the contraction of a muscle, its fibres remain in a
 state of quiescence;  or  whether they undergo an alternate contrac-
 tion and relaxation, in obedience to the interrupted stimulus  derived
 through the medium of the nerves, it is not easy to determine with
 certainty;  nevertheless, it is most probable that where the contraction
 is very intense, and  long sustained, such  an alternation of condition
 does exist.
   The stiffening of the body, which occurs after death, known by the
 terms "rigor mortis," "cadaveric rigidity," is  due to  muscular con-
 traction.   This  rigidity  usually comes on a few hours after death;
 and after continuing for  a variable time, not exceeding  six or seven
 days, again disappears.   There is  much variety, however, in  the
 exact periods of the advent and departure of the rigidity: it has been
 observed to come on latest, attain its  greatest intensity, and to last
 longest  in the bodies of robust persons, who have  either  died of short
 and acute  diseases, or who have suffered a violent death.   On  the
 contrary, it has been remarked  to set in soonest, and  to  disappear
 earliest, in  persons of feeble constitution, and those who  have died of
 a lingering and exhausting malady.
  The  immediate cause of cadaveric  rigidity has never  yet  been
 satisfactorily explained.  Some have supposed  that it depends  upon
 the coagulation of the blood in the capillaries—an hypothesis scarcely
 tenable:  others,  with  more  reason,  conceive  that it proceeds  from
 the solidification of the fibrin of which  muscle is chiefly constituted—
 that it is, in fact, a phenomenon precisely analogous to the coagulation
 of the fibrin of the blood.
  An explanation differing  from both of the  former has suggested
 itself to my mind.  I conceive  that muscular contraction may possibly
be brought about by the stimulus of the thinner and more  watery
parts of the blood, &c,  acting on the  still irritable muscular fibre,
 and  which are known to escape from their containing vessels very
shortly after the extinction of  life.  Of this passage of fluid through
the walls of its receptacle, we have a familiar instance in the case of
the gall-bladder and its contents.
  Two  other points require to be briefly alluded to, in relation to the
subject  of  muscular  contraction: the  first is the muscular sound
heard on applying the ear to a muscle in action, and which has  been 
MUSCLE.
367
likened by Dr. Wollaston* to the distant rumbling of carriage-wheels;
the second relates to the fact  made  known by  MM. Bequerel and
Breschet, that a muscle during  contraction experiences an augment-
ation of the temperature.

                       DEVELOPMENT OF MUSCLE.
   The muscular tissue, like  the  majority of those which have hitherto
been described, takes its origin in cells.
   The term fibre is applicable only to the  striped form of muscle, in
which a number of fibrillae are included in an investing sheath common
to them; these striped fibrillae of the striped fibre of voluntary muscles,
are analogous to the  unstriped fibrillae of the involuntary muscles.
   The  process of the development of muscle may be divided into
three stages:
   In  the first, isolated cells, arranged in  linear series, unite to form
the unstriped fibrilla, the  nuclei  remaining.
   This stage appertains to all unstriped  muscular fibre.
   In the second, the  transverse  striae or markings  appear upon  the
fibrillae, the nuclei still remaining.
   This stage is permanently exemplified in the muscles of the  heart,
temporarily in the voluntary muscles of  the foetus, and probably also
in some few other muscles.
   In the third period, the fibrillae become very slender, the transverse
markings more defined, and the  nuclei altogether disappear.
   This condition  is  represented in all the fully-developed striped
muscles of animal life.
   But the striped voluntary muscular fibre, even of the adult, con-
stantly  exhibits, and  is constantly passing through the three stages
just described;  a fact not generally known.   It has  been ascertained,
indeed, since the time of Valentin, that the striped  muscular fibre of
the foetus originates in cells, and also  that cell nuclei  are contained
in each  fibre of the  adult; but it has not been perceived that  the
fibrillae  also proceed from cells, and that the stage of muscular devel-
opment, that of unstriped muscular fibre, likewise exists in the volun-
tary muscles of both  the foetus and the adult.
   It has  been supposed, as we have already seen, that the nuclei
which are  met with in the striped muscular  fibre  are scattered
throughout its entire  thickness:  this has been shown to be erroneous,
and also that the nuclei are situated only on the exterior of each fibre.
                         * Phil. Trans. 1811. 
3CS                      THE  SOLIDS.
  Now, in every  adult  striped muscular  fibre,  we find the nuclei
under the following circumstances:  some  few of them are in a free
state; others, more numerous, are contained in fibrillae, both  striped
and unstriped;  of  these fibrillae, the majority are  on the inside of the
sarcolemma; but some of them are also on its exterior, adhering to
its surface,  and constituting a considerable part  of its  substance:
lastly, internal to these nucleated  fibrillae', other fibrillae,  which  form
the chief bulk of each fibre, exist destitute of nuclei.
  With a good defining object-glass many of these unstriped fibres
may be  traced  for a considerable  distance along the fibre, and  may
be observed to contain as many as twenty nuclei.
  From these several  facts it  would thus  appear, that  striped and
unstriped muscular fibre do not represent distinct types of structure,
but that each is to be regarded  as a different stage in the development
of the same.  The unstriped muscular fibrilla passes through but one
stage of growth,  and   then its development becomes permanently
arrested: the fibrillae  of  the heart,  &c, attain  a  higher degree  of
development, the nucleated fibres  becoming marked with transverse
striae;  after  which  their growth permanently  ceases:  lastly, the
striped fibrillae  of  the  voluntary muscles  reach  the third  and last
period in the development of the" muscular tissue, having their nuclei
obliterated, and becoming exceedingly slender.
  It  would appear, also, that new fibrillae are constantly being devel-
oped, even in the adult muscular fibre.
  But certain appearances may be observed which render it extremely
probable that not merely new fibrillae are constantly being developed,
but also that new fibres are continually  being formed.
  Thus, it is a common thing to meet with unstriped and even striped
fibrillae,  which  are slightly adherent  to the external surface of the
sarcolemma; again, small muscular fibres  attached  to the larger
fibres, and  consisting  of but  very few fibrillae,  may  constantly  be
observed.   (Plate XLII. fig. 4.)
  In the uterus we have a very  remarkable example of a periodic
development and subsequent absorption of unstriped muscular fibrillae.
  The last point to which reference need  be  made is, to the doubt
expressed as  to "whether the identical corpuscles originally present"
(in the  fibre) "remain  through  life, or whether  successive crops
advance  and decay during the progress of growth and  nutrition."*
This matter is no longer doubtful: the particulars observed in relation
                       * Loc. cit. pp. 182,183. 
MUSCLE.
rrn
to the development of muscular fibre enable us to give a solution of
the difficulty.   Thus, there is no question  but  that successive crops
of corpuscles or nuclei are continually being formed in  both the
striped  and the unstriped  muscles, and that those in the former are
permanent, while in the latter they are only transitory.
  It will be  readily perceived that the  above-detailed views of the
structure and development of the muscular fibre differ, in very many
important particulars, from  those generally entertained.  According
to the views of most physiologists, the unstriped muscular fibre is the
analogue of the striped fibre; while, according  to those of the author,
the striped fibrilla is the analogue of the unstriped fibrilla, or "fibre"
of most writers.  Dr. Carpenter, in the third edition of the " Princi-
ples of Human Physiology," thus clearly gives expression to the
notion that the striped and unstriped muscular fibres are the analogues
of each other.   "From the  preceding history, it  appears  that there
is no difference at an early stage of development between the striated
and the non-striated forms of muscular fibre.   Both are simple tubes,
containing a granular matter, in which no definite arrangement can
be  traced, and  presenting enlargements  occasioned by the presence
of the nuclei.   But while the striated fibre goes on in its develop-
ment, until the fibrillae, with their alternation of light and dark spaces,
are fully produced, the non-striated retains throughout life its original
embryonic character."  The description just quoted, in its application
to the fibrilla  of the  striped and  unstriped muscle, would  be  most
true, but in its comparison of the unstriped fibrillae with the entire
striped fibre, it is completely at fault.
  There is considerable discrepancy  between the views entertained
by Bowman and Valentin, and those expressed in this work, in relation
to the development of muscle, as will be evident from the statement of
them by the  former gentleman.   "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 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 deposition  occurs in granules,
which, as  they come into view, are seen to be  disposed in the utmost
order,  according to the  two  directions  already  specified.   These
granules or sarcous elements being of the same size as in the perfect
                         24 
370
THE  SOLIDS.
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 bqfore the transverse  ones: when both
are become strongly marked, as is always the case at birth,  the nuclei
of the cells, which were before 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 perfect 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."
  According to the views entertained by the author, a striated mus-
cular  fibre,  in the earliest period of its development, consists of cells
arranged in linear series:  these unite  together, giving origin to the
fibrilla and  not  the fibre, and that each  fibrilla of a fibre  is, in like
manner, developed from cells.
  Dr. Sharpey, in the fifth edition of Quain's "Anatomy," makes the
remark, in treating of the subject of the development of muscle, "But
much still  remains to be explained  by  future investigation."  The
truth of this remark it is  conceived is, in some degree, exemplified in
the foregoing article on muscular fibre. 
MUSCLE.                            371
                                 MUSCLE.
   [To what the striation of muscular fibre is owing, is not yet satisfactorily
established.  The opinion of Drs.  Sharpey and Carpenter, again referred to
in the Appendix, and seemingly adopted by  the author, that the striation, or
dark spots on the fibrillas, indicate the cavities  of the cells which compose
each fibrilla,  is  more probably the correct explanation.   The junctions of
these cells, according to  the same authorities, are further marked by delicate
transverse  lines, intermediate between the cells.  These lines are readily
seen in the muscular fibre of the pig,  with a power of 600 diameters.
  That the striation depends on the  corrugation of  the muscular fibre, a
theory which the author seemed  disposed  to  adopt  in  his  explanation of
Plate  XLIII., fig. 6, is not probable.   The striations are too regular to result
from such  cause.
   Professor Kblliker has ascertained that  non-striated muscular fibre more
generally enters into  the structure  of different organs, than was usually
believed.   His researches  on this subject  have been very laborious, and an
abstract of the results obtained by him has been published in the eleventh
number of the "British and Foreign  Medico-Chirugical Review," for July
1850.  This abstract is so clear and concise, and affords such assistance to
the student, that it is here inserted.

     ON A  NEW  FORM OF SMOOTH OR NON-STRIATED  MUSCULAR  FIBRE.
                            BY PROFESSOR KOLLIKER.
  "Kolliker describes the smooth muscles as composed  of  short, isolated fibres,
each containing a nucleus.  He calls them muscular or contractile fibre-cells, and
gives three varieties:
  1. "Short, round, spindle-shaped, or rectangular plates, like those of epithelium,
0-01'" long, and 0-006'" broad.
  2. " Long plates of  irregular rectangular, spindle or club-like shape, with fringed
edges,  0-02'" long, and 0001'" broad.
  3. '• Narrow, spindle-shaped, round, or flat fibre, with  fine ends, which  are either
straight or wavy, 0-02'", or even 0-25'" long, and 0-002'" to 0-01'" broad.
  " The first and second of these forms are only to be found in the walls of vessels;
the first may be mistaken for the cells of epithelium.
  "These muscular fibre-cells are composed of  soft, light yellow substance, which
swells in water and acetic acid, in which  last it becomes of a paler colour.  There is
no appreciable difference between  the outer and inner parts, though in acetic acid it
would  seem as if eacli fibre-cell  had a delicate covering.  Their substance is homo-
geneous, with longitudinal stripes; and  they often contain  small pale granules,
sometimes yellow  globules of fat. Each fibre-cell has  without exception a pale
nucleus, sometimes only perceptible in acetic acid.  Its form is peculiar, being like a
small staff  rounded at each end.  The  substance of the nucleus is homogeneous;
its length is 0-006'" —0-004'", its breadth 0'0008" —000013'".   The muscular
fibre-cells lying side by side, or end to end, form the smooth muscles as they appear
to the naked eye.   They may be divided  into: 
37 2                          THE  SOLIDS.

  1. "Purely smooth muscles containing no other  tissue;  such are  those  of the
nipple, corium, of the interior of the eye, of the intestines, of the perspiratory glands
of the axilla, of the cerumen glands ot the ear, of the bladder, of the prostate, of the
vagina, of the small arteries, of the veins and lymphatics.
  2. "Mixed smooth muscles, which contain, besides the muscular fibre-cells, cellu-
lar  tissue, nuclear fibre, and elastic fibre: such are the trabecular of the spleen and
corpora cavernosa of both  sexes.  They are  also found  in the tunica dartos,  gall-
ducts, the fibres of the trigonum vesica?, the circular fibres of the larger arteries and
veins, the long and transverse fibres of the prostata, urethra, Fallopian  tubes,  and of
the  womb; they change  by imperceptible transitions into  the first form; this is the
case in the trachea,  bronchi,  urethra, the inner muscular  layer  of  the testicles,
seminal ducts, &c.
  "Kolliker says, that he has  found smooth  muscles in the skin  to  a far greater
extent than is generally supposed.  In the sub-cutaneous cellular membrane  of the
scrotum,  penis  (prepuce), and the anterior portion of the perineum,  they are  well
developed.   The greater number seems  to exist  in the  tunica dartos; in the  peri-
neum and prepuce there are fewer.  In the tunica dartos they form a muscular coat
resembling, on a small scale, the tissue of the bladder.  In the nipple and areola
(especially in the female),  the smooth muscles are  strongly developed, somewhat
resembling those of the tunica dartos, but having no fibrous covering.   In the areola,
up to the base of the nipple, they are arranged in circular order; in the nipple  they
are  circular and vertical, the ducts passing between them.  Some lie in the corium,
and form the corpus reticulare; others belong to the sub-cutaneous tissue.  Smooth
muscles are also found in every part of the body covered  with hair, in  the hair-bulb,
and in the upper portion of the corium.   In the parts not covered with hair, such as
the  palm of the hand, the  smooth muscles are wanting.  One or two bundles of
muscular fibre encircle each hair-bulb or sebaceous gland.  Kolliker  remarks, that
the  tensor choroideae does not insert itself into the processus  ciliaris, but that it lies
flat  on its anterior  surface, and that it arises from the canalis scblemmii.   The
sphincter pupilfce, he says, may be easily seen in the eye of the white  rabbit, and in
the  blue eye in  man, on  removing the uvea.   In man it is \'" broad, and forms the
pupillar edge of the iris.   He has also observed  a muscular ring near the annulus
iridis minor.  The dilator pupillse does not form a continuous membrane, but seems
to consist of isolated bundles of fibres passing between the muscles to insert them-
selves in  the  edge of the sphincter.   He has never seen the anastomosis of these
fibres mentioned by Todd and Bowman.   The writer thinks that the elements of all
these muscles are smooth muscular fibre, though he admits that he has seldom suc-
ceeded in isolating the muscular  fibre-cells in the  human  body.   He does not think
that the M. cochlearis discovered in the ear by Todd and Bowman deserves the name
of a muscle; he is rather disposed to consider it as a ligamen^us#itructure, and calls
it the ligamentum spirale; he looks upon it as a means  of" attachment for the  zonula
membranacea.  Remarking that  the smooth muscles of the intestines  resemble one
another in their histological characters, he points out one peculiarity, viz : that  they
present a knotty appearance with ends running out into fine spirals.  He thinks that
it is not improbable that the knots are due to  a contraction of the fibre.  The fibre-
cells of  the intestine seem to be striped, as if they were  composed of an envelope
and some homogeneous striped contents.   No muscular fibre  is found  among them,
but they  are covered and bound together by cellular membrane. 
MUSCLE.
373
  " The small perspiratory glands seldom  possess smooth muscular fibres, although
these are always present  in the large  perspiratory glands of the axilla, and in the
cerumen glands  of the ear.
  " Kolliker does not admit the presence of muscular fibre in the lacteal glands.
  "In the lungs he  finds  that the structure of the small and large  bronchi is the
same.  Outside  of the  epithelium they present  a layer  composed of longitudinal
fibres of areolar  tissue, and a number of strong, fine, elastic fibres.  Then follow one
or more circular layers of smooth muscular fibre, with some nuclear fibre running
transversely; lastly, a layer  of  cellular tissue, with nuclear fibre.  He never could
find muscular fibre running longitudinally through the bronchi.   With respect to the
vesicles of the lungs, he could come to no satisfactory conclusion.  Long nuclei are
seen in the walls of  the vesicles, but they are  not so long and narrow as those of
the smooth muscles,  and appear to him to belong to the  capillaries.   The smooth
muscles of the trachea and bronchi resemble in their elements those of the intestines.
In the ox, the gall-bladder, the ductus cysticus, d. choledocus, and the ducts lying
out of the substance of the liver, present a large amount of muscular fibre of the
smooth species.   It is strongly developed  in the canals, in which  it is so disposed
longitudinally;   in the gall-bladder this is not so much the case, a transverse, and
even  an oblique layer of the fibres  being placed between two longitudinal layers.
In the human body, the muscular structure is very faintly developed in the gall-ducts.
Kolliker could only discover a very delicate layer at all approaching muscular fibre.
In the pancreatic ducts of the human body, no  trace of muscular fibre exists.  In the
lacrymal apparatus there  are no muscular fibres: in the ductus stenonianus none;
the ductus whartonianus  has a very faint layer of smooth muscular fibre.
  "No part  of the internal structure of the "kidney shows traces of museular fibre;
it is only in the  calices and pelves that it becomes apparent.  The muscular fibres
of the pelves and calices  are composed of an outer longitudinal coat, and an inner
transversal layer; they are continuations of the same in the urethra, and all partake
of the general characters  of smooth  muscular fibre.   Supposing the disposition of
the muscular fibres of the bladder to  be  well known, the writer observes that the
trigonum vesicas consists of a pretty strong layer of pale  yellow fibres immediately
under the mucous membrane; this  is to  be considered as an expansion of the
longitudinal fibres of the urethra.
  " The canaliculi of the testes have no muscular fibres, but on the inner side of the
interior surface of the tunica vaginalis  communis, smooth muscular fibre is evident.
The vas deferens presents a thick layer of smooth muscular fibre,  forming an outer
longitudinal, a middle transverse, and  an  oblique layer directly under the mucous
membrane.   The canaliculi of the epididymis present  the same conditions of  their
walls as the vasa deferentia.  Kolliker thinks he has seen some muscular fibres in
the body of the epididymis.   The ductus  ejaculatorii are formed like  the vas defer-
ens ; the seminal vesicles  present also  the same conditions.  'Both coverings of the
prostate—that derived from the seminal vesicles, and  its own peculiar covering—are
more or less  muscular.
  "The pars membranacea urethras possesses but little smooth fibre, compared with
the prostate.   Under the mucous membrane (whose cellular tissue is rich in elastic
or nucleus-fibre) there  is  a layer of longitudinal fibre, mostly  composed of  fibro-
cellular membrane, containing nuclear  fibre and  contractile fibre-cells;  this layer is 
374
THE  SOLIDS.
 succeeded by another of transverse fibre belonging to the musculus urethralis; it
 also  contains smooth muscular fibre.  In the pars cavernosa urethra; the fibres  are
 but slightly developed; but they are still found at a certain depth.
    "The  corpora cavernosa  may be  considered as  highly developed  muscular
 structures, furnished with  peculiar blood-vessels, since the smooth muscular fibres
 exist in the fibrous septa, even in the glans.
   " The inner portions of the uropoietic viscera  in the female resemble those of the
 male witli regard to their  structure.   The urethra has, besides the  longitudinal
 fibres, a transverse layer of smooth  muscular fibre.   Fallopian tubes have  a thick,
 middle layer of longitudinal and transverse fibre; the elements of which are  smooth
 muscular fibre-cells, with moderate-sized nuclei.   The smooth muscular fibre is with
 difficulty isolated in the virgin state;  but in the gravid uterus it is seen in great per-
 fection.  In the fifth month Kolliker saw bundles of red fibre of the smooth muscular
 kind, mixed with cellular membrane, without nucleated fibre;  the fibre-cells were
 spindle-shaped, and very long.  As pregnancy advances, no  new cells seem to form;
 but those already formed increase in size.   Sometimes they  measure tV'""!'" 5
 they are spindle-shaped, and  ran out  into long, thin tails.   After  birth, they rapidly
 decrease in size.   The middle or vascular layer of the uterus is rich in smooth mus-
 cular fibre; it differs only from the inner and outer coat, in  the fibres crossing each
 other in every direction.
   " The ligamenta uteri anteriora et posteriora present  a red fibrous tissue, enclosed
 in the two folds of the peritoneum; in this, smooth muscular fibre maybe  traced.
 In the ligamenta  ovarii very few are found.  The writer says he has seen muscular
 fibre in the lower portion of the anterior  fold of the peritoneum;  on the ligamenta
 lata these fibres expand between the folds, and he even  thinks that they insert them-
 selves in  the walls of the  pelvis.  Directly under the mucous membrane  of  the
 vagina, a layer of muscular fibre exists, stretching from the bottom of the vagina to
 the vestibule, and containing a thick plexus of veins; it is composed of longitudinal,
 but more especially of transverse, long fibre-cells, with wavy ends.  The structure
 of  the clitoris, glans clitoridis, bulbus  vestibuli, &c, is  analogous to  that  of  the
 corpora cavernosa in the  male.
  "In the spleen of the human body, Kolliker has never been able to discover smooth
 muscular fibre, either in its covering, or in the larger fibrous bands;  but  in  the
 microscopical fibrous bands he has  found elements which lie thinks are of a muscular
 nature.  He also states, that in birds, reptiles, and fishes he has found some muscu-
 lar fibre in the fibrous bands of  the spleen.  The existence of smooth muscular
 fibre  in the blood-vessels and lymphatics is indubitable; Kolliker recommends  the
 middle-sized  arteries  and veins for examination.   In  the aorta and trunks  of  the
 pulmonary arteries, the middle coat is composed  alternately of muscular and elastic
 membrane, with fibro-cellular tissue.  These muscles consist of.fibre-cells, contain-
ing nuclei.   The larger veins of the human body present, externally to their lining, a
 single or double layer of elastic fibre, a simple coat of transverse muscular fibre-cells,
mixed with cellular tissue, to which succeeds externally a coat of longitudinal fibres.
In the middle-sized veins there is  a middle coat  of a pale reddish colour, composed
of alternate transverse and longitudinal fibres;  the former are of fibro-cellular tissue
and contractile fibre-cells.  Towards the periphery, the muscular structure decreases.
The veins of the uterus, which in the unimpregnatcd state present no peculiarities 
                                  MUSCLE.                           37 3

  acquire a great development during pregnancy with regard to length and organization.
  This does not so much proceed from the thickening of their walls, as from the
  increasing size of the fibre-cells existing in the middle coat before pregnancy, and in
  certain changes in the outer  and  inner coat caused by their acquiring a considerable
  quantity of smooth  muscular  fibre.   The very large veins which pierce the inner
  muscular coat of the uterus at the point of attachment of the placenta, and which
  communicate with its uterine portion, make an exception to this rule, as they have
  only longitudinal muscular coats, which with  the epithelium form the walls of the
  vein.
    "The following veins have no muscular structure:
    1. "The veins of the uterine portion of the placenta.
    2. "The veins  of the cerebral substance, which are formed  of  epithelium and
  cellular membrane.
    3. " The sinuses of the dura mater.
    4. "Breschet's veins of the bones.
    5. "The venous cells of the corpora cavernosa in the male and female.
    6. "Probably  the venous cells  of the spleen.   The  muscular fibres of the
  lymphatics are like those of the veins, they exist sparingly in  the trunks, and in
  greater number in the smaller branches."

                              MANIPULATION.
     Muscular fibre is best studied by placing  a small  fragment  of muscle
  on  a glass slide, moistening it with water, and tearing  it with fine needles,
  until the  fibrillae are made apparent.
     The sarcolemma  or sheath  of muscular  fibre may  be  displayed on
  rupturing the  fibrillae by tension ; the sarcolemma will sometimes  remain
  unbroken after the fibrillae are  ruptured, and may thus be examined. Another
  method is to immerse  the fibre  in water before irritability be extinguished;
  the  fibre imbibes  the  moisture, then  contracts,  and presses out the  fluid
  which raises the sheath into vesicles.
     The study of the muscular »fibre in the inferior animals is  replete with
  interest, the largest fibres being  found in fishes and reptiles.   In the lobster
  and shrimp, the  fibrillae are well seen, even after they have been  boiled.
     The muscular fibre  of the pig is worthy of  examination; it is so capable
  of being  resolved into oblong squares by sufficient magnifying power, that
  it has been adopted as a test for  object glasses  of high power.
     Mr. Quekett states that the nerves of muscular fibre are best  studied in
  the thin layer of muscle, whichforms part of the abdominal wall of the frog.
  Some of  the capillary vessels may be also here  seen:  these  vessels, how-
  ever, are best observed after they have been filled with fine injection when
• their relation to the primary fasciculi can be made apparent.
     Muscular fibre,  whether injected or not, is best preserved in fluid, in flat
  or thin glass cells, so it may be  examined with high powers.] 
376
THE  SOLIDS.
                     ART. XIX. —NERVES.

   The nervous system has been divided  into  two orders or lesser
systems; the cerebro-spinal, which includes the brain and spinal cord,
together with the  nerves  which  proceed therefrom, and  the  sympa-
thetic systems.  The former, which admits of still  further  leading
divisions, presides  over animal life, its nerves administering to sensa-
tion, and being distributed to the principal  organs  of locomotion, the
muscles, as well as  to those of  the senses; the latter is connected
with the functions of organic life, and supplies principally the  viscera
and glands with nerves.
   Corresponding with the presumed functional differences of the two
systems,  there  are also certain  structural  differences, the nature of
which will shortly be described.

                       STRUCTURE OF NERVES.
   Cerebro-spinal System.—The nervous matter  constituting the
cerebro-spinal system consists of two very distinct substances, a gray,
cineritious, cellular,  or secreting structure, and a white,  conducting,
or tubular structure.
   Secreting or Cellular Structure.—The  very numerous situations
in which the  gray  matter of the brain and spinal cord is encountered
need not here  be  described  at any length: it  will be sufficient to
observe, that  in the cerebrum it occupies principally an external sit-
uation, a layer  of it  of about the one-eighth of an inch in thickness,
extending over the entire surface  of its convolutions; but that it is
also found in lesser quantities in several localities  in the interior of
the cerebrum, as in the optic thalami, corpora striata, tuber cinereum,
crura cerebri, &c.; that, on the  other hand, in  the cerebellum, pons
Varollii, medulla oblongata, and spinal cord, it is deep seated, forming
the central portion of these organs.
   The  secreting substance, or gray matter of the brain,  is made up
of a granular base, in which are contained  numerous nucleated cells
of different sizes and  forms.  In the gray matter of the convolutions of
the brain the granular base is very abundant, the cells small and round,
and in less proportion than the base itself:  in the tuber cinereum, in
the cerebellum, and in the  gray matter of the cord, the small granular
cells are extremely abundant, and the granular  base is  diminished in
quantity.   (See Plate XLV. figs. 2, 3.) 
NERVES.
377
  Now, the granular base and the small granular cells constitute the
principal  portion  of the substance  of  the  gray matter, wherever
encountered: in certain localities, however, cells of different forms
and  of considerable magnitude  are met with: these cells have been
termed ganglion cells.
  Ganglion Cells.—Ganglion cells are encountered  in  different por-
tions of the cerebro-spinal system, as in the locus niger of the crura
cerebri, in the gray matter of the arbor vitae, and corpus dentatum of
the cerebellum; in the medulla oblongata; in the spinal  cord for its
entire length, and according to Valentin and Purkinje, in all the extent
of the cerebral  hemispheres, especially in the posterior lobes, and in
the gray lamina of  the spiral fold of the cornu Ammonis.
  These  cells vary greatly both  in  size  and shape; many  of them
attain  a very considerable  diameter, and they are, almost  without
exception, all provided  with caudate prolongations, which  are fre-
quently branched.   (See Plate XLIV. fig. 4.)
  The ganglioniform cells of the locus  niger are for the most part
small, and irregularly  stelliform in shape: those of the gray matter
of  the  cerebellum  are  pyriform, the spinous and often-branched
processes, usually two or  three  in  number, proceeding from their
narrow extremities: many of the  cells of the medulla oblongata are
triangular, the  spines arising from the angles, and  being much pro-
duced, those of the spinal cord are  usually very large,  irregular in
form, and are furnished with numerous prolongations.
  These  cells  are  highly  and  uniformly granular: they frequently
contain pigmentary matter,  and  enclose a  nucleus, which  again is
provided  with  its nucleolus, and  both of which are remarkable  for
their exceeding brilliancy.
  Ganglion cells are, doubtless, connected with the  secretion  of the
nervous element or fluid:  the use of the prolongations  with which
they are furnished, and the precise relation of these with the  adjacent
structures, the smaller secreting cells  and the nerve tubules, is not yet
well ascertained: it has been  conjectured, however, that the caudiform
processes  are directly continuous with the tubules; a view  which is
certainly  incorrect.
  Mixed up with the ganglion cells wherever met with, but especially
with those occurring in the gray matter of the cerebellum and spinal
cord, a considerable number of branched  and nucleated fibres may be
seen, similar in appearance and structure to those of unstriped muscle,
and more particularly resembling the gelatinous filaments  of  the sym-
pathetic system, from which  they  in all probability really  proceed. 
378
THE  SOLIDS.
  There is a  second description of ganglion  cell, not contained  in
either the brain or spinal cord, but  found in  the various ganglia,  as
the  Casserian, Optic, Ophthalmic, Spinal,  &c, formed in connexion
with the nerves of the cerebro-spinal and  sympathetic  systems, and
which may be here described.
  These cells resemble the ganglion corpuscles already  noticed  in
their general  structure, but  differ from  them in form, being more  or
less round in shape, and destitute of the branched processes belonging
to the latter.   (See Plate XLV. fig.  4.)
  The mode of multiplication of ganglion cells  is not well understood:
it is possible that the numerous granules  contained in each are the
germs of the  future cells   Adhering to the surface of many of the
larger ganglion cells  of the second form, a number of nucleated par-
ticles or lesser cells may frequently  be  observed, forming a kind  of
capsule  around  them, which,  however, is entirely  external  to the
proper membrane of the cells.   (See Plate XLV. fig. 4.)
  Tubular Structure.—The white  fibrous  substance  of the brain,
spinal cord, the nerves of motion and of special sensation, is composed
of unbranched tubules, the diameter of which is subject to considerable
variation.  The tubules  of  the cerebrum  are exceedingly slender,  as
are  also those of the  nerves of special sense: those of the cerebellum,
spinal cord, posterior  root of spinal  nerves, and of the  sympathetic
system,  are  of somewhat larger calibre,  while those  of the motor
nerves are of still larger size, and of firmer texture.  See the figures.
  The tubules of the white  substance of the cerebrum are especially
prone to become dilated at intervals, or varicose.  (See Plate XLIV.
fig. 7.)   This condition  was formerly supposed to be natural, and it
was presumed that by  this character  the nerves of special sense
could be  discriminated from those  of motion:  there is little doubt,    ^
however,  but that this varicose condition of the fibres is  abnormal,
and that  it is produced  by the pressure  and disturbance to which
they are subject during examination. The tubules of the cerebellum
are subject to a like  change, although in a less degree; those of the
nerves of motion are but  little prone  to the alteration, these becoming,
when much disturbed, broken into fragments, many of which assume
a globular form, and all of which are greatly corrugated.   (See Plate
XLIV.  fig. 1.)
  The  nerve tubules  contain  a fluid matter, and it is the collection
of this  fluid  in  certain parts  of each tubule, the  result of pressure,
which occasions the distension of the membranous wall of the tubes 
NERVES.
379
and which gives  rise to the varicose condition  described.   Such is,
at least, the  most probable explanation  of the exact nature of this
condition.
   The  tubules of the cerebrum, cerebellum, spinal cord, and motor
nerves,  &c, present an average diameter: nevertheless, much differ-
ence may be detected in the size of the tubules taken  from  the  same
portion  of the nervous system:  those of the spinal cord agree in their
average size with those of the cerebellum.
   The  tubes of the cerebrum, of the nerves of  special sense, and of
the cerebellum, are  so  small, that it is impossible to ascertain with
certainty the amount of organization which really belongs to them:
this, however, is not the case wdth those  of the  motor nerves, which
are so much  larger.   (See  Plate XLIV. fig. 1.)
   Each tube of  a motor nerve  consists of an  investing  sheath or
neurilemma,  an inner  elastic  and but  little consistent matter, the
"white  substance of Schwann," which  forms  a pseudo membrane,
and which includes the third constituent  of the nerve  tube, a soft and
semi-fluid  matter, which,  however, would appear in  some cases to
become solid, and to exhibit a fibrous fracture:  this matter has been
termed  the "axis  cylinder."
   It is a matter of some difficulty to display the investing  sheath, or
neurilemma,  around the fibres  in their fresh  and unaltered state:  it
may,  however, be easily detected, and its structure recognised  in a
portion  of motor nerve which  has been  immersed  for some hours in
spirit: it will then be seen  that it is made up of nucleated  fibres, the
nuclei in the sheath  of fcetal nerve tubes being  of  considerable  size,
and presenting a smooth aspect.  (See Plate  XLIV. fig. 2.)
   Todd and Bowman describe  the outer  membrane of  the nerve
tube,  and to which alone  the  word  neurilemma should be  applied,
"as an  homogenous and probably elastic tissue of extreme delicacy,
analogous to  the sarcolemma of striped muscle, and, according to our
observation, not presenting any such distinct longitudinal  or oblique
fibres in its composition as have been  described by some writers."
It will be observed  that this description does not  accord  with  that
given by the  author.
   The white substance of Schwann, on  the contrary, is best seen in
the motor  nerve  tubes, which  are  perfectly recent, and which have
been but little disturbed: its thickness is indicated by a double line
which runs along each side of the tube:  it does not  present any trace
of organization: it is very elastic, and its  contraction gives rise to the 
380
THE  SOLIDS.
corrugated appearance presented by the tubes of motor nerves which
have been disturbed and broken.   (Plate XLIV. fig. 1.)
  The existence of -the third constituent of the nerve tube, the " axis
cylinder" of Rosenthal and Purkinje, is best determined by the immer-
sion of the fibres in either ether or acetic acid, which breaks it up into
granules and vesicles.   (Plate XLIV. fig.  3.)
  In albumen the nerve tubes and nervous tissue in general undergo
but little alteration, and it is therefore in this fluid that  its examination
is best conducted.
  But the  tubes  of  the  white fibrous material of the cerebrum,
cerebellum, and spinal marrow, just described, form one element only
of its structure; another  is invariably present,  forming  indeed the
greater  portion of its  substance; and it is somewhat strange that it
should have been  overlooked by observers:  this element consists of
globules of every possible size, which, when  free from  pressure and
undisturbed, are perfectly spherical, but which  are  put  out  of shape
by the slightest compression or disturbance.  It is not easy to deter-
mine whether  these globules are true cells  or  not: they  present the
greatest possible variety of size: they have the colour and consistence
of oil;  bu.t nevertheless appear to be hollow, and frequently present  a
spot which bears much resemblance to a nucleus.  (See Plate  XLIV.
fig- 6.)
  It now  only remains to be observed,  that the nerves of  special
sense, as the optic, olfactory,  and auditory, present a structure pre-
cisely analogous to that of the white substance of the cerebrum.
  Sympathetic System.—The  nerves entering into the formation
of the sympathetic or organic system, differ both in appearance and
structure from  those  derived  from the cerebro-spinal  system:  thus,
the great  sympathetic cord itself, as  well as the  organic nerves con-
nected with it, present a reddish gray colour, are soft and gelatinous,
and do not readily admit of  division in the longitudinal direction,
although they are easily torn across  by any extending force: these
differences of colour and of consistence are dependent  upon a differ-
ence of structure.  The great sympathetic cord itself,  and  the organic
nerves connected with it,  are  composed of two distinct descriptions
of fibre; first, of the ordinary tubular fibre, which,  however, is of
small diameter, and  therefore readily becomes varicose, and  second,
of nucleated filaments, in every appreciable respect resembling those
of unstriped muscular fibre.  Henle has called these fibres "gelatinous
nerve fibres." 
NERVES.
381
   The relative proportions existing between these two kinds of fibre
 differ  in different nerves:  thus, in some cases, the gelatinous fibres
 are by far the most numerous; in others, the  tubular fibres prepon-
 derate.   The  gelatinous or gray filaments are best seen in what are
 called  the roots of the sympathetic; that is to say, in the branches
 which, accompanying the carotid artery, proceed  from the superior
 cervical ganglion to the fifth and sixth pair of cerebral nerves, and in
 those which descend from  the same ganglion and follow  the course
 of the carotid.  In these the proportion of tubular fibres is but small,
 as one to six;  and they are also isolated from each other, each being
 surrounded with a number of  gelatinous  fibres.  This disposition of
 the  nucleated fibres has led Valentin to consider that  they form  a
 sheath around  the tubular fibres, each gray nerve, according to that
 observer, being composed of a number of fascicles or bundles.  Henle,
 however, objects to this view, considering that the fibres are too large
 for a sheath, and remarking that the gray nerves do not separate into
 such bundles, but divide much more readily in such a way as that the
 tubular fibre is found at the border of the bundle.   Henle, therefore,
 considers it to be more natural to regard the gray nerves as  forming
 solid threads, composed of nucleated filaments,  between  which the
 tubular fibres run.
   The tubular fibres are more numerous  than in  the  roots of the
 great  sympathetic,  in  the majority of the visceral nerves, in  the
 branches  which proceed from the cardiac and  hypo-gastric plexuses,
 &c; in these the tubular fibres may be seen enclosed within the gray
 filaments, forming many bundles.  Their number becomes still more
 considerable in the great sympathetic cord itself and the splanchnic
 nerves; the  cardiac  nerves  are almost entirely formed of tubular
 fibres.  In all these nerves the tubular fibres are observed to be of
 smaller diameter than they are in those which are distributed to the
 voluntary muscles.
   In  consequence of the great difference which exists between  the
 structure of the tubular nerve fibre and that  of the gelatinous nerve
 fibre, it has been a matter of doubt with some observers  whether the
 latter should be  regarded as a true nerve fibre or not.
   The following is a brief enumeration of the  various anatomical
 and  microscopical  facts hitherto recorded,  both in favour of and
opposed to the  opinion  of  the nervous  character of the gelatinous
filaments just described.
   The chief structural considerations which may be urged in favour 
382
THE  SOLIDS.
 of the opinion that the nucleated filaments associated with the various
 nerves of the sympathetic system are true nerve filaments are—
   1st.  The origin of the gelatinous filaments from the ganglia  of the
 sympathetic, as first distinctly affirmed in the researches of Volkmann
 and Bidder.*
   2d.  The  tubular character  of these filaments,  as shown  by  T.
 Wharton Jones.f
   3d.  The  peripheral  distribution  of the  gelatinous  filaments,  as
 asserted by many observers, but particularly  by Bidder, who even
 states  that he  succeeded in counting their number in the  transparent
 septum of the auricles of the frog's heart.
   4th.  The peculiar structure of the ganglion caecum, discovered by
 Mr. T. Wharton Jones, in connexion  with one  of the ciliary nerves
 of the  dog.J
   5th.  The variable, yet fixed proportions of gelatinous and tubular
 fibres occurring in different nerves, as described especially by Henle.
   6th.  The occurrence, as stated by Todd and Bowman, 6f nucleated
 filaments very similar to the gelatinous fibres of the sympathetic, "in
 parts where their nervous character is indubitable, as  in the olfactory
 filaments, and the  nerve in the axis of the Pacinian corpuscle, exhibits
 very much the same appearance, save that it is  devoid of  nuclei."§
   7th.   The resemblance borne,  according  to the  observations of
 Schwann,|| between the tubular  nerve fibre in the  early stages  of its
 development, in which  it is described as being  nucleated,  and the
 adult gelatinous fibre.
   8th.   The origin of the gelatinous filaments  from the cells  themselves
 composing the ganglia of the  sympathetic,  as the  observations of
 several observers tend to prove.
   These various facts thus briefly referred to, could they  all  be fully
depended  upon, would,  doubtless, make out not merely a  strong, but
even a convincing and  unanswerable  case in favour of the  nervous
character of the gelatinous filaments:  unfortunately,  however, those
facts which, if they could be relied  upon, would be the most conclu-
sive, are  open  to  question: such,  for  instance,  as  the   peripheral
distribution of  the gelatinous filaments, their presumed origin from
  * Die Selbslandigkeit des  Sympalhisken Nervensxjslems  durch Analomische Unter-
suchungen nachgewiesen Von J. H. Bidder und A. W. W. Volkmann. Leipsig, 1842.
  f Lancet, April 24th, 1847.                j Lancet, November  14th, 1846.
  \  Physiological Anatomy, part iii. p. 142.
  || See Wagner's Physiology, translation by Willis. 
NERVES.
383
the ganglionic corpuscles, and the asserted resemblance between  the
tubular nerve fibre in an early stage of its development and the fully
grown gelatinous filament: it will presently be shown, indeed,  in the
observations on  the growth  of  the primitive  nerve tubule, that no
such resemblance exists.
   Subtracting, then,  the  points referred  to in the 3d,  7th, and  8th
headings, no one conclusive  fact remains of the  position that  the
gelatinous fibres are really nervous.
   Against  the opinion that the gelatinous filaments are nervous, may
be urged:
   1st.  The positive structural identity between the gelatinous  nerve
filament and the fibrilla of unstriped muscle, and the great improba-
bility, as a consequence, that one and the same structure should have
to perform  two such distinct functions as must necessarily belong to
a muscular fibre  and a nerve tube.
   2d.  The  apparent  structural  unfitness of nucleated filaments  to
serve as a conducting medium of the  nervous force.
   3d.  The evidently tubular  character of the nerve filaments in parts
which, from their nature, we should expect would be preeminently
supplied by the gelatinous filaments.
   4th. The fact of the  non-occurrence of gelatinous  fibres, separate
from the tubular, is strongly opposed  to the idea of the independence
of the former.
   The above short summary will serve to give some idea of the state
of the much-canvassed  question of the nervous or non-nervous  char-
acter of the gray or gelatinous filaments of the sympathetic.

                       STRUCTURE OF GANGLIA.
   The ganglia consist of the peculiar globules already described, of
nerve tubules, and of gelatinous filaments.
   Each ganglion is enclosed in  an investing tunic of fibrous tissue*
a continuation of the common envelope of the nerves which enter and
depart from it, and which  sends  down dissepiments which divide  the
contained globules into parcels, and thereby give the ganglion the gen-
eral arrangement and character of a gland.
   The gelatinous nerve filaments in the ganglion form  a kind of  inner
capsule, and their arrangement is thus described by Henle: "Besides
the nervous fibres  properly so called of the  soft nerves, one meets
with also, in the  ganglions of the great sympathetic, gelatinous  fibres
which have special relations with the ganglionic globules.  The  fibres 
3S4
THE  SOLIDS.
of a bundle expand in the form  of a funnel, in order to embrace a
globule or a series of globules, and unite together afterwards afresh,
to separate again a second time.  In this way we often come to draw
out of a ganglion entire threads of gelatinous fibres, which are dilated,
in the manner of a chain of pearls, and enclosing the globules in their
dilatations."
   The  proper  tubular fibres enter the divisions of the ganglion in
bundles, subsequently separate from each other, and ramify among the
ganglion globules in a waved and serpentine manner.
   The arrangement of the ganglion globules and nerve tubules just
indicated, tends to show that these  are  really  the  only essential
elements of a ganglion.
   The ganglia  are supplied with blood-vessels.
   It will be apparent from the above description that the ganglia have
all  the  structural characteristics of glands, and therefore there can
be little question but that they are really glandular organs, and that
the tubular fibres  which pass  through them  carry away the fluid,
which is destined to exercise its influence on the  parts and organs to
which the nerves are  themselves  distributed.
   The question as to  the origin of either the tubular fibre or the gela-
tinous filament  from the ganglionary corpuscles, is still an undecided
one, the weight of evidence being opposed to the idea that either ordei
of .fibres has any origin from these corpuscles.

                   ORIGIN AND TERMINATION OF NERVES.
   Origin.—But little that is certain is known respecting the exact
mode of origin of the numerous tubules composing the nerves, and of
the precise relation of these with the cellular or secreting element of
the ganglionic centres.  The observations of Dr. Lonsdale,* however,
render it highly probable that the  greater portion at least of the nerve
tubes have a looped origin in the brain and spinal cord: that gentle-
man having made out the interesting fact, that  in two foetuses, in the
one of which both the brain and spinal cord were deficient, and in the
other the brain only,  the extremities of the nerves, which extended
into the cavities of the spinal column and cranium, were made up of
looped nerve tubes imbedded in an imperfectly developed granular and
cellular matter,  apparently of a  ganglionic character.   Now, from
what is known  respecting the laws of development, it would appear to

           * Edinburgh Medical and Surgical Journal, No. cxvii. 
NERVES.
3S5
be a perfectly justifiable and natural inference, that the nerve tubes,
when fully developed, have a similar mode of origin.
  According to some  observers, certain nerve tubes are connected
with and take their origin from the prolongations with which the cau-
date variety of ganglionary cells are provided;  this view, however, is
confidently  denied by many other investigators, and  the point is one
which is still involved in considerable uncertainty:  for myself, I would
observe, that I have never succeeded in making a single observation
favourable  to  such  a  conclusion.  Notwithstanding, hovvever, the
doubts which  are now entertained respecting the modes of origin of
nerve tubes, the question is assuredly one which, at some future day,
will be satisfactorily determined by direct observation.
  It is also still uncertain whether  nerve tubules  originate in the
ganglia not included in the brain, as in those connected with the
encephalic nerves, and  those of the sympathetic system.
   When  speaking in the preceding remarks of the origin of nerves,
that extremity of them is implied which is in connexion with the brain
and spinal cord:  it is questionable, however, in the case of the nerves
of special sense, whether it would not be more  proper to  consider
their  peripheral rather than their central extremities  as their true
origins; a view supported  by the consideration  that the sensations
arise in, and proceed from, the organs of the senses inwards towards
the brain, the  great centre  of nervous structure and  force, as well as
by the fact, that the peripheral  extremities of these nerves are gener-
ally, if not invariably, connected with  ganglionic  cells;  such  an
association of the two  elements is known to exist in the eye, in the
ear, in the nose, and probably exists also in the papillae of the tongue
and skin.
  Termination.—It was not known until within  the last four or five
years that  nerves had  any real termination: it was up to that time
generally considered that  the nerve  tubes  invariably ended in the
same manner as it is now supposed that they originate, viz: in loops;
and there can  be little  question but that such a mode of termination,
though not universal, is at least very frequent: thus, the arrangement
of the primitive nerve fibres in loops has been described by Valentin,
in the pulps  of the teeth; by Miiller, in the membrana nictitans, and
in the mucous membrane of the throat of the frog; in the papillae  of
the  skin and tongue, by Todd and Bowman.   The loops are formed
by one or more of the  nerve tubes,  separating themselves from the
bundle of tubes composing every nerve of any magnitude, and after-
                           25 
386                       THE  SOLIDS.

wards either passing into  and mingling with those of a neighbouring
nerve, or else returning back to  that from which originally it started.
   It is now, however, very certain  that  some  at  least of the  nerve
tubes have a real  termination: this is indisputably the case with the
single filaments which enter the Pacinian bodies; it has also been shown
to occur with many of the primitive tubes distributed to  muscles.

                          PACINIAN BODIES.*
   The Pacinian bodies are found in considerable numbers attached
to the cutaneous nerves of the hands and feet, especially to those of
the extremities of the fingers and toes;  they are also met  with, though
more sparingly, on other spinal nerves, on the plexuses of the sympa-
thetic, but never  on the  nerves  of motion, and in the mesentery; in
that of the human  subject, however, they are only with great difficulty
to be  discovered, owing to its thickness, and the quantity of fat usually
contained in it: in the mesentery of the smaller mammalia, as the cat,
rabbit, &c, and more particularly when these are in a lean state, they
may be readily discerned with the naked eye, and the  entire of their
structure followed out without even the employment of a reagent:  it
is, therefore, in these animals that they are studied to most advantage.
   The Pacinian  bodies vary greatly in size, but are usually as large
as the head  of a pin of ordinary magnitude;  they are of an oval or
pyriform  shape,  are  perfectly  translucent,  attached to the  nerve
filaments by short pedicles, and occur either singly  or sometimes in
pairs.  (See Plate XLVI. fig. 1.)
   So large are these  peculiar bodies, that the whole of their structure
may be followed out  with object  glasses of an inch and half-inch foci;
when examined with these magnifying powers, each  Pacinian body is
observed  to consist of numerous  concentric lamellae  or capsules
disposed with much  regularity;  these  lamellae are formed of white
fibrous tissue, contain numerous nuclei  in  their substance,  and are
separated from each  other by distinct intervals which contain fluid;
the spaces intervening between  the plates do not communicate and
diminish gradually, but regularly from without inwards, so that the
  *The discovery of  these remarkable  bodies constitutes one of the happiest and
most beautiful results of the application of the microscope to  minute anatomy.
Pacini first noticed them in 1830, subsequently in 1835; but it was  not until 1840
that he gave an account of them.—(Nuoci organi scoperli net Corpo umano dal DoU
Filippo Pacini, Pistoja.)   A. G. Andral, Camus, and Lacroix, announced their exist-
ence at a Concours at Paris, in 1833, but do not appear to have recognised their real
character. 
NERVES.
387
central lamellae are almost in contact with each other, from which
cause they present a darker aspect than do those having appreciable
spaces  dividing them  the one from  the other: these capsules  have
been distinguished from  the  rest by the term the  "inner system of
capsules."  It  is this regular disposition of the lamellae, together with
their gradual approximation, which imparts so beautiful an appearance
to these strangely constituted organs.  The capsules, however, are
not continued to the very centre of the Pacinian body; but in that
situation a cavity, having a somewhat elliptical form, and filled with
fluid, exists.  This cavity opens externally by means of a canal which
pierces the whole  of the lamellae, and the  sides of which canal are
formed by the  union of those lamellae ; into this canal a single nerve
tube passes, enters the central cavity just described, which it trav-
erses from  end to  end in a  straight line, terminating in  a slightly
enlarged extremity, which is described as being attached to the inner
wall of the distal end of the central chamber; the nerve tube, imme-
diately on its entrance into this chamber, loses its double and defined
border, in consequence, it is  presumed, of the absence of the white
substance of Schwann.   (Plate XLVI. figs. 2, 3.)
   Such is a brief  and general description of the Pacinian body; one
or two other  points of a less evident character still  remain  to be
noticed.  It  has been  stated that  the  capsules  contain  elongated
nuclei in their  parietes, that  they are formed of fibrous  tissue, and
that the spaces between them have no communication  with  each
other:  if the outer and  larger capsules be  carefully  examined, it will
frequently be observed that they present a double edge, separated by
a faint  interval, and conveying the  impression that each  capsule is
made up  of two distinct membranes; it is  in this  interval  that the
nuclei  are lodged:  that the inter-capsular spaces do not communicate
with each other, is proved by the fact, that  when the outer  capsules
are pierced through, the  fluid escapes only from the spaces which
have  been  opened  into; if the  whole  of  the  capsules have  been
divided, the entire corpuscle  immediately collapses.   (It is a curious
fact that a Pacinian body, allowed to dry up, does" not again absorb
fluid, and expand to its natural size.)   It has also been observed that
the capsules  are united to each other at the proximate extremity of
the Pacinian body along the sides  of the canal already described:
according to Pacini, they are also bound together at the distal end by
a band of fibrous  tissue, which he  calls the  "inter-capsular liga-
ment:"  the existence of this ligament has been denied by Henle and 
388
THE  SOLIDS.
Kolliker.*   Todd  and Bowman do not deny its existence, but state
that they have seldom seen it reach  the surface of the corpuscle.!
   Pacinian  bodies  not unfrequently present varieties of form and
structure: it is possible that  many of these admit of explanation on
the supposition that in some instances  they are multiplied by self-
division:  thus, sometimes the distal end of the  central  chamber is
bifid, the  nerve tube being also divided; in others, a single corpuscle
will be found to contain two  distinct chambers and nerve tubes, each
being surrounded by a certain  number of capsules, but which again
are themselves included in a  number of other capsules which embrace
both the  sets of inner membranes: again, in other instances, two
Pacinian corpuscles, entirely  formed, but yet not altogether separated
from each other, being connected by a few of the capsules, will be
situated  upon  a  single primitive  nerve tube: a fourth  peculiarity,
which may be noticed more  frequently than any of the others, is the
curling back of the extremity of the central  chamber, the innermost
capsules describing the same curvature.   (See Plate XLVI. figs. 4, 5.)

            •DEVELOPMENT AND REGENERATION OF NERVOUS TISSUE.
  Development of nerve fibres.—The following is the account given
by Schwann of the  development of the nervous cords as rendered by
Willis in his translation of Wagner's "Physiology," the references to
the figures only being omitted.  "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  difficulty of distinguishing nervous cells while yet
in their  primary state  from  the indifferent cells out of which entire
organs are evolved.   When first a nerve can be distinguished as such,
it presents itself as  a pale cord with  a longitudinal fibrillation, and in
this cord a multitude of nuclei are  apparent.  It is  easy to  detach
individual filaments from a cord of this kind,.....in  the interior
of which many nuclei  are included,  similar to those of  the primitive
muscular fasiculus, but at a greater distance from one another.  The
filaments are pale, granulated, and (as appears by  their farther devel-
opment)  hollow.  At this period, as in muscle, a secondary  deposit
takes  place  upon the inner aspect of the  cell membrane  of the
  * Ueber die Pacinischen Kbrperchen an den Nerven des Menschen  und der Sauge-
ihicre.  Zurich, 1844.
  t Physiological Anatomy, vol. i. p. 397. 
NERVES-
389
secondary nervous  cell.   This secondary deposit  is a fatty white-
coloured substance, and it is through this that  the nerve acquires its
opacity.   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.   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 aspect of the cell membrane, and of greater or
less thickness;  3d, of a substance, which is frequently firm or consist-
ent, included within the cells,  the band of  Remak."
   The author's observations lead him to entertain views of the devel-
opment  of the primitive  nerve tube essentially distinct from those
expressed by  Schwann  in the account quoted^above: according to
these observations, the outer  covering of the nerve tube  does not
consist of a structureless membrane, as is supposed  by Schwann, as
well as most other observers, but is constituted of a nucleated form
of  fibrous tissue.   (See  Plate XLIV. fig.  2.)   Now,   the  nuclei
observed by Schwann the  author believes to be  concerned  in the
development of the fibres, of which  the  proper membrane of each
primitive nerve tube is wholly constituted, and that  they do not by
their growth give origin to a transparent tubular membrane.
   In the nerve tubes of both young and adult animals, smooth bodies
of an oval form and large size, their  diameter exceeding that of the
tube itself, may always be observed; the nature  of these, and the
part taken by them in the structure and development of the nerve
tube, I have not been able to determine.
   Development of  Glandular Nerve or  Ganglionary  Cells.—The
nervous  matter composing the two or three  systems into which, in
the present day, it is divided, presents all the essential and distinctive
characters of a true gland, so that its description  would  have been
more correctly given under the general heading of " Glands."
   The nerve or ganglionary cells present essentially the same structure
as all other glandular cells, and are doubtless continually passing through 
390
THE  SOLIDS.
the same phases of development and destruction during the progress
of nutrition and secretion.
   The secreting or glandular cells m the brain and spinal marrow are,
for the most part, aggregated into distinct masses, the term ganglia
being equally applicable to these  masses as it is to those  existing in
connexion with the nerves of the sympathetic  system.   Henle con-
siders that the principal development of new cells takes place on  the
outer surface of the brain, which is the most vascular from its con-
tiguity to the pia mater, and that the more mature cells are gradually
conveyed inwards, coming thus into nearer connexion with the tubu-
lar or conducting fibres, the  disintegration  and  removal of the older
cells determining the  movement of the cells from without inwards.
This view,  as applied to the gray matter of the convolutions of  the
brain, is  probably  correct, and is to some extent confirmed by an
observation which I made  several months since, viz:  that the cortical
substance of the cerebellum consists of two distinct portions, separated
by a well-defined line,  perceptible with a common magnifying-glass:
the outer portion is made up of a granular base, containing but few
fully-developed cells, while the inner portion  consists almost entirely
of completely-formed cells.  The distinct separation of the cortical
or secreting matter of the cerebellum into two portions is very remark-
able, and the purpose fulfilled by such an arrangement wholly obscure.
   Regeneration of Nervous Matter.—The regeneration of the primi-
tive nerve tube admits of proof, both by experiment and direct observ-
ation.  The experimental proof  consists  in the simple  division  of
nerves, and even in the removal of portions of them: the parts to
which the  nerve is distributed, of course  at first, lose their sensory
and  motor endowments:  these, however,  after a variable time,  are
more or less perfectly recovered, thus  completing the experimental
proof.  The direct proof is derived from  the  former: the recovery
of the power of a nerve  after the excision of a portion of it, argues
strongly  the fact of the regeneration of the nerve  tubes; and this
result, by a careful microscopic examination, can be positivelv demon-
strated :  the number of tubes  in the renewed part  of the nerve is
stated, however, to be less than in  the  original portions;  and this in
part explains the reason of the restoration of the functions of a divided
nerve being usually but imperfect.  Other proofs of the  regeneration
of the nerve tubes  may be gathered from the more  or less  complete
restoration of various sensitive and motor parts of the body, as well
as from the reunion of parts which have been entirely detached from
the body, as the nose, the top of the finger, &c. 
I
                           NERVES.                        391

  With respect to the regeneration  of the glandular element  of the
nervous  matter, but  little definite or microscopic is  known: from
analogy, however, it may be inferred, that like other cellular structures,
as the epidermis, epithelium, &c, it  also is capable of a more  or less
complete reproduction.

