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of Medicine. 
A NEW, ENLARGED EDITION. JUST READY. 
Recommended as a Text-book at University of Pennsylvania, Long Lsland 
College Hospital, Yale and Harvard Colleges, Bishop's College, Montreal, 
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A HANDBOOK OF THE THEORY AND PRACTICE OF 
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A 
COMPEND 
OF 
Human Physiology. 
ESPECIALLY ADAPTED FOR THE USE OF 
MEDICAL STUDENTS. 
BY 
ALBERT A.M. M.D., 
Demonstrator of Physiology in the Jefferson Medical College; Member 
of the Pathological Society. 
SECOND EDITION, REVISED AND ENLARGED. 
OF PH YSIOLOGICAI^--'CONSTAJN'y$.v 
PHILADELPHIA : 
-y. 'WLA K ISTON, SON & CO., 
1012 Walnut Street. 
1884. Entered according to Act of Congress, in the year 1884, by 
P. BLAKISTON, SON & CO., 
In the Office of the Librarian of Congress, at Washington, D. C. 
PRESS OF WM. F. FELL & CO., 
1220-24 Sansom Street. TO MY FATHER, 
HENRY BRUBAKER, A.M., M.D., 
THIS LITTLE VOLUME 
IS AFFECTIONATELY INSCRIBED. PREFACE. 
This Compend of Physiology is the outgrowth of the author’s system of 
examinations in the Quiz room during a number of years, and was written 
at the request of medical students who desired a compact and convenient 
arrangement of the fundamental facts of human physiology. As most 
medical students enter upon the study of physiology before they have 
acquired a thorough knowledge of anatomy, it was thought desirable that 
such anatomical details should also be inserted as would be essential 
to a clear conception of the functions about to be studied. It was believed 
that it would be practically useful to students during their attendance upon 
lectures and in reviewing the subject prior to examinations. The fact 
that during the first year after its publication the first edition has been 
exhausted, proves that it has met the needs of students. 
In preparing a second edition the author has carefully revised the en- 
tire work, and inserted some fifteen pages of additional matter, which it is 
hoped will still further increase the usefulness of the book. 
To those teachers of physiology who have kindly noticed and recom- 
mended the Compend to their students I tender my thanks, and trust that 
in its improved condition it will continue to merit their approval. 
1210 Race Street. 
May 1st, 1884. 
ALBERT P. BRUBAKER. TABLE OF CONTENTS. 
PAGE 
Introduction 9 
Chemical Composition of the Body 10 
Structural Composition of the Body 14 
Food 17 
Digestion 21 
Absorption 28 
Blood 32 
Circulation of Blood 37 
Respiration 44 
Animal Heat 50 
Secretion 52 
Mammary Glands 54 
Vascular or Ductless Glands 56 
Excretion 58 
Kidneys 58 
Liver 63 
Skin 67 
Nervous System 70 
Spinal Nerves 72 
Properties and Functions of Nerves 74 
Cranial Nerves 77 
Spinal Cord 91 
Medulla Oblongata 98 
Pons Varolii 101 
Crura Cerebri 102 
Corpora Quadrigemina 102 
Corpora Striata and Optic Thalami 103 
VII VIII 
TABLE OF CONTENTS. 
PAGE 
Cerebellum 105 
Cerebrum 106 
Sympathetic Nervous System in 
Sense of Touch 114 
Sense of Taste 116 
Sense of Smell 117 
Sense of Sight 118 
Sense of Hearing 124 
Voice and Speech 128 
Reproduction 131 
Generative Organs of the Female 131 
Generative Organs of the Male •. 134 
Development of Accessory Structures 135 
Development of the Embryo 140 
Table of Physiological Constants 147 
Table showing Relation of Weights and Measures of the 
Metric System to Approximate Weights and Measures 
OF THE U. S 150 
Index 151 COMPEND 
OF 
HUMAN PHYSIOLOGY. 
Physiology, from tpbais, nature, and Xopos, a discourse, in its origi- 
nal application embraced the study of all natural objects, inorganic as well 
as organic. In its modern application physiology signifies the study of 
life; the investigation of the vital phenomena exhibited by all organic 
bodies, vegetable and animal. 
It may be divided into— 
1. Vegetable physiology, which treats of the phenomena manifested by 
the several structures of which the plant is composed. 
2. Animal physiology, which treats of the phenomena manifested by the 
organs and tissues of which the animal body is composed. 
Human Physiology is the study of the functions exhibited by the 
human body in a state of health. 
A Function is the action of an organ or tissue. 
The Functions of the Human Body may be classified into three 
groups, viz.:— 
1. Nutritive functions, which have for their object the preservation of 
the individual; e. g., digestion, absorption, circulation of the blood, 
respiration, assimilation, animal heat, secretion and excretion. 
2. Animal functions, which bring the individual into conscious relation- 
ship with external nature; e. g., sensation, motion, language, mental 
and moral manifestations. 
3. Reproductive function, which has for its object the preservation of 
the species. 
The facts of human physiology have been determined by means of 
anatomy, chemistry, pathology, comparative anatomy, vivisection, the 
application of physics, etc. 
The Body may be studied from a chemical and structural point of view. 
9 10 
HUMAN PHYSIOLOGY. 
CHEMICAL COMPOSITION OF THE HUMAN 
BODY. 
composition of the body, in the following proportions:— 
Of the Sixty-four Chemical Elements, about sixteen enter into the 
Oxygen 72.00 
Hydrogen 9.10 
Nitrogen 2.50 
Carbon 13.50 
O. H. and C. are found in all the tissues and 
fluids of the body, without exception. 
O. H. C. and N. found in most of the fluids 
and all tissues except fat. 
Sulphur 147 In fibrin, casein, albumen, gelatin; as potas- 
sium sulpho-cyanide in saliva; as alkaline 
sulphate in urine and sweat. 
Phosphorus 1.15 In fibrin and albumen; in brain; as tri-sodium 
phosphate in blood and saliva, etc. 
Calcium 1.30 As calcium phosphate in lymph, chyle, blood, 
saliva, bones and teeth. 
Sodium 10 As sodium chloride in all fluids and solids of 
the body, except enamel; as sodium sul- 
phate and phosphate in blood and muscles. 
Potassium 026 As potassium chloride in muscles; generally 
found with sodium as sulphates and phos- 
phates. 
Magnesium 001 Generally in association with calcium, as phos- 
phate, in bones. 
Chlorine 085 In combination with sodium, potassium and 
other bases, in all the fluids and solids. 
Fluorine 08 As calcium fluoride in bones, teeth and urine. 
Iron 01 In blood globules; as peroxide in muscles. 
Silicon a trace In blood, bones and hair. 
Manganesium, a trace Probably in hair, bones and nails. 
Of the four chief elements which together make up 97 per cent, of the 
body, O. H. N. are eminently mobile, elastic, and possess great atomic heat. 
C. H. N. are distinguished for the narrow range and feebleness of their 
affinities and chemical inertia. C. has the greatest atomic cohesion. O. 
is noted for the number and intensity of its combinations, and its remark- 
able display of chemical activity. 
Chemical Elements do not exist alone in the body, but are combined 
in characteristic proportions to form compounds, the proximate principles, 
which are the ultimate compounds to which the fluids and solids can be 
reduced. CHEMICAL COMPOSITION OF THE HUMAN BODY. 
11 
Proximate Principles exist in the body under their own form, and can 
be extracted without losing their distinctive properties. 
There are about one hundred proximate principles, which are divided 
into four classes, viz: inorganic, organic, non-nitrogenized, organic nitro- 
genized, and principles of waste. 
SUBSTANCE. WHERE FOUND. 
Oxygen Lungs and blood. 
Hydrogen Stomach and intestines. 
Nitrogen Blood and intestines. 
Carbonic anhydride Expired air of lungs. 
I. INORGANIC PROXIMATE PRINCIPLES. 
Carburetted hydrogen 
Sulphuretted hydrogen 
Lungs and intestines. 
Water Found in all solids and fluids. 
Sodium chloride In all fluids and solids except enamel. 
Potassium chloride In muscles, liver, saliva, gastric juice, etc. 
Ammonium chloride Gastric juice, saliva, tears, urine. 
Calcium chloride Bones, teeth, urine. 
Calcium carbonate Bones, teeth, cartilage, internal ear, blood. 
Calcium phosphate 
Magnesium phosphate 
Sodium phosphate 
Potassium phosphate 
In all fluids and solids of the body. 
Sodium sulphate 
Potassium sulphate 
Universal,except milk,bile and gastric juice. 
Sodium carbonate 
Potassium carbonate 
Blood, bones, lymph, urine, etc. 
Magnesium carbonate Blood and sebaceous matter. 
Inorganic principles enter and leave the body under their own form. 
Water gives elasticity to the tissues and is a general solvent. Sodium 
chloride regulates osmotic action (exudation and absorption), influences 
the form and consistence of blood corpuscles. Calcium phosphate gives 
solidity and resistance to bones. 
II. ORGANIC NON-NITROGENIZED PRINCIPLES. 
Palmitin, 
Stearin, 
Olein, 
PATS. c. o. H. 
Palmitic acid, 
Stearic acid, 
Oleic acid, 
Neutral Fats. 
- Fatty Acids. 
The Neutral fats, when combined in proper proportions, constitute a 
large part of the fatty tissue of the body; they are soluble in ether, chloro- 12 
HUMAN PHYSIOLOGY. 
form and hot alcohol; insoluble in cold alcohol and water, and liquefy at a 
high temperature; by boiling with a caustic alkali they are decomposed 
into glycerine and fatty acids. 
The Fatty acids combined with sodium, potassium and calcium, are found 
as salts in various fluids of the body, such as blood, chyle, fseces, etc. 
Phosphorized fats in nervous tissue, butyric acid in milk, propionic acid in 
sweat, are also constituents of the body. 
Fat is derived from the food, stored up in the form of vesicles in and 
around the various anatomical structures and beneath the skin, constituting 
the adipose tissue; it serves as a non-conductor of heat, and gives round- 
ness and form to the body. During the process of nutrition fat undergoes 
oxidation, which is attended by the evolution of heat and the manifestation 
of muscular and nervous force. 
SUGARS. C.O. H. 
Glycogen, or Amyloid substance. 
Lactose, or Milk sugar. 
Dextrose, or Grape sugar. 
Inosite, or Muscle sugar. 
Dextrine. 
Sugar is found in many of the tissues and fluids of the body, e. g., liver, 
placenta, blood, milk, muscles, etc. The varieties of sugar are soluble in 
water, assume the crystalline form upon evaporation, and are converted 
into alcohol and carbonic anhydride by fermentation. Sugar is derived 
from the food, is absorbed into the blood, where it largely disappears, 
undergoing a transformation into fat; or it is directly oxidized and con- 
tributes, like the fats, to the production of heat and force. 
III. ORGANIC NITROGENIZED PRINCIPLES. 
ALBUMENS. C. O. H. N. S. P. 
Albumen. 
Albuminose. 
Fibrin. 
Casein. 
Ostein. 
Myosin. 
Protagon. 
Pepsin. 
Pancreatin. 
Salivin. 
Mucin. 
Chondrin. 
Elastin. 
Keratin. 
Globulin. 
The Albuminous compounds are organic in their origin, being derived 
from the animal and vegetable world; they are taken into the body as 
food, appropriated by the tissues, and constitute their organic basis; they 
differ from the non-nitrogenized substances in not being crystalline, but 
amorphous, in having a more complex but just as definite composition, and 
containing in addition to C. O. H., nitrogen, with, at times, sulphur and CHEMICAL COMPOSITION OF THE HUMAN BODY. 
13 
phosphorus. The albumens possess characteristics which distinguish them 
from all other substances: viz., a molecular mobility, which permits 
isomeric modifications to take place with great facility. Under favorable 
conditions they promote chemical changes, by their presence (catalysis) in 
other substances: e. g., during digestion, salivin and pepsin cause starch 
and albumen to be transformed into sugar and albuminose respectively. 
Different albumens possess varying proportions of water, which they lose 
when subjected to desiccation, becoming solid; but upon exposure to 
moisture they again absorb water, regaining their original condition—they 
are hygroscopic. Another property is that of coagulation, which takes 
place under certain conditions: e. g., the presence of mineral acids, heat, 
alcohol, etc. 
After death the albuminous compounds undergo putrefactive changes, 
giving rise to carburetted and sulphuretted hydrogen and other gases. 
Albumen exists in the blood, lymph, chyle, constituting the pabulum of 
the tissues; it is coagulated by heat, mineral acids and alcohol. 
Peptones are formed in the stomach from the digestion of albuminous 
principles of the food; they are coagulated by tannic acid, chlorine, acetate 
of lead, and characterized by great diffusibility, which permits them to pass 
through animal membranes with facility. 
Fibrin can be obtained from freshly drawn blood by whipping; it also 
coagulates spontaneously, and when examined microscopically exhibits a 
filamentous structure. 
Casein is the albuminous principle of milk. 
Ostein constitutes the organic basis of bone, with which are mingled the 
salts of lime. 
Myosin is found in muscles, protagon in brain, pepsin, pancreatin and 
salivin, in the digestive fluids. 
Mucin, chondrin, elastin, keratin and globulin, are found in mucus, 
cartilage, elastic tissues, hair, nails, and red corpuscles, respectively. 
As the properties of the compounds formed by the union of elements 
are the resultants of the properties of the elements themselves, it follows 
that the ternary substances, sugars, starches and fats, possess a great 
inertia and notable instability; while in the more complex albuminous 
compounds, in which sulphur and phosphorus are united to the four 
chief elements, molecular mobility, resulting in isomerism, exists in 
a high degree. As these compounds are unstable, of a great molecular 
mobility, they are well fitted to take part in the composition of organic 
bodies, in which there is a continual movement of composition and 
decomposition. 14 
HUMAN PHYSIOLOGY. 
IV. PRINCIPLES OF WASTE. 
Urea. Xanthin. Sodium, 
Creatin. Tyrosin. Potassium, 
Creatinin. Hippuric Acid. Ammonium, 
Cholesterin. Calcium Oxalate. Calcium, 
Urates. 
These principles, which represent waste, are of organic origin, arising 
within the body as products of disassimilation or retrograde metamorphosis 
of the tissues; they are absorbed by the blood, carried to the various excre- 
tory organs, and by them eliminated from the body. 
The excrementitious substances will be fully considered under excretion. 
Proximate Quantity of the Chemical Elements and Proximate 
Principles of Body Weighing 154 lbs. 
Oxygen 
lbs. 
oz. 
Hydrogen 
Nitrogen 
3 
8 
Carbon., 
21 
Calcium 
Phosphorus 
I 
12 
Sodium, etc 
12 
154 
ti 
Water 
lbs. 
OZ. 
Albuminoids 
... 23 
7 
Fats 
... 12 
.. 
Calcium phosphate 
- 5 
13 
Calcium carbonate 
Calcium fluoride 
3 
Sodium sulphate, etc... 
9 
154 
„ 
STRUCTURAL COMPOSITION of THE BODY. 
The Study of the Structure of the body reveals that it is composed 
of dissimilar parts, e. g., bones, muscles, nerves, lungs, etc.; while these, 
again, by closer examination, can be resolved into elementary structures, 
the tissues, e. g., connective tissue, muscular, nervous, epithelial tissue, etc. 
Microscopical examination of the tissues shows that they are com- 
posed of fundamental structural elements, termed cells. 
Cells are living physiological units; the simplest structural forms 
capable of manifesting the phenomena of life. 
Cells vary in their anatomical constitution in the different structures of 
the body, and may be classed in three groups, viz.: I. Cells possessing a 
distinct cell wall, cell substance and a nucleus. 2. Cells possessing a cell 
substance and a nucleus. 3. Cells possessing the cell substance only. 
They vary in size from the to the of an inch in diameter; 
when young and free to move in a fluid medium they assume the spherical STRUCTURAL COMPOSITION OF THE BODY. 
15 
form; but when subjected to pressure, may become flattened, cylindrical, 
fusiform or stellate. 
Structure of cells. The cell wall is not an essential structure, as many 
cells are entirely devoid of it. It is a thin, structureless, transparent 
membrane, permeable to fluids. 
The Cell Substance in young cells is a soft, \gscid, albuminous matter, 
unstable, insoluble in water, and known as protoplasm, bioplasm, sarcode, 
etc.; in older cells the original cell substance undergoes various trans- 
formations, and is partly replaced by fat globules, pigment and crystals. 
The Nucleus is a small vesicular body in the interior of the cell sub- 
stance, and frequently contains smaller bodies, the micleoli. 
MANIFESTATIONS OF CELL LIFE. 
Growth. Cells when newly formed are exceedingly small, but as they 
approach maturity they increase in size, by the capability which the cells 
possess of selecting and appropriating new material as food, vitalizing and 
organizing it. The extent of cell growth varies in different tissues; in 
some the cells remain exceedingly small, in others they attain considerable 
size. In many instances the cell substance undergoes transformation into 
new compounds destined for some ulterior purpose. 
Reproduction. Like all organic structures cells have a limited period 
of life; their continual decay and death necessitates a capability of repro- 
duction. Cells reproduce themselves in the higher animals mainly by 
fission. This is seen in the white blood corpuscles of the young embryos 
of animals; the corpuscle here consists of a cell substance and nucleus. 
When division of the cell is about to take place, the nucleus elongates, 
the cell substance assumes the oval form, a constriction occurs, which 
gradually deepens, until the original cell is completely divided and 
two new cells are formed, each of which soon grows to the size of the 
parent cell. 
In cells provided with a cell membrane the process is somewhat different. 
In the ova of the inferior animals, after fertilization has taken place, a 
furrow appears on the opposite sides of the cell substance, which deepens 
until the cell is divided into two equal halves, each containing a nucleus; 
this process is again repeated until there are four cells, then eight, and so 
on until the entire cell substance is divided into a mulberry mass of cells, 
completely occupying the interior of the cell membrane. The whole 
process of segmentation takes place with great rapidity, occupying not 
more than a few minutes, in all probability. 16 
HUMAN PHYSIOLOGY. 
Motion. Spontaneous movement lias been observed in many of the 
cells of the body. It may be studied, for example, in the movements of 
the spermatozoa, the waving of the cilia covering the cells of the bronchial 
mucous membrane, the white corpuscles of the blood, etc. 
By a combination and transformation of these original structural elements, 
and material derived from them, all the tissues are formed which enter into 
the structure of the humSn body. 
CLASSIFICATION OF TISSUES. 
I. Homogeneous Substance, a more or less solid, albuminous struc- 
ture, filling the spaces between the cells and fibres of various tissues, e. g., 
cartilage, bone, dentine, etc. 
II. Limiting Membrane, a thin, homogeneous membrane, structure- 
less, composed of coagulated albumen, and often not more than the 
of an inch in thickness, found lining the blood vessels and lymph- 
atics, forming the basement membrane of the skin and mucous mem- 
branes, the posterior layer of the cornea, the capsule of the crystalline 
lens, etc. 
III. Simple fibrous or filamentous tissue—the elements of which 
are real or apparent filaments. 
(a) Connective or areolar; white fibrous tissue; constituting tendons, 
ligaments, aponeuroses, periosteum, dura mater, synovial membranes, vas- 
cular tunics, etc. 
(b) Yellow elastic tissue, found in the middle coats of arteries, veins, 
lymphatics, ligamentum nuchse, vocal cords, ligamenta subflava, etc. 
IV. Compound membranes (membrano-cellular or fibro-cellular 
tissues), cells aggregated into laminae. 
(a) Epidermic tissue; (b) epithelial tissue; (c) glandular tissue; 
(d) cornea. 
V. Cells containing coloring matter, or pigment cells, e. g., skin, 
choroid membrane, etc. 
VI. Cells coalesced or consolidated by internal deposits, e. g., 
hair, nails, bone, teeth, etc. 
VII. Cells imbedded in an intercellular substance, e. g., cartilage, 
crystalline lens, etc. 
VIII. Cells aggregated in clusters, forming tissues more or less 
solid, e. g., adipose tissue, lymphatic glands. 
IX. Cells imbedded in a matrix of capillaries, e. g., gray or vesicular 
nervous matter. FOOD. 
17 
X. Cells whose coalesced cavities form tubes containing liquids or 
secondary solid deposits, e. g., vascular tissue, dentine. 
XI. Cells free, isolated, or floating—fluid tissue—e. g., red and white 
blood corpuscles, lymph and chyle corpuscles. 
A Food may be defined to be any substance capable of playing a part 
in the nutrition of the body. 
Food is required for the repair of the waste of the tissues consequent 
on their functional activity, for the generation of heat and the evolution of 
force. 
Hunger and Thirst are sensations which indicate the necessity for 
taking food; they arise in the tissues at large, and are referred to the 
stomach and fauces, respectively, through the sympathetic nervous system. 
Inanition or Starvation results from an insufficiency or absence of 
food, the physiological effects of which are hunger, intense thirst, intestinal 
uneasiness, weakness and emaciation; the quantity of carbonic acid 
exhaled diminishes and the urine is lessened in amount; the volume of the 
blood diminishes; a fetid odor is exhaled from the body; vertigo, stupor 
followed by delirium, and at times convulsions, result from a disturbance 
of the nerve centres; a marked fall of the bodily temperature occurs, from 
a diminished activity of the nutritive process. Death usually takes place, 
from exhaustion. 
During starvation the loss of different tissues, before death occurs, aver- 
ages or 40 per cent, of their weight. 
Those tissues which lose more than 40 per cent, are fat, 93.3; blood, 75 ; 
spleen, 71.4; pancreas,64.1; liver, 52; heart,44.8; intestines, 42.4; muscles, 
42.3. Those which lose less than 40 per cent, are the muscular coat of the 
stomach, 39.7; pharynx and oesophagus, 34.2; skin, 33.3; kidneys, 31.9; 
respiratory apparatus, 22.2; bones, 16.7; eyes, 10; nervous system, 1.9. 
The Fat entirely disappears, with the exception of a small quantity which 
remains in the posterior portion of the orbits and around the kidneys. The 
Blood diminishes in volume and loses its nutritive properties. The Muscles 
undergo a marked diminution in volume and become soft and flabby. 
The Nervous system is last to suffer, not more than two per cent, dis- 
appearing before death occurs. 
The appearances presented by the body after death from starvation are 
those of anaemia and great emaciation; almost total absence of fat; blood- 
lessness ; a diminution in the volume of the organs; an empty condition 
FOOD. 18 
HUMAN PHYSIOLOGY. 
of the stomach and bowels, the coats of which are thin and transparent. 
There is a marked disposition of the body to undergo decomposition, 
giving rise to a very fetid odor. 
The duration of life after a complete deprivation of food varies from 
eight to thirteen days, though life can be maintained much longer if a 
quantity of water be obtained. The water is more essential under these 
circumstances than the solid matters, which can be supplied by the 
organism itself. 
The different alimentary principles which are appropriated by the 
system are combined in different proportions in the various articles of 
food, and are separated from the innutritious substances during the process 
of digestion. They belong to the organic and inorganic worlds, and may 
be classified, according to their chemical composition, as follows :— 
1. Albuminous group—nitrogenized, C. O. H. N. S. P. 
PRINCIPLE. WHERE FOUND. 
Myosin, syntonin Flesh of animals. 
Vitellin, albumen Yolk of egg, white of egg. 
Fibrin, globulin Blood contained in meat. 
Casein Milk, cheese. 
Gluten Grain of wheat and other cereals. 
Vegetable albumen Soft growing vegetables. 
Legumin Peas, beans, lentils, etc. 
Gelatin Bones. 
2. Saccharine group—non-nitrogenized, C. O. H. 
Cane sugar beet root sugar Sugar cane, beets, etc. 
Glucose, grape sugar Fruits. 
Inosite, liver sugar, glycogen Muscles, liver, etc. 
Lactose or milk sugar Milk. 
Starch Cereals, tuberous roots and legu - 
minous plants. 
CLASSIFICATION OF ALIMENTARY PRINCIPLES. 
3. Oleaginous group—non-nitrogenized, C. O. H. 
Animal fats and oils... 
Stearin, olein 
Palmatin, fatty acids.. 
Found in the adipose tissue of 
animals, seeds, grains, nuts, fruits, 
and other vegetable tissues. 
4- Inorganic group. Water, sodium and potassium chlorides, sodium, 
calcium, magnesium and potassium phosphates, calcium carbonate and 
iron. FOOD. 
19 
5. Vegetable acid group. Malic, citric, tartaric and other acids, 
found principally in fruits. 
6. Accessory foods. Tea, coffee, alcohol, cocoa, etc. 
The Albuminous principles enter largely into the composition of the 
body, and constitute the organic bases of the different tissues; they are 
mainly required for the growth and repair of the tissues, but when oxidized 
give rise, to some extent, to the evolution of heat and force. Muscular 
work, however, does not result from a destruction of the albuminous com- 
pounds. The oxidation of the carbonaceous compounds, sugars and oils, 
furnishing the force which is transformed by the muscular system into 
motor power. When employed exclusively as food for any length of time 
the albuminous substances are incapable of supporting life. 
The Saccharine principles are important to the process of nutrition, but 
the changes which they undergo are not fully understood ; they form but a 
small proportion of the animal tissues, and by oxidation generate heat and 
force. Starch undergoes conversion into dextrin and grape sugar. 
The Oleaginous principles form a large part of the tissues of the body. 
They are introduced into the system as food, and are formed also from a 
transformation of saccharine and albuminous matter during the nutritive 
process; they enter into the composition of nervous and muscular tissue, 
and are stored up as adipose tissue in the visceral cavities and subcutaneous 
connective tissue, thus giving roundness to the form and preventing, to 
some extent, the radiation of heat. While they aid in the reconstruction 
of tissue, they mainly undergo oxidation, giving rise to the production of 
heat and the evolution of muscular and nervous force. 
The Inorganic principles constitute an essential part of all animal tissues, 
and are introduced with the food. 
Water is present in all fluids and solids of the body, holding their 
ingredients in solution, promoting the absorption of new material into the 
blood and tissues, and the removal of waste ingredients. 
Sodium chloride is an essential constituent of all tissues, regulating the 
passage of fluids through animal membranes (endosmosis and exosmosis). 
Calcium■ phosphate gives solidity to bones and teeth, constituting more 
than one-half their substance. 
Iron is a constituent of the coloring matter of the blood. 
The Vegetable acids are important to nutrition, and tend to prevent the 
scorbutic diathesis. 
The Accessory foods also influence the process of nutrition. Tea excites 
the respiratory function, increasing the evolution of carbonic acid. Coffee 
is a stimulant to the nervous system; increases the force of the heart’s 
action, increases the arterial tension and retards waste. 20 
HUMAN PHYSIOLOGY. 
Alcohol, when introduced into the system in small quantities, under- 
goes oxidation and contributes to the production of force, and is thus 
far a food. It excites the gastric glands to increased secretion, improves 
the digestion, accelerates the action of the heart and stimulates the 
activities of the nervous centres. In zymotic diseases, and all cases of 
depression of the vital powers, it is most useful as a restorative agent. 
When taken in excessive quantities, it is eliminated by the lungs and 
kidneys. The metamorphosis of the tissues is retarded, the elimination of 
urea and carbonic acid is lessened, the temperature lowered, the mus- 
cular powers impaired and the resistance to depressing external influences 
diminished. When taken through a long period of time, alcohol impairs 
digestion, produces gastric catarrh, disorders the secreting power of the 
hepatic cells. It also diminishes the muscular power and destroys the 
structure and composition of the cells of the brain and spinal cord. The 
connective tissue of the body increases in amount, and subsequently con- 
tracting, gives rise to sclerosis. 
A proper combination of different alimentary principles is essential 
for healthy nutrition; no one class being capable of maintaining life for 
any definite length of time. 
The Albuminous food in excess promotes the arthritic diathesis, mani- 
festing itself as gout, gravel, etc. 
The Oleaginous food in excess gives rise to the bilious diathesis, while 
a deficiency of it promotes the scrofulous. 
The Farinaceous food, when long continued in excess, favors the rheu- 
matic diathesis by the development of lactic acid. 
The Alimentary Principles are not introduced into the body as such, 
but are combined in proper proportions to form compound substances, 
termed foods, e. g., bread, milk, eggs, meat, etc., the nutritive value of 
each depending upon the extent to which these principles exist. 
WATER. 
ALBUMEN. 
STARCH. 
SUGAR. 
FATS. 
Bread 
37 
8.1 
47-4 
3-6 
1.6 
2-3 
Milk 
86 
4.1 
5-2 
3-9 
0.8 
Eggs 
14.0 
10.5 
1.5 
Meat 
54 
27.6 
15-45 
2-95 
Potatoes 
75 
2.1 
18.8 
3-2 
0.2 
0.7 
Corn 
H 
11.1 
64.7 
0.4 
8.1 
1.7 
Oatmeal 
i5 
12.6 
58.4 
5-4 
5-6 
3 
Turnips 
9i 
1.2 
5-i 
2.1 
6 
Carrots 
83 
i-3 
8.4 
6.1 
0.2 
1.0 
Rice 
6-3 
79.1 
0.4 
0.7 
°-5 
PERCENTAGE COMPOSITION OF DIFFERENT FOODS. DIGESTION. 
21 
The Amount of food required in 24 hours has been estimated at about 
pounds, comprising meat, 16 oz.; bread, 19 oz.; fat, oz.; water, 
52 fluid oz. 
In the excreta of the body the normal proportion of nitrogen to carbon 
is I to 15. To maintain this relation, a proper proportion of nitrogenized 
to carbonaceous food should be observed in diet. The proportion in the 
excreta would be— 
On a meat diet nitrogen i to carbon 3 
On a bread diet “ 1 “ 30 
On a mixed diet “ 2 “ 33 
Or “ 1 “ 16 
The amount of nitrogen and carbon necessary to compensate for the 
loss would be contained in 16 oz. of meat and 2 lbs. of bread; as, however, 
usually 3 oz. of oil are consumed in 24 hours, only 19 oz. of bread are 
required. 
COMPARISON OF INGESTA AND EGESTA IN 24 HOURS 
FOOD, DRINK, AIR. OZ. 
Albumen 4.23 
Starch 11.63 
Fats 3.17 
Salts 1.13 
Water (6 pints) 93.00 
Oxygen 26.24 
Breath 
EXCRETIONS. OZ. 
carbonic acid' 
watery vapor 
43-4° 
Perspiration 
carbonic acid 
watery vapor 
► 23.62 
Urine 66.31 
Solid excreta 6.07 
Total 139-4° 
Total 139-4° 
DIGESTION. 
Digestion is a physical and chemical process, by which the food is 
changed by the action of solvent fluids into a form capable of being 
absorbed into the blood. 
The Digestive Apparatus consists of the alimentary canal and its 
appendages, viz: teeth, salivary, gastric and intestinal glands, liver and 
pancreas. 
Digestion may be divided into seven stages; prehension, mastication, 
insalivation, deglutition, gastric and intestinal digestion and defecation. 
Prehension, the act of conveying food into the mouth, is accomplished 
by the hands, lips and teeth. 22 
HUMAN PHYSIOLOGY. 
Mastication is the trituration of the food, and is accomplished by the 
teeth and lower jaw, under the influence of muscular contraction. When 
thoroughly divided, the food presents a greater surface for the solvent 
action of the digestive fluids, thus aiding the general process of digestion. 
The Teeth are thirty-two in number, sixteen in each jaw, and divided 
into four incisors or cutting teeth, two canines, four bicuspids, and six molars 
or grinding teeth; each tooth consists of a crown covered by enamel, a 
neck, and a root surrounded by the crusta petrosa, and imbedded in the 
alveolar process; a section through a tooth shows that its substance is 
made up of dentine, in the centre of which is the pulp cavity, containing 
blood vessels and nerves. 
The lo7ver jaw is capable of making a downward and an upward, a 
lateral and an antero-posterior movement, dependent upon the construc- 
tion of the temporo-maxillary articulation. 
The jaw is depressed by the contraction of the digastric, genio hyoid, 
mylo-hyoid and platysma myoides muscles; elevated by the temporal, masseter 
and internal pterygoid muscles; moved laterally by the alternate contrac- 
tion of the external pterygoid muscles; moved anteriorly by the pterygoid 
and posteriorly by the united actions of the genio-hyoid, mylo-hyoid and 
posterior fibres of the temporal muscle. 
The food is kept between the teeth by the intrinsic and extrinsic mus- 
cles of the tongue from within, and the orbicularis oris and buccinator 
muscles from without. 
The Movements of Mastication are called forth by reflex action 
through the medulla oblongata, induced by the presence of food in the 
mouth. 
NERVOUS CIRCLE OF MASTICATION. 
AFFERENT OR EXCITOR NERVES. 
1. Lingual branch of 5th pair. 
2. Glosso-pharyngeal. 
EFFERENT OR MOTOR. 
1. 3d branch of 5th pair. 
2. Hypo-glossal. 
3. Facial. 
Insalivation is the incorporation of the food with the saliva secreted 
by the parotid, sub-?naxillary and sub-lingual glands; the parotid saliva, 
thin and watery, is poured into the mouth through Steno’s duct; the sub- 
maxillary and sub-lingual salivas, thick and viscid, are poured into the 
mouth through Wharton’s and Bartholini’s ducts. 
Saliva is an opalescent, slightly viscid, alkaline fluid, having a specific 
gravity of 1.005. Microscopical examination reveals the presence of 
salivary corpuscles and epithelial cells. Chemically it is composed of DIGESTION. 
23 
water, proteid matter, a ferment (ptyalin) and inorganic salts. The 
amount secreted in 24 hours is about 2J4 lbs. Its function is twofold:— 
1. Physical.—Softens and moistens the food; glues it together, and 
facilitates swallowing. 
2. Chemical.—Converts starch into grape sugar. This action is due to 
the presence of the organic ferment, ptyalin. The change consists in the 
assumption of a molecule of water. 
Starch. 
c6h10o8 + h2 o = c6h12o6 
Water. 
Grape sugar. 
NERVOUS CIRCLE OF INSALIVATION. 
1. Lingual Branch of 5th pair. 
2. Glosso-pharyngeal. 
AFFERENT OR EXCITOR NERVES. EFFERENT OR MOTOR NERVES. 
1. Auriculo-temporal branch of 5th 
pair, for parotid gland. 
2. Chorda tympani, for sub-maxil- 
lary and sub-lingual glands. 
The centres regulating the secretion are two, viz.: The medulla oblon- 
gata and the sub-maxillary ganglion of the sympathetic; the latter 
acting antagonistically to the former. Impressions excited by the food 
in the mouth reach the medulla oblongata through the afferent nerves; 
motor impulses are there generated which pass outward through the 
efferent nerves. 
Stimulation of the auriculo-temporal branch increases the flow of 
saliva from the parotid gland; division arrests it. 
Stimulation of the chorda tympani is followed by a dilation of the blood 
vessels of the sub-maxillary glands, increased flow of blood (thus act- 
ing as a vaso dilator nerve) and an abundant discharge of a thin saliva; 
division of the nerve arrests the secretion. 
Stimulation of the cervical sympathetic is followed by a contraction of 
the blood vessels, diminishing the flow of blood (thus acting as a vaso- 
constrictor nerve) and a diminution of the secretion, which now becomes 
thick and viscid; division of the sympathetic does not, however, com- 
pletely dilate the vessels. There is evidence of the existence of a local 
vaso-motor mechanism, which is inhibited by the chorda tympani; exalted 
by the sympathetic. 
Deglutition is the act of transferring food from the mouth into the 
stomach, and may be divided into three stages:— 
1. The passage of the bolus from the mouth into the pharynx. 
2. From the pharynx into the oesophagus. 
3. From the oesophagus into the stomach. 24 
HUMAN PHYSIOLOGY. 
In the ist stage, which is entirely voluntary, the mouth is closed and 
respiration momentarily suspended; the tongue, placed against the roof of 
the mouth, arches upward and backward, and forces the bolus into the 
fauces. 
In the 2d stage, which is entirely reflex, the palate is made tense and 
directed upward and backward by the levatores-palati and tensores-palati 
muscles; the bolus is grasped by the superior constrictor muscle of the 
pharynx and rapidly forced into the oesophagus. 
The food is prevented from entering the posterior nares by the uvula 
and the closure of the posterior half-arches (the palato-pharyngei muscles); 
from entering the larynx by its ascent under the base of the tongue and 
the action of the epiglottis. 
In the jd stage the longitudinal and circular muscular fibres, contract- 
ing from above downward, strip the bolus into the stomach. [For nervous 
mechanism of Deglutition see Medulla Oblongata.] 
Gastric Digestion. The stomach is a dilatation of the alimentary 
canal, 13 inches long, 5 inches deep, having a capacity of about 5 pints; 
there can be distinguished a cardiac and pyloric orifice, a greater and 
lesser curvature, a greater and lesser pouch. 
It possesses three coats:— 
1. Serous, a reflection of the peritoneum. 
2. Muscular, the fibres of which are arranged longitudinally, trans- 
versely and obliquely. 
3. Mucous, thrown into folds, forming the rugae; imbedded in the 
mucous coat are immense numbers of mucous and true gastric glands ; the 
former, found in the pyloric portion, are lined by columnar epithelium 
throughout their depth; the latter, the true peptic cells, are found in the 
cardiac end, and mainly contain oval, spherical cells, which are granular 
and nucleated. 
During the intervals of digestion the mucous membrane of the stomach 
is pale and covered with a layer of mucus. Upon the introduction of 
food the blood vessels dilate and become filled with blood, and the 
mucous membrane becomes red. At the same time small drops of a fluid, 
the gastric juice, begin to exude upon its surface, which gradually run 
together and trickle down the sides of the stomach. 
The Gastric Juice is a secretion of the true peptic cells, and when 
obtained from the stomach through a fistulous opening, is a clear, 
straw-colored fluid, decidedly acid, with a specific gravity of 1.005 to 
I.OIO. DIGESTION. 
25 
COMPOSITION OF GASTRIC JUICE. 
Water 975.00 
Pepsin 15.00 
Hydrochloric acid 4.78 
Inorganic salts 5.22 
1000.00 
The water forms the large part of the fluid, and holds in solution the 
other ingredients. It results from a transudation from the blood vessels 
under the increased blood supply. Of the inorganic salts the chlorides of 
sodium and potassium are the most abundant. 
Pepsin is the organic nitrogenized ferment of the gastric juice, and is 
formed, during the intervals of digestion, by the peptic cells. In the pres- 
ence of a small per cent, of an acid, it acquires the property of converting 
the albumen of the food into albuminose or peptones. 
Hydrochloric acid is present in small quantity, and gives the juice 
its acidity. In all probability, its production is due to the activity of the 
peptic cells. 
These two characteristic ingredients of the gastric juice exist in a state 
of combination as hydrochloro-peptic acid, and the presence of both is 
absolutely essential for the complete digestion of the food. When the food 
enters the stomach it is subjected to the peristaltic action of the muscular 
coat, and thoroughly incorporated with the gastric juice. This fluid pos- 
sesses the property of attacking the connective tissues of the food, disin- 
tegrating it and dissolving out the alimentary principles. 