                     RESEARCHES OF M. ROBIN.
  The following is a translation of an abstract made by  the  author
himself, M. C. Robin, of a paper communicated to the Royal Academy
of Sciences at the Seance  of June  21st,  1847, entitled "Researches
on the Two Orders of Elementary Nerve Tubes, and the Two  Orders
of Ganglionary Globules which correspond to them."
  " The  end of these researches is to show that the ganglions of the
spinal nerves and of the great sympathetic,  do not give origin to
elementary  nerve tubes, as many modern anatomists admit, as Han-
nover, Valentin, Remak, Bidder,  and Volkmann, &c, &c.;  but that
all  the nerve tubes  arise exclusively from the  spinal  cord and the
encephalon; consequently that one  can  only  regard these ganglions
as special little  nervous centres, performing, with respect to certain
functions, the same  office as  does the cerebro-spinal  centre  for the
other functions.  These reflections naturally occur to the  mind when
one sees the cavity of the tubes or elementary nerve fibres given off
from  the spinal cord, or from  the  encephalon, merge into the  cavity
of the ganglionary globules at one of their poles, and reappear at the
opposite pole of the globule in the same manner that they  entered.
  "Setting out from a globule  (cell), these  nerve tubes proceed  to lose
themselves in the organs.   Thus, those peculiar cells, the agglomera-
tion of which  constitutes  the  ganglions of nerves, are no  other than
organs which are interposed between the origin of the nerve tube and
its termination at a determined point of its course, and, perhaps, there
is more than one upon each  tube: they interrupt it in its course to
allow it  once more to reappear; they change  it, they  modify its
structure at a point to immediately restore it.
  "The authors who have hitherto written upon the subject have not
observed the entrance and exit of each  elementary tube  at the two
opposite poles of each globule, but only the one  or the other.  It is
this circumstance which has led them to consider each of these gang-
lionary globules as a little nervous centre  of origin for each tube.
  "There is yet another fact, still more important than the first, which
has not been pointed out by anatomists who have studied the structure
of nerves. 
392
THE  SOLIDS.
  "They  have all  described but one order of globules: there are,
nevertheless, two which differ, the one from the other, in numerous
characters, deduced from the consideration  of size, form, contents,
walls, &c.  One of these  orders of globules  is always in connexion
with the elementary nerve tubes of animal life, or the large tubes, &c.
The other is associated especially with the elementary tubes of organic
or sympathetic life, or with the small tubes, &c.  One never finds the
large tubes communicating  with the second order  of globules, and
reciprocally the small tubes are never in connexion with  the poles of
the globules of the first order.
  "It follows, from  these facts, that one can no longer doubt  the
existence  of the two orders  (altogether distinct) of elementary nerve
tubes named above, which, nevertheless, some authors have  done
recently.   (Kolliker.)
  " The two orders of globules, and of the corresponding tubes, exist
in the posterior or sensitive roots of the nerves of the spinal cord, but
the globules do not exist in the anterior or motor roots.
  " They exist also in the ganglions  of the encephalic  nerves and of
the great  sympathetic;  only in  these last there is  a  much greater
number of globules and of slender tubes, than of globules  and of large
tubes (thirty or fifty to one), more or less according to  the ganglions.
In the spinal ganglions, on the contrary,  there are about four or five
globules and large tubes to one of the other kind.
  "These facts tend to  confirm  the  observations of anatomists who
have pointed out the existence of the two orders of elementary tubes
in the nerves of animal life,  and  those of the great sympathetic, but
with predominance of the large tubes in  the first, and of the slender
tubes in the second; notwithstanding which, no  one of  them  has
pointed out the  existence and the difference of the two  orders of
ganglionary globules,
  "The absence of ganglionary globules on the anterior or motor
roots of the spinal nerves  anatomically distinguishes the elementarv
tubes of motor nerves of animal life from those of the sensitive nerves.
But this decisive character can be remarked only in  the short course
of the roots of the spinal nerves before their union and the mixture of
their tubes.  If wishing to push still further the deductions to be drawn
from the  preceding facts, we demand of ourselves what functions
should be  attributed  to  the  ganglionary globules, we should answer,
that they  are  the modifiers  of the action which takes place  in  the
sensitive and in the organic  nerves;  but it is impossible to determine
the nature of this modification. 
NERVES.
393
  "Since the  ganglia of the sympathetic and of the cerebro-spinal
nerves enclose the same ganglionary globules, and the same element-
ary tubes, but  only in different proportions, we  see  that we cannot,
with Reil, Bichat, &c, acknowledge two nervous systems independent
of each other.   This opinion is founded on the communications of
the great sympathetic with  the  spinal nerves;  on the fact of nerves
being furnished to the abdominal diaphragm of birds, exclusively by
the great sympathetic (Sappey) on the partial and successive substi-
tution  of sympathetic nerves for  spinal and encephalic in a great
many vertebrata."
  The above highly interesting  observations of M.  Robin need con-
firmation, and it is to be hoped that microscopic anatomists will direct
their  attention  to  the subject.  In the many examinations which I
have  made of ganglia, I have never recognised the presence of two
orders of ganglionary cells, nor have I ever perceived any attachment
between the tubes and cells.   I  would remark, however, that I have
made no examination of the ganglia and  their constituent cells since
the publication of the researches of M. Robin.  There is one defect
in the abstract of the author,  of which we have  given  a somewhat
literal  translation, viz :  that the distinctive  characters of  the  two
orders of ganglionary cells are not recited:  it will be observed, also,
that no mention is made of their occurrence in either the  brain or
spinal cord: from this I should judge that M. Robin was not acquainted
with the delicate cells described by me in Part X.  of this work, as
existing in vast numbers in the white substance of the cerebrum, cere-
bellum, spinal cord, and nerves of special sense wherever this occurs. 
394
THE  SOLIDS.
                                NERVES.
  [The examination of the nerves is  best conducted by cutting thin slices
with a very sharp  scalpel, or flat-bladed knife, in different directions, and
subjecting these to moderate pressure,  having previously moistened them with
water  or  with serum.   Other  sections may  be  gently dissected  with  fine
needles, and the fibrillae separated.   In all instances, the sooner the nerves
are examined  after death, the more readily will their structure be determined.
  Hints  have already been given  for  viewing the neurilemma, the white
substance of Schwann, and the  "axis  cylinder" of Rosenthal and Purkinge,
and the localities pointed out in which the Pacinian bodies are found.
  Dr.  Stilling*  gives  the following instructions  for examining the spinal
cord :
  "I place a fresh spinal cord, and medulla oblongata, as they are taken  from  the
body, in weak spirit, and allow them to remain in it twenty-four hours; then I pour
off the  spirit, and  place fresh  but  stronger spirit on the  parts, which, after two or
three days, is again poured off, and then the strongest rectified  spirit is used;  the
specimens  being allowed to remain in it from four to eight days, acquire by degrees
such hardness as to allow of the finest sections  being made.  The sections being
provided (if from a recent cord), are then to be  extended by means of a compres-
sorium.  Low  powers are  best adapted for the examination;  a lens of two-inch
focus being first used, and then others of higher power."

  He  directs the sections to be  made  with a sharp and broad razor, the sur-
face of which must  be kept moistened with the spirits of wine.
  Preparations of nerves can only be preserved in fluid; for this  purpose,
the naphtha-water, chromic acid, or Goadby's B-solution may be employed.]
* Lancet, Oct. 7th, 1843. 
ORGANS OF  RESPIRATION.
395
            ART. XX. —ORGANS  OF  RESPIRATION.

   The organs of respiration  seem  to stand alone in  the  animal
 economy, and not to exhibit  any strong structural relationship or
 affinity with any other organ or organs comprised  in that economy.
 In  their position and general  form they bear some resemblance, in
 the mammalia at least, to glands: this resemblance, however, is more
 apparent  than real, as becomes evident from the single  consideration
 that the lungs are essentially destitute- of the innumerable granular
 cells which constitute the chief bulk of true glands, and form  their
 distinctive and essential element.   In a strictly natural  arrangement,
 the lungs would be more properly and correctly described in connexion
 with the circulatory apparatus;  for essentially they are vascular organs,
 their  only indispensable constituent being blood-vessels, so situated,
 indeed, as to admit  of their being brought  continually into contact
 either with air, or with water impregnated with air.
   The great object aimed at in the formation of the lungs  of mam-
 malia  is  the  construction of  organs which  shall  occupy but  little
 comparative space, and  which shall  yet present a greatly  extended
 surface, throughout which  the blood and air may be  brought  into
 close  approximation.   We shall now proceed to describe the manner
 in which this  purpose is accomplished.
   The tissue of the lungs of man and other mammalia may be divided
 into two systems of apparatus: the first comprises  the circulatory or
 vascular apparatus, consisting of arteries and veins, together with the
 plexuses formed by the union of the capillaries proceeding from both
 sets of vessels;  the  second  comprises  the respiratory  or aeriferous
 system, which includes  the bronchial  tubes, the  air cells, and  the
 ciliated epithelium.  The intimate structure  of the lungs will be best
 understood  by an examination in' the first  place  of the aeriferous
 apparatus.
                        AERIFEROUS APPARATUS.
  The  aeriferous apparatus  of the lungs consists of bronchial tubes
 and air cells.
  Bronchial Tubes.—The bronchial tubes are formed of cartilaginous
rings  united by elastic tissue:  the rings, however, are imperfect,  and
 are only present in the larger tubes, as those  of the first, second,  and
 third or fourth diameters: in the smaller tubes they are  absent, these
being composed entirely of a nucleated form of fibro-elastic  tissue: 
396
THE  SOLIDS.
they divide repeatedly in a dichotomous manner: it is not easy, how-
ever, to determine the number of divisions which each bronchial tube
undergoes  after its entrance into each lobule;  it would appear, how-
ever, that  the intra-lobular ramifications are less numerous than the
inter-lobular  branchings, the bulk of the lobule consisting chiefly of
air cells.
   The bronchial tubes are lined throughout by mucous membrane,
which  is invested by  a stratum of cylinder ciliated  epithelium.  The
smaller bronchial tubes are eminently elastic and  contractile,  by
virtue  principally of the elastic  tissue of which  they  are  chiefly
formed.  This elasticity is still further  increased in the case  of the
larger tubes by the presence of muscular fibrillae of the unstriped kind.
   Air  Cells.—The air cells are minute  cavities of variable size, of an
angular form, not dilated, which communicate freely with each other,
and the parietes  of which are formed of a diaphanous, tough,  highly
elastic  and delicately  fibrous membrane, which contains and supports
the capillary blood-vessels, and the interior of which is lined by a modi-
fied mucous membrane also invested with a layer of ciliated epithelium.
   From this description, it becomes evident that the air cells contain
the same structural elements as the smaller bronchial tubes themselves,
and that they therefore differ from these solely in form and arrange-
ment, possessing precisely the same general physical properties, being
in the same manner highly elastic, a property mainly dependent upon
the abundance of fibro-elastic  tissue  present in the  lungs.    (See
Plates  XLVII. and XLVIII.)
   That the air cells do really communicate freely with each other (a
fact which is now generally admitted, but which  is  yet denied  by
Dr. T.  Williams*) may be satisfactorily determined in  many  ways.
Thus, it is  by no means difficult  to see  the circular and ever  patent
openings of communication, both  in injected  and uninjected  lungs;
again,  by  injection  with size, perfect casts  of the  cells may  be
obtained:  these casts, when a fragment of lung is  torn up in  water,
readily escape, by which means  the variety presented by the cells in
form and magnitude  may be accurately determined,  as well  as the
shape and  number of the openings of communication.  (See Plate
XLVIII. fig.  2.)  Not unfrequently these casts  are  more or  less
coated with the epithelium lining the cells,  as also represented  in the
figure just referred to.
  * "Essay on  the Structure and Functions of the Lungs."   College of Surgeons
London, 1842. 
ORGANS OF  RESPIRATION.
397
   So perfect and consistent are the models of the air cells procured
in this way, that for some  time I was  led  to  entertain the idea that
each little mass of size was really enclosed  in a delicate and structure-
less membrane, which I conceived to be the true air cell lining, and I
have scarcely yet been able to discard the notion altogether from my
mind.   If the  lung be injected with tallow, we do not procure casts
in the same number and perfection, because the  tallow adheres closely
to the sides of the air cells.  Sometimes I  have  seen casts even with-
out injection; but the occurrence of these  is rare.  It is, therefore, yet
possible that  I have not been deceived, and that a structureless mem-
brane does really line the air cells, a modification of the mucous lining
of the tubes,  the "basement membrane" of Bowman.
   It would appear from an examination of these casts, that the num-
ber of openings of communication  varies  from one to five;  usually,
however, but one, two, or  three, are present.
   When  looking attentively  at these  casts,  covered with epithelial
cells, and  labouring under the impression that they were really distinct
structures, I  have sometimes perceived cells  of glandular epithelium,
one much larger than the rest, with a transparent border; and this I
fancied was a fresh cell membrane in process of development.
   The presence of epithelial scales in the  air cells was first observed
by Mr.  Addison;*  but that  gentleman  was  unable  to determine
whether  these were  ciliated  or  not; subsequently Mr. Raineyf
advanced the statement that healthy air cells contain no epithelium.
In sections of recent lungs, it is a very  easy  matter not merely to
determine the existence of epithelium in  the air cells, but  also the
fact of its cylinder and ciliated form and character.  Circular  and
oval epithelial cells also occur; these are most probably ciliated cells
in a  less advanced condition  of development.   (See Plate XLVIII.
fig. 3. and Plate XLIX. fig. 2.)
   It has been stated that the air cells vary in size.   This is the case
with even contiguous  cells, as may be seen by a reference  to the
figures: the air cells  in the lungs  of an adult are also much larger
than those of a child.
   The fact of the epithelium extending from  the bronchial tubes into
the air cells, would seem in itself to imply that the mucous membrane
  ♦"Observations on the Anatomy of the Lungs," by Thomas Addison, M. D., 1841.
—Transactions, Mcdico-Chirurgic Society.
  f'On the Minute Structure of the Lungs, and on the Formation of Pulmonary
Tubercle," by George Rainey.—Transactions, Medico- Chirurgic Society, 1845. 
398
THE  SOLIDS.
also lined them, at least in a modified condition, which is contrary to
the opinion expressed by Mr. Rainey.

                        VASCULAR  APPARATUS.
   The vascular apparatus of the lungs consists of arteries and veins:
these vessels, after numerous ramifications in the inter-lobular spaces,
unite together on the surface of the air cells,  through the medium of
a  beautiful  and elaborate  system of plexuses,  each air cell  being
furnished with its own separate plexus.
   The manner in which the vessels, either arteries or veins, are dis-
tributed  throughout each lobule is as follows:—first, large branches,
after having  reached the lobule  through  the inter-lobular spaces,
extend over an area of several cells (see  Plate XLVII. fig. 2);  from
these, secondly,  a  number of smaller vessels proceed, which  run in
the spaces between  the  cells, forming loops  around them (see Plate
XLVII. fig. 3); third and  last, from these inter-cellular vessels the
capillaries constituting the plexuses are given off.   (See Plate XLIX.
fig. 3.)   This distribution  of the  vessels is especially evident on the
pleural surface of the lung.
   From  the preceding description it does not appear that the capillary
plexus belonging to each air cell  is compounded of both venous and
arterial capillaries,  but that in most cases it consists entirely of capil-
laries derived exclusively either from a vein or an artery.
   It is thus evident that an air cell with  its investing plexus of capil-
laries  contains  all  the essential constituents of an entire lung, and
therefore that each air cell may be regarded as a lung in miniature.
   It is well known that  it  is frequently a matter of great moment, in
a medico legal respect, to discriminate between a lung naturallv
inflated  and one  artificially  so:  the test  proposed,  and  ordinarilv
employed and relied upon, seems  to me to be unworthy  of full confi-
dence.   I  allude to  the hydrostatic test: it  is  stated that, by  firm
pressure, all the air contained in a portion of lung artificially inflated
may be expressed,  so that it will sink in water;  but that this cannot
be done in  the case of a lung naturally inflated;  a portion of air will
always remain unexpressed sufficient to keep  it afloat.   I see no good
reason for this constant difference, since it is perfectly certain that a
lung may be most  completely  and entirely injected  with air or fluid,
far more completely, I should be inclined to say, than occurs with air
naturally inspired,  except perhaps during a forced inspiration.   Not-
 withstanding the  uncertainty  which seems to me to be attached to 
                 ORGANS  OF  RESPIRATION.              399

this test, I yet consider that by a careful examination of the condition
of the blood vessels in the two lungs, the  question may in most cases
be satisfactorily determined, whether has the lung been artificially or
naturally extended with air ?
  Previous  to birth, it is known that the circulation of blood through
the lungs is of a very limited character, and that it is'only after that
period, and  during the first act or acts of respiration that the great
mass of  vessels, principally capillaries, become carriers of blood.
  The vessels, then,  in the one case, viz: before respiration, will be
almost devoid of blood, and, in the other, after that act, replete with
that fluid.
  Dependent  upon this difference in the  condition of the vessels, we
shall notice certain  distinctive features,  both general and micro-
scopical, in the case of the artificially and the naturally inflated lung.
The former, after inflation, will be observed to collapse to nearly its
previous size  on the  escape of the air: it will present a pale appear-
ance, especially evident if the lung be cut into, and when examined
with a lens, it will be seen that the inter-spaces between the lobules
and cells are  pale, not being occupied with red vessels.  Now, on the
other hand, the latter will be  characterized by appearances the very
reverse: it, after inflation, will not collapse to nearly its previous  size;
it will be somewhat  red, and  the intervals between the lobules and
cells will be seen  to  contain red vessels, in which, as well as in the
capillaries, the higher powers of the microscope will reveal the exist-
ence of red-blood discs.

                              PATHOLOGY.
  Now that the normal anatomy of the lungs is well understood, the
several pathological  conditions of those  organs  admit of a precise
and satisfactory explanation.  The principal  diseases of the lungs,
upon the exact nature  and  seat  of which the microscope affords,
directly  or indirectly,  satisfactory information,  are Emphysema,
Asthma, Pulmonary Apoplexy, Pneumonia, and Tubercle.
  Emphysema.—The essential pathological and microscopical char-
acters of Emphysema consist in an enlargement and rupture  of  a
greater or less number of air cells, whereby the cavities of several
distinct cells become  thrown into one, with sometimes the escape of
air  from the ruptured air cells into the  inter-lobular cellular tissue.
When  the  air  cells  are simply dilated  and ruptured, without any
escape of  air from them, the Emphysema is lobular; when, on the 
400
THE  SOLIDS.
contrary, the air passes from  the  cells into the cellular tissue, which
unites the lobules to each other, the Emphysema is termed inter-lobular.
It cannot be doubted but that this condition of the lungs interferes
very greatly with the efficiency of these organs;  the extent of surface
over which the air and blood are brought into contact being very
considerably diminished.
   Asthma.—The microscope has revealed the fact that the smaller
bronchial tubes and air cells are principally constituted of a form of
elastic tissue, which, possessing  marked physical properties, is yet, to
a certain extent, under the control of the  nervous system.  It is then
the irregular action and contraction of this tissue, determined partly
by physical causes and partly by irregular and unequal  impressions
arising from internal causes conveyed to this tissue  by the nerves,
which occasion and account for  the distressing and peculiar symptoms
of Asthma.
   Pulmonary  Apoplexy.—Pulmonary apoplexy is  simply a highly
congested condition of the vessels, which are principally capillary,
of the  lungs.   A congested  vessel is of greater  diameter than an
uncongested one, and,  therefore, is capable of containing, and really
does  contain, a far larger quantity of blood than the vessel in its
normal state.   There  are many stages or degrees of congestion and
of pulmonary apoplexy: the congestion may  be slight, may  engage
only one lung or a portion  of one; the dilatation of the vessels mav
be but trifling, and therefore the  increased quantity of blood conveyed
by them will be but small; or, on the other hand, the congestion mav
be very great, both lungs may be affected, and the dilatation of the
vessels may be considerable; the quantity of blood also contained in
such vessels will be very great.  In cases  of trivial or partial conges-
tion, a slight retardation in the progress of the blood only occurs; in
the more severe and  complete  cases, the blood accumulates in the
vessels to such  an extent as that the circulation is totally annihilated,
death being the necessary result  of such a condition of things.
   In what way may the occurrence of this congestion  be explained.
and what is the cause of the cessation  of  the circulation?  The cap-
illary vessels of the lungs are, of course, incapable of coveying beyond
a certain quantity of blood: any causes, therefore, and there are sev-
eral, which drive in upon the lungs a greater amount of the vital fluid
than its vessels  are capable of circulating, would produce congestion:
the first effect of which is  an accumulation of blood in the vessels;
the second, an enlargement  of those vessels, the coats  of which are 
ORGANS OF  RESPIRATION.
401
 highly elastic, as a necessary consequence of the first; third, a total
 cessation of the circulation, arising from the rapid aggregation of the
 blood corpuscles in the vessels.  The various degrees of congestion
 may be followed out with the microscope in the most  satisfactory
 manner in  the  tongue of the frog, or in the web of the  feet of that
 creature.  Some  of  the  vessels will  be  but slightly dilated;  other
 capillaries, which in their normal state are capable of conveying only
 a single row of corpuscles, will now be observed to contain two or
 three rows; in others, again, the blood will have ceased to move
 altogether.
   These several changes in the condition of the blood and its vessels
 during  congestion, are all unaccompanied by structural alterations, by
 which character congestion may be distinguished from inflammation.
   Pneumonia.—The phenomena of congestion precede those of pneu-
 monia,  of which indeed it may be considered as the first stage; the
 second stage of pneumonia, consists in the rupture of some  of the
 capillary vessels, and the escape of a portion of their contents (whence
 proceeds the characteristic rust-coloured expectoration), as well as the
 effusion without rupture of coagulable lymph through the walls of the
 vessels, the consolidation of which in the air cells constitutes the con-
 dition of the lung known by the name of hepatization: these results
 are probably necessary consequences of the protracted  congestion:
 the third stage of pneumonia  is attended by the formation and excre-
 tion of granular cells in large  quantities, imbedded in a fibrinous fluid:
 the excreted matter may be either mucus, constituting the stage of
 resolution, or it  may be pus, when the pneumonia is  said to terminate
 in purulent infiltration: the difference between the two excretions is
 one of degree rather than of kind.   With respect to the  nature and
 origin of the granular corpuscles, some physiologists will  have it that
 they are the white corpuscles  of the blood escaped from the vessels—
 an  opinion completely untenable:  they  doubtless  have an  origin
 external to the blood vessels, and are to be regarded as of an epithelial
 character, representing as a rule the peculiar epithelium of the surfaces
 or parts from which they emanate.
  Tubercle.—The  earlier  microscopic  observers  approached the
 investigation of  tubercle,  especially of tubercle in the lungs, with the
expectation of  finding in tubercular matter some peculiar element
or structure which should account for the fatality and apparent malig-
 nity of  that fearful affection, not knowing fully the true structure of
 the organs  of respiration, and therefore not perceiving clearly that this 
402
THE  SOLIDS.
fatality is occasioned rather by the peculiar structure of the lungs
themselves, than by any malignity in the character of the  tuberculous
formation.   Some of these observers have even fancied that they have
discovered in the matter of tubercle peculiar and characteristic cells:
it is now scarcely necessary  to remark, that careful and  extended
microscopic investigation does not warrant any such conclusion.
  One of the  most accurate views with  which  I am  acquainted
respecting the nature of tubercle, is that put forth by Dr. Addison:*

  "Tubercles of the lungs,"  he writes, "are  composed of objects
originating from blood corpuscles, which have been  arrested in their
circulation through the minute vessels of the structure of  the air cells.
So  long  as  this retardation is confined to  the  colourless corpuscles,
the morbid  actions  which ensue  are  strictly those  of an  abnormal
nutrition, and various forms of imperfect and degenerated epithelium
are the results; but if it extend, so as to interfere with the  free cir-
culation  of the red corpuscles, we  then have all  the phenomena of
inflammation.  No new elementary particles are formed to constitute
a tubercle, and although from the insidious nature of the primary
actions, from the delicacy of the structure, and the important charac-
ter of the function of the lungs, the treatment of  tubercular diseases
must always be  attended with more  than common difficulties, still
there is every reason to believe that they are susceptible of prevention
and cure, especially  if our efforts for the attainment of these ends be
enforced previous to the appearance of a cough, which is not a con-
comitant of the first stages of  tubercular deposition in the lungs."

   My own views of the nature of  tubercle  in the lungs differ in one
important respect from those of Dr. Addison; that is, with reference
to the precise origin of the imperfect and degenerated epithelial cells.
Dr. Addison conceives that they are  derived immediately from the
blood itself, while I consider that they proceed from the epithelium,
which has been described as lining the  air cells themselves.
   A tubercle, then, I would define as  an accumulation  of epithelial
scales, the  imperfect  and  degenerate  representatives   of  the true
epithelial cells of the organ or part in which  the  tubercle is itself
developed.

  * "Experimental Researches."—Transactions of Provincial Medical and Surgical
Association, vol. xi pp. 287, 288. 
                 ORGANS  OF  RESPIRATION.             403

  A tubercle of the lungs, at the earliest period of its formation, is
exceedingly small, occupying a single cell only; when this cell becomes
filled with tubercular matter, a rupture of its membrane occurs, and
thus the extension of the tubercle takes place from  cell to cell; this
extension at the same time being accompanied  by a destruction and
displacement of numerous of the capillary plexuses.
  After the  above  description, it  need scarcely be observed  that
tubercles of the lungs are not vascular. 
404
THE  SOLIDS.
                                  LUNGS.
   [The presence or absence of epithelium in the air-cells of the lungs is a
point of considerable importance, since Dr.  Hassall  defines tubercle to be an
accumulation of degenerate epithelial scales in the air-cells;  a definition
that would possess little value if no epithelium was there present.
   Since the paper by Mr. Rainey, in  1845, referred to in the text, in which
he contended that the air-cells were not furnished with epithelium, the same
gentleman  has extended his inquiries to the lungs of inferior animals, and
he here finds in several instances demonstrative proof of the non-existence
of epithelium.   His paper* thus refers to the opinion of those who still main-
tain "that the air-cells are lined with ciliated  epithelium."

   " The demonstration of this  supposed fact has been attempted by filling  the air-
passages with tallow or size, and then submitting the lung thus treated, and the casts
taken from the air-cells, to examination with the microscope.  I may observe that
all the ramifications of the bronchial tubes have a very complete lining of ciliated
epithelium, which, by such a mode of preparation, might have been easily detached,
and broken up, and fragments of it forced into  the air-cells;  hence, such a mode of
procedure seems ill calculated to determine a point of so much delicacy.  I am ready
to admit that corpuscles of various kinds may occasionally be found in the air-cells,
but these have not the most remote resemblance, either in their quantity or manner
of arrangement, to a lining of epithelium, especially of  that kind which is called
ciliated epithelium.  Mr. Addison was the first who described an epithelium, lining
the air-cells, which he  states to be in the form of round nucleated scales, with from
one to fifteen or more nuclei observable in a single  scale."—(Philosophical Transac-
tions, 1842, Part ii. p.  162.)
   "It is very evident from this description that Mr.  Addison must have mistaken the
nuclei in the coat of the capillaries for an  epithelium, an error which it is very easy
to commit, in examining the uninjected lungs, and which error can only be cor-
rected by comparing the lungs uninjected with  those in which the capillaries have
been filled with injection.   I have frequently seen  the curve formed by a capillary
projecting beyond the free border of the pulmonary membrane, where it forms a
communication with an adjoining cell, presenting so much the appearance of a delicate
epithelium, that, had I not more than once  seen  a vessel in a similar situation in the
injected lung, I might have mistaken it for a portion of epithelium, lining an  air-cell,
and considered that the air-cells have a lining,  if not of ciliated, yet of pavement
epithelium, as some anatomists of the present day imagine."

   Mr. Rainey describes the bronchial tubes of birds to  be lined with ciliated
epithelium, as in mammals.   The air-cells he found to be so infinitely small,
that it is impossible for them to be lined with epithelium, as he found upon
measurement that the epithelial scales from the  bronchus of a pio-eon were
87o of an inch in length, and  ¥?Vo  of an  inch  in  breadth, while the  air-
* Medico-Chir.  Transactions, 1849. 
ORGANS  OF  RESPIRATION.
405
cells, or air-spaces, on  an average, measured only -ggVo 0I" an mcn  m
diameter, and some were even smaller.
  He also observed  that in the  kangaroo many of the air-cells were  so
minute,  that a single cell of epithelium would have entirely filled them, and
that in the  rat  and mouse, in which the ciliated epithelium is  of the same
size as in man, many of the air-cells were too small to receive an individual
particle.
  Mr. Rainey considers  that the essential and  only true organs of respira-
tion, or  rather of the  aeration of the blood, are the pulmonary capillaries,
with the blood in them.
  Quain and Sharpey* believe the air-cells to  be  lined with delicate, thin,
transparent mucous membrane, covered with a  stratum of squamous epithe-
lium.  This membrane, by a doubling inwards of itself, forms the intervening
septa.
                           MANIPULATION.
  In  addition to  the  methods already pointed out for the study of the air-
cells, the lung may be artificially  inflated, and  then allowed  to dry.  Thin
sections of the dried lung may then be made, and the size, shape, and num-
ber of air-cells  readily examined.   The  capillaries can only be viewed  by
injecting them; this  may be done by either the  pulmonary artery or vein.
In the fcetal subject, the lungs, with the rest of the organs, may be injected
from  the umbilical vein.
  Rossignol's experience in the injecting of the  capillaries of the lungs is
worth here recording.  He found  that injections  by the bronchial arteries
returned by both  the  pulmonary and  bronchial veins,  but  not by the
pulmonary artery.
  2dly. That the injections by the pulmonary  arteries returned entirely  by
the  pulmonary  veins, but not by the bronchial arteries;  and 3dly, that  by
injecting the pulmonary veins it was  easy to fill all the other vessels; viz:
the  pulmonary artery and bronchial arteries and veins.
  Portions of injected lung  are best preserved in fluid.  They should be
mounted in cells, just deep enough to allow the cover to be applied without
coming  in contact with  the  object, as it is necessary sometimes to change
the  focus of the object-glass so as  to  penetrate  to the bottom of an air-cell;
the  fluid may be either spirit and water, naphtha, or Goadby's B-solution.
  Some Injected  lungs show well when mounted in the dry way.

  Plate  LXXIII., fig. 2, shows capillaries and air-cells of the fcetal lung.
     «     "     fig. 3,  do. of an infant.
     «     "     fig. 4,  do. of an adult.
     "     «     fig. 5,  Bronchial laminae of an eel.]

        * "Quain's Anatomy," by  Sharpey and Quain, 5th edition, p. 1153. 
406
THE  SOLIDS.
                     ART.  XXL —GLANDS.

   Much uncertainty has until  recently prevailed as to what really
 constitutes a gland:  some have  considered those only as true glands
 which are furnished with distinct openings or excretory ducts; others
 again have regarded those organs only as glands which  give forth a
 secretion: the former view  of  a  gland  would exclude  the  vascular
 glands as well as some others, and the latter, although it would include
 these,  and, doubtless,  also every other glandular structure, is not a
 sufficiently obvious or structural character, the secreted product of
 glands in many cases being furnished in  small and scarcely apprecia-
 ble quantities, and which again  are immediately, on  their  formation,
 absorbed, in some cases, into the circulation.  Again, secretions are
 supplied by parts and extended  surfaces  to which, although  they are
 essentially glandular, the term gland would scarcely be applicable; of
 this nature are the free surfaces of all  membranes covered  by epithe-
 lium, as the mucous, serous, synovial, &c.
   We have still then to inquire,  first, what are the essential structural
 elements of which all glandular  organs or parts are constituted? and,
 second, what is the exact definition to  be given of a gland ?
   The researches of modern microscopists have  indisputably proved
 the fact, that the only essential elements  of a secreting structure are
granular cells and  a  circulating fiuid,  the secreted product being
formed out of the latter by the vital endowments resident in the former.
   According to this definition,  the blood itself is to  a  considerable
extent glandular, inasmuch as it contains a vast number of granular
 cells to which the elaboration of the fibrin  is, in  all  probability, due.
   Again, the free surfaces of all membranes  are  glandular;  the epi-
thelium covering them constituting the one essential glandular element:
the varieties in the size and form of the cells representing this epithe-
lium have been already described in a  former chapter of this work.
   Following up this  general definition of glandular structure, a gland
may be defined as a  collection or aggregation of granular cells placed
in close  approximation with  a formative fluid, contained, ordinarily,
but not essentially, in the blood-vessels.
   This definition of a gland embraces not merely those glands which
are provided  with orifices  or excretory ducts, but also those which 
GLANDS.
407
have  no such external  or apparent channels  of excretion,  as  the
vascular and other glands.
  While it is certain that secretion takes place in the cavities of the
granular cells, as  may  be actually shown  to occur in  the hepatic,
renal and sebaceous cells, there is much reason to believe, from the
rapid and continual development and dissolution of successive genera-
tions  of cells, as especially  evident  in the case  of those  of  the
stomach and small intestines,  that this secretion is liberated in many
instances only by the dissolution of cells themselves.   From this view
of  the  relation existing between the  secretion and  the cells, it
would  appear that  the  secretive process  is accompanied  by an
endosmotic  action.
  In  the case of fat  cells, the secretion is rarely eliminated,  the
secretive process  is exceedingly slow, and the oleaginous matter is
stored up and retained within the cavities of the cells themselves, the
growth of the cell membrane  keeping  pace with the increase in the
amount of its fatty contents.
  The  idea of fluidity is  almost inseparably  connected wuh  our
notions of a secretion;  secretions, however, are not essentially fluid,
for there are solid secretions  as well as  fluid; the sebaceous matter
of the glands of the prepuce is a solid, and the urine of many ser-
pents, as the  boa, is also stated to be solid.  There is little doubt,
however, but that most and perhaps all secretions are fluid during the
act of their formation, and that the solidity acquired by certain of
them occurs after their perfection and  elimination.
  In a strictly systematic arrangement of structures, the majority of
the glands might  well  be  described in connexion with  the internal
and external integuments  of  the body,  the  skin, and mucous mem-
brane, since in very  many glands, the secreting structure is contained
within, but most probably not developed from inverted  processes of
these  tissues.   Such an arrangement  of the glands, although a very
natural  one as far as  it goes, would yet not embrace all the glands;
the  vascular and some  others would be excluded from it.
  The proof of the  position that very many glands,  and even  the
most complex ones,  are contained in  offsets  of the various modifica-
tions  of mucous  membrane and outer integument,  observers have
stated  to be  derived  from an  examination of these  organs in an
embryonic condition, when even, it has been affirmed, the most elab-
orate  and varied  of them may be seen  as  simple follicles cr sacs,
springing from the general membrane covering the skin or lining the
internal cavities. 
408
THE  SOLIDS.
   It would appear, however, from recent and  trustworthy observa-
 tions,  that the principal glandular organs of the body have each  a
 separate  development, and that  it is only after they have been more
 or less completely formed that they become  attached to the surface
 of the skin or mucous membrane, upon which their  secretions  are
 poured.
   Numerous  divisions  of glands  have been proposed by different
 writers: the majority of  these do not require  any special notice:
 there  is one,  however, originating with  Mr. Goodsir, which would
 appear to be ingenious and philosophical, which deserves especial
 mention.   That gentleman divides glands into two types or classes;
 the distinctions existing between which are founded upon observations
 derived from the study of  the early development of these organs.
   In the first  type of glandular structure, the follicles which are at
 first  distinct from the excretory duct, but which  subsequently become
 united with it, are regarded  as parent  cells, the granular cells con-
 tained  within them being secondary formations, which are continually
 in process  of development, springing from a  germinal spot situated
 either  at the bottom of the follicle, if this be short, or over its entire
 surface,  if the follicle  be tubular: in this  class, the  follicle is  a
 permanent structure.
   In the second  type, the follicle is also a parent cell, but is not a
 permanent structure;  and having attained  its  maturity,  it bursts,
 discharges the secondary cells contained within it, and finally shrivels
 up, its  place being  supplied by other similarly organized cells.
   In this type, but one gland  is included—the testis.
   The   arrangement of glands proposed  below,  in  a tabular form,
would  appear to be one of the least objectionable, as well as the most
practical for purposes  of description:


               CLASSIFICATION  OF  GLANDS.

                      o. UNI-LOCULAR GLANDS.
     Follicles.                        Solitary Glands.
     Stomach Tubes.                 Aggregated Glands.

                     b.  MULTI-LOCULAR GLANDS.
     Sebaceous Glands.               Mucous Glands.
     Meibomian Glands.              Labial  Glands. 
GLANDS.
409
     Glands of Hair Follicles.        Buccal Glands.
     Caruncula Lachrymalis.         Gingival Glands.
     Glands of Nipple.               Lingual Glands.
     Glands of Prepuce.              Tonsellitic Glands.
                                     Stomach Glands.
                                     Tracheal Glands.
                                     Vaginal Glands.
                                     Uterine Glands.
                        e. LOBULAR GLANDS.
     Salivary Glands.                 Mammary Glands.
     Pancreas.                       Liver.
     Parotid Glands.                 Prostate Gland.
     Submaxillary Glands.            Cowper's Glands.
     Lachrymal Glands.
                        d. TUBULAR GLANDS.
     Brunner's Glands.                Ceruminous Glands.
     Sudoriferous  Glands.             Kidneys.
     Axillary Glands.                 Testes.
                      e. GANGLIONARY GLANDS.
           COMPOUND.                       SIMPLE.
 Brain and Cerebellum.           Ganglia of Encephalic Nerves.
 Medulla Oblongata & Spinal Cord. Ganglia of Sympathetic Nerves.
                       /. ABSORBENT GLANDS.
     Lacteal Glands.                  Lymphatic Glands.
                       g. VASCULAR GLANDS.
     Spleen.                          Thyroid.
     Supra-renal Capsules.             Pituitary Body.
     Thymus.                        Pineal Gland.
                     h. GERM-BEARING GLANDS.
                            Ovaries.

  It is doubtful whether the  glands admit of any strictly natural and
at the same  time convenient classification.   The more simple glands
pass by almost insensible gradations into the more complex, thus
leaving but few salient points available for purposes of division.  The
separation of the multi-locular from the lobular glands is to a great 
410
THE  SOLIDS.
extent arbitrary, and is adopted simply from its convenience.  Per-
haps the best division which could be proposed of those glands which
are provided with excretory ducts or openings, is into follicular and
tubular glands.
  It is very probable that one of the  organs introduced into the
division of lobular  glands, viz: the liver, will  hereafter have  to be
removed from that division and placed  by itself near to the vascular
glands, should some recent researches in reference to the termination
of the biliary ducts be confirmed.
  It is also  probable  that further research will disclose the fact that
certain of those glands arranged as mucous glands do not all possess
precisely the same structure.

                     UNI-LOCULAE GLANDS.
                             FOLLICLES.
  Crypts and follicles are inverted, and sometimes tubular prolonga-
tions of one variety of mucous membrane, termed compound, and to
which that of the alimentary canal, the gall-bladder, the uterus and
the Fallopian tubes  belong.
  In the stomach and  in  the large  intestines  these follicles are so
closely set in the membrane, that,  from  the mutual compression  exer-
cised upon each other, they assume a more or less angular figure; in
the small intestines there are fewer follicles, in consequence of the
great number of villi  present in these, and they are  not angular, but
round.  These follicles, which, in the small intestines, are called the
follicles of Lieburkiihn, are met with under two very different condi-
tions; in each of which they present a very distinct appearance, being
in the  one case—that is, in their  perfect state—lined by epithelium,
and  in the  other being destitute  of this epithelium.   (See  Plate L.
figs. 1. 6.)
  The epithelium lining the follicles of  the alimentary canal, is of the
same kind as that which covers  the inter-spaces between the follicles,
and is  of the conoidal variety.  It lines  the entire follicle with a beau-
tifully regular layer of united epithelial scales, which are so large that
they nearly fill up the cavities of the follicles, a small circular channel
only being visible in each:  this is  usually occupied  by the mucus
secreted by the cells, and appears at the mouth of each follicle as a
mere depression, surrounded by a  circle of radiating epithelial scales.
  To see the epithelium in the follicles of the  human stomach, and
even to see  the follicles in the mucous membrane of this organ at all, 
                            GLANDS.                        411

requires that it should be examined immediately after  death, as the
lapse of a few hours is sufficient to allow of the action of the gastric
juice to such an extent as to dissolve the follicles entirely.
  The follicles dip into the thickness of the mucous  membrane to a
variable extent in  the small and  large intestines;  their  extremities
reach nearly to the sub-mucous cellular tissue, and in the lower part
of the rectum  they are much  elongated, and continued for some
distance into the sub-mucous fibrous tissue between the mucous and
muscular coats; the follicles  usually terminate in rounded and some-
times even in dilated and bifurcated extremities.  (Plate L.fig.  7.)
  The  object attained by these innumerable  follicular  inversions of
the mucous membrane of the stomach and intestines is obvious, viz:
a greatly extended surface for secretion.
  The  mucus with which the intestinal canal is so abundantly pro-
vided, is chiefly secreted by the epithelium contained in these follicles.
  Todd and Bowman thus describe the epithelium of the  stomach cells
m the  "Physiological Anatomy:" "They [the epithelial particles]
seem to lie in a double series, the  deeper being in course  of develop-
ment, 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 enclosed, and that at a subsequent period
the granular contents escape at the free extremity by a dehiscence or
opening of the wall, at that part, having the  transparent husk with its
nucleus subsisting  for some time  longer.   The clear  structureless
mucus,  which is almost always found occupying the cells and cover-
ing 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, when it fills the cells, shows  that it has
oozed out from ever}* part of their wall so as gradually to fill them up."
  The ridges or spaces between the follicles of the stomach and large
intestines in the human subject are occupied with a plexus of vessels
larger than capillaries (see Plate LI. fig. 1);  these are situated on the
deep surface of the basement membrane, while the epithelial scales
are  upon its superficial surface: in the cat, and many other animals,
the  inter-follicular spaces, instead  of being occupied by  a plexus of
vessels,  contain only a single  vessel, which freely inosculates with the
neighbouring vessels, thus mapping out the spaces between the follicles
into somewhat irregular  hexagons.  (See Plate LI. fig. 2.) 
412                      THE SOLIDS

                          STOMACH TUBES.
  The tubes of the stomach are prolongations of the basement mucous
membrane lining the follicles of that organ.   (See Plate L.figs. 3,4, 5.)
  These tubes take a parallel course, end in irregularly-dilated extrem-
ities, are arranged in sets of three, four, or five tubes, each of which
corresponds with a follicle, and represents the number of tubes which
open into that follicle:  it is only however, near their entrance into
trie follicles that they are thus parcelled out:  at their termination they
would  appear to be independent of each other, and to be separated by
equal intervals, as  represented in Plate L. fig. 3.
  The  stomach tubes,  unlike the  mucous  follicles, are filled  with
spheroidal or glandular  epithelial  cells:  these cells, however, do not
quite fill up the cavity of the tubes, but leave in the centre of each a
channel or canal, along which the  fluid secreted by the  cells flows,
until at last it reaches the follicle into which it is poured.
  The fluid secreted by these cells is, doubtless, the true solvent or
gastric fluid.
  The tubes I find to exist not merely in the stomach, to  which they
are generally described as exclusively belonging, but also in the upper
part of the duodenum, which  shows that  in the human  subject this
portion of the intestine is to be regarded as a kind of second stomach.
I have observed the occurrence of these tubes  more  than once, both
in the duodenum of man as well as of other mammalia.
  The fact  of the mucous membrane lining the  duodenum being
frequently dissolved some hours after death, in the  same manner as
that of the stomach, would in itself lead to  the inference that these
tubes were present in the upper part of that division of the aliment-
ary canal.
  Messrs. Todd  and  Bowman figure  the  tubes  as more  or  less
branched previous to their entrance into the follicles, an observation
which  I can confirm: these gentlemen also thus describe a modifica-
tion of the follicles and tubes near to 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  cells already  described, but  are prolonged into
much wider cylindrical tubes, lined with the same columnar epithelium,
and descending nearly or altogether to the deeper surface  of the com- 
GLANDS.
413
pound 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; but we have likewise found
them terminating in either flask-shaped or undilated extremities, lined
throughout with the sub-columnar variety of epithelium."
   The stomach tubes are each surrounded by a plexus of vessels.
  Sec Plate LXXIV., figs. 1—4.
                     FALLOPIAN AND  UTERINE TUBES.
   Tubes somewhat similar to those of the stomach exist, according to
the observations of Mr. Bowman,  in the mucous  membrane  of  the
Fallopian tubes and stomach.
   " The lining membrane of the Fallopian tubes,  as well as that of the
uterus, is of a compound nature, especially during gestation, and con-
sists of tubules arranged vertically to the general surface.  It is to be
observed that the cilia only clothe  the  general surface, and that  the
epithelium lining the  tubules is  spheroidal or intermediate  between
that  and  the  prismatic.  It is a  form of the  glandular variety, and
bears no cilia.*
                          SOLITARY GLANDS.
   The solitary glands  are scattered irregularly over nearly the whole
surface of the same small and  large intestines;  they vary consider-
ably in size—the larger glandulae being found principally in the lower
portion of the large intestines,  and admitting  of  easy  recognition
without the aid  of lenses;  while the smaller  glands, situated in  the
lesser  bowel, are scarcely visible,  except in states  of disease, when
their  cavities are filled with secretion.  Plate LII. fig. 6, is a drawing
of these glands, as they appeared  in a  case of muco-enterite in one
of the small intestines, while Plate LI. fig. 6, is a  representation of
them  as found in  the larger  bowel in a case  of English cholera
in a child.
  These glands are  simple  sacs or cells, filled with a fibrinous fluid.
containing imbedded in it innumerable  spheroidal and granular cells,
somewhat smaller than ordinary mucous corpuscles.
  I have  observed  these glandulae both with and without central
orifices; these have been more frequently absent  than present;  hence
it is very probable that their normal condition is  that of a closed cell,
and that when these cavities become filled with secretion, they rupture,
and thus  permit their  contents  to escape, the orifice subsequently
closing up again.
   * Cyclopedia of Anatomy and Physiology, Art. " Mucous Membrane," vol. iii. 
414
THE  SOLIDS.
  Not unfrequently, these glands in certain animals, but not generally
in man, are observed to be surrounded by a circle of short and tubu-
lar  caeca;  these by some  observers  are  regarded as  follicles of
Lieburkuhn, and it is  uncertain whether their  bases  communicate
with the cavities of the glands or not, but it is generally stated not to
communicate with the interior of the glandulae.
  The distribution of the vessels around these glands presents nothing
remarkable.

                  •     AGGREGATED  GLANDS.
  The  aggregated, agminated  or Peyer's glands,  are present in the
lower portion of the ilium only.
  They occur in patches of various sizes, each of which is made up
of a considerable number of  distinct glandulae,  having much  the
same structure, form and volume, as the solitary glands, an aggrega-
tion of  which  they may be considered to be.  These patches may be
readily recognised without  the assistance of glasses.
  In the " glandulae aggregatae," central apertures are occasionally
present, and  they are  not unfrequently surrounded  by  the  short
tubular caeca already spoken of: the inter-spaces between the gland-
ulae in the human subject are very generally covered with villi.   The
size and limits of these glands may be best determined by injection.
  When examined with glasses, as  they lie in the mucous membrane
in situ, they appear rounded  and flat, presenting many dark spots,
the nature of which is not  understood: when viewed sideways,  they
are  seen to be  really of a flask-shape, the narrow extremity of the
flask being turned towards  the surface of the mucous membrane.
(Plate LII. figs. 3, 4.)
  In inflammation of the mucous membrane of  the ilium, a frequent
concomitant of low fevers, these glands are often found to be entirely
eajen away, but sometimes they are only so far eroded as to present,
in place of closed glands, a number of open cells or follicles.


                    MULTI-LOCULAR GLANDS.

                         SEBACEOUS GLANDS.
   The sebaceous  glands  are very generally distributed  over the
surface of the body, probably not less so than the sudoriferous glands,
there being but two situations in which they are stated to be absent 
GLANDS.
415
 viz: the palms of the hands and the soles of the feet.  On all other
 surfaces of the body thS two kinds of glands are constantly associated
 together, the sudoriferous being much more numerous than the seba-
 ceous  glands.
   They are  found especially more or less deeply imbedded in those
 portions of integument which are copiously clothed with  hair, as the
 scalp,  whiskers, beard,  axilla, pubis,  scrotum, and perineum.   They
 also exist, however, in abundance in certain situations not usually
 invested with  hair, as in the  integument  of the forehead, face, and
 nose, in the meatus auditorius externus of the ear, and for a certain
 distance up the anterior openings of  the nares: those situated around
 the  nipple of  the  female are  particularly  large, while those of the
 prepuce are not  merely of considerable size, but yield  a solid and
 unctuous secretion of a peculiar and penetrating odour.
   Those glands which exist in situations which are naturally clothed
 with hair,  always open into the  hair follicles; while those present in
 parts not furnished with such a covering, yet nevertheless open into
 follicles, which, although from the absence of hairs  they cannot  be
 called hair follicles, must yet not be  regarded as essentially distinct
 from hair follicles, since they in  some cases do really contain hairs.
   As there are varieties of sebaceous matter, so are there sebaceous
 glands  which  differ structurally from each other;  thus, the cerumen
 glands of the ear present a conformation  typically distinct from  all
 other sebaceous glands, belonging to the tubular type of glands, with
 which they will be described.
   There are characters, however, in the possession of which  all
 sebaceous glands agree, save, perhaps, the cerumen glands, and these
 are in  the semi-solid nature of their secretion and in the mode of  its
 formation and elimination.
   The  secretion of the sebaceous glands, like  other secretions,  is
 formed within the cells, which are very large, and in which  it exists
 in the form of little spherical and shining particles of various sizes;
 these cells, when filled with the secreted matter, are thrown off with-
 out rupture from the glands in which they have been formed, probably
 by the development of fresh cells behind them, so that in general, the
 sebaceous  secretion consists  of an aggregation of such  eliminated
cells.  Some few of the cells, however, do  burst, and allow of the
escape of their contents.
  The sebaceous cells, like other secreting cells  in an early stage of
development, are granular and nucleated. 
416
THE  SOLIDS.
   In  the  character  of their secretion, the sebaceous  glands exhibit
considerable affinity with the mammary glands.  The  milk globules,
however,  are formed without the cells, and not within  them, as is the
case in the sebaceous glands.
   The sebaceous glands, exclusive of the  ceruminous, manifest con-
siderable variety in size, form, and arrangement.   They may be thus
arranged: first,  the  Meibomian glands;  second,  the  glands of the
Hair  Follicles, the hairs being in some cases present  in the follicles,
and in others  absent from  them; third, the  glands of  the Nipple;
fourth, the glands of the Prepuce:  and fifth, the glands of Carunculae
Lachrymales.

                       Meibomian Glands.
   The  Meibomian  glands  are  situated  on the inner  surface of the
eyelids, between the conjunctiva  and the tarsal cartilages; they are
of an elongated form, and disposed in a vertical manner.
   The number  of these  glands  in  the two eyelids is usually not less
than forty;  in one instance I counted eighteen in the upper eyelid,
and twenty-two in the lower.   Their general form and arrangement
differs somewhat in the two eyelids; thus, in the  lower, they are  of
nearly equal length, and are arranged in a parallel manner, while in
the upper they are  much longer, almost as long again, their origins
describing an arc;  and  in place  of being disposed parallelly,  they
radiate from each other.   These differences depend  upon the corres-
ponding differences in the size and form of the two eyelids.
   Each gland consists of a number of follicles or sacs  which  open
into a central canal, which pierces the conjunctival membrane at the
margin of the tarsal cartilages.  The follicles are usually filled  with
cells,  which may be seen through their walls.   These cells present a
bright and shining appearance from the oily nature of their contents.
(See Plate LIII. fig. 2.)

                    Glands of  Hair Follicles.
  The external surfaces of the body, with  few exceptions, the palms
of the hands and soles of  the feet being the principal of them, are
covered with the hair follicles, which are placed at tolerably regular
distances  from  each other,  and  the apertures  of  which  are visible
even without the aid of glasses.
  The hairs which issue from these follicles differ in character accord-
ing to their situation: those of the scalp being long  and  fine;  those of 
GLANDS.
417
 the beard, &c, short and thick;  while those clothing the general sur-
 face of the body are not merely  short, but also exceedingly slender.
   In certain situations, the hair follicles  are frequently without hairs,
 as on many parts of the  face; this, however,  is  the exception rather
 than the rule, as very fine hairs  are generally present over the entire
 surface of the face.
   It is  into these hair follicles  that  almost all, if not all, sebaceous
 glands open.
   The  sebaceous glands of the hair follicles consist of several distinct
 cells or sacculi, each of which has a separate excretory duct;  two or
 more of these ducts—there being sometimes three, four, or five—open
 into one  common duct, which last opens upon the sides of the hair
 follicles:  there are usually two, but sometimes more of these common
 ducts, and very frequently several of  the  primary excretory tubes
 open directly into the  hair follicle.  The ducts are large, and usually
 straight;  but occasionally, like those of  the  sudoriferous  glands,  they
 are slightly spiral.   (See Plate LIII. fig.  1. 3.)
   Those  sacculi which open into the hair  follicles by distinct ducts
 are  to  be regarded as separate glands.   In the hair follicles of the
 scalp, the glands are usually binary.
   The  glands  of the  hair  follicles are  not  confined  to  the external
 surfaces of the body, but are continued  for a certain distance along
 several  of the  outlets.  Thus,  they occur in the lower part of the
 anterior openings of the nares, in the  meatus  auditorius externus, in
 the palpebral conjunctiva, in the caruncula lachrymalis, in the vulva,
 and  on  the interior surface  of the prepuce.
  The  sebaceous glands vary greatly in size, being, in  certain  situ-
 ations, much larger than in others, as in the eyelids, ears,  nose, around
 the nipples, especially of the female, and on the inner surface of the
 prepuce.
  The cells contained within the ordinary sebaceous glands differ, in
 no respect, from  those of the  Meibomian glands already described.
 It is  in the hair or sebaceous follicles that the well-known  parasite, the
 Steatozoon Folliculorum, whose  economy has been so well described
 by Mr. Wilson, is found;  it being placed  in these in an inverted  posi-
 tion, the head  being turned inwards,  as  though  the animalcule had
crept into the follicles from without.   Many of the follicles frequently
contain more than one parasite.
                            27 
118
THE  SOLIDS.
                     Caruncula  Lachrymalis.
  The caruncula lachrymalis is usually described as formed of a single
large  sebaceous gland:  it is not so, however, but  is constituted of a
considerable quantity of mixed fibrous tissue and of blood-vessels, in
the midst of which  several, usually four  or five,  distinct  sebaceous
glands are imbedded.
  These glands, like other sebaceous glands, also open into follicles,
which are certainly hair follicles, although, in the human subject, they
do not usually contain hairs.   That they are really hair follicles, how-
ever, is proved by the fact that in the sheep, minute hairs do constantly
issue from them.

                        Glands  of Nipple.
  The sebaceous glands imbedded in the integument which forms the
areola around the nipple, so conspicuous  in the female, differ  from
other sebaceous glands principally in  their larger size, which allows
of their being readily perceived without the assistance of glasses.

                       Glands of Prepuce.
   The glands of the prepuce are also remarkable for their large size,
as well as for the  peculiar characters of the  secretion which  they
furnish: one of these being its semi-solid consistence; a second, its
penetrating and remarkable odour

                           MUCOUS GLANDS.
   The great agents in the secretion of mucus are the cells contained
in the follicles with which all compound  mucous membranes are
furnished;  there is, nevertheless, a description of gland very generally
distributed, differing anatomically from the follicles also called mucous,
and which is, in like manner, supposed to furnish a mucous secretion.
It is, however, very probable that as  there are structural differences
between the two, so are there differences in the nature of the secretion
elaborated by them.
   Before entering into a description of the mucous glands, it will not
be out of place to present to the reader the results of some additional
researches on the structure of mucous membranes: at a former page
of this work, it was  stated that mucous membranes may  be  divided
into simple and compound, according as they contain follicular  invo-
lutions, or are destitute of such inverted processes; and that the com- 
                            GLANDS.                       419

pound membranes were that of the alimentary canal from the cardia
downwards, of the gall-bladder, and of the uterus and Fallopian ubes,
according to Bowman.  Further observations have, however, shown
me that on the  one side  the  mucous membranes  of he mouth
(including  that which lines its roof, which  invests the tongue, and
which covers the tonsils, uvula,  and epiglottis),  of the oesophagus
down to the cardia, of the vagina and neck of the uterus, of the vesiculae
seminales, as well as the Schneiderian membrane, are also compound;
while, on the other, the mucous membranes of the Eustachian tubes, of
the trachea, and bronchial tubes, of the bladder,  and of the unimpreg-
nated uterus, and Fallopian tubes, are  simple mucous membranes.
   The follicles of the mouth are somewhat large, scattered, and mostly
simple; those of the oesophagus are  small, and not unfrequently divided
into branches near their extremities; the follicles of the vagina resem-
ble somewhat those of the oesophagus;  but are much more branched,
very many of the follicles terminating in several offsets, and becoming,
in fact, perfect multi-locular glands: the follicles of the Schneiderian
membrane  are the largest hitherto noticed, and appear to be simple
inversions of the membrane.
   It has been stated that the mucous membrane of the uterus and
Fallopian  tubes  is  simple; in which  respect there is a  difference
between  the observations of  the author and those of  Mr. Bowman.
Considerable pains have, however, been taken to arrive at the truth;
and it is conceived that  the mucous membrane  of the parts cited
affords one of the best examples which could be  given of a simple and
delicate mucous  membrane.   The  membrane covering the lips of the
uterus and  lining the orifice of that organ is, however, like that of the
vagina, follicular—the follicles in  the  latter  situation being  particu-
larly large;  and it is these follicles which yield the thick and tenacious
mucus which  usually more or less completely plugs up the uterine
orifice.
   Mucous glands occur in very many  and different localities, in sev-
eral of which they have received distinct names, taken  from the parts
or situations in which they have been  found.  Thus, we have labial,
buccal, tonsillitic, lingual, and tracheal glands; following up a similar
kind of nomenclature for these glands, we  might add to  this  list
Eustachian, palatine,pharyngial, and  bronchial glands; also, glands
of the uvula.
   In the roof of  the  mouth the mucous glands are very numerous,
forming almost one continuous glandular layer,  provided with many 
420
THE  SOLIDS.
orifices, disposed at tolerably regular distances from each other:  they
are also  numerous in the tonsils, but much less so in the  uvula:  on
the dorsum of the tongue, mucous glands  occur but very sparingly,
and mostly near the root of this organ.
  There are some few situations in which  mucous glands  have  been
described as present, in which they would appear to be entirely absent;
as on the margins of the gums, where they have  been called gingival,
in the uterus and vagina, where they have  been named  uterine and
vaginal  glands: in the stomach, also, where they  are known as the
lenticular glands, they are very frequently wanting.
  There are also certain glands which have not been generally placed
in the category of mucous glands, which, nevertheless,  are really
structurally identical with them: of this  nature, are  Brunner's and
Cowper's glands.
  From  the preceding observation,  it follows that Brunner's and
Cowper's glands should be described with  the other mucous glands:
it will, however, be seen hereafter that  the  former  present certain
resemblances to the tubular, and the latter to the lobular glands.
  Messrs. Todd and Bowman* regard the mucous glands as identical
in structure, and probably in function also,  with the salivary glands:
that  they are not  salivary glands,  however, may be  shown, first,  by
the anatomical differences which  may be pointed out as  existing
between  mucous and salivary glands,  as well  as, secondly, by the
fact that mucous glands occur in situations—as in the trachea, &c.—
where  they could serve no purpose as salivary  glands.   Mucous
glands  occur in two  forms: a simple and  compound form.  In  its
simple or simplest form, a mucous  gland consists of a single duct, in
communication, at  its origin, with a saccated membrane, each saccu-
lus of which forms an imperfect follicle.   In its compound form, it
consists  of several ducts, each of which,  at its  origin,  is in like
manner in connexion with a bunch of incomplete follicles.
  The chief anatomical characters which distinguish mucous glands
from the salivary, to which, indeed,  they bear considerable resem-
blance, depend  upon the fact that,  in the  mucous glands, the follicles
are incomplete; that is, they open into each other, and into a common
central cavity, from which the single efferent duct proceeds; while
in the salivary glands each follicle is a distinct body of a rounded or
oval  form, and provided with a small primary efferent duct.
  Independent of the important differences indicated in the preceding
                    * Physic-logical Anatomy, p. 182. 
GLANDS.
421
 paragraph, there are others, viz: the larger size of  the follicles of  the
 mucous glands, and the coarser and firmer texture of the membrane
 which constitutes their parietes.
   That the follicles do really  communicate with each other, is proved
 by the  numerous circular apertures which they frequently present,
 and which reminds one of those of the air-cells of  the lungs.   (Plate
 LIII. fig. 4.)
   The  epithelium contained within the follicles  is  very small,  the
 majority of the cells being spherical.
   The  membrane of the  follicles  would  appear to be fibrous, and is
 sufficiently resisting  to preserve their  form under ordinary pressure
 and manipulation.

                          BRUNNER'S  GLANDS.
   These glands have  been  already referred  to under  the head of
 mucous glands, with which they are structurally identical.
   I was led, for a short time, into the  error of arranging them with
 the tubular glands, in consequence of observing that  each  of  the
 larger glands of Brunner was generally furnished with several tubu-
 lar ducts; and  this led me at  first  to infer that they were  formed
 entirely upon the tubular type, which is not the case.
   In those  instances in  which more  than one duct  proceeds from
 what appears to be a single gland, this  gland is not really simple, but
 compound;  that is to say, it is  formed of several clusters of follicles
 held together  by fibrous tissue, and  from each of  which a separate
 efferent duct proceeds.
   The glands of Brunner  occur only in  the duodenum, and occupy
 usually   the upper two-thirds  of  that  intestine: their number  and
 extent of distribution vary, however, in different subjects.
   For further particulars, see  the description of the Mucous Glands.