The Principal Action of the gastric juice, however, is to transform 
the different albuminous principles of the food into peptones or albuminose. 
Before digestion they are insoluble in water and incapable of being 
absorbed. After digestion they become soluble and are readily absorbed. 
Peptones differ from the albumins in being— 
1. Diffusible, passing rapidly through the mucous membrane and walls 
of the blood vessels. 
2. Non-coagulable by heat, nitric or acetic acids; but are readily 
precipitated by tannic acid. 
3. Soluble in water and saline solutions. 
4. Assimilable by the blood; when injected into it they do not reappear 
in the urine. 
Gastric juice exerts no influence either upon grape sugar, cane sugar, 
starch or fat. 26 
HUMAN PHYSIOLOGY. 
Gastric Digestion occupies on the average from 3 to 5 hours, but 
varies in duration according to the nature and quantity of the food, exercise, 
temperature, etc. 
The Amount of gastric juice secreted in 24 hours varies, under normal 
conditions, from 8 to 14 pounds. 
Movements of the Stomach. As soon as digestion commences, the 
cardiac and pyloric orifices are closed; the walls of the stomach contract 
upon the food, and a peristaltic action begins, which carries the food along 
the greater and lesser curvatures, and thoroughly incorporates it with the 
gastric juice. As soon as any portion of the food is digested it passes 
through'the pylorus into the intestine. 
Intestinal Digestion. The intestine is about 20 feet long, inches 
in diameter, and possesses three coats:— 
1. Serous (peritoneal). 
2. Muscular, the fibres of which are arranged longitudinally and trans- 
versely. 
3. Mucous, thrown into folds, forming the valvulce conniventes. 
This stage of digestion is probably the most complex and important; 
here the different alimentary principles are further elaborated and prepared 
for absorption into the blood by being acted upon by the intestinal juices 
pancreatic juice and bile. 
Throughout the mucous coat are imbedded the intestinal follicles, the 
glands of Brunner and Lieberkiihn. They secrete the true intestinal juice, 
which is an alkaline, viscid fluid, composed of water, organic matter and 
salts. Its function is to convert starch into glucose, and assist in the 
digestion of the albuminoids. 
The Pancreatic Juice is secreted by the pancreas, a flattened gland 
about six inches long, running transversely across the posterior wall of the 
abdomen, behind the stomach; its duct opens into the duodenum. 
The Pancreatic fluid is transparent, colorless, strongly alkaline and 
viscid, having a specific gravity of 1.040. 
COMPOSITION OF PANCREATIC JUICE. 
Water 900.76 
Pancreatin 90.44 
Inorganic salts 8.80 
1000.00 
The Pancreatin is the most important constituent, and gives to the fluid 
its digestive power. It is coagulated by heat, nitric acid and alcohol. DIGESTION. 
27 
The Functions of the pancreatic fluid are: 1. To transform starch 
and cane sugar into glucose. 2. To emulsify the oils and fats, and split 
them up into fatty acids and glycerine. 3. To convert albuminoid sub- 
stances into peptones. 
The Emulsification of the fats seems to be the principal office of the 
pancreatic juice, for disease of the pancreas, preventing the discharge of 
its secretion into the intestine, is attended by an abundant discharge of fat 
from the bowels. 
The total quantity of this fluid secreted in 24 hours has not been accu- 
rately determined; varies from one to two pounds. 
The Bile has an important influence in the elaboration of the food and 
its preparation for absorption. It is a golden-brown, viscid fluid, having a 
neutral or slighly alkaline reaction and a specific gravity of 1.020. 
Water 859.2 
COMPOSITION OF BILE. 
Sodium glycocholate 
Sodium taurocholate 
... gi-4 
Fat 9.2 
Cholesterine 2.6 
Mucus and coloring matter 29.8 
Salts 7.8 
1000.00 
The Biliary salts are characteristic ingredients, and are formed in the 
liver by the process of secretion, from materials furnished by the blood. 
They probably aid digestion. 
Cholesterine is a product of waste taken up by the blood from the nervous 
tissues and excreted by the liver. 
The Coloring matters which give the tints to the bile are biliverdin and 
bilirubin, and are probably derived from the coloring matter of the blood. 
The Bile is both a secretion and an excretion; it is constantly being 
formed and discharged by the hepatic ducts into the gall bladder, in which 
it is stored up, during the intervals of digestion. As soon as food enters 
the intestines, it is poured out abundantly by the contraction of the walls 
of the gall bladder. 
The Amount secreted in 24 hours is about pounds. 
Functions of the Bile. (1) It assists in the emulsification of the fats 
and promotes their absorption. (2) It tends to prevent putrefactive 
changes in the food. (3) Stimulates the secretions of the intestinal 
glands, and excites the normal peristaltic movements of the bowels. 28 
HUMAN PHYSIOLOGY. 
The digested food, the chyme, is a grayish, pultaceous mass, but as it 
passes through the intestines it becomes yellow, from admixture with the 
bile. It is propelled onward by vermicular motion; by the contraction of 
the circular and longitudinal muscular fibres. 
As the digested food passes through the intestines the nutritious matters 
are absorbed into the blood, and the residue enters the large intestine. 
The Faeces consist chiefly of indigestible matters, excretin, stercorin 
and salts; varying in amount from 4 to 7 oz. in 24 hours. 
Defecation is the voluntary act of extruding the faeces from the body; 
accomplished by a relaxation of the sphincter muscle, the contraction of 
the walls of the rectum, assisted by the abdominal muscles. 
The Gases contained in the stomach and small intestine are oxygen, 
nitrogen, hydrogen, and carbonic acid. In the large intestine, carbonic 
acid, sulphuretted and carburetted hydrogen. They are introduced with 
the food, and also developed by chemical changes in the alimentary canal. 
They distend the intestines, aid capillary circulation, and tend to prevent 
pressure. 
Absorption has for its object the introduction of new materials into the 
blood, and takes place mainly from the alimentary tract; but also to some 
extent from the skin, respiratory surface and closed cavities of the body. 
The Agents of Absorption are the veins and lymphatics. 
As a result of the process of digestion the different alimentary substances 
are converted into forms which are capable of being absorbed into the 
blood, e. g., albuminose, glucose and fatty emulsion, water and inorganic 
matters undergoing no change, being already in a condition to be absorbed 
and to play a part in the nutritive process. 
The blood vessels which are most active as absorbents, are the gastric, 
superior and inferior mesenteric veins. They arise in the coats of the 
alimentary canal, and as they converge, unite with the splenic vein to form 
the portal vein, which enters the liver. 
As the digested mass of food, the chyme, passes through the alimentary 
canal a large portion of it disappears; the veins absorb water, albutninose, 
glucose, and inorganic salts, and convey them directly into the liver; the 
blood of the portal vein being especially rich in these substances. 
At times, after the ingestion of large quantities of oleaginous food, the 
blood vessels take up, in addition, a certain quantity of fatty matter; but 
this is not usually the case; the fats being absorbed by special vessels, the 
lymphatics or lacteals. 
ABSORPTION. ABSORPTION. 
29 
General Anatomy of the Lymphatic System. The lymphatics 
constitute a system of minute, delicate, transparent vessels, which, having 
their origin at the periphery of the body, pass forward toward the centre 
and empty into the veins at the base of the neck, by means of the thoracic 
duct. In their course they pass through small ovoid bodies, the lymphatic 
glands. 
Origin of Lymphatics. The lymphatic vessels commence by a fine 
capillary plexus, or in irregular lymph spaces, distributed over the surface 
and throughout the interior of the various tissues of the body. 
The lymphatics of the small intestine, the lacteals, arise within the villous 
processes which cover its inner surface throughout its entire extent. 
Each villus is formed by an elevation of the mucous membrane, covered 
externally by a laver of columnar epithelial cells; in the interior are found 
numerous blood vessels, non-striated muscular fibres, and the beginnings 
of the lacteal vessels. 
The structure of the larger vessels resembles that of the veins, consisting 
of three coats— 
i. External, composed of fibrous tissue and muscular fibres, arranged 
longitudinally. 2. Middle, consisting of white fibrous and yellow elastic 
tissue, non-striated muscular fibres, arranged transversely. 3. Internal, 
composed of an elastic membrane, lined by epithelial cells. 
Throughout their course are found numerous semi-lunar valves, looking 
toward the larger vessels, formed by a folding of the inner coat and 
strengthened by connective tissue. 
Lymphatic Glands consist of an external fibrous covering, from the 
inner surface of which partitions of fibrous tissue, the trabeculae, pass into 
the substance of the gland, forming a stroma or network, in the meshes of 
which are found the true lymph corpuscles. 
The lymphatics which enter the gland are called the afferent vessels; 
those which leave it, the efferent vessels. 
The Thoracic Duct is the general trunk of the lymphatic system, into 
which the vessels of the lower extremities, of the abdominal organs, of the 
left side of the head and left arm empty their contents. It is about twenty 
inches in length, arises in the abdomen, opposite the third lumbar verte- 
bra, by a dilatation, the receptaculum chyli; ascends along the vertebral 
column to the seventh cervical vertebra, and terminates in the venous 
system at the junction of the internal jugular and subclavian veins on the 
left side. The lymphatics of the right side of the head, of the right arm 
and the right side of the thorax, terminate in the right thoracic duct, about 30 
HUMAN PHYSIOLOGY. 
one inch in length, which joins the venous system at the junction of the 
internal jugular and subclavian on the right side. 
Lymph is a clear, transparent fluid, slightly alkaline, having a saline 
taste and a specific gravity of 1.022. It is found in the lymphatic vessels 
throughout the body. 
Lymph contains a number of corpuscles (the leucocytes') resembling the 
white corpuscles of the blood, which increase in number as it passes 
through the lymphatic glands. They are about of an inch in diam- 
eter and somewhat granular; they are discharged into the blood, but their 
function is obscure. When withdrawn from the vessels lymph undergoes 
spontaneous coagulation, separating into serum and clot, as in the case of 
the blood. 
DR. OWEN REES. 
Water 96.536 
Proteids (serum-albumen, fibrin, globulin) 1.320 
Extractives (urea, sugar, cholesterine) 1.559 
Fatty matter a trace 
Salts 0.585 
100.000 
COMPOSITION OF LYMPH. 
Origin of Lymph. Lymph is undoubtedly a transudation from the 
capillary blood vessels, occurring during the process of nutrition, and is 
identical, for the most part, with the liquor sanguinis, or plasma. As new 
material is constantly exuded, the old is absorbed by the lymphatics, and 
returned again to the circulation. 
Excrementitious matters, as urea, cholesterine, etc., are also taken up 
from the tissues by the lymphatics and emptied into the blood. 
The total quantity of lymph poured into the thoracic duct in 24 hours 
has been estimated at 3 lbs. 
Chyle. As a result of the process of digestion, the oleaginous matters 
which have been acted upon by the pancreatic juice and bile are trans- 
formed into a condition of emulsion, forming an opaque, milky fluid, 
termed chyle, which adheres to the folds of the mucous membrane and 
villi. * 
The Molecules of the fat are first absorbed by the epithelial cells upon 
the surface of the villi, through which they pass and enter the lymphatics. 
Absorption by the Lacteals. The lacteals, or lymphatics of the small 
intestine, have their origin in the interior of the villi, from which they 
emerge and form a lymphatic plexus; the larger branches of which pass ABSORPTION. 
31 
through the layers of the mesentery, and finally terminate in the thoracic 
duct. 
In the intervals of digestion the lacteals contain clear, transparent lymph, 
and are invisible on account of their small size and delicacy. But during 
digestion these vessels become filled, from absorption of the chyle, and form 
a visible network of white vessels ramifying through the mesentery, and 
converging toward the receptaculum chyli. 
The lacteal vessels also absorb a small quantity of water, albuminose, 
glucose and salts. 
Water 902.37 
Albumen 35.16 
Fibrin 3.70 
Extractives 15.65 
Fatty matters 36.01 
Salts 7.11 
1000.00 
COMPOSITION OF CHYLE. 
The Products of digestion find their way into the general circulation by 
two routes: — 
1. Water, albuminose, glucose and salts, are mainly absorbed by the 
gastric and mesenteric veins, carried into the liver, through the capillaries 
of which they pass, and enter the inferior vena cava by the hepatic veins. 
2. The Fats are absorbed by the lacteals, emptied into the thoracic duct, 
and enter the blood at the junction of the internal jugular and subclavian 
veins. 
Forces aiding the movements of Lymph and Chyle. 
1. Endosmosis. The continued transudation of matter from the capil- 
laries, and its absorption into the lymphatics by endosmosis, constitutes the 
main cause, the vis-a-tergo, of the movement of the lymph; it is so con- 
siderable as to rupture the walls of the vessels if they are ligated. 
2. Contraction of the non-striated muscular fibres in the walls of the 
lymphatic vessels, especially when fully distended, aided by the action 
of the valves, promotes the onward flow of the fluids. 
3. Muscular contraction in all parts of the body, by exerting intermit- 
tent pressure upon the lymphatic vessels, hastens the current onwards; 
regurgitation being prevented by the closure of the valves. 
4. The Inspiratory movement, by expanding the chest, causes a dilation 
of the thoracic duct, and a rapid flow of lymph and chyle into it; during 
expiration it is compressed, and the fluids forcibly expelled into the venous 
system. 32 
HUMAN PHYSIOLOGY. 
The Blood is a nutritive fluid containing all the elements necessary for 
the repair of the tissues; it also contains principles of waste absorbed 
from the tissues, which are conveyed to the various excretory organs and 
by them eliminated from the body. 
The total amount of blood in the body is estimated to be about one- 
eighth of the body weight; from 16 to 18 pounds in an individual of 
average physical development. The quantity varies during the 24 hours ; 
the maximum being reached in the afternoon, the minimum in the early 
morning hours. 
Blood is a heterogeneous, opaque red fluid, having an alkaline reaction, 
a saline taste, and a specific gravity of 1.055. 
The opacity is due to the refraction of the rays of light by the elements 
of which the blood is composed. The color varies in hue, from a bright 
scarlet in the arteries to a deep purple in the veins, due to the presence of 
a coloring matter, hcemoglobin, in different degrees of oxidation. 
The alkalinity is constant, and depends upon the presence of the tri- 
sodium phosphate; becomes acid in cholera and sunstroke. 
The saline taste is due to the amount of sodium chloride present. 
The specific gravity ranges within the limits of health from 1.045 to 1.075 • 
The odor of the blood is characteristic, and varies with the animal from 
which it is drawn, due to the presence of caproic acid. 
The temperature of the blood ranges from 98° Fahr. at the surface to 
107° P’ahr. in the hepatic vein; it loses heat by radiation and evaporation 
as it approaches the extremities, and as it passes through the lungs. 
Blood consists of two portions:— 
1. The Liquor Sanguinis or Plasma, a transparent, colorless fluid in 
which are floating— 
2. Red and white corpuscles ; these constituting by weight less than one- 
half, 40 per cent., of the entire amount of blood. 
BLOOD. 
COMPOSITION OF PLASMA. dalton. 
Water 902.00 
Albumen 53-°° 
Paraglobulin 22.00 
Fibrinogen 3.00 
Fatty matters 2.50 
Crystallizable nitrogenous matters 4.00 
Other organic matter 5.00 
Mineral salts 8.50 
1000.00 BLOOD. 
33 
Water acts as a solvent for the inorganic matters and suspends the 
corpuscular elements. 
Albumen is the nutritious principle of the blood; it is absorbed by the 
tissues to repair their waste, and is transformed into the organic basis 
characteristic of each structure. 
Paraglobulin or Jibrinoplastin is a soft amorphous substance precipitated 
by sodium chloride in excess, or by passing a stream of carbonic acid 
through dilute serum. 
Fibrinogen can also be obtained by strongly diluting the serum and 
passing carbonic acid through it for a long time, when it is precipitated 
as a viscous deposit. 
Fatty matters exist in small proportion, except in pathological conditions 
and after the ingestion of food rich in oleaginous matters; it soon dis- 
appears, undergoing oxidation, generating heat and force, or is deposited 
as adipose tissue. 
Sugar is represented by glucose, a product of the digestion of saccharine 
matter and starches in the alimentary canal; glycogenic matter is derived 
from the liver. 
The Saline constituents aid the process of osmosis, give alkalinity to the 
blood, promote the absorption of carbonic acid from the tissues into 
the blood, and hold other substances in solution; the most important are 
the sodium and potassium chlorides, the calcium and magnesium phos- 
phates. 
Excrementitious matters are represented by carbonic acid, urea, creatin, 
creatinin, urates, oxalates, etc.; they are absorbed from the tissues by the 
blood and conveyed to the excretory organs, lungs, kidneys, etc. 
Gases. Oxygen, nitrogen, and carbonic acid exist in varying propor- 
tions. 
BLOOD CORPUSCLES. 
The corpuscular elements of the blood occur under two distinct forms, 
which from their color are known as the red and white corpuscles. 
The Red Corpuscles, as they float in a thin layer of the Liquor Sanguinis, 
are of a pale straw color ; it is only when aggregated in masses that they 
assume the bright red color. Inform they are circular and biconcave; 
they have an average diameter of the an inch- 
In mammals, birds, reptiles, amphibia and fish the corpuscles vary in 
size and number, gradually becoming larger and less numerous as the scale 
of animal life is descended, e. g. :— 34 
HUMAN PHYSIOLOGY. 
TABLE SHOWING COMPARATIVE DIAMETER OF RED 
CORPUSCLES. 
Mammals. 
Man, 32^3- 
Chimpanzee, 
Ourang, 3^3. 
Dog, 3BV2- 
Cat, «W 
Hog, iihs- 
Horse, ISW 
Ox, 52*37 • 
Birds. 
Eagle, tbW 
Owl, T7!S3- 
Sparrow, 21*w. 
Swallow, 5x35. 
Pigeon, rsVs- 
Turkey, 
Goose, ihbb- 
Swan, ib'ss- 
Reptiles. 
Turtle, Ti&x. 
Tortoise, 
Lizard, tsbs- 
Viper, tbVj- 
Amphibia. 
Frog, nW 
1 oad, Tuks- 
Proteus, 
Siren, 
Amphiuma, 3J3. 
Fish. 
Perch, 20&5* 
Carp, 2ihi- 
Pike, soVff* 
I7is- 
In man and the mammals the red corpuscles present neither a nucleus 
nor a cell wall, and are universally of a small size. They can be readily 
distinguished from the corpuscles of birds, reptiles and fish, in which they 
are larger, oval in shape and possess a well defined nucleus. 
The red corpuscles are exceedingly numerous, amounting to about 
5,000,000 in a cubic millimetre of blood. In structure they consist of a 
firm, elastic, colorless framework, the stroma, in the meshes of which is 
entangled the coloring matter, the hcemoglobin. 
Water 688.00 
Globulin 282.22 
Hsemoglobin 16.75 
Fatty matter 2.31 
Extractives 2.60 
Mineral salts 8.12 
1000.00 
CHEMICAL COMPOSITION OF RED CORPUSCLES. 
Hcemoglobin, the coloring matter of the corpuscles, is an albuminous 
compound, composed of C. O. H. N. S. and iron. It may exist either in 
an amorphous or crystalline form. When deprived of all its oxygen, 
except the quantity entering into its intimate composition, the haemoglobin 
becomes darker in color, somewhat purple in hue, and is known as reduced 
hcemoglobin. When exposed to the action of oxygen it again absorbs a 
definite amount and becomes scarlet in color, and is known as oxy-hcemo- 
globin. The amount of oxygen absorbed is 1.76 c.cm. (xV cubic inch,) for 
I milligramme grain) of hsemoglobin. 
It is this substance which gives the color to the venous and arterial 
blood. As the venous blood passes through the capillaries of the lungs, 
the reduced hcemoglobin absorbs the oxygen from the pulmonary air and 
becomes oxy-hcemoglobin, scarlet in color, and the blood becomes arterial. BLOOD. 
35 
When the arterial blood passes into the systemic capillaries the oxygen is 
absorbed by the tissues, the haemoglobin becomes reduced, purple in 
color, and the blood becomes venous. A dilute solution of oxy-hsemo- 
globin gives two absorption bands between the lines D and E of the solar 
spectrum. Reduced haemoglobin gives but one absorption band, occupying 
the space existing between the two bands of the oxy-haemoglobin spectrum. 
The Function of the red corpuscles is, therefore, to absorb oxygen and 
carry it to the tissues; the smaller the corpuscles, and the greater the 
number, the greater is the quantity of oxygen absorbed; and, consequently, 
all the vital functions of the body become more active. 
The White Corpuscles are far less numerous than the red, the proportion 
being, on an average, about I white to 350 or 400 red; they are globular 
in shape, and measure the twists °f an inch in diameter, and consist of a 
soft, granular, colorless substance, containing several nuclei. 
The white corpuscles possess the power of spontaneous movement, alter- 
nately contracting and expanding, throwing out processes of their substance 
and quickly withdrawing them, thus changing their shape from moment to 
moment. These movements resemble those of the amoeba, and for this 
reason are termed amoeboid. They also possess the capability of moving 
from place to place. In the interior of the vessels they adhere to the inner 
surface while the red corpuscles move through the centre of the stream. 
The white corpuscles are identical with the leucocytes, and are found in 
milk, lymph, chyle and other fluids. 
Origin of Corpuscles. The red corpuscles take their origin from the 
mesoblastic cells in the vascular area of the developing embryo. 
In the adult they are produced from colorless nucleated corpuscles 
resembling the white corpuscles. The spleen is the organ in which they 
are finally destroyed. 
The white corpuscles originate from the leucocytes of the adenoid tissue, 
and subsequently give rise to the red corpuscles and partly to new tissues 
that result from inflammatory action. 
COAGULATION OF THE BLOOD. 
When blood is withdrawn from the body and allowed to remain at rest 
it becomes somewhat thick and viscid in from three to five minutes; this 
viscidity gradually increases until the entire volume of blood assumes a 
jelly-like consistence, which occupies from five to fifteen minutes. 
As soon as coagulation is completed a second process begins, which con- 
sists in the contraction of the coagulum and the oozing of a clear, straw- 
colored liquid, the serum, which gradually increases in quantity as the clot 36 
HUMAN PHYSIOLOGY. 
diminishes in size, by contraction, until the separation is completed, which 
occupies from 12 to 24 hours. 
The changes in the blood are as follows:— 
Before coagulation. 
Liq. Sanguinis 
or 
Plasma. 
Water. 
Albumen. 
Fibrin. 
Salts. 
Living blood. 
Consisting of 
Corpuscles. Red and white. 
After coagulation. 
Crassamentum. 
Clot or coagulum. 
Containing 
Fibrin. 
Corpuscles. 
Dead blood. 
Serum. 
Containing 
f Water. 
-j Albumen. 
[ Salts. 
The Serum, therefore, differs from the Liquor Sanguinis in not contain- 
ing fibrin. 
In from 12 to 24 hours the upper surface of the clot presents a grayish 
appearance, the buffy coat, which is due to the rapid sinking of the red 
corpuscles beneath the surface, permitting the fibrin to coagulate without 
them, which then assumes a grayish-yellow tint. Inasmuch as the white 
corpuscles possess a lighter specific gravity than the red, they do not sink 
so rapidly, and becoming entangled in the fibrin, assist in forming the buffy 
coat. Continued contraction gives a cupped appearance to the surface of 
the clot. 
Inflammatory states of the blood produce a marked increase in the 
buffed and cupped condition, on account of the aggregation of the corpus- 
cles and their tendency to rapid sinking. 
Nature of Coagulation. Coagulable fibrin does not pre-exist in the 
blood, but is formed at the moment blood is withdrawn from the vessels. 
According to Denis, a liquid substance, plasmine, exists in the blood, 
which, when withdrawn from the circulation, decomposes into fibrin and 
7net-albumen. 
According to Schmidt, fibrin results from the union of fibrinoplastin 
(paraglobulin) and fibrinogen, brought about by the presence of a third 
substance, the fibrin ferment. 
Conditions Influencing Coagulation. The process is retarded by 
cold, retention within living vessels, neutral salts in excess, inflammatory 
conditions of the system, imperfect aeration, exclusion from air, etc. CIRCULATION OF THE BLOOD. 
37 
It is hastened by a temperature of ioo° F., contact with air, rough sur- 
faces and rest. 
Blood coagulates in the body after the arrest of the circulation in the 
course of 12 to 24 hours; local arrest of the circulation from compression 
or a ligature will cause coagulation, thus preventing hemorrhages from 
wounded vessels. 
The Composition of the Blood varies in different portions of the 
body. The arterial differs from the venous, in being more coagulable, in 
containing more oxygen and less carbonic acid, in having a bright scarlet 
color, from the union of oxygen with haemoglobin; the purple hue of 
venous blood results from the deoxidation of the coloring matter. 
The blood of the portal vein differs in constitution, according to different 
stages of digestive process; during digestion it is richer in water, albumin- 
ous matter and sugar; occasionally contains fat; corpuscles are dimin- 
ished, and there is an absence of biliary substances. 
The blood of the hepatic vein contains a larger proportion of red and 
white corpuscles; the sugar is augmented, while albumen, fat and fibrin 
are diminished. 
Pathological conditions of the Blood. 
1. Plethora—increase in the volume or quantity of blood. 
2. Ancemia—deficiency of red globules with increase of water. 
3. Leucocythemia—increase of white and diminution of red corpuscles. 
4. Glycohcemia—excess of sugar in the blood. 
5. Urcemia—increase in the amount of urea. 
6. Cholestercemia— an excess of cholesterine in the blood. 
7. Thrombosis and embolism—clotting of blood in the vessels and dis- 
semination of coagula. 
8. Lipcemia—an excess of fat. 
9. Melanamia—pigment in the blood. 
CIRCULATION OF THE BLOOD. 
The Object of the Circulation is to distribute nutritious blood to all 
portions of the system and to carry waste materials to the various elimi- 
nating organs. 
The Circulatory Apparatus consists of the heart, arteries, capillaries 
and veins. 
The Heart is a hollow, muscular organ, pyramidal in shape, measuring 
inches in length and weighing from io to 12 oz. in the male, and 8 
to 10 oz. in the female. It is invested externally by a closed fibro-serous 38 
HUMAN PHYSIOLOGY. 
sac, the pericardium, containing a small amount of fluid, which prevents 
friction as the visceral and parietal layers glide over each other, during 
the movements of the heart and lungs. 
The heart consists of four cavities, a right auricle and ventricle, and a 
left auricle and ventricle, completely separated by a vertical partition. The 
right is the venous side, receiving the blood from the venae cavae, and pro- 
pelling it through the pulmonary artery into the lungs; the left is the 
arterial side, receiving the arterial blood from the lungs by the pulmonary 
veins, and propelling it through the aorta to the system at large. 
The Auriculo-ventricular orifices are guarded on the right and left sides 
by the tricuspid and mitral valves respectively, while they are so arranged 
as to permit the flow of blood in the forward direction only; the orifices 
of the pulmonary artery and aorta are guarded by the semi-lunar valves. 
The Endocardium is a delicate, shining membrane, lining the interior of 
the heart, and continuous with the lining membrane of the blood vessels. 
The walls of the left ventricle are nearly half an inch in diameter, being 
two or three times thicker than the walls of the right; the force of its 
contraction being much greater. 
The Function of the Heart is to propel the blood to all portions of 
the vascular system; accomplished by successive alternate contractions and 
relaxations of its muscular walls, constituting the systole and diastole. 
Course of the blood through the Heart. The venous blood re- 
turned to the heart by the superior and inferior vense cavse is emptied, 
during the diastole, into the right auricle, on the contraction of which it is 
forced through the right auriculo-ventricular opening into the right ventricle 
and distends it. Upon contraction of the ventricle the blood is propelled 
through the pulmonary artery into the lungs, where it undergoes aeration 
and is changed in color. 
The arterial blood is now collected by the pulmonary veins and poured 
into the left auricle; thence it passes into the left ventricle, which becomes 
fully distended. Upon the contraction of the ventricle, the blood is pro- 
pelled into the aorta, and by it distributed to the system at large, to be 
again returned to the heart by the veins. 
Regurgitation from the ventricles into the auricles during the systole is 
prevented by the closure of the tricuspid and mitral valves; regurgitation 
from the pulmonary artery and aorta into the ventricles during the diastole 
is prevented by the closure of the semi-lunar valves. 
Movements of the Heart. At each revolution, during the systole, 
the heart hardens and becomes shortened in its long diameter; its apex is CIRCULATION OF THE BLOOD. 
39 
raised up, rotated on its axis from left to right and thrown forward against 
the walls of the chest. The impulse of the heart, observed about two 
inches below the nipple, and one inch to the sternal side, between the fifth 
and sixth ribs, is caused mainly by the apex of the heart striking against 
the chest walls, assisted by the distention of the great vessels about the 
base of the heart. 
Sounds of the Heart. If the ear be placed over the cardiac region 
two distinct sounds are heard during each revolution of the heart, closely 
following each other and which differ in character. 
The sound coinciding with the systole in point of time, the first sound, is 
long and dull, and caused by the closure and vibration of the auriculo-ven- 
tricular valves, the contraction of the walls of the ventricles and the apex 
beat; the second sound, occurring during the diastole, is short and sharp, 
and caused by the closure of the semi-lunar valves. 
The capacity of the left ventricle when fully distended is estimated at 
from four to seven ounces. 
The frequency of the heart’s action varies at different periods of life, 
but in the adult male it beats about 72 times per minute. It is influenced 
by age, exercise, posture, digestion, etc. 
Age. Before birth the number of pulsations per minute averages 140 
During the first year it diminishes to 128 
During the third year diminishes to 95 
From the eighth to the fourteenth years averages 84 
In adult life the average is 72 
Exercise and digestion increase the frequency of the heart’s action. 
Posture influences the number of pulsations per minute ; in the male, 
standing, the average is 81; sitting, 71; lying, 66; independent, for the 
most part, of muscular effort. 
The Rhythmical movements of the heart are dependent upon, 1. An 
inherent irritability of the muscular fibres, which manifests itself as long as 
the nutrition is maintained. 2. The continuous flow of blood through its 
cavities distending them and stimulating the endocardium. 
The force exerted by the left ventricle at each contraction 
has been estimated at 52 pounds. If a tube be inserted into the aorta the 
pressure there will be sufficient to support a column of blood nine feet or 
a column of mercury six inches in height, the weight in either case being 
about four pounds. The estimation of the force which the heart is 
required to exert to support this column of blood, is arrived at by multiply- 
ing the pressure in the aorta (4 pounds) by the area of the internal surface 40 
HUMAN PHYSIOLOGY. 
of the left ventricle (about 13 inches). Each inch of the ventricle being 
capable of supporting a downward pressure of 4 pounds. 
Work done by the Heart. The work done by the heart is esti- 
mated by multiplying the amount of blood sent out from the right and left 
ventricles at each contraction, by the pressure in the pulmonary artery and 
aorta respectively, e. g., when the right ventricle contracts it forces out 
one quarter pound of blood, and in so doing must overcome a pressure in 
the pulmonary artery sufficient to support a column of blood three feet in 
height; that is, must exert energy sufficient to raise lb 3 feet or X 3 
or fb one foot. When the left ventricle contracts it sends out lb of 
blood, and in so doing the left ventricle must overcome pressure in the 
aorta sufficient to support a column of blood nine feet in height; that is, 
must exert energy sufficient to raise lb 9 feet, or X 9 or 2)4' lbs one 
foot. Work done is estimated by the amount of energy required to raise 
a definite weight a definite height, the unit, the foot pound, being that 
required to raise one pound one foot. 
The heart, therefore, at each systole exerts energy sufficient to raise 3 
foot pounds, and as it contracts 72 times per minute it would raise in that 
time 3 X 72 or 216 foot pounds; and in one hour 216 X 60 or 12,960 foot 
pounds; and in 24 hours 12,960 X 24 or 311,040 foot pounds or 138.5 foot 
tons. 
Influence of the Nervous System upon the Heart. When the 
heart of a frog is removed from the body it continues to beat for a 
variable length of time, depending upon the nature of the conditions sur- 
rounding it. The heart of warm-blooded animals continues to beat but for 
a very short time. The cause of the continued pulsations of the frog heart 
is the presence of nervous ganglia in its substance. These ganglia have 
not been shown to exist in the mammalian heart, but there is reason to 
believe that the nervous mechanism is fundamentally the same. 
The ganglia of the heart are three in number, one situated at the open- 
ing of the inferior vena cava (the ganglion of Remak), a second situated 
in the auriculo-ventricular septum (the ganglion of Bidder), and a third 
situated in the inter-auricular septum (the ganglion of Ludwig). The first 
two are motor in function and excite the pulsations of the heart; the third 
is inhibitory in function and retards the action of the heart. The actions 
of these ganglia, though for the most part automatic, are modified by 
impressions coming through nerves from the medulla oblongata. When 
the inhibitory centre is stimulated by muscarin, the heart is arrested in 
diastole; when atropia is applied, the heart recommences to beat, because 
atropia paralyzes the inhibitory centre. ARTERIES. 
41 
The nerves modifying the action of the heart are the Pneumogastric 
(Vagus) and the Accelerator nerves. 
The Pneumogastric nerve after emerging from the medulla receives 
motor fibres from the spinal accessory nerve. It then passes downward, 
giving off branches, some of which terminate in the inhibitory ganglion. 
Stimulation of the vagus by increasing the activity of the inhibitory centre 
arrests the heart in diastole with its cavities full of blood; but as the stimu- 
lation is only temporary, after a few seconds the heart recommences to 
beat; at first the pulsations are weak and feeble, but soon regain their 
original vigor. After the administration of atropia in sufficient doses to 
destroy the termination of the pneumogastric, stimulation of its trunk has no 
effect upon the heart. The inhibitory fibres in the vagus are constantly in 
action, for division of the nerve on both sides is always followed by an 
increase in the frequency of the heart’s pulsations. 
The Accelerator fibres arise in the medulla, pass down the cord, emerge 
in the cervical region, pass to the last cervical and first dorsal ganglia of 
the sympathetic, and thence to the heart. Stimulation of these fibres causes 
an increased frequency of the heart’s pulsations, but they are diminished 
in force. 
The Arteries are a series of branching tubes conveying blood to all 
portions of the body. They are composed of three coats— 
1. External, formed of areolar and elastic tissue. 
2. Middle, contains both elastic and muscular fibres, arranged trans- 
versely to the long axis of the artery. The elastic tissue is more 
abundant in the larger vessels, the muscular in the smaller. 
3. Internal, composed of a thin homogeneous membrane, covered with 
a layer of elongated endothelial cells. 
The arteries possess both elasticity and contractility. 
The Property of Elasticity allows the arteries already full to accommo- 
date themselves to the incoming amount of blood, and to convert the 
intermittent acceleration of blood in the large vessels into a steady and 
continuous stream in the capillaries. 
The Contractility of the smaller vessels equalizes the current of blood, 
regulates the amount going to each part, and promotes the onward flow of 
blood. 
Blood Pressure. Under the influence of the ventricular systole, the 
recoil of the elastic walls of the arteries, and the resistance offered by the 
capillaries, the blood is constantly being subjected to a certain amount of 
ARTERIES. 42 
HUMAN PHYSIOLOGY. 
pressure. If a large artery of an animal be divided, and a glass tube of 
the same calibre be inserted into its orifice, the blood will rise to a height 
of about nine feet; or if it be connected with a mercurial manometer, the 
mercury will rise to a height of six inches. This height will be a measure 
of the pressure in the vessel. The absolute quantity of mercury sustained 
by an artery can be arrived at by multiplying the height of the column by 
the area of a transverse section of that artery. 
The pressure of the blood is greatest in the large arteries, but gradually 
decreases toward the capillaries. 
The blood pressure is increased or diminished by influences acting upon 
the heart or upon the peripheral resistance of the capillaries, viz.:— 
If, while the force of the heart remains the same, the number of pulsa- 
tions per minute increases, thus increasing the volume of blood in the 
arteries, the pressure rises. If the rate remains the same, but the force 
increases, the pressure again rises. Causes that increase the peripheral 
resistance by contracting the arterioles, e. g., vaso-motor nerves, cold, etc., 
produce an increase of the pressure. 
On the other hand, influences which diminish either the volume of the 
blood, or the number of pulsations, or the force of the heart, or the 
peripheral resistance, lower the pressure. 
The Pulse is the sudden distention of the artery in a transverse and 
longitudinal direction, due to the injection of a volume of blood into the 
arteries at the time of the ventricular systole. As the vessels are already 
full of blood, they must expand in order to accommodate themselves to the 
incoming volume of blood. The blood pressure is thus increased, and the 
pressure originating at the ventricle -excites a pulse waste, which passes 
from the heart toward the capillaries at the rate of about twenty-nine 
feet per second. It is this wave that is appreciated by the finger. 
The Velocity with which the blood flows in the arteries diminishes 
from the heart to the capillaries, owing to an increase of the united sec- 
tional area of the vessels, and increases in rapidity from the capillaries 
toward the heart. It moves most rapidly in the large vessels, and espe- 
cially under the influence of the ventricular systole. From experiments 
on animals, it has been estimated to move in the carotid of man at the rate 
of sixteen inches per second, and in the large veins at the rate of four 
inches per second. 
The Calibre of the blood vessels is regulated by the vaso-motor 
nerves, which have their origin in the gray matter of the medulla oblon- 
gata. They issue from the spinal cord through the anterior roots of spinal ARTERIES. 
43 
nerves, pass through the sympathetic ganglia, and ultimately are distributed 
to the coats of the blood vessels. They exert, at different times, a constrict- 
ing and dilating action upon the vessels, thus keeping up the arterial tonus. 
Capillaries. The capillaries constitute a network of vessels of micro- 
scopic size, which distribute the blood to the inmost recesses of the tissues, 
inosculating with the arteries on the one hand and the veins on the other ; 
they branch and communicate in every possible direction. 
The diameter of a capillary vessel varies from the -rfas to the 
of an inch; their walls consist of a delicate homogeneous membrane, the 
TubniS of an inch in thickness, lined by flattened, elongated, endothelial 
cells, between which, here and there, are observed stomata. 
It is through the agency of the capillary vessels that the phenomena of 
nutrition and secretion takes place, for here the blood flows in an equable 
and continuous current, and is brought into intimate relationship with the 
tissues, two of the essential conditions for proper nutrition. 
The rate of movement in the capillary vessels is estimated at one inch 
in thirty seconds. 
, In the capillary current the red corpuscles may be seen hurrying down 
the centre of the stream, while the white corpuscles in the still layer adhere 
to the walls of the vessel, and at times can be seen to pass through the 
walls of the vessel by amoeboid movements. 
The passage of the blood through the capillaries is mainly due to the 
force of the ventricular systole and the elasticity of the arteries; but it is 
probably also aided by a power resident in the capillaries themselves, the 
result of a vital relation between the blood and the tissues. 