                          COWPER'S GLANDS.
   Cowper's, or  the anti-prostatic, glands  are, as already mentioned,
 mucous glands,  being the  largest examples of this description of gland
 met with in the human body.
   The description  given  of these glands  by authors in general, their
large size and their apparent constitution  of lobules, were the reasons
which led to their being temporarily  classified with the lobular glands.
   The  description given  of  the mucous  glands  applies in  every
respect  to these. 
422
THE  SOLIDS.
   A knowledge of their true structure and relationship explains their
use, concerning which  many vague conjectures have been hazarded.


                        LOBULAR  GLANDS.

                           SALIVARY  GLANDS
   The  salivary glands  include the  parotid, sub-maxillary, and lingual
glands,  together with the pancreas.
   These several glands resemble each other very closely in structure,
as well  as  in the characters of the secretions furnished by them.
   The salivary glands  consist of lobes and lobules, on the surface of
which the  blood-vessels ramify;  the lobes  are made up of the lobules,
and the lobules themselves  consist  of follicles of a rounded or oval
form, and  each of which is furnished  with a minute efferent duct,
which,  uniting with  the other ducts of the same size, forms other
larger ducts, and these, uniting again with others of still larger calibre,
at  length  form,  by  their union, the  main excretory tube of these
organs.   (Plate LIV. figs.  1, 2, 3, 4,  5.)
   The follicles contain  numerous minute granular cells ;  and those of
the pancreas,  in  addition,  frequently  many shining  globules  of an
oleaginous character.
   Such is  a  brief description of the salivary glands in their adult
form: in their embryonic condition, however, they do  not consist of
lobes and lobules, but the terminal* efferent  ducts  end  in single folli-
cles, which afterwards  become multiplied, until at length  clusters of
them appear—the incipient lobules.   (Plate LIV. figs. 1, 2.)
   The structure of these glands  may be readily followed out without
the aid  of  injection.*

  * It will be observed, that the above description of the salivary glands agrees
closely with  that ordinarily given.   An examination of these glands, instituted since
this description  was in type, has convinced me that they approach in organization
very nearly to the mucous glands, of which they are to be  considered as a variety.
The salivary glands differ indeed from  the mucous in the particulars  already men-
tioned, viz: in the less size  of the  follicles, and in their more complete shape, but
nevertheless  are furmed upon a similar type of organization.  The efferent duct with
which each of the follicles of the salivary glands is said to be furnished is so short,
that it in very  many instances scarcely deserves  the name of such; the general
arrangement is that of a number of follicles, almost sessile, clustering around the
terminations of the salivary  ducts. 
GLANDS.                         423
                         LACHRYMAL GLANDS.
  These glands resemble the salivary in all essential structural partic-
ulars :  they are, however,  separated from them in consequence of the
difference in the character of the secretion which they furnish.

                          MAMMARY  GLANDS.
  The mammary glands do not require any lengthened description,
since they also are  formed upon precisely the same type as the sali-
vary and lachrymal glands.
  The principal structural  difference  has reference  to  the efferent
ducts.   Each salivary gland is furnished with but a single excretory
duct, while to each mammary gland there  are  as  many as  eight or
ten ducts which open on  the apex of the nipple: the ducts of the
mammary gland are also remarkable for their great capacity, for it is
in them that the  milk principally collects when it is  allowed to
accumulate.
  When the follicles  of  a  mammary gland in  an active  state  are
examined, vast numbers of milk globules, of various sizes, will be per-
ceived within them; and  lying in the midst of these,  the  small gran-
ular secreting cells  will be seen: these,  however, do not contain milk
globules, from which it follows that the milk corpuscles are not formed
within the granular cells, but external  to them, although still within
the cavity of the follicles.   (Plate LIV. figs. 3, 4, 5.)
  Mammary glands exist in the human  male as well as female breast,
the essential structure  being the same in both, as proved by the many
cases now on record, in which infants have been suckled by men.
  In childhood and old age the  mammary  glands consist of white
fibrous tissue, in the midst of which traces only of the follicles can be
perceived.
  Numerous lacteals arise from the neighbourhood of the follicles;  by
these, the more watery parts of the milk  are absorbed when this is
retained for any length of time within the breast, and in  this way the
distension of that organ is from time to  time relieved.

                              LIVER.
  The liver has  been described as consisting, like the other glands of
the lobular form, of lobes, lobules, and follicles or acini;  and, indeed,
in some of the lower animals, this organ has such a constitution.  It
has,  nevertheless,  recently become a  matter of very  great  doubt 
424
THE  SOLIDS.
 whether in the Mammalia, at least,  the same  type or organization
 prevails, and whether the structure of this gland in this class of animals
 is not of a totally  different kind.
   The mammalian liver consists indeed of lobes  and lobules, but the
 question is as to the existence of the  follicles or acini furnished with
 their efferent  ducts.
   In the adult liver, the  division into lobes, even, is essentially arbi-
 trary; so that, in  fact, it is of lobules alone that the liver is entirely
 composed.
   Lobules.—The  lobules of the  liver  are aggregations or  masses of
 granular or secreting cells, of a more or less angular form, first resting
 upon, and then traversed by, branches of the hepatic vein, and enclosed
 on all sides by a  process of the capsule of Glisson.   The intervals
 separating the sides of two lobules from each other are called  inter-
 lobular fissures, and  those  which exist  where three or more lobules
 touch each other,  inter-lobular spaces.
   These lobules, for the  most part, are perfectly distinct  from  each
 other; nevertheless, not  unfrequently two of them are more or less
 united together, as is seen especially on the surface of the liver, and
 in preparations in which the  hepatic system of vessels  has   been
 injected.  (Plate LIV. fig. 6.   Plate LV.fig. 1.)
   The lobules of the liver are of sufficient size to be easily recognised
 with  the unassisted sight:  they vary, however,  in  dimensions, not
 merely in the liver of different  animals, but likewise in that of the
 same: in some animals,  also, as in the rabbit  and pig, their form, as
 well  as their  size, may  be clearly defined; and in these  they are
 evidently angular.   (Plate LV. fig. 1.)
   Such is a brief description of the lobules of the liver: the supposed
 follicles or acini are  nothing more than the intervals between the
 meshes of the  capillary vessels which ramify through the substance of
 the lobules, and the outlines of which vessels may be readily followed,
 even  without  the  aid of injection, their course being indicated by a
 number of dark lines.
   Mr. Kiernan supposed  that the acini were really follicles, and that
 they occupied the  spaces which he conceived existed between the
 meshes of his lobular plexus of biliary ducts.
   The secreting apparatus of the liver consists not only of lobules and
their component cells, but also of biliary ducts and gall-bladder.
   Biliary Ducts.—In his admirable paper on the liver, inserted in the
"Philosophical Transactions" for 1833, Mr. Kiernan describes the 
GLANDS.
425
 biliary ducts as terminating in the substance of the lobules in a com-
 plicated net-work of minute biliary vessels, which he termed the lobular
 biliary plexus.   Much doubt, however, has recently been cast upon the
 accuracy of this description, notwithstanding that it has received the
 confirmatory testimony of very many high microscopical authorities.
   The first observer who, I believe, expressed doubts of the existence
 of a lobular biliary plexus was  Mr.  Bowman, to whose  numerous
 microscopical  researches science  is so much indebted.
   More recently still, Dr. Handfield Jones, in a paper "On the Secre-
 tory Apparatus of the Liver,'"* has not merely expressed the same
 doubts, but has entered fully into the reasons on which his opinion
 is based.
   Dr.  Jones founds his belief of the non-existence of a lobular biliary
 plexus upon the following observations:
   " First, the non-existence of basement membrane  in the interior of the lobules,
 which, in common with Mr. Bowman," he writes,  " I have been unable to detect; yet,
 were this simplest constituent of a duct present, it could hardly escape notice, espe-
 cially as in other glands it admits of being readily demonstrated; at the broken margin
 of a lobule it may be well seen that  the broken  extremities of the linear series are
 quite free, and exhibit no trace of any containing membrane.  Secondly, if the margin
 of a lobule be carefully examined, where it forms the sides of a fissure, the basement
 membrane may often be clearly seen, and through its transparent texture the terminal
 ceils of the linear series are easily distinguished, resting against and contained by it.
 Now, were the membrane inflected to form lobular ducts, surely some indentation or
 irregularity would be visible at the margin of the lobule, but I have often traced the
 outline'carefully without observing any such.   A third proof is supplied by the result
 of some experiments  which I made  on  rabbits.   I tied the duct. com. choled., and
 shortly after death, which took place at periods varying from  two to four days, I
 examined their livers: these organs were found to be beset on the surface and
 throughout  their  substance with numerous spots of deep yellow colour, evidently
 produced by accumulation of bile;  a section  of these spots, examined under the
 microscope, showed that they were  very partial, never extending throughout the
 whole of a lobule, but  frequently situated in two  or more adjacent; their outline was
 always well defined, and not the slightest appearance of a distended plexus of ducts
 could be observed.  This last evidence appears to me conclusive.  I can hardly con-
 ceive  that, if any plexus of anastomosing ducts existed, the accumulation of bile
 should take place in definite spots, and those not always situated in a single lobule.
 but in two or three adjacent."
   Of the proofs of the existence  of a lobular biliary plexus,  supposed
 to be derived from injection, it may be remarked, that these are, in all
probability, fallacious,  the injection escaping from the extremities of
the biliary ducts, and passing  into, generally, branches of the portal
                     * Philosophical Transactions, 1846. 
426
THE  SOLIDS.
vein from which it extends irregularly into the lobular capillary plexus,
and it is this plexus, filled with  injection  from the biliary duct, that
Mr.  Kiernan, it appears  to me,  took  for a lobular biliary plexus.  It
still, however, must be regarded as a singular circumstance that the
injection should so generally pass, after its escape from the ducts, into
blood-vessels, in place of becoming extravasated around the  apertures
of the ducts from which  the injected material has escaped.
   Presuming it, then, to  be concluded that there is no lobular biliary
plexus, let us next inquire in what manner the biliary ducts do really
terminate.
   From the  further researches of Dr. Handfield Jones, contained in
a recent paper communicated to the Royal Society, and entitled "On
the Structure and Development of the Liver," it would appear that
the biliary ducts  terminate in  the vertebrate series of animals in the
inter-lobular fissures and spaces in closed and rounded extremities.
(Plate LVII. fig. 1.)
   If a branch of the hepatic duct be taken up with the forceps, it may,
by delicate manipulation, be dissected  out from the surrounding paren-
chymatous tissue.  A branch thus prepared, when placed under the
microscope, will be seen  to be composed of numerous ramified biliary
ducts of various sizes: the extremities of a majority of these are even
broken off; but several are evidently  entire, and these are  rounded,
as represented in  Plate LVII. fig. 1.
   These ducts are not simple tubes, formed of basement  membrane,
but are lined by  a  regular layer of epithelial scales:  these serve to
secrete  the mucus, which partly occupies them;  and their  presence
accounts for the  great difficulty experienced in getting the  injection
to flow  along the ducts.
   The experiment of dissecting out a branch of the hepatic duct from
the parenchymatous tissue of the liver is most readily performed in
the soft livers of  most fish; as the plaice, sound, &c.; but it may be
also effected in the livers of the various mammalian animals.
   The author has repeatedly examined branches of the hepatic duct
thus prepared, and his own independent observations fully corroborate
those of Dr.  Handfield  Jones, to whom for  his very carefully con-
ducted inquiries on the intimate structure of the liver, physiological
anatomists are much indebted.
   The mucous  membrane lining the larger hepatic duct is, according
to the observations of Mr. Kiernan, follicular.
   Secreting Cells.—The  secreting structure of the  liver,  as of all 
GLANDS.
427
other truly glandular organs, is cellular, the majority of the cells being
perfect, and consequently nucleated, but some few consisting of nuclei
only, the most essential element  of  the cell.  Each cell may contain
more than one nucleus.
  These cells are disposed in series, which radiate from the centre of
each lobule, occupied by the lobular hepatic vein: the radii are not
formed of single rows of cells placed simply end to end, but the cells
frequently partially overlap each other.  (Plate LIV. fig. 6.)
  This  linear disposition of  the cells would appear to be determined
by the radiated arrangement of the vessels which proceed on all sides
from the central hepatic vein.
  Dr. Jones considers that this arrangement of the cells is connected
with the secretion of the bile, and that it facilitates the transmission of
this  fluid from the centre  to the circumference of the lobules : when
it has reached this, it is discharged into the inter-lobular  fissures and
spaces,  to be absorbed into the ducts by an endosmotic action deter-
mined by the denser mucoid fluid contained within them.
  Dr. Handfield Jones has also observed that frequently the cells are
not  merely disposed in linear series, but  that  they likewise  coalesce
with each other  by their  opposed margins, whereby the cavities of
several  cells are made to communicate with each other.  This union
of the cells Dr. Jones considers  to be intended  to facilitate still further
the  transmission of the bile along the series  of cells; and he seems
disposed to regard it,  if not absolutely essential to this transmission,
yet as of very general occurrence.   There can be no question, how-
ever, but that, in the  great majority of cases, the bile is  passed from
cell  to cell, independent of any  such union: this is proved by the ex-
ceeding rarity of the occurrence of rows of cells united in the manner
described and figured by Dr. Jones.
  The  same accurate  observer  considers  that the first secretion of
bile  takes place in the most  central cells  of the lobule, and that this
fluid is  accumulated in the greatest quantity, and its elaboration per-
fected, in the marginal cells of the lobule.   These opinions are founded
upon the following experiments and observations:  thin sections of the
liver of a rabbit being examined, the ductus communis choledochus of
which had been tied twenty-four hours before  death,  it was manifest,
in almost every instance, that accumulation of bile had  taken  place
in the centres of  the  lobules, as indicated by  a yellow zone of some
width surrounding the  intra-lobular  vein. Now this  case, in the
opinion of Dr. Jones, presents the earliest  effect of interruption to the 
428
THE  SOLIDS.
flow of the secretion; and the appearance described seems to point out
the exact  spot where the secretion  had  its origin, viz:  in the com-
mencement of the rows of cells surrounding  the central axis of the
lobule,  as represented by the  lobular hepatic  vein:  again, in many
livers, a  remarkable difference  may  be observed in the  condition of
the marginal  cells and those placed  more centrally; while  the latter
have appeared of their usual pale or light yellow colour, and.have con-
tained but one or two minute oil globules, the former have  presented
a darker and  more opaque  appearance, arising from the presence of
numerous oil  globules.
   These observations, especially when considered in  connexion with
the mode of termination of the bile ducts, render it almost certain  that
the secreting  process reaches  its termination  near the margin of the
lobule.
   Dr. Jones recognises an active and  a passive condition of the lobules
of the liver, and thus describes the differences in the appearances of
the margins of the lobules in the two states:

  " The appearance which the margin of a lobule presents when the process of secre-
tion has been proceeding actively, differs much from that which is observed when the
lobule, so to speak, is quiescent: in the latter case, as I have described it, the margin
is well defined, and bounded by  a distinct basement membrane;  while the terminal
cells of the linear series  contain few and minute oil globules, and do not appear to
project outwards in any degree:  in the other case, the margin of the lobule has  an
opaque cloudy appearance from the multitude of oil globules.   Several cells are seen
projecting into the cavity of the duct, giving the wall  occasionally a tuberculated
appearance:  these cells contain oil globules,  and their wall is sometimes so extremely
delicate as to be barely perceptible even under a high power.  Very many oil globules
are also seen, which lie evenly in contact with the sides and floor of the duct: it is
difficult to determine whether these have escaped from their cells or not: it seems
probable, however, that they are  for the most part free, having recently been liberated
by the solution of their cell wall.   The margin of a lobule, in the condition now
described, presents no trace of basement  membrane; the cells themselves form the
wall of the ducts, preserving still the general outline: it seems, therefore, certain that
the basement membrane is only a temporary structure, which disappears when the
cells are actively discharging their contents.  A forcible and instructive contrast to
the above condition  was exhibited by a liver which I  examined, which was  in an
advanced state of fatty degeneration: in this the linear arrangement of the cells was
lost; they lay confusedly together;  and were gorged with their fatty contents; the
margin of the lobule, far from exhibiting any tendency to discharge the retained secre-
tion, was invested, and, as it were, closely bound by a membrane, not of the delicate
transparent texture of the basement tissue, but much more opaque, and closely resem-
bling the semi-fibrous aspect of thin layers of false membrane." 
GLANDS.
429
  With respect to  the dissolution of the membrane surrounding the
lobules at  the period of the most active secretion of the bile, it may be
remarked  that it is a matter of very great question whether this is either
a constant and necessary occurrence, or even a very frequent one.
  Gail-Bladder.—The gall-bladder is  composed of an outer,  strong,
fibrous tunic, and an inner mucous one: this latter has a honeycomb
arrangement, and is of the follicular type: the larger meshes, which
are plainly visible to the unaided  sight, are divided by ridges of mem-
brane into four or five other spaces or depressions of irregular size and
form, also discernible without glasses: and these again are still further
sub-divided into other cells very numerous, and which are only to be
seen with  the aid of the miscroscope.  It  is these last which constitute
the follicles of the mucous membrane of the gall-bladder, which differ,
however,  greatly  from the  ordinary  tubular  follicles of compound
mucous membranes, being simple cells or depressions formed by the
plaited and ridged arrangement of the membrane of the  gall-bladder.
The follicles in the hepatic duct,  and also in the inner tunic of the
vesiculae  seminales, would appear to be of the same character.
   If air be  inserted, by means of the blow-pipe, beneath the  mucous
coat, the latter will  be thrown up into lobes, each of which corresponds
with  one  of the larger honeycomb cells:  this fact shows that the
mucous membrane of the gall-bladder is bound down to the  fibrous
tissue beneath, principally in the intervals between the cellular depres-
sions alluded to.
   Injection thrown  into the  ductus communis choledochus  very
frequently reaches  the  coats of the gall-bladder:  this fact  affords an
interesting and striking proof that the vessels ordinarily injected from
the common hepatic duct are not biliary, for it is generally acknowl-
edged that biliary  ducts  do not exist in this situation—a conclusion
to which  one, without  hesitation, arrives, on reflecting  that  in such
a situation they could serve no possible purpose.
   General Remarks.—Should  the foregoing account of  the mode of
termination of the biliary ducts be correct, of which scarcely a rea-
sonable doubt  can be entertained, it is evident that in the vertebrate
class of animals, at least, the  liver is not of the follicular type, and
that in them this organ should be separated from those glands formed
on the follicular type.   In the fact  of the secretion  making  its way
into closed vessels, the liver clearly manifests an intimate and essential
relationship with the vascular  glands.
   The liver, then,  in the vertebrate series, is the only exception with 
430
THE  SOLIDS.
which we  are  at present  acquainted, of an organ  which, being
furnished with an excretory duct, is yet not formed on the follicular
plan of development.
  In all follicular glands, the secreting cells are situated on the inter-
nal surface of the basement membrane:  in  the liver, however, they
are placed upon its external surface, the true basement  membrane
terminating with the termination of the biliary vessels.
  Mr. Bowman regards the innumerable  series of secreting cells as
representing the continuation of the biliary ducts, and a rudimentary
condition of which he considers them to be; in the same manner as
linear series of granular cells represent, according to some observers,
the rudimentary form of other vessels and tissues; as, for example, the
muscular fibre and the primitive nerve tubule.

                      Vascular Apparatus.
  The vascular apparatus of the liver has been well understood since
the period of the publication  of  Mr. Kiernan's Researches.  This
apparatus consists of hepatic veins, portal vein, and hepatic artery.
  Hepatic Veins.—The venae cavae hepaticae commence in the centre
of each lobule of the liver by a plexus of capillaries, which penetrates
it in all directions; these uniting, form larger vessels, and which, again,
join together, to constitute the central lobular vein:  this, escaping
from the lobule  altogether, becomes what has  been termed the  sub-
lobular vein, and it next  unites with other sub-lobular veins to form
the main branches of the hepatic veins.   (Plate LV.fig. 1, 2.)
  Portal Veins.—The portal vein is mainly formed by the  union of
the inferior and superior mesenteric veins; and these, again, have
their origin principally in the confluence of the capillary vessels of
the villi of the small intestines.
  The portal vein enters the substance of the liver at  the  transverse
fissure.   After numerous ramifications,  many of its  branches  are
spread over the outer surface of the lobules: these branches are called
the inter-lobular veins: from these branches others still smaller  pro-
ceed ; these, penetrating the substance of the  lobules, break up  into
capillaries, which unite with the capillaries of the lobular hepatic veins,
already spoken of; and it is  the capillaries of both hepatic  and portal
veins, thus united, that constitute the lobular capillary plexus.   (Plate
LV.fig.  4;  Plate LVI.fig. 1.)
  The lobular plexus  may  be completely injected either  from the
portal or hepatic veins, as might be supposed from the fact of its being 
GLANDS.
431
constituted of vessels derived from both.  This plexus, however, is not
always fully injected: it is only when the operation of injection has
been very successfully performed that this  result is secured:  some-
times, in injecting from  the portal vein, the injection fills  only those
vessels which ramify on the surface of the lobules, viz:  the inter-lob-
ular veins, as represented  in Plate LV.fig. 4; in other  instances, the
injection  will penetrate further, and fill that portion  of the  lobular
plexus which is formed by the capillaries which belong  especially to
the portal vein; in this case a zone of capillaries surrounds each lob-
ule,  as figured in Plate  LVI. fig.  1.  In others, again, the injection
will fill the entire lobular plexus, and extend even to the central lob-
ular hepatic vein (Plate LVI.  fig. 4);  in  this latter case, the entire
section of the liver appears but a mass of capillaries, the size and form
of the lobules being indicated merely by the cut extremities of the
larger lobular and inter-lobular vessels.
   On the other hand, in injecting from the hepatic veins, the injection
may reach only the central lobular vein and its principal ramifications,
as shown in Plate LV.fig. 1;  or it may fill that portion of the lobular
plexus  especially  formed by the capillaries of the hepatic veins, in
which case each  lobule will  appear to be  the centre  of  a separate
injection  (Plate LV.fig. 2); lastly, the entire lobular capillary plexus
is sometimes injected from the hepatic veins in the same manner as
from the portal vein.
  In those instances  in which  two lobules are seen  to  be united
together, the vessels are also observed  to  proceed directly from  one
to the other;  this communication is especially evident  in injections
of the hepatic veins.   (Plate LV.fig. 2.)
  The form of the portal vein, from its origin in the villi of the intes-
tines to its termination in the lobules of the liver, may then be com-
pared either to two trees joined by their trunks, or to a single uprooted
tree.   The preceding account renders it evident that  it is from the
blood contained in the portal vein that the secretion of bile takes place.
  In those cases in which  the  blood-vessels become injected from the
biliary ducts, it is usually the portal system which receives the greater
part of the injection; and this  is thrown  into it at different points
irregularly, so that there are no definite zones of capillaries marking
out  the lobules; but masses of capillaries  are seen here  and there
arranged without any certain order.
  Hepatic Artery.—The hepatic artery is the nutritious vessel of the
liver; it supplies the vessels of the hepatic ducts, the vasa vasorum,
and  the capsule of the liver. 
432
THE  SOLIDS.
  It is  distributed principally, however, to the capsules covering the
lobules, and to the general capsular investment of the liver.
  Some of the inter-lobular or lesser capsular  branches penetrate the
substance of  the lobules, and  terminate  in the  portal capillaries of
the lobular plexus.   (See Plate LVI. fig.  2.)
  The outer capsular branches are remarkable for their great length,
and the simple manner in which  they divide and sub-divide.
  The hepatic artery does not anastomose  with the hepatic vein.

                            Pathology.
  The  pathology of the liver may be  divided into two sections,
according as  the  seat of the disease affects its secreting or vascular
apparatus.

                      Secreting  Apparatus.
  Two abnormal conditions of the  secreting cells of the  liver have
been noticed: in the first, biliary engorgement,  the  cells are seen to
contain a greater quantity of biliary matter, in the form of globules
of various sizes, than ordinary; in the second, fatty degeneration of
the liver, the  cells are laden  with innumerable globules  of an ole-
aginous character; this  condition  of the cells, of  course, impairs, to
a very great extent, their secretory powers.   (See Plate LVII. fig. 2.)
  Livers thus laden with oleaginous particles have been termed fatty;
this term, although expressive, is  certainly incorrect.  Fat is  a dis-
tinctly organized cellular constituent of  the higher  forms  of animal
organization;  and each  true fat  globule  is a perfect cell, constituted
of nucleus  and cell wall.  The minute globules of oil existing  in the
cells of the liver and of some other glands, especially in disease, have
none of the attributes of cells; they are  merely globular collections
of an oily fluid,  similar to those which exist in the  cells of cartilages.
  It is, therefore,  evident  that  the  term  fatty, applied to  organs
affected in the manner described, is  scientifically and fundamentally-
improper: the appellation of oily would be  more correct.
  The truly fatty liver and kidney do, certainly, occasionally present
themselves  to our notice; in these, there is an accumulation of true
fat cells, not, indeed, within the epithelial particles, but  in the inter-
spaces between the lobules and tubules, and also beneath  the capsules
to a less degree.
  The microscopic  characters of the disease  called cirrhosis do not
appear to have been as yet satisfactorily determined. 
GLANDS.
43:3
                       Vascular Apparatus.
   A knowledge of the distribution of the blood-vessels in the lobules
of  the  liver,  has enabled  the pathologist  to  explain  satisfactorily
various abnormal appearances connected with its vascular apparatus.
   The lobules of the liver  of persons or  animals  that have bled to
death, or that have died in an exceedingly anaemic  condition resulting
from disease, present a pale and ex-sanguine appearance, arising from
the small quantity of blood contained within the blood-vessels.
   A second very  common appearance  of  the  lobules of the  liver,
after  death, is that  in which  they are red  in  the centre,  and pale
around the margin.   This condition arises from the presence,  in the
venous hepatic vessels, of a considerable quantity of blood, the  portal
vessels being at the same time almost destitute of this fluid;  it  has
been called by Mr. Kiernan the first stage of hepatic venous conges-
tion, and is said to be due to the continuance of  capillary action in
the vessels after the general circulation has ceased.
   In the second stage of hepatic venous  congestion, not merely the
centres of the lobules  are red,  but also the portal plexus in parts;  the
parts  of the lobules which  are most free from  congestion  are those
surrounding the inter-lobular  spaces; so  that the non-congested por-
tions appear in the form of isolated and irregular patches, in  the midst
of  which  are situated the  inter-lobular  fissures  and spaces.   The
second stage of hepatic venous congestion commonly attends disease
of the heart and other disorders in  which there is an impediment to
the venous circulation, and it also  gives rise,  in  combination with
accumulation  of bile in  the secreting cells, to  those various appear-
ances which characterize the  nutmeg or dram-drinker's liver.
  A third form of venous congestion is that which affects the portal
veins  alone; in this the margins  of  the lobules are  red, while their
centres are pale; it is the very reverse condition to hepatic venous con-
gestion in its first stage, and has been distinguished  by Mr. Kiernan
hv the name of portal venous congestion.   This form of congestion
is rare,  and has hitherto been noticed to occur in children only.
  The fluid of the liver, the  bile, has already been described in this
work;  in addition  to  the epithelial  scales derived from  the mucous
membrane  lining  the  gall-bladder, the bile frequently contains,  when
inspissated, concrete masses of biliary matter, which have been mis-
taken  for true cells; also, crystals of  cholesterine, gall-stones, and the
parasite called the fluke with  its ova.
                              28 
434
THE  SOLIDS.
    Hydatids  are  frequently developed  in the substance of the liver;
 these often attain a very large  size.*

                        Development  of the Liver.
   "With respect to  the development of the liver, the authorf considers the opinion
 of Reichart to be decidedly the correct one, namely, that its formation commences
 by a cellular growth from the germinal membrane, independently of any protrusion
 of the intestinal canal.  On the morning of the fifth day, the oesophagus and stomach
 are clearly discernible, the liver  lying between the heart, which is in the front, and
 the stomach, which is behind; it is manifestly a parenchymal mass, and its border is
 quite distinct and separate from the digestive canal at this period;  the vitelline duct
 is wide, it does not open into the abdominal cavity, but its canal is continued into an
 anterior and  posterior division, which are tubes of homogeneous  membrane, filled,
 like the duct, with opaque  oily contents;  the anterior one runs forwards, and forms
 behind the liver a terminal expanded cavity, from which then passes one offset, which
 gradually dilating opens into the stomach;  a second, which runs in a direction
 upwards and backwards, and forms apparently a caecal prolongation; and a third and
 fourth, which are of  smaller size, arise from the anterior part of the cavity and run
 to the liver, though they cannot  be seen to ramify in its substance;  at a somewhat
 later period, these offsets waste away, excepting the one which is continued into the
 stomach, and then the mass of the liver  is completely free and unconnected with
 any part of the intestine.  As the vitelline duct contracts, the anterior and posterior
 prolongations of it  become fairly continuous, and form  a loop of intestine,  the
 posterior division being evidently destined to form the cloaca and lower part of the
 canal.  The final development of the hepatic  duct takes place about the ninth day,
 by a growth proceeding from the liver itself, and consisting of exactly similar mate-
 rial ; this  growth extends towards the lower part  of the  loop of the duodenum,
 which is now distinct, and appears to  blend with the coats of the intestine; around
 it, at its lower part, the structure of the pancreas is seen to be in process of forma-
 tion.  The further process of development of the hepatic duct will, the author thinks,
 require to be carefully examined; but the details he has  given in this paper have
 satisfied him of the correctness of the statement that the structure of the liver is
 essentially parenchymal."

  * On  one  occasion I  noticed the  liver to be thickly  studded throughout with
 numerous cysts, the  largest of about the twelfth or  eighth of an inch in diameter.
These cysts contained a gaseous fluid only; the secreting cells included a greater
quantity of oil than natural.
  f Dr. Handfield Jones, Abstract of Paper in  Philosophical Magazine, September,
 1847. 
GLANDS.
435
                                LIVER.
   [For a very accurate account of the minute structure of the liver, with
excellent drawings, the  reader is referred to  a paper "on the Comparative
Structure of the Liver," by Dr. Jos. Leidy, of Philadelphia, and published in
vol. xv.  (new series) of American Journal of Medical Sciences, pp. 13-23.
   Dr. Leidy's researches are confirmatory of  the views of Dr. Kiernan, as
laid down in the paper referred to in the text.
    Appended  to Dr. Leidy's  paper, will  be  found a table containing the
measurements of the secretory cells of the liver in several of  the different
orders of animals.
   The minute structure  of the liver  should  be studied  in  both the  recent
state, and after injection;  the method  in the  recent state is  the  same as
already pointed out for other  organs—thin sections in  different directions,
dissected with needles under water, and viewed with low powers;  others
may  be  compressed, and treated with  acetic  acid, whereby the nuclei of
the secretory cells are readily brought into view.
   The arrangement of vessels is of course best seen after injection.   Any
one particular order of  vessels may be filled, or  the four orders may be
injected with different  colours.   When  this is desired, the following division
will be the  best: Arteries,  blue;  vena portse, yellow;  hepatic vein, red;
hepatic duct, white.
   D'-s. Goddard and Neill have made some successful injections of the liver,
by which the four sets of vessels were filled; using red for the arteries and
blue for  the hepatic vein.   It will  be  found more difficult to  inject com-
pletely the liver than any other organ.  After injection, sufficient time must
be allowed for  drying.   Slices  may  then be cut in different directions, and
after  these have been moistened with turpentine, may be examined with a
low power.    If the vessels seem  to be  well filled and  distinct, without
extravasation, the specimens may be permanently mounted in cells with
Canada balsam,  without heat.] 
430
THE  SOLIDS.
                           PROSTATE  GLAND.
   This gland belongs to the  compound follicular division,  and not to
the lobular class  of glands;  its structure  consisting of clusters  of
follicles, united by ducts: these follicles are usually of an oval form,
of large size, and frequently communicate with each other.
   The  follicles  cannot be exhibited separately as such, being mere
excavations or cells which exist in  the substance of the  gland, and
which are lined by prolongations of the mucous membrane  of  the
urethra.
  That the follicles constituting the essential structure of the prostate
gland are simply inversions of the genito-urinary membrane, is proved
by the fact that the epithelium which lines them is of the clavate form,
which has been elsewhere described as  appertaining to the bladder.
  In consequence  of the large size of the follicles, and of the fact of
the epithelium which lines them forming on  their interior but a single
and even layer of cells, a considerable space or cavity  exists  in  the
centre of each follicle.
  The tissue out of which the follicles are formed, and to the presence
of which the prostate owes  much of its size and nearly all its firmness,
is a  good  example  of the nucleated variety of  fibro-elastic tissue,
approaching in its characters very  closely  to  the  muscular fibre of
organic life.
  The increase which  so  generally takes  place in the size of  the
prostate in old age is due to an increased development of the above-
named tissue.
  From the preceding description, it would  appear that  the office of
the prostate is simply to  secrete mucus, and that it does not, as has
been conjectured,  furnish any peculiar  secretion necessary, as some
even have supposed, to fecundity.
  The most  curious circumstance about the prostate is the almost
constant occurrence, in considerable numbers, of concretions or calculi
formed of concentric lamellae.   These calculi are situated in the fol-
licles  already described; they differ  from each other very greatly in
size, form, and  colour, and in the number, arrangement, and strength
of the  concentric  capsules.   Ordinarily, the concentric  lamellae are
disposed around a single  nucleus of granular and amorphous matter;
sometimes, however, there  are two or even three separate nuclei
within each calculus; in these cases, each  nucleus will be encircled
by its own lamellae, the entire of them being also included in a greater 
GLANDS.
437
 or less number of larger lamellae.  The form of the calculi, although
 various, has a tendeney to the triangular; and the colour, although
 differing  in different glands,  depends upon their  size and age, the
 younger  and  smaller being transparent and almost free from colour,
 the older and larger being of a deep orange  or ochre  tint.   (Plate
 LVII. ^. 3.)
   The prostatic calculi have been noticed by several observers; by
 Cruveilhier, Dr. Jones,  Mr. Quekett, Mr. Adams, of the London Hos-
 pital, Dr. Letheby, and myself.
   Dr. Jones*  describes  them  a,s originating  in  oval or rounded
 nucleated and organic vesicles, which enlarge, and then  have their
 amorphous  contents arranged into concentric laminae.   Dr. Letheby
 believes that "they are concretions which arise exactly like those of
 the kidney  and bladder, viz:  by a succession  of external  deposits;"
 this view is most probably the correct one.
   Dr. Letheby has favoured  me with the  following observations on
 the chemistry  of these  bodies: "You will  find," he says,f  "that they
 consist of phosphate of lime, which is mixed up with a large quantity
 of nucleated fat cells and inspissated  mucus; the whole  being gen-
 erally tinted with some shade of yellow or  red."
   "They are  slowly soluble  in  strong acetic and muriatic  acids;
 more quickly when heated, and they then leave numerous fat globules
 and remnants  of cells.   They are not  dissolved by potash or strong
 ammonia.   Heated before the blow-pipe, they char, and leave a small
 residue of earthy matter."
   The smaller calculi resemble closely the concentric corpuscles or
 bodies described by Mr. Gulliver as occurring in fibrinous clots, and
 many of them do not present  concentric lamellae.

                       TUBULAR GLANDS.
                        SUDORIFEROUS GLANDS.
   The sudoriferous are the most numerous  class of glands in the body,
 their  apertures thickly  studding the entire external surface, and far
 outnumbering the  sebaceous glands, which have a somewhat similar
 distribution.
   They consist of convoluted tubes of nearly equal diameter, which
unite, at irregular intervals, with each other, forming looped meshes, all
of which terminate in a single excretory duct.  (See Plate LVII. fig. 4.)
              * Medical Gazette, 1847.             fin litt. 
438
THE  SOLIDS.
   The excretory duct is  either  straight or  coiled  spirally,  and it
always terminates in a raised and rounded mammillary process, evi-
dent on the surface of the  epidermis.   (See Plate XXIII. fig. 1.)   It
is straight where the epidermis which it has to pass  through is thin,
and where, in consequence, its course to the  surface  is short;  on the
other  hand, it  is coiled in spires  which are  remarkable  for their
extreme regularity, where  this membrane is thick, as in the palms of
the hands  and soles  of the feet (see Plate XXIV.^r. 3), and  where
as a result its course is prolonged.   The acting  cause which  deter-
mines this  spiral arrangement is  probably the gradual  flattening to
which  the outer and older layers of* epidermic cells  are continually
subject from pressure.
   The duct of the sudoriferous glands is formed by an  inversion of
the epidermis itself, similar to that which forms the lining of the hair
follicles.  The sudoriferous glands never open into the  hair follicles,
but in  the  intervals  between  them, and also  between the sensory
papillae with which the true skin is covered.
   The  palms of the  hands and soles  of the  feet, being entirely free
from the sebaceous glands,  are occupied exclusively with the sudorif-
erous;  they are  placed in lines or rows, which  are variously curved,
and which correspond with the arrangement of the sensory papillae of
the true skin.   The apertures of the sudoriferous glands on the  ridges
of the  skin are just perceptible  with  the naked eye, but they become
verv evident and conspicuous with a lens of moderate power.   (Plate
XXIV. fig. i.)
   The secreting cells of the sudoriferous glands are small.
   The tubes are formed like those of the testes of a nucleated variety
of fibro-elastic tissue, and are surrounded by a similar  plexus of capil-
laries.   These  vessels, as well as  the  tubes themselves, are held in
position by bands of fibrous tissue.
   The following calculations by Mr. Wilson will serve  to convey some
idea of the extent and importance of the sudoriferous  system:
  " To arrive at something like an estimate of the value of the perspiratory system in
relation to the rest of the organism, I counted the perspiratory pores on the palm of
the hand, and found 3,528 in a square inch.  Now; each of these pores  being the
aperture of a little tube of about a quarter of an inch long.it follows that, in a square
inch of skin on the palm of the hand, there exists a length of tube equal to 882 inches,
or 73 i feet.  On the pulps of the fingers, where the ridges of the sensitive layer of
the true skin are somewhat finer than in the palm of the hand, the number of pores
on a square inch a little exceed that of the palm;  and on the heel, where the ridges
are coarser, the number of pores  on the square inch is 2,268, and the length  of tube 
GLANDS.
439
567 inches, or 47 feet.  To obtain an estimate of the length of tube of the perspira-
tory system of the whole surface of the body, I think that 2,800 might be taken as a
fair average of the number of pores in the square inch; and 700, consequently, of the
number of inches in length.  Now, the number of square inches of surface in a man
of ordinary height and bulk is 2,500; the number of pores, therefore, 7,000,000;
and the number of inches of perspiratory tube, 1,750,000; that is 146,833 feet, or
48,600 yards, or nearly twenty-eight miles." *
   See Apptndix,  547 ?
                        SUDORIPAROUS  GLANDS.
   [The paper by Mr. Rainey, referred to in the  Appendix, undoubtedly
gives the true structure of the sudoriparous glands, and their ducts:  hence
most of the figures given in the standard works of Physiology, of the course
and structure of these ducts, will be found incorrect.   The course of these
ducts is perhaps not stated at sufficient length in the Appendix.  Mr. Rainey
divides the duct into two portions, that passing through the dermis, or dermic
portion, and that continuous through the epidermis, or epidermic portion.

  " The membrane composing this duct is thin and transparent, and of considerable
strength; and becomes gradually dilated at its upper part, and terminates by becom-
ing contiguous with the basement membrane, covering the adjacent papillae, and is
not continued through the cuticle to the surface.
  "The duct is lined with epithelium, which appears to have no regular form below,
being merely finely granular, but which becomes  more  distinct at its  upper part,
where it is  continuous with the deep layer of the  epidermis; namely, that lying
upon the basement membrane.
  " These lowest cells possess a greater degree of coherence  than  those which are
situated above them; so that when the epidermis is separated from the cutis after
maceration, they come away with the  cuticle in a tubular form, being in fact the
lining of the duct, leaving  the basement membrane of the papillae and the mem-
branous part of the duct in the areolar tissue.   That part of the duct which traverses
the epidermis, and which  may  be  called, for distinction, the epidermic portion, is
altogether of a different structure to the one just described, not having like it mem-
branous parietes, but merely being a spiral passage between epidermic cells and scales.
  " In the scaly or superficial layer of the cuticle, the passage is made up entirely of
epidermic scales, placed with their flat sides parellel with the axis of the tube which
they compose: while in the corpuscular or deep layer of the epidermis,  the passage
is situated between scales above and  cells below, which cells  being less and less
* Diseases of the Skin, p. 18. 
440
THE  solids.
perfect, as they are situated nearer the basement membrane, render the parietes of
the duct at its origin between the papillae very indistinct;  this part of the duct being
merely a passage through a confused  stratum  of cell-nuclei  and blastema, and
gradually contracting in diameter as  it approaches the  dermic portion, insensibly
disappears; hence its inferior extremity cannot be clearly defined by the microscope."

   The sudoriparous glands and their ducts are best studied in thin sections
of the  skin  from the  palm of the  hand  or the sole  of the %ot.   Fresh
integument will be  found best for making  these sections, although  it will
require many attempts  before  sections can be obtained which  will show the
gland and its duct in its whole course to its external opening.
   Sometimes  thin sections  can be  best obtained after the skin has been
hardened in sulphuric ether, or in a solution of chromic acid, or potash.
   A good Valentin's knife, or a broad thin razor, is the best instrument for
making these sections.   When a satisfactory specimen is obtained, it should
be mounted  in a shallow  cell  with fluid; the best  for this  purpose are
Goadby's B-fluid, naphtha and water, or a very weak solution of chromic acid.

   Plate LXXVII.,fig. 1, exhibits the sudoriparous glands and the course of
                        their ducts.
     "       "   fig. 2, A more highly magnified view.] 
GLANDS.
441
                           AXILLARY GLANDS.
   These glands, first described by Professor Horner and M. Robin,
 are probably but a variety of the ordinary sudoriferous glands.
   They are situated in the axillae, are similar in organization to the
 sudoriferous glands, but are much  larger than these.
   They doubtless furnish the peculiar and odorous secretion,  which
 characterizes the region of the axillae.
   This  odorous principle, it is said, exists in the blood ready formed,
 and the glandulae  merely separate it from that fluid.   It is also stated
 that its presence may be detected, in dried blood, on the  addition of
 sulphuric acid,  and that its odour is different in the male and female;
 also, that even the blood of different animals may be distinguished by
 means of it; assertions which are very doubtful.*

                          CERUMINOUS GLANDS.
   The ceruminous glands are situated beneath the integument  of the
 deeper part of the external meatus of the ear.   Thev occur mixed up
 with numerous  sebaceous glands, but  have no direct communication
 with these, as they open on the surface by distinct  apertures.
   They resemble very closely in structure  the  sudoriferous  glands
 just described, consisting, like them, of convoluted and looped  tubes,
 which unite together and end in a slender duct.   They  differ, how-
 ever, from the sudoriferous glands in the fragile character of the tubes.
 which renders it somewhat difficult to procure a  perfect preparation
 of one of them; this difference seems to arise principally from the
 absence, in a great measure, of fibrous tissue, whereby, in the  sudor-
 iferous glands,  the  tubes  are  bound  together,  as well  as  of also
 enveloping plexuses of blood-vessels.   (See Plate  LVII. fig. 5.)
   In the external ear of the sheep, in which these  glands  may  be
 studied to  great advantage, the tubes  appear of a pale straw-colour,
 transparent and glossy,  with  but  few apparent  granular cells, and
 these totally different from  the characteristic cells of the sebaceous
 glands, filled with innumerable globules  of oil.   The granular cells
 filling the tubes,  and which are usually concealed by a quantity of oily
 fluid, may be made apparent by the addition of acetic  acid.   The mem-
 brane of the tubes is composed of a nucleated form  of elastic tissue.f
  * Annates d'Hygvne, vol. i. ii. x. &c.
  f It seems doubtful, after all, whether the ceruminous are any thing more than a
variety of the sudoriferous glands. 
442
THE  SOLIDS.
   From the fact of the ceruminous glands coexisting with numerous
 sebaceous  glands, it seems probable  that the cerumen is the mixed
 production of the  two descriptions of glands.

                              KIDNEYS.
   The substance of the kidney, like that of the other large glands, may
 be divided, for the purposes of description, into two orders or systems
 of structure  or apparatus:  the  glandular or secretory, which is  the
 most important and  characteristic;  and the vascular, which is  but
 subordinate.
                       Secreting Apparatus.
   The secreting apparatus of the kidney consists of the  tubes; their
 enlarged and globular extremities, which,  in  part, constitute  those
 peculiar and  interesting  structures, the Malpighian bodies, and their
 contained  granular cells.   (See Plate LVIII. figs. 1. 6; Plate LX.
figs. 2, 3.)
   Tubes.—The substance  of the  kidney  is divided  into an  outer
 cortical  and an inner  or medullary part.   The  former is  generally
 conceived  to be the secreting  portion of the kidney, and  the  latter
 merely the tubular or  conducting  portion  through which the  urine
 passes in its way to the ureter.  This notion of the nature of the two
 parts and of their  mutual relation is certainly erroneous, as is proved
 by the facts that both portions of the kidney are alike formed of tubes,
 and  that all these tubes are abundantly furnished with  secreting cells.
   The secreting structure of the cortical part of the kidney is distin-
 guished by the large size of its tubes;  their tortuous course; the loops
 formed  by them, not  merely on the surface of the kidney, but also in
 its interior; by the globular enlargements in which they terminate;
 and  by the larger size, &c, of their contained cells.
   The medullary part  of the kidney  is characterized  by the smaller
 calibre of its tubes, their straight course, the absence of dilated extrem-
 ities, and the frequency of the union of the tubes with each other.
   The tubes, then, of the kidney, describing their course from without
 inwards, commence in dilated  extremities  (see Plate LX.figs.  2, 3),
 which form part of the structure of the Malpighian bodies; they  after-
 wards take  a tortuous  course, describing loops on the surface of  the
 organ, as well as in  its  interior (see Plate LIX. fig. 2, and  Plate
 LVIII. fig. 1), until they  reach  the medullary part, when their course
 becomes straight,  and where they frequently unite, especially near its
 lower portion, in a dichotomous manner, thus forming a number of 
GLANDS.
443
larger tubes, which terminate in the mammillary processes which dip
into the midst of the chambers  called calices.
  According to the above description of the course and origin of the
tubes of the  kidney, which is  now the generally received one, each
tube commences in a single dilated extremity; it seems to me, how-
ever, to be probable that many  of the tubes have their origin in loops;
the fact of the occurrence of loops throughout both the medullary and
the cortical parts of the kidney, the  universal formation of loops on
the surface of that organ, and the non-existence of dilated extremities
of tubes on that surface, all tend to prove the correctness of the view
just mentioned.
   The tubes of the kidney, wherever encountered, consist of a strong
and structureless basement membrane (see Plate LVIII. fig. 1);  it is
worthy, however,  of especial notice that these tubes, as well as  their
globular terminations, are all enclosed in a frame-work constituted of
a nucleated form of elastic tissue.   This frame-work is seen to most
advantage in cross-sections; this it is which keeps the tubes distinct
from  each other,  and  which  explains  the  occurrence of intervals
between  the tubes, seen  especially  in  longitudinal  sections.   (See
Plate LVIII. fig.  2.)
   Malpighian Dilatations.—It is certain that some,  if not all, of the
tubes terminate in enlarged extremities.  These dilatations constitute
the Malpighian  bodies in part only; they are of a globular form, and
their diameter exceeds  five or  six times  that of the tube itself.   (See
Plate LX. figs. 2, 3.)   They vary, however, considerably in size, in
all parts of the  cortical substance of the kidney; and Mr. Bowman
states that they  are largest near to the point  of junction between the
cortical and medullary portions.
   The best way to obtain a satisfactory view of these bodies is to tear
up with needles a fragment of the cortical substance of the kidney,
and to search among the divided shreds for the Malpighian dilatations,
which are there met with in all  possible conditions.  Some will be
seen entirely detached,  lying loose in the water in which the fragment
has been torn up, others will be observed to be attached to the tubes
which take their origin from them.   All of  these, however, whether
attached or loose,  will occur in one of two states; either  the surface
of each will be seen to be constituted of convoluted and branched tubes,
the vessels of the Malpighian plexus; or it will appear perfectly smooth
and even.  The former condition is the more frequent;  the latter is
by far the less common, and is explained by the fact  that in this case 
444
THE  SOLIDS.
 the Malpighian dilatation is enclosed in a capsule of fibro-elastic tissue
 of considerable thickness, a continuation of that  which invests  the
 tubes themselves.   (See Plate LX.figs. 2, 3, and Plate LVIII. fig. 2.)
   The Malpighian dilatations rarely, if ever, extend to the surface of
 the kidney; they have been, in all the  instances in which they have
 been noticed by the author, covered by convolutions of the tubes.
   Epithelium.—The epithelium  of the kidney presents several well-
 marked modifications, in different localities of that  organ.
   The epithelium  of the tubes of the cortical part of the kidney, save
 within a short distance of their junction with the  Malpighian dilata-
 tions, is  composed of large and angular scales or cells, which  are
 coarsely granular,  and which form a regular layer of pavement epithe-
 lium lining the tubes; the centres of these are unoccupied with cells,
 and  are thus left pervious for  the passage of the urine.   (See Plate
 LVIII.  fig. 6.)
   The cells forming the epithelium of the tubes  of the medullary part
 of the kidney are  of much smaller  size than those contained in  the
 tubes of its cortical substance, consisting of nuclei, surrounded by a
 very narrow border.  (See Plate LVIII. fig. 6.)
   The cells situated at  the neck  of the Malpighian dilatations are of
 the ciliated kind:  these were first noticed by  Mr. Bowman  in  the
 kidney of the frog, and that gentleman  conjectured their  existence in
 the higher animals; the author has seen them in action in the sheep,
 rabbit, and horse.   (See Plate LX. fig. 3.)
   Lastly,  the cells which invariably line the Malpighian dilatations of
 the tubes  are small, and furnished with oval nuclei.   (See Plate LX.
fig. 3.)   Mr. Bowman considered that  epithelium was not constantly
 present  in these bodies; and that, when it was so, it only lined that
 portion of them in connexion with the tubes.   This statement arose
 in a misapprehension of the  real structure of the Malpighian body.

                       Vascular Apparatus.
  The vessels of the kidney  consist of the renal artery and vein; also,
 of a vein  which may be called portal:  we will  first trace the course
 of the artery.
  Renal Artery.—The  renal artery, after its entrance into the sub-
 stance of  the kidney, divides into numerous  branches, some of them
 pass between the  medullary cones,  others  traverse these  in sets:
 arrived  at the  cortical  part  of the kidney, many undergo a  further
 sub-division, and some,  passing  towards the  Malpighian dilatations, 
GLANDS.
415
form in part, upon its external surface, the Malpighian tuft or plexus
of vessels (see Plate LIX. figs.  1.5); others continue onwards to the
surface of the kidney, and there terminate in capillaries.   (See Plate
LlX.^g-. 2.)   Such is a brief sketch of the course of the renal artery.
   The branches of the renal artery take, through the cortical part of
the  kidney, a straight and parallel course; some of these branches
give off lesser vessels on  each side, which pass towards,  and  are
expended upon the Malpighian dilatations, as also are, ultimately, the
terminations of the main vessels from which the lesser ones proceeded.
Others, again, of the larger  and  parallel branches, in like manner give
off  Malpighian twigs;  but their terminations,  in  place of being
exhausted upon the  Malpighian  dilatations,  reach  the surface,  and
there form,  with  the branches  of the  renal  vein,  an  inter-lobular
plexus.   It is seldom that a branch of the artery reaches  the surface
of  the  kidney, without  first communicating with the  Malpighian
dilatations.
   Renal  Vein.—The renal vein has two origins: one in  the capilla-
ries on  the surface of the kidney;  these capillaries, uniting with those
of the renal  artery, form the plexus,  which ramifies  in the interstices
left between the terminal loops of the tubes (see Plate LIX.  fig. 2);
the second origin  is in the plexus of capillaries surrounding the tubes
formed  by the junction  of the capillaries of  both  artery and vein;
from these two origins and  plexuses branches proceed; these, uniting
with each other,  form  larger vessels, which also  pass through the
medullary part of the kidney in sets.  (See Plate LVIII. figs. 4, 5.)
   Portal  Vein.—Each Malpighian tuft or plexus of vessels is formed,
like  other plexuses, of capillaries derived in part from an artery  and
in part from  a vein.  As  a single  arterial  twig proceeds  to each
Malpighian dilatation—the  afferent  vessel, so a single venous  twig
departs  from it—the  efferent vessel;  this vessel is  usually  of much
smaller  size than  the artery, and terminates in the  capillaries which
encircle the uriniferous tubes.   (See  Plate LX. fig.  2.)
  The efferent  vessel of the  Malpighian  tuft resembles in its origin
and  distribution the  portal  vessel of the liver, being in connexion
with capillaries, at both its origin and its termination: in consequence
of this  resemblance,  it has  been termed by Mr. Bowman the portal
vein of the kidney;  and as each Malpighian plexus has a  separate
efferent vessel, to  the  aggregate of these  that gentleman applies the
term "portal system" of the kidney.
  The above  description  of the  vascular distribution belonging to the 
44G                      THE  SOLIDS.
kidney  differs, in some important respects, from  that given  by Mr.
Bowman, as we shall now proceed to make apparent.
   In the first place, Mr. Bowman describes the afferent vessel of the
Malpighian tuft as piercing the membrane of the enlarged extremity
of the tube, and as forming within this, by its numerous sub-divisions,
the Malpighian plexus: the efferent vessel, in like manner, perforating
the membrane of the dilatation, or proper capsule.
   This view of the position of the  Malpighian plexus is undoubtedly
incorrect; this plexus, like  every other plexus belonging to glands
formed  on the tubular or follicular types,  is situated on the external
surface of the basement  membrane, that is, embracing  the  globular
head of the tubes, and lying between this and the frame-work of elastic
tissue  already described.  Analogy, therefore, is entirely opposed to
the description of the author of the paper in the Philosophical Trans-
actions to which reference has been made more than once.
   In the  second place, Mr. Bowman describes the renal artery as
being spent upon the Malpighian bodies, with the exception of a few
branches  given  off to the coats of the excretory ducts and of the
larger vessels; while, according to  the  author's observations, only a
proportion of the branches of the renal artery are thus disposed of.
   The accuracy of  the foregoing account of the distribution of the
blood-vessels of the kidney is borne  out, to a very great extent, by
the results furnished by injection.
   1st.  The Malpighian plexus can be injected  with great facility by
the artery, but not by the vein:  the reason of this will be obvious on
a little reflection;  the branches of the renal artery pass directly to
the Malpighian plexus; those of the renal vein, commencing from the
larger  or  terminal trunks, end either in the  plexus surrounding the
tubes of the kidney, or in that which lies on  its surface  between the
convolutions of those tubes; and it is in one or other plexus that the
efferent or portal  vein of the Malpighian tuft terminates;   so that
between the terminal branches  of  the  renal  vein and the origin of
the efferent vessel, a complicated plexus is interposed—that surround-
ing the  uriniferous tubes;  the injection,  therefore, before reaching the
Malpighian tuft, would have to traverse the plexus already spoken of;
and it is this which accounts for its being so difficult, if not impossible,
to inject the Malpighian plexus from the renal vein.
  2d. The plexus surrounding the tubes may be injected with care,
from both the artery and vein; but especially  from the latter.
  3d. The plexus, ramifying  between  the  loops of the tubes on the 
GLANDS.                          447
surface of the kidney, may also be readily injected from either artery
or vein.
   Occasionally, the injection will pass from the blood-vessels,  and
escape  into the tubes, or their Malpighian extremities.
   The  tubes  themselves, and very rarely their globular terminations,
may be injected from  the ureter: this is accomplished more readily
in the kidneys of some animals, as the horse, than in those of man.
   A complete Malpighian body, then, consists of the globular enlarge-
ment of the tube, over which is spread the Malpighian plexus, formed
by branches of  the renal artery and  portal vein;  this plexus does not
consist entirely of capillary meshes, but of vessels of different diame-
ters; the artery divides and sub-divides: its  terminal branches are,
however, capillary in  size, but, in place  of forming  distinct meshes,
follow a serpentine and convoluted course.   (See Plate LX. fig. 2)
   Mr.  Bowman conceived, as already noticed, that the  Malpighian
plexus  was situated within the globular enlargement of the uriniferous
tube;  and, reflecting on  the remarkable structure of the Malpighian
bodies, and on  their singular connexion with  the tubes, was led to
consider that the tubes and  their plexus  of capillaries  are the  parts
concerned  in the secretion of that  portion of the urine to which  its
characteristic properties  are due  (the urea, lithic acid,  &c),  while
the Malpighian  bodies  are an apparatus destined to separate from the
blood the watery portion of the urine.
  "It would indeed be difficult," Mr. Bowman writes, "to conceive a disposition of
parts more calculated 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 of the velocity of the current of
blood.  The  vessels in which this delay occurs are uncovered by  any structure.
They lie bare in a cell from which there is  but one outlet, the orifice of the tube.
This orifice is encircled by cilia, in active motion, directing a current towards the tube.
These exquisite organs must not only serve to carry forward the fluid already in  the
cell, and in which the vascular tuft is bathed, but must tend  to remove pressure from
the free surface of  the vessels, and so to encourage the escape of their more fluid
contents.  Why is  so wonderful an apparatus placed at the extremity of each urin-
iferous  tube, if not to furnish  water, to aid in the  separation and solution of  the
urinous products from the epithelium of the  tube?"—P. 75.