The Veins are the vessels which return the blood to the heart; they 
have their origin in the venous radicles, and as they approach the heart, 
converge to form larger trunks, and terminate finally in the venae cavae. 
They possess three coats— 
1. External, made up of areolar tissue. 
2. Middle, composed of non-striated muscular fibres, yellow, elastic and 
fibrous tissue. 
3. Internal, an endothelial membrane, similar to that of the arteries. 
Veins are distinguished by the possession of valves throughout their 
course, which are arranged in pairs, and formed by a reflection of the in- 
ternal coat, strengthened by fibrous tissue; they always look toward the 
heart, and when closed prevent a return of blood in the veins. Valves are 
most numerous in the veins of the extremities, but are entirely absent in 
many others. 44 
HUMAN PHYSIOLOGY. 
The onward flow of blood in the veins is mainly due to the action of 
the heart; but is assisted by the contraction of the voluntary muscles and 
the force of aspiration. 
Muscular contraction, which is intermittent, aids the flow of blood in 
the veins, by compressing them. As regurgitation is prevented by the 
closure of the valves, the blood is forced onward toward the heart. 
Rhythmical movements of veins have been observed in some of the 
lower animals, aiding the onward current of blood. 
During the movement of inspiration the thorax is enlarged in all its 
diameters, and the pressure on its contents at once diminishes. Under 
these circumstances a suction force is exerted upon the great venous trunks, 
which causes the blood to flow with increased rapidity and volume toward 
the heart. 
Venous pressure. As the force of the heart is nearly expended in 
driving the blood through the capillaries, the pressure in the venous 
system is not very marked, not amounting in the jugular vein of a dog to 
more than tV that of the carotid artery. 
The time required for a complete circulation of the blood throughout the 
vascular system has been estimated to be from 20 to 30 seconds, while for 
the entire mass of blood to pass through the heart 58 pulsations would be 
required, occupying 48 seconds. 
The Forces keeping the blood in circulation are— 
1. Action of the heart. 
2. Elasticity of the arteries. 
3. Capillary force. 
4. Contraction of the voluntary muscles upon the veins. 
5. Respiratory movements. 
RESPIRATION. 
Respiration is the function by which oxygen is absorbed into the 
blood and carbonic acid exhaled. The appropriation of the oxygen and 
the evolution of carbonic acid takes place in the tissues as a part of the 
general nutritive process; the blood and respiratory apparatus constituting 
the media by means of which the interchange of gases is accomplished. 
The Respiratory Apparatus consists of the larynx, trachea and lungs. 
The Larynx is composed of firm cartilages, united together by liga- 
ments and muscles; running antero-posteriorly across the upper opening 
are four ligamentous bands, the two superior or false vocal cords, and the 
two inferior or true vocal cords, formed by folds of the mucous membrane. RESPIRATION. 
45 
They are attached anteriorly to the thyroid cartilages and posteriorly to the 
arytenoid cartilages, and are capable of being separated by the contraction 
of the posterior crico-arytenoid muscles, so as to admit the passage of air 
into and from the lungs. 
The Trachea is a tube from four to five inches in length, three-quarters 
of an inch in diameter, extending from the cricoid cartilage of the larynx 
to the third dorsal vertebra, where it divides into the right and left bronchi. 
It is composed of a series of cartilaginous rings, which extend about two- 
thirds around its circumference, the posterior third being occupied by 
fibrous tissue and non-striated muscular fibres which are capable of dimin- 
ishing its calibre. 
The trachea is covered externally by a tough, fibro-elastic membrane, 
and internally by mucous membrane, lined by columnar ciliated epithelial 
cells. The cilia are always waving from within outward. When the 
two bronchi enter the lungs they divide and subdivide into numerous and 
smaller branches, which penetrate the lung in every direction until they 
finally terminate in the pulmonary lobules. 
As the bronchial tubes become smaller their walls become thinner; the 
cartilaginous rings disappear, but are replaced by irregular angular plates 
of cartilage; when the tube becomes less than the of an inch in di- 
ameter they wholly disappear, and the fibrous and mucous coats blend 
together, forming a delicate, elastic membrane, with circular muscular 
fibres. 
The Lungs occupy the cavity of the thorax, are conical in shape, of a 
pink color and a spongy texture. They are composed of a great number 
of distinct lobules, the pulmonary lobules, connected together by inter- 
lobular connective tissue. These lobules vary in size, are of an oblong 
shape, and are composed of the ultimate ramifications of the bronchial 
tubes, within which are contained the air vesicles or cells. The walls of 
the air vesicles, exceedingly thin and delicate, are lined internally by a 
layer of tessellated epithelium, externally covered by elastic fibres, which 
give the lungs their elasticity and distensibility. 
The Venous Blood is distributed to the lungs for aeration by the 
pulmonary artery, the terminal branches of which form a rich plexus of 
capillary vessels surrounding the air cells; the air and blood are thus 
brought into intimate relationship, being separated only by the delicate 
walls of the air cells and capillaries. 
The Pleura. Each lung is surrounded by a closed serous membrane, 
the pleura, one layer of which, the visceral, is reflected over the lung, the 46 
HUMAN PHYSIOLOGY. 
other, the parietal, reflected over the wall of the thorax; between the two 
layers is a small amount of fluid which prevents friction during the play of 
the lungs in respiration. 
The lungs are nourished by blood from the bronchial arteries ramifying 
in the walls of the bronchial' tubes and interlobular connective tissue. 
Respiratory movements. The movements of respiration are two, 
and consist of an alternate dilation and contraction of the chest, known as 
inspiration and expiration. 
1. Inspiration is an active process, the result of the expansion of the 
thorax, whereby air is introduced into the lungs. 
2. Expiration is a partially passive process, the result of the recoil of 
the elastic walls of the thorax, and the recoil of the elastic tissue of the 
lungs, whereby the carbonic acid is expelled. 
In Inspiration the chest is enlarged by an increase in all its diameters, 
viz:— 
1. The vertical is increased by the contraction and descent of the 
diaphragm when it approximates a straight line. 
2. The antero-posterior and transverse diameters are increased by the 
elevation and rotation of the ribs upon their axes. 
In ordinary tranquil inspiration the muscles which elevate the ribs and 
thrust the sternum forward, and so increase the diameters of the chest, are 
the external intercostals, running from above downward and forward, the 
sternal portion of the internal intercostals and the levatores costarum. 
In the extraordinary efforts of inspiration certain auxiliary muscles are 
brought into play, viz: the sterno-mastoid, pectorales, serratus magnus, 
which increase the capacity of the thorax to its utmost limit. 
In Expiration the diameters of the chest are all diminished, viz : 
1. The vertical, by the ascent of the diaphragm. 
2. The antero-posterior, by a depression of the ribs and sternum. 
In ordinary tranquil expiration the muscles which depress the ribs and 
sternum, and thus diminish the diameter of the chest, are the internal inter- 
costals, the infra-costals and the triangularis sterni. 
In the extraordinary efforts of expiration certain auxiliary muscles are 
brought into play, viz: the abdominal and sacro-lumbalis muscles, which 
diminish the capacity of the thorax to its utmost limit. 
Expiration is aided by the recoil of the elastic tissue of the lungs and 
ribs and the pressure of the air. 
Movements of the Glottis. At each inspiration the rima glottidis is 
dilated by a separation of the vocal cords, produced by the contraction of RESPIRATION. 
47 
the crico-arytenoid muscles so as to freely admit the passage of air into the 
lungs; in expiration they fall passively together, but do not interfere with 
the exit of the air from the chest. 
Nervous Mechanism of Respiration. The movements of respira- 
tion are involuntary and reflex, and are under the control of the medulla 
oblongata. 
This centre may be stimulated— 
1. Directly, by the condition of the blood. An increase of carbonic acid 
or a diminution of oxygen in the blood causes an acceleration of the 
respiratory movements; the reverse of these conditions causes a diminution 
of the respiratory movements. 
2. Indirectly, by reflex action. The medulla may be excited to action 
through the pneumogastric nerve, by the presence of carbonic acid in the 
lungs irritating its terminal filaments; through the fifth nerve, by irrita- 
tion of the terminal branches; and through the nerves of general sensibility. 
In either case this centre reflects motor impulses to the respiratory muscles 
through the phrenic, intercostals, inferior laryngeal and other nerves. 
Types of Respiration. The abdominal type is most marked in young 
children, irrespective of sex; the respiratory movements being effected by 
the diaphragm and abdominal muscles. 
In the superior costal type, exhibited by the adult female, the respiratory 
movements are more marked in the upper part of the chest, from the istto 
the 7th ribs, permitting the uterus to ascend in the abdomen during preg- 
nancy without interfering with respiration. 
In the inferior costal type, manifested by the male, the movements are 
largely produced by the muscles of the lower portion of the chest, from the 
7th rib downward, assisted by the diaphragm. 
The respiratory movements vary according to age, sleep and exercise, 
being most frequent in early’life, but averaging 20 per minute in adult life. 
They are diminished by sleep and increased by exercise. There are about 
four pulsations of the heart to each respiratory act. 
During inspiration two sounds are produced; the one, heard in the 
thorax, in the trachea and larger bronchial tubes, is tubular in character; 
the other, heard in the substance of the lungs, is vesicular in character. 
AMOUNT OF AIR EXCHANGED IN RESPIRATION, AND CAPACITY 
OF LUNGS. 
The Tidal or breathing volume of air, that which passes in and out of 
the lungs at each inspiration and expiration, is estimated at from 20 to 30 
cubic inches. 48 
HUMAN PHYSIOLOGY. 
The Complemcntal ah- is that amount which can be taken into the lungs 
by a forced inspiration, in addition to the ordinary tidal volume, and 
amounts to about no cubic inches. 
The Reserve air is that which usually remains in the chest after the 
ordinary efforts of expiration, but which can be expelled by forcible expira- 
tion. The volume of reserve air is about ioo cubic inches. 
The Residual air is that portion which remains in the chest and cannot 
be expelled after the most forcible expiratory efforts, and which amounts, 
according to Dr. Hutchinson, to about ioo cubic inches. 
The Vital Capacity of the chest indicates the amount of air that can 
be forcibly expelled from the lungs after the deepest possible inspiration, 
and is an index of an individual’s power of breathing in disease and pro- 
longed severe exercise. The combined amounts of the tidal, the comple- 
mental and reserve air, 230 cubic inches, represents the vital capacity of an 
individual 5 feet 7 inches in height. The vital capacity varies chiefly with 
stature. It is increased 8 cubic inches for every inch in height above this 
standard, and diminishes 8 cubic inches for each inch below it. 
The Tidal Volume of air is carried only into the trachea and larger 
bronchial tubes by the inspiratory movements. It reaches the deeper 
portions of the lungs in obedience to the law of diffusion of gases, which is 
inversely proportionate to the square root of their densities. 
The ciliary action of the columnar cells lining the bronchial tubes also 
assists in the interchange of the air and carbonic acid. 
The entire volume of air passing in and out of the thorax in 24 hours is 
subject to great variation, but is estimated by Dr. Smith at 686,000 cubic 
inches, or 397 cubic feet. 
Composition of Air: Oxygen, 20.81 parts; nitrogen, 79.19, forming a 
mechanical mixture in which exist traces of carbonic acid and watery 
vapor. 
The changes in the air effected by respiration are— 
Loss of oxygen, to the extent of 4.782 per cent. 
Gain of carbonic acid, to the extent of 4.35 per cent. 
Increase of watery vapor and organic matter. 
Elevation of temperature. 
Increase and at times decrease of nitrogen. 
Gain of ammonia. 
The total quantity of oxygen withdrawn from the air and consumed by 
the body in 24 hours amounts to 18 cubic feet; to obtain this quantity 400 
cubic feet of pure air are necessary. RESPIRATION. 
49 
The quantity of carbonic acid exhaled in 24 hours varies greatly. Dr. 
Smith computed it at 24.208 cubic inches, containing 7.144 oz. of pure 
carbon. It is increased by muscular exercise; nitrogenous food ; tea, 
coffee and rice; age, and by muscular development; decreased by a 
lowering of temperature; repose; gin and brandy, and a dry condition of 
the air. 
Condition of the Gases in the Blood. 
Oxygen is absorbed from the lungs into the arterial blood by the color- 
ing matter, hcemoglobin, with which it exists in a state of loose combina- 
tion, and is disengaged during the process of nutrition. 
Carbonic acid, arising in the tissues, is absorbed into the blood in conse- 
quence of its alkalinity; where it exists in a state of simple solution and 
also in a state of feeble combination with soda and potassa, forming the 
bicarbonates; it is liberated by pneumic acid in the pulmonary tissue. 
Nitrogen is simply in solution in the plasma. 
The amount of watery vapor thrown off from the lungs daily is about 
one pound, with which is mingled organic matter and ammonia. 
Changes in the Blood during Respiration. 
As the blood passes through the lungs it is changed in color, from the 
dark purple hue of venous blood to the bright scarlet of arterial blood. 
The heterogeneous composition of venous blood is exchanged for the 
uniform composition of the arterial. 
It gains oxygen and loses carbonic acid. 
Its coagulability is increased. Temperature is diminished. 
Asphyxia. If the supply of oxygen to the lungs be diminished and 
the carbonic acid retained in the blood, the normal respiratory movements 
cease, the condition of asphyxia ensues, which soon terminates in death. 
The phenomena of asphyxia are, violent spasmodic action of the respira- 
tory muscles, attended by convulsions of the muscles of the extremities, 
engorgement of the venous system, lividity of the skin, abolition of 
sensibility and reflex action, and death. 
The cause of death is a paralysis of the heart, from over distention by 
blood. The passage of the blood through the capillaries is prevented by 
contraction of the smaller arteries from irritation of the vaso-motor centre. 
The heart is enfeebled by a want of oxygen and inhibited in its action by 
the inhibitory centres. 50 
HUMAN PHYSIOLOGY. 
ANIMAL HEAT. 
The Functional Activity of all the organs and tissues of the body is 
attended by the evolution of heat, which is independent, for the most part, 
of external conditions. Heat is a necessary condition for the due perform- 
ance of all vital actions ; though the body constantly loses heat by radia- 
tion and evaporation, it possesses the capability of renewing it and 
maintaining it at a fixed standard. The normal temperature of the body 
in the adult, as shown by means of a delicate thermometer placed in the 
axilla, ranges from 97.250 Fahr. to 99.50 Fahr., though the mean normal 
temperature is estimated by Wunderlich at 98.6° Fahr. 
The temperature varies in different portions of the body, according to 
the degree to which oxidation takes place; being the highest in the muscles 
during exercise, in the brain, blood, liver, etc. 
The conditions which produce variations in the normal tempera- 
ture of the body are: age, period of the day, exercise, food and drink, 
climate, season and disease. 
Age. At birth the temperature of the infant is about i° F. above that 
of the adult, but in a few hours falls to 95.5° F., to be followed in the 
course of 24 hours by a rise to the normal or a degree beyond. During 
childhood the temperature approaches that of the adult; in aged persons 
the temperature remains about the same, though they are not as capable 
of resisting the depressing effects of external cold as adults. A diurnal 
variation of the temperature occurs from 1.8° F. to 3.6° F. (Jiirgensen); 
the maximum occurring late in the afternoon, from 4 to 9 p. M., the 
minimum, early in the morning, from x to 7 A. M. 
Exercise.. The temperature is raised from i° to 2° F. during active con- 
tractions of the muscular masses, and is probably due to the increased 
activity of chemical changes ; a rise beyond this point being prevented by 
its diffusion to the surface, consequent on a more rapid circulation, radia- 
tion, more rapid breathing, etc. 
Food and drink. The ingestion of a hearty meal increases the tempera- 
ture but slightly; an absence of food, as in starvation, produces a marked 
decrease. Alcoholic drinks, in large amounts, in persons unaccustomed to 
their use, cause a depression of the temperature amounting from i° to 20 
F. Tea causes a slight elevation. 
External temperature. Long continued exposure to cold, especially if 
the body is at rest, diminishes the temperature from i° to 20 F., while ex- 
posure to a great heat slightly increases it. 
Disease frequently causes a marked variation in the normal temperature ANIMAL HEAT. 
51 
of the body, rising as high as 107° F. in typhoid fever, and 105° F. in pneu- 
monia; in cholera it falls as low as 8o° F. Death usually occurs when the heat 
remains high and persistent, from 1060 to no° F.; the increase of heat in 
disease is due to excessive production rather than to diminished elimination. 
The source of heat is to be sought for in the chemical combinations 
taking place during the general process of nutrition, and the amount of 
its production is in proportion to the activity of the internal changes. 
Every contraction of a muscle, every act of secretion, each exhibition 
of nerve force, is accompanied by a change in the chemical composition of 
the tissues and an evolution of heat. The reduction of the disintegrated 
tissues to their simplest form by oxidation ; the combination of the oxygen 
of the inspired air with the carbon and hydrogen of the blood and tissues, 
results in the formation of carbonic acid and water and the generation of a 
large amount of heat. 
Certain elements of the food, particularly the non-nitrogenized sub- 
stances, undergo oxidation without taking part in the formation of the 
tissues, being transformed into carbonic acid and water, and thus increase 
the sum of heat in the body. 
Heat-producing Tissues. All the tissues of the body add to the 
general amount of heat, according to the degree of their activity. But 
special structures, on account of their mass and the large amount of blood 
they receive, are particularly to be regarded as heat producers ; e. g. :— 
1. During mental activity the brain receives nearly one-fifth of the 
entire volume of blood, and the venous blood returning from it is charged 
with waste matters, and its temperature is increased. 
2. The muscular tissue, on account of the many chemical changes 
occurring during active contractions, must be regarded as the chief heat- 
producing tissue. 
3. The secreting glands, during their functional activity, add largely to 
the amount of heat. 
Of the entire quantity of heat generated in the body, it is estimated 
that only a small proportion is utilized, as five-sixths escape by radiation 
and evaporation, the remaining one-sixth being utilized in keeping the 
body at the normal temperature standard, 98.6° F., and in the production 
of muscular force. 
The body loses heat by radiation and evaporation from the general cuta- 
neous surface, the respiratory passages and by the urine and faeces. About 
75 per cent, of all the heat lost escapes from the skin. In passing through 
the lungs the temperature of the blood is lowered by about i° Fahr. 52 
HUMAN PHYSIOLOGY. 
The nervous system influences the production of heat in a part, by 
increasing the amount of blood going through it by its action upon the 
vaso-motor nerves. Whether there exists a special heat centre has not 
been satisfactorily determined, though this is probable. 
The Process of Secretion consists in the separation of materials from 
the blood, which are either to be again utilized to fulfill some special pur- 
pose in the economy, or are to be removed from the body as excrementi- 
tious matter; in the former case they constitute the secretions, in the latter, 
the excretions. 
The materials which enter into the composition of the secretions are de- 
rived from the nutritive principles of the blood, and require special organs, 
e. g., gastric glands, mammary glands, etc., for their proper elaboration. 
The materials which compose the excretions pre-exist in the blood, and 
are the results of the activities of the nutritive process; if retained within 
the body they exert a deleterious influence upon the composition of the 
blood. 
Destruction of a secreting gland abolishes the secretion peculiar to it, 
and it cannot be formed by any other gland; but among the excreting 
organs there exists a complementary relation, so that if the function of one 
organ be interfered with, another performs it, to a certain extent. 
SECRETION. 
CLASSIFICATION OF THE SECRETIONS. 
Serous fluids. 
Synovial fluid. 
Aqueous humor of the eye. 
PERMANENT FLUIDS. 
Vitreous humor of the eye. 