   My view of  the  nature of the Malpighian body differs, in  some
respects, from that entertained by Mr. Bowman.   The  proper Mal-
pighian capsule is invariably lined by innumerable granular cells;  for 
448                      THE  SOLIDS.
this single and simple reason, therefore, I regard this body as a secret-
ing organ as much as the uriniferous tubes themselves, which present
an organization essentially  the  same.   I differ, therefore, from  Mr.
Bowman, who considers the epithelium  of the tubes as  the sole true
secreting agents of  the urine.   I conceive that this fluid is formed in
every part of  the tubular and Malpighian surface of the kidney, and
I dissent from the opinion that the Malpighian  body is  an apparatus
destined for the simple  separation of the watery parts  of the urine
apart from any act of secretion.
  Nevertheless, I so far agree with Mr. Bowman in his theory, as to
consider that  the greater portion of the more watery  parts of the
urine proceed from  the  Malpighian bodies; not, however, by an act
of simple separation, but by one of secretion.  The peculiar arrange-
ment of the blood-vessels, and the presence of ciliated  epithelium at
the entrance to the  tubes, are facts in themselves sufficiently conclu-
sive of  the accuracy of this view:  as, on the other hand, I conceive
the great extent of secreting surface presented by the tubes to be in
itself sufficient to prove  that at least a portion of the aqueous constit-
uent of the urine emanates from this surface.
  An accurate knowledge of the pathology of  the  kidney and urine
would,  doubtless, furnish arguments conclusive as to  the  relative
functions and  importance of the tubes, and their enveloping plexus
and the Malpighian bodies.
  The reader  will at once observe that one of the arguments in favour
of Mr. Bowman's theory, urged  in the preceding exposition, does not
hold good, in  consequence of its want  of accordance with the true
structure.   I allude to the supposed entrance of the plexus into the
cavity of the proper Malpighian  capsule.
  In birds  and reptiles,  the Malpighian plexus is  not  formed  of a
number of convoluted vessels, resulting from the repeated sub-division
of the afferent artery, as is the case in all the Mammalia, but  simply
consists of a single coiled vessel, so that the afferent and the  efferent
vessels of each tuft are one  and the same by direct continuity.   In
these  classes,  the  efferent vessel  readily  admits of being injected
from the artery, and this in consequence of the simplicity of the plexus
surrounding the Malpighian enlargement.
  The  size  of the Malpighian bodies varies, not merely in the same
kidney, but also to a still greater  extent in the kidneys of different ani-
mals: they are largest in  the elephant and horse, and smallest in birds. 
GLANDS.
449
                        Development of the Kidney.
   According to Dr Carpenter,  "The first  appearance of any thing resembling a
 urinary apparatus in the chick, is seen in the second half of the third day.  The
 form at the time presented by it is that of a long canal, extending on each side of
 the spinal column, from the region of the heart towards the allantois; and the  sides
 of these present elevations and depressions, indicative of the commencing develop-
 ment of ca3ca.
   "On the  fourth  day, the Corpora Wolffiana, as they are termed, are distinctly
 recognised,  as composed of a series of caecal appendages, which are  attached along
 the whole course of the first-mentioned canal, opening into its  outer side.  On the
 fifth day, these appendages are convoluted; and the body which they form acquires
 increased breadth and thickness.  They evidently then possess a secreting function;
 and the fluid which they separate is poured by the long straight canal  into the cloaca.
 Between their component shut sacs numbers of small points appear, which consist of
 little clusters of convoluted vessels exactly analogous to the Corpora Malpighiana
 of the kidney.   The Corpora Wolffiana, however, have only a  temporary existence
 in the higher Vertebrata, although it seems that in fishes  they constitute the  perma-
 nent kidney.  The development of the true kidneys commences in the chick about
 the fifth day.  They are  seen, on the sixth, as lobulated grayish masses, which sprout
 from the outer edges of the Wolffian bodies;  and they gradually increase, the tem-
 porary organs diminishing in the same proportion.  The sexual organs, as will be
 hereafter explained, also originate in the Wolffian bodies; and  at the end of  fetal
 life, the only vestige of the latter is to be found as a shrunk rudiment situated near
 the testes of the male.   The progress of development in the human  embryo seems
 closely conformable to the foregoing account.   The Wolffian bodies begin to appear
 towards the end of the first month; and it is in the course of the seventh week that
 the true kidneys first present themselves.  From the beginning  of the thud month,
 the diminution in the size of the Wolffian bodies goes on pari passu with the increase
 of the kidneys;  and at the time  of birth, scarcely any traces of them can be found.
 At the end  of the third  month, the  kidneys  consist of seven or eight  lobules, the
 future pyramids; their secreting  ducts still terminate in the same canal, which receives
 those of the Wolffian bodies and of the sexual organs.   And  this opens with the
 rectum into  a sort of cloaca, or sinus urogenitalis, analogous to that which is perma-
 nent in the oviparous Vertebrata.  The kidneys arc at this time covered by the supra-
 renal  capsules,  which are very large;  about the sixth month, however, these  have
 decreased, while the kidneys have increased, so that their proportional weight is as 1
 to 4i.   At birth, the weight of the  kidney is about three times that of the supra-
 renal capsules, and they bear to the whole body the proportion  of 1  to 80;  in the
 adult, however, they are no more then 1 to 240.  The Corpora Wolffiana are, when
 at their greatest development, the most vascular parts of the body next to the liver;
 four or five branches from the aorta are distributed to each, and two veins are returned
 from each to the vena cava.  The upper veins and their  corresponding arteries are
converted into the  renal and emulgent vessels; and the  lower, into the spermatic
 vessels.  The lobul;ited  appearance  of  the kidney gradually disappears; partly in
consequence of the condensation of the areolar tissue, which connects the different
 |)::rts;  and partly through t!>e development of additional tubuli in the  interstices."
                                    29 
450
THE  SOLIDS.
  It is  only necessary to observe, in addition to the description of
Dr. Carpenter, that, although  the development  of the kidney  com-
mences near to the Wolffian body, it is yet not formed out of it, but
has an independent origin in  its own proper blastema or  primordial
matter.   In its earliest condition in the Mammalia, it consists of  tubes
proceeding from  the hilus outwards towards  the circumference in
bundles; these tubes afterwards separate and become contorted, yet
all terminate in enlarged and vesicular extremities—the  Malpighian
bodies.   In the earliest state  in which the kidney can be examined,
the caeca alone exist in connexion with  short  tubes;  the  central or
proximal extremities are free, and not yet united  to the ureter.  This
fact proves that the kidney is not an involution of the genito-urinary
mucous  membrane, but an independent formation,  as is, probably,
every other gland.
  Such is a simple, concise, and, it is believed, in all essential partic-
ulars, a correct account of the  normal anatomy of the kidney.
  Reference to the various discrepant, contradictory, and  often erro-
neous statements of many writers on this  subject has been hitherto
purposely avoided, lest  such should obscure the simplicity of the
description just given.   A few of the more remarkable  statements
and opinions advanced respecting  the anatomy  of the renal organs
may now, however, be noticed with advantage and interest.
  Every statement, without exception, made by Mr. Bowman, one of
the earliest and very best writers on the  minute anatomy of the kid-
ney, has been  from time to time contradicted by  different  observers;
by others, again, the descriptions of that gentleman have been con-
firmed,  and not denied.  As might be readily imagined, the truth lies
not exclusively with either the denying or  the confirming observers.
  Thus, the reality of  any connexion existing between the tube and
the Malpighian body has been  questioned  and denied, and still con-
tinues to be so; as also the existence of  a  vibratile epithelium in the
upper portion  of the uriniferous tube.  The first  particular has  been
denied by Miiller,* Reichert,+ Gerlach and Bidder;  and  the second
has been doubted or denied by Huschke, Reichert, and Bidder.  On
the other hand, the observations  of Schumlansky,J and A.  Kolliker
  * "De Glandularum Secernentium Structura Peinitiori Earumque prima formatione
in Homine atque Animalibus, Commentatio Anatomica."—Cum Tabulis am.  incisis
xvii. Leipsise, 1830.
  f Bericht uber die Fortschrilte der Mikroscopischen Anatomic in dem Jdhre, 1842;
von K. B. Reichert, Prof, in Dorpat, Mailer's Archiv. 1843.
  \ "De Structura Renum," 8vo. 1788. 
GLANDS.
451
 of Zurich, accord with those of Mr. Bowman on the first particular,
 and those of Bischoff, Valentin, Pappenheim, Gerlach, and  Kolliker,*
 on the second, the latter observer describing the entire epithelium of
 the tubes as ciliated.
   It is so easy, however, to satisfy ourselves, in  the  kidney of every
 animal, of the reality of a connexion between the tube and the  Mal-
 pighian body, as well as of the presence of a ciliated epithelium, in
 the upper portion of the uriniferous tubes, that it would  be perfectly
 unjustifiable for observers  again to call these two points  in question.
   The statement of Mr. Bowman which has met  with most opposition,
 is that made as to the entrance of the Malpighian capillary plexus into
 the cavity of the true capsule.   Some observers  have denied the cor-
 rectness  of  this description, on the simple ground of the anomalous
 position in which the blood-vessels would be placed, were  such an
 arrangement the true one.   This objection, however, is insufficient to
 disprove the accuracy of Mr. Bowman's explanation,  since in the liver
 there  is every reason to believe that  the vascular and secreting ele-
 ments  of glands are  intimately associated.   Again, some  observers,
 not satisfied with Mr. Bowman's description, have given others.
   Thus, Gerlachf says that the  Malpighian capsule is  not, as  Mr.
 Bowman described it, a blind termination of a uriniferous duct, but a
 retraction or introversion, a diverticulum  of the same  structureless
 membrane which  forms the uriniferous tubes; also, "that when the
 Malpighian  capillary net-work is  closely examined, after the capsule
 has been  entirely detached from it,  we see  it in its whole extent
 covered by a thick layer of nucleated cells, which are continued from
 the  inner wall of  the capsule  upon the Malpighian  vessels; and the
 latter  lie  introverted within a  layer of cells, like an intestine within
 the peritoneum."!
   Gerlach's  description is assuredly  incorrect: the  views  of the
 structure  of the Malpighian body, entertained by Bidder,§ although
 they approach more nearly to the  truth, are  also inaccurate: he con-
 siders  that  the glomerulus, or vascular plexus, is inserted  or pushed

  * Ueber Flimmerbewig-ungen in den Primordial Nteren, Archiv. fur  Anatomic,
 Physiologie, und Wissenchaftliche Medicin, Heft V. S. 518.  1845.
  f Beitrdge  zur Slruclurlehre  der Niere, von Dr. Joseph Gerlach, prakt in Mainz
 (Mayence),  Mailer's Archiv. 1845.
  I Edinburgh Medical and  Surgical Journal, October, 1847.
  5 Ueber die Malpighischen Korper  der Niere, von  F. Bidder  in Dorpat, Miiller's
Archiv. 1845. 
452
THE  SOLIDS.
 into the expanded  portion of the uriniferous canal; this on its part
embracing and surrounding the glomerulus.  According to this  view,
the glomerulus would  still be external to the cavity of the dilated
extremity of the tube, the relation between the two being comparable
to the head within the  double night-cap.
   The correct view of the structure of the Malpighian body is, how-
ever, much more  simple  than either  of those  just described.   A
Malpighian body, as already stated, consists of the dilated extremity
of a uriniferous tube,  over which is spread the  Malpighian  plexus:
these two  structures viz:  the dilatation  of the uriniferous tube, and
the vascular plexus, constitute all that is  essential in the anatomy of
the Malpighian  body:  both are enclosed in a thick capsule: this is
not, however,  a  structure peculiar to the Malpighian body, but a mere
envelope, similar to, as well as a continuation of, that which invests
the tubes themselves.
   A little reflection will  show that  this view reconciles  many of the
conflicting statements  made in reference to the anatomy of the Mal-
pighian body.   The outer capsule referred to, which is that spoken ol
by most  other observers  as the true Malpighian capsule, is evidently
that which Mr. Bowman had in view as the dilated extremity of the
uriniferious tube, and it is this which he described as being pierced by
the Malpighian artery—a description literally and  positively correct.
   The common envelope, which, however, as already stated, forms
no necessary part of the Malpighian body, is  really pierced by both
the afferent and efferent vessels of  that body, as well as by the  tube.
(See Plate  LX. fig. 3.)    Mr. Bowman's  error consists in having
regarded this mere outer covering as the true dilated extremity of the
uriniferous tube, which it most certainly is not, and in having neces-
sarily,  as a consequence, overlooked the  true  extremity of the urin-
iferous tube with its contained epithelium.
   Again, the confounding of this common envelope with the true Mal-
pighian capsule  accounts for  the assertions of those observers  who
state that the  uriniferous tube has  no connexion with that capsule:
it  has,  indeed, no connexion by  continuity; it simply pierces it: of
the inner  or  true   capsule, the uriniferous  tube is   absolutely  a
continuation.
   The common  envelope of the entire and perfect Malpighian  body
differs structurally from the true capsule:  the latter is thin and struct
ureless;  the former, thick, and constituted of a delicately fibrous and
nucleated form of elastic tissue. 
GLANDS.
453
  Mr. Toynbee* is  the only writer, with whose observations I am
acquainted, who understands the true character of what is ordinarily
regarded as the  "capsule of the Corpus Malpighianum:" this he cor-
rectly describes as being a distinct globular investment, and not, as
was supposed, an expansion of the tube.
  Notwithstanding, however, the knowledge of this fact, Mr. Toyn-
bee's  views of the structure of the  Malpighian body appear to me to
be far from correct.
  Thus, Mr. Toynbee describes the  Malpighian body as "composed
of two distinct elements—a plexus of blood-vessels, and a membranous
capsule, which completely surrounds  and envelopes the plexus."
  Each  Malpighian  body is indeed composed of two  distinct  and
essential  elements, the  dilated extremity  of the uriniferous  tube
embraced  and  surrounded  by  the  Malpighian  plexus:  the outer
investment, called by Mr. Toynbee  and others "the capsule," is not a
structure essential to the Malpighian  body, since it alike invests this
and the uriniferous tubes for  its whole length attached to it.
  Again, Mr. Toynbee  describes  the uriniferous  tube, after pene-
trating the  capsule, as twisting into-a coil, and after being in contact
with  the ramifications of the corpus, as emerging from the capsule.
  This last  statement shows that Mr. Toynbee was  unacquainted
with the  proper character of the  most important and essential of the
two elements of the Corpus Malpighianum, viz:  the dilated extremity
of the uriniferous tube, filled  with its secreting cells.

                            Pathology.
  The kidney would appear to be more liable to morbid  alterations
than  any other  organ in the  body; nevertheless, its pathology is still
far  from being  completely understood, notwithstanding that several
observers have paid especial  attention to the subject.   Several of the
pathological conditions of this organ  appear to have been confounded
together  under the common term "Bright's Disease."
  A very frequent pathological condition of the secreting cells of the
kidney is that in which they are  laden with  globules of an oily fluid,
similar to those which occur in the hepatic cells in the affection com-
monly called fatty liver, or fatty degeneration of the liver, but which
would be more correctly distinguished by the appellation of oily liver;
  * "On the Intimate Structure of the Human Kidney, and on the changes which its
several parts undergo in Bright's Disease."  By Joseph Toynbee, F. R. S.—Medico-
Chirurgical  Transactions, June 1846. 
454
THE  SOLIDS.
the corresponding affection  in  the renal organ being  known by
the name of oily kidney.
  It is this condition of the renal cells which, in Dr. George John-
son's* opinion, constitutes the true Morbus Brightii.
  The large, smooth, and mottled kidneys  are those in which the oily
matter abounds; the  smoothness, according to Dr. Johnson, depend-
ing upon the uniform distribution  of the  tubes in the cortical portion of
the kidney with the oily matter.
  The wasted and granular kidneys, according to the same observer,
are those in which the accumulation  of fat takes place less rapidly
and less uniformly; certain  of the convoluted tubes becoming dis-
tended with fat, forming prominent granulations;  and these, pressing
upon  the surrounding tubes and vessels, occasion their obliteration
and atrophy,  a wasting and contraction of the  entire  organ being the
result.   This condition attends the more advanced stages  of Bright's
Disease, and is the sequence of the first-described form of the affection.
  Dr. Johnson, from numerous examinations, has arrived at the inter-
esting and important conclusion,  that the oily disease  of the kidney is
generally coexistent with a  similar affection  of the  liver, and even
with steatomatous  deposition in the coats of the arteries, and to a
less extent with tubercular deposit in the lungs.
  Dr. Johnson also maintains the opinion,  that the oily deposition is
not preceded  by  any inflammatory or  congestive stage:  congestion
accompanies  the disease; but this may be either active  or passive,
and when the latter, is produced  by the pressure to which  the vessels
are subject in consequence of the distention of the epithelial cells, and
which pressure gives rise to  the  effusion of serum and blood within
the tubes.  These results are, however, the effects, and not the cause
of the disease.
   The dropsy ensuing on scarlet fever, Dr. Johnson  considers, does
not depend upon the presence of oil in  the cells of the kidney;  this
dropsy he regards  as the result partly of the  cutaneous disease, and
partly of  the effort made by  the kidneys to relieve the skin, the cir-
culation and functions of which are so much impaired.
   From  experiments made  on cats, it appears that  confinement in
dark chambers has the effect of inducing granular disease  of the kid-
ney, accompanied by deposition of oil in the urine.
  * "On the Minute Anatomy and Pathology of Bright's Disease of the Kidney, and
on the relation of the Renal Disease, to those Diseases of the Liver, Heart, and
Arteries with which it is commonly associated." George Johnson, M. D.—Medico-
Chirurgical Transactions, 1846. 
GLANDS.
455
    Dr. Johnson regards the existence of albuminous urine as  quite a
 secondary effect.
    The results  of Mr.  Toynbee's investigation on the  pathology of
 Bright's  Disease are very different, as we  shall  presently  perceive,
 from those of  Dr. Johnson:  both  observers,  however,  agree  in the
 statement  that there can be no doubt that albuminous urine often
 exists, without  any deposition of fat in the epithelial cells of the kid-
 ney; as in dropsy after scarlatina.
    The following is Mr. Toynbee's  own exposition  of his researches
 on the pathology of  Bright's Disease:
   " The First Stage of the Disease.—In this stage the kidney is enlarged, and innu-
 merable black points are visible, which are the corpora Malpighiana dilated, and their
 vessels distended  with blood, seen through the capsule.  The white spots, which
 derive their appearance from the collection of fatty matter, begin to be perceptible.
   "The peculiar features of this stage consist of an enlargement of the arteries enter-
 ing the corpora Malpighiana; the dilatation of the vessels of the tuft, the capillaries
 and the veins; an increase in the size of the capsule of the corpus and of the tubuli,
 and a large addition to the quantity of the parenchyma of the organ.
   "The condition  of the arteries is visibly changed, even at this early period;  the
 artery entering the corpus being actually twice or thrice its natural  size;  which is
 the case also with  the Malpighian  tuft,  and  the capillary vessels which spring from
 the tuft.  An injection, in this stage, cannot very easily be made to pass through the
 tuft, and fill the capsule of the corpus—a circumstance which almost always attends
 injection in the later stnges of the disease.
   " The capillaries and veins are greatly enlarged, giving to the surface of the organ
 the resemblance of net-work.  This is the commencement of the stellated condition,
 which is so marked a characteristic  of the next stage of the complaint.
   "The tubuli in this stage are also much increased in their dimensions;  but the fat
 which is found in them is soft and white.
   " The Second Stage of the Disease.—The organ  in this stage  is very greatly
 increased in size, its surface is smooth, and presents numerous white spots; the cap-
 sule is but slightly adherent to the surface,  and the tissue of the organ is  flabby.
   "The structural  changes exhibited during this stage are the following:
   " 1st. The  artery of the corpus Malpighianum becomes so greatly enlarged, that
 frequently it equals the dimensions of the tube itself,  and is eight or ten times its
 natural size.  It is tortuous and dilated, and sometimes, previously to entering  the
 capsule of the corpus, presents swellings analogous to those  of varicose veins.  The
 primary branches of it, in forming the tuft, are also distended to ten or fifteen times
 their natural size, and are not unfrequently discovered external to the capsule of the
corpus, as though thrust out by some internal force.   The vessels forming the tuft
are likewise enormously enlarged, and very often the minutest branches are fully as
large as the main artery of the corpus in a healthy state.
  " Occasionally the tuft is broken up, and, instead of forming a compact mass, exhib-
its its individual branches separated from each other.  At other times the branches
of the tuft arc actually larger than the primitive artery of the corpus.  Under these 
456
THE  SOLIDS.
circumstances it is singular that Mr. Bowman should have made the following remarks
'Though I have examined with great care many kidneys at this stage of the complaint,
I have never seen, in any instance, a clearly dilated condition of the Malpighian tuft
of vessels:' he adds, 'on the contrary, my friend Mr. Busk, an excellent observer, has
specimens which undoubtedly prove these tufts not to be dilated in the present stage:
and I possess injected specimens showing them in all stages, but never above their
natural  size.'—It is very possible that the  peculiar injection used by Mr. Bowman
may account  for the fact which he mentions; and this conjecture is  rendered  ex-
tremely probable, as in the later stages  of the disease, the Malpighian  tuft becomes
pressed upon by the adipose accumulation within, and, after undergoing compression,
will  permit the fluid used in the process  of double injection to pass  through rather
than  yield and distend.  There  are  instances, again, in  which  the tufts  are  not
enlarged, but appear healthy, even in organs otherwise extensively diseased: but it
is important to add  that these tufts, both in the second and third stages, when  but
slightly enlarged, or even not  enlarged at all, will offer free passage to the injection,
on the most gentle  pressure, without even distending the whole of their vessels, and
thus indicate their diseased condition.
  " An  enlargement of the renal arteries and dilatation of their branches, are also
observable in this stage of the disorder.
  "The capsule of the corpus, too, is in this stage very greatly increased in size, and
during the process  of  injection  becomes frequently filled with the injection thrown
into the arterial system.
  " The tubuli differ considerably from their healthy condition,  being enlarged to
two or three times their natural size, and aggregated together in masses, so as to lie
in contact with  each  other,  and form definite, roundish  bodies:  they  are  also
extremely convoluted with  numerous dilatations: frequently thev are varicose.  At
other times they present distinct aneurismal sacs, which bulge out from one part of
the wall of the tube, to which they are  attached by a  small neck or  pedicle.  Occa-
sionally, some of the vessels of a convolution are smaller than the, others, and their
size nearly natural.   The tubuli in the masses are so closely packe'd  that the blood-
vessels are evidently compressed, and rendered incapable of admitting an injection.  At
times, a tube, even at some distance from the corpus, becomes very convoluted  and
knotted into a mass.
  " Parenchyma.—In cases where the kidney is much enlarged, the parenchymatous
cells will be found not merely increased in size, but adipose deposition will be visible
throughout them.
  " The Third Stage of the Disease.—The  kidneys are smaller than  their natural
size;  hard, white granules  are prominent on their surface, which is  more or  less
lobulated; the capsule  is adherent; vesicles  of large size are frequently every where
interspersed, and numbers  of smaller ones  stud  the whole  surface.   On making a
section, the organ is found  to be deprived of blood;  the cortical part contracted, the
blood-vessels large  and their walls thick.
  " Arteries.—The arteries  are in a more contracted condition than that described in
the second stage; and the Malpighian tuft is often so changed from its natural state,
that the greater part of its vessels are not capable of being injected.
  " The capsule of the  corpus  has assumed a more contracted appearance.
  "The arteries in this stage are so difficult to  inject, that some anatomists have 
GLANDS.
457
denied the possibility of the operation.  The difficulty has its  origin in the great
pressure, which is exerted on the whole of the arterial system, by the contraction and
hardening of the organ.
  " Veins.—The veins in this stage present, on the surface of the organ, the well
known stellated aspect which arises from the gradual pressure exerted on the trunks
and the contraction of the organ.
  " Tubuli.—The tubuli are larger than in the preceding stage, and are gathered into
rounded masses, which form  the granules on the  surface  of the organ.  The latter
are of a white hue, and are  most commonly fully distended with fatty depositions;
though not unfrequently they appear like dark spots; the tubuli, in that case, being
full of blood.  A rounded appearance  is generally characteristic of the granules, in
each of which the component tubule forms innumerable convolutions.  It is extremely
difficult to inject the tubuli from the ureter; indeed, it is very rarely that it is possible
to distend them from this source; nor is it an easy matter to fill them from the artery,
though, as will be  seen by the drawings, my efforts  have  not been without success.
  " The tubuli are filled with oily cells,  granular matter, particles of various sizes, and
blood globules.
  " Parenchyma.—The parenchyma is  hard, and is composed of elongated stellated
cells, from the angles of which fine threads proceed, and communicate with each other."

   The  researches  of Mr.  Simon and Dr.  Johnson, which appeared
simultaneously in the " Transactions of the Medico-Chirurgical Soci-
ety" for  1847, have  brought to  light  other facts in  the pathology of
the  kidneys.   It is  proposed in the  next  place to give an abstract of
the  observations of each of these  observers, couched, as  far  as  possi-
ble, in the language of the  authors.
   Mr. Simon's  paper is entitled  "On Sub-acute Inflammation of the
Kidney."

  "Without dwelling on those  excessively  rare cases, where  idiopathic nephritis
(independent of tubercles or of calculus) may, by its mere intensity, have ended in
large suppuration or (almost uniquely) in gangrene, I may state that, in  an  infinite
majority of instances, inflammation of the kidneys is sub-acute.   It depends on some
humoral derangement of the entire system, and commences as functional excitement
manifest in an act of over-secretion.  The morbid material which thus stimulates the
kidney in  its struggle for elimination  will  sometimes consist of products of faulty
digestion—the lithates or the oxalates; sometimes of matters cast upon the kidney
in consequence of suppressed function  in other organs—the skin, or the liver; some-
times will be the mysterious ferment of a fever poison—typhusfor scarlatina.  In these
several cases, whatever variety may exist in the detail of their causation, the essential
symptoms during life, and the essential anatomical changes, are strictly identical  in
kind.  They vary only in degree.   The maleries morbi seeks to effect its discharge by
means of an increased activity in the secreting functions of the kidney: it stimulates
it; and the result of the stimulation is not so much an increase of the watery secre-
tion as it is an  augmented cell growth  in the tubules of the gland- This accel-
eration of function is  incompatible  with maturity  of  the  secreted  products; the 
458
THE  SOLIDS.
epithelial cells undergo various arrests or modifications of development, and become
more or less palpably imbued with evidences of inflammation.
  "If attention happen to be directed to the state of the urine, that fluid will be found
to present manifest signs of derangement.  Microscopical examination will show in
it numerous  nucleated cells, which, in the hurry of over-secretion, have descended
from the urinary tubules.  Many free cytoblasts will likewise generally present them-
selves, together with  a variety of those  indefinite shapes which are known to  the
Morphologist as abortions of cell-growth, and which constitute a series of connecting
forms between the pus globule and the healthy gland cell.  Mingled with these, in
greater or less quantity, will be noticed also those remarkable fibrinous threads first
described by Dr. Franz Simon in connexion with renal disease.  They are seen  as
exceedingly delicate, almost perfectly transparent and colourless cylinders, often con-
taining in their mass some of the cell forms just enumerated, or, not unusually, a few
blood discs, resulting  from haemorrhage into the tubules.
  "On several occasions, where  the  renal irritation has been gouty, I have seen
crystals of lithic acid thus entangled in fibrin: in other  cases, though far less fre-
quently, I have distinguished crystals of oxalate of lime similarly  enveloped.  It is
well known that these little cylinders are fibrinous moulds  of the  inflamed urinary
tubules, some of the  other contents of which they bring with them in their descent.
They are thus quite as characteristic of the disease they attend as croupy expectora-
tion is of tracheitis; and the cells or crystals included in  them often afford the most
valuable therapeutical indications.
  " If patients chance  to die while their urine is  first furnishing the signs enumerated,
it will often happen that the kidneys, in their general appearance, present no marked
deviation from healthiness.  Their cortical substance may, indeed,  show the  minute
blood dots of intra-tubular haemorrhage;  or, more rarely,  may present here and there
a pin-head abscess.  But often, perhaps most often, a superficial observer would pro-
nounce the kidneys healthy; and, unless previous knowledge of the albuminuria had
existed, they would receive no farther attention;  or the Case-Book might contain that
vaguest of all vague records—' slight congestion of the kidney.'
  "On minuter  analysis,  however, the microscope will  reveal  a  large  amount  of
disense.  The ultimate tubules are found, as one might anticipate, gorged with  an
uneliminable excess of crude and vitiated secretion.  Blood and amorphous matter, and
an infinite range of cell-growth, from pus globules to the healthy germination of the
gland, present themselves in various combinations; and among them shape or colour
will sometimes enable us to discern the specific cause of  the derangement—crvstals
of lithic  acid or of oxalate  of lime, or the ochreous tinting of bile.  By products
such as these the  tubes are plugged, irregularly distended, and  not unfrequently
burst and  annihilated.  So  close is the  compaction  of material, even in manv  of
those tubes that have no shaped inflammatory products  within them, that they are
plainly impervious; and it is only by artificial means—by further tearing of the frag-
ment, or by use of chemical agents, that we can satisfy ourselves that the dense plug
in question consists but of agglomerated gland cells.
  "Now, in the post mortem  examination of these chronic cases,  we may or may not
find the  kidneys materially contracted and deformed.  It happens, to say the  least,
very frequently that the organ has preserved its full size, and presents the ordinary
colours.  Perhaps  it may have a cyst or two on its surface.  Between such kidneys 
GLANDS.
450
and those which are all knobbed and puckered and wrinkled, there is not the essen-
tial difference which first sight would suggest.  I shall first detail the changes which
are latent in the healthier-looking  kidney,  and subsequently  shall  consider the
anatomy of the  contracted specimens,  and analyze the circumstances which deter-
mine that apparent atrophy of the gland.
  "In the first instance, then: In commencing the microscopical  examination of the
cortical substance, we partially find a similar  state of tubes to that described in con-
nexion with  the sub-acute attack—a state, namely, of unequal distention and  of
blocking up by their  own accumulated products.  In the cases which have lasted
a long time, these products will often be  found to have undergone material altera-
tions, from the combined effects of pressure and absorption.  The contents of the
epithelial cells will have lost  much of their natural fine granularity; so that the cells
will appear, even when viewed singly, to have acquired a marked increase of solidity
and substance.   But, more than this: in many parts hardly a trace  of tubularity will
be found;  the tubes have been burst; their contents have been interfused amid the
matrix and blood-vessels; and their debris  may be  found on  opposite sides of  a
preparation—here black and bloated, there pale and collapsed.
  " Between these trophies of disease there is a  new manifestation.  The interspace
is crowded with a  profuse development of cysts, apparently  foreign to the healthy
structure of the part.  They are of all sizes; some are visible to the naked eye;
some are of the magnitude of normal gland cells, T?o4™'} 0 0 6;  but the majority are of
an intermediate bulk, ^l™1^.  Even where smallest, they are distinguished by their
sharp outline; and the larger ones  are conspicuous by their roundness and trans-
parency, for all  above j$j^  have predominantly fluid contents.
  "To explain this very remarkable phenomenon, I  take leave  to  digress  for  a
moment  from the straight-forward pursuit of the inflammatory  changes.  Any one who
has made a dozen post-mortem examinations must have observed  cysts in the  kidney;
and there can be few  pathologists  who have not speculated on the origin of these
growths.   Their connexion  with chronic  obstructive  diseases of the  kidney being
notorious, some  observers have supposed  them  to originate in dilatation of the Mal-
pighian capsules; while others have referred them to distention of the urinary tubules.
They exhibit great variety in size; they are seen every day as small  as mustard-seeds;
they have been seen as large as cocoa-nuts.  Thus, they obviously range from a very
conspicuous largeness to a size at which the naked eye loses them.  On microscopical
examination of cysted kidneys, the same uninterrupted gradation of size is seen to
repeat itself. The  larger vesicles fill the  field of the microscope; the smaller ones
diminish progressively, so that scores of them may be in the  field at the same time.
  "A section of cysted kidney, carefully examined with a  sufficent magnifying power,
may show an astonishing number of these minute vesicles; a number quite dispropor-
tionate to that of the larger cysts visible to the  naked eye; so that, sometimes, by  a
single one of the latter class  seen on the surface of the kidney, I have found myself
guided to a disease which is  substantially a vesicular transformation of the ultimate
structure of the gland.  The smallest  cysts are simple nucleated  cells, of the same
size  (or  rather within the same limits of size) as the common secretory, or epithelial
cells of  the gland.  From these cells they seem to be distinguished  by their very
definite outlines, and by their transparent fluid contents:  but  a step further in micro-
scopical analysis shows that the distinction  ceases at this point.   They show no signs 
460
THE  SOLIDS.
of a specific origin; no germs can be found for them other than might equally belong
to epithelial development; it  seems as  though from the same germs—according, no
doubt, to varying influences—healthy gland cells  might grow, or these fluid-hold-
ing cysts.
  "Fuller investigation of the specimen reveals the following very suggestive fact:
the copious formation of cells occupies the place of tubes, holding their relation to
the vascular plexus of the gland; and, as one gets to the periphery of the portion of
gland thus transfigured, one  finds the  broken extremities of the  original tubules—
some empty and collapsed, others obstructed and often dilated with morbid accumula-
tion.  In some cases, this  obstructive material contains a large proportion of fat, or
consists of it almost entirely.
  " In short, in pursuing the minute anatomy of the cysted kidney, we are conducted
back to that same structural change which we found  in connexion with sub-acute
nephritis, and demonstrably dependent  on inflammatory processes; or sometimes we
are led to a change in some respects similar to this, associated with what is known as
the mottled condition of the kidney.
  "The pathology of cysted kidney may accordingly be traced in either of two direc-
tions; from its first causation, or from its extreme phenomena.   Following the latter
course, we have ascended to  a period in the history of cysts, in which they lie with
numberless  gland-germs amid the remnants  of broken tubules.  The unbroken
tubules around show no growth of such cysts in their interior; many are distended,
it is true, but not with cysts;  their distention is of a kind that we have already inves-
tigated—inflammatory, or perhaps fatty. From the smallness attained by the cysts, it
seems quite obvious to me, that they cannot commence in any transformation  of the
tubes themselves or of the Malpighian  capsules.  Accordingly, I  find the  same
theory suggested by this method of inquiry, as when the morbid change had been
traced descensively from its causes, viz: that certain diseases of the kidney (whereof
sub-acute inflammation is by far the most frequent) tend to produce a blocking up of
the tubes:  that this obstruction, directly or indirectly, produces rupture  of the limit-
ary membrane; and that then, what should have been the intra-tubular cell-growth
continues with certain modifications as  a parenchytic development.
  "During the growth of the cysts, they frequently  exhibit an endogenous formation
of cells which  line them as an epithelium.
  "If I  am right in my statement of facts, and if my theory of  the cyst-growth is
sound, then the early stages of the process are certainly points of great interest: for
no one accustomed to the interpretation of nature, can doubt the reparative tendency
of these  acts.   The effused gland-germs are the last phenomena of the original dis-
ease, and the first of the attempted compensation.   The transparent nucleated cysts,
with their clear, sharp outlines, are  not mere dropsical  epithelia;  but are organized
for  secretion into their own cavities, so  as at least to withdraw from the blood, if they
cannot eliminate from the body, the materials which fill them.
  " Returning  now to the traces of inflammation in  an uncontracted kidney, we have
yet to  ascertain the  condition of  its blood-vessels.  Numbers of the  Malpighian
bodies are extinct for all purposes of secretion: their vessels  obliterated, their cap-
sules wrinkled  round them; they are dwindled,  opaque and bloodless.   Sometimes
the contraction of the Malpighian bodies is secondary on that rupture  of their capil-
laries which Mr. Bowman has indicated as the source of intra-tubular haemorrhage; 
GLANDS.
461
which rupture, of course, may have arisen either in an augmented impulse of the
arterial stream which fills them, or in an impeded circulation through the venus plexus
into which they discharge themselves.  But rupture of the capillaries is not the only
cause of atrophy, to which these bodies are liable in the disease under consideration.
  The vascular tufts may be exposed to injurious pressure from materials accumu-
lated  in  their capsules.   Thus, 1 have seen  them flattened into a fourth of their
natural compass, while the remaining larger  portion of the capsule (probably con-
tinuous  with  an  obstructed  tubule)  has been distended with a colourless  and
transparent fluid.
  " Such is the minute anatomy of  a kidney, which, having suffused from sub-acute
inflammation, has  undergone, in consequence, no noticeable alteration of volume,
although having in its interior a very considerable new development.
  "If the pathology of the  uncontracted kidney be  rightly understood, that of the
contracted specimen will follow it naturally.  It  seems  to  me  that, in the mere
destruction and absorption of tissues, there is abundant explanation of the shrunken
dimensions of a kidney which has passed  through inflammatory changes.   The tubes
have burst, and a great portion of their contents has been removed by absorption; the
Malpighian bodies have dwindled to a few; what, then, remains to make bulk?  In
the uncontracted specimen a false appearance of size is maintained by the adventi-
tious cyst-growth, which, I have described as filling the interstices of the organ.  But
the cysts are so much over and  above the  real  kidney-structure; and if that succulent
surplus could be removed,  the result, as I  have  suggested, would be the falling
together of wasted textures into a comparatively small  compass.   The  cause of
shrinking in the  gland  is the  gradual absorption  of spoiled material.  This cause
operates equally in all chronic cases, and its effects are to  be traced in the uncon-
tracted, as in the contracted specimen.  The  main difference between these two lies
in the more or less of interstitial cyst-development; the most dwindled are those in
which  least of the new growth has arisen or has survived.
  "I see no reason for believing that the interstitial  effusion of lymph effects much
towards the final  contraction of the kidney.   There are not wanting, I know, some
pathologists who will assert  it to be the great agent in the change; and who conceive
they have seen the whole process of fibre-formation, according to the most approved
foreign cell-theories.  But I suspect that the  observers of new fibre will often have
confounded cause and effect.  Coincidently with atrophy of the kidney, there occurs
a contraction of the reticular matrix; but that  contraction is, probably, consequent on
a prior absorption  of the intervening tissue.  The meslies  of the matrix come nearer
together, and, in a given space,  there is an excess of  fibrous tissue, only because the
material is withdrawn, which originally expanded that matrix through three times the
space  it now occupies.
  "Up to the present point, I have studiously  avoided introducing the ambiguous and
controversial  name of 'Bright's Disease.'  And now it will probably be asked, what
relation to Bright's Disease is borne by the malady I have treated of?  Is it the same
thing  under another name?  This question can be answered in a word, only when it
shall have been settled what Bright's Disease really is.  The history of the  complaint
or complaints, included under that title, was, perhaps, originally systematized with too
much  haste.  Starting from dropsy with albuminuria,  and noticing that two chief
forms of morbid appearance corresponded to  that symptom (one, namely, where the 
462
THE  SOLIDS.
kidney was large  and mottled;  the  other, where it was contracted and knobbed, or
irregularly granular), pathologists have considered these two  forms  as representing
the extreme stages of one and the same disease.
  "I must venture to express a doubt as to the justice of this generalization.  After
investigating both classes extensively, I am convinced  that the mottled and the con-
tracted kidney do, in almost every instance, belong to different morbid actions; not to
different stages of the same.
  "The mottled kidneys, in an infinitely large proportion of cases, remain large and
mottled to  the end.
  "I have  now little  further to add; with respect to the symptoms of sub-acute
inflammation of the kidney, I will make one observation in addition to those already
embodied in my paper.   The descent of epithelium and its germs  with the urine;
the presence  of albumen there, and sometimes of blood;  the  little casts of the
tubules—sometimes  wrought of  fibrin,  sometimes of compressed  epithelium;—
these signs belong equally to the sub-acute inflammation  and  to the scrofulous
disease.  They are signals simply of renal irritation, whether from one cause or the
other,  and  I suspect they only attend the scrofulous  disease at that  stage of its
progress in which  sub-acute  inflammatory action  is superadded to the primary fatty
degeneration.  Dr. Johnson's  accurate  observation has enabled us, under most cir-
cumstances, to diagnose the  two classes from each other; for,  in the scrofulous
disease there will  be always seen,  as he describes, more or less oil entangled in the
fibrinous casts, or  gorging the cells which descend in the urine; a phenomenon which
does not belong to the pure sub-acute inflammation."

   The following pages  embrace  the more  important  portions of Dr.
Johnson's communication, which is entitled, "On the Inflammatory
Diseases  of  the Kidney:"

  "In a paper published in the last volume of the 'Society's Transactions,' I gave
some account of fatty degeneration of the kidney, and declared my intention to  make
the inflammatory diseases the subject of a separate communication.  On the present
occasion, I  purpose to bring before  the  Society the result of some observations on
this very interesting and important subject.
  " In  the  paper  before alluded to, when  referring to the  condition of the kidney,
which occurs as a  consequence of scarlatina, I stated that "it is, in fact, an inflamma-
tion of the  kidney, excited, like the  inflammation of the skin which constitutes the
eruption of scarlatina, by the passage through the part of the peculiar fever-poison;
and as the inflammation of  the skin terminates  in an excessive development  of
epidermis, and a  desquamation of the surface, so the  inflammation  of the kidney
excites an increased development of  the epithelium which lines the urinary tubules-
this material partly accumulates in and chokes up the tubes, while part of it becomes
washed out with  the urine, and may be detected in large quantities in that fluid by
the aid of the microscope.
  " To the  account then given, which I believe to be essentially correct, subsequent
observations enable me to make some important additions.
  "On a microscopical examination, the convoluted tubes are seen filled in different
degrees with nucleated cells, differing in no essential character from those which lme 
GLANDS.
463
the tubes of the healthy gland.   The chief difference between these cells, which are
the product of inflammation, and those which  exist in health, consists in the former
being generally of smaller size and more opaque and dense in their texture.  It is very
interesting and important to observe that, while the convoluted tubes are rendered
opaque by this accumulation of cells in their interior, the Malpighian bodies are trans-
parent and apparently quite healthy.  The straight tubes which form the pyramids also
contain an increased number of  cells; but there is reason to believe, that these cells
are not formed in these portions of the tubes, but that they are lodged there in their
passage  from  the convoluted through the straight  tubes; the  latter being merely
ducts leading  into the pelvis of the kidney.  Some of the tubes contain blood, which
has, doubtless, escaped from the gorged Malpighian vessels lying within the dilated
extremities  of the tubes.  There is no  deposit outside the  tubes.  The essential
changes  in the kidney are an increased fullness of the blood-vessels, and an abundant
development  of epithelial cells,  differing slightly in general appearance, size, and
consistence, from  the normal renal cells; this increased cell-development occurring
in those  portions  of  the urinary tubules, the  office  of which, as  Mr.  Bowman has
suggested, is to excrete the peculiar saline constituents of the urine, while the Mal-
pighian bodies, whose office is the separation of the  water,  are unaffected.
   " The  condition of the urine in these  cases, is  clearly indicative of the  changes
occurring in the kidney.  After  the urine has been allowed to stand for a short time,
a  sediment  forms, and, on placing a portion of this under the  microscope, there may
be seen blood corpuscles, with epithelial cells in great numbers, partly free and partly
entangled in  cylindrical fibrinous  casts of the  urinary tubes; and, very commonly,
numerous crystals of lithic acid are present.   As the disease  subsides, which, under
proper treatment, it  usually does in  a few days, the blood, fibrinous  casts,  and
epithelial cells, diminish in quantity, and finally disappear;  but traces of the casts
and cells are  still visible some  days after the urine has ceased  to coagulate on the
application  of heat or nitric acid.
   " The  casts and cells which appear in the urine, when  the disease is subsiding, are
such as  have remained some time in  the urinary tubes before they have become
washed out by the current of fluid poured into the tubes  from the Malpighian bodies;
many of the cells entangled in these casts have, consequently, become disintegrated
and broken up into amorphous granular masses; thus presenting appearances which I
shall presently show  are  characteristic of the  casts occurring in cases of chronic
nephritis.   Such is the morbid anatomy of the kidney, and such are the characters of
the urine occurring as a consequence of scarlatina.
   "To the form  of  renal  disease here  described  as occurring in connexion  with
scarlatina, I propose to give the name of  ' acute desquamative nephritis?
   "The  next  form of inflammatory disease, to which I would  direct attention, is one
of great interest and importance.  Two  drawings by Mr.  Westmacott represent the
disease  in two different  stages;  one  represents a  kidney in the earlier  stage; the
other shows a more advanced stage of the same disease.  The kidney is never much
enlarged; in the earlier stage, the size of the organ is natural, and the structure of
the cortical portion appears confused, as if from the admixture  of some abnormal
product; there is also some  increase of vascularity.  As  the disease advances, the
cortical  portion gradually wastes; the entire organ becomes contracted, firm, and
granular; the pyramidal bodies remaining comparatively unaffected even in  the most 
464
THE  SOLIDS.
advanced stages: simultaneously with the diminution in size of the kidney, there is a
decrease of vascularity.  These changes occur very gradually; the disease is essen-
tially chronic, having a duration in most cases of many months, and in some even  of
several years.  It is almost confined to persons who  are in the habit of partaking
freely of fermented liquors;  it is very commonly seen  in those who have suffered
from gout, and is not, uncommon in those who, having indulged freely in the use of
fermented liquors, have yet never had an  attack  of  gout.  It is  sometimes, but I
believe rarely, met with in those whose mode of life has been  strictly temperate and
abstemious.   The symptoms  usually  attending the  disease,  are  the  following:—
dropsy, which commonly is not excessive, often coming on only in the most advanced
stages, and sometimes being entirely absent throughout the entire progress  of the
disease.  The urine is commonly albuminous:  it seldom, however, contains  a very
large quantity of albumen, and sometimes there is no coagulation on the addition of
heat or nitric acid.  The urine is sometimes high-coloured and scanty; but in most
cases, it is rather abundant, pale, and of low specific gravity—from 1005 to 1010.   In
some instances, the quantity of urine is much greater than in health, and this increased
quantity  of urine is secreted by kidneys which are found after death to be contracted
to one-third  of their original bulk.  In urine of such low specific  gravity, there is, of
course, a deficiency of the solid constituents, while the blood, which is much changed
and impoverished, contains an excess of these materials.
  " On a microscopical examination of the kidney, the  nature of the above-mentioned
changes is very clearly revealed, and at the  same  time, the  attending symptoms are
satisfactorily explained.  My  account  of these phenomena will be  rendered more
intelligible, if I give the facts  and their explanation at the same time.
  "On placing thin sections of the kidney under  the microscope, some of the tubes
are seen  to  be in precisely the same condition as in  a case of  acute desquamative
nephritis: they are filled and  rendered  opaque by an accumulation within them of
nucleated cells, differing in no essential respect from  the normal epithelium  of the
kidney: this increase in the number, and this slight alteration in the character, of the
epithelial cells, are the result  of the elimination, by the kidney, of mal-assimilated
products, which are being continually developed in these gouty  and  intemperate
subjects, and which are not normal constituents of the renal secretion.
  " There must evidently be  a certain limit to the number of  cells  which can be
formed in any one of the urinary tubes; for, although  some of the  cells  escape with
the liquid part of the secretion, and so may be seen in the urine, as  in a case of acute
desquamative nephritis, yet, in many of the tubes, the cells become so closely packed,
that the further formation of cells is impossible, and the process of  coil-development,
and, consequently, of secretion within that tube, are arrested.   The  cells, thus formed
and filling  up  the tube, gradually decay, and become  more or less disintegrated.
While these changes are going on in the convoluted portions of  the  tubes, the Mal-
pighian  bodies remain quite  healthy, the  Malpighian  capsules for the most part
transparent,  and the vessels in their interior are perfect.   From these vessels  water
with some albumen and coagulable  matter, is continually being poured into the tubes;
and, as a consequence of this, the disintegrated epithelial cells are washed out by the
current of liquid flowing through the tubes so that, on examining the sedimentary
portion of the urine, we find in it cylindrical moulds of the  urinary tubes composed
of epithelium in different degrees  of disintegration, and rendered  coherent by the 
                                  glands/                            41.rj
                                                         •
fibrinous matter  which coagulates  among its  particles.   The  appearance  of these
casts are quite characteristic of this form of 'chronic desquamative nephritis.'
  "There is reason to believe, that when the process of cell-development and of
secretion have once been arrested, by the tube becoming filled  with its accumulated
contents, it  never recovers its  lining of normal epithelial cells; but, when the disin-
tegrated epithelium  has become  washed  away from  the interior  of the  tube, the
basement membrane may be seen, in some cases, entirely denuded  of epithelium; in
other cases, a few granular particles of the old decayed epithelium remain: and again,
in other instances, the interior of  a tube, which  has been deprived of its  proper
glandular epithelium, is seen lined by small delicate transparent cells, very similar to
those which may sometimes be seen covering the vessels of the  Malpighian tuft.
  " It now becomes interesting to ascertain what further change the tube undergoes,
after having lost its normal epithelium.  It is quite certain that, as a general rule, the
Malpighian bodies remain unaffected, both in structure and in their  office of secreting
the watery constituents of the urine, until the whole of the disintegrated epithelium
has been washed out of the tubes.  Of this there are two proofs; the first is the fact
of a very long  convoluted tube having its contents completely washed  out, and its
basement membrane left quite naked: this could happen only as a  consequence of a
current of liquid passing through  the  tube, and there is no known source of  such a
current but  the Malpighian vessels: the  second proof is still more convincing and
satisfactory, and  it is this—that a tube may often  be seen entirely denuded of its
epithelial lining, and continuous with a Malpighian body, in the  interior of which the
vessels are quite  perfect.
  " Now, a tube of this kind, deprived of its lining of normal epithelium, has manifestly
lost its power of separating from the blood the solid constituents of the urine, while
the Malpighian  vessels remaining unaffected, the power of secreting water remains.
Further, it appears probable not  only that the Malpighian body continues to secrete
water, but that the whole length of a convoluted tube thus deprived of its  proper
epithelium, and either  remaining naked or lined by delicate nucleated cells, such as
those which  cover the Malpighian vessels—that the entire length of such a tube
becomes a secretor of water, which it abstracts from the  portal plexus of vessels on
its exterior.   This is rendered probable by the appearance of the tube itself; and the
probability is still further increased by the fact of the tubes becoming, in some cases,
dilated into cysts, which usually contain a simple serous fluid, without any of the solid
constituents of the urine.
  " It has long  been supposed that the simple cysts, which are so commonly seen in
connexion with some  forms of renal disease, are, in  fact, dilatations of the urinary
tubes.   I am not aware that any satisfactory evidence has been  adduced  in confirma-
tion of tins  opinion, but there are some facts and arguments  which appear  to me
abundantly sufficient to prove  the accuracy of the notion.
  " ] st. The tubes thus denuded of their epithelium are' often seen much dilated.  I
have repeatedly seen them three or four times exceeding their normal diameter.  In
some cases the dilatation is very sudden, so  that the tube assumes a globular form,
and appears to  bulge in the intervals of the  fibro-cellular tissue, in which the tubes
are packed:  in some cases, too, the basement membrane appears thickened in propor-
tion to the dilatation of its cavity.   Now, this process of dilatation  having once com-
menced and the lower end  of the  tube becoming closed by a deposit in its interior, or
                                    30 
466                          THE   SOLIDS.

by pressure from without, there is no reason to suppose  that the process may not
continue until a cyst as large as a pea or a walnut is formed.
  "2dly.  But there are other facts which afford a  very interesting and remarkable
confirmation  of this notion.   In  a case of simple  acute  or chronic nephritis, the
quantity of oil in the secreting cells of the kidney is very  small; sometimes, indeed,
none can be detected.  But it frequently happens that, after a tube has been stripped
of its secreting cells in the manner before mentioned, an  accumulation of fatty mat-
ter occurs  in its interior, the  denuded basement membrane becomes scattered over
with separate oil globules, and these increase in size until they form masses of fatty
matter, having much the appearance of adipose tissue; and such a mass is frequently
washed out from the tube, and may be detected in the urine.  This occasional filling
of the tube with  fatty matter is  very interesting in connexion with the fact, that  in
some cases the cysts, which are  supposed to be dilated tubes, are also found filled
with the same material.  In two cases, I have found a cyst as large as a hazel-nut,
quite full  of oil, presenting all the characters of that seen in the tubes which have
lost their epithelium in consequence of chronic inflammation.
   "The evidence, then, of the simple serous cysts being dilated tubes, is the follow-
ing:—1st.  That  tubes are often  seen much  dilated  and thickened.   2d.  As the
inner surface of the tubes has the appearance of being endowed with the power  of
secreting water, so  the cysts usually contain a simple serous fluid.   3d.  As an accu-
mulation of  oil occasionally occurs in the tubes, so the cysts are in some instances
filled with the same material.  4th.  There is  no  reason  to suppose that these cysts
have any other origin.   It  appears probable that the Malpighian bodies could not
become dilated into cysts, because an accumulation of  liquid within  the  Malpighian
capsule would necessarily compress and obliterate the vessels of the Malpighian tuft
and so would cut off the further supply  of fluid.
   " Another  change consequent  upon the  destruction  of the  cells  which  line the
urinary tubes is, a diminished supply of blood, and a gradual wasting of the tube.
I have already shown that there  must be a close  connexion between an increased
development of epithelial cells, and an increased afflux  of blood to the part.  This is
well seen in a case of acute desquamative nephritis, and  vice versa, a more or less com-
plete destruction of the epithelial cells will be attended by a corresponding diminished
afflux  of blood, and a consequent atrophy of the  part affected.  In every kidney
which has been the subject of chronic inflammation, there may be seen tubes  con-
tracted in different  degrees, as a  consequence of the destruction of their epithelial
lining;  in some instances, the basement membrane becomes folded, and presents  an
appearance not very unlike white fibrous tissue.  As a consequence of  this wasting
of successive sets of tubes, there is a gradual diminution in the bulk of the cortical
portion of kidney,  until, at length, the  entire organ becomes small, contracted, and
granular.  When a thin section of a kidney, thus atrophied, is  placed under the
microscope, there may be seen an abundance  of fibrous tissue; and this has often
been described as new fibrous tissue developed during the progress of the disease:
whereas it is, in reality, nothing  more than the  atrophied  remains  of the basement
membrane of the tubes, with the healthy fibrous tissue arranged in the form of a
network in which  the  tubes  are packed, and which now appears more abundant in
consequence of the wasting of the tubes.
   "It has already  been stated that the Malpighian bodies are unaffected  in  the 
GLANDS.
467
progress of this disease; and this is true, in so far as they remain, for the most part,
free from any deposit or accumulation in their interior; but they must necessarily be
affected by the changes occurring in other parts of the organ.  Thus, the destruction
of many of the Malpighian  bodies is a necessary consequence of the simultaneous
wasting  of the vessels  and tubes which occurs in the advanced stages of chronic
nephritis: and, during the progress of the disease, the vessels of the Malpighian tuft
will be in  a state of more or less active congestion, in proportion to the rapidity of
secretion and of cell development in  the tubes ; and one consequence 6f this con-
gestion of the Malpighian bodies will be the escape of serum into the tubes, and the
mixture of albuminous matter with the urine.  The quantity of albumen in the urine
will be great in proportion as the disease approaches in activity to that form which I
have called ' acute desquamative nephritis.'   When the disease is chronic and inactive.
there may be no albumen in the urine, or, it may be present in quantities so small as
not to be detected by the ordinary chemical tests.  In such cases, as, indeed, for the
accurate discrimination of all forms of renal disease, the microscope will be found an
invaluable  aid.  It must be remembered that the  essential change in this disease is a
destruction of the epithelial cells in the manner already described; the best evidence
of this change being in progress is, the presence in the urine of moulds of the urinary
tubes, composed of  more or less disintegrated epithelium; and such evidence I have
repeatedly obtained, when no albumen could be detected by  the ordinary heat and
nitric acid tests.
   " A sufficient explanation has  already been given of the small quantity of the saline
constituents excreted by the kidneys in cases of chronic nephritis.  It is manifest
that, if the epithelial cells are the agents by which the solid constituents of the urine are
separated  from the blood, a deficient excretion of these materials will be a necessary
consequence of the greater or less destruction of the epithelial  cells.
   " Before concluding this communication on the inflammatory diseases of the kidney,
it appears  desirable to allude very briefly to the subject of my  last paper, viz: 'Fatty
Degeneration of the Kidney;' my object being to  show how essentially distinct are
the two  forms of disease; and, at the same time, to  explain the  manner in which they
are sometimes combined.
   "For  some months past, I have been aware that fatty degeneration of the kidney,
occurs in two distinct forms.
   "In the simple fatty degeneration  of the kidney, all the tubes become almost
uniformly  distended with oil.  In a slight degree and in the earlier stages, it is often
found, after death, in cases where there is no reason to  suspect that it has been pro-
ductive of any mischief during life: it is not until the fifty accumulation has attained
a certain amount, that the functions of the  kidney are interfered with.   It is this form
of fatty degeneration of the kidney which occurs in animals, as a  consequence of
confinement in a dark room.  In the human subject, although in the earlier stages, it
is a  very common occurrence, yet in the  more advanced stages it occurs less fre-
quently than the second form  of fatly degeneration.  This form  of the  disease is
represented in the  5th figure of Dr. Bright's 3d plate, as well as in the 1st, 2d, 5th,
and 6th figures of Rayer's 8th plate.   The cortical portion of the kidney, to use the
words of Dr. Bright, is soft and pale, and interspersed with numerous small yellow
opaque  specks.  The kidney is generally  enlarged;  sometimes it is even double the
natural size.   In some cases, the cortical portion is somewhat atrophied and granular; 
468
THE  SOLIDS.
but neither in this, nor in the first form of fatty degeneration of the kidney, does that
extreme wasting  with granulation  occur, which  is  so  frequent a consequence  of
chronic nephritis.
  '•On a microscopical examination, the convoluted tubes are found filled in different
degrees with oil; some  tubes  being  quite free,  while others are ruptured  by the
great accumulation in their interior.  The opaque yellow spots scattered throughout
the kidney, are neither more nor less  than convoluted tubes distended, and many of
them ruptured by their  accumulated  fatty contents; just as the red spots are found
to be convoluted  tubes  filled with blood.  The  cells which contain the oil  are for
the most part smaller, more transparent, and  less irregular in their outline than the
ordinary healthy epithelium; they are increased in number, and many of them are so
distended with oil as to appear quite black.   In parts of the same  kidney, there
may commonly be seen  some of the appearances already described as indicative of
desquamative nephritis.   This form of disease is very commonly combined with fatty
degeneration of the liver; but less frequently than is the first form of fatty degenera-
tion of the kidney.
  " The peculiarities of  the second form of fatty degeneration of the  kidney result
from a nephritic condition of the organ, dependent on the presence of some irritating
material in the blood being associated  with a tendency to fatty degeneration; this
tendency resulting from the presence in the blood of mal-assimilated fatty  matter.
The nephritic condition  is manifest by an increase in the number of epithelial cells;
the tendency to fatty degeneration, by a filling of many of these with oil.  Although
the two conditions are combined in this  and in similar cases, it must be remembered
that they are essentially distinct in their nature and origin.  Each cell which  escapes
from the kidney carries  with it a portion of the morbid material.  The oil is in the
form of visible globules; while the cells which contain no oil doubtless contain some
other material  which is invisible, or less readily seen  than the oil globules.
  "I have now distinguished and described four conditions  of the kidney:
  " 1 st.   Acute desquamative nephritis;
  " 2d.  Chronic desquamative nephritis;
  " 3d.  Simple fatty degeneration; and"
  "4th.  A combination  of fatty degeneration with desquamative nephritis.
  " The diagnosis of each of these conditions of the kidney, during the  life of the
patient, is a matter of the greatest importance with reference to prognosis and treat
ment; and the diagnosis may be made with ease and certainty by a  microscopical
examination of the urine.