Fluid of the labyrinth of the internal 
ear. 
Cerebro-spinal fluid. 
Mucus. 
Sebaceous matter. 
Cerumen (external meatus). 
Meibomian fluid. 
Milk and colostrum. 
Tears. 
Saliva. 
TRANSITORY FLUIDS. 
Gastric juice. 
Pancreatic juice. 
Secretion from Brunner’s glands. 
Secretion from Lieberkiihn’s glands. 
Secretion from follicles of the large 
intestine. 
Bile (also an excretion). 
EXCRETIONS. 
Perspiration and the secretion of 
the axillary glands. 
Urine. 
Bile (also a secretion). SECRETION. 
53 
FLUIDS CONTAINING FORMED ANATOMICAL ELEMENTS. 
Seminal fluid, containing spermatozoids. Fluid of the Graafian follicles. 
The essential apparatus for secretion is a delicate, homogeneous, 
structureless membrane, on one side of which, in close contact, is a capillary 
plexus of blood vessels, and on the other side a layer of cells whose physio- 
logical function varies in different situations. 
Secreting organs may be divided into membranes and glands. 
Serous membranes usually exist as closed sacs, the inner surface of 
which is covered by pale, nucleated epithelium, containing a small amount 
of secretion. 
The serous membranes are the pleura,peritoneum,pericardium, synovial 
sacs, etc. 
The serous fluids are of a pale amber color, somewhat viscid, alkaline, 
coagulable by heat, and resemble the serum of the blood; their amount is 
but small; the pleural varies from 4 to 7 drachms; the peritoneal from 1 
to 4 ounces; the pericardial from 1 to 3 drachms. 
The synovialfluid is colorless, alkaline, and extremely viscid, from the 
presence of synovine. 
The function of serous fluids is to moisten the opposing surfaces, so as 
to prevent friction during the play of the viscera. 
The mucous membranes are soft and velvety in character, and line the 
cavities and passages leading to the exterior of the body, e. g., the gastro- 
intestinal, pulmonary and genito-urinary. They consist of a primary 
basement membrane covered with epithelial cells, which, in some situa- 
tions, are tessellated, in others, columnar. 
Mucus is a pale, semi-transparent, alkaline fluid, containing epithelial 
cells and leucocytes. It is composed, chemically, of water, an albumin- 
ous principle, mucosine, and mineral salts; the principal vari eties are nasal, 
bronchial, vaginal and urinary. 
Secreting Glands are formed of the same elements as the secreting 
membranes; but instead of presenting flat surfaces, are involuted, forming 
tubules, which may be simple follicles, e. g., mucous, uterine or intestinal; 
or compound follicles, e. g., gastric glands, mammary glands; or racemose 
glands, e. g., salivary glands and pancreas. They are composed of a 
basement membrane, enveloped by a plexus of blood vessels, and are lined 
by epithelial and true secreting cells, which in different glands possess the 
capability of elaborating elements characteristic of their secretions. 
In the production of the secretions two essentially different processes 
are concerned, viz.:— 54 
HUMAN PHYSIOLOGY. 
1. Chemical. The formation and elaboration of the characteristic organic 
ingredients of the secreting fluids, e. g., pepsin, pancreatin, takes place 
during the intervals of glandular activity, as a part of the general function 
of nutrition. They are formed by the cells lining the glands, and can 
often be seen in their interior with the aid of the microscope, e. g., bile in 
the liver cells, fat in the cells of the mammary gland. 
2. Physical. Consisting of a transudation of water and mineral salts 
from the blood into the interior of the gland. 
During the intervals of glandular activity, only that amount of blood 
passes through the gland sufficient for proper nutrition; when the gland 
begins to secrete, under the influence of an appropriate stimulus, the blood 
vessels dilate and the quantity of blood becomes greatly increased beyond 
that flowing through the gland during its repose. 
Under these conditions a transudation of water and salts takes place, 
washing out the characteristic ingredients, which are discharged by the 
gland ducts. The discharge of the secretions is intermittent; they are 
retained in the glands until they receive the appropriate stimulus, when 
they pass into the larger ducts by the vis-a-tergo, and are then discharged 
by the contraction of the muscular walls of the ducts. 
The activity of glandular secretion is hastened by an increase in the 
blood pressure and retarded by a diminution. 
The nervous centres in the medulla oblongata influence secretion, (i) by 
increasing or diminishing the amount of blood entering a gland; (2) by 
exerting a direct influence upon the secreting cells themselves, the centres 
being excited by reflex irritation, mental emotion, etc. 
The Mammary Glands secrete the milk, and undergo at different 
periods of life remarkable changes in size and structure. Though rudi- 
mentary in childhood, they gradually increase in size as the young female 
approaches puberty. 
The gland presents, at its convexity, a small prominence of skin, the 
nipple, surrounded by an areola of a deeper tint. It is covered anteriorly 
by a layer of adipose tissue and posteriorly by a fibrous structure which 
attaches it loosely to the pectoralis muscle. 
During utero-gestation the mammae become large, firm, well-developed 
and lobulated; the areola becomes darker and the veins more prominent. 
In the intervals of lactation the glands gradually shrink in size to their 
original condition, undergo involution, and become non-secreting organs. 
Structure of the Mammae. The mamma is a conglomerate gland, 
MAMMARY GLANDS. MILK. 
55 
consisting of a number of lobes, from 15 to 20 in number, each of which is 
subdivided into lobules made up of gland vesicles or acini. The ducts 
which convey the secretion to the exterior, the lactiferous ducts, open by 
15 to 20 orifices upon the surface of the nipple, at the base of which they 
are dilated to form little reservoirs in which the milk collects during the 
periods of active secretion. 
The walls of the lacteal duct consist of white, fibrous tissue, and non- 
striated muscular fibres, lined by short columnar cells, which disappear 
during active lactation. The ducts measure about the of an inch in 
diameter; as they pass into the substance of the gland, each duct divides 
into a number of branches, which are distributed to distinct lobules and 
terminate in the acini. 
An acinus is made up of a number of vesicles composed of a homoge- 
neous membrane, lined by pavement epithelium. The gland vesicles are 
held together by white, fibrous tissue, which unites the lobules into lobes. 
MILK 
Milk has a pale, blue color, is almost inodorous, of a sweetish taste, an 
alkaline reaction, and a specific gravity varing from 1.025 t0 1.04.6. 
Examined microscopically it is seen to contain an immense number of 
globules, measuring the xuihjT! °f an inch in diameter, suspended in a clear 
fluid; these are the milk globules, formed of a small mass of oily matter 
covered by a layer of albumen. 
The quantity of milk secreted by the human female in 24 hours, during 
the period of lactation, is about two to three pints; the quantity removed 
by the infant from a full breast at one time being about two ounces. 
COMPOSITION OF MILK. 
Water 890.00 
Proteids, including casein and serum albumen 35 .oo 
Fatty matter (butter) 25.00 
Sugar (lactose) with extractives 48.00 
Salts 2.00 
1000.00 
Casein is the nutritive principle of milk, and constitutes its most import- 
ant ingredient. It is held in solution by an alkali, but upon the addition 
of an acid it undergoes coagulation, passing into a semi-solid form. The 
presence of lactic acid, resulting from a transformation of milk sugar, 
causes spontaneous coagulation to take place. 
The Fatty matter is more or less solid at ordinary temperature, and con- 56 
HUMAN PHYSIOLOGY. 
sists of margarine and oleine; when subjected to the churning process the 
globules run together and form a coherent mass, the butter. 
When milk is allowed to stand for a varying length of time the fat glob- 
ules rise to the surface, forming a layer more or less thick, the crea?n. 
Milk sugar or lactose is an important ingredient in the food of the young 
child; it is readily transformed into lactic acid in the presence of nitro- 
genized ferments. 
Influences modifying the secretion. During lactation there is a 
demand for an increased amount of fluid, and if not supplied, the amount 
of milk secreted is diminished. Good food in sufficient quantity is neces- 
sary for the proper elaboration of milk, though no particular article influ- 
ences its production. 
Mental emotion at times influences the character of the milk, decreasing 
the amount of its different constituents. 
Mechanism of Secretion. The water and salts pre-exist in the blood 
and pass into the gland vesicles by osmosis. The casein, fatty matter and 
sugar appear only in the mammary gland, but the mechanism of their for- 
mation is not understood. 
Colostrum is a yellowish, opaque fluid, formed in the mammary glands 
towards the latter period of utero-gestation ; it consists of water, albumen, 
fat, sugar and salts, and acts as a laxative to the newly born infant. 
VASCULAR OR DUCTLESS GLANDS. 
The Vascular Glands are regarded as possessing the power of acting 
upon certain elements of the food and aiding the process of sanguinifi- 
cation; of modifying the composition of the blood as it flows through their 
substance, by some act of secretion. 
The vascular glands are the spleen, suprarenal capsules, thyroid and 
thymus glands. 
The Spleen is about 5 inches in length, 6 ounces in weight, of a dark 
bluish color, and situated in the left hypochondriac region. It is covered 
externally by a reflection of the peritoneum, beneath which is the proper 
fibrous coat, composed of areolar and elastic tissue and non-striated 
muscular fibres. From the inner surface of the fibrous envelope processes 
or trabeculae are given off, which penetrate the substance of the gland, 
forming a network, in the meshes of which is contained the spleen pulp. 
The splenic artery divides into a number of branches, some of which, 
when they become very minute, pass directly into veins, while others 
terminate in true capillaries. VASCULAR OR DUCTLESS GLANDS. 
57 
As the capillary vessels ramify through the substance of the gland their 
walls frequently disappear and the blood passes from the arteries into the 
veins through lacuna (Gray). 
The splenic or Malpighian corpuscles are small bodies, spherical or ovoid 
in shape, the of an inch in diameter, situated upon the sheaths of the 
small arteries. They consist of a delicate membrane, containing a semi- 
fluid substance composed of numerous small cells resembling lymph cor- 
puscles. The spleen pulp is a dark red, semi fluid substance, of a soft 
consistence, contained in the meshes of the trabeculae. In it are found 
numerous corpuscles, like those observed in the Malpighian bodies, blood 
corpuscles in a natural and altered condition, nuclei and pigment granules. 
Function of the Spleen. Probably influences the preparation of the 
albuminous food for nutrition; during digestion the spleen becomes larger, 
its contents are increased in amount, and after digestion it gradually dimin- 
ishes in size, returning to the normal condition. 
The red corpuscles are here disintegrated, after having fulfilled their 
function in the blood; the splenic venous blood containing relatively a 
small quantity. 
The white corpuscles appear to be increased in number, the blood of the 
splenic vein containing an unusually large proportion. 
The spleen serves also as a reservoir for blood when the portal circula- 
tion becomes obstructed. 
The nervous system controls the enlargement of the spleen; division of 
the nerve produces dilatation of the vessels, stimulation contracts them. 
The Supra-renal Capsules are triangular, flattened bodies, situated 
above the kidney. They are invested by a fibrous capsule sending in 
trabeculae, forming the framework. The glandular tissue is composed of 
two portions, a cortical and medullary. The cortical being made up of 
small cylinders lined by cells and containing an opaque mass, nuclei and 
granular matter. The medullary consists of a fibrous network containing 
in the alveoli nucleated protoplasm. 
The Thyroid gland consists of a fibrous stroma, containing ovoid 
closed sacs, measuring on the average of a inch, formed of a delicate 
membrane lined by cells; the contents of the sacs consist of yellowish 
albuminous fluid. 
The Thymus gland is most developed in early life and almost disap- 
pears in the adult. It is divided by processes of fibrous tissue into lobules, 
and these again into follicles which contain lymphoid corpuscles. 
The functions of the vascular glands appear to be the more complete 58 
HUMAN PHYSIOLOGY. 
elaboration of the blood necessary for proper nutrition; they are most 
highly developed during infancy and embryonic life, when growth and 
development are most active. 
The Principal Excrementitious Fluids discharged from the body 
are the urine, perspiration and bile; they hold in solution principles of 
waste which are generated during the activity of the nutritive process, and 
are the ultimate forms to which the organic constituents are reduced in 
the body. They also contain inorganic salts. 
The Urinary Apparatus consists of the kidneys, ureters and bladder. 
EXCRETION. 
KIDNEYS. 
The Kidneys are the organs for the excretion of urine; they resemble 
a bean in shape, are from four to five inches in length, two in breadth, and 
weigh from four to six ounces. 
They are situated in the lumbar region, one on each side of the verte- 
bral column, behind the peritoneum, and extend from the nth rib to the 
crest of the ilium; the anterior surface is convex, the posterior concave, 
and presents a deep notch, the kilum. 
The kidney is surrounded by a thick layer of fat, beneath which is the 
fibrous coat, thin and smooth, composed of dense white fibrous tissue with 
which are intermingled elastic fibres. It is adherent to the surface of the 
organ, but can easily be removed by dissection. 
The Substance of the Kidney is dense, but friable; upon making 
a longitudinal section, and dividing it, there is presented a cavity, the 
pelvis, lined by the proper fibrous coat and occupied by the expanded 
portion of the ureter. 
The kidney exhibits two structures, viz.:— 
1. An external or cortical portion, about *4 of an inch in diameter, of a 
reddish color, and somewhat granular. 
2. An internal or medullary portion, of a dark red color, arranged in 
the form of pyramids, the bases of which are directed towards the cortical 
portion, and the apices toward the pelvis, into which they project, and are 
covered by the calyces. 
The Cortical portion of the kidney consists of a delicate matrix con- 
taining an immense number of tubules, having a markedly convoluted 
appearance, and interlacing in every direction (the tubules of Ferrein). 
Throughout its structure are numerous ovoid bodies, the Malpighian bodies, 
which are the flask-like terminations of the convoluted tubules; these tubes KIDNEYS. 
59 
are composed of a delicate homogeneous membrane lined by nucleated 
cells. After pursuing a most intricate course in the cortical portion, they 
become narrower and form loops which dip into the pyramidal portion 
(Henle’s tubules), returning upon themselves, to finally terminate in the 
straight tubes of the pyramids. 
The Malpighian bodies, the dilated extremities of the convoluted tubes, 
consist of a little sac, which is ovoid in shape, measuring about the 
of an inch in diameter, and contains a tufted mass of minute blood vessels, 
over the surface of which is reflected a layer of cells. 
Medullary Substance. The conical masses, th e. pyramids of Malpi- 
ghi, consist of a number of straight tubes, which commence at the apex by 
from io to 20 openings; and as they pass towards the cortical portion, they 
divide and subdivide at acute angles, until a large mass of tubes is pro- 
duced. These tubes are on the average about of an inch in diameter, 
and composed of a thin, but firm, elastic, structureless membrane, lined by 
polygonal nucleated cells, which reduce the diameter of the lumen of the 
tube about two-thirds ; these are the straight tubes of Bellini. 
Blood vessels of the Kidney. The renal artery is of large size and 
enters the organ at the hilum; it divides into several large branches, 
which penetrate the substance of the kidney, between the pyramids, at 
the base of which they form an anastomosing plexus, which completely 
surrounds them. From this plexus vessels follow the straight tubes.towards 
the apex, while others entering the cortical portion, divide into small twigs 
which enter the Malpighian body and form a mass of convoluted vessels, 
the glomerulus. After circulating through the Malpighian tuft the blood 
is gathered together by two or three small veins, which again subdivide 
and form a fine capillary plexus, which envelops the convoluted tubules ; 
from this plexus the veins converge to form the emulgent vein, which 
empties into the vena cava. 
The Nerves of the kidney follow the course of the blood vessels and 
are derived from the renal plexus. 
The Ureter is a membranous tube, situated behind the peritoneum, 
about the diameter of a goose quill, 18 inches in length, and extends from 
the pelvis of the kidney to the base of the bladder, which it perforates in 
an oblique direction. It is Composed of 3 coats, fibrous, muscular and 
mucous. 
The Bladder is a temporary reservoir for the reception of the urine 
prior to its expulsion from the body ; when fully distended it is ovoid in 
shape, and holds about one pint. It is composed of four coats, serous, 60 
HUMAN PHYSIOLOGY. 
muscular, the fibres of which are arranged longitudinally and circularly, 
areolar and mucous. The orifice of the bladder is controlled by the 
sphincter vesicce, a muscular band, about half an inch in width. 
As soon as the urine is formed it passes through the tubuli urini- 
feri into the pelvis, and from thence through the ureters into the bladder, 
which it enters at an irregular rate. Shortly after a meal, after the ingestion 
of large quantities of fluid, and after exercise, the urine flows into the bladder 
quite rapidly, while it is reduced to a few drops during the intervals of 
digestion. It is prevented from regurgitating into the ureters on account 
of the oblique direction they take between the mucous and muscular coats. 
Nervous Mechanism of Urination. When the urine has passed into 
the bladder it is there retained by the sphincter .vesicse muscle kept in a 
state of tonic contraction by the action of a nerve centre in the lumbar 
region of the spinal cord. This centre can be inhibited and the sphincter 
relaxed, either reflexly, by impressions coming through sensory nerves from 
the mucous membrane of the bladder, or directly, by a voluntary impulse 
descending the spinal cord. When the desire to urinate is experienced, 
impressions made upon the vesical sensory nerves are carried to the centres 
governing the sphincter and detrusor urince muscles and to the brain. If 
now the act of urination is to take place, a voluntary impulse, originating 
in the brain, passes down the spinal cord and still further inhibits the 
sphincter vesicse centre, with the effect of relaxing the muscle, and of 
stimulating the centre governing the detrusor muscle, with the effect of 
contracting the muscle and expelling the urine. If the act is to be sup- 
pressed voluntary impulses inhibit the detrusor centre and possibly stimu- 
late the sphincter centre. 
Thqgenito-spinal centre controlling these movements is situated in that 
portion of the spinal cord corresponding to the origin of the 3d, 4th and 
5th sacral nerves. 
URINE. 
Normal Urine is of a pale yellow or amber color, perfectly transpa- 
rent, with an aromatic odor, an acid reaction, a specific gravity of 1.020, 
and a temperature when first discharged of ioo° Fahr. 
The color varies considerably in health, from a pale yellow to a brown 
hue, due to the presence of the coloring matter, urobilin or urochrome. 
The transparency is diminished by the presence of mucus, the calcium 
and magnesium phosphates and the mixed urates. 
The reaction is slightly acid, caused by the acid phosphate of sodium. 
After standing for a short time, an increased acidity is observed, due to an URINE, 
61 
acid fermentation, from the presence of mucus. The urea is converted 
into ammonium carbonate, giving rise to a strong ammoniacal odor. 
The specific gravity varies from 1.010 to 1.025. 
The quantity of urine excreted in 24 hours is between 40 and 50 fluid 
ounces, but ranges above and below this standard. 
The odor is characteristic, and caused by the presence of taurylic and 
phenylic acids, but is influenced by vegetable foods and other substances 
eliminated by the kidneys. 
Water 967. 
Urea 14.230 
COMPOSITION OF URINE. 
Other nitrogenized crystalline bodies, uric acid, prin- 
cipally in the form of alkaline urates. 
Creatin, creatinin, xanthin, hypoxanthin. 
Hippuric acid, leucin, tyrosin, taurin, cystin, all in 
small amounts, and not constant. 
Mucus and pigment. 
io.63S 
Salts :— 
Inorganic, principally sodium and potassium sulphates,' 
phosphates and chlorides, with magnesium and cal- 
cium phosphates, traces of silicates and chlorides. 
Organic; lactates, hippurates, acetates, formates, 
which appear only occasionally. 
8-135 
Sugar a trace. 
Gases (nitrogen and carbonic acid principally). 