   The most recent  researches  in this country into  the patnoWical
anatomy of the kidneys are those of Dr Gairdner,* who has evidently
devoted to the elucidation of this subject not  a little  time and  atten-
tion;  and  the  results of these  investigations will now be  given in  as
concise a form as possible.
  Dr. Gairdner treats of his subject under the three following heads:
  1. Exudation; 2.  Lesions affecting chiefly the vascular system; and 3. Lesions of
the tubes and epithelium—an arrangement which  will here be followed.
  *  "Contributions to  the  Pathology of  the Kidney," by  William T. Gairdner,
M.  D.—Monthly Journal of Medical Science, 1848. 
GLANDS.
469
                                   Exudation.
   Exudations into the  substance of the kidney  give rise to a great variety of
external appearances, which have been well figured and described in  the works of
Bright and Rayer.
   Exudations from the blood-vessels may have their seat in any, or all the tissues of
the kidney; their usual situation, however, is in the interior of the tubes, but it also
occurs frequently within and around the Malpighian bodies, and in the inter-tubular
tissue, the tubes being quite clear;  it is also seen infiltrated through all the tissues
in the form  of a homogeneous mass, which  contained within it  the  whole of the
anatomical elements of the kidney.
   The appearance of the kidney, as altered by the presence of exudation in the tubes,
is subject to  variations depending on the amount of the deposition, and its partial or
general character: one almost invariable effect of  the repletion of  the tubes, is  a
corresponding diminution in the fullness  of the vessels  of the cortical substance,
particularly of the  Malpighian vessels, and the capillaries  surrounding the tubes.
This effect is evidently the result of pressure.
   It is thus evident that Dr. Gairdner does not ascribe the albuminous urine of Bright's
Disease to secondary congestion, or rupture of the Malpighian bodies, caused by the
distension of the tubes from accumulated  fat; and in this particular his views differ
from those already cited of Dr. George Johnson.
   The volume and weight of kidneys containing exudation in the tubes are frequently
much increased.
   The exudation may be  diffused throughout the organ, or it may be confined to
certain portions of  it. " It then tends," writes Dr.  Gairdner, " to accumulate in cer-
tain sets of the  convolutions in which  the urinary current is  least active.   These
becoming partially blocked up, and  ceasing entirely  to secrete, are thrown aside from
the outward current of  secretion,  and become a  centre  of attraction for  further
deposit, just as the eddies and still  waters at the sides of a rapid stream receive from
it the foam and floating bodies brought down from above.  In this way, more and
more of the adjacent loops of tubuli are filled with the abnormal deposit, and become
added to the former nucleus, until the masses of exudation, thus imprisoned within
tubules through which no  secretion passes, form irregularly rounded  bodies in the
cortical substance, visible to the naked eye, more or less prominent on the surface of
the organ, and usually of an opaque yellowish colour.  These are the granulations
first described by Dr. Bright."
   Intra-tubular exudations, including tubercular and cancerous deposits, may be con-
sidered under three heads: a, crystalline  or saline matters deposited from the urine;
b, oleo-albuminous,  or granular exudations from  the blood plasma;  c, exudations
forming pus.
   a. The most common saline deposit met with in  the tubes of the kidney is  the
amorphous urata of ammonia;  inasmuch as this salt is a constituent of healthy urine,
its presence in moderate quantities is merely a normal post-mortem  appearance, the
deposition of the salt resulting from the cooling of  the urine after death.   In some
instances, however, it  is present in such large quantities, and in these it occasions such
an alteration in the  appearance of the kidney, that it might, unless discriminated by
means of the microscope, be attributed to disease. 
470
THE  SOLIDS.
  Under the microscope, the urate of ammonia presents the appearance, when within
the tubes, of a fine molecular shading which  entirely  obscures the nuclei; the dis-
tinguishing  character of this deposit is its ready solubility in the dilute acids, as the
acetic or nitric.
  In one case  Dr. Gairdner detected the  presence of crystals in the tubes, which, from
their appearance and colour, he entertained little doubt were of  uric acid, although,
from their minute quantity, they could not be  submitted to chemical examination.
  In this case  the urine was of low specific gravity, and albuminous, although there
was no apparent exudation within the substance of the gland.
  b. Dr. Gairdner includes under the  term " oleo-albuminous exudations from the
blood plasma," those exudations which are fatty in their nature, as well  as the inflam-
mation globules, granular corpuscles, or exudation granules, and corpuscles of differ-
ent writers.
  The facts connected with the presence of fatty exudations in the kidney, have been
almost exhausted by the excellent  reasearches of Dr.  Johnson; one additional fact
of interest has been  added by Dr. Gairdner.  This  observer finds that the  fatty
granules or  globules are not confined to the  epithelial cells, but also that they may
be freely disseminated throughout the tubes: the tubes containing the fatty granules
sometimes appear  distended, at other times smaller than natural, as if they had con-
tracted around the fat.
  It is probable that the presence of the fatty  globules in the tubes results from the
rupture and disorganization of the cells which first contained them, and that, there-
fore, their location in the tubes themselves indicates a more advanced  condition of
this form of renal disorganization.
  c. The occurrence in the cortical  substance  of deposits of pus is not very uncom-
mon : their most usual form is that of small abscesses, rarely exceeding the size of a
pea, and frequently much smaller; sometimes confluent, and irregularly disseminated
throughout the cortical substance.
  The granular (oleo-albuminous) form of exudation is frequently found occupying
the tubes of the kidney, and occasionally also  within the capsules of the  Malpighian
bodies: when  in large quantity in the latter  situation, the tuft of vessels becomes
compressed, shrunk, and, in most cases,  invisible.
  Under the heading " Partial  distribution of the oleo-albuminous  exudation," Dr.
Gairdner describes, in the following terms, a peculiar  pathological condition of the
kidney:—" I have already described the formation of granulations as  dependent on
the accumulation of deposit in particular groups of tubules in the cortical substance.
In such cases,  however, the affection is  probably, at first, general; they are very dif-
ferent  from the form now to be described, in which the deposit is quite limited in
extent, and isolated.
  " There are  occasionally met with, on removing the  capsule from the surface of a
kidney, irregular  patches, of a paler  colour than the rest of the organ, sometimes a
little elevated, sometimes depressed below the general surface.  Their boundary is
quite abrupt, and  they are frequently surrounded by  a well-marked  rose-coloured
areola, extending more or less into the surrounding substance.   On making a section
of these patches, they are found to  penetrate into  the cortical  substance, and some-
times even a  certain way into the  pyramids.  The vascular  areola,  when  present,
extends round them in every direction, and is found, on examination, to consist of 
GLANDS.                              471
  highly-injected Malpighian bodies and capillaries, with or without extravasation; the
  colour  of the  patches varies from yellowish-gray to gamboge-yellow: their con-
  sistence is generally firm.  On microscopic examination, they present a large amount
  of exudation, varying from the molecular to the large granular form.  In some cases
  the  tubes may be seen filled with exudation; in others they  appear to be in great
  part obliterated.  In one case I found the Malpighian bodies quite free of exudation;
  they  preserved their usual arrangement, and were readily discoverable by a simple
  lens on the surface of the  section.   The parts  of the kidney not involved in the
  deposit, generally present no abnormal appearance."

                   Lesions affecting chiefly the Vascular System.
   Variations in the vascular condition of  the kidney may, and  frequently do exist,
  totally unconnected with organic  change: thus, this organ, like all other vascular
  structures, may be either in a hyperemic  or anaemic state; and these conditions may
  affect either the entire vascular system, or they may be local  only,  or they may
  involve respectively the venous or arterial  vessels.  The veins of the kidney are dis-
  posed chiefly in  two  situations, viz: on its  surface, and in the substance of the
  pyramids, the cortical  substance containing  but  few veins.  On  the  surface  the
  larger vessels follow a somewhat stelliform arrangment, while the  capillaries'them-
 selves form a mesh-work, the meshes  describing small pentagonal or hexagonal
 spaces, in each  of which a single convolution of a tube is  situated.  The  state  of
 these vessels is subject to much variation;  they may be in an anaemic condition, and
 scarcely visible,  or they may be gorged with blood; in some instances this engorgement
 is general, and in others it is confined to the  stelliform vessels just referred to.  These
 conditions, as already observed, may be totally unconnected with disease; when,
 however, there  is great irregularity of injection, amounting to marbling of the sur-
 face, and  great  increase in  the  size  of  the stellar  vessels,  these are  generally
 pathological, and result either from  partial obliteration of the venous net-work, or  of
 the  extrusion of the blood  from it, through over-distention of the loops of tubuli
 which form the  intervening pale spaces.
   " The  engorgement of the capillaries and Malpighian tufts gives rise to two condi-
 tions: first, a generally diffused  heightened colour of the cortical  substance; and
 second, increase and greater distinctness of  the vascular striae, running from the base
 of the pyramids  to the external surface.   This latter species of injection  often exists
 to a great extent, without any corresponding injection of  the rest of the  kidney, and
 in some  instances the red points  composing  the striae are so  much increased in size
 as to form  considerable petechiae (one line in diameter, or upwards), in which case
 the petechiae usually extend to the surface,  occupying the intervening spaces of the
 venous polygons above mentioned.  This  appearance was supposed by Rayer to
 occur from  simple hypertrophy and vascular injection of the Malpighian bodies; but
 Bowman,* who has shown that the Malpighian bodies do not exist on the surface of
the kidney, has  also given a better  explanation of such petechias, which  he  holds to
arise  from  rupture  of the  Malpighian tuft,  with extravasation  of blood  into the
surrounding tubes.  He argues that the petechiae are of irregular form, and  of much
larger size than the Malpighian bodies have ever been observed to acquire.  He gives,
                       *  Philosophical Transactions,  1842. 
472
THE  SOLIDS.
    also, a figure  representing the occurrence of a similar appearance, from artificial
    injection, at the surface  of the kidney.  In this figure the loops or knuckles of the
    tubuli are seen filled with injection, presenting  themselves at the surface, and sur-
    rounded by the venous net-work."

      The correctness of this explanation cannot be doubted; and it is therefore evident
    that the occurrence of these petechiae must be considered as invariably morbid.
      The anaemic condition of the kidney, when the result  of disease, is generally
    accompanied by increase  in the  size of the tubes from contained secretion; and it is
    the pressure of these on  the surrounding vessels that occasions their empty condi-
    tion, and, in some instances, even obliteration.  The vessels of the Malpighian tufts
*   likewise become involved, and the Malpighian corpuscles themselves, thereby altered
    inform, from being globular they become angular and compressed.
      Under the  heading, "Congestion  followed  by  permanent  obliteration of the
    Capillaries," Dr. Gairdner has described a lesion of the kidney, which he has desig-
    nated by the term " waxy degeneration!'' in contra-distinction to the "fatly degeneration^

      " The appearances most characteristic to the naked eye of this form of lesion, are
    those so admirably figured and described by Rayer as  the second  form  of his
    'nephrite albumineuse.'   The kidneys are generally increased in size, sometimes very
    remarkably so.  Their consistence  varies:  they are sometimes more flaccid than  in
    the  natural condition, but always  preserve considerable tenacity.  The  surface is
    either quite smooth, or  more or less  depressed and furrowed.   The venous vascu-
    larity assumes, to a considerable extent, the stellate form; the polygons are mostly
    absent;  and the extreme irregularity and abruptness of distribution of the superficial
    veins gives to the surface  a variegated  or 'marbled' appearance, which is quite
    characteristic of this  stage  of  the affection.  (See Rayer, Plate,  VI. figs. 2, 3. 5;
    Bright, Plate II. fig. 1.)   Occasionally, also, amid this unequal injection, there are to
    be found scattered petechiae, indicating recent extravasations of blood into the tubes.
    On  section, the cortical  substance  has considerable volume,  and presents a smooth,
    glistening, almost semi-transparent appearance, which cannot be better distinguished
    than by the term  waxy.  It may  partake in a slighter degree  of the variegated
    character of the  surface; more commonly it is of  uniform appearance, and of a
    yellowish  or fawn-colour, sometimes verging into a pale flesh  tint.  The vascular
    striae  of the cortical substance are generally to be traced by a more or less distinct
    injection, and a few injected Malpighian bodies, or petechiae of extravasation, are
    sometimes  dispersed through the  section.   (See Rayer, Plate X. fig. 3.)  In other
    cases, a little further advanced, both the striae and the Malpighian bodies are nearly
    destitute of blood.  (Rayer, Plate X. fig. 1; Bright, Plate II.  fig.  1.)  The pyramids
    frequently retain  their normal vascularity; sometimes, however, they are of a pale
    colour, and  their  bases  are indistinctly marked—a  condition  which indicates  the
    progress towards a further disorganization.
      " When  a kidney in this  condition is carefully and minutely injected, the greater
    proportion of the cortical substance remains impervious; the injection however, can
    frequently be made to penetrate as far as the cortical striae, and even to some of the
    Malpighian bodies.  (See Rayer, Plate X. fig. 2; Bright, Plate II. fig. 3.) 
GLANDS.
473
  "From these circumstances it is obvious, that the lesion above  described consists
in an obliteration or obstruction of the capillary system of vessels throughout the
organ, and a partial obliteration of the  veins on  its surface.  There is also every
probability that this condition is secondary to one  in which there is a high degree of
congestion of the  organ.  The extravasations, the  occasionally injected Malpighian
bodies,  and the highly injected though partially  distributed stellar veins, leave  no
doubt that the  state of  congestion  described as the first form of albuminous
nephritis by Rayer, is really the antecedent of the present or second form.
  "To  any one who is familiar with the marbled and waxy kidney here described,
there can be no difficulty in recognising  a further  stage of the same lesion, in which
the organ is  perfectly pale, both on the surface and on section, with the exception,
perhaps, of a  very few  stellated superficial veins.  The kidney in this  stage (the
transition to which seems to  be represented in Rayer, Plate VI. fig. 4) is still heavy
and voluminous;  it acquires additional firmness and elasticity, and  assumes much of
the general appearance of a true non-vascular texture.  It varies from a light yellow
to a fawn-colour, which extends to the pyramids, the bases of which become still
more confused and  intermingled with the  cortical  substance  than in the  marbled
kidney.  The capsule is frequently more firmly  adherent to the external  surface
than in health.
  "From the pale and yellow appearance of the kidney in this stage, it is very apt to
be mistaken, even by a practised eye, for an extreme degree of the fatty degenera-
tion.  A well-marked example, indeed, will hardly give rise to this error, if attention
be directed to the degree of firmness of the organ, the peculiar lustrous character of
the cut  surface, and the entire absence of. the opaque granulations of Bright, or of
that dull tint which distinguishes the excessive degrees of the fatty disease.  The
appreciation of these characters is, however, more  difficult where,  as  sometimes
happens, exudation is also  present; and  the distinction which has  escaped the acute
observation of M. Rayer, has undoubtedly been overlooked by many other observers.
  "The  microscopic characters of this  lesion are chiefly  negative.  There is  not
unfrequently an entire absence of exudation;  indeed, in the most marked cases of
the lesion, I have  seldom  found even the slightest trace of any  abnormal deposit.
Occasionally, however, there is a very minute quantity of fatty exudation In the tubes,
generally in very  small granules, and  scattered throughout the organ.  The tubes
are either natural, or in the advanced stages pass into some of the states hereafter to
be described.   The capillary  vessels surrounding the tubes are not  visible, and in
their place there is fibrous  tissue, which in this form of lesion always appears some-
what  exaggerated.   The Malpighian bodies are also frequently seen in  process of
obliteration, and surrounded by dense capsules of  fibrous tissue.  The epithelium is
frequently altered in character, but its changes follow no fixed rule.
  "The absence or scantiness of exudation, taken in connexion with the extent of
degeneration appreciable  by  the naked eye, are  amply  sufficient  characters  to
distinguish this lesion from the extreme stages of the fatty disease." 
474
THE  SOLIDS.
                     Lesions of lite  Tubes and Epithelium.

   Some of these lesions have been already described under the head of exudation;
but there are  others which are  not  less important than those formerly alluded to,
and which are very frequently found in connexion with them.

   Imperfect Development of the Epithelium  Cells and Nuclei—The epithelium cells
and nuclei vary in size  and characters  within certain limits even in healthy kidneys;
the nuclei less so than the cells  themselves; but in all kidneys, whether healthy or
diseased, the nuclei which  are most closely adherent to the basement membrane are
less perfectly circular, and of considerably smaller  size, than those lining the tubes
and surrounded by complete cell-walls.
   Those acquainted with the normal anatomy of the kidney will be able to determine
the limits of variations in the epithelium and nuclei compatible with a state of health.
   In very many pathological conditions  of the organ, the nuclei  occur in various
places  almost wholly devoid  of  cell-walls.   They may be more abundant or more
scanty  than  usual; and  often appear  in great profusion, huddled together in con-
fused masses, and mixed with shreds of membrane and amorphous molecular matter,
not soluble in acetic acid.   This  appearance  of debris, which  no doubt results from
disintegration of the cell-walls, most  frequently occurs  in  kidneys which are abnor-
mally soft and large, and from the cut surface of which an unusually large quantity
of turbid whitish juice may be scraped.  Such softened and altered kidneys occur
frequently in fever and other diseases.
   A more unequivocal pathological change (often occurring along with the above) is
the small size and altered form of the  nuclei throughout the organs, these not being
more than  half the usual  size, and always destitute of  cell-walls.  Sometimes they
float scattered  and solitary in the field of  the  microscope;  at other times, they
appear aggregated together either  by two's or three's, or-in much greater numbers,
the connecting medium being a transparent and  filmy substance, the  nascent  or
undeveloped cell-membrane which has  separated from the basement membrane, along
with the half-developed or young nuclei  above described.  These aggregations of
young nuclei are sometimes mingled with the amorphous debris of effete epithelium, or
with granules and molecules of oleo-albuminous exudation, or of lithate of ammonia,
which communicate to them a dark and confused appearance:  not unfrequently, also,
these  masses,  when  freed  from  the tubes,  retain more or less of their form,  and
present so exactly the appearance of  the  casts of the  tubuli  seen by Franz  Simon,
and many other observers, in the urine, as to leave no doubt of their identity with
these bodies.

   Desquamation  of the Epithelium.—The  changes above described  are generally
accompanied by an extremely rapid generation of nuclei, which are separated from
the basement membrane in an imperfect state, and carried away along with the urine,
in which they may be readily detected.
   In some cases of desquamation of  the epithelium, it  is scarcely possible to recog-
nise any  departure from the usual condition of the kidney, either with  or without the 
GLANDS.
475
assistance of the microscope.  The degree of vascularity is very various in different
specimens, and the epithelium thrown off is so  quickly resupplied, that there is no
very observable  change in  the  microscopic condition of the tubules.  In one very
intense case, in which ten pounds of very watery urine, loaded with an epithelial
sediment, were,passed daily for  some weeks before death, the  kidneys were small,
flaccid, and bloodless; many of  the tubes were quite full  of nuclei closely heaped
together; some of the nuclei  were under-sized; the cells, when entire, were  much
compressed and  angular.  In  an another instance, where  urine was passed in large
quantity and full  of epithelial debris, during the last two months of life, the kidneys
were found in an opposite condition, viz: large and congested, and  with a firmness
and smoothness of section like  the first  stage of the waxy degeneration formerly
described.  In this case, the condition of the tubuli was in most parts quite natural;
in some, however, there was extravasated blood, and  in  others the epithelium had
accumulated in abnormal quantity.   In both these cases there was imperfect develop-
ment of the epithelium, but cases have occurred to me in which this character was
by no means well marked: the crowding of the tubes with nuclei, although frequently
found  in  the  earlier stages of  desquamation, is not invariably present; and the
tubes were even seen to be  gorged with epithelium in a case where none had  been
separated from the urine for weeks before death.
   So long, therefore, as the epithelium is freely regenerated, the kidneys may present
a tolerably healthy appearance, even on minute examination: after prolonged disease,
however, further changes take  place; the epithelium becomes more sparingly gener-
ated, and is thrown off in the coherent masses above described, leaving the basement
membrane in  portions bare, or with a few scattered oval  nuclei, much smaller than
those  cast off, adhering  to  its inner surface.  In  the microscopic  examination of
organs in this condition, there  are frequently seen films of such  exceeding delicacy
and transparency  as to be only visible by very careful management of the light: they
preserve the shape of the tubules, and contain no nuclei or  structures of any kind.
Similar films are  occasionally  seen in the sediment of urine.   They are probably
thrown off from the  denuded basement membrane.

   " Obliteration of the Tubes.—The basement membrane, which, with the few closely
adherent oval  nuclei  above described, is  now the sole remaining structure of the
tubes, soon  undergoes a change.   It loses the  cylindrical form proper to it in the
fresh and natural  kidney, and becomes flattened by the pressure of the surrounding
parts.    Its cavity  is thus obliterated, and what was a tube assumes the appearance
of a transparent  riband, dotted  here and there with small oval nuclei, which, when
seen at the edges, appear to be enclosed between two layers of membrane.  These
riband-shaped portions of membrane appear to present considerable tenacity and elas-
ticity ;  by their greater density, and by the constant presence of the small oval nuclei
so often mentioned between their layers, they are in most cases readily distinguished
from the delicate  films which have been referred to above.  They are very various in
diameter, but are  always inferior in this respect to the normal tubes;  and they appear
to break up spontaneously into smaller portions, each of which contains from one to
six or more nuclei:  these portions are of various sizes; they are usually broadest in
the middle, and taper to a point at both ends.  The smallest of them contain only a 
476
THE  SOLIDS.
sin«rle nucleus, and present an appearance in every respect like that of young fibres
of areolar texture, or those fusiform cells, which have been  called fibro-plastic.  I
think it probable that the whole of the diseased basement membrane ultimately splits
up into fibres of this kind.  While these changes are proceeding, the capillary vessels,
which have ceased to be subservient to secretion, are usually obliterated: the conse-
quence of  this double  obliteration of vessels and tubes is a considerable degree of
atrophy in the diseased parts;  and as  the atrophy takes place  at first chiefly in the
cortical  substance,  great irregularities of the surface  generally supervene: thence
arises the appearance so well described and figured by Dr. Bright (Plate III. fig. 2),
in which, from the atrophy of the cortical substance, the bases of the pyramids 'are
drawn towards the surface of the kidney.'
  " When  oleo-albuminous  exudation supervenes on the above derangement of the
tubes, or when desquamation supervenes on the former  (circumstances which I con-
ceive to be of very common occurrence), the exudation most commonly takes the
form of the granulations of Bright, which are deposited chiefly in the diseased tubes;
and  the  atrophy proceeding around  these, they  become  salient,  and  the  surface
generally irregular, giving rise to the tuberculated state of the surface so common in
all the  later stages of the granulated kidney.  (Bright,  Plate III. fig. 1; Rayer,
Plate VII. fig. 6.  Plate IX. fig. 8.)   As the atrophy, however, proceeds, the granu-
lations are gradually absorbed; and when the kidney has become extremely con-
tracted and irregular, they often in part disappear.
  "The atrophied portions of the kidney are usually ex-sanguine, and of a tawney or
drab colour: they have considerable hardness and toughness.  Examined microscopic-
ally, they appear to consist of fibres and fusiform cells in great abundance, and more or
less granular exudation, according to circumstances.  According to  Henle, Eichholtz,
Gluge, and others, these fibres are in great part new formations; Johnson and Simon
consider them as nothing more than the compressed parenchyma of the gland, from
which all the other normal elements have disappeared.  I look upon them as formed
in great part by the breaking up of the basement membrane of the tubes (as above
described), as well as from  the  parenchyma and  obliterated  capillaries.  It is not
improbable, however, that in addition to these elements,  some new fibrous tissue
is formed.
  " The extreme stage of the atrophied kidney is  nearly the same, whether exuda-
tion  have existed or not.

  "Microscopic Cyst-formation.—It occasionally  happens, on examining the  section
of a kidney with the microscope, that we see, scattered through some  parts  of the
section,  a few  small clear vesicles, of nearly circular or oval  form : they are either of
a very pale straw-colour, or nearly colourless, and are perfectly clear and translucent,
with a very distinct shadowed margin, which causes them to stand out in bold relief
from the other textures composing the section.   Their diameter is usually from one-
fortieth  to  one-fifteenth of a millimetre, but in this respect they vary considerably;
sometimes they appear to lie in the tubular areolae, and at other times to be uncon-
nected with these.   Very rarely they have appeared to contain a few granules ; most
commonly, even when there  is granular  exudation around  them on every side, they
contain  nothing but clear fluid.   Their refractive power is not so great as that of 
GLANDS.
477
oil, while it is much greater than that of the spherical cells of the tubes: hence their
distinct and characteristic shadowed outline.
  " These bodies (which, however, have never appeared to me to present distinct
nuclei) are probably the same with the 'nucleated cells or vesicles' described by Mr.
Simon as resulting from the extravasation of the epithelial cells into the inter-tubular
tissue, and as progressively enlarging, so as to form the cysts visible to the naked
eye, which are so common in diseased kidneys.   To  these structures he  attaches
great  importance in the pathology of the kidney, conceiving them to be the invariable
result of the  desquamative disease when of long standing;  the kidney being, in Mr.
Simon's opinion, changed  more or Jess into an  aggregation  of  microscopic cysts,
which either  undergo  absorption, and lead to atrophy of the  organ, or increase in
size, and monopolize its texture.   Thus, according to Mr. Simon, the serous cysts so
common in  the  kidney result from an enormous development and hypertrophy of
extravasated  epithelium cells, which assume the character of the vesicles he describes,
and acquire the power  of increase and endogenous development.
  " Whether the bodies described by me above, are the same with the vesicles of
Mr. Simon, I have some difficulty in  determining:  but they are  the  only objects  I
have  seen which correspond at all closely with his description; unless, indeed, it
were  possible to suppose, as Dr. Johnson appears to hint, that he may have mistaken
the normal disposition  of the tubuli for a cystic structure.
   " However this may  be, I am satisfied that the vesicles above described are excep-
tional productions, and by no means invariably connected, as Mr. Simon describes
his vesicles to be, with the progress of the desquamative degeneration.  They are
seen in comparatively  few cases:  on  referring to four, of which I have drawings or
memoranda,  I find two to have been congested and waxy kidneys, with slight exuda-
tion;  one to  have been a  soft and desquamating kidney, also with slight exudation;
and one a granular kidney with numerous cysts, from the size of a pea to that of  a
hazel-nut.  On the other hand, I have examined organs in every stage of desquama-
tive disease without finding these bodies,  the production of which cannot therefore
be an essential step in  the  degeneration and atrophy of kidneys so affected.
   " The origin and progress of these  vesicles is very obscure.   It is not improbable
that, as Mr.  Simon asserts, they are transformed into the larger  cysts visible to the
naked eye: though I confess that I have not been able to trace the intermediate steps
of their progress in a satisfactory manner.  On the other hand, their origin from
extravasated  epithelial cells seems exceedingly improbable; indeed, I have already
stated, that I do not think the epithelium ever becomes extravasated.   Moreover, the
vesicles in question have all the appearance of  being formed iviihin the tubes,
although they afterwards become  separated from them.
   " From the occasional appearances of alternate distention and constriction pre-
sented "by the tubes when undergoing obliteration, I am induced to believe that cysts
may be formed by the occlusion and isolation of portions of tube  which have not yet
lost their power of secretion.  Whether the vesicles in  question are formed in this
way,  can  only be determined by close and repeated  observation ; and I have not been
able to obtain demonstrative evidence on this point.
   " The larger cysts in the kidney present very strong evidence of being formed in
connexion with the secreting membrane.   In one instance, I found their inner surface 
478                '         THESOLIDS.
to be lined at some points with  tessellated epithelium, in the form of pentagonal or
hexagonal  flattened cells, with circular  nuclei; in another case, there were oval
nuclei without any distinct cells, and a large number of free oil globules of consider-
able size.   The existence of oil in these cysts has also been observed by Dr. Johnson.
Other products of secretion are also occasionally found.   On one occasion I found
several cysts in a kidney, otherwise healthy in appearance, which  contained a turbid
ochrey-coloured liquid, presenting under the  microscope numerous  minute crystals
of uric acid.  Mr. Simon mentions having found on two occasions xanthic oxyde in
considerable proportion.   I have more than once observed them to contain blood in
large quantity;  and I have likewise found them full of a matter like stiff glue.
  " The occurrence of cysts  in kidneys presenting a generally healthy structure is so
frequent, as to lead to the idea that they must be in such cases the result of disease
which has been arrested before any considerable  disorganization has  taken place.
Many of the cases of partial atrophy of the  kidneys figured by Rayer  are probably
due to the rupture or obliteration of these cysts.
  " Before leaving the subject of cyst-formation, I may state, that in one instance I
have observed the Malpighian  capsules to  be occupied by distinct cysts.*

  " Dilatation and Thickening of the Tubes.—This condition, although by no means
a very frequent one, is  important, as being characteristic, so  far as I have observed,
of the extreme stage of what I have called the 'waxy degeneration.'  I have scarcely
ever seen it unaccompanied  by entire obliteration of the vessels, and by  enlargement
and increased density of  the kidney.  The organ has the dense resistant feeling of
fibro-cartilage, and both cortical and tubular  portions have the light yellow  colour,
and the appearances described above as those of the waxy degeneration in its last
stage.  The striae of the pyramids appear to radiate indefinitely towards the surface,
and meet the cortical substance in digitations, instead of being marked off by a sharp
semi-circular line, as occurs in the healthy kidney.   When examined with a simple
lens, or even the naked eye, the pyramidal striae  are seen  to pursue an unusually
sinuous course: this is peculiarly the case where they pass into the cortical substance.
   "Moreover, the pyramids are unusually broad at the bases; and the length of the
straggling digitations is sometimes so great, that I have measured fully an inch and
a half between the extreme end of the striae and the corresponding papilla.   Never-
theless, the cortical substance is not usually diminished in  quantity, being developed
to a great extent between the  pyramids.
  " This condition I have ascertained to proceed from dilatation and thickening of
the tubuli uriniferi throughout the organ.  The dilated tubes are usually twisted and
varicose, as may be seen  by inspecting a section of the pyramids with a low power.
When examined with a higher power, the section presents an appearance very similar
to some tumours (of the fibrous or fibro-cysted kinds), viz:  a number of compressed
areolae, enclosed by fibrous tissue, and presenting an  appearance of irregular con-
centric rings, of various distinctness, (an effect apparently due to the peculiar refrac-

  *  Obs.  In one case of cystic disease of the kidneys which fell under the notice  of
Mr. Quekett, the formation  of the  cysts  evidently commenced in the corpora Mal-
pighiana beneath the capillary  plexus.—A. H. H. 
GLANDS.
479
tion  of light by the thickened membrane.)  The nuclei are obscured or invisible
owing to the thicknass of the intervening wall, but nevertheless exist in considerable
numbers.   The Malpighian bodies and capillaries are usually obliterated.  The kidney
nas in fact become, like  the  tumours  whose structure it resembles, a true  non-
vascular texture.
   "The explanation of the peculiar extension  of the pyramidal striae towards the
surface in these cases, is to be found in the fact that, even in the normal condition
the convoluted  tubuli have a  general  disposition from the  bases of the  pyramids
towards the surface, in the direction of the striae of the cones.  This is evident from
the facility with which the gland tears in that direction; although in the normal state
this disposition is  masked by that of the vessels, which, passing in straight lines
through the cones, break into a complicated net-work of capillaries at the bases of
the pyramids.  In the present lesion, the vessels having disappeared, and the course
 of tubes being strongly marked, their disposition towards the surface becomes mani-
fest, and the abrupt line of demarcation between the cortical and pyramidal substance,
caused by the presence of the vessels, is obliterated."
                               CONCLUSION.

  With  the view of enabling  the reader  to  place  the  foregoing  observations in
relation with the descriptions found in systematic pathological works, Dr. Gairdner
subjoins  the following short remarks  on the principal physical characters  usually
ascribed to diseased kidneys:

   "Increase of Size and  Weight: Hypertrophy.—Enlargement of the  kidney occurs
chiefly in consequence of three conditions:—1st, from sanguineous engorgement;  2d,
from distention of the tubes by secretion or  exudation;  3d, from permanent dilatation
and thickening of the tubes.   Of all  these causes, the second is  by far the most
common.   The last is characteristic of the  waxy degeneration formerly described.
  "The quantity of liquid in the tubes is, at all times, subject to so much variation,
that it is difficult to say what amount of increase of weight may be thereby occasioned
without the existence of any positively morbid condition.  It is not very uncommon
to find kidneys, otherwise not differing from the healthy standard, about double the
usual weight, or between seven and eight ounces each.  I have more than once found
them to weigh nine ounces each, with very slight marks of disease.  When the weight
much exceeds this, it  is probable it arises from the rare combination of vascular and
tubular engorgement.
  " In kidneys containing oleo-albuminous  exudation, the greatest increase of size is
attained,  when the exudation is universal, and  unaccompanied by desquamation.
  "Cystic degeneration of the kidneys, dilatation of the pelvis and ureters (Hydro-
nephrose, Rayer), &c., also give rise to great increase of size and weight.

  " Diminution of Size and Weight: Atrophy.—This condition sometimes occurs to
a certain  extent, in emaciated subjects, without any disorganization, owing to the 
480
THE  SOLIDS.
 diminished activity of secretion.  More frequently, however, it is the result of sepa-
 ration of the epithelium, followed by  contraction and  obliteration of the tubular
 structure.
   " Atrophy, from this cause, is liable to supervene in all  other varieties  of renal
 lesion, except the waxy degeneration, which appears to lead  to a permanently hyper-
 trophied condition of the organ.  In kidneys enlarged from exudation, the occurrence
 of desquamation and its  consequences is frequent; and the diminution of size in
 such cases is often not followed by a return to the natural condition, but by perma-
 nent atrophy.
   li The course of all disorganizing diseases of the kidney is  to produce first, enlarge-
 ment,  and then contraction  of the organ.   In the  extreme stages of the atrophy
 which results from exudation, exudation is often nearly absent.   When exudation,
 therefore, even  in  very sparing quantity, accompanies a contracted  condition of the
 kidney, there is a probability that it has been abundant at some former period.

  " Irregularities of  Surface:  Tuberculated and Granulated  Kidneys.—The  smooth-
 ness of the surface in the kidney is destroyed either by unequal dilatation or unequal
 contraction of the tubili of the cortical substance.  The former  takes place in the
 waxy degeneration ;  the latter, in the desquamative processes.
  " The most frequent irregularities of surface are  formed in  connexion with  the
 granulations  of Bright.   These are invariably formed when exudation is  deposited
 in kidneys tending to the desquamative lesion; and, as this runs  its usual course, the
 granulations become prominent from the destruction of the tubes around them.   An
 extreme degree of the irregularities thus  produced, constitutes the  tuberculated
 kidney.
  " The puckering and partial atrophy occasionally seen  in kidneys, otherwise not
 morbid, or comparatively  slightly  diseased, are probably,  in many instances,  the
 result of the obliteration of cysts.
  "The more remarkable changes in colour and consistence  are described very fully
 in many parts of the  preceding memoir."

  On reviewing the whole of the preceding observations,  Dr. Gairdner is induced to
 regard the following  conclusions as especially important in relation to the pathology
 of renal diseases:

  "1.  By far the greater part of the pathological lesions of the kidney arise from, or
 are connected with, the exudation of oleo-albuminous granules  into the interior of
 the tubes and epithelial cells.

  " 2.  The oleo-albuminous exudation is, probably, often preceded, and, certainly,
 occasionally accompanied, by vascular congestion; but when the quantity of exuda-
tion is considerable, more or less complete depletion of the vascular system invariably
 occurs.  This is a secondary result of the obstruction of the tubuli uriniferi.

  " 3. The oleo-albuminous exudation occurs in two chief forms, viz: first, universal
infiltration of the  tubes throughout the organ; and, second, infiltration of  peculiar 
GLANDS.
481
sets of tubules: the rest remaining free, or nearly so.  In the latter mode arise the
granulations of Bright.

  " 4. There is no essential anatomical difference between the exudations in the kid-
ney, which are the result of chronic processes, and those which have been considered
as the result of inflammation.

  " 5. The  capillary vessels of the kidney are subject  to spontaneous obliteration
(unaccompanied, in the first instance, by any visible lesion of the tubes), giving rise
to the peculiar affection which I have called the waxy degeneration.  This oblitera-
tion of the vessels is probably, in all cases, preceded by a stage of congestion.

  " 6. The consequence of the waxy degeneration is  thickening and varicose dilata-
tion of the tubuli throughout the organ.

  " 7. The tubes of the kidney are subject to contraction and obliteration, in conse-
quence of the desquamation of their epithelium; a condition resulting in atrophy, and
complete disorganization of the organ.

  "8. The desquamation of the epithelium occurs very frequently in all the other dis-
eased conditions of the kidney.  When sufficiently long-continued and extensive, it
produces contraction, and this indifferently, whether exudation be present or not.   It
is sometimes accompanied by  vascular congestion in every stage of its progress.

  " 9. The earlier stages of the exudations can only be discovered by means of the
microscope.   The progress of the waxy degeneration, on the contrary, is best traced
by the unaided eye.  The desquamation of the epithelium is only to be discovered
with certainty by means of the microscope, and is particularly apt to escape attention,
under all circumstances, if the kidney only, and not the urine, be looked to.  It results
that  careful investigation, both by the microscope and the naked  eye, both of the
kidney after death and the urine during life, are indispensable, to enable the patholo-
gist  to determine with exactitude the presence or absence of  disease."

   I have  been  induced to dwell thus  largely on the  microscopic
pathology of the kidney: first, on account  of the  great importance
and interest attached to the lesions of that organ;  secondly, from the
great number of interesting facts which  the microscope has already
brought to light in reference  to its  pathology; and,  thirdly,  in the
hope of inducing other  observers to  follow out more  completely the
inquiry which  has already led to such successful and striking results.
                                    31 
482
THE SOLIDS.
                               KIDNEY.
   [The  anatomy of the  kidney may be in part studied by dissection  of
recent specimens under water.  The structure, however, is more readily
made out after injection,  and this is best performed after removal from the
body.   An injection by either  set of vessels almost always  passes into the
others.   Hence  an injection by the  artery  frequently  fills  partially the
tubule uriniferi and the veins.   It  will be exceedingly difficult to limit the
injection to the terminations of the vessel injected; many trials, however,
will enable one to judge how much force is necessary to  fill only the set of
vessels desired.
   When three colours can be successfully employed, the best arrangement
will be found to  be—red or blue for the arteries, yellow for the veins, and
white for the urinary tubes.  When it  is required  to fill the three sets of
vessels with one  injection, the artery must be first injected, and the urinif-
erous tubes farther filled from the  ureter.   It may  be  here stated, that for
practise  in  making fine  injections, the kidneys of sheep, pigs, &c, will  be
found the organs most suitable for that purpose.  They are easily obtained,
are sufficiently difficult to inject, and do not require a very large amount
of material.
  Injections of the kidneys are  best preserved in Canada balsam without
heat,  after  being cut in slices, and dried.   Cells  may be  used or not,
according to the thickness of the specimen.

  Plate LXXV.  fig. 5,  Malpighian  bodies and their relation to the urinif-
                           erous tubes.
                 fig. 6, The same  enlarged, as in the first stage of Bright'g
                           disease.
 Plate LXXVI.  fig.  1,  Enlarged veins of kidney.
            "    fig. 2, The same ;  another view.
            "    fig. 3, Stellated condition of veins.
            "    fig. 4, Granulation on the surface of the  kidney.
            "    fig. 5, A  tube much dilated.] 
GLANDS.
483
                              TESTIS.
  The testis,  the last of the tubular glands  in  the  human subject,
agrees more closely in structure with  the sudoriferous  and ceruminous
glands than with the kidney; there being this in common between the
three first mentioned, viz: that the tubes, of which they are principally
constituted, are  convoluted, and are not enclosed in  a dense frame-
work of fibro-elastic tissue, as is the case with those of the kidney.
  The testis, is  invested by a tunic of white fibrous tissue; this sends
down, into the substance of the gland, numerous dissepiments, which
divide the tubes of which it is composed into  parcels, each  of which
may be called a lobe.
  The tubes of  the testes  are remarkable for their large size, great
tortuosity,  and  exceeding  and ready extensibility.  (See Plate LX.
figs. 1.4.)
  When viewed as opaque objects,  the tubes appear of a delicate
and semi-transparent whiteness;  and, when seen by transmitted light,
they are  almost  black; this arises from  the fact of the interception
of the luminous  rays by the cells contained within the tubes.
  The membrane of the tubes is  totally distinct from that of most
other tubular  glands;  it is very  thick and fibrous, being constituted
of a well-marked form of  nucleated  fibro-elastic tissue.  (See Plate
LX.fig.4.)
  The constitution of the  tubes of elastic tissue explains satisfactorily
their ready extensibility  and  variable  diameter; this variation, in
specimens prepared for microscopic examination, is very obvious, and
arises from the  displacement of the contained  cells, occasioned by
unequal  external pressure; where these  cells are accumulated in the
greatest  number, there the tubes are thickest;  and where  there are
but  few cells,  or even where the  tubes are destitute of cells, they are
thinnest, and frequently even entirely collapsed.
  These facts show that the tubes  are highly  expansive;  and there is
no doubt that their diameter varies, during life, in accordance with
the amount of seminal fluid contained within the testis; this expansive
property being  especially  designed to allow of the accumulation of
that fluid within the semeniferous organ.
  The tubes of  the testis contain a vast number of granular cells of
various sizes (see Plate LX. fig.  4), some  being  several times larger
than others, especially in the testis of the  adult.   Most of these cells
contain but a  single nucleus; in  others, however, and these  the larger 
484
THE  SOLIDS.
 cells, there are as many as from two to seven, or even more, distinct
 nuclei.  (See Plate XVI. fig. 1.)
   In the testes of a child, the granular cells present great uniformity
 of size, and contain, for the most part, but  a  single nucleus.  These
 cells, as in other tubular glands, form a regular epithelium on the walls
 of the tubes, the central channel being free; this arrangement is very
 evident in the tubes of immature testes;  but  far less  so in  those of
 the adult organ; the manipulation to which the latter are subject, when
 being prepared for microscopical observation, readily displacing  the
 cells.
   It  is in these  cells,  according  to the observations  of numerous
 observers, that the spermatozoa are developed.  For further particu-
 lars on the development of the spermatic animalcules, see the article
 "Semen."
   The tubes of the testes  are  loosely bound together  by bands of
 fibrous tissue;  it  is this  tissue  which  contains  the  tortuous blood-
 vessels with  which this organ is so  copiously supplied.
   That the tubes are not furnished with a distinct external envelope,
 like those  belonging to the kidney, is proved by the  fact that they
 admit readily of being separated from each  other, as also  of being
 drawn out to a great length: this last circumstance shows the extent
 to which the tubes are  convoluted, the few anastomoses which take
 place between them, and their extraordinary elasticity.


                      VASCULAR  GLANDS.

   The vascular glands all agree with each other  in the  abscence  of
 excretory ducts or channels for the discharge of their secretion, a
 deficiency  which involves as a necessary consequence the reception
 of the secreted fluids by the blood-vessels.
   From the differences in the size and structure of these several glands,
 it is very doubtful whether any other resemblance besides that just
pointed out exists between them, and it is most probable that each has
a separate purpose to fulfil in the animal economy.

                             THYMUS.
  The thymus, although usually spoken of and described as  a single
organ, is in reality double, and consists of two distinct glands united
to each other in the middle line by cellular tissue only.
  Each separate adult thymus is constituted  of numerous, probably 
                             GLANDS.                        4Q5

 some  hundred follicles, which vary in size  from a pin's head  to, in
 some  cases, that of a pea, and the walls of which are made up' of
 mixed fibrous tissue.
   These follicles are usually more or less  rounded, but sometimes
 polygonal in shape from pressure;  they are  loosely held  together by
 fibrous tissue, and by the blood-vessels which supply them;  they each
 contain in their interior a cavity which is more or less filled with a
 milky fluid.   (See Plate LXI. fig.  8.)
   Several of  these follicles open into each other and into a common
 receptacle  or "pouch," and  this last again opens  into the  internal
 cavity of the gland, the face of which is thickly studded with similar
 openings.
   On  its exterior each follicle may be seen, even without injection, to
 be invested with a very beautiful plexus of blood-vessels, represented
 in Plate LXI. fig. 8.
   When unravelled by the removal of the inter-lobular cellular tissue,
 the whole gland is seen to consist of a straight tube, with the follicles
 arranged around it in a spiral manner.
   The central cavity, "reservoir of thymus," is lined by a  delicate
 mucous membrane, which is raised into ridges by a layer of ligament-
 ous bands situate beneath it;  these proceed in various directions, and
 encircle the apertures of the pouches:  their use is to keep the lobules
 together, and  to prevent the injurious distention of the cavity.
   The whole  organ is enclosed in  a dense  capsule  of fibrous tissue,
 the blood-vessels contained in which are remarkable for their disposi-
 tion in three's, an arrangement which is not uncommon in the capsular
 investments of glands.   (See  Plate LXI. fig. 7.)
   The "milky fluid" contained in the follicles and reservoir is made
 up, to  a  great extent, of an immense  number  of granular  nuclei, as
 well as  numerous  cells  of large size, which do  not appear hitherto
 to have been either described or figured in a satisfactory manner, and
 which are probably to be regarded in the light  of parent cells.  (See
 Plate LXI. fig. 10.)
  Many of  these cells contain several granular nuclei, each of which
is surrounded  by one or more concentric lamellae; they thus resemble
the cartilage cells  found in the inter-vertebral  substance,  and also
certain species of Microcystis, a genus of Fresh-water Algae.
  Mr. Simon, in his " Prize Essay," makes the following observations
on the above-described  cells:—" In specimens taken from animals past
that period of life when the thymus is most active, I have found cells 
486
THE  SOLIDS.
in which these dotted corpuscles occupied the relation of nuclei.   The
cells are at first little larger than the corpuscles themselves, and contain
a perfectly pellucid material; but as they grow, their contents become
molecular, and they develope themselves into perfect fat cells, which
lie in the cavities of the glands, and  in  some instances completely
fill them.  During the period in which these cells are being developed,
the application of  acetic acid to the preparation as it lies under the
microscope shows  them to have great affinity to embryonic cells; for
the acid dissolves the cell-membrane completely away, and leaves the
nucleus of the cell (the dotted corpuscle) unaffected by its action."
  Lining  each follicle, Mr. Simon has detected a delicate and homo-
geneous structure, which he has termed the  " limitary membrane :"
this  structure is identical with the basement  membrane of Bowman,
and is probably common to all glands, especially the follicular ones.
  Mr. Simon has likewise described a lobular arrangement of the fol-
licles.  The structure  of the  gland  resolves itself, he  says,  "into
masses ranged round an axis.   Each mass constitutes a sort  of cone
of glandular substance, its apex pointing to the axis or  mesial line of
the gland; its base directed to the surface, where it presents innumer-
able vesicles; while  its intermediate  part  contains those  successive
branchings of the follicle which terminate superficially  in the vesicu-
lar form."
                          THYROID GLAND.
  The anatomy of this gland is best studied in a specimen which has
undergone a  slight enlargement of its several parts; a portion of such
a gland,  when viewed  with  the inch object-glass, bears  so close a
resemblance to a mass of fat, that, except by a practised miscroscopist,
it would be  impossible  to distinguish it therefrom with such a low
power;  even when  viewed with the  half-inch,  the illusion would
scarcely be dispelled, and it is only on  the application of the quarter-
inch glass, that misgivings would begin to be entertained in reference
to its identity with fat.
  The resemblance borne by a  portion of thyroid gland thus slio-htly
enlarged by disease to a mass of fat, arises from the form of the ves-
icles or closed cells  of which  the gland is  composed, and  from the
manner in which  they reflect  the light, the  centre of each vesicle
being clear and bright, and the circumference  dark and  almost black;
here, however, the resemblance  ceases, as the  thyroid vesicles are
most satisfactorily  distinguished from fat globules by their larger size,
the fibrous texture  of their parietes, and the nature of their contents. 
GLANDS.
487
  Such is  the  general  character and  appearance of a portion of
thyroid examined microscopically; the entire gland, however, consists
of two  lobes, which are placed one on each side of the trachea, and
which are connected with each other by a narrow slip, or isthmus of
the gland, and these lobes are further divisible into numerous lobules,
many hundreds to each lobe.  Now, it is these lobules which, so far
as the descriptions hitherto given of this  gland are to be understood,
have  been regarded and  described as  the membranous cavities of
the thyroid (see  Plate  LXI. fig. 1), the true and ultimate cellular
structure being in general overlooked.
  Thus  the lobules are further divisible,  each into  many small
cavities, the ultimate divisions of which the gland is susceptible.  (See
Plate LXI. figs. 2, 3, 4, 5.)   These  in the slightly  enlarged gland
are circular, and comparable to  fat vesicles (see Plate LXI. figs. 2,
3); but in the gland in its  normal state, they are compressed  and
angular, being  also very liable to be altogether overlooked, their size
and form  being  indicated  only by certain  light-coloured spaces
traversing the lobule.   (See Plate LXI. fig. 5.)
  Over the surface of  each lobule, the blood-vessels  form a plexus,
from which branches proceed inwards, encircling the  vesicles much
in the same way as the blood-vessels do the fat corpuscles.  (See
Plate LXI. fig. 1.)
   The cavity of each vesicle is perfectly distinct, and does not com-
municate  with that of any other  of  the vesicles by which it  is
surrounded:  the  fibrous tissue,   however, of which its  walls  are so
evidently composed (Plate LXI. fig. 4), does communicate with and
run into that of the neighbouring vesicles, at certain points, however,
only.  These fibres may frequently be  traced from the wall of one
cell into that of another; and it is this fibrous union  of the vesicles
which renders it impossible completely to isolate any one of the cells,
and accounts for the fact, that when the vesicles are broken up with
needles, they are entirely reduced to  fibrous tissue.
   The contents of the vesicles consist of a fluid, containing numerous
granular nuclei of a rounded or oval  form, as well as of a few perfect
cells, two  or three  times larger than the nuclei, and the  granules
contained  in which are very large, presentingan oily aspect; between
these two extremes of size, other cells intermediate are met with: the
larger are  evidently parent cells.  (See Plate LXI. figs. 9 and 4.)
   The fluid of the vesicles contains a good  deal of oil,  which, when
the gland is slightly decomposed, is apt to collect in them in  the form
of one or two large circular discs. 
488
THE  SOLIDS.
  The increase in the size of the gland in goitre is due to an increased
development of the vesicles and of their contents.
  It is evident that each vesicle contains all the elements of the gland,
and that the entire organ is made up of an assemblage of many thou-
sands of such vesicles or glands.   (See Plate LXI. fig. 2.)

                       SUPRA-RENAL CAPSULES.
  The supra-renal capsule bears some resemblance in structure to the
kidney, being divisible like it into a cortical and medullary substance.
  It is made up of numerous simple and cylindrical tubes, closed at
both ends, and formed  of structureless  basement membrane;  these
tubes are disposed  in a vertical manner, one extremity forming the
surface of the organ, and the other extending in an opposite direction,
as far as the inner  cavities or  lacunae  situated in the centre of each
supra-renal capsule.   (See Plate LXII. fig. 3 a.)
  These tubes  enclose  elements  of three kinds; first,  innumerable
circular particles  or molecules,  which reflect the light strongly, and
which are of an oily  nature; of these  the greater part is free in the
tubes, but a lesser proportion is enclosed  in certain of the cells which
are  met with in the tubes;  second, granular nuclei in large quantities;
and, third, parent cells of considerable size, containing each  several
nuclei intermingled with, and in part very frequently obscured by a
considerable number  of the bright molecules previously referred to.
These parent cells do not appear to have been hitherto characterized
with any degree of precision.   (See Plate LXII.  fig. 3 b.)
  The differences between the  cortical and medullary portions of the
supra-renal capsule, depend principally upon the  irregular disposition
of the tubes in the latter, the  plexiform arrangement of the vessels,
and on the presence of numerous parent cells containing more or less
of colouring matter in their interior.  It  is these cells which impart
to sections of the  gland the dotted  appearance so  commonly observed
in its medullary portion.   (See  Plate LXII. fig. 3.)
  The vascular distribution in the supra-renal is very  simple. . On
the surface of the  organ we have a very beautiful  plexus of capillaries,
the  pentagonal  and hexagonal  meshes of  which  lie in the intervals
between the extremities of the  tubes;  in the tubular part the vessels
both veins and arteries run, in straight  lines between the tubules,
terminating, on the one hand,  in the plexus on  the surface, and, on
the  other, in the central plexus.  (See  Plate LXII. figs.  1. 5.)
  The supra-renal is  an organ which varies greatly in different sub- 
GLANDS.
489
jects; in some the proportion of granules  is much greater than in
others ; in others again, the central lacunae  are occupied with  a
whitish-looking substance, which, on examination, is found to consist
of granular nuclei  arranged in irregular masses, but in which some-
times we can detect a tubular disposition: in these cases we encounter
from without inwards, three substances;  cortical, medullary, and then
lastly, the central substance just described.
   The capsule of the supra-renal is often laden with fat, which totally
obscures the plexus on the surface of the organ.
   The  parent cells,  when filled  with oily molecules, bear a  close
resemblance to the cells of a sebaceous gland, between which and the
supra-renal capsule one would hence be disposed to suspect a degree
of affinity.
                               SPLEEN.
   The spleen consists of a fibro-elastic capsule which  sends down
from its inner surface septa, which penetrate  the  organ in  all direc-
tions, and divide it into compartments;  of an immense assemblage  of
blood-vessels which compose its chief substance, and which impart to
 it the character and appearance of an erectile tissue; and, thirdly and
 lastly, of a small quantity of secreting structure, consisting of nuclei
 only, and which appears to lie in  the  intervals between the blood-
 vessels.*   (See Plate LXII. fig 2.)
   The above comprehends all that can be readily made out of structure
 in the spleen: the examination, however, of this organ is by no means
 satisfactory or easy on  account of  the impossibility of fully injecting
 it, a difficulty which arises from causes  but imperfectly understood.
  ' Dr. Julian Evans,  however, describes a very elaborate  structure
 and arrangement of the tissues in the spleen, as will  be seen from the
 perusal of the following abstract of his paper, taken from the  third
 edition of Carpenter's "Principles of Human Physiology."

   " According to the account of Dr. Julian Evans.f whose  researches
 appear to have been more successful than those of any other anato-
 mist, the  spleen  essentially consists of a fibrous membrane, which
 constitutes its exterior envelope, and which sends W^TZuK
 directions across its interior, so as to divide it into a number of minute
 cavit rsor  lacunae of  irregular form.   These splenic  lacuna  corn-
 muilicl freely with each other, and with the ^™^™\^
 are lined by a continuation of the lining membrane of  the  latter,
       *See Med. Chir. Rev. No. X. p. 28.      \Lancet, April 6th, 1844. 
490
THE  SOLIDS.
which is so reflected upon itself as to leave oval or circular foramina
by which  each lacuna opens into others,  or into the splenic  vein.
The lacunae, whose usual diameter is estimated by Dr. E. at from hall
to one-third of a line, are generally traversed by filaments  of elastic
tissue, imbedded in which a small artery and vein may be frequently
observed; over these filaments, the lining  membrane is  reflected in
folds; and, in  this manner, each  lacuna is incompletely divided into
two or  more smaller compartments.   There is no direct communi-
cation between the splenic artery and the interior of the lacunae; but
its  branches are  distributed  through  the  inter-cellular parenchyma
(which will be presently described); and the small veins which collect
the blood from the capillaries of the organ convey it into these cavities,
from which it is conveyed away by the  splenic vein.   The lacunae
may be  readily injected from  the splenic vein with either air or liquid,
provided they  are  not  filled with coagulated blood; and  they are so
distensible, that  the organ may be made to dilate to many times its
original size with very little force.   This is especially the case in the
spleen  of the  Herbivora; for the spleen of a sheep weighing four
ounces,  may be  easily  made  to contain thirty ounces  of water.
That of man,  however, is less  capable of this kind of enlargement.
According to Dr. Evans, the lacunae of the spleen never contain any
thing but blood: and he notices that a frequent condition of the human
spleen after death, which is sometimes described as a morbid appear-
ance, consists in the filling of the lacunae with firmly coagulated blood,
which gives a  granular appearance to  the organ.
  "The partitions  between the lacunae are formed, not  only by the
membranes already mentioned, but by the peculiar parenchyma of the
spleen;  which constitutes a larger part of the organ in man, than in
the Herbivorous Mammalia.  It presents a half-fluid appearance to the
eye; but when an attempt is made to tear it, considerable resistance
is experienced, in consequence of its being intersected by what appear
to be minute fibres.  When a small portion of it is pressed, a liquid is
separated: which is that commonly known as the Liquor Lienis, or
splenic blood;  which is usually described (but erroneously, according
to Dr. E.) as filling the lacunae of the spleen. This liquid, when diluted
with serum, and examined under the microscope, is found to contain
two kinds of  corpuscles—one  sort being  apparently identical with
ordinary blood corpuscles, and the other with the globules character-
istic of the lymph, and  abundant in the lymphatic  glands.  The
remaining fibrous substance consists entirely of capillary blood-vessels 
GLANDS.
491
and lymphatics,  with  minute corpuscles, much  smaller than blood
corpuscles, varying  in size from about l-6000th to l-7000th of an
inch, of spherical form, and usually corrugated on the surface.  These
lie  in great numbers in the meshes of the  sanguiferous capillaries;
and the minute lymphatics are described by  Dr. E. as connected with
the  splenic  corpuscles, and apparently arising from them.  Lying in
the midst of the parenchyma, are found a large number of bodies, of
about a third of a line  in  diameter, which are evidently in close con-
nexion with the vascular system; these have been long known as the
Malpighian bodies of the  spleen, after the name of their discoverer;
but since his time, their existence has been denied, or other  appear-,
ances have been  mistaken for them.
  "According to Dr. E., they in all respects  resemble the mesenteric,
or lymphatic glands  in miniature, consisting as they do of convoluted
masses  of blood-vessels  and  lymphatics,  united  together by elastic
tissue, so as to possess considerable firmness:  and they further cor-
respond with them in this—that the lymph  they contain, which was
quite transparent in their afferent lymphatics, now becomes somewhat
milky, from containing a large number of lymph globules."

  Dr. Handfield Jones has noticed the occurrence of certain peculiar
corpuscles in the spleen of various animals, including  that of fishes,
mammals, and man; these corpuscles he describes as follows:*
  "In the spleens of various animals there may often be seen a number
of minute corpuscles of a yellow colour, varying from a dark to a pale
hue; they occur sometimes singly, but mostly in groups, which I have
sometimes thought were  aggregated, especially along the larger blood
canals.   These groups are made up of corpuscles of very  various
size; they do not appear to have  any special connexion with the
surrounding substance, which occasionally,  however, has a decided
yellow tinge.
  "In the animal series,  I have found these corpuscles most highly
developed in fishes.  In  the  human subject, they  are  rarely to be
found.  I have, however, observed them distinctly in six instances, in
one  of which  they were very large and numerous. In most of the
cases in which  they were  found, there had been considerable  inter-
ruption  to the respiratory process.  The spleen  was generally much
enlarged, soft, and of rather a pale colour, quite an opposite condition
to that often observed in cases of'Bright's Disease,' where the organ
                    * Medical Gazette, 1847, p. 141. 
492
THE  SOLIDS.
is found  small  and contracted:  in  such spleens I have never found
any of the yellow corpuscles."
  For a description to the Pineal and Pituitary glands, placed in the
classification under  the  heading "Vascular Glands," the reader is
referred to the Appendix.

                         ABSORBENT  GLANDS.
  The absorbent system of vessels  is divisible into lacteals and lym-
phatics, the  glands attached  to  the former being called mesenteric,
and those to the latter, lymphatic glands.
  The lacteal absorbents commence in a plexiform manner in the
villi of the small intestines, while the lymphatic absorbents originate
all over the body, in the same manner, in each of the  several tissues
and organs of which it is composed: they are minute, delicate, and
transparent vessels, remarkable for  their uniformity of size, a knotted
appearance due to the presence of numerous valves,  the dichotomous
divisions which occur in their course, and their separation into several
branches immediately before entering a  gland.*
  In the mesentery, the lacteals  become variously coiled and  knotted,
these  aggregations of coils,  together with fibrous tissue  and blood-
vessels, forming the  mesenteric  glands; the lymphatic glands have a
similar structure and origin, being placed in certain determinate
regions of the human body.
  The lymphatics which enter  a gland, or the afferent lymphatics,
vary in number from two to six; they divide at a short distance from
the gland into several smaller vessels, and enter it by one of  the flat-
tened surfaces: while those which leave it, or the efferent lymphatics,
escape from the gland on the opposite, but not  unfrequently on the
same  surface; they also consist,  at their junction with the gland, of
several small vessels, which unite after a  course of a few lines, and
form  from  one to three  trunks, often  twice as large as the afferent
lymphatics.
  The afferent lacteals  and  lymphatics,  as they enter the gland,
become somewhat dilated; and  the epithelium, in place of forming a
single layer  of flattened cells firmly  adherent to the walls of the tubes,
consists of several layers of  rounded and  glandular cells, which are
very  readily displaced.
  These cells are doubtless more or less concerned in the elaboration
  f See the Article "Lymphatic System," by Mr. Lane, in the Cyclopedia of Anatomy
and Physiology. 
GLANDS.
493
of the fibrin of the chyle;  and there is much reason to believe that
from time to time the more mature cells become detached from the walls
of the lacteals. and are conveyed along with the chyle into the blood,
where they become the white or granular corpuscles of that fluid.
  Such is a very brief outline of the minute  anatomy of the  mesen-
teric and lymphatic glands.
  This is probably the most fit  place  to introduce a few remarks on
the structure of the villi themselves, the chief agents in  the  absorp-
tion of the  chyme, and  the parts in which the lacteals themselves
take their origin.