1000.00 
The Average Quantity of the principal constituents excreted in 24 
hours is as follows:— 
Water 52 fluid oz. 
Urea 512.4 grains. 
Uric acid 8.5 “ 
Phosphoric acid 45.0 “ 
Sulphuric acid 31.11 “ 
Inorganic salts..., 323-25 “ 
Lime and magnesia 6.5 “ 
To Determine the amount of solid matters in any given amount of 
urine, multiply the last two figures of the specific gravity by the coefficient 
of Hseser, 2.33; e.g., in 1000 grains of urine having a specific gravity 1.022, 
there are contained 22 X 2-33 = 51-26 grains of solid matter. 62 
HUMAN PHYSIOLOGY. 
The Elimination of the urinary constituents is accomplished by the 
two processes of filtration and secretion. 
1. By Filtration the water and mineral salts are removed from the 
blood, and takes place, for the most part, in the Malpighian corpuscles, by 
the process of osmosis. The amount of these constituents eliminated 
varies with the pressure of blood in the renal arteries. All of the agen- 
cies which increase the general blood pressure increase the quantity of 
urine. 
Season. In summer, while the capillary vessels of the skin are dilated, 
and perspiration is abundant, there is a diminished blood pressure, and a 
consequent diminution in the amount of urine ; in winter the reverse takes 
place. 
During sleep the renal excretion is diminished, but increased in the 
morning hours, and especially after the ingestion of hearty meals. 
The nervous system influences the secretion of urine. Irritation of the 
medulla oblongata, a little above the origin of the pneumogastric and 
auditory nerves, increases the quantity; division of the renal nerves 
destroys the nutrition of the kidney, and thus interferes with the elimina- 
tion of the urine. Mental emotion, fear, anxiety, etc., increase the amount 
secreted. 
2. Secretion. While it is established that the Malpighian corpuscles 
permit the filtration of water and salts, it has also been shown that the 
renal epithelial cells lining the convoluted tubes are the agencies by which 
the solid matters, as urea, creatin, etc., are removed from the blood, by a 
process of true secretion, which is independent of blood pressure and 
caused by the presence of these ingredients in the blood. 
Urea is the most important of the organic constituents of the urine. It 
is a colorless, neutral substance, crystallizing in four-sided prisms, soluble 
in boiling alcohol and water; when subjected to prolonged boiling it is 
decomposed, with the production of ammonium carbonate. 
Urea is not formed in the kidneys, but pre-exists in the blood. 
The Amount of Urea excreted in 24 hours is estimated at about 500 
grains; it is increased during the waking hours, by an animal diet, and by 
prolonged muscular exertion; diminished during sleep and by non- 
„nitrogenized food. 
Source. Urea results from an imperfect oxidation of the albuminous 
principles of the food, and from a disintegration of the organic constituents 
of the tissues. 
Uric acid, or lithic acid, is a constant ingredient of the urine; the LIVER 
63 
amount excreted daily is about 8 grains; it is increased by nitrogenized, 
decreased by non-nitrogenized food. It exists in the urine in a free state, 
and as the urate of soda. It arises from the disassimilation of albuminous 
compounds, and when secreted in excess is deposited in a crystalline form, 
as a brown or “ brick-red ” sediment, with the sodium and ammonium 
urates. 
Creatin is a colorless, transparent substance, crystallizing in prisms; 
found in blood, kidneys, and muscular tissue; by boiling in acid solutions 
it is transformed into 
Creatinin, which resembles creatin chemically. It is soluble in water 
and alcohol, and crystallizes in colorless prisms. About 15 grains are 
excreted daily. 
The Earthy phosphates are insoluble in water but held in solution in the 
urine by the acid reaction. If the urine becomes alkaline, they are de- 
posited copiously, and yet may not be increased in quantity; from 15 to 25 
grains are excreted in 24 hours. The sulphates are those of sodium and 
potassium; they are very soluble and do not appear as a precipitate; the 
average quantity excreted in 24 hours is about 60 grains. 
Abnormal ingredients appear in the urine at times, in pathological con- 
ditions, e. g., sugar, albumen, biliary salts, etc. 
The Gases of the urine are carbonic acid and nitrogen. 
The Liver is a highly vascular, conglomerate gland, appended to the 
alimentary canal, and performs the triple office of (i) excreting bile, (2) 
elaborating blood and (3) secreting glycogen. 
It is the largest gland in the body, weighing about pounds; it is 
situated in the right hypochondriac region, and retained in position by five 
ligaments, four of which are formed by duplicatures of the peritoneal in- 
vestment. 
The proper coat of the liver is a thin but firm fibrous membrane, closely 
adherent to the surface of the organ, which it penetrates at the transverse 
fissure, and follows the vessels in their ramifications through its substance, 
constituting Glisson's capsule. 
Structure of the Liver. The liver is made up of a large number of 
small bodies, the lobules, rounded or ovoid in shape, measuring the of 
an inch in diameter, separated by a space in which are 'situated blood 
vessels, nerves, hepatic ducts and lymphatics. 
The lobules are composed of cells, which, when examined microscopi- 
cally, exhibit a rounded or polygonal shape, and measure, on the average, 
LIVER. 64 
HUMAN PHYSIOLOGY. 
the xthtT7 °f an inch in diameter; they possess one, and at times two, nuclei; 
they also contain globules of fat, pigment matter, and animal starch. The 
cells constitute the secreting structure of the liver, and are the true hepatic 
cells. 
The Blood vessels which enter the liver are (i) The portal vein, 
made up of the gastric, splenic, superior and inferior mesenteric veins ; (2) 
the hepatic artery, a branch of the cceliac axis ; both of which are invested 
by a sheath of areolar tissue; the vessels which leave the liver are the 
hepatic veins, originating in its interior, collecting the blood distributed by 
the portal vein and hepatic artery, and conducting it to the ascending vena 
cava. 
Distribution of Vessels. The portal vein and hepatic artery, upon 
entering the liver, penetrate its substance, divide into smaller and smaller 
branches, occupy the spaces between the lobules, completely surrounding 
and limiting them, and constitute the inter-lobular vessels. The hepatic 
artery, in its course, gives off branches to the walls of the portal vein and 
Glisson’s capsule, and finally empties into the small branches of the portal 
vein in the interlobular spaces. 
The interlobular vessels form a rich plexus around the lobules, from 
which branches pass to neighboring lobules and enter their substance, 
where they form a very fine network of capillary vessels, ramifying over 
the hepatic cells, and among which the various functions of the liver are 
performed. The blood is then collected by small veins, converging toward 
the centre of the lobule, to form the intra-lobular vein, which runs through 
its long axis and empties into the sub-lobular vein. The hepatic veins are 
formed by the union of the sub-lobular veins, and carry the blood to the 
ascending vena cava; their walls are thin and adherent to the substance of 
the hepatic tissue. 
The Hepatic Ducts or Bile Capillaries originate within the lobules, 
in a very fine plexus lying between the hepatic cells; whether the smallest 
vessels have distinct membranous walls, or whether they originate in the 
spaces between the cells by open orifices, has not been satisfactorily 
determined. 
The Bile Channels empty into the interlobular ducts, which measure 
about the of an inch in diameter, and are composed of a thin homo- 
geneous membrane lined by flattened epithelial cells. 
As the interlobular bile ducts unite to form larger trunks, they receive 
an external coat of fibrous tissue, which strengthens their walls; they 
finally unite to form one large duct, the hepatic duct, which joins the cystic LIVER. 
65 
duct; the union of the two forms the ductus communis choledochus, which 
is about three inches in length, the size of a goose quill, and opens into 
the duodenum. 
The Gall Bladder is a pear-shaped sack, about four inches in length, 
situated in a fossa on the under surface of the liver. It is a reservoir for 
the bile, and is capable of holding about one ounce and a half of fluid. It 
is composed of three coats, (i) serous, a reflection of the peritoneum, (2) 
fibrous and muscular, (3) mucous. 
(1) Bile. Mechanism of its Secretion. Bile does not preexist in 
the blood,but is formed in the interior of the hepatic cells, from materials 
derived from the venous as well as arterial blood. The secreted bile is 
tljen taken up by the delicate plexus of vessels, from which it passes into 
the larger ducts, and finally either empties into the intestine or is regur- 
gitated backward into the gall bladder, in which it is stored up during the 
intervals of digestion. 
Although the secretion of bile is constantly taking place, it is only when 
the food passes into the intestinal canal that this fluid is discharged abund- 
antly, under the influence of the contraction of the walls of the gall 
bladder; it increases in amount during the period of active digestion, from 
the 2d to the 8th hour, and then gradually diminishes. 
The Bile is both a secretion and an excretion; it contains new con- 
stituents which are formed only in the substance of the liver, and are 
destined to play an important part ultimately in nutrition ; it contains also 
waste ingredients which are discharged into the intestinal canal and 
eliminated from the body. 
The physical properties and functions of bile have been considered 
under the head of digestion (see page 27). 
(2) Elaboration of Blood. Besides the capability of secreting bile, the 
liver possesses the property of so acting upon and modifying the chemical 
composition of the products of digestion, as they traverse its substance, 
that they readily assimilate with the blood, and are transformed into mate- 
rials capable of being converted into the elements of the blood and solid 
tissues. 
The albuminose particularly requires the modifying influence of the 
liver; for if it be removed from the portal vein and introduced into the 
jugular vein, it is at once removed from the blood by the action of the 
kidneys. 
The blood of the hepatic vein differs from the blood of the portal vein, 
in being richer in blood corpuscles, both red and white; its plasma is 66 
HUMAN fHYSIOLOGY. 
more dense, containing a less percentage of water and a greater amount 
of solid constituents, but no fibrin; its serum contains less albumen, fat 
and salts, but its sugar is increased. 
(3) Glycogenic Function. In addition to the two preceding func- 
tions, Bernard, in 1848, demonstrated the fact that the liver, during life, 
normally produces a sugar-forming substance, analogous in its chemical 
composition to starch, which he termed glycogen ; also that when the 
liver is removed from the body, and its blood vessels thoroughly washed 
out, after a few hours, sugar again makes its appearance, in abundance. 
It can be shown to exist in the blood of the hepatic vein as well as in 
a decoction of the liver substance, by means of either Trommer’s or 
Fehling’s tests, even when the blood of the portal vein does not contain a 
trace of sugar. 
Origin and Destination of Glycogen. Glycogen appears to be 
formed de novo in the liver cells, from materials derived from the food, 
whether the diet be animal or vegetable, though a larger per cent, is 
formed when the animal is fed on starchy and saccharine, than when fed 
on animal food. The glucose, which is one of the products of digestion, 
is absorbed by the blood vessels and carried directly into the liver; as it 
does not appear in the urine, as it would if injected at once into the 
general circulation, it is probable that it is detained in the liver, dehydrated 
and stored up as glycogen. The change is shown by the following formula: 
Glucose. 
Water. 
Glycogen. 
The glycogen thus formed is stored up in the hepatic cells for the 
future requirements of the system. When it is carried from the liver it is 
again transformed into glucose by the agency of a ferment. Glycogen 
does not undergo oxidation in the blood; this takes place in the tissues, 
particularly in the muscles, where it generates heat and contributes to the 
development of muscular force. 
Glycogen, when obtained from the liver, is an amorphous, starch-like 
substance, of a white color, tasteless and odorless, and soluble in water; 
by boiling with dilute acids, or subjected to the action of an animal 
ferment, it is easily converted into glucose. When an excess of sugar is 
generated by the liver, it can be found, not only in the blood of the hepatic 
vein, but also in other portions of the body; under these circumstances 
it is eliminated by the kidneys, appearing in the urine, constituting the 
condition of glycosuria. 
The nervous system influences the production of the glycogenic 
C6Hi206 h2o — C6H10O5. SKIN. 
67 
matter; irritation of the medulla oblongata, between the auditory and 
pneumogastric nerves, is followed by an increase in the production of 
sugar, and its appearance in the urine, which, however, is only temporary. 
SKIN. 
The Skin, the external investment of the body, is a most complex and 
important structure, serving (i) as a protective covering; (2) an organ for 
tactile sensibility; (3) an organ for the elimination of excrementitious 
matters. 
The Amount of Skin investing the body of a man of average size is 
about twenty feet, and varies in thickness, in different situations, from the 
to the of an inch. 
The skin consists of two principal layers, viz., a deeper portion, the 
Comum, and a superficial portion, the Epidermis. 
The Corium, or Cutis Vera, may be subdivided into a reticulated and 
a papillary layer. The former is composed of white fibrous tissue, non- 
striated muscular fibres and elastic tissue, interwoven in every direction, 
forming an areolar network, in the meshes of which are deposited masses 
of fat, and a structureless amorphous matter; the latter is formed mainly of 
club-shaped elevations or projections of the amorphous matter, constituting 
the papillce ; they are most abundant, and well developed, upon the palms 
of the hands and the soles of the feet; they average the of an inch in 
length, and may be simple or compound; they are well supplied with 
nerves, blood vessels and lymphatics. 
The Epidermis or scarf skin is an extra vascular structure, a 
product of the true skin, and composed of several layers of cells. It may 
be divided into two layers, the rete mucosum or the Malpighian layer, and 
the horny or corneous. 
The former closely applies itself to the papillary layer of the true skin, 
and is composed of large, nucleated cells, the lowest layer of which, the 
“ prickle cells,” contain pigment granules, which give to the skin its vary- 
ing tints in different individuals and in different races of men; the more 
superficial cells are large, colorless, and semi-transparent. The latter, 
the corneous layer, is composed of flattened cells, which, from their 
exposure to the atmosphere, are hard and horny in texture; it varies in 
thickness from of an inch on the palms of the hands and feet, to the 
of an inch in the external auditory canal. 68 
HUMAN PHYSIOLOGY. 
APPENDAGES OF THE SKIN. 
Hairs are found in almost all portions of the body, and can be divided 
into (i) long, soft hairs, on the head; (2) short, stiff hairs, along the edges 
of the eyelids and nostrils; (3) soft, downy hairs, on the general cutane- 
ous surface. They consist of a root and a shaft, which is oval in shape, 
and about the of an inch in diameter; it consists of fibrous tissue, 
covered externally by a layer of imbricated cells, and internally by cells 
containing granular and pigment material. 
The Root of the hair is embedded in the hair follicle, formed by a tubular 
depression of the skin, extending nearly through to the subcutaneous tissue ; 
its walls are formed by the layers of the corium, covered by epidermic 
cells. At the bottom of the follicle is a papillary projection of amorphous 
matter, corresponding to a papilla of the true skin, containing blood vessels 
and nerves, upon which the hair root rests. The investments of the hair 
roots are formed of epithelial cells, constituting the internal and external 
root sheaths. 
The hair protects the head from the heat of the sun and cold, retains 
the heat of the body, prevents the entrance of foreign matter into the lungs, 
nose, ears, etc. The color is due to the pigment matter, which, in old age, 
becomes more or less whitened. 
The Sebaceous Glands, imbedded in the true skin, are simple and 
compound racemose glands, opening, by a common excretory duct, upon 
the surface of the epidermis or into the hair follicle. They are found in 
all portions of the body, most abundantly in the face, and are formed by a 
delicate, structureless membrane, lined by flattened polyhedral cells. The 
sebaceous glands secrete a peculiar oily matter, the sebum, by which the 
skin is lubricated and the hairs softened; it is quite abundant in the region 
of the nose and forehead, which often present a greasy, glistening appear- 
ance ; it consists of water, mineral salts, fatty globules, and epithelial cells. 
The Vernix caseosa which frequently covers the surface of the foetus at 
birth consists of the residue of the sebaceous matters, containing epithelial 
cells and fatty matters; it seems to keep the skin soft and supple, and 
guards it from the effects of the long continued action of water. 
The Sudoriparous Glands excrete the sweat; they consist of a mass 
or coil of a tubular gland duct, situated in the derma and in the sub- 
cutaneous tissue; average the -fa of an inch in diameter, and are surrounded 
by a rich plexus of capillary blood vessels. From this coil the duct passes 
in a straight direction up through the skin to the epidermis, where it makes SKIN. 
69 
a few spiral turns and opens obliquely upon the surface. The sweat 
glands consist of a delicate homogeneous membrane lined by epithelial 
cells, whose function is to extract from the blood the elements existing in 
the perspiration. 
The glands are very abundant all over the cutaneous surface, as many 
as 3528 to the square inch, according to Erasmus Wilson. 
The Perspiration is an excrementitious fluid, clear, colorless, almost 
odorless, slightly acid in reaction, with a specific gravity of 1.003 or 1.004. 
The total quantity of perspiration excreted daily has been estimated 
at about two pounds, though the amount varies with the nature of the food 
and drink, exercise, external temperature, season, etc. 
The elimination of the sweat is not intermittent, but continuous; but 
it takes place so gradually that as fast as it is formed it passes off by 
evaporation as insensible perspiration. Under exposure to great heat and 
exercise the evaporation is not sufficiently rapid, and it appears as sensible 
perspiration. 
COMPOSITION OF SWEAT. 
Water 995-573 
Urea 0.043 
Fatty matters 0.014 
Alkaline lactates. 0.317 
Alkaline sudorates 1.562 
Inorganic salts 2.491 
1000.000 
Urea is a constant ingredient. 
Carbonic acid is also exhaled from the skin, the amount being about 
of that from the lungs. 
Perspiration regulates the temperature, and removes waste matters from 
the blood; it is so important, that if elimination be prevented death occurs 
in a short time. 
The Nervous System influences the secretion of watery vapor by causing 
a dilatation of the capillary blood vessels around the tubular coil. It is 
increased by mental emotions; section of the sympathetic fibres in the 
neck is followed by a copious perspiration; stimulation of the nerves, pro- 
ducing contraction of the vessels, is followed by an arrestation of the 
elimination of the sweat. 70 
HUMAN PHYSIOLOGY. 
NERVOUS SYSTEM. 
The Nervous System co-ordinates all the various organs and tissues 
of the body, and brings the individual into conscious relationship with 
external nature by means of sensation, motion, language, mental and moral 
manifestations. 
The Nervous Tissue may be divided into two systems, viz: the 
Cerebro-Spinal and the Sympathetic. 
(1) The Cerebro-Spinal System occupies the cavities of the cranium 
and spinal canal, and consists of the brain, the spinal cord, the cranial and 
spinal nerves. It is the system of animal life, and presides over the func- 
tions of sensation, motion, etc. 
(2) The Sympathetic System, situated along each side of the spinal 
column, consists (1) of a double chain of ganglia, united together by nerve 
cords, which extends from the base of the cranium to the coccyx; (2) of 
various ganglia, situated in the head and face, thorax, abdomen, pelvis, 
etc. All the ganglia are united together by numerous communicating 
fibres, many of which anastomose with the fibres of the cerebro-spinal 
system. It is the nervous system of organic life, and governs the functions 
of nutrition, growth, etc. 
Nervous Tissue is composed of two kinds of matter, the grey and 
white, which differ in their color, structure and physiological endowments; 
the former consists of vesicles or cells which receive and generate nerve 
force; the latter consists offibres which simply conduct it, either from the 
periphery to the centre or the reverse. 
Structure of Grey Matter. The grey matter, found on the surface of 
the brain in the convolutions, in the interior of the spinal cord, and in the 
various ganglia of the cerebro-spinal and sympathetic nervous systems, 
consists of a fine connective tissue stroma, the neuroglia, in the meshes of 
which are embedded the grey cells or vesicles. 
The cells are greyish in color, and consist of a delicate investing cap- 
sule containing a soft, granular, albuminous matter, a nucleus, and some- 
times a nucleolus. Some of the cells are spherical or oval in shape, while 
others have an interrupted outline, on account of having one, two, or more 
processes issuing from them, constituting the uni polar, bi-polar or multi- 
polar nerve cells. Cells vary in size; the smallest being found in the NERVOUS SYSTEM. 
71 
brain, the largest in the anterior horns of grey matter of the spinal cord. 
Some of the cell processes become continuous with the fibres of the white 
matter, while others anastomose with those of adjoining cells and form a 
plexus. 
Structure of the White Matter. The white matter, found for the 
most part in the interior of the brain, on the surface of the spinal cord, and 
in almost all of the nerves of the cerebro-spinal and sympathetic systems, 
consists of minute tubules or fibres, the ultimate nerve filaments, which, in 
the perfectly fresh condition, are apparently structureless and homogeneous; 
but when carefully examined after death are seen to consist of three dis- 
tinct portions, (i) a tubular membrane; (2) the white substance of 
Schwann; (3) the axis cylinder. 
The Tubular membrane, investing the nerve filament, is thin, homo- 
geneous, and lined by large, oval nuclei, and presents, in its course, annular 
constrictions; it serves to keep the internal parts of the fibre in position, 
and protects them from injury. 
The White substance of Schwann, or the medullary layer, is situated 
immediately within the tubular membrane, and gives to the nerves their 
peculiar white and glistening appearance. It is composed of oleaginous 
matter in a more or less fluid condition ; after death it undergoes coagula- 
tion, giving to the fibre a knotted or varicose appearance. It serves to 
insulate the axis cylinder, and prevents the diffusion of the nerve force. 
The Axis cylinder occupies the centre of the medullary substance. In 
the natural condition it is transparent and invisible, but when treated with 
proper reagents, it presents itself as a pale, granular, flattened band, 
albuminous in character, more or less solid, and somewhat elastic. It is 
composed of a number of minute fibrillge united together to form a single 
bundle. (Schultze.) 
Nerve fibres in which these three structural elements coexist are known 
as the medullated nerve fibres. In the sympathetic system, and in the 
gray substance of the cerebro-spinal system, many nerves are destitute of a 
medullary layer, and are known as the non-medullated nerve fibres. 
Grey or Gelatinous nerve fibres, found principally in the sympathetic 
system, are grey in color, semi-transparent, flattened, with distinct borders, 
finely granular, and present oval nuclei. 
The diameter of the gelatinous fibres is about the an 5 °f 
the medullated fibres, from to of an inch. 
Ganglia are small bodies, varying considerably in size, situated on the 
posterior roots of spinal nerves, on the sensory cranial nerves, alongside 72 
HUMAN PHYSIOLOGY. 
of the vertebral column, forming a connected chain, and in the different 
viscera They consist of a dense, investing, fibrous membrane, containing 
in its interior grey or vesicular cells, among which are found white and 
gelatinous nerve fibres. They may be regarded as independent nerve 
centres. 
Structure of Nerves. Nerves are rounded or flattened cords extend- 
ing from the centres to the periphery; they are surrounded externally by a 
sheath, the neurilemma, composed of fibrous and elastic tissue forming a 
stroma, in which blood vessels ramify, from which the nerves derive their 
nourishment. 
A Nerve consists of a greater or less number of ultimate nerve filaments, 
separated into bundles by fibrous septa given off from the neurilemma. 
The nerve filaments pursue an uninterrupted course, from their origin to 
their termination; branches pass from one nerve trunk into the sheath of 
another, but there is no anastomosis or coalescence with adjoining nerve 
fibres. 
A Plexus is formed by a number of branches of different nerves inter- 
lacing in every direction, in the most intricate manner, but from which 
fibres are again given off to pursue their independent course, e.g., brachial, 
cervical, lumbar, sacral, cardiac plexuses, etc. 
SPINAL NERVES. 
Origin. The spinal nerves are thirty-one in number on each side 
of the spinal cord, and arise by two roots, an anterior and posterior, 
from the anterior and posterior aspects of the cord respectively; the pos- 
terior roots present near their emergence from the cord a small ganglionic 
enlargement; outside of the spinal canal the two roots unite to form a 
main trunk, which is ultimately distributed to the skin, muscles and viscera. 
The Function of the Anterior Roots is to transmit motor impulses 
from the centres outward to the periphery. Irritation of these roots, from 
whatever cause, excites convulsive movements in the muscles to which 
they are distributed; disease or division of these roots induces a condition 
of paresis or paralysis. 
The Function of the Posterior Roots is to transmit the impressions 
made upon the periphery to the centres in the spinal cord, where they 
excite motor impulses, or to the brain, in which they are translated into 
conscious sensations. Irritation of these roots gives rise to painful sensa- 
tions ; division of the roots abolishes all sensation in the parts to which 
they are distributed. SPINAL NERVES. 
73 
The ganglion on the posterior root influences the nutrition of the sen- 
sory nerve; for if the nerve be separated from the ganglion, it undergoes 
degeneration in the course of a few days, in the direction in which it 
carries impressions, i. e., from the periphery to the centres; if the nerve be 
divided between the ganglion and the cord, the central end only undergoes 
degeneration. The nutrition of the anterior root is governed by nerve cells 
in the grey matter of the cord; for if these cells undergo atrophy, or if 
the nerve be divided, it undergoes degeneration outward. 
Nerve Terminations, (i) Central. Both motor and sensory nerve 
fibres, as they enter the spinal cord and brain, lose their external invest- 
ments, and retaining only the axis cylinder, ultimately become connected 
with the processes of the grey cells. 
(2) Peripheral. As the nerves approach the tissues to which they are 
to be distributed, they inosculate freely, forming a plexus from which the 
ultimate fibres proceed to individual tissues. 
Motor Nerves. In the voluntary or striped muscles the motor nerves 
are connected with the contractile substance by means of the “ motorial 
end plates /” when the nerve enters the muscular fibre the tubular mem- 
brane blends with the sarcolemma, the medullary layer disappears, and 
the axis cylinder spreads out into the form of a little plate, granular in 
character, and containing oval nuclei. 
In the unstriped or involuntary muscles, the terminal nerve fibres form 
a plexus on the muscular fibre cells, and become connected with the 
granular contents of the nuclei. 
In the glands nerve fibres have been traced to the glandular cells, where 
they form a branching plexus from which fibres pass into their interior 
and become connected with their substance, and thus influence secretion. 
Sensitive Nerves terminate in the skin and mucous membranes, in 
three distinct modes, e. g., as tactile corpuscles, Pacinian corpuscles, and 
as end bulbs. 
The tactile corpuscles are found in the papilla; of the true skin, espe- 
cially on the palmar surface of the hands and fingers, feet and toes ; they 
are oblong bodies, measuring about of an inch in length, consisting of 
a central bulb of homogeneous connective tissue surrounded by elastic fibres 
and elongated nuclei. The nerve fibre approaches the base of the cor- 
puscle, makes two or three spiral turns around it, and terminates in loops. 
They are connected with the sense of touch. 
The Pacinian corpuscles are found chiefly in the subcutaneous cellular 
tissue, on the nerves of the hands and feet, the intercostal nerves, the 74 
HUMAN PHYSIOLOGY. 
cutaneous nerves, and in many other situations. They are oval in shape, 
measure about the of an inch in length on the average, and consist of 
concentric layers of connective tissue; the nerve fibre penetrates the cor- 
puscle and terminates in a rounded knob in the central bulb. Their 
function is unknown. 
The end bulbs of Krause are formed of a capsule of connective tissue in 
which the nerve fibre terminates in a coiled mass or bulbous extremity; 
they exist in the conjunctiva, tongue, glans penis, clitoris, etc. 
Many sensitive nerves terminate in the papillae at the base of the hair 
follicle ; but in the skin, mucous membranes, and organs of special sense 
their mode of termination is not well understood. 
PROPERTIES AND FUNCTIONS OF NERVES. 
Classification. Nerves may be divided into two groups, viz:— 
(1) Afferent or centripetal, as when they convey to the nerve centres 
the impressions which are made upon their peripheral extremities or parts 
of their course. They may be sensitive, when they transmit impressions 
which give rise to sensations; reflective or excitant, when the impression 
carried to the nerve centre is reflected outward by an efferent nerve and 
produces motion or some other effect in the part to which the nerve is dis- 
tributed. 
(2) Efferent or centrifugal, as when the impulses generated in the 
centres are transmitted outward to the muscles and various organs. They 
may be motor, as when they convey impulses to the voluntary and involun- 
tary muscles; vaso-motor, when they regulate the calibre of the small blood 
vessels, increasing or diminishing the amount of blood to a part; secretory, 
when they influence secretion; trophic, when they influence nutrition ; 
inhibitory, when they conduct impulses which produce a restraining or 
inhibiting action. 
The Axis Cylinder is the essential conducting agent, the white substance 
of Schwann and tubular membrane being probably accessory structures, 
protecting the axis from injury, and preventing the diffusion of nerve force 
to adjoining nerves. 
The properties of sensation and motion reside in different nerve fibres. 
Motor nerves can be destroyed or paralyzed by the introduction of woorara 
under the skin, without affecting sensation; the sensibility of nerves can be 
abolished by the employment of anaesthetics without destroying motion. 
Irritability. Nerves conduct peripheral impressions to the centres, and 
motor impulses to the periphery, in virtue of their possessing an ultimate 
and inherent property, denominated neurility, nervous irritability, or PROPERTIES AND FUNCTIONS OF NERVES. 
75 
excitability, which is manifested as long as the physical and chemical integ- 
rity of the nerve is maintained. 
Nerve degeneration. When nerves are separated from their trophic or 
nutritive centres, they degenerate progressively in the direction in which 
they conduct impressions. In motor nerves, from the centre to the pe- 
riphery ; in sensory nerves, from the periphery to the centres. 
Nerve force is not identical with electricity. Nerves do not possess the 
power of generating force, or of originating impulses within themselves, 
but propagate only the nervous impulses which are called forth by chemi- 
cal, physical and mechanical stimuli from without, and by volitional acts, 
normal and pathological conditions from within. * 
Phenomena of Muscles and Nerves. The muscles are the motor 
organs of the body and constitute a large per cent, of the body weight. 
Muscles are of two kinds, striated and non-striated or involuntary. The 
striated muscles consist of bundles of fibres, the fasciculi, held together 
by connective tissue. Each muscle fibre is about yz to I inches long, 
and possesses a delicate homogeneous membrane, the sarcolemma, in the 
interior of which is contained the contractile substance, which presents a 
striated appearance. During life this substance is in a fluid condition, but 
after death undergoes stiffening. 
The non-striated muscles form membranes which surround cavities, e.g., 
stomach, arteries, bladder, etc. They are composed of elongated cells 
without striations and contain in their interior one or more nuclei. 
Muscular tissue is composed of water, an organic contractile substance, 
myosin, non-nitrogenized substances, such as glycogen, inosite, fat and 
inorganic salts. When at rest the muscle is alkaline in reaction, but 
during and after contraction it becomes acid. 
Muscles possess the properties of (i) Contractility, which is the capa- 
bility of shortening themselves in the direction of their long axis, and at 
the same time becoming thicker and more rigid. (2) Extensibility, by 
means of which they are lengthened in proportion to weights attached. 
(3) Elasticity, in virtue of which they return to their original shape when 
the force applied is removed. 
The contractility of muscles is called forth mainly by nervous impulses, 
descending motor nerves, which originate in the central nervous system; 
but it can also be excited by the electric current, the application of strong 
acids, heat, or by mechanical means. 
Phenomena of a Muscular Contraction. When a single induc- 
tion shock is propagated through a nerve, the muscle to which it is dis- 76 
HUMAN PHYSIOLOGY. 
tributed undergoes a quick pulsation, and speedily returns to its former 
condition. As is shown by the muscle curve, the contraction, which is at 
first slow, increases in rapidity to its maximum, gradually relaxes and is 
again at rest, the entire pulsation not occupying more than the of a 
second. 
The muscular contraction does, not instantly follow the induction shock 
even when the electrodes are placed directly upon the muscular fibres 
themselves; an appreciable period intervenes before the contraction, 
during which certain chemical changes are taking place preparatory to the 
manifestation of force. This is the “latent period,” which has an average 
duration of the of a second, but varies with the temperature, the strength 
of the stimulus, the animal, etc. The muscular movements of the body, 
however, are occasioned by contractions of a much longer duration, 
depending upon the number (the average, 20) of nervous impulses passing 
to the muscles in a second. 
During the muscular contraction the following phenomena are observed, 
viz: a change in form, a rise in temperature, a consumption of oxygen and 
an evolution of carbonic acid; the production of a distinct musical sound, 
a change from an alkaline to an acid reaction, from the development of 
sarcolactic acid; a disappearance of the natural muscle currents, which 
undergo a negative variation in the “ latent period,” just after the nervous 
impulse reaches the termination of the nerve, and before the appearance of 
the muscular contraction wave. 
Electrical Properties of Nerves. When a galvanic current is made 
to flow along a motor nerve from the centre to the periphery, from 
the positive to the negative pole, it is known as the direct, descending or 
centrifugal current. When it is made to flow in the reverse direction it is 
known as the inverse, ascending or centripetal current. 
The passage of a direct current enfeebles the excitability of a nerve; the 
passage of the inverse current increases it. The excitability of a nerve 
may be exhausted by the repeated applications of electricity; when thus 
exhausted it may be restored by repose, or by the passage of the inverse 
current if the nerve has been exhausted by the direct current or vice 
versa. 
During the actual passage of a feeble constant current in either direction 
neither pain nor muscular contraction is ordinarily manifested; if the 
current be very intense the nerve may be disorganized and its excitability 
destroyed. CRANIAL NERVES. 
77 
Electrotonus. The passage of a direct galvanic current through a 
portion of a nerve, excites in the parts beyond the electrodes a condition 
of electric tension or electrotonus, during which the excitability of the 
nerve is decreased near the anode or positive pole, and increased near the 
kathode or negative pole; the increase of excitability in the kathelectro- 
tonic area, that nearest the muscle, being manifested by a more marked 
contraction of the muscle than the normal, when the nerve is irritated in 
this region. The passage of an inverse galvanic current excites the same 
condition of electrotonus; and the diminution of excitability near the 
anode, the anelectrotonic area, that now nearest the muscle, being mani- 
fested by a less marked contraction than the normal when the nerve is 
stimulated in this region. Between the electrodes is a neutral point where 
the kathelectrotonic area emerges into the anelectrotonic area. If the 
current be a strong one the neutral point approaches the kathode; if weak, 
it approaches the anode. 
When a nervous impulse passes along a nerve the only appreciable 
effect is a change in its electrical condition, there being no change in its 
temperature, chemical composition or physical condition. The natural 
nerve currents, which are always present in a living nerve as a result 
of "its nutritive activity, in great part disappear during the passage of an 
impulse, undergoing a negative variation. 
The rapidity with which nervous impulses are propagated along a nerve 
has been estimated at about ioo feet in a second for both motor and 
sensory nerves, but varies according to the temperature, the degree of 
excitability, the strength of the stimulus, etc. 
Law of Contraction. If a feeble galvanic current be applied to a 
recent and excitable nerve, contraction is produced in the muscles 
only upon the making of the circuit with both the direct and inverse 
current. 
If the current be moderate in intensity the contraction is produced in the 
muscle both upon the making and breaking of the circuit, with both the 
direct and inverse currents. 
If the current be intense, contraction is produced only when the circuit 
is made with the direct current, and only when it is broken with the 
inverse current. 
CRANIAL NERVES. 
The Cranial Nerves come off from the base of the brain, pass through 
the foramina in the walls of the cranium, and are distributed to the skin, 
muscles and organs of sense in the face and head. 78 
HUMAN PHYSIOLOGY. 
According to the classification of Soemmering, there are 12 pairs of 
nerves, enumerating them from before backward, as follows, viz :— 
xst Pair, or Olfactory. 7th Pair, or Facial, Portio dura. 
2d Pair, or Optic. 8th Pair, or Auditory, Portio mollis. 
3d Pair, or Motor oculi communis. 9th Pair, or Glosso-pharyngeal. 
4th Pair, or Patheticus, Trochlearis. 10th Pair, or Pneumogastric. 
5th Pair, or Trifacial, Trigeminus, nth Pair, or Spinal accessory. 
6th Pair, or Abducens. 12th Pair, or Hypoglossal. 
The Cranial Nerves may also be classified physiologically, according 
to their function, into three groups: 1. Nerves of special sense. 2. 
Nerves of motion. 3. Nerves of general sensibility. 
1st Pair. Olfactory. 
Apparent Origin. From the inferior and internal portion of the anterior 
lobes of the cerebrum by three roots, viz : an external white root, which 
passes across the fissure of Sylvius to the middle lobe of the cerebrum; an 
internal white root, from the most posterior part of the anterior lobe; a 
grey root, from the grey matter in the posterior and inner portion of the 
inferior surface of the anterior lobe. 
Deep Origin. Not satisfactorily determined. 
Distribution. The olfactory nerve, formed by the union of the three 
roots, passes forward along the under surface of the anterior lobe to the 
ethmoid bone, where it expands into the olfactory bulb. This bulb con- 
tains ganglionic cells, is greyish in color and soft in consistence; it gives 
off from its under surface from 15 to 20 nerve filaments, the true olfactory 
nerves, which pass through the cribriform plate of the ethmoid bone, and 
are distributed to the Schneiderian mucous membrane. This membrane 
extends from the cribriform plate of the ethmoid bone downward, about 
one inch. 
Properties. The olfactory nerves give rise to neither motor nor sensory 
phenomena when stimulated. They carry simply the special impressions of 
odorous substances. Destruction or injury of the olfactory bulbs is attended 
by a loss of the sense of smell. 
Function. Governs the sense of smell. Conducts the impressions 
which give rise to odorous sensations. 
2d Pair. Optic. 
Apparent Origin. From the anterior portion of the optic commissure. 
Deep Origin. An external -white root, from the corpus geniculatum 
externum; an internal white root, from the corpus geniculatum internum CRANIAL NERVES. 
79 
and the anterior tubercula quadrigemina; a grey root, from the grey matter 
in the floor of the 3d ventricle. Filaments also come from the optic thalami 
and cerebral peduncles. 
Distribution. The two roots unite to form a flattened band, the optic 
tract, which winds around the crus cerebri to decussate with the nerve of 
the opposite side, forming the optic chiasm. The decussation of fibres is 
not complete ; some of the fibres of the left optic tract going to the outer 
half of the eye of the same side, and to the inner half of the eye of the 
opposite side; the same holds true for the right optic tract. 
The optic nerves proper arise from the commissure, pass forward through 
the optic foramina, and are finally distributed in the retina. 
Properties. They are insensible to ordinary impressions, and convey 
only the special impressions of light. 
Division of one of the nerves is attended by complete blindness in the 
eye of the corresponding side ; division of the optic tract produces loss of 
sight in the outer half of the eye of the same side, and in the inner half of 
the eye of the opposite side. Lesion of the anterior part of the optic 
chiasm causes blindness in the inner half of the two eyes. 
Functions. Governs the sense of sight. Receives and conveys to the 
brain the luminous impressions which give rise to the sensation of sight. 
The reflex movements of the iris are called forth by the optic nerve. 
When an excess of light falls upon the retina the impression is carried 
back to the tubercula quadrigemina, where it is transformed into a motor 
impulse, which then passes outward through the motor oculi nerve to the 
contractile fibres of the iris and diminishes the size of the pupil. The 
absence of light is followed by a dilatation of the pupil. 
Apparent Origin. From the inner surface of the crura cerebri. 
Deep Origin. By filaments coming from the lenticular nucleus, corpora