                    The  Villi of the  Intestines.
  The villi exist in the whole extent of the small intestines, but it is in
the lower part of  the  duodenum and  the whole of the jejunum that
they are best developed, and the lacteals most readily detected.
  Several distinct structures have to be noticed and described enter-
ing into the  constitution of each  villus:  these  are the epithelium
resting upon the outer surface of the villus, the basement membrane,
the intra-villous nuclear contents, the fatty  intra-villous contents,  the
blood-vessels of the villus and its lacteals; these several parts will be
described in the order of their enumeration.
  The epithelium investing the villi (see Plate LII. fig.  1), is  of  the
conoidal variety, already fully described and figured.  It  not  merely
clothes  the villi from base  to summit;  but also the inter-spaces
between them, as well as the numerous follicles of Lieberkuhn, situated
in the whole length of the small intestines.
  According to the observations of Professor Goodsir, this epithelium
is shed on each recurrence  of the process of chymefication, the cells
first absorbing  the  partially  elaborated chyme,  effecting a  further
elaboration of it, and finally becoming ruptured and dissolved,  set free
the fluid absorbed, at  the same time  adding their own substance to
augment its amount and nutritive qualities.
  The accuracy of this view is  in the main admitted by most  observ-
ers ; Professor Weber and  Dr.  Jones, however, do not consider that
the shedding of the epithelium is necessary to enable the villi to per-
form  their function;  and the latter observer makes the following
remarks  on this point:  " I have certainly seen the villi clad with their
epithelium  when the lacteals have  seemed to be every where filled
with chyle:  however,  I think there can be little doubt that, when the
absorbing process is most  actively  performed, the villus does throw 
494
THE  SOLIDS.
off its protecting  covering; certainly,  this  is the case  in a great
number of instances."*
   The basement membrane of the  villi is a continuation of that of
the general  surface of the mucous membrane, and is, as  far as has
yet been ascertained, perfectly structureless.
   The granular, or, more correctly speaking, the nuclear contents of
the villi have been noticed by several observers.  (See Plate LII. figs.
1, 2).  Dr.  Jones, however,  in the communication already referred
to, has pointed out the fact that the nuclear and granular contents of
one villus are continuous with those of another, and that the granules
and  nuclei form a  continuous stratum lying beneath the basement
membrane,  extending  not  merely from  villus to  villus,  but also
throughout  the large  intestines, where  it is  very  easily seen in the
spaces between the follicles.
   Professor Goodsir has described these granular nuclei, as enlarging
during the process of absorption, and as forming a number of enlarged
and  very evident cells  at the  apex of the villus.   These  supposed
cells, however, are nothing more  than oil drops, usually of a brown
colour, and  of various sizes.  (See Plate  LII. fig. 2.)  At this con-
clusion  I  arrived many months since, and gave a figure of these oil
drops in the villi in the 13th Part of the Microscopic Anatomy, pub-
lished in  April,  1848;  and I  am glad  that  Dr. Jones entertains  a
similar opinion of their nature.  I may at the same time remark, that
the cells delineated  in the original  figure given by Professor Goodsir,
have all the characters of oil drops, being round, smooth, and reflect-
ing the light strongly.
   The use of these  oil drops in the villi is by no means evident;  they
are formed, in  all probability, by the cohesion of the smaller oily
granules which are  scattered  throughout  the villi during the process
of absorption, and  which contribute so greatly to  their opacity; in
the end, they are most probably absorbed by  the lacteals.
   Notwithstanding, however, the non-existence of  the peculiar cells
described by Professor Goodsir, the leading idea of that observer of
the elaboration of  the chyme within  the villus is still correct, the
agents in this work being the nuclei already described.
   The presence of these nuclei throughout the whole length of the
villus seems to  point  to the  inference that it is  not the apex only
which absorbs.
   Each  villus is copiously supplied  with blood-vessels;  an  artery
                   * Medical Gazette, Nov. 17th, 1848. 
GLANDS.
495
ascends one side of the villus, a vein descends along the opposite side,
and between these two principal vessels a very complicated and beau-
tiful plexus of capillaries is extended.   (See Plate LI. figs. 3, 4, 5.)
  The lacteals are described as originating in the villi in a plexiform
manner.
  In the rabbit I have observed a  very curious construction of the
villi, their surfaces  being studded with numerous mucous  follicles;
the portion of intestine exhibiting these characters was most probably
taken from near the junction of the large and small intestines; and 1
have little doubt but that the villi of the  human intestine, in a corres-
ponding position, would  exhibit the same combination of the struct-
ural peculiarities of  both small and large intestines.
  The anatomical characters of the mucous  membrane of the stom-
ach, and  large intestines, have  already  been described.   (See page
339. et seq.) 
49G
THE SOLIDS.
                       VILLI OF INTESTINES:
 [The villi of the intestines can only be examined satisfactorily after injection,
and the removal of the  epithelium.  They may be seen, but not so well, in
the recent intestine, after the epithelium and mucus have been well washed
off, on examination under water with a low power.  In the fowl and dog, as
in many other animals, the villi are longer than in the human subject.  The
intestines may be injected with the other chylopoietic viscera from the vena
portae, or they may be injected alone  from the superior and inferior  mesen-
teric vein, or any portion of the intestinal canal may be isolated by applying
ligatures above and below the portion to be injected, containing the intestine
and mesentery, and the pipe of the syringe then placed in the largest mesen-
teric vein discoverable in the isolated portion.
   After the injection has set, the intestine must be placed in water, to allow
the epithelium to  become detached,  and the  mucus removed.   It will  be
sometimes necessary to  wash the  internal coat  of the intestine with water
from a syringe.   These injections are best preserved in cells  and in fluid.
Sometimes  it will be found desirable to preserve longer portions of intestine
than can be contained in cells of the usual size;  for this purpose, the built-
up cells already described will be of service, as they can be made of almost
any size.
  When the villi are long and well filled, the vessels are sometimes beauti-
fully shown in transverse sections, mounted in balsam without heat.

  Plate LXXIV., fig. 5, Villi of duodenum.
    "     "      fig. 6, Villi of jejunum.
  Plate LXXV., fig. 1,  Villi of ileum.
    "     "     fig. 2,  Muscular fibre of small intestine.] 
ORGANS OF  THE SENSES.
197
          ART.   XXII.—ORGANS  OF  THE  SENSES.

                              TOUCH.
                 Papillary Structure of the Skin.
   The sense of Touch is the simplest as well as the most universally
 diffused of the senses, it not merely extending over every portion of
 the external surface of the body, but also over certain of the internal
 mucous surfaces, as those of part of the mouth, nose, &c.
   Over the general  surface of the body this  sense exists under the
 form of common sensation; and it is only in certain parts, as on the
 palmar and plantar surfaces of the hands and feet, that it becomes so
 highly developed as to assume the  importance of a distinct sense, and
 to deserve the name of Touch.
   This sense has its seat in the papillary structure of the skin, and
 the degree of the development of this structure, as shown by the size
 and  number of the papillae, is always proportionate to the degree of
 perfection of the sense: thus, the papillae over the general surface of
 the body are much less numerous and  less perfect in form than they
 are in the palms of the hands and  soles of the feet.
   The  papillae in the natural  state are of course invested  by the
 epidermis, which indeed conceals them to a great extent  from view;
 this requires to be removed by maceration before their form, size, and
 arrangement can be clearly ascertained.
   After the removal of the epidermis,  it will be seen that the papillae
 on the general surfaces of the body do not follow any definite arrange-
 ment, but are scattered here and there without apparent order,  more
 or less thickly according to the degree in which the part of the integu-
 ment upon which they are seated is  endowed  with sensation, but
 every where they are less numerous than on the  palmar and  plantar
 surfaces of the hands and feet.   (See Plate LXIII. fig. 4.)
   On the  palms of the  hands and soles of  the feet, the  papillae are
 arranged,  as may be seen with the naked eye, in lines or ridges, each
 ridge being made up of two rows of papillae in single file, and between
 each pair  of which a further line of separation may be  traced:  such
 is the general disposition of the papillae in each ridge;  the  ducts of
 the sudoriferous glands pass through its centre and between the rows
of papillee, the number of these glands and  ducts to that of the papillae
being in the proportion of one to four.   (See Plate LXIII. fig. 3.)
                             32 
498
THE  SOLIDS.
   The arrangement just described can be well seen on the palms of
the hands  by the aid of a lens, even while  the  epidermis is still
attached to the cutis;  the  ridges are seen  to  be disposed here and
there in beautiful curves, some abruptly coming to a termination, and
others dividing into two distinct ridges, this  disposition enabling them
to adapt themselves more accurately to the varying nature  of the
surface over which they are extended: along the middle of each ridge,
the apertures of the  numerous sudoriferous glands may be seen for
the most part crossed in the direction of the diameter of the ridge by
a faint groove, which indicates the  line of separation  of the papillae
into pairs.   (See Plate LXIII. fig. 1.)
   Each  papilla  appears  to consist  of a prolongation of basement
membrane, and contains in its interior granular and nuclear contents
and a single looped blood-vessel, (see Plate LXIII. figs.  3.  7):  these
points of structure are all made out readily enough; the chief difficulty
consists in  the determination of the manner in  which the nerve fila-
ments, with which the papillae are undoubtedly supplied, terminate in
them.  On this subject, Messrs. Todd and Bowman* have the follow-
ing observations:—"In regard to the presence of nerves in the papillae
themselves, we can  affirm  that we have  distinctly traced solitary
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 distinguish them in such situations from other textures.
Thin vertical sections of perfectly fresh specimens are essential for this
investigation, 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 observations, we do not deny the existence
of true loop-like terminations as figured by so respectable an authority
as Gerber; but neither do we  feel entitled to assent  to it.  . . .   We
incline to  the belief that  the  tubules, either entirely  or in a  great
measure, lose the white substance when within the papillae."
   Messrs.  Todd  and Bowman further observe, in reference to the
structure of  the  papillae:—" Within  the basement membrane it  is
difficult to  distinguish any special tissue, except by artificial modes of
preparation.  A  fibrous  structure,  however,  is apparent,  having a
more or less vertical arrangement;  and with the help  of solution of
potass, filaments of extreme delicacy, which  seeem to be of the elastic
kind, are generally discoverable in it."
                    * Physiological Anatomy, p. 412. 
ORGANS OF  THE  SENSES.
499
  The blood-vessels of the papillae consist of single loops; each of
these is made up of  an artery and a vein: the former, derived from
the arterial plexus of the cutis, ascends the  papilla on one side, and
on reaching its summit gradually merges into the vein which descends
along its opposite  side, and terminates in the venous plexus of the
cutis.   In an injected preparation, and where the  villi are large, the
turn of the loop is seen to be very abrupt, the two vessels, the artery
and the vein, coiling round each other, and resembling a piece of
twine which has been bent upon itself and  afterwards twisted in  a
spiral  manner.  This disposition of  the  vessels seems  intended to
delay somewhat the passage of the blood through  the  papillae.   (See
Plate LXIII. fig. 7.)
   The  thickness of the epidermis which so closely invests the papillae,
does not appear to  have  any direct relation to the sense of touch:
thus, over the general surface of the body, where this sense exists
only as common sensation, the epidermis is very thin, while over the
palmar surface of the hands it is very thick;  the epidermis must not
be  too thick, however, even in this situation, as is shown by the fact,
that where it has been greatly thickened by manual labour, touch  is
totally obscured.
   The  density of  the epidermis in certain situations is evidently due
to  pressure,  and may be explained by the  fact that such pressure
induces an increased determination  of blood to  the  part, which  is
followed  by  increased  nutrition and development.  Between  the
sense of touch  and the  number of sudoriferous glands, there would
appear to  be  a certain  relation: thus, on the palmar aspect  of the
hands, where this  sense exists in  its highest perfection, the number of
sweat  glands is very great.
   The  use of these glands in this situation in such increased numbers,
may readily be conceived to be to keep the epidermis  in a moist  and
flexible condition, whereby impressions would be  more  readily con-
veyed to the papillae and more  distinctly felt, the acuteness  of the
entire  sense being thus greatly augmented.
   The  epidermis  is  very accurately adapted to the papillae, so that
when detached and  viewed upon its under surface, it is seen to con-
tain exact impressions of each and all of them; it is in  this manner
that their form, size, number,  and arrangement  are best studied, and
it will  then  be noticed that,  in all these particulars,  considerable
variations exist.   (See Plate LXIII. figs. 5, 6.) 
500
THE  SOLIDS.
                         PAPILL/E  OF SKIN:
  [The papillae of the skin  may  be examined in  their recent state  on
detaching the epidermis after slight maceration: the papillae may then be
viewed  in thin transverse sections of the skin, as directed in the prepara-
tion of the sudoriparous glands.  The loopings of the vessels investing the
papillae, can only be seen after injection.   In some  cases of very success-
ful  minute injection of the whole body, the  capillaries of the  skin  will be
found filled;  but this success is rare, except in fcetal subjects.   Injections
of the  skin  may sometimes be  made of one  extremity—as one arm, or a
hand or foot.  In these attempts, the injection must be made by the vein.
  When success is obtained, those portions of skin that show best the papillae,
and these will be found on the palmar surface of  the  hand and fingers,
may be preserved in cells with fluid.  Other portions should be allowed to
dry, and transverse sections made and mounted in balsam.] 
ORGANS OF  THE  SENSES.
501
                              TASTE.
   Papillary Structure of the Mucous Membrane of the Tongue.
  The mucous membrane of the tongue, the principal, if not the sole
seat  of the sense of taste, is divisible, like the skin, into a chorium, a
papillary structure, and an epidermis or epithelium.
  The chorium is a firm and tough membrane, formed of mixed fibrous
tissue, and containing in its substance  the  blood-vessels  and nerves,
arranged in a plexiform manner, from which the papillae are supplied:
to its under surface the extremities of the mascular fibres of the mus-
cles of the tongue are firmly attached;  this arrangement imparts to
the whole organ a  considerable  power of movement and of  nice
adaptation.
  The papillary structure, which is the real seat of the sense of taste,
is constituted of an immense number of papillae, which occasion a
somewhat flocculent appearance of the whole surface of the tongue.
  The papillae are divisible into simple and compound, and the latter
again into filiform, fungiform, and calyciform;  besides these  several
compound forms, however, others exist of no very definite shape, but
approaching more  or less  closely in their characters to either the
fungiform or calyciform papillae.
  The simple papillae exist principally on the sides and under surface
of the tongue, but also, though more sparingly,  on its upper surface,
as between  the filiform papilae,  in  the space around the base of each
fungiform papilla, and for a short  distance behind the calyciform
papillae, and to  either side of them.  (See Plate LXV. fig.  10.)
  They vary somewhat in size, form, and structure in different situa-
tions ; in general they are much pointed  at their extremities:  behind
the calycform  papillae they  are  obtuse  and  pyriform  in shape, (see
Plate LXV. fig. 11,) while on the under surface of the tongue their
extremities are very frequently perforated,  and  they appear to serve
the double purpose of a papilla and mucous follicle.   (See Plate LXV.
fig- 2.)
  They each consist of, in addition  to their epithelial investment, a
laver of basement membrane, a single looped blood-vessel, filaments
of nerves, and granular and nuclear contents.   (See Plate LXV. fig.
6, and Plate LXVI. fig. 5.)
  The compound papillae are confined to the upper surface  and edges
of the tongue, and do not extend, except for  a  short distance  at the 
502
THE  SOLIDS.
sides, over the space bounded in front by the calyciform papillae, and
behind by the epiglottis.  This chain of papillae forms* the extreme
boundary of the space over which the sense of taste extends, the surface
behind it being smooth, non-papillary, and exhibiting numerous open-
ings of mucous glands; thus then  it would appear we have  a true
gustatory region.
  Each compound papilla is made up  of numerous simple papillae,
arranged differently in the case of the three forms of these  already
enumerated.
  The filiform papillae are  by far  the  most numerous, being more
than in the proportion of twenty to  one; when freed from epithelium
they are  seen to be more or less cylindrical in  form, and to  consist
of a variable number  of simple papillae, from  sixteen to twenty  or
more to each, arranged in a single circular series, forming the top and
margin of the cylinder.   (See Plate LXIV. fig. 3.)   The sides of the
simple papillae are  more or less united together, but the tips are free
and pointed, some  more so than others.
  The length of the cylinder which  each filiform papilla describes, the
degree of acumination of the apices  of the secondary papillae, and the
extent of these which is free, vary in accordance with the position of
the papillae on the  tongue.
  The circular disposition referred to is best seen in the papillae  placed
near the tip and sides of the tongue, for in those situations the sec-
ondary papillae  are short, blunt, and nearly of equal lengths.  (See
Plate LXIV. fig. 3.)   In the centre  of the organ the simple or second-
ary papillae are much  longer, and  more slender,  so  that they  fall
together  and variously intermix with each other, and thus it  is that
the circular disposition in them is usually more or less concealed from
view.  (See  Plate LXIV. fig. 4.)
  This disposition of the secondary papillae includes  of course, as a
consequence, a corresponding arrangement of  the blood-vessels,  (a
single looped vessel proceeding to each,) and of the nerve filaments,
which are in like  manner arranged in  circles.   (See Plate  LXVI.
fig- 4.)
  The centre of each filiform papilla is hollowed  out, and is to  be
regarded as a large mucous follicle,  and  thus the comparison of these
papillae to a cylinder is rendered almost complete.  (See Plate  LXIV
fig- 3.)
  We shall presently see that the same  circular arrangement extends 
ORGANS  OF  THE  SENSES.
503
  to the filiform epithelial appendages hereafter to be described, and one
  of which corresponds to each secondary papilla.*
    The fungiform papillae  are seated principally on the tip and sides
  of the tongue, at least they are most evident in  those situations, and
  around each a space or shallow fossa, dotted with numerous  simple
  papillae, may be observed; they are  distinguished from the filiform
  papillae  by which they are surrounded, by their form, being narrow
  at the base, and dilated near  the  summit, by being clothed all over
  with simple papillae,  which are usually a good deal compressed in
  form, and by the tenuity of the epithelium, destitute of filiform append-
  ages, which covers them, and which allows of the blood in the vessels
  being seen through it.  (See Plate LXIV. fig. 5.)
    At the edges of the tongue, and at the sides behind the calyciform
  papillae, compound papillae exist, which bear some  resemblance to the
  fungiform papillae, of which they may be  described as modifications;
  they differ  from  ordinary fungiform papillae, however, in being  sessile
  and simply rounded; in the form of the simple papillae  which clothes
  them, and which usually are  not compressed, but swollen  at the
  extremity,  or pyriform.   (See Plate LXV. fig. 11.)
    The calyciform papillae  bound the true gustatory region posteriorly;
  they are seven or eight in number, and arranged in two rows, which
  meet behind in  the  foramen caecum, and enclose  a V-shaped  space,
  the concavity of which looks forward.
    They each consist of  a depression or cup,  out of which a large
  papilla,  sometimes more or less  adherent to the rim of the cup, arises,
  and the level of which it but little  exceeds; the central papilla, as well
  as the sides and margin of the cup,  are  closely set with very many
  simple papillae, which are short, obtuse, and dilated  at their extremities.
»  A calyciform papilla, perfectly freed from epithelium, and with all the
  secondary papillae visible, forms a very beautiful  object.   (See Plate
  LXVI. fig. 1.)
    The foramen ccecum usually  contains one and sometimes two large
  papillae, similarly clothed with  secondary papillae, and according  as
  it  includes one or two papillae, it is to  be regarded as a single  or
  double modified calyciform papilla.
    In front of the calyciform papillae, in some tongues, a number  of
  larcre and irregular  papillae exist, invested with  secondary  papillae

    * The form and structure  of the  filiform papillae, as above detailed, was first
  described by me in the Lancet of 3d March, 1849. 
404
THE  SOLIDS.
similar to those of the calyciform papillae, but not, like the latter, seated
in cups.
   On the edges and under surface  of the  tongue numerous mucous
follicles are observed: it is sometimes, however, difficult to distinguish
between these and simple papillae, in consequence of the  latter being
frequently perforated in the centre, and thus combining  the charac-
ters of both follicles  and papillae.  (See Plate LXV. figs. 1, 2, 3.)
   The epithelial investment of the tongue adheres very closely to the
papillae, and generally requires one or two weeks' maceration  for its
complete removal; even then, in but few instances in the  human sub-
ject, can it be removed  in  entire pieces, it in most  cases crumbling
away into its constituent cells.
   It adapts itself accurately to the papillary structure of  the tongue,
and is of sufficient thickness to conceal effectually the simple papillae,
whether these exist by themselves or constitute by their  aggregation
the compound papillae.   For  the satisfactory study of  the papillae,
therefore, it is absolutely  necessary that  the  epithelium should be
entirely removed.
   The epithelium of the  tongue presents all the characters  of the
epidermis of the skin, consisting, like it, of numerous layers  of large
and nucleated cells, those forming the outer layers being flattened and
membranous, while the  deeper-seated cells are rounded and granular.
(See Plate LXV. fig. 6.)
   The thickness of the  epithelium of the tongue in the human subject
varies very considerably in different cases, and would appear to be
much affected by disease;  it in some cases even being entirely absent.
   It is  thickest over the  simple papillae, which  are usually entirely
concealed by it; over the  fungiform  and calyciform papillae it is  very
thin and delicate, while over the filiform  papillae it is prolonged into
long filiform processes, which correspond in number and arrangement
with the secondary papillae  themselves.   (See Plate LIV. fig.  1, 2.)
   These filiform appendages vary much  in length,  being very short
upon the sides and near the tip of the tongue, but three or four times
as long near its centre (see Plate LIV. fig. 1,2);  at the very tip they
are often entirely wanting, the papillae in this situation presenting the
appearance of large open follicles with slightly spinous  rims.   (See
Plate LV. fig. 4.)
   Each filiform process is constituted of flattened epithelial  scales,
which lie in the direction of their length, and frequently contains a
canal in its centre. 
                  ORGANS OF  THE  SENSES.             505

   Tubular nerve filaments, terminating in loops, have been discovered
in the fungiform and filiform  papillae, but not  hitherto  in either the
simple or calyciform papillae, although nerve filaments, in some form
or other, doubtless exist in these also.
   The internal minute structure of the three principal forms of com-
pound papillae requires a careful  and  searching examination, with a
view to the determination of their respective functions.   From a con-
sideration of their outward  configuration, they would all appear to be
well adapted to receive gustatory impressions.  The fungiform papillae
seem to be so by their prominence and the delicacy of the epithelium
by which they are invested, the calyciform papillae also by the tenuity
of their epithelial covering and by their cupped  form, and the filiform
papillae, by reason of  the cavity which  occupies the centre  of  each,
and the regular disposition of the secondary papillae around this.
  An additional, and to my mind,  indeed, an almost conclusive reason
in favour of the subserviency of the filiform papillae to the reception of
gustatory impressions, is derived   from the  consideration that they
cover nineteen-twentieths of the  mucous membrane of the tongue;
and it is but natural to suppose that  the principal portion of this is
destined to the discharge of the function for which it has so evidently
been designed.
  The filamentary  papillae  have generally been considered to be ill
adapted to the reception of gustatory  impressions, in consequence of
the character of the epithelial processes in connexion with them; and
it has been supposed  that they are to be  regarded as  tactile rather
than gustatory organs.  This opinion  has, however, been entertained
in the absence of a full knowledge of  the real form and structure of
these papillae, as already shown.
  It has occurred to me  that these filamentary processes  act  as
absorbents of the nutrient juices, and that collectively they constitute
an absorbent surface of considerable power, conveying directly to the
papilla those fluids, and keeping them  in contact with the papillae for
a time,  thus prolonging the duration of the gustatory impression.
This idea would appear to gather confirmation from the fact that it is
in these filamentary epithelial prolongations that the variable coating
known as the fur of the tongue has its seat.
SMELL.
      Structure of the Mucous  Membrane  of the Nose.
The anatomical characters of the mucous membrane of the nose 
500
THE  SOLIDS.
differ in different regions; for  a short  distance within the anterior
nares, the mucous  membrane presents many of the characters of the
skin, it  being divisible into chorion, papillary structure, and epider-
mis; the papillae  resemble in every respect  those of the sense ol
touch, and the epidermis  consists of flattened epithelial scales analo-
gous to  those of the same structure in the skin.   This, the commence-
ment of the  nasal  mucous  membrane, may be  called  the  tactile
region of the  nose, and it is abundantly furnished with hairs, which
guard the entrances of the nares, and the roots of which are in con-
nexion with the ordinary sebaceous glands of the hair follicles.
  Higher up the mucous membrane of the nose, losing its papillae and
scaly epithelium, becomes thick and soft, and presents more completely
the ordinary appearances  of a  mucous  membrane; imbedded in its
substance are numerous  mucous follicles of large size, having but
small apertures, which are best  seen thickly studding  the surface of
the membrane after slight maceration and the removal of the epithe-
lium.  Between and around these the blood-vessels are disposed, the
veins being particularly large, and forming a very evident plexus, each
mesh of which corresponds with a follicle.  (See Plate  LXIX. fig. 2.)
  The large size and considerable numbers  of the mucous follicles
explain  the  copious secretion which proceeds from  this  portion of
the  mucous  membrane,  when  suffering from  irritation, while the
venous  plexuses sufficiently account for the disposition of this part
to hemorrhage.
  This  is by far the largest of the three nasal regions, and may be
denominated the pituitary; the epithelium which clothes it is of the
ciliated   kind, and  several of  the cavities in  connexion with the
meatuses  are  invested by a  similar epithelium, as  the frontal  and
sphenoidal  sinuses, the antrum  maxillare, and the  Eustachian tubes.
In the sinuses, however, the  mucous membrane, losing  its follicles,
becomes much reduced in thickness, and presents the  characters of a
fibrous rather than of a mucous  structure.
  Still higher up in the nose we come upon the third region, which has
been particularly defined and described by the authors of the Physi-
ological Anatomy as follows, under the name of the olfactory region:
  " The  olfactory region is situated at  the top of the  nose, imme-
diately 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 septum, and over the supe-
rior and part of the middle spongy bones of the ethmoid.  Its limits 
ORGANS OF THE SENSES.
507
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 composed of an aggregation of
superposed nucleated particles, of pretty uniform appearance through-
out; 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.  These epithelial particles, then, are
not ciliated;  and they form a thick, soft,  and pulpy stratum, resting
on  the  basement membrane.   The deepest layer often adheres after
the others are washed aw7ay.   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 macera-
tion.  In fact, glands  apparently identical with the sweat-glands exist
in this region in great numbers.  They dip down in the recesses of the
sub-mucous tissue,  among the  ramifications of the olfactory  nerves;
and their orifices are very easily seen, after  the general  brown coat
of epithelium has been detached, lying more or less in vertical rows;
the arrangement 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 that 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 par-
ticles to differ from those which they traverse.  We have sometimes
seen rods of epithelium, apparently hollow, left projecting from the base-
ment membrane, after the brown  epithelium has been washed away,
and these are perhaps portions of the excretory ducts of these glands."
  In the propriety  of the discrimination  of this  region, and in the
accuracy of much  of the description of it given  above,  the author
fully concurs.   He does not, however, hesitate  to  affirm that  no
glands at all analogous to sweat-glands exist in it; the membrane of
this region is indeed thickly studded with mucous follicles, apparently
in  no respect dissimilar to those of the pituitary region, except that
they are smaller in  size, and more  delicate in structure. 
508                      THE  SOLIDS.
   The chief characteristics of the olfactory region consist, then, in
its glandular epithelium, in the presence  of pigment cells lying be-
neath this, in its more delicate structure, in the presence of gelatinous
nerve  filaments, and in a somewhat  different  arrangement of the
blood-vessels.   (See Plate LXIX. fig.  1.)
   In the sheep this region is rendered almost black by the presence
of very many pigment cells which are  of the stellate form.
   Mr.  Quekett pointed out, some years ago, the very curious fact that
the blood-vessels of the olfactory region of the human foetus, and that
of mammalia in general, are disposed in loops, the convexity of each
of these presenting a decided dilatation.  (See Plate LXIX. fig. 12.)
   Much  interest is attached to the existence of these loops,  since they
appear to indicate the presence of true papillae in the seat of smell of
the mammalian foetus; if such be the case, however, it  is very cer-
tain that neither the papillae  nor loops exist in the olfactory region in
the adult condition of the nasal organ.
   The most rigorous search has failed  to detect  the presence in the
olfactory region of  cells, which could be decidedly pronounced to  be
nervous or ganglionic.
   The nerves  of the nose are the first pair, branches of the fifth, and
motor filaments from the seventh pair.  The first pair are,  doubtless,
the proper nerves of smell, while the fifth gives common sensibility to
the nose.
  The olfactory lobes are prolongations of the white or fibrous por-
tion of the brain, and consist, like it,  of  slender tubular nerve fila-
ments, intermixed with the  delicate transparent  cells, described  in a
previous  division of this work.
  " The olfactory filaments 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 membrane of  the olfac-
tory region.  They here branch, and sparingly reunite in a plexiform
manner,  as  they  descend.   They form a considerable  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 a former volume.   These facts we have  repeatedly ascertained, and 
                 ORGANS  OF  THE  SENSES.              509

they appear to be of great importance to the general question of the
function of the several  ultimate elements of the nervous structure,
especially when viewed in connexion 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 fibre  in  any case, pretending that it is formed by artificial
modes of preparation.  We hold it to be a  true structure, but how-
ever that may be, these nerves never exhibited 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 charac-
ter 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
cribriform plate after detachment of the bulb.  It must be remembered
that a few tubu  •  nbres 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."—Physiological
Anatomy.
                              VISION.
                Structure of the  Globe  of the  Eye.
   The structure of the several appendages of the globe of the eye: as
the eye-lids, with their lashes, and Meibomian glands, the caruncula
lacrymalis, the lachrymal gland, muscles, &c, have already been fully
described in previous sections  of this work ; we have now to  enter
upon the description of the numerous parts which compose the essen-
tial portion  of the organ of vision, the globe of the eye; each of these
may be examined in much the same order in which they would  natu-
rally present themselves to the notice of an  ordinary dissector, and
which would be somewhat as follows :   Sclerotic and cornea; cho-
roid, ciliary processes, and iris ;  retina; crystalline lens; hyaloid
membrane, &c.
                            Sclerotic.
   The sclerotic is composed, to a great extent, of white fibrous tissue,
intermixed with a small proportion of a nucleated form of elastic tissue.
   These tissues are disposed in a laminated manner, the fibres of one
layer crossing those  of another more or less  at right  angles;—an
arrangement evidently designed to render this the protecting tunic of
the eye more firm and unyielding.   The inner surface of the sclerotic 
510                      THE  SOLIDS.
 is rough, and connected with the choroid by the lamina fusca of that
 membrane, to be described hereafter.
   The nutrition of the sclerotic is provided for by small vessels which
 ramify on  its outer surface, and which are  sparingly continued into
 its substance.
   Anteriorly, the sclerotic is  strengthened  by the  tendinous expan-
 sion of the four recti muscles, known  as  the tunica albuginea, or
 white of the eye.
                             Cornea.
   The cornea, although in a state of health as clear as  crystal, yet
 possesses  a complicated and  beautiful organization, plainly demon-
 strable with the aid of the microscope.
   Notwithstanding also the definite line of demarcation by which the
 limits of the cornea and sclerotic are marked out, these two parts are
 yet inseparably united to each other;  this indissoluble union depend-
 ing upon the circumstance of the existence of a structural connexion
 between  them,  the nature  of which will shortly be rendered  evident.
   The cornea  is clearly divisible into four, and, according  to some
 observers,  even five  laminae.   These are,  reckoning from before
 backwards, conjunctival epithelium, cornea  proper, posterior elastic
 lamina, and the epithelium of the aqueous humour;  the fifth layer has
 been described in the " Physiological Anatomy"  under  the title of
 the "anterior elastic lamina."   These several layers will be separately
 noticed, and in  the order mentioned.   (See Plate  LXVII. fig. 1.)
   The conjunctival epithelium  forms a distinct membrane of appre-
 ciable thickness, and capable of separation as  such shortly  after death.
 It consists  of several layers of super-imposed cells, which partake of
 many of the characters of ordinary  epidermic scales or cells.
   Those cells which constitute the outer or more superficial layers
 are large, flat, and membranous; while those nearest to  the cornea
proper, and which appear to rest directly upon it, are baton-shaped,
 and disposed vertically to the surface of the cornea.   (See  Plate
 LXVIII. figs.  3. 5,  and Plate LXVII. fig. 1.)
   After death  this  epithelium becomes whitish and opaque, and it
then forms the film of the eye.
   The second lamina, according to  the observations  of the author, is
the cornea proper;  and it is this which constitutes the principal bulk
of that structure.
   Externally, the cornea  proper is firm and dense in texture,  but
becomes more lax and soft gradually as we approach the interior; it is 
                  ORGANS  OF  THE  SENSES.              511

this external and firmer portion which exhibits the lamellar arrange-
ment so generally described, the fibres following a less regular course
internally, and being separated by wider intervals.
  The tissue of the cornea has been recently described as a peculiar
modification of the white fibrous element of the sclerotic.  It would
appear, however, that the  fibrous tissue of which it is constituted is
of a kind totally distinct from that which enters so largely into the
composition  of the cornea  proper; a conclusion  derived from its
examination, for which we  might be prepared, simply by the consider-
ation of the very opposite physical characters  of the two parts, the
sclerotic  and  cornea, the  former being white and opaque, and the
latter clear and diaphanous.
  If we  tear  up with needles a  small portion of the sclerotic, and
examine it with the microscope, we then see  that  it is made  up, for
the  most part, of bundles  of wavy  and distinct  fibres, presenting
scarcely a nucleus, and reflecting a yellowish hue;  if now we  carry
our examination still further, and  apply acetic acid to these bundles,
they  swell  up,  the  fibres  becoming indistinct,  and finally converted
into a jelly-like substance.
  On the other hand, if we submit a portion of the cornea to the same
examination, and the same treatment by acetic acid, we shall encoun-
ter different appearances and results.  In the first place,  we shall not
perceive distinct and  separate  bundles  of fibrous tissue free  from
nuclei, but we shall merely notice  an  indistinct  fibrous character  in
the mass, with here and there elongated nuclei imperfectly seen; on
the application of acetic acid, however, the fibres become much  more
evident, and multitudes of nuclei are brought into view.   Thus, then,
it is  evident that the tissue of the cornea is something more  than  a
modification of the white fibrous element of  the sclerotic.   The nucle-
ated fibres just described are often, in the neighbourhood of the nuclei
themselves,  expanded and membraneous; and it is remarkable that they
do not lie in direct apposition with each other, but interlace in such a
manner as to  describe elongated spaces, several of which are extended
in the same line.  These spaces are oval in the cornea, and round in
that portion of the sclerotic where the two structures are in connexion
with each other.*   (See Plate LXVII. fig. 3.)

  * A subsequent examination of the cornea renders it necessary that the  views
above expressed of its  structure  should be modified to some extent.  I find that a
considerable amount of a tissue, very closely resembling the white fibrous tissue of
the sclerotic, does enter into the construction of the cornea; in sections, however, 
51-:
THE  SOLIDS.
   This arrangement  was first pointed  out by  the authors of the
" Physiological Anatomy," and is thus described  by them.   " 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, the  fibres, which in  the  sclerotic  have been  densely inter-
laced  in various directions, and mingled with elastic  fibrous tissue,
flatten out into a membraneous form, so as to 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 singular  arrangement,  hitherto
undescribed.  They lie in superpose planes, the  continuous  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.   The arrangement  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."   In addition to the  above it  may be  remarked,  that the
spaces may be seen' without injection, or any other preparation, even
in perfectly fresh eyes.
   In vertical  sections  of  the cornea, after the application of acetic
acid, the nucleated fibres  in its outer or denser  portion  are seen to
follow the curved form of the cornea itself, while in its  inner and softer
part they are variously disposed;  horizontal sections of  the  cornea,
even taken from the surface, exhibit a curved and interlaced arrange-

whether treated  or not with acetic acid, this tissue is scarcely to be traced, the nuclear
form of fibrous tissue already described, and which is so very abundant, being alone
visible, and appearing to constitute the entire of its substance. If, however, a small
piece of the inner and softer part of the  cornea be  torn up with needles, and then
examined, bundles of fibrous tissue, very  analogous to those of the white fibrous
form, will be plainly seen; these are of considerable diameter, reflect a greenish
shade, and are, in many parts, transversely straited, each filament bearing a resemblance
to a minute  Conferva; they are rendered  nearly, though not  quite, invisible by the
action of vinegar.   Considered altogether, the cornea resembles very closely, in
structure, a tendon, which also contains a very large quantity of a similar nuclear
fibrous tissue. 
ORGANS OF  THE  SENSES.
5:3
ment of the fibres;  fibres, also nucleated, pass from the surface of the
cornea deeply into its substance:  the use of these is doubtless to assist
in preserving its convexity.  (See Plate LXVII. fig. 1.)
   The posterior elastic lamina is the third layer of the cornea; it is
a perfectly transparent membrane of appreciable thickness, so that it
may be readily recognised with the unaided sight, and is  but slightly
attached to the cornea proper.
   It is usually described as structureless, and in most cases it certainly
is so; but in the human eye it frequently exhibits peculiar markings,
portrayed  in  Plate LXVII. figs. 11,  12.   These, however, would
appear to proceed from definite inequalities of the surface, rather than
from any distinct fibrous or cellular tissue; nevertheless,  the appear-
ances observed are remarkable, and worthy  of record.
   This lamina preserves its transparency even in boiling water  and
acetic acid; and a further peculiarity is, that although it may be torn
in any direction, it is so hard that it can be  bitten through only with
difficulty.   It extends to  the  margin  of  the cornea only, where it
comes into connexion  with  certain elastic fibres to  be  described
hereafter.
   The epithelium  of the aqueous humour is the fourth layer of  the
cornea:  this is of such delicacy and  tenuity as to be readily over-
looked; it consists of angular cells which form a tessellated epithelium,
and rests  upon the  posterior surface  of the elastic lamina above
described.   (See Plate LXVIII. fig. 11.)  This epithelium is doubtless
concerned in  the  secretion of the aqueous  humour, but it  does  not
appear to extend beyond the limits of the elastic lamina.
   The fifth layer, to which reference has already been made, is  the
anterior elastic lamina, which is described in the third part of "Physi-
ological Anatomy,"* as follows: " This is a transparent  homogeneous
lamina, coextensive 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 filimentous cords, which
take hold, in a very beautiful artificial manner, of the fibres and mem-
branes of those parts, and serve to brace them and hold them in their
rio-ht configuration.  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
                             33 
514
THE  SOLIDS.
lamina sustains the conjunctival epithelium which covers the cornea,
and is very probably a representative of the basement membrane of
the mucous system, as it occupies the corresponding position in regard
to the epithelium."
   The writer has made diligent and repeated search  for this lamina,
or for any structure resembling it, without success, however;  and he
has no  hesitation  in asserting his disbelief in the existence of any
membrane in the slightest degree analogous to the posterior  elastic
lamina in the situation indicated: he is not prepared, however, to deny
the presence of an exceedingly thin  layer of structureless basement
membrane, although of this  even he  has not yet  discovered  any
evidence, but conceives it possible that it may exist.  Its detection
has been attempted  in several ways;  namely, by vertical and hori-
zontal sections, and by the use of reagents, but to no purpose.
   In a representation of a vertical section of the human cornea, given
in the  "Physiological Anatomy,"  this  anterior  elastic  lamina  is
represented as being three or four times the thickness  of the posterioi
lamina,  so that there ought to be but little difficulty in its detection,
were it  present on the face of the human cornea.
   The "elastic cords" mentioned would  appear to be nothing more
than the nucleated fibres,  already described  as passing in a curved
manner from the surface of the cornea, and extending deeply into its
substance.   (See  Plate LXVII. fig. 1.)

                            Choroid.
   The next membrane met with, in the usual order of dissection, is
the choroid: this adheres intimately to the sclerotic in the neighbour-
hood of the larger trunks of the venae vorticosae; but more slightly in
the intervals between, being united to it only by the lamina fusca.
   The choroid forms a thick  membrane, externally of a chocolate-
colour, flocculent  and rough,  but internally of a bluish-black colour,
and smooth ; its substance is made up of numerous blood-vessels, and
of an immense quantity of pigment in connexion with a peculiar form
of fibrous tissue.
   The tissue of which the choroid is  composed, has been  hitherto
stated to resemble the  fibrous  tissue of the sclerotic:  this is not the
case, however, as indeed might have been inferred from the ease with
which it tears, especially in the course of the vessels, and the absence
of bundles  of  fibres  on the torn and  divided  margins:  the fibrous
element of the  choroid is of a peculiar kind, to be more fully described
hereafter, and unlike any other form existing in the human body. 
ORGANS  OF  THE  SENSES.
515
  The blood-vessels of the choroid are usually described as forming
two layers, and this they may be fairly considered as doing, although
the two lamellae are not perfectly distinct from each other, being con-
nected by numerous blood-vessels which pass between them.
  These laminae may be designated  in  general  terms  separately as
arterial and venous; the inner or arterial lamina, known as the tunica
Ruyschiana, consists of a dense and beautiful plexus of vessels, which
are so closely applied  to  each other  as  scarcely to leave  any inter-
vening spaces  or  meshes.  (See  Plate LXVII. fig. 4.)  The main
arteries which supply  this  tunic, and the veins which carry off its
blood, leave it by numerous points on its outer surface only; the veins
are particularly large and numerous, and disposed in beautiful curves,
whence they are called vence vorticosce.   (See Plate XLVIII. fig. 2.)
Before leaving the choroid, they converge to form four or five principal
trunks which enter  the  sclerotic; the arteries, fewer in number and
much smaller in size, run between the veins.
  An immense  number of granular nuclei are visible in the walls of
the venae vorticosae.
  Stellate Choroid Epithelium.—Such is the distribution of the blood-
vessels of the choroid: the next most  important element in  its consti-
tution are the pigment cells; these exist in vast  quantities,  and make
up much of its substance; they are of various forms and  sizes;  but
being furnished with two, three, or more  arms or radii, they may be
aptly termed stellate.  The nucleus in each cell is large and  particu-
larly  clear, appearing almost like a hole in its centre: this is owing to
the absence of the  colouring matter contained in each cell in that
situation.
  The existence of the  stellate form of pigment cells in the human
subject appears to have been generally overlooked: it was described
and figured  in Parts VII. and VIII. of the  Microscopic Anatomy, pub-
lished in February and March, 1847, and its arrangement in rows was
at the same time pointed out; its position in the choroid, as well as its
structure, have since been  examined with more care,  and with  the
following results:
  This pigment is situated beneath the tunica Ruyschiana,  and in the
intervals between the venae vorticosae, which it accurately  fills  up,
some of the arms of the cells,  as well  as occasionally a few of the
scattered cells, intrenching upon the veins: thus, then, its disposition
is a counterpart of that of the venae vorticosae, the dense rows of cells
exhibit the  same  curves, the same mode of branching, and viewed 
516
THE  SOLIDS.
altogether with a low object-glass in the eyes of some animals, as the
sheep, nothing can exceed the beauty and elegance of the object thus
presented to our examination.  (See Plate LXVIII. fig. 1.)
  With regard to structure, it is remarkable that each radius, or arm
of the cells is prolonged into a colourless fibre, in the course of which
several other cells may be included.   (See Plate LXVIII. fig. 13.)
  This structure is best seen in the lamina fusca, the fibres of which
are all of this nature, and  are exceedingly diaphanous, often mem-
branous, much disposed to curl up, and unaffected by distilled vinegar,
beyond undergoing a degree of contraction.  All the fibres met with
in the  choroid,  except  those entering into the constitution of  the
blood-vessels, are of  this peculiar nature.
  The inner surface of the  choroid  is so smooth  as  to convey the
impression of the existence of a distinct membrane:  of this, however,
no satisfactory evidence has yet been obtained, although portions of
membrane apparently  devoid of structure, have been seen on  the
margins of torn portions of  the choroid.   If a membrane does really
exist in this  situation, it is possible that  it is nothing more than the
vessels  of the  tunica  Ruyschiana united into  a  membrane by the
fibres above described.
  Hexagonal Choroidal Epithelium.—On the  inner surface of the
choroid a layer of cells of a regularly pentagonal, or hexagonal form,
filled with pigmentary granules, exists; these cells  are so coherent
that they form a distinct  layer, much more  evident in the  eyes of
some animals,  as the sheep, and pig,  than in those of man.  (See
Plate LXVIII. fig.  12.)
  This layer extends over that peculiar structure common to the eyes
of many quadrupeds and fishes, the tapetum lucidum; but in that
situation its component cells are of smaller size, and almost entirely
deprived of colouring matter.
  In albinoes  the colouring  matter  is deficient, not only in the cells
of tapetum lucidum, but also in those of the hexagonal and stellate
choroidal epithelium.
  The tapetum  lucidum is a layer of fibrous  tissue  implanted upon
the choroid,  possessing the  remarkable  property  of refracting  un-
equally  the rays of light which fall  upon it,  and hence its brilliancy
and metallic  lustre:  acetic  acid destroys  to  some extent  this  pecu-
liarity;  the stellate pigment is continued behind the tapetum lucidum,
which singular and  beautiful structure  acts  as  a concave reflector,
its use being to economize light, and to cause the rays to traverse the 
ORGANS  OF THE SENSES.
517
retina  a second  time,  by which means animals possessing it, are
enabled to discern  objects in a light which would be insufficient for
the purpose, in the  absence of such a provision.
  The description of the choroid now given, includes that portion of
it, only, which corresponds to the retina, and which  ceases at a line
known  as  the ora  serrata; about the eighth of an inch behind the
margin  of the cornea, in front of this line as far as the iris, the choroid
is known as the ciliary body; this is covered behind by a layer  of
non-striated  muscular fibre,  the ciliary  muscle  (see Plate LXVIII.
fig. 4), and from it the  ciliary processes descend.
   Ciliary Processes.—These processes, usually reckoned at about sixty
in number, are received into corresponding folds or plaitings of the
hyaloid membrane, called the secondary ciliary processes, and which,
taken altogether, form a circle around the crystalline lens, named after
their discoverer the Zone of Zinn: they are each composed of numer-
ous blood-vessels, (see  Plate LXVII. fig. 4), fibrous tissue, irregular
pigment cells;  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 immediately  connected with the hyaloid membrane."
   The  iris may be regarded as  an extension of the choroid, although
it does  not exhibit  all the  anatomical characters of that membrane;
it is made up  of a  considerable quantity of pigment cells, of blood-
vessels, and of fibres of unstriped muscle.    (See Plate LXVIII. fig. 9.)
   The  pigment cells constituting the posterior layer of the iris, and
called uvea, are irregular in size  and form, as are those also situated
among  the fibres of the iris;  upon the varieties  in  the colouring
matter  contained in these  last, many of  the differences observable in
the iris of different persons and animals depend.   (See Plate LXVIII.
fig- 14.)
   The  muscular fibres of the  iris in the human subject, are of the
unstriped kind, and follow two courses, a radiating and a circular; in
birds, however, the radiating fibres consist of striped muscular fibres,
and they surround  immediately the pupil;  the one set of fibres dilates
the pupil, the other contracts it.
   The  blood-vessels of the  iris  are very numerous, and are derived
chiefly  from  the two long ciliary arteries, which, on approaching the
iris, bifurcate and  form an  arch around  it, whence pass inwards a
number of branches which form loops near the  pupillary margin.
   "On  the anterior surface, near the pupil, a vascular circle marks 
518
THE  SOLIDS.
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  posterior  from the anterior  chamber, and receives from
several  parts of the circular vessel  last  mentioned, small branches,
which approach the centre, and  then return in arches, after inoscula-
ting sparingly across  the  central point."  The  membrana pupillaris
is almost absorbed at birth.
  The iris,  according to the authors of the Physiological Anatomy,
"is attached all around at the  junction of  the sclerotic and the cor-
nea, 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 sur-
face,  or that towards the laminated cornea, a net-work 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 line of the anterior  chamber, and through the aqueous
humour.  They are seen more easily in some animals than in others,
forming a regular series of pillars around the anterior chamber."
  It would appear, however, that these fibres, which  may be readily
detected in the human eye, should rather be described as proceeding
from the sclerotic,  and passing, some on the anterior  surface of the
elastic lamina, and others on  the front of the  iris, thus assisting in
uniting  these parts to that  tunic; it is very doubtful whether they
have  any structural  connexion with  the  posterior  elastic  lamina.
(See Plate LXVIII. fig. 8.)
  The ciliary nerves pierce the ciliary muscle on their  way to  the iris.

                             Retina.
  We come in  the next place to the  description  of the most interest-
ing and important of the many structures which enter into the com-
position of the globe of the eye, namely, the retina.  This membrane
may be  regarded as the expansion of the optic nerve, to which certain
other structures are superadded, and, like most of the other  mem-
branes of the eye, is divisible into distinct lamellae; these, reckoning
from  without inwards, are, tunica Jacobi,  or "stratum bacillosum,"
the granular or nuclear  layer, the  ganglionary layer, the vesicular
layer, the fibrous expansion of the optic nerve, and, lastly, the vascular
expansion of the arteria centralis retinae. 
ORGANS  OF  THE  SENSES,
49
  The tunica Jacobi is composed of a single stratum of cells of very
remarkable form.  They are minute in size, several times longer than
broad, having their long axes disposed vertically to the general surface
of the retina, and  they each consist of a body or head of a more or
less globular  or oval shape, and of a prolongation or tail, four or  five
times longer  than the head, and not more than a third of its diameter.
By their coherence these cells form a distinct membrane, the heads of
the cells all being directed  one way, namely, towards the surface of
the choroidal epithelium, and the tails disposed in an opposite direc-
tion.   Although  these cells adhere  together with sufficient firmness
to constitute a distinct membrane, it would appear that they possess
a certain power of movement upon each other, for it is only on such
a supposition that we can explain satisfactorily the fibrous appearance
which  this  membrane frequently presents  when  viewed in extenso.
 (See Plate LXVII. fig. 9.)
   The tunica  Jacobi, although  certainly not a nervous structure, is
 yet properly enumerated as one  of the layers of the retina, since it
 never adheres, on the removal of  the latter to the choroidal epithelium,
 but always  to the second  or granular layer of the retina itself: on
 account of its extreme frailty and delicacy, this membrane is only to
 be satisfactorily studied in  extremely fresh  eyes.   A few hours  after
 death the cells separate from each other, and the heads of the  cells
 become disjointed from the tails, so that in the course of a short time
 not a vestige of the membrane remains.
   Each cell of the stratum bacillosum bears not an inexact resemblance
 to a  human  spermatozoon, than which it is, however, less considerable
 in size.
   The granular layer consists  not of granules  merely, as the name
 implies but of numerous nuclei imbedded in granular matter, and each
 of which contains several dark spots which reflect the light strongly.
 This layer is of considerable thickness, and is described in the "Physi-
 ological  Anatomy" as being divided into two, of which the inner is
 much the narrower, by a pale stratum which can only be seen by very
 careful manipulation.  The nuclei of which it is  composed bear much
 resemblance to those which occur in the convolutions of the W, and
 are most probably of the same nature.   (See Plate LXVII. figs. 5 6.)
    The next is  the ganglionary layer: this appears to  have  been
  hitherto altogether overlooked; its  discovery supplies a desideratum
  in the anatomy of the eye, and clearly shows the really nervous  char-
  acter of the granular and vesicular strata of the retina, which many
  persons  have been much disposed to doubt. 
520
THE  SOLIDS.
   This layer is exceedingly thin and delicate, hardly indeed to be con-
 sidered as a distinct stratum, but yet consisting of numerous caudate
 ganglionary globules, in every respect similar, in point of structure, to
 those  which have  been described as occurring  in so many  of the
 ganglia of the human brain.
   These  caudate cells differ considerably  in  size, but  yet  are all
 referable  to one of two standards, the larger very much exceeding the
 smaller in dimensions.  (See Plate LXVII. fig. 8.)
   It is in the human retina only that  these cells have as yet been
 detected.
   The fourth or vesicular layer lies immediately on the outer  surface
 of the fibrous layer: the cells composing it are several times larger
 than the nuclei of the granular layer; a few of the most external of
 them are granular and nucleated, but the majority,  and these the larger
 cells, are clear and transparent as water, perfectly globular, and without
 appreciable nuclei.   The cells of the vesicular layer resemble very
 closely the delicate  cells which have been described in a previous part
 of this work, as found in the fibrous portions of the human brain.  (See
 Plate LXVII. fig. 7.)
  The fibrous gray layer is best seen and most  strongly  marked in
 the retina, near to the optic nerve.   If a portion of this membrane be
 cut off and spread out upon  glass, it  will be  seen to present, viewed
 with the inch  or half-inch object-glass, a number of parallel or rather
 radiating flattened bands, two of which occasionally divide or bifurcate.
  If, in the next place, these bands or bundles, having been separated
 somewhat from each other by means  of needles, and as much of the
 granular layer which so obscures  them washed  away with  a camel's-
 hair brush as possible, be then examined, they  will each be observed to
 present a  fibrous appearance; and,on  a prolonged  and careful  exami-
 nation, it will become apparent that they are made up, first, of a small
 quantity of nucleated fibrous tissue; and, secondly, and principally, of
 gray gelatinous nerve fibres.  (See Plate LXVIII. fig. 6.)
  That these gelatinous fibres constitute the principal portion of the
 fibrous layer of the retina, and that no tubular nerve  fibres exist in
 the retina itself, are points upon which not the smallest doubt can be
entertained.
  Of the reality of the transformation of the  tubular into the gelatinous
nerve filament; that is, the conversion of a tubular, unbranched,  and
unnucleated structure into a branched and nuclear tissue, great mis-
givings might be well entertained; an  attentive study of the structure 
ORGANS  OF THE SENSES.
521
of the fibrous gray layer of the retina renders it very difficult, however,
to deny the reality of such a structural transition.
   The vascular lamina is the last of the layers of the retina: it would
appear to be entirely distributed upon the inner surface of the fibrous
layer;  for, if we take a perfectly fresh eye, and spread the  retina out
with its inner surface upwards, we can readily see the larger blood-
vessels  filled with blood corpuscles, and having the fibrous  layer situ-
ated immediately behind them.  (See Plate LXVII. fig. 2.)
   The optic nerves consist of several bundles of nerve tubules: these
are very slender and brittle, and interspersed  with  delicate  globular
cells; in these last two particulars, these  nerves correspond  with the
white fibrous portions of the brain.
   The  transparent  media of the  eye are the vitreous body and the
crystalline lens with its capsule.

                          Vitreous Body.
   The  vitreous humour  is enclosed in a perfectly structureless  and
exceedingly delicate membrane, called the  hyaloid membrane:  this
does not  enclose  the whole of the vitreous  humour, but is  deficient
behind the crystalline lens, it being inserted into the side of the capsule
of that body.
   From all points of the inner surface of this membrane fibres  proceed;
these interlace with each other in such a manner as to form a cellated
structure.
   The size and structure of these cells may be readily seen with an
inch or half-inch object-glass; and the best view of them is  obtained
in the neighbourhood of the zona ciliaris.   (Plate LXVIII. fig. 7.)
   Granular nuclei of large size are seen  on  the walls of the cellated
spaces; these are most probably  concerned in the secretion of the
vitreous humour.  That  these several cellated spaces communicate
with each other, seems proved by the  fact that if the hyaloid mem-
brane be  ruptured, the whole of the vitreous  humour will gradually
escape through the aperture.
   A layer of cells of large size, and of such  extreme transparency;
as to be  discovered only with great difficulty, are described in the
"Physiological  Anatomy"  as situated on  the  hyaloid  membrane,
between it and the retina: these have not  fallen under the observation
of the writer.
   The vitreous  body, then, consists of the hyaloid membrane, cellated
fibrous  structure, the  zone of Zinn, and  of the vitreous  humour. 
5C2
THE  SOLIDS.
Through the centre of tnis body a branch of the central artery of the
retina passes in early life, destined for the posterior part of the capsule
of the lens.

                        Crystalline Lens.
  The crystalline lens is composed of capsule and body.
  The capsule is formed of a thin lamella of elastic tissue, much thicker
before  than behind, but in all essential particulars similar to the poste-
rior elastic lamina of the cornea.  The manner in which it is  attached
to the hyaloid membrane has been already pointed out; it now remains
to observe that the cellated fibres of the vitreous body are also inserted
into  its posterior part.  It is perfectly closed  on all sides, so that in
the adult condition of the eye neither vessels nor nerves pass through
it to the lens.
  The body of the lens, transparent and jelly-like as it appears to the
unaided sight, is yet full of elaborate and elegant structure.  It consists
of very many layers  of concentric  lamellae of flattened fibres, which
radiate from the centre, and  are disposed in a parallel manner with
reference  to each other; the fibres, however, have a more complicated
arrangement than this, as will be evident from what follows.
  In the Mammalia  in  general, there are visible on  the front surface
of the lens, when this has slightly lost its transparency, three radiating
grooves or  lines, the points  of which terminate at about one-third
from the  border  of  the  lens.  On  the  opposite surface of  the  lens
there exist  three similar  lines, occupying an intermediate  position.
From these  lines the fibres pass from the one surface on to the other;
thus  a  fibre which starts from the point of one  of the lines  in front,
passes  over  the border of the lens, advances midway between  two
lines on the  opposite  surface, and is inserted in the  angle of division
of those lines; another fibre starting from between two lines  in front,
is lost  on the extremity of a line situated  posteriorly : the rest  of the
fibres occupy positions intermediate to  these.  If, in the next place,
we bear in mind the  fact  that these lines, seen on the  surface  of the
lens, are but the edges of planes which pass through the centre of
the  lens, affording points of divergence,  and concourse for all the
fibres, deep as well as  superficial, we shall readily comprehend what,
without this explanation,  would have  appeared an intricate  arrange-
ment;  and we shall perceive why it is that the lens, when hardened
in spirit, or boiled in water, is prone to separate into concentric lamellae,
and into three triangular segments.   From the above arrangement it 
ORGANS OF  THE  SENSES.
523
results,  also, that all the fibres, whether  superficial or deep-seated,
decrease in width as they approach  the centre of the lens on either
surface, and also that the superficial  are longer and larger than the
deeper seated.   (See Plate  LXVII. fig. 13.)
   The edges of the fibres are most beautifully toothed and dovetailed
together,  as was first  pointed out  by Sir David  Brewster.  This
toothing is  best seen in the eye of fishes; it is also clearly manifest,
although on a smaller scale, in the fibres of the lens of most mammalia
and of man.  (See Plate LXVII. fig. 10.)
   On the surface of the lens beneath the  capsule, and occupying the
space between these, a delicate epithelium exists, very similar to that
on the posterior elastic lamina.  (See Plate LXVIII. fig. 10.)  After
death, this  space is occupied by a small  quantity of fluid, the liquor
Morgagni.
   Beneath this  epithelium,  again, other small oval  granular  cells are
encountered; from  these possibly the  fibres of  the lens  take their
origin.
   The lens is of less density externally than internally;  this, is also
 one of the results of the peculiar form and arrangement of the fibres.
   In the  adult eye,  the  lens is  entirely destitute of blood-vessels,
 although during its  development in the foetus it  is  copiously supplied
 with them.

                        THE ORGAN OF HEARING.
   Elaborate as is the organization of the ear,  it  yet presents less
 to  interest the microscopical  anatomist, than  many other  of the
 organs which enter into the composition  of the  human fabric.  The
 ear is divisible  into three portions—the  limits of  each of which are
 well defined—an external, a middle, and an  internal: the external
 portion is  an apparatus for the collection of sound;  the  middle  is
 designed  for its conveyance to the  internal, or  true and essential
 division of the organ of hearing.

                         The External Ear.
    The external ear  consists of the  expanded part  or auricle, and the
 external meatus.
    The Auricle.—The auricle presents several  eminences and depres-
 sions manv of  which have received distinct names; it is made up  of
 integument, cartilages, and fat; the integument  is  thin and delicate
 and is furnished with but few sebaceous glands;  the cartilages are  of 
524
THE  SOLIDS.
the fibrous kind, and  are  three in number—the larger forming the
pinna, being separated from that of the  tragus  and anti-tragus, by
grooves filled up with  fibrous tissue; lastly, the fat is situated chiefly
in the lobe of the ear.  Ligamentous bands  bind the auricle to the
bone, while  its  movements are effected,  in  part, by muscular fibres
which pass between the prominent parts of its  constituent cartilages,
but mainly, by three small muscles of the striped  variety, and each
of which, has received a distinct name.
   The  Auditory Canal.—The auditory canal consists of two parts—
a cartilaginous and an osseous;  the first is formed by the prolongation
inwards  of the cartilages  of the auricle;  these form a tube, deficient
at the upper and back part, where the place of cartilage is supplied
by a fibrous  membrane; this tube is inserted  into the auditory pro-
cess of the temporal bone;  the osseous part of this  canal  is formed
by the  auditory process already alluded to; this  process in the adult
is nearly three-quarters of an inch long,  and to  its outer margin the
tympanum is attached, the bone being grooved for its reception: in
the foetus, the auditory process is a detached  ring of bone, into which,
however, the tympanum is inserted.
   The orifice of the meatus is defended by hairs, the bases of which
are in  connexion with sebaceous glands; still further inwards, but
limited to the cartilaginous part of the passage, the ceruminous glands
are encountered:  these have already been described.
   According to some  observers, muscular fibres  exist in the external
meatus, which becomes shortened by their contraction.

                        The Middle Ear.
   The middle ear consists of the tympanum, tympanic cavity, and
the ossicles with their muscles.
   The tympanum,  or tympanic  membrane, is  divisible  into  three
laminae—an external or cuticular, a middle or  fibrous, and an internal
or ciliated;  the external is a continuation of  the cuticle which lines
the external meatus, and  may be  separated as a distinct membrane:
the fibrous tissue, of which  the internal  lamina  of the tympanum is
composed, is strong and dense, and is arranged in a radiated manner;
into this the handle of the malleus is inserted: the blood-vessels which
supply the tympanum pass along the handle of  the above-named
bone, and follow the same radiated course as  the  fibres themselves;
the inner and third lamina is composed of cells of ciliated epithelium,
similar to those lining the tympanic cavity. 
ORGANS OF  THE  SENSES.
525
    The tympanic cavity is lined by a fibrous  membrane, divisible
 into two layers;  the  fibres  entering into the composition  of one  of
 these, follow a longitudinal  course, while those of the other layer are
 circularly disposed;  these fibres are, for  the most part, nucleated, and
 would appear to  be  of the elastic kind: in the longitudinal layer, the
 fibres are disposed in bundles,  and are possibly contractile: on  the
 surface of this membrane, and lining immediately the tympanic cavity,
 is a layer of ciliated epithelium,  continuous on the one hand with that
 of the tympanic  membrane; and on the other, with that clothing the
 interior surface of the Eustachian tube.
   Posteriorly, the tympanic cavity exhibits the openings of the mastoid
 cells; anteriorly, the  orifice of  the Eustachian tube may be noticed,
 while the internal wall of the tympanum presents two orifices which
 communicate with the internal ear: these are the fenestra ovalis, leading
 into the vestibule; and the fenestra rotunda, opening into the cochlea.
   The whole length of the tympanic  cavity, is traversed by a chain
 of three bones, united  to each  other by muscles of the striped kind;
 one extremity of this  chain  is attached,  as already noticed, to  the
 tympanum, while the other, formed by  the base  of the stapes, is in
 connexion with the fenestra ovalis.
    In  the tympanic  cavity  of the  ear of the sheep cells, containing
 pigment,  may very  generally  be observed;  among these, I have
 noticed the occurrence of numerous delicate transparent cells, similar
 to those of  the white substance  of the brain and spinal marrow.

                 The Internal  Ear or  Labyrinth.
   The internal ear,  which is the essential  portion of  the organ of
 hearing, consists of  three parts: the  vestibule,  the  semi-circular
 canals, and the cochlea; these  are cavities imbedded in the petrous
 bone, communicating with the tympanic cavity on the one side, by the
 fenestras ovalis and rotunda; and on the  other, with the internal audit-
 ory canal.   The  dense bone immediately surrounding these cavities is
 termed the osseous labyrinth, in  contra-distinction to the membranous
 labyrinth contained within  them.   The description of the form, &c,
 of  the osseous labyrinth belongs rather to descriptive than to general
 or microscopic anatomy, and therefore will not here be entered upon.
   The osseous labyrinth contains  a fluid which has been called the
perilymph,  from its  surrounding,  though in the vestibule and  semi-
 circular canals only, a hollow membranous apparatus—the membran-
 ous labyrinth, which  itself contains a fluid, the endolymph. 
526
THE  SOLIDS.
  The following account of the structure of the spiral lamina ; of the
cochlea; the cochlear  muscle; the cochlear nerves; the membran-
ous labyrinth; the vestibular and auditory nerves, is copied from the
" Physiological Anatomy:"

  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 wall, and is perforated,  as already
described, 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 any thing  else, but having a peculiar arrange-
ment, quite  unlike any other with  which we are acquainted.  Being
uncertain  respecting the office of this structure,  we shall term  it the
denticulate lamina (Plate LXIX.  fig. 3), from a beautiful series of
teeth, forming its  outer margin, which project far  into the vestibular
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 appears to rest on the osseous
zone;  seen from above, after the osseous zone has been rendered more
transparent  by weak hydro-chloric acid, rows of clear lines may be
traced from  the teeth  at the  convex edge, towards the opposite 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 are  more or less sinuous
and irregularly branched. 
ORGANS OF  THE SENS-ES.
527
   " The denticulate lamina, thus placed on the vestibular surface of
the osseous zone, is  above, and  at some  distance from the plexus of
the cochlear nerves, which lies near its tympanic surface.  The vesti-
bular surface of the osseous zone, including the denticulate lamina, is
convex, rising from the free series of teeth towards the modiolus.
   " In the groove already mentioned, there is a  series  of elongated
bodies,  not unlike  columnar epithelium, in which  the nuclei are
very faint.
   "These bodies are  thick and tubical 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 mem-
brane.  We can assign them no use.
   "Continuous with the thin margin of the osseous zone is the mem-
branous zone.  (Plate LXIX. fig. 4.)  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 homogeneous, 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 the inner clear belt, and on its tympanic
surface, runs a single, sometimes branched vessel,  which would be
most correctly called a capacious capillary,  as it resembles the capil-
laries 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."
   Of the  Cochlearis Muscle.—■" At  its outer or  convex margin, the
membranous zone is connected to the outer wall by a semi-transpa-
rent  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 cochlea presents a groove, 
:>:s
THE  SOLIDS.
 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, 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 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 margin 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  laminae.
 Thus the cochlear muscle is broad at its origin  from the groove of
 bone, and slopes above and below to the  thin margin in which it  ter-
 minates,  so  that its section is triangular, and it presents three surfaces,
 one towards the groove of bone,  and one to each of the scalae.   The
 surface 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.  (Plate LXIX.
fig. 5.)   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 mus-
 cular  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  capillaries of the ciliary muscle  are derived from  vessels
 meandering over  the walls of the scala before entering it, and  those
 from above  and below do  not anastomose across  the line of attach-
 ment of the membranous zone; thus indicating that the continuation
 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 manv
 animals containing scattered pigment" 
                  ORGANS  OF  THE  SENSES.              52Q

   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 succession into the canals hollowed in the osseous
 zone of the spiral lamina, close  to  its tympanic  surface.  In this
 distribution, the  nervous bundles sub-divide and reunite  again and
 again, forming a plexus with  elongated meshes, the general radiating
 arrangement of which may be readily seen  through the substance of
 the  bone when it  has been  steeped in  diluted hydro-chloric acid.
 (Plate LXIX. fig. 6.)  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 mem-
 branous zone, these tubules arrange themselves more or less evidently
 into small sets, which advance  a  short  distance, and  then terminate
 much on the same level.   These terminal sets of tubules  are  cone-
 shaped, coming to  a kind  of point ere  they cease.   The  white sub-
 stance  of Schwann exists  in them throughout, but is thrown into
 varicosities, and broken  with extreme  facility, and they are  inter-
 spersed with nuclei, so that it is very difficult to discover the precise
 disposition of the individual tubules.  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 nucleated fibres ending in  loops;  but
 this  is a peculiar structure.
   "The capillaries of the  osseous zone are most abundant on the
 tympanic scala, in connexion with the nerves now mentioned, and form
 loops near the margin, with here and there an inosculation with the
 large marginal capillary already mentioned."
   Of the Membranous Labyrinth.—" This has the  same  general
 shape as the bony cavities in which it lies, but is considerably smaller,
 so that  the perilymph  intervenes in some quantity, except where the
 nerves passing to it confine it in close contact with the osseous wall.
 Its vestibular  portion  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
communicating with the utriculus.
                             34 
530
THE  SOLIDS.
  " The  membranous semi-circular 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 membranous ones open  at  both  ends
into the utrijculus, there  being, however, a constricted neck between
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 vesti-
bule 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 at those
parts.  The branches to the ampulla of the superior vertical and the
horizontal semi-circular  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 35, 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 than
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 opposed, and
but slightly adherent; the nuclei are often saucer-shaped, and when
seen edgeways have the  uncommon appearance of a crescent.  They
easily become detached, and  fall into the endolymph.  Minute arteries
and veins, derived chiefly from a branch of the basillar accompanying
the auditory nerve, enter the vestibule from the internal meatus, and
ramify on the exterior of the  membranous labyrinth, apparently bathed
in the perilymph.  A beautiful net-work of capillaries, forcibly remind-
ing 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 
                   ORGANS  OF THE  SENSES.              531

 other situations.  There is an abundant net-work of capillaries in the
 interior, of  the utriculus and sacculus, about the terminal distribution
 of the  nerves, which evinces the activity of the functions of these
 parts.
   " The membranous labyrinth, or its simple representative, the audit-
 ory sac, contains in all animals, either solid or pulverulent calcareous
 matter in connexion 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  semi-circular canals.  In the
 vestibular sacs it appears to be entangled in  a  mesh of very delicate
 branched fibrous tissue, in connexion with the wall, and it is  most
 probably held in place by cells  within which, according to Krieger,*
 its particles are deposited.   It has a regular  arrangement, and is not
 free  to change its place in the endolymph.  Otolithes  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
 terminate.  In the utricule 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
 connexion 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-cylinders 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, without losing their white sub-
stance.   In the frog this has been evident enough.
  " The nervous twigs belonging to the semi-circular canals do not
                      * De Ololilhis.  Berol, 1840. 
532
THE  SOLID?.
seem to advance beyond the ampullae, in which they have a remark-
able distribution—entering 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 termina-
tion can be best  seen in the osseous fishes, and has been described
by Wagner to be loop-like.   We believe we have seen 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."
  Of the Auditory Nerves.—"At  the  bottom of the meatus, the
portio  mollis divides  into two branches,  one  to the  vestibule and
semi-circular canals, the other to the cochlea.
  " The vestibular nerve divides into three branches;—the largest is
uppermost, and penetrates the depression which  is immediately behind
the orifice of the  aqueduct of Fallopius  to be distributed  to the
utriculus, and to the ampullae  of the superior vertical and horizontal
semi-circular canals.   The second  branch of  the vestibular  nerve
is distributed to the sacculus; and  the third to the posterior vertical
semi-circular canal.
  "The  cochlear nerve  penetrates the funnel-shaped  depression  at
the bottom of the auditory canal, and proceeds from it through the
numerous 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
described.
  " The labyrinth receives nerves from no other source but 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." 
ORGANS  OF  THE  SENSES.
533
                                 EYE.
  [Little need be said with regard to the methods of studying the anatomy
of the eye, farther than the directions already given.  The sclerotic and
successive lamina of the cornea, can only be well seen on careful dissection;
for  this purpose, fresh eyes are necessary, and the dissection should be
made under water.  The arrangement  and  size of the tubes of the  cornea,
may be seen  by driving  mercury or  air into  a  slight puncture.   A thin
section, dried and opened  with needles  under water, will also exhibit them.
Acetic acid is a valuable  assistant in minute dissection of these structures.
  The vessels of the  choroid membrane and  of the ciliary processes are
best observed after injection; a fcetal subject will here offer the best chance
of success when the injection is made  by the umbilical vein.  To examine
the  tunica Jacobi, Quain and Sharpey state that it may be  raised from the
surface of the retina by  injecting air or introducing mercury beneath  it,
when under water.  The retina should  be examined in the freshest possible
state.  Wagner  recommends white rabbits as subjects;  the pigmentary
matter of the choroid coat offering no obstacle to accurate observation.  Dr.
Hannover, of Copenhagen, states that the vitreous body is best studied in the
eye of the horse, after having been hardened in chromic acid.  In man, he
found the  vitreous humour to be arranged, as it were, in arched slices  or
wedges, the arches turned outwards, and the angles converging towards the
axis of the eye like the wedges of an orange.  If the sections are horizon-
tal,  they resemble the slices of an orange cut from pole to pole: if  perpen-
dicular, they resemble one  cut  at right angles to the preceding direction.
This  arrangement is  more  clearly seen in infants than  in adults.  Dr.
Hannover  was  unable to decide whether  the membrane  between  these
segments  is  single  and  common to  both,  or whether each  segment  is
furnished  with a membrane of its own.*

  Plate LXXVIII., fig.  1,  The terminal vessels  in the cornea of the eye
                             of the pig.
     «       »      fig.  2,  Cornea of viper, showing its vascularity.
     «       «      fig.  3,  Choroid coat of foetal eye.
     tt       «      fig.  4,  Ciliary processes of the eye of  an adult.]
* Dublin Quarterly Journal, May, 1848. 
 
APPENDIX,
                      Pituitary  Gland.
   The pituitary body, inasmuch as it presents the usual characteristics
 of glandular structures, would be more accurately denominated the
 pituitary gland, a term which conveys its real nature.
   The pituitary gland, in the absence  of an excretory duct—unless
 indeed the infundibular process attached to it is to be considered as
 such—would appear to be allied to the vascular glands, while in some
 other respects it resembles the ganglia of the sympathetic, which also
 are glandular organs.                     '
   It consists of two lobes, an anterior  and a posterior, which differ
 from each other in size, colour, and consistence; the former is  con-
 siderably the larger of the two, is of a yellowish gray colour, and of
 much  firmness and  density;  while  the  latter is gray and  soft, and
 scarcely differs in consistence from the gray matter of the cerebrum.
   As the two lobes differ  in colour and consistence, so are they some-
 what different in structure also; the anterior or denser lobe is made
 up of  numerous  granular cells, very various in form and  size, and
 many of which are in some  cases  of very considerable  dimensions;
 these cells lie in meshes of fibrous tissue, which separate  and parcel
 them out, each of the larger cells occupying  separately an entire
 mesh.   (Plate  LXIX. fig. 8.)  The posterior lobe differs  from the
 anterior in the  smaller size of its cells, and the less amount of fibrous
 tissue which enters into its composition.
   The pituitary gland is connected with the brain by means of the
infundibulum, the small extremity of which is attached to the superior
concave surface of the gland, and is united principally to the posterior
lobe, which  it  also  resembles in structure, containing  very many
granular cells in its parietes.
   This gland resembles a ganglion of the sympathetic in the large
size  of its cells, and  in the arrangement of its fibrous constituent; 
536
APPENDIX.
but differs from it in the irregular form of the cells, and in the absence,
so far as has been yet ascertained, of tubular nerve fibres.

                          Pineal Gland.
   Notwithstanding the interest which exists in the  minds of most
persons in reference  to this body, and which  has arisen  in conse-
quence of the strange physiological speculations of which it has been
the subject,  its structure yet does not appear to have been examined
with that amount of care which has now been bestowed upon  most
of the other organs which  enter into the constitution of the human
fabric;  not,  however, that its organization is uninteresting or difficult
to be understood;  for this, while it is complex and singular, yet admits
of easy determination.
   The  chief bulk of the pineal gland, is made up  of  innumerable
minute  granular cells, which, when carefully examined in a  perfectly
fresh subject, are seen to be of  the caudate form, the rays of the cells
being exceedingly  delicate  and slender,  and  apt, therefore,  to  be
entirely overlooked.
   Imbedded in this cellular matrix, and, for the most part, collected in
the centre of the organ, there may be noticed numerous  particles  of
stony hardness of various sizes, and mostly of  a rounded form, and
the larger of which are  plainly visible to the  naked eye.  Of these
bodies, I have never encountered  any satisfactory description;  thev
are not, as generally considered, mere inorganic and earthy  particles,
but structures of a definite and complex organization, constituting an
essential element  in the  composition of the  pineal  gland.  When
viewed  with the half or quarter-inch  object-glass, the larger of these
bear much  resemblance to masses  of fat, each  being composed  of
numerous distinct and  aggregated lesser  pieces, or particles which
reflect light  strongly, and it is in this  circumstance, as well as in their
large size, that the resemblance  borne by these  bodies to masses  of
fat consists.   (Plate LXIX. fig. 7.)
   In the natural condition,  these bodies are hard and brittle;  after,
however, the application of dilute nitric acid, they become soft, the
earthy matter being dissolved away,  and nothing remaining  but their
animal constituent; this, if the acid employed has not been too strong
still retains,  to a great extent, the size, form, and appearance of these
bodies, previous to its action, and will now readily be seen to exhibit
a cellular structure, a cell corresponding to each of the bright con-
stituent pieces above described.  If, however, the  acid employed  be 
APPENDIX.
537
somewhat stronger, these bodies undergo a singular change in form
and appearance, the cellated  spaces  become almost lost to view, and
these compound structures assume the characters of large and spher-
ical cells exhibiting numerous concentric lamellae.  The earthy matter,
then,  is contained  in these cells or cellated spaces; the acid  dissolves
this away, and the entire body becomes so soft, as to admit readily of
being torn to  pieces with needles; in this state, its structure may be
easily determined,  and is seen to consist of membranous elastic tissue.
  These bodies originate  in exceedingly small and bright circular
discs, which, when seen with the quarter-inch  object-glass, are less in
size than the head of  a pin;  in these appear first, one, and, afterwards,
other divisions, indicating the compound and cellular character, which
they ultimately more  completely exhibit.
  The earthy  matter entering into their composition consists of phos-
phate of lime,  a small portion of phosphate of magnesia, and a trace
of carbonate  of lime.
  Minute sandy particles have been  described connected with the
choroid plexuses, and that  portion of the velum inter-positum which
invests the pineal  gland; whether these bodies are of the same nature
as those occurring in the gland  itself, I am unable to say, not having
myself detected them in either of the above situations.
  These bodies, which are almost peculiar to the human subject, are
stated not  to  occur  in the pineal gland, until  after the age  of seven
years.
  In addition  to the above described essential  elements of every fully
formed human pineal gland, I encountered on  one occasion two large
round cells or  bodies, containing dark nuclei of a compound charac-
ter;  these appeared  to be some modification of the sabulous bodies
already described.
  The pineal  gland  is  copiously supplied with blood-vessels, is trav-
ersed sparingly with  delicate nerve tubules,  and  contains a small
quantity of an exceedingly slender form of fibrous tissue, which
possibly proceeds from the caudate cells already noticed.

                         The Pia  Mater.
  The pia mater, the vascular  membrane of the brain, is composed
of fibrous tissue and blood-vessels;  over the surface of the brain and
its convolutions, this membrane  is delicate and highly vascular, while
over  the spinal marrow, it  is thicker and less freely supplied with
vessels. 
53 S
APPENDIX.
  In the ventricles, this membrane forms the choroid plexuses and
velum  inter-positum; in the former, it is  thrown up  into numerous
processes  or villi, each of which  is furnished  with  a large looped
blood-vessel, and its outer surface, like the villi of the  intestines, is
clad with a  very evident epithelium.  (Plate LXIX. fig.  9.)
  This  epithelium, according to many observers, is  of the ciliated
kind;  the cells  composing it, are polygonal somewhat flattened, and,
as Henle* long  since noticed, furnished  at their angles with spinous
processes; these are only to be seen in perfectly fresh  subjects, and it
is probable that in some  cases, they have been mistaken for cilia;  not,
however, since  the fact  has been attested by several witnesses, that I
would deny the existence of  ciliary processes on the  cells  of this
epithelium.

                    The Pacchionian Glands.
  The Pacchionian Glands  are found among the  vessels of the pia
mater on the edges of the cerebral hemispheres, and are  described as
granulations composed of an albuminous  material;  they push before
them  the  arachnoid membrane, project  into  the  longitudinal  sinus,
and, in cases, even occasion absorption  of the  parietal  bones, lying
imbedded in little pits or recesses.   They are  stated not to occur in
early life, and they are frequently absent in the adult.
  I have encountered on the surface of different portions of the pia
mater, usually near to the sulci  of  the convolutions, little  masses or
bodies of two forms, apparently very distinct;  in the first, these were
opaque  and whitish, and consisted of a  capsule  of  fibrous tissue,
enclosing  a number of minute granular cells; in  the  second,  the
masses appeared to  lie  free among the vessels  of the pia mater,  and
each broke  up readily on being touched into  several other smaller
granulations of the same character:  these, examined with the micro-
scope, were seen to be made  up of numerous dark-looking bodies,
very irregular in form and size, and which  appeared to be of a fatty
nature.

      Observations  on  the Development of the Fat Vesicle.f
  "When the difficulty of determining the exact structure of the fat
vesicle is  considered—a difficulty arising  from the extreme tenuity
of its cell-wall,  and the opacity of its contents—it is scarcely surpris-
  * Anat. Gen. t. L p. 233.
  fBy the Author.—Lancet, January 20th, 1849. 
APPENDIX.
539
mg that we  should  yet be without any  consistent account  of  the
modes of development  and growth of the fat vesicle.
  "This hiatus in the structural history of that peculiar animal tissue,
fat, the present brief remarks are intended in some measure to fill up.
  " When the little fatty masses which are met with so abundantly in
the neck, in the neighbourhood of the thyroid and  thymus glands, as
also in some  other  situations in a foetus nearly or quite  arrived at
maturity, are examined, it will be observed, by the  use of a lens only,
that these masses are  each composed of a number of  distinct  and
opaque bodies of various sizes, presenting a smooth outline, having a
more or less rounded or oval form, and held loosely together by fibro-
cellular  tissue, the  extension  of which  forms the envelope which
invests each of these bodies.  It will also be further noticed that each
mass of fat is supplied with one or more blood-vessels, and that these
break up into numerous lesser branches, one  of which goes to each
of the previously-described bodies, being conveyed to it by the con-
necting fibrous tissue;  and that, having reached this body, it undergoes
a further sub-division, the  branches extending over its entire surface.
  "In continuation  of these  observations,  it  will be remarked,  that
each of these peculiar bodies bears a close resemblance in  its general
aspect, to a lobe of a sebaceous gland—a resemblance, which, as will
be seen almost immediately, extends even to its internal structure.
  "If a number  of these bodies  be torn  into fragments with  fine
needles, and be examined with a half or quarter-inch object-glass, it
will be observed  that  the cavities of some of them  are  filled  with
cells  of a large size, and which  again are  occupied with numerous
globules of various  dimensions,  presenting many  of the  characters
of  oil globules, but being of greater consistence.  (Plate  LXIX.
fig.  10.)  These cells, save by their somewhat, larger size, it is impos-
sible  to distinguish  from the perfect  cells of sebaceous  glands; so
complete indeed  is this  resemblance, that at first sight I did not
hesitate to regard them as belonging to some sebaceous gland, and
which  I was  much astonished to  encounter in  such  a situation.
Others of these  peculiar  bodies, which  may be termed  'fat cysts,'
contain a mixture, in variable proportions, of these compound cells and
of free globules, which, however, it is to be observed, are generally of
larger size than those contained within the compound or parent cells.
Lastly, others of these bodies enclose no compound cells,  but are filled
with globules of still larger size.  (Plate LXIX. fig 11.)
  "Now, the  curious part of this history is, that it is these globules 
540
APPENDIX.
which  go on increasing in size, and, bursting the envelopes which
contain them, ultimately become what are ordinarily regarded as the
true fat vesicles.
  "In  the article  Fat,  in an early number of the  'Microscopic
Anatomy,' I noticed the fact, that the fat vesicles of children are not
so large as those of the adult;  this fact it then appeared to me had an
evident relation to  the growth of the fat vesicle, and it suggested the
idea that the fat corpuscle was of very slow growth, not attaining its
full dimensions until near the,adult age;  and that it was permanent in
its character, enduring throughout life.   This idea gathers increased
weight, and,  indeed its  correctness  is rendered almost  certain,  by
the additional observations just cited on the development  and growth
of the fat vesicle.
  "It would appear, therefore, taking into consideration all the fore-
going particulars, that the principal development of fat vesicles takes
place in the advanced foetus, and in  the early  years of life (for I now
remember having  met with  'fat  cysts' in the  great  omentum  of
children of five and six  years  of age, although at the time of observ-
ing them I did not know their nature  and meaning), that what are
usually regarded as the  true fat vesicles or cells, are first contained in
parent cells,  and lastly, that  they are slow  in  their  growth, and
persistent throughout life.
  "I infer also further, from the foregoing facts,  that the ordinary fat
vesicles  are incapable of acting  as parent cells and of reproducing
their like; an inference which might be fairly entertained on other
grounds, viz:  the  difficulty,  not  to  say  impossibility, of detecting
nuclei in them, and the absence of those granules among their contents
which  are so characteristic of true cells, and which there is so much
reason to believe are the real germs of the future generations of cells.
  " From comparative observations it would appear that the develop-
ment and growth of fat  proceed at different rates in different localities
of the  same body, it being more  advanced in one situation than in
another; and also in the same parts in different children  of the same
age; so that an exactly similar condition of things to that which I have
described as  existing in  the masses  of fat which occur in the region
of the neck in the mature foetus, must not in all cases be looked for.
  " The structural resemblance which I have shown to exist between
fat  cells in an early condition of their development, and  the cells of
sebaceous glands is most interesting, the latter appearing to be,  in fact,
simply fat in  a rudimentary and imperfect state of its development." 
APPENDIX.
541
          On the  Structure and Formation of the  Nails.

   Since the  publication of the article  contained in  this work on the
structure of  nail, some  further  observations  by Mr. Rainey, on the
same subject, have appeared; the more  important  of these  are con-
tained  in the following extracts :*

  "The object of this paper is to show that the nails consist of at least two distinct
structures; one proper to them, the horny structure, and the other the cuticular one;
and also, that their matrix possesses one set of vessels expressly  for the secretion
of the horny part of the nail, and another set for the formation of the cuticular por-
tion; and that besides these, there are other vessels, differing in their characters and
arrangement from the  preceding, and  probably intended to furnish a material, inter-
mediate in some of its properties between horn and cuticle, and destined to blend
these together, and  thus to preserve their union during the growth and protrusion
of the nails.  However far this idea  may be  correct, -the  anatomical fact of there
being these three different arrangements of vessels is indisputable."

                         Structure  of the Nails.
  "If a  thin vertical section be made lengthways through a finger-nail from its poste-
rior to its anterior or free margin, the  external or dorsal  surface of that portion of it
which was lodged in the  groove between the matrix and the semi-lunar fold of skin
projecting from the dorsum of the finger, is seen covered by a thin layer of cuticle,
which extends backwards as far as its posterior border, which is generally jagged and
uneven, and forwards upon its dorsum.  This portion  of cuticle is immediately con-
tinuous with that overhanging the root of the nail, and although it is not inseparably
blended with its horny substance, yet it is sufficiently adherent to be carried forward
with it during  its growth, and to remain intimately attached to its dorsal surface until
it is worn off by friction or some other mechanical cause.  The palmar surface, near
to its free border, is also seen covered by cuticle, which in like manner divides into
two parts, the  one becoming continuous with the cuticle  covering the end  of the
finger; the other passing  backwards along the palmar surface of the nail as far as
the lunula, where  it imperceptibly terminates.  This portion of cuticle gradually
diminishes in thickness as it extends backwards, and  is more intimately connected
with the horny part of the nail than was the cuticle on its dorsal surface.   Between
these layers of cuticle the proper or horny matter of the nail can be distinguished,
presenting fine, nearly parallel, and generally  semi-elliptical lines, with  their con-
cavity looking in different directions in  different parts of the same section, and also a
multitude of darkish-looking corpuscles, when viewed by transmitted light, of various
forms and sizes.  These compose the substance of the horn of the nail, and the lines
are the cut edges of the laminae of which it is made up.  The horny part of the nail
does not increase in thickness after it has extended beyond  the lunula, the apparent

   * " On the Structure and Formation of the Nails  of the. Fingers and Toes."  By G.
Eainey, Esq., M. R. C.L.—Transactions of the Microscopical Society, March, 1849. 
542
APPENDIX.
increase of the nail anterior to this point being derived from the cuticle formed upon
the anterior part of the matrix."

                         The Matrix  of the Nail.
  "A mere inspection, even  in the living subject, of the parts  situated beneath the
nail, is, in consequence  of its transparency, sufficient to give a general idea of the
relative vascularity of the various parts of its matrix  The upper part of the matrix
is seen to present a pale, semi-lunar space, called the lunula.  The greater part of the
lunula is concealed by the semi-lunar fold of integument which  projects over it; but
extending a little below this fold, the lower portion of the lunula is visible, presenting
a curved border, with its convexity looking downwards.  Immediately  below the
lunula, and circumscribing its inferior limit, the matrix  has a reddish  colour, which
gradually becomes fainter towards the free margin  of  the nail, but which deepens
considerably where the nail becomes detached from the integument.
  "When the matrix is fully injected and the nail  removed, the part corresponding
to the lunula presents several rows of convoluted capillaries:  the  individual convo-
lutions have  different degrees of complexity, from  a simple loop (a little twisted
round itself,) to  a complex tuft of vessels.  These rows have their direction from
above to below; they are all slightly curved, being concave towards the median line
of each nail, and the  most external ones are nearly parallel with its lateral margins.
These, being the vessels which secrete the horny part of the nail, may be called the
horn-vessels.   Superiorly these vessels are separated from the rich plexus on the fold
of integument which  overhangs the nail, by a fibrous and almost non-vascular groove,
in which  the  free border of the  nail was lodged, and where the cuticle covering its
root terminates.  A  few vessels, however,  pass across  this  groove from the horn-
vessels to the plexus just mentioned.  Interiorly the horn-vessels communicate with
quite a different arrangement of capillaries,  which run in a more straight course, and
are much more crowded together than the horn-vessels.  These vessels run nearly
parallel  with one another, in a  direction  from behind forwards, and being very
near together, render this the most vascular part of the  matrix, and produce  that
redness  immediately below the  lunula  upon which the form  and  degree of dis-
tinctness of its lower border is dependent.   Just below these vessels the surface of
the matrix begins to be raised into numerous plications or folds, passing directly for-
wards, and increasing in depth as they approach the free extremity of the nail, where
they become  continuous with the raised lines observable on the ends of the fingers.
These plica? consist each of a fold of basement membrane, enclosing a series of loops
of vessels.   At first  these loops  are small and simple, but they become larger and
more complex, as they advance towards the end of the finger, where they  are  con-
tinued from the ridges of the matrix of the nail into those of the skin ofthe finger,
in which they are generally very complex.   When the nails are in situ, these ridges
are received into corresponding grooves in their inferior surface.   Near the part of the
matrix where the plicae commence, several distinct circular or oval  openings are
sometimes seen passing for some depth  beyond the surface, and appearing like fol-
licles or  lacunae.  These  are frequently closed by the opposition of the  adjacent
plicae, and thus their presence is rendered doubtful, but they can be seen very dis-
tinctly either when some of the material which they contain has been recently removed
or still remains within them in the form of  whitish, globular masses.  The situation 
APPENDIX.
543
of these lacunae, where the openings themselves are not apparent, can be  dis-
tinguished by the plexus of capillaries in their vicinity, in the areola? of which  their
openings are situated."

     On the  Ganglionic Character of the Arachnoid Membrane.

   The following extracts contain the more important portions of Mr.
Rainey's  observations "on the Ganglionic  Character of the Arach-
noid Membrane  of the* Brain and Spinal Marrow:" *

  " The first idea which suggested to me the resemblance of the arachnoid to the
sympathetic, was from the examination of a piece of the former taken from the infe-
rior and lateral part of the medulla  oblongata, when I  observed, at the meeting of
two of the chords situated between the arachnoid and pia mater (called by Magendie
' Tissu Cellulo-vasculaire sub-Arachnoid'), a triangular body of the form and general
appearance of the ganglion, very similar to such as I had seen in small  animals.
  " This resemblance appeared more  striking on observing a branch going from the
chord connected with this body to the arachnoid membrane, along which it ran for a
considerable distance, dividing  and sub-dividing in its  course, in the  manner of a
nerve; the successive sub-divisions becoming more and more minute, and at the same
time interlacing and enclosing small areolae filled with  corpuscular matter.   These
corpuscles were so  blended with  the ultimate  filaments of this chord as to render
indistinct their exact mode of termination.
  " Such was  the connexion of one  extremity  of one  of  these chords.   The next
point to be determined was the structure to which the other extremity of the same
chord had been attached.  As, in this case, it had been separated from its connexion,
this could only be ascertained by examining similar chords in other portions of mem-
brane.   This examination being made, I found  that the end in  question terminated
either on an artery or on a cerebro-spinal nerve.   In the  former case, a chord, as soon
as it comes in contact with an artery, divides into branches which ramify upon it, and
run along its  external coat, just  as, to all appearance, the branches of the solar
plexus do on the small arteries supplying the viscera in the abdomen.  If the cerebral
artery be rather large, and situated between the arachnoid and pia mater, some of the
branches going from a chord form upon it a plexus, and others proceed onwards to
the vessels of the pia mater.
  " In some instances a chord passes from an artery to the arachnoid without dividing
in its course,  as just described; but more frequently, on approaching  the latter,
it sends  off three or four large branches, which pass to different parts of the. mem-
brane,  and ramify in it, as before explained;  however,  sometimes one of these
branches either itself expands into a large dense plexus, or joins other branches to
form one, from which plexus two, three, or more chords pass into the  substance of
the arachnoid.   The shape of these plexuses is either square or triangular, according
to the number of branches which join them, and the number they give  off.  Besides
consisting of interlacing fibres, they also contain corpuscular matter.
  « The arachnoidal extremity of some of the chords connecting the vessels with the
* Medico-Chirurgical Transactions, 1846. 
541
APPENDIX.
arachnoid of the cauda equina expands, close to the membrane, into a large  oblong
and rather oval bulb, the axis of which is occupied by a continuation of the chord,
extremely convoluted, and bent upon itself;  while, inferiorly, its  fibres are blended
with those of the membrane.
  " The chords which pass from the vessels of the pia  mater, at the upper portion of
the brain to the arachnoid, terminate in the latter by fibres having a stellate arrange-
ment.  There are also some large triangular plexuses like  those at the base of the
brain, from which branches descend between the  convolutions to the vessels within
the sulci.
  " In  the lower animals, as in the sheep, in which the cerebral convolutions are
small, the stellate fibres are the best seen.  They can  even be distinguished by the
naked eye, appearing like minute opaque points.  At their centre, the fibres of which
they are composed, seem to be blended into an irregular confused mass, from which
other fibres  radiate, and  lose themselves in the cerebral surface of  the arachnoid.
Some fibres go from one stellate body to another, and others can be traced into the
coats of the vessels:  these latter are by no means numerous.  Branches also descend
(still having  somewhat  the  stellate disposition) between the convolutions  to the
deep-seated vessels; these filaments are  much  more  numerous  upon some vessels
than upon others, and they do not appear  to extend so  far as the capillaries, no fibres
of any kind being visible upon this system of vessels.
  " It appears, from what has been stated, that the  disposition of the  ramifying fila-
ments of the arachnoidal chords,  and  the form and size of the gangliform plexuses
connected with them, bear some proportion to the  number and size of the vessels in
their vicinity.  Hence, about the base of the brain, where the branches of the arteries
are large, the plexuses are also large, and of an irregular shape, while on its upper
surface, where the vessels are comparatively small, and more equal in size, and  have
a more uniform distribution, the plexuses  are also smaller, more numerous, and more
regular in their shape and volume.
  " Besides the plexuses situated in the course of the chords of the arachnoid, there
are others which are more intimately connected with its cerebral  surface, and which,
in some situations, appear to compose  the entire thickness of the membrane.
  " In  these plexuses, the filaments interlace very much in  the same manner as the
nerves do in the plexuses of the cerebro-spinal and sympathetic systems.  A chord,
for instance, when traced into one of them, will be observed to break up into its  com-
ponent filaments, the adjoining  bundles of which interlace, yielding to one another
one or more bundles, and the chords which emerge from the plexuses deriving  their
component filaments  from  different bundles: these bundles and their component
threads, during their interlacing, will be seen to preserve their individuality.
  " When a chord going from the arachnoid, terminates on a  cerebral nerve, it divides
in the same manner  as an artery, some filaments  ascending and others descending
along with the nerve tubules.  In some instances this  extremity terminates in a sort
of membranous expansion, which encloses several nerve tubules."

  Mr. Rainey, in the next place, enters upon the consideration of the nature of the
above-described apparatus of ramifying chords and plexuses, and arrives at the con-
clusion, derived from their relations and intimate  structure, that they are composed
essentially of gelatinous or sympathetic nerve filaments. 
                               APPENDIX.                           O i.J

  "In  the  chords of the  arachnoid (he writes) I could distinguish three different
kinds of filaments, all which exist in the branches of the sympathetic.
  "One species,  generally considered  the most characteristic, is the nuclear fibre
described by Henle ; it is  a flat, clear fibre, with oval, nearly equi-distant nuclei, and
each having its long axis corresponding to that of  the fibre.  I have  found these
fibres in the  arachnoid, but they are very rare.   I have seen such going from  the
arachnoid to the coat of the internal carotid, the trunks being blended with the mem-
brane, and  the  branches connected with the artery.  I also found, that as the fibres
branch off from these trunks, and intermix with others, they lost their nuclei, became
more pale and  clear, and differed in no respect whatever from the other fibres of the
membrane.  Besides, I have seen these fibres in other parts of the membrane, and
they exist chiefly on the exterior of the larger chords.  This species of fibre I have
also found to be very uncommon in the smaller branches of the nerves confessedly
sympathetic, especially in those most  remote from  the ganglia and larger  trunks.
The next kind  of fibre is  one consisting of bundles,  for the most part rather  smaller
than nerve tubules, of very minute wavy filaments, intermixed with small particles of
granular matter, having no definite form, size, or position in respect to the filaments.
Some of the chords of the arachnoid are made up entirely of fibres of this description;
in others they exist  chiefly on their surface, being most abundant near their attach-
ment to the arachnoid, upon which they are continued.   This kind of fibre exists
abundantly in  all the branches of the nerves undoubtedly sympathetic; and also,
more or less, in those connected with the ganglia.   The third kind of fibre occurs in
the form of roundish, though sometimes flat chords, composed of extremely minute
wavy filaments, either collected or not  into bundles, but apparently interwoven some-
what together, so  that, generally, a filament of only an inconsiderable length will
admit of being detached mechanically from the rest, and, when thus  separated, its
breadth is very unequal, and its contour ill-defined.   These filaments are often totally
destitute of granular matter.
   " This last species of fibre is very common among the chords composing the plex-
uses of the arachnoid; it  is also sometimes situated  in the centre of the larger ones,
surrounded by the second species of fibre; this can be detached mechanically, and
exhibited separately under the microscope.
   "In the nerves  obviously sympathetic, this kind  of fibre  exists in  considerable
abundance in those branches of the solar and other  plexuses which are most remote
from the ganglia.
   "Thus far my observations have been confined to  the structure of the fibres of the
arachnoid, and  their supposed use.  I will now consider the corpuscular or ganglionic
part of this membrane.   Some of the plexuses on its cerebral surface have the inter-
stices  formed by their interlacing fibres, completely filled  up with small roundish
corpuscles, about the size of blood-discs; while, in  others, these fibres are  covered
with irregularly-oval masses of them.  On  this surface, also, in various situations,
there are well-defined round or oval bodies, having in their centre a granular nucleus
surrounded by fibrous tissue,  intermixed  with more or less  corpuscular matter.
Some of these  bodies are connected to the fibres  of the  arachnoid by a very fine
thread others  are  situated at the conflux of two or more  fibrous chords, and  their
diameter varies from that of two to  seven blood corpuscles.  They are generally
solitary and not numerous; but as they have been present in the arachnoid of every
human subject which I have  examined (a number exceeding twenty), they cannot be 
546
APPENDIX
regarded as accidental or adventitious.   At present I cannot decide as to their nature
or office, not having seen any thing which they exactly resemble in other parts of the
body; at any rate, they look more like small ganglia than any thing else I have seen.
  "Besides these corpuscles, which, as before stated, exist on the cerebral surface of
the arachnoid, I have met with some of a very different character, situated in its sub-
stance, though nearer to the cranial than to the cerebral surface.  The most ordinary
appearance which these present, when seen by transmitted light, is that of a section
of an urinary calculus made through its centre, appearing, like it,  to be made up of
concentric layers.  When viewed by reflected light, these bodies seem to be vesicu-
lar, and filled with fluid, the quantity of which appears to diminish as the number of
layers  increases, so  that those in which the laminae  have  extended as far as the
centre, are  almost flat.   Although the most frequent form of these  bodies is circular,
yet some are oval; occasionally they are connected with a fibre of the arachnoid, in
such a manner as to resemble small Pascinian corpuscles. One remarkable fact con-
nected with these bodies is, that they occur in the arachnoid of almost every subject
which I have had an opportunity of examining, and that no  part of the membrane is
exempt from them; generally they are  solitary, and  very sparingly distributed; but
sometimes  they are  in  clusters.   I have found them in the internal  Pacchionian
glands mixed with granular matter, and the same kind of fibre as exists in most parts
of the arachnoid membrane.   Their diameter varies from 75,000 to 39,800ths of an
inch.   I have observed on some parts of the arachnoid, in the vicinity of a cluster of
these bodies, cavities of a similar  shape and size, from which the  corpuscles them-
sel  es  appear to have been dislodged.   From this circumstance, as well as from the
general aspect of these bodies, they seem to me either to be  structures altogether
adventitious, or the  result of an abnormal  deposition in diseased  corpuscles.   The
tendency which they may be observed to have to coalesce when several smaller ones
occur together,  evident by the  obliteration of those portions which seem  pressed
against one another, and the union of the remote segments to form a single outline
enclosing an area whose figure clearly indicates the number  of corpuscles which have
united to form it, proves them to be something more than mere earthy deposits, such
as are sometimes found in the choroid plexuses, or even than mere  scrofulous tuber-
cles.  Vogel has found bodies similar to these in the choroid plexuses;  in these, and
in the pia mater, Dr. E. Harless has also seen them, and given a very minute account
of their structure in a number of Miiller's Archives, 1845. This author seems to think
that their seat is in the arteries, and that they are  somewhat allied  to ossification of
these structures; but their occurrence in all parts of the arachnoid, in some of which
there are Drobably no vessels,  is opposed to this view."

  Mr. Rainey regards the corpuscles constituting the epithelium of the  choroid plex
uses as ganglionary, and details  his reasons for this  opinion; these, however, canno<
be admitted to be decisive on this point.
  "As  respects the  supply of vessels  and cerebro-spinal nerves to the arachnoid, I
may observe, that the arteries are few, but rather  large,  almost  sufficiently so  to
receive a small injection tube; (I have preparations of these;) and that cerebro-spinal
nerves may be traced into its visceral portion, and, with the  microscope, their tubules
(can be seen running along with the arachnoid fibres, into which they appear, from the
gradual loss of their tubular contents, to degenerate." 
APPENDIX.
547
            Structure of the Striped Muscular Fibrilla.
  At page 358, doubts were expressed as to the correctness of the
view entertained by Drs. Carpenter and Sharpey, in reference to the
structure of the striped muscular fibrilla.   At that period, the author
had not seen any of Mr. Lealand's preparations, on the examination
of which, the above-named gentlemen founded their opinion; he has
since, however, been favoured by Dr. Carpenter with the examination
of his  own specimen, and this  would certainly appear  to bear out
fully their opinion of its cellular constitution.

                Structure of the Bulb of the Hair.
  Further opportunities of examination have satisfied the author that
the vesicle which he has described  as forming  a portion  of the bulb
of the hair has no existence, and that this rests immediately upon  a
compound vascular and nervous papilla.

                      The Synovial Fringes.
  The synovial fringes consist of branched and elongated threads  or
filaments, which taper to a point, and each of which is supplied with
one or more, according to its size, contorted and looped blood-vessels;
these,  however, do not reach the  whole length of each thread, but
terminate at one-third or  one-half  its length.  It is in the termina-
tions of these filaments, according to the observations of  Mr. Rainey,
that those cartilage-like bodies sometimes  found loose in the joints,
especially the knee-joint, are first formed.  The threads or filaments of
which the synovial fringes are constituted are of such length and  so
much branched, that they  might, at first sight,  be mistaken for those
of some conferva of the genus Cladophora.

           On the Anatomy of the Sudoriparous Organs.
  Mr. Rainey* describes the duct  of the sudoriparous glands as con-
sisting of two distinot portions, an epidermic and dermic.
  The epidermic portion is of a conical form, the base being directed
towards the surface,  and the apex situated in the midst of the cells
which form the deep layer of the epidermis; it is constituted of cells
which are flattened and elongated, and the long  axes of which are

  "On the Minute Anatomy of the Sudoriparous Organs."  By G. Rainey.—Roy*
Med. and Chirur. Society.  See Lancet, 1849. 
548                       APPENDIX.
disposed in the direction of the length of this portion of the  duct:
below, near its termination, the cells are thicker and less flattened.
  The dermic portion of the duct is also of a somewhat conical shape,
its base being in like manner directed upwards, and its parietes being
continuous with the basement membrane of the dermis;  this portion,
therefore,  is  of a totally different structure from the former;  it is
described by  Mr. Rainey as being lined by a layer of epidermic scales,
which get  gradually indistinct towards the gland, and its upper or
expanded part as receiving the termination of the epidermic division
of the duct.
  This description of the duct of the sudoriparous gland, so far as I
have  been  able to follow it, would appear to be in its main particular
correct, it consisting, as stated, of two portions, an epidermic and a
dermic; the former is scarcely to be regarded, however, as any thing
more  than  an appendage to the dermic part, which is the true duct, it
being little more than a definite channel through  the epidermis.
  It seems to me, however, to be incorrect to describe the epidermic
portion of the duct as commencing  in the deep layer of the epidermis;
it extends beyond and far deeper than this, for it lines the whole length
of the true duct, and this not merely with loosely aggregated cells,
but these are so united together as  to form a  distinct  tubular  mem-
brane, which by maceration  may  be exhibited as such (see  Plate
XXIII. fig. 2); the  epidermic cells  become, in fact, continuous with
those  of the sudoriparous gland itself.
  Mr. Rainey has noticed the fact that the secretion of the sudoripa-
rous glands in the palms of the hands and  soles of the feet, where the
sebaceous glands are entirely wanting, is of a greasy character; from
this circumstance he draws the conclusion that  these glands secrete
both  sweat and sebaceous matter, the former in their more active
state, the latter in their less active condition.
  It is only in the hands and feet, where the epidermis is thick, that
the epidermic portion of the sudoriparous  duct assumes importance. 
INDEX,
Adams, Mr.  On the calculi of the prostate     437
Addison, Dr.  His belief in the existence of a
  nucleus in the red blood disc   .      .      .93
  Views on the structure of the red blood cor-
    puscle      .      .            .      .     94
  Observations on the white corpuscles of the
    blood......103
  Further observations on the same  .      106.111
  His opinion that milk, mucus, and bile are the
    visible fiuid results of the first dissolution of
    the cells.....100
  His opinion that the white corpuscles are the
    foundations of the tissues  and the special
    secreting cells.    .      .      .      .107
  On the presence in increased quantities of the
    white corpuscles in the hard and  red basis
    of boils and pimples, and in the skin in scar-
    latina, ......109
  His opinion that mucous and  pus globules are
    altered colourless blood corpuscles     .    170
  His opinion that out of the white corpuscles
    of the blood, all  other corpuscles met with
    in the body are formed      .      .      . 177
  On the action of liq. potass, on pus      .    189
  On epithelial scales in the air cells of the lungs 397
  On tuburcles of the lungs  .      .      .    4(12
Aggregated or Peyer's glands    .      .      . 414
Albinoes, state of pigmentary cells in       .    287
  Hair of  .      .      .      .      .      -302
Albinus.  The first describer of the nail    .    283
Alcohol and Water      .      .      .      .50
Allen, microscope of            .      •      •  33
Alpaco, blood of     .      .       •      •     ^
Alumina, acetate of          .      .      .57
Ancell.  On the increased quantities of  white
     corpuscles in the  blood  in inflammatory

Andral and Gavarret.'   On the mammillated
    appearance of the red blood discs .      . 138
  Important researches on the pathology of the
    blood            .      •       •      .142
Andral,  A. G.  Camus, and Lacroix.   On the
    Pacinian bodies      .      •       •      • 3|G
Annelidas, blood of          .       •      •     ™
Arachnoid Membrane   .                    54.1
  Ganglionary, character of  .       .      •    543
Area Vasculosa   .      •      •      •      • ^
Arteries, injection of  .      •      •      '     ia
Asphaltum Cement      .      •             •  4J
Axilla.  New tubular gland in.   Plate lvii.
Axillary glands.  Structure of       .      .    130

Baly.  His opinion that the white  globules are
    red blood corpuscles in process of formation 11J
Barry,  Dr.   His belief  in  the existence of  a
    nucleus in the human red blood discs  .     93
  Views on the  structure of the red blood cor-  ^

  Views3on the white blood corpuscle      .    107
  His opinion that  the  tissues are formed by
    direct apposition of the blood corpuscles  . 107
  His discoveiy of spermatozoa on the ovary    233
Bat.  Hair of     .      •      •      •      • "I
Bear.  Spermatozoa of       •
Beclard.  On the disappearance of the fat vesicle 201
Becquerel and Kodier. Researches on the blood 158
Berzelius.  Analysis of healthy ui ine   .      .246
Bidder.   On the peripheral distribution of the
    gelatinous nerve filaments       .      .    382
  On the structure of the kidney       .      . 450
  On the structure of the Malpighian body .    451
Bile.......242
  Epithelium in                    .      .    243
  Cell-like bodies in      .      .      .      .243
  Corpuscles of liver in                       243
  Meconium     ..... 243
Birds, fat of    .      .      .      .      .    255
  Malpighian bodies of         .      .      . 404
Bischoff.   His discovery of living spermatozoa
    in the rabbit eight days after intercourse    227
  His discovery of spermatozoa on the ovary itself 233
  On the structure of the kidney
Blood      ....
  Definition of  .
  Red blood
  Colourless blood
  Composition of .
  Coagulation of without the body
  Death of .
  Quantity of in the body
  Blood of annelid*
  Clot   ....
  Coagulation of blood within the vessels after
    death  ......
  Motling of
  Fluid state of after death
  Globules of   .
  Red
  White
  Venous and arterial blood
  Causes of inflammation
  Exciting cause  .
  Proximate causes
  Pathology of blood
  Blood in the menstrual fluid
  Transfusion of blood   ....
  Importance of a microscopic examination of
    the blood in criminal cases
  Corpuscles, preservation of
       '•     size of  .
  Examination of ....
  Stains, how detected by  the microscope
Bone.  Structure of
  Cancellous structure
  Lamellae of   .
  Medullary cells of   .
  Communications of
  Contents of   .
  Canalicular structure of
  Haversian canals of .
  Contents of ditto
  Arterial and venous Haversian canals
  Lamellae   ...      •      •
  Number and arrangement of ditto .
  Structure of ditto
  Bone cells
  Differences of opinion as to nature of .
  Form of     .■•      •
 450
  79
  80
  80
  80
  80
  80
  80
  80
  80
  81

  86
  85
  87
  88
  89
  100
  134
  140
  140
  140
  142
  100
  100

  104
,  170
  79
.  109
  104
  317
.  317
  317
  317
.  317
  318
.  318
  318
.  319
  319
.  319
  320
.  320
  321
.  321
  321 
550
INDEX.
                                           PAGE
Bone.  Canaliculi of      ...        322
  Size of bone cells in different animals    .    322
  Development of  ditto  .... 329
  Comparison of to stellate pigment       .    330
  Marrow of bones      .... 322
  Periosteum of ditto ....    322
  Vessels of ditto  .      .      .            . 323
  Nerves of ditto     ....    324
  Growth of ditto  .      .      .      .      .324
  Development of  ditto      .      .      .    325
  Intra-membranous form of ossification      . 325
  Intra-cartilaginous form of ditto   .      .    320
  Formation of medullary cavity       .      . 330
  Ditto of medullary cells     .      .      .    331
  Ditto of Haversian canals     .      .      . 332
  Accidental ossification      .      .      .    332
  To make sections of          .      .      . 334
Bowerbank, Mr.   On  the  size  of the human
    blood disc  .....     91
Bowman, Mr.  On the  lining membrane of the
    Fallopian tubes      .... 413
  His doubts as to  the existence of a lobular bil-
    iary plexus .....    423
  His opinion that the series of secreting cells
    represent  the  continuance of  the  biliary
    ducts    .      .      .       .      .      .430
  On  the ciliated epithelium at the neck of the
    Malpighian dilatations    .      .      .    444
  His opinion  that  the  afferent  vessel of the
    Malpighian tuft pierces the dilated extremity
    of the tube      .... 444. 451
  On  the termination of the renal artery on the
    Malpighian bodies        .      .      .    440
  On  the uses of the Malpighian body  .      . 447
Branchiostoma Lubricuni    .      .      .80. 110
Breschet.   On the presence of Pigment in the
    membranous labyrinth of the ear of mam-
    malia   ...... 287
  On  imbibition of cartilages       .      .    312
  On  the communication of the medullary cells
    of bone       ..... 317
  On  a system of osseous canals in flat bones .  3J9
Brewster, Sir David, on the fibres of the crystal-
    line lens      .      .       .      .      .523
Bronchial glands     ....    419
Bronchial tubes  .      .        ... 395
  Structure of  .      .      .      .      .    395
  Larger tubes    ..... 395
  Smaller ditto .....    395
  Mucous membrane of  .       .      .      .390
  Epithelium of      ....    39j
  Muscular fibre-of      .       .      .      .390
Brunner's glands      .      .      .       420,421
  Structure of     ....        421
  Distribution of.  (Vide mucous Glands.)
Brunner's  microscope    .       .      .      .31
Bruns.  On the membrane lining the cavities of
    the true cartilages    .... 307
  On  the nature of bone cells       .      .    321
Buccal glands     ..... 419
Buffy  Coat of Blood, conditions favourable to the
    formation of             ...     85
Built-up cells      .             .      .      .55

Cabinets for objects      .       .      .      .64
Cadaveric rigidity     ....    300
Canada balsam.  Method of mounting objects in  02
Camelidas.   Blood of                  .      .90
  Of dromedary      .      .            .91)
  Of alpaco.      .      .       .      .      .90
  Of vicugua   .....     90
  Of llama......90
Capybara, blood of          .      .      .92
Carnivora, blood of      .       .      .      .92
Carpenter, Dr.  On the structure of the striated
    muscular fibrilla  ....    358
  On  the analogy between striped and unstriped
    muscular fibres      .... 309
  On  the analogy between certain cartilage cells
    and certain algae  ....    314
                                           PAGE
Cartilage.  General structure of  .      .      . 306
  Division of into true and false     .       .    306
  True Cartilages       .       .      .      .306
  Enumeration of     ...       .    306
  Structure of     ..... 306
  Matrix of.....306
  Cavities of       ....      . 307
  Primary cells of     ...       .    307
  Secondary cells of      ...      . 308
  Nuclei of.....309
  Distinction of cartilage into true and false or
    fibro cartilages, to some extent artificial
  Conversion of true into fibro cartilage
  Union of true cartilage with ligament
  Fibru-cartUages     .      .
  Structure of     ...      .
  Cells of      ...      .
  Fibres of .
  Enumeration of
  Nutrition of cartilage
  Pericondrium of
  Vessels of cartilage
  Pathology of .
  Ossification of
  Ulceration of .
  Atrophy of      ...      .
  Growth and development of cartilages
  Of the cells     ....
  By division of ditto .
  By cytoblasts    ....
  By parent cells
  Comparison of cartilage cells to certain algae
  Growth and development of the inter-cellular
    substance     .....
  By a deposit of new layers  .
  By thickening of the walls of the cavities
  Enchondroma
  Uses of cartilage....
  To examine  ....
Caruncula Lachrymalis, structure of
Cat.  Bulb of  hair of .
  Blood vessels of  stomach of
Cells.   Thin glass
  Drilled   .       .      .
  Tube  .....
  Built-up     .....
  Gutta-percha ....
Cements.  Asphaltum
  Canada balsam
  Compound      ....
  Gum  Arabic ....
  Japarmer's gold size
  Marine glue  ....
  Sealing-wax     ....
Cerebellum, ganglion cells of arbor vitae
  Ditto of corpus dentaium
Ceruminous glands
  btructure of
Charriere's syringe
Chevalier's microscope   .       .      ,
Chromic acid
Chyle      .....
  Analysis of   .
  Molecular base of
  Granular corpuscles of
  Chylous blood   ....
  Oil globules of chyle
  Minute spherules of
  Coagulum of .      .
  Serum of       ....
  Nature of          .      .      .
  Contrasted  with lymph .       .
  Colour of in thoracic duct .
  Examination of  .      .       .
Cilia.....
Circulation, capillary
  In embryo of the chick &c.       .
    (Extremities of young spiders, fins of fishes,
    gills of tadpole and newt, tail of water-newt,
    ■web of frog's foot and tongue of frog.) 
INDEX.
PAGE
.  81
   81
.  82
   82
.  82
   83
   83
   83
   83
   84
551
Clot.  Formation of
  Ditto in blood after freezing   '   .  '
  Constitution of        .
  Uength of time for formation o'f  .      .
  Characters of in health and disease   .
  iJitto in diseases of a sthenic character   .
  unto ot in diseases of an asthenic character
  ooftemng of fibrum
  Buffy coat of clot
  Mode of formation of   .
  Adherence of red corpuscles in'rolls hi clot of
    inflammatory blood
  Conditions favourable to the formation of clot
  Cuppuig ot   .
  To what owing  .
  Condition of red globules in
Colostrum.  Corpuscles of
  Disappearance of ditto     .
  Colostrum corpuscles peculiar to the human
    subject     .      .      _                 203
  Purgative qualities of colostrum              203
  Division of pregnant women into three classes
    founded on its characters .      .           207
Comparetti.  On the presence of pigment in'the
    membranous  labyrinth of the ear of mam-
    malia   .      .      .                     287
Compressor, the      .                   .30
Coppin,  Mr. J.  On the circulation in the tongue
    ot the frog
  Corpora Wolffiana  .'.'.'
Corpuscles.  Of the blood.  Red corpuscles '  .
  Colouring matter of  .
  Uses of   .
  Causes of colour of  .
  Iron in
  Origin of     ....'.
  Phases of the development of  .      .
  Final condition of
  Blood  globules of reptiles, fishes, and bird's  .
  Ditto of Camelidae  ....
  Ditto of  the embryo of  fowl    .            .
  Ditto of  young frog  ....
  Blood  corpuscles, dissolution of
  Blood  corpuscles of adult fowl
  Ditto of  tritons and frogs
  Effects of reagents on the red corpuscles .
  Modifications the results of different external
    agencies      .....
  Ditto the effect of commencing dessication
  Ditto the result of ^composition occurring in
    blood abandoned to itself, without the body 139
  Ditto the effect of decomposition in the blood
    within the body, after death     .      .    139
   Effects of certain remedial agents upon  the
    constitution and form of the red  blood    . 102
  Effects of iodine on ditto   .      .      .163
  Peculiar concentric corpuscles in blood    121, 122
   White corpuscles of blood.  Number of
  Size of       ....
  Form of  .
  Structure of  .
  Nucleus of      ...      .
  Properties of  .
  Position of in capillaries
  Motion of in ditto
  Uses in connexion with secretion
  Uses in connexion with nutrition  .
  Aggregation of in capillaries   .
  Increased quantities of in disease  .
  Processes by  which they may be separated
    from the red globules
  Origin of     ...
  Opinions concerning
  Different names for  ....
  (" Central Particles " of Hewson; " Escaped
    Nuclei;" " Parent Cells " of Barry; " Tissue
    Cells " of Addison ; " Fibrinous Globules "
    of Mandl;  "Granule Cells" of Wharton
    Jones; " Exudation Corpuscles " of Gerber;
    "Lymph Corpuscles" of Miiller.)
PAGI
.  174
  174
.  175
  176
.  176
  176
  177
Of Mucus.  Structure of  .
  Nuclei of, single and compound
  I orm of  .      .               '
  Size of      .     .
  Properties of
  Nature of
  Identity of with the pus corpuscle '
  Mucous corpuscles, young epithelial scales   ' 179
 4.,tf' Uentllyof 5U8 wiln mucous corpuscles 183
  Natuie, origin, and formation of pus corpus-
    C16S    ,      #      #                    lfid
Cowper's glands      .               '   42n' 4«,
Creosote    ...          '57
Crustacea, fat of      •".".'      '255
Crusta Petrosa     .      .                "    30c
Cruveilhier, on the calculi of the  prostate   .   ' 437

Davy, Dr.  On the increased quantities of white
    corpuscles in  the  blood in inflammatory
    affections      ..... 109
  On the presence of spermatozoa in the fluid
    of the  urethra after stool in a healthy man  236
Death.  Signs of            .      .      .    .  86
  Real and apparent .       .      .       .'    '  86
  Coagulation of the blood, the most  certain
    sign of .      .      .      .      .     .87
Delia Torre.   On the  annular form of the red
    blood disc   .      .      .      .      .93
Donne. His disbelief in the existence of a nucleus
    in the red blood disc  .      .      .     .93
  On the increased quantities of white corpus-
    cles in  the blood in disease      .      .    109
  Opinions in reference to the blood globules  .  110
  His  opinion that the white globules are red
    blood corpuscles in process of  formation    112
  His  observations on the  conversion of milk
    globules into white corpuscles      .      .112
  On the transition of white globules to red cor-
    puscles  .      .      .     .      .  113, 114
  Reasons  in favour of the opinion that the
    red globules are formed out of  the white    115
  Opinion of, as to the cause of the  maimnilaled
    appearance of  the red blood disc      .    138
  Vaginal tricho-monas of       .      .      .181
  Vaginal vibrios of        .      .      .    182
  Opinions as to the nature of pus  globules      86
  Venereal vibrios of .     .      .      .    194
  On cheese globules     ....  196
  The  discoverer of colostrum corpuscles  .   201
  His  statement that the colostrum corpuscles
    are soluble in ether  .... 202
  On the recurrence of colostrum   .      .   204
  Condition of milk after confinement, in con-
    stant relation with its state during gestation  207
  His  division of pregnant  women into  three
    classes, founded on the characters of the col-
    ostrum during the last months  of gestation  207
  Lactoscope of                .      .      .211
  On the formation of butter .      .      .   215
  His detection of the spermatozoa in the vagi-
    na on the second day        .      .      . 227
Double decomposition.  Injections by     .     44
Drilled Cells  ".....54
Dromedary.  Blood of       ...     90
Dry Way.  Method of mounting objects in the   59
Dujardiu.  On the  human spermatozoon   223, 224
  His statement that spermatozoa lived thirteen
    hours in the testicle after death    .      . 227

Ear, structure of.   See  Hearing,  organ of  .    523
Eble. On the hair at its full term of development 298
  On nerves in the bulb of the hair of the cat   304
Elephant.  Blood of     .       .      •      -92
  Malpighian bodies of                       418
Enchondroma    ..... 315
Epidermis.  Form, size, and structure of cells of 277
  Correspondence of to epithelium      .      . 277
  Disposition of      •••'?!?
  Ditto of lines on the surface of       .      .278
  Effects of water on  .      .      .      .279 
INDEX
                                            PAGE
Epidermis of white and coloured races .      . 279
  Destruction and renewal of .      .      .    279
  Uses of   .      .     .      .      .      .280
  Pathology of .      .      •      .      .    278
  Mr. Rainey's description of          .      .281
  Examination of           .      .      .    281
Epithelium.  Constitution of          .      . 204
  Distribution of      ...          205
  Different forms  of     ...       205
  Tesselated variety  ....    205
  Form of  cells of .     .      .      .      .203
  Size of       .....    200
  Structure of     .     .      .      .      .200
  Distribution of      ...          207
  Conoidal variety ..... 207
  Form and size of cells of         .          207
  Structure of     ....      . 208
  Naked conoidal variety     .      .      -208
  Distribution of   .     .      .      .      . 208
  Ciliated variety     ....    208
  Distribution of   .     .      .      .      . 270
  Development and multiplication of epithelium 271
   Nutrition of dito
   Destruction and renewal of ditto
   Uses of          .      .      .
   Methods of examination of
   Epithelial Tumours
 Ether, injections
 Eustachian glands  .
 Evans, Dr. Julian. On the structure of the spl
 Eye.  See Vision
   Dissection of .

 Fat.  Vesicles of   .
   Contents of ditto
   Form of ditto
   Size of ditto  .
   Colour of ditto   .
   Consistence of ditto
   Structure of ditto
   Distribution  of fat
   Quantity  of
   Disappearance of
   Uses of   .
   Distinction of fat vesicles from oil globules
   Development of the fat vesicle
   Examination of
 Fibrin.  Softening of     .
   Fibrillation of
 Fibrous Tissue
   Wliite Fibrous Tissue
   Enumeration of parts constituted of
   Morphous form of   .
   Amorphous form of
   Condensed form of  .      .      .
   Reticular form of       .
   Areolar form of     .      .      .
   Structure of
   Action of acetic acid on
   Yellow fibrous tissue
   Enumeration of parts constituted of
   Structure  of            .      .   .
   Varieties of  .
  Pecuiiar arrangement of
   Mixed fibrous tissue
   J\Tuclear form of fibrous tissue
  Development of white fibrous tissue
  Ditto of yellow fibrous tissue  .
Fishes.  Bone cells wanting in bone of
Fluids.   Organized
  Lymph
  Chylo
  Blood .      i
  Mucus
  Pus   .
  Semen
   Unorganized .
  Saliva   .      ■
  Bile   .
  Sweat
    272
    272
   . 273
    275
   . 275
     43
   . 419
een 489
   . 509
    533

   . 254
    254
   . 254
    255
   . 255
    255
   . 255
    259
   . 200
    261
   . 202
    262
   . 538
    203
   .  83
    353
   . 340
    346
   . 340
    347
   . 347
    347
   . 347
    347
   . 347
    347
   . 348
    349
  . 348
    349
  . 350
    353
  . 349
    352
  . 352
    322
  . 60
    67

  ' 67l
    79
  . 171
    183
  . 218
   240
  .  241
    242
  . 243
	PAGR
Fluids. Unne	. 2-i5
Pancreatic fluid	250
Lacrymal ditto .	. 250
Gastric ditto ....	250
Preparation of	. 50
For mounting objects	56
Alcohol and Water	. 56
Goadby's Solutions .	56
Acetate of Alumina	. 57
Creosote ....	57
Glycerine	. 57
Canada balsam	57
Salt and Water .	. 57
Naphtha ....	58
Chromic acid	. 58
Method of mounting objects in	59
Follicles. Of stomach	. 410
Of small intestines .	410
Of Lieberkuhn	. 410
Of large intestines .	410
Form of . . .	. 410
Epithelium of	410
Blood-vessels of .	. 411
Follicles of uterus	413
Of P'allopian tubes	. 413
Of vagina ....	419
Of oesophagus .	. 418
Of neck of uterus	418
Of vesicula seminalis . .	. 418
Of Schneiderian membrane	419
Forceps, dissecting	. 33
Cutting ....	34
Frog. Tongue of. Mode of exhibition of . 126	
Gall Bladder.   Structure of  .      .      .429
Gallinae.  Spermatozoa of      ... 220
Gastric juice   .....    250
Gelatine, injections with  . .            .      .48
Gerber.  On the relation between the size of the
    blood globules and the capillaries      .     92
  His belief in the existence of a nucleus in the
    red blood disc .      .      .      .      .93
  On the structure of the spermatic animalculi
    of the guinea-pig       .       .      .      223
  On the stellate bodies observed in decomposing
    fat vesicles    .....  259
  His description of the epithelium of the ven-
    tricles as a tesselated cjliated epithelium     271
  On nerves in the bulb  of«the hair of  the
    guinea-pig    .      .  *   .      .        304
  On the nature of bone cells        .      .     330
Gerlach.  On the structure of the kidney      .  450
  On the structure of the Malpighian capsule    451
Gingival glands   .....  420
Glands.  Definition of .      .      .     .406
  Classification of   .    .   .      .      .     .  408
  a.  Unilocular glands     .      .     .     410
  Follicles of stomach    .      .      .      .410
  Ditto of large intestines    .      .     .410
  Ditto of Lieberkiihn    .      .      .      .410
  Stomach tubes      ....     412
  Fallopian and uterine tubes or follicles         413
  Solitary glands   .....  413
  Aggregated or Peyer's glands.     .     .     414
  b. Multilocular ditto    ....  414
  Sebaceous ditto     ....     414
  Meibomian ditto       ....  410
  Glands of the hair follicles  .      .     .416
  Caruncula lachrymalis  .      .      .      .  418
  Glands of nipple    .      .      .     .418
  Ditto of prepuce       ....  418
  Mucous glands      ....     418
  Labial ditto      .      .      .      .       .419
  Buccal ditto   .      .     .      .     .419
  Tonsillitic ditto   .      .      .      .      .419
  Lingual ditto       ....     410
  Tracheal ditto   .      .     .      .       -419
  Bronchial ditto      .     .      .     .419
  Palatine ditto    .....  419
  Pharyngial ditto     .     .      .     .419 
INDEX.
 Glands of uvula
   Ditto of Eustachian tubes
   Brunner's glands
   Cowper'B ditto
   Gingival ditto   .
   Uterine ditto .
   Vaginal ditto
   Lenticular ditto
   c. Lobular ditto  .
   Salivary ditto
   Mammary glands
   Liver .
   Prostate gland   .   '  .
   d. Tubular glands   .
   Sudoriferous ditto
   Axillary ditto
   Ceruminous ditto
   New tubular gland in axillae kidneys
   Testis    .       .      .         '
   g.  Vascular glands .       .   '   .
   Thymus gland   .
   Thyroid gland      .       ,
   Supra-renal  capsule
   Spleen
   /. Absorbent glands           .
   Lacteal or mesenteric glands
   Lymphatic glands
   Villi of intestines
Glass slides .
   Cells  .       .   "   .
   Thin     .      .      .    '   .   '
   Instruments for cutting
Globules of milk  .
Goadby's solutions     .       .      ,
Goat.  Blood of .
Goodsir.  On  the general development of the
    teeth   .....
   On the classification of glands
   On the epithelium of the villi   .
   On the cells  developed during absorption  in
    ditto      .....
Grallae.  Spermatozoa of  .
Gruby and De la Font. M.M.   On blood discs in
    chyle      .....
Gueterbock.  His opinion that  the colostrum
    corpuscles  axs true cells     .      .      . 202
Guinea-pig, spermatozoa of   .      .      .    219
Gulliver, Mr.  Observatipns on  the molecular
    base of the chyle in the blood      .      .  69
  On the lymphatics of the spleen   .      .     71
  On the ctiaracters of the blood discs in  the chyle 71
  His  opinion  in favour of Hewsoii's  views of
                                              72
                                              90
                                              91
  PAGE
  . 419
    419
420, 421
420,421
  . 420
    420
    420
    420
    422
    422
    423
    423
    430
    437
    437
    441
    441
    441
    483
    484
    484
    480
    488
    489
    492
    492
    492
    493
     51
     54
     51
     52
    197
     50
     92
553
PAGK
     the thymus .
   On the blood of the vicugna and llama
   On blood corpuscles in states of disease
   On the relation in the size of the  blood cor-
     puscles among  the  mammalia, and that of
     the animal from which they proceed       .  95
   On the dimensions of the rod blood discs of
     the elephant, capybara, and napu musk-deer  9:
   His disbelief in the existence of a nucleus  in
     the red blood discs       ...     9;
   His  measurement of  the human colourless
     blood corpuscle      .      .      .       .101
   His observations on the presence of white cor-
     puscles in the blood in unusual quantities in
     inflammatory affections  .      .      .    10S
   His opinion  that  the white globules are red
     blood corpuscles in process of formation  . 112
   His opinion that blood discs  are the  escaped
     nuclei of the white corpuscles   .       .    117
   On the  blood of birds after a full meal    .    118
   On concc ntric corpuscles in the blood, which
     he has styled " Organic Germs," or " Nucle-
     ated Cells ".....122
Gum Arabic cement   ....     51
Guilt.   His statement that the fat  vesicles in
    lean animals contain serosity, and not grease 261
Glycerine   .      .       .      •      .      .57
Gutta-percha cells    ....     55
 Haidlen.  Inorganic components of milk of cow,
     according to
 Hair.  Form of    .
   Size of .'
   Structure of  .
   Ditto of-root of  .
   Ditto of bulb of
   Ditto of sheath of
   Ditto of shaft of
   Ditto of cortex of
   Ditto of fibrous layer of
   Ditto of medullary canal of
   Ditto of follicle of   .
   Growth of hair  .
   Regeneration of
   Nutrition of
   Distribution of
   Number of hairs in different situations
   Erection of  .
   Colour of .
   Gray hair
   Properties of hair
   Hairs'of different animals
    (Of the musk deer, sable, mouse,
   Uses of hair  .
   Transverse sections of
   Sections of, to mount
 Hair Follicles.  Glands of
   Distribution of
   Structure of
   Binary arrangement of
   Steatozoon folliculorum
 Havers.  Glands of
 Haversian canals
 Hearing. Organ of
   External ear
   Auricle, structure of
   Cartilages of
   Muscles of
   Auditory canal  .
   Cartilaginous part of
   Osseous ditto
   Sebaceous glands of
   Ceruminous ditto
   Muscular fibres in
   Middle ear
   Tympanum  .
   Structure of
   Tympanic cavity
   Structure of membrane of
   Openings into
   Ossicles and muscles of
   Transparent cells in .
   Pigment cells in .
   Internal ear .      .
   Osseous labyrinth
   Membranous ditto
   Perilymph
   Endolymph  .
   Structure of the spiral lamina
   Denticulate lamina  .
   Membranous zone
   Structure of the cochlearis muscle
   Cochlear ligament
   Aluscular zone
   Epithelium  of scalae
   Structure of the cochlear nerves
   Of the membranous labyrinth
   Utriculus
   Sacculus  .
   Membranous semi-circular canals
  Otolith
  Otoconia
  Of the vestibular nerves
  Of the auditory nerves   .
Hedgehog.   Structure of spines of
Henle, M.  Theory of the changes of the colour
   of the blood
  Opinions as to the nature of the white corpus-
   cles of blood, lymph, chyle, mucus, and pus 178
            195
          .  291
            292
            292
          .  292
            293
          .  293
            294
          .  294
            295
          .  296
            297
          .  298
            298
          .  299
            30U
          .  300
            301
          .  301
            302
          .  302
            303
bat, martin)  304
            304
          .  305
            305
          .  416
            416
          ,  416
            417
          ,  417
            200
            318
            523
            523
            523
            523
            524
            524
            524
            524
            524
            524
            524
            524
            524
            324
            525
           525
           525
           525
           525
           525
           525
           523
           525
           525
           525
           526
           526
           527
           527
           528
           528
           528
           529
           529
          529
          529
          530
          531
          531
          531
          532
          304

          136
of the cochlea 
554
INDEX.
 rr   i    „■    .  .                           PAOE
 Henle.  His opinions  as to the structure of the
     milk globules     .      .       :      :    197
   On the application of acetic acid to the milk
     globules      .....  199
   His opinion that the colostrum  corpuscles are
     aggregations of  granules in a mucoid sub-
     stance     ....           202
   On the structure of spermatozoa     .      .223
   On the membrane of the  fat vesicle     .    250
   On the nucleus of the fat vesicle     .      .  257
   On  the stellate bodies observed  on decom-
     posing fat vesicles       .       .      .    259
   On  the presence of  fat in the  blood after re-
     peated bleedings    ....  262
   On the absence of epithelium in the bursae    205
   His description of the epithelium  of the ven-
     tricles as a cuneiform ciliated epithelium  .  271
   On the position of the pigment granules in the
     cells      .....    288
   On the fibres of the fibrous layer of the hair   295
   On the medullary canal of hair    .      .    290
   On  the membrane of the cavities  of true car-
     tilage ......307
   On  the  arrangement of the  cells  of articular
     cartilage   .....    308
   On certain large cells, presenting in their in-
     terior  a cavity in  the cartilage  of the epi-
     glottis ......311
   On the increase of the inter-cellular substance
     of cartilages  by the thickening of the mem-
     brane of the  cavities     .       .      .    314
   On the structure of the lamellae of bone     .  320
   On the nature of bone cells        .      .    330
   On the structure of the inter-tubular substance
     of dentine.   .....  337
   On  a  peculiar arrangement of the fibres of
     elastic tissue     ....    350
  On the disposition of gelatinous nerve fibres  380
  On  the proportions-of gelatinous  nerve fila-
     ments in different nerves        .      .    382
  On the arrangement of the gelatinous nerve
     filaments in ganglia  .      .      .      .383
  On the development of nerve cells on the sur-
    face  of the convolutions of  the brain   .     390
  On the epithelium of the choroid plexuses   .  538
Herbivora.  Blood of  .     .       .      .92
Hewson.  On the lymphatics of the spleen    .  71
  His opinion that the thymus is an  appendage
    to the lymphatic system, chyle globules, or
    the corpuscles of the thymus   .      .     72
  His belief in the existence of  a nucleus in the
    red blood disc       .       .      .       :  93
Hodgkin.  His disbelief in the existence of a
    nucleus in the red blood disc    .      .     93
Haematine  .      .       .      .      .       .95
Hooke.  On the hair .      .       :      .    290
Horner, Professor: On the axillary glands     . 441
Hunter.  On the persistence of fat vesicles .    201
Huschke. On the structure of the kidney      . 450
Inflammation.  Causes of
  Exciting cause  .
  Proximate cause
Injections.  Minute
  Objects of
  Of arteries
  Of Veins
  Syringes used in
  By Swammerdam's Syringe
  By Charriere's ditto
  Materials used in
  With turpentine
  With ether   .
  By double decomposition
  Of one set of vessels
  With gelatine
  With fresh milk
Introduction
140
140
140
 38
 38
 39
 40
 40
 40
 41
 42
 42
 43
 44
 48
 48
 48
 27
49
91
116
175
                                           PAGE
Jacobi.  Experiments in fertilizing the ova of a
    carp       .....    234
Japanner's gold size      ....
Johnson, Dr. G.  On fatty degeneration  of the
    kidney     ....      454,40"
  On the inflammatory diseases of ditto       . 40;
Jones, Mr. Wharton.  On the presence of a nu-
    cleus in the blood disc of the lamprey .
  On the mulberry or granulated  appearance of
    the red blood disc    •      .            .94
  On the structure of the red blood corpuscle    95
  Opinions concerning the white blood corpuscle 111
  Observation on the blood corpuscle, consider-
    ed in its different phases of development in
    the animal series ....
  On the nuclei of mucous corpuscles  .
  On the brown pigment of the membranous
    labyrinth of the ear of man     .     .    287
  Ou the tubular character of the  gelatinous
    nerve filaments       .... 382
  On the structure of the ganglion caecum in the
    dog ......    382
Jones, Dr. Handfield.  Reasons for his non-belief
    in the existence of a lobular biliary plexus  425
  His investigations as to the terminations of the
    biliary ducts     ....    420
  On the arrangement of the hepatic cells in
    connexion with secretion    .      .      . 427
  On the union and consolidation of the hepatic
    cells       ....
  Description  of the active  and passive  condi-
    tions of the lobules of the liver
  Ou the development of the liver  .
  On the calculi of the prostate  .
  On the peculiar corpuscles in the spleen .
  On the epithelium of the villi  .
  On the granular substratum in ditto
  On oil drops in ditto   ....
427.

42e
434
437
491
493
494
494
 Kidney.  Secreting apparatus of    .      .     442
   Tubes of......442
   Tubes of, in cortical part   .      .      .     442
   Tubes of, in medullary part   .       .      . 442
   Basement membrane of          .      .     443
   Frame-work for the lodgment of tubes      . 443
   Malpighian dilatations     .      .      .     443
   Vessels of      .....  443
   Capsules of  .      ...      .      .     444
   Epithelium of the tubes      .       .      .  444
   Ditto of  Malpighian dilatations    .           444
   Ditto of  neck of Malpighian dilatations      .  444
   Vascular apparatus of kidney    .      .     444
   Renal artery    .....  444
   Renal vein   .....     445
   Inter-tubular plexus    ....  445
   Portal vein   .....     445
   Portal system    .....  445
   Afferent  vessel of Malpighian tuft        .     445
   Efferent vessel of Malpighian plexus  .      .  445
   Malpighian body, structure of, when complete  447
   Malpighian bodies of  birds and reptiles      .  448
   Size of       .....     448
   In elephant and birds  ....  418
   Development of the kidney .      .      .     449
  True capsule of the Malpighian tuft  .      .  452
  Pathology of the kidney    .      .      .     453
  To inject......482
Kiernan.   His description of the biliary ducts,
    and of the lobular biliary plexus       .    424
  On the acini of the liver     .      .      .  424
Kieser.  On the pigmentary membrane of the eye 286
Kolliker.  On the absence of internal organs in
    spermatozoa   ..... 225
  On the development of spermatozoa      .    231
  On non-striated muscle  .... 371
  On the structure of the kidney    .       .    450
Labial glands
Labelling slides, method of
Lachrymal fluid
.419
  63
 250 
INDEX.
                                           PAGK
Lachrymal glands     .      .      .      .423
Lacteal or Mesenteric glands     .      .      .492
Lactoscope     .      .      .      .      .211
Lallemand. On the development of spermatozoa 230
Lambotte. His disbelief in  the existence of a
    nucleus in the red blood disc   .      .     93
Lamina fusca, pigment cells of  .      .      . 288
Lampenhoff.   Ou  living semen in the vesiculie
    seminales of dead men   .     .           227
Lamprey.  Blood of     .      .      .      .91
Lane, Mr.  Analysis of chyle      .       .     68
  On blood discs in the chyle    .      .      .71
  His belief in the existence of a nucleus in the
    red blood disc     ....     93
  Views on the structure of the red  blood cor-
    puscle        .      .      .      .      .95
Llama.  Blood of            .     .     .91
Lealand and Powell.  Microscope of   .      .  2'J
Letheby, Dr. H.  On cell-like bodies in the bile  243
  On the calculi of the prostate .      .      .  437
Leeuwenhoek.  The first to describe  the  blood
    globules in different animals     .     .     89
  The  discoverer of milk globules      .      .  197
  His  discovery of living  spermatozoa  in  the
    uterus and Fallopian tubes of a bitch, seven
    days after connexion      .      .     227,233
  On the discovery of spermatozoa     .      .  218
  On the spermatozoa of the ram  and rabbit    223
  The discoverer of epithelium cells  in the mu-
    cus of the vagina    ....  204
  The first to observe  that  the  epidermis was
    composed of scales
  On the haii-
 Lenticular glands
 Liebig.  On the condition of iron in the blood
 Liq. potass., action of, on pus
 Liston, Mr.   His disbelief in the existe:
     nucleus  in the red  blood disc
 Lingual glands .
 Liver       ....
   Secreting  apparatus  of
   Lobules of
   Form of
   Size of
   Union of
   Inter-lobular fissures
   Inter-lobular spaces  .
   Follicles, or acini
   Biliary ducts .
   Lobular biliary plexus .
   Doubts concerning   .
   Mode of termination of
   Structure  of .
   Secreting  cells   .
   Structure  of .
   Linear and radiated disposition ot
   Union of     .      •       •
   First secretion of bile in central celts
   Active and passive  conditions  of  "~
     of the liver
   Dissolution of membrane of
   Gall bladder .
   Structure of
   Vascular apparaUts of liver
   Hepatic veins
   Central-lobular veins
   Sub-lobular veins
   Portal veins .
   Inter-lobular veins
   Lobular capillary plexus
   Hepatic artery    •
   Pathology of liver   .
   Development of  .
   Prostate gland
   Structure of
   Epithelium of
   Calculi of
   Increase  of in old age
   Injection  of
  Locus Niger.
Ganglion cells of
       290
       420
        98
   106,188
ce of a
        93
       419
       423
       424
       424
       424
       424
       424
       424
       424
       424
       424
       425
       425
       420
       420
       420
       427
       427
       427
       427
the
lobules
                                          PAGE
Lungs.  Aeriferous apparatus of      .      . 395
  Bronchial tubes     ....    395
  Air cells  .      .      .      .      .      .396
  Form of            .      .       .      .390
  Size of   ...... 397
  Structure    .....    396
  Communications of    ...      . 396
  Models of          .      .       .      .397
  Epithelium of   .      .      .      .      .397
  Vascular apparatus of                     398
  Arteries   .      .      .      .      .      .398
  Veins ....            .398
  Capillaries      .      .      .      .      .398
  Natural inflation of lungs .      .      .    398
  Artificial ditto.....398
  Mr. Rainey on epithelium in the air cells of  404
  Of birds......404
  Injection of  .                            405
 Lymphatics.  Structure of      .     .     .76
  Valves in          .      •      .     .77
 Lymphatic glands.  Structure of .     .     . 492
 Lymph ......     67
  Analysis of      .      .      •      .      .08
  Coagulum of .      .      .     .      .08
   Granular corpuscles of  .     .     .      .09
   Serum of           .      .      •           09
  Examination of  .      .     .     .      .76
 Lymphatic system.  Structure of lymphatics    07
   Ditto of lacteals .       .      .      .      .68
   Ditto of lymphatic glands  .     .      .    492
   Ditto of mesenteric glands     .      .      . 492
   Thoracic duct       ....    08
   Blood in lymphatics of spleen  .      .      •70

 Madder.   In bones of animals fed with     .   324
 Magendie.  His disbelief  in the  existence of a
     nucleus in the red blood disc
   Experiments of, on the blood
 Malpighi.  The discoverer of  the red globule
 Mammary Glands.  Structure of
   Efferent ducts of        ...
   Milk globules in follicles of
   Follicles of
   Existence of mammary  gland  in the human
     mole       ...••   423
   Epithelium of   .      •      •      •      ■ 423
   Degeneration of mammary glands in age .   423
   Lacteals of.....423
 Man.   Spermatozoa of       ...   21J
 Mandl.   On  the blood of the dromedary  and
     alpaco  .      .      •      ■      •      .90
   His  belief in the existence of a nucleus in the
     red blood disc     ....     93
   His  opinion that the formation of the nucleus
     of the  blood corpuscles of reptiles takes
     place subsequently to the removal  of the
     blood from the system      •      .      .124
   Opinion as to the nature of pus  and mucous
     globules    .                             1™
   Opinion as  to the structure of  milk globules  197
   On the  structure of the  fat vesicle .      .    257
   On stellate bodies observed in  decomposing ^
     fat vesicles     .
  Marine glue    .      • .     •
  Martin.   Structure of hair of
  Materials used in injections  .     .
  Mayer, E. H.  On the nature of  bone cells
  Medulla Oblongata. Ganglion cells of
  Menobranchus.   Bone cells of   .
  Meibomian glands
   Number of
   Form of            •
    Structure of     •      •.■_...'
  Meckauer.  On the structure of cartilage
  Microscope.  Of Allen
   Brunner      •
    Chevalier  .
    Oberhauser  .
    Pike & Sons     .      .     •     ■
    Powell & Lealand   .
 93
153
 88
423
423
423
423
259
 50
304
 42
330
377
321
416
416
416
416
311
 33
 31
 30
 30
 33
 29 
556
INDEX.
                                           PAGE
Microscopes.  Of Ross   .      .      .      .29
  Smith & Beck      ...      .30
  Spencer  .      .      .      .      .      .31
Microtome     .            ...      34
Milk.  Inorganic components of        .      .  195
  Organic constituents of                      195
  Analysis of     ....   209,211
  Serum of           .     .      .      .190
  Cheese globules of  .          .      .      .  196
  Fatty ditto ot       .     .-     .      .197
  Form, size and structure of          .      .  197
  Opinions of observers as to the structure of   197
  Action of boiling water, boiling alcohol, the
    alkalies, acetic acid, and aether on     .     200
  Colostrum of          .      .      .      .  201
  Patholagy of milk   ....     203
  Milk of unmarried women   .      .      .  206
  Ditto of women previous to confinement .     206
  Ditto of women who have been delivered, but
    who have not nursed their offspring      .  208
  Milk in the breasts of children    .      .     208
  Different kinds of milk .      .      .      .208
  Relative proportions of the elements of milk
    in woman, the cow, the goat, and the ass   209
  Good milk      .      .       .      .      .210
  Poor milk    .....    212
  Rich milk       .      .      .      .      .213
  Adulteration of milk      .      .      .    213
  Formation of butter   ....  214
  Milk abandoned to itself   .      .     .    215
  Penicillum glaucum in .      .      .      . 216
  Medicines in milk   ....    217
  Injections with milk   .       .      .      .48
Mitscherlich.  Observations on the saliva       241
Mondini. On the pigment of the eye     .    286
Mounting objects.   Method  of  .      .      .56
  The dry way .....     59
  In Canada balsam with heat   .      .      .60
  As opaque   .....     63
Mouse.  Spermatozoa of .      .      .      . 219
  Structure of hair of .      .      .     .    314
Mucus.  General characters of   .      .      . 171
  Ditto of true, false, and mixed membranes     172
  Corpuscles of          .      .      .      . 174
  Mucus of different organs  .      .      .    179
  Vaginal and uterine ditto      .      .      . 180
  Effect of acid mucus on the teeth .      .    180
  Tricho-monas in vaginal mucus      .      . 181
  Vibrios in ditto      .      .      .      .182
  Distinctive characters of mucous and pus   . 186
Mucous Membranes.  True  or compound        172
  False or simple and mixed       .      172, 418
   Compound.    Alimentary canal from  cardia
     downwards   ..... 419
  Gall-bladder, oesophagus, vagina        .    419
  Neck of uterus, vesiculse seminalis   .      .419
  Simple.  Eustachian tubes .      .      .    419
  Trachea, bronchial tubes,  and bladder         419
  Unimpregnated uterus  .... 419
  Mixed.  Mouth  and nose  .      .      .    419
 Mucous Glands.  Structure  of          .      . 420
  Follicles, epithelium, and membrane of   420,421
 Miiller.  On blood discs in the chyle .      .     71
  On the quantity of blood in the system      .  80
  On the coagulation of blood after freezing      81
  On the blood of the frog      .     .      .82
  His belief in the existence of a nucleus in the
     red blood disc     ....     93
  His verification of the white globules  in  the
     blood of a frog       .      .     .      .100
  On spermatozoa     ....    223
  On the terminations of nerves in the mem-
     brana nictitans       .... 385
  On the kidney      ....    450
 Muscle.  Voluntary      .      .     .      .354
   Involuntary   .....    354
   Of animal and organic life    .     .      . 354
   Striped and unstriped     .      .      .     354
   General structure of muscle   .     .      . 355
   Of unstriped muscular fibrilla     .       .    355
Muscle.  Nuclei of unstriped fibrilla
  M uscular structure of the heart
  Of striped muscular fibre     .      .
  Size and form of
  Size of, in foetus and adult
  Cause of striation of
  Differences of opinion as to
  Lacerti, or bundles of fibres
  Structure of fibrillae of fibres  .
  Nuclei of     ...      .
  Situation of, in the fibre
  Sarcolemma
  Cleavage of fibre
  Blood-vessels of muscles
  Nerves of ditto   ....
  Union of muscle with tendon     .
  Muscular contraction    .      .      .
  Active and passive contraction of muscle
  Zigzag disposition of the fibres in  .
  Approximation of the striae in
  Increase in the diameter of the fibre in
  Rigor  Mortis    ....
  Muscular sound
  Developments of muscle, three stages of
  Differences of opinion as to striation
  Kolliker.  On non-striated variety of .
  Examination of
Muscular rigidity.  A sign of death
Musk Deer.  Structure of hair of
  PAGK
  .  355
    350
  .  357
    357
  .  357
    358
  .  358
    357
358,547
    359
  . 3: 9
355, 359
  . 361
355, 361
  . 301
    362
  . 303
    303
    303
  . 305
    305
  . 306
    306
  . 367
    358
  . 371
    375
  .  87
    304
Nachet.  Microscope of      ...     31
Nails.  Structure of     .      .      .      .282
  Development and Pathology of  .      . 283, 284
  Modification of in the animal kingdom    .    285
  Regeneration and Examination of    .      . 285
  Mr. Rainey on the structure and formation of  541
Naphtha    .      .      .      .      .      .58
Napu Musk Deer.  Blood of  .      .      .92
Nasmyth Mr.  On the constitution of the inter-
    tubular substance of dentine      .      . 337
  On secondary dentine      .      .      .    337
  His opinion that the cementum passes over the
    entire surface of the enamel of the tooth 338,344
  On the development of dentine      .      . 341
Nasse, Professor.  On the adherence of the red
    corpuscles in rolls                          84
  On a mottled appearance characteristic of in-
    flammatory  blood     .      .      .      .85
  His  opinion that the white globules are red
    blood corpuscles in process of formation    112
  On the milk globules   .... 200
  On  the  speedy disappearance of colostrum
    corpuscles in women who have borne many
    children   .....    203
Needles.  Dissecting      .      .      .      .35
Nerves.  Cerebro-spinal system      .      .    376
  Sympathetic ditto      .... 380
  Structure of nerves  ....    370
  Uf cerebro-spinal system      .      .      . 376
  Secreting, or cellular structure of  .      .    376
  Disposition of          .      .      .      . 376
  Granular base and cells of  .      .      .    376
  Caudate ganglion cells and distribution of   . 377
  Globular ganglion cells.  Distribution of  .    378
  Of the tubular structure      .      .      . 378
  Of the cerebrum and nerves of special sense  378
  Of cerebellum and spinal cord  •  .      .    378
  Of posterior root of spinal nerves    .      . 378
  Of sympathetic system and motor  nerves     378
  Varicose dilatation of the tubes    .      .    378
  White substance of Schwann in     .      . 379
  Neurilemma  .....    379
I  Axis cylinder    ..... 380
  Globules of white substance of brain    .    380
  Ditto of spinal marrow, and nerves of special
     sense   ...... 38')
   Of sympathetic system    .      .      .    38.)
   Structure of nerves of  .      .      .      . 380
   Gelatinous nerve fibres of  .      .      .    38J
   Where best seen       .... 3bl 
INDEX,
N       n                                 PAGK
serves  Proportion of nerve fibres in different  381
  Structure of ganglia       .      .      .381
  lubular and gelatinous nerve fibres in       . 383
  Arrangement of    .      .      .      .383
  Ganglion globules and nerve fibres in .      .384
  Origin  and termination of nerves  .      .    384
  Origin in ioops  ..... 384
  In ganglion cells     .      .       .      .385
  Termination in loops    .       .            .385
  In definite extremities     .       .      .    386
  Blood-vessels of nerves       .      .      . 384
  Pacinian bodies     ....    380
  Development of nerve fibres   .      .      . 388
  Ditto of ganglionary cells  .       .      .389
  Regeneration of nervous matter      .      . 390
  Researches of M. Robin    .      .      .291
  Examination of  .....  394
Nesbitt.  The first  to  distinguish between the
    two forms of ossification .
Neurilemma       ....
Nipple, glands of     ...
Nose.   Structure  of mucous  membrane of.
     See Smell
   325
   379
   418

  . 505
99, 108
Nutrition, corpuscular theory of

Oberhauser.  Microscope of           .      .30
Objects of minute injections  ...     38
Oesophagus.   Muscular fibres of, striped  and
    unstriped     .....  360
Omnivora.  Blood of  .      .      .      .92
Opaque objects.  Methods of mounting       .  63
Organs of the senses.  Touch       .      .     497
  Taste     .      .      .      .      .      .501
  Smell and Vision    .      .      .      .     505
  Hearing  ......  523
Owen, Mr.  His disbelief in the existence of a
    nucleus in the red blood disc       .      .  93
  On the development of dentine    .      .     341

Pacini. On the Pacinian bodies .      .      .  386
Pacinian bodies.  Situation and structure of     386
  Inner system of capsules of       .      .     387
  Termination of nerve in                      387
  Inter-capsular ligament of .      .      .     387
  Varieties in form and structure of
Pacchionian glands.  Situations and forms of
Palatine glands        ....
Palmipedes.  Spermatozoa of
Pancreatic fluid       ....
Papillae of skin    ....
  Examination of     ...
Pappenheim.  On the structure of the kidney
Passeres.   Spermatozoa of
Pathology.   Of the blood .
   Of the red corpuscle
  Increase of in plethora .
  Decrease of in anaemia
  Increase of,  under  the  influence of recovery
     and certain medicinal agents
  Effects  of disease on the white corpuscles .
  Deficiency of fibrin  in fevers, typhus,  small-
     pox,  scarlatina, and measles .
  Increase of fibrin in  inflammatory affections,
     as pneumonia, plueritis, peritonitis, acute
     rheumatism      .     ■ .      •      •    148
  Condition of the blood in hemorrhages     . 151
   Decrease in the normal portion of albumen    154
  Becquerel and Rodier's pathological researches
     on the blood   .      .      •      •     .158
   Blood in ecchymoses       .      .      .    161
 Of  milk.  Persistence  of,  in the condition of
     colostrum      .
   Recurrence of colostrum   .
   Influence of retention of milk
   Pus and blood in milk
  The milk of  syphilitic women  .      .     .
  The milk of  women in case of the premature
     return of the natural epochs
 Of the semen      .
 Of the urine    .
Pathology.  Of albuminous urine             . 247
  Fibrinous, fatty, chylous, and milky ditto     248
  Excess of mucus in ditto  .      .      .    249
  Blood in ditto    ...            . 249
  Pus in ditto ..."            ' 250
 Of epidermis      .      .      .             278
 Of nails       .      .       .      .         ' 28-1
 Of pigment cells   ...             286
 Of cartilage    ...                31 j
 Of the luvgs.  Emphysema      .      .       399
   Asthma  and pulmonary apoplexy .      .   400
   Pneumonia and tubercles      .            . 401
 Of liver.   Secreting apparatus      .      .   432
   Biliary and fatty engorgement of cells   '  . 432
   Vascular apparatus.   Anaemic condition of
     lobules ......  433
   First stage of hepatic venous congestion  .    433
   Second stage of ditto    .... 433
   Nutmeg or dram-drinker's liver   .      .    433
   Portal venous congestion      .      .     . 433
   Hydatids and cysts in liver .      .      .    434
 Of the bile     .....    433
 Of kidney. Fatty condition of      .      . 452, 407
   Pathology of "Bright's disease," according to
     Toynbee    .....    455
   Sub-acute inflammation of the kidney       . 457
   Cystic disease of ditto     .      .      458, 405
538
419
220
250
498
500
451
219
142
142
143
144

146
146

147
 Inflammatory diseases of the kidney
 Acute desquamative nephritis
 Chronic ditto    .....
 First and second form of fatty degeneration
 Exudation, and ditto within the tubes
    a. Crystalline or saline deposits .
    b. Oleo-albuminous exudation
    c. Exudations in the form of pus
 Exudation within the Malpighian bodies
 Exudation in the inter-tubular tissue
 Partial distribution  of the oleo-albuminous
    exudation      .....
 Lesions affecting chiefly the vascular system
 Congestion followed  by permanent  oblitera-
    tion of capillaries of cortical substance
 Waxy degeneration  ....
 Lesions of the tubes and epithelium  .
 Imperfect development of cells and nuclei
 Desquamation of the epithelium
 Obliteration  of the tubes
  Microscopic  cyst formation
 Dilatation and thickening of the tubes
 Conclusion      .....
Of thyroid gland.   Condition of, in goitre  .
Paint injections    .                  •      •
Peyen.  His analysis of the milk of woman
Pearson. On  the colouring matter of  the lungs
    and bronchial glands
Peligot, M.   His  observations on milk retained
    for a long  time in  the breast
Peyer's glands     .      .     .      .      •
Pharyngeal glands
Pia mater.  Structure  of  .
  Choroid plexuses and velum inter-positum of 538
  Villi, blood-vessels, and epithelium of       . 538
Pig.  Fat vesicles of  .
  Bulb of hair of  .
Pigment Cells. Structure and situation of
  Pathology of and freckles
  Cells of the choroid  .
  Of the iris and ciliary processes
  Of the lamina fusca  .
  Pigment cells in  the skin
  Ditto of outer surface of choroid
  Pigment granules
  Examination of
Pike and Sons. Microscope of  .
Pineal Gland.  Caudate cells of
  Compound and calcareous cells of
  Earthy matter of
  Blood-vessels and nerve tubules of
Pipettes        .      •      •
Pituitary gland.  Lobes of
 462
 463
 464
 467
 409
 469
 470
 470
 470
 470

 470
 471

 472
 472
 474
 474
 474
 475
 476
 478
 479
 488
  42
 209

 287

 204
 414
 419
. 537
254
304
286
287
288
288
288
289
289
289
290
 33
536
536
536
537
 37
535 
558
INDEX.
                                           PAGE
Pit'y glands.  Structure and infundibulum of    585
  Comparison ot, to a ganglion  .      .      . 535
Porcupine.  Bulb of spines of      .      .    304
Powell and Lealand.  Microscope of   .      .29
Preparation of objects ....     37
Prepuce, glands of       .... 418
Preservation of objects       ...     49
Prevost and Dumas.  Their observations of liv-
    ing spermatozoa seven days after connexion 233
  Experiments on the semen    .      .      . 234
Proteus.   Blood globules of  .      .      .    123
  Shape  of bone cells of .     .      .      . 321
Purkinje.  On  the  vibratile  epithelium of the
    ventricles  .     .       .      .      .271
Purkinje and Valentin.  On ciliary motion 269,270
Pus.  General characters of   .      .      .    183
  Distinctive characters  of pus and mucus    . 186
  Action of liq potass, and sol. anion, on pus 106,188
  Distinctions between certain forms of pus and
    mucus  ...... 190
  Detection of pus in blood   .      .      .191
  False pus.....192
  Metastatic abscesses ....    193

Quekett  Mr.  His disbelief in the existence of
    a nucleus in the red blood disc     .      .  93
  His opinion on the  mammillated  appearance
    of the red blood disc     .      .      .   139
  On bone cells    ..... 322
  On the calculi of the prostate     .      .   437
  On looped blood-vessels in the olfactory re-
    gion of the foetus     .... 508
Quevenne, M.  On the cheese globules    .    196
  On the milk ditto      .      .      .     .200
 Rainey,  Mr.  On epidermis  .      .      .    281
  On trie structure and formation of the nails   541
  On the ganglionic character of the arachnoid
    membrane of the brain and spinal marrow  543
  On healthy air cells    .... 397
  On sudoriparous  glands    .      .      .    439
  On lungs of birds     .... 404
  On the structure of the sudoriferous glands    547
  On the synovial fringes .... 247

 Ram.  Spermatozoa of                        223
 Rapaces.  Spermatozoa of                    220
 Rapp.  On nerves in the bulb of the hair of the
    seal, porcupine, &c.     .      .      .    304
 Rat.  Spermatozoa of          .         '     223
 Rees, Dr. G. O.  Analysis of lymph .     .    68
  His  belief in  the existence of a nucleus in
    the red blood disc    .      .      .     .93
  On the structure of the red blood corpuscle     95
  On the urine of persons taking cubebs, &c.   247
 Reichart.  On the kidney    .            .    450
 Reptilia.  Blood globules, form and size of   .  123
  Structure of   .     .      .      .      .124
  Action of water on     ...     . 124
  Ditto of acetic acid on                     123
  White globules of            .      .     .125
  Plastic properties of red ditto     .      .    125
  Fat of reptiles  .      .      .      .     .255
  Malpighian bodies of                        426
 Respiration.  Corpuscular theory of         .99
 Rhinorceros.  Blood of      ...     92
 Rigor .Mortis       ..... 366
 Robin, M. C. Researches on the nervous system  391
  On the axillary glands  .      .      .     .441
 Rodentia. Hair of   .      .      .      .304
 Ross.  Microscope of           .      .     .29

 Sable.   On the medullary canal of hair of      296
  Ou the structure of the hair of       .     . 304
 Salamander.  Spermatozoa of      .      .    223
 Saliva.  Amount of      ...       241
  Mitscherlich's observations on          .241
  Solid constituents and salts of .     .     . 241
  Acetic acid in     ....    241
  Admixture of saliva with mucus     .     .241
  Uses of.....242
                                           PAGE
Salivary Glands.  Structure of  .      .      .  422
  Follicles and form of, in embryo   .      .     422
Salt and water     .      .      .      .      .57
Sarcolemma    .....    355
Scalpels for dissection    .      .      .      .33
Scansores. Spermatozoa of  .      .      .    223
Scarpa.   On the  presence  of pigment in the
    membranous labyrinth of the ear of  Mam-
    malia  ......  287
Scherer.   On pigment cells in the bile      .    243
Schuliz.   Observations on the action of oxygen
    and carbonic acid on the form of the  blood
    corpuscles    ....    136,137
  Ditto of iodine on ditto     .      .      .    1G3
Schumlansky.  On the structure of the kidney  450
Schwann.  On the membrane of the fat vesicle  256
  On the nuclei of the fat vesicle       .      .  256
  On the  motion of the pigmentary granules in
    the cells of the choroid   .      .       .    288
  On the  membrane lining  the cavities of true
    cartilage      ..... 307
  On the  nature of bone cells      .      .    330
  On the  tubular nerve fibre in the early stages
    of its development   .... 382
Sebaceous glands.     ....    414
  Distribution, secretion, and cells of   .      • 415
  Structure of ...                 416
Sequin.   On the amount of fluid passing off by
    the skin.....243
Semen.   Characters of          .      .      ■ 218
  Spermatozoa        ....    218
  Pathology of semen    .      .      .      • 234
  Application of  a microscopical  examination
    of the semen to legal medicine  .      .    237
Sharpey,  Dr.  On the structure of the lamella of
    bone......320
  On intra-membranous ossification .      .    325
  On the  striated muscular fibrilla      .      . 358
Sidall.  On the increased quantities of white cor-
    puscles in the blood of the horse in influenza 109
Siebold.  On the absence of internal organs  in
    the spermatozoa      .... 225
  On the development of spermatozoa     .    230
  On  living ditto in the uterus and fallopian
    tubes eight days after connexion   .      . 233
 Simon, M.   Organic   constituents of human
    milk, according to .     .      .      195,209
  Analysis of sweat      .... 244
Simon, Mr.  On the thymus      .    73, 485, 486
  On sub-acute inflammation of the kidney     457
Siren.  Blood globules of"    .      .      .    123
  Bone cells of    ...      ■      • 32]
  Skey.   On  the size of muscular fibres of the
    heart      .....    35C
Skin.  See Touch.....497
  Smell.   Structure of mucous membrane  of
    nose       .....    505
   Tactile region  ..... 506
  Epidermis, papillae, and hairs of  .      .    506
  Sebaceous glands of          .      .      . 506
  Pituitary region   ....    506
  Epithelium, and mucous follicles     .      . 505
  Blood-vessels of    ...      .    506
   Olfactory region.  Position of .      .      . 506
  Characters, epithelium, and glands of    .    507
  Pigment cells and blood-vessels of   .      . 508
  Looped ditto of in foetus   .      .      .    508
  Gelatinous nerve filaments of  .      .      . 508
  Olfactory lobes and filaments     .      .    508
Smith and Beck.  Microscope of      .      .30
Spallanzani.  The discoverer of the white glo-
    bules in the blood of salamanders     .    100
I  Experiments on frogs with spermatized water 234
 Spencer.   Microscope of           •      .31
 Spermatophori    ..... 228
 Spermatozoa   .....    218
   Form of (in man, the rat, the mouse, guinea-
     pig, in birds, tritons, and salamanders)    . 219
   Size and structure of  .      .      .    220,221
   Motions and mode of progression of .      .225 
INDEX.
559
Spermatozoa.  Duration of motion  .      .    220
  affects of reagents on  .      .      .      .227
  Development of    ....    229
  Spermatozoa essential to fertility     .      . 232
  Condition of, in hybrids    .      .      .233
Spinal Chord, gauglion cells of   .      .      . 377
Spleen.  Structure and capsule of   .      .    489
  Blood-vessels and secreting structure of    . 489
  Dr. Jullieu Evans on       ...    489
  Dr. Jones  on    ....      . 491
  Peculiar corpuscles in                       491
  Lymphatics of   .       .      .      .       .70
Solids.   ......    253
  Fat       .      .      .      .      .       .254
  Epithelium   .....    264
  Epidermis      ..... 277
  Nails  ......    282
  Pigment cells    .      .      .      .       .286
  Hair   ......    291
  Cartilages       .      .      .      .       .306
  Bone  ......    317
  Teeth     .      .      .      .      .       .335
  Cellular or fibrous tissue   .      .      .    346
  Muscle   ...... 354
  Nerves      .....    376
  Glands   .      .      .     .      .      .406
Solitary Glands.  Distribution and structure of  413
  Orifices of      ..... 413
  Follicles of Lieberkhun   .          '  .    414
Supra-renal Capsule.  Structure and tubes of   488
  Molecules, granular nuclei, and parent cells of 488
  Differences in medullary and cortical portions  488
  Vascular distribution in         .      .    488
  Capsule of      ..... 489
Steatozoon Folliculorum     .     .      .    403
Stomach Tubes.  Arrangement of     .      . 412
  Form, structure, and epithelium of       .    412
  Existence of in the duodenum      .      . 412
  Modification of, near the pylorus  .      .    412
Sudoriferous Glands      .... 437
  Distribution and structure of      .      .    437
  Tubes and ducts       .... 438
  Secreting cells, number of  .     .      .    438
  Mr Rainey's description of          .      . 439
  Examination of     ...      .    440
  Structure of, according to Mr.  Rainey .      . 547
Swammerdam's syringe      ...     40
Sweat.   Quantity of      .     .      .      .243
  Scales of epidermis in     .     .      .    244
  Solid constituents and analysis of    .      . 244
  Crystals in          .      .     .      .244
  Pathology of.....245
Synovial Fringes      .      .     .      .547
Syringes  used in injections     .      .      .40

Table of magnifying powers  .
Taste.  Structure of mucous membrane of tongue
  Chorium and papillae of
  Simple and compound  ....
  Filiform, and fungiform    .      .      502,
  Variety of ditto, and calyciform
  Foramen caecum
  Mucous follicles and epithelium of
  Filiform appendages of
  Gustatory region of
Teeth.  General structure of  .
  Dentine  .
  Modifications and tubes of  .
  Secondary formation of, in cavity of tooth
  Constitution of      .      •     •      •
  Ditto of inter-tubular substance, according to
    Nasmyth      .      •
  Ditto, according to Henle  .
  Peculiar globular formation in .
  Cementum   .       • .    •      •      •
  Bone cells, and Haversian canals of  .
  Hexagonal and granular layers of .
  Dentinal tubes in       •      •      •       •
  Cementum and dentine, modifications of each
    other      •
                                          PAGE
Teeth.  Enamel.  Fibres and cells of     .  338, 339
  Form and arrangement of ditto   .      .    339
  Pulp of tooth.  Structure of   .      .      .339
  Development of teeth.   General particulars of 339
  Formation of dentine and dentine pulp     . 341
  Membrane of ditto, Formation of enamel     342
  Enamel pulp.  Cells of .      .      .      .342
  Formation of cementum and cementum pulp  343
  Caries of the teeth     .... 344
  Tartar ou ditto      .      .".*.' 345
  To make sections of          .      .      . 345
Testis.  Structure, tubes, and cells of       .    483
Thoracic duct     .     .     .      .       ,68
  Fluid, red colour, and composition of    .     70
  Blood and granular corpuscles in    .      70,71
Thymus.  Follicles of .      .      .      .484
  Structure of     ....       485
  Limitary membrane and lobular arrangement 486
  Blood-vessels, and reservoir-of .     .      . 485
  Mucous membrane and capsule  of .      .    485
  Blood-vessels in, and milky fluid of follicles of 485
  Granular and nucleated cells of  .      .  73.485
Thyroid.  Vesicles of          .      .      .486
  Structure, lobules, and blood-vessels of  .    487
  Nuclei and cells of     ...      . 487
Todd and Bowman, Messrs.  On two forms of
     Haversian  canals ....     319
  Experiments ou bone cells, suggested by     322
  Their opinion that the nuclei of cartilage cells
     become developed into bone cells          328
  On the granular blastema in cancelli of bones  329
330
347
356
358
359
360
363
309
379
385
411
412
420
498
  On the nature of bone cells
  On the structure of white fibrous tissue
  On the muscular structure of the heart
  On " sarcous elements "
  On the nuclei of striated muscular fibre
  On the striated muscular fibre .
  On muscular contraction
  On the development of muscle
  On the neurolemma
  On the occurrence of gelatinous fibres in parts
    where their nervous character is indubitable 382
  On the termination of nerves in loops in the
    papillae of the skin and tongue  .
  On the epithelium of the stomach  cells
  On a modification of the follicles and stomach
    tubes near the pylorus
  Opinions as to the mucous glands
  On the termination of the nerve tubules in the
    papillae of the tongue
  On a fibrous structure in the papillae of tongue 498
  On the olfactory region    .      .      .    500
  On the olfactory filaments     .      .      . 508
  On the tubular structure of the cornea proper 512
  On the anterior elastic lamina of cornea  .    513
  On the membrana pupillaris  .      .      . 518
  On certain elastic fibres attached  to the  pos-
    terior elastic  lamina    .      .      .    518
  On the granular layer of the retina  .      . 519
  On a layer of cells situated on the hyaloid __
    membrane .
Tomes, Mr.   On the  development of bone
  His lectures on  teeth
  Description of granular layer of cementum
  On the development of dentine
  On the cells of the cementum pulp
  On the spaces  between the fibres of newly-
    formed enamel
  On tubes of carious dentine
Tongue.  Structure of. See  Taste
  Ditto of frog .      .      •      ■
Tonsillitic glands  .
Touch.  Seat of
  Papillae of      .
  Epidermis of .
  Distribution and arrangement of
  Structure and basement membrane of
  Nuclear contents of
  Blood-vessels of          •       ■
  Nerves of and fibres in
521
328
330
337
341
343

343
345
501
126
419
497
497
499
497
498
498
499
11)8 
560
INDEX,
Toynbee.  On the structure of Malpighian body 453
  On the corpus Malpighianum     .      .    453
  On the pathology of " Bright's disease "    . 455
Tracheal glands       .       .      .      .419
Tricho-monas     ..... 181
Troughs for dissection .       .                  36
Tube cells .      .     .      .      .      .54
Turpentine injections ....     42
Turpin.  His opinion that the milk globules con-
    sist of two vesicles  enclosing fine globules
    and buttery oil      ...      .  197
  His idea that the fungus, penicillum glaucum,
    was developed from the milk globules .    216

Urine.   Specific gravity of                     245
  Analysis of         .       .      .      .    240
  Solid organic constituents of, viz: mucous oor-
    puscles and epithelial scales    .      .    246
  Spermatozoa in  .     .      .      .      . 246
  Pathology of.....246
  To examine     ..... 252
Uterine glands .....    420
Uterine and Fallopian tubes    .     .   413.419
  Spheroidal epithelium of   .      .      .    413

Vaginal glands    ..... 420
Valentin's knife       ....     35
Valentin.  On quantity of blood in the system    80
  On the supposed stomach of spermatozoa     223
  On the spermatozoa of the bear      .      . 224
  On fhe development of spermatozoa     .    230
  On the ciliated epithelium of the ventricles    271
  On the occurrence of pigmentary  ramifica-
    tions in the cervical portion of pia mater    287
  On the  disposition of nucleated or gelatinous
    nerve fibres    ..... 381
  On the termination of nerves in pulp of teeth 385
  On the structure of the kidney    .      .    451
Valentin and Schwann.  Their researches on the
    development of muscular fibre     .      . 369
Valves in lymphatics ....     77
Veins,  injection of.     .      .      .      .40
Vibrious,  vaginal     ....    182
  Ditto venereal   ..... 194
Vicugna, blood of            .      .      .90
Villi.  Of the intestines, distribution of       . 493
  Structure and epithelium of      .      .    493
  Basement membrane and nuclear contents of  494
  Oil-drops in and blood-vessels of  .      •    494
  Lacteals and peculiar form of .      .      . 495
  Examination and injection of      .      .    496
  Of the pia mater       .... 538
Vision.  Structure of globe of the eye     .    509
  Sclerotic.  Structure of .      .      .      . 509
  Tunica albuginea and vessels  of   .      .    510
  Cornea.  Structure and laminae of   .      • 510
  Conjunctival epithelium and cornea proper    510
  Posterior and anterior elastic lamina  .      . 513
                                           PAGE
Vision.  Epithelium of aqueous humour   .    513
  Choroid.   Blood-vessels of     .      .   514,515
  Tunica Ruyschiana, venae vorticosae     .    515
  Stellate choroidal epethelium .      ,      .  515
  Lamina fusca       ....    516
  Hexagonal choroidal epithelium      .      .  516
  Tapetum lucidum   ....    516
  Ciliary and second ciliary processes   .      .  517
  Zone of Zinn, iris, and uvea      .      .    517
  Membrana pupilaris and retina       .      .  518
  Tunica Jacobi, granular and ganglionary layer  519
  Vesicular, fibrous gray, and vascular ditto  520,521
  Optic nerves, vitreous  body, vitreous humour  521
  Hyaloid membrane     ....  521
  Crystalline lens, capsule, body and fibres of    522
  Structure and arrangement of ditto   .      .  522
Vogel.  His opinion the mucous corpuscles are
    formed externally to the blood-vessels  .    177
  Ditto as  to  the nature of pus and  mucous
    globules      .....  184
  On the stellate bodies observed on decompos-
    ing fat  vesicles    ....    259
Volkman and Bidder. On the origin of gelatin-
    ous filaments from the  ganglia of the sym-
    pathetic       .      .      .      .      .382

Wagner.  On the blood  of the lamprey    .     91
  His belief in the existence of a nucleus in the
    red blood disc       .      .       .      .93
  His opinion  that the white  globules  are  red
    blood corpuscles in process of formation     112
  On the milk  globules   .      .       .      .200
  On the structure of human spermatozoa  .    224
  His supposition that the motions of spermato-
    zoa were produced by a ciliary apparatus   226
  His observation of spermatozoa in motion at
    the end of twenty-four hours    .      .    227
  On the development of spermatozoa  .      . 229
  On the  degeneration  of the testes of birds
    during  winter     ....    232
  On spermatozoa in male hybrids     .      . 232
  On the coloration of the iris of birds     .    255
  On the development of nerves       .      . 388
Waller, Dr. A.  On the tongue of the frog  .    126
Williams, Dr. T.   On the air cells of the lungs  396
Willis.   His translations of Wagner's Physi-
    ology     .....388
Wilson, Mr. Erasmus. On the anatomy of epi-
    dermis  .      .            .      .      .280
  On structure  of the striated muscular fibrilla  358
  Calculation of extent of sudoriferous system   438
Withoff.  On the number of hairs  existing on
    different surfaces of the body   .      .    300

Young.   His disbelief in the existence of a nu-
    cleus in the red blood disc  .      .      .93
Zinn, zone of
517
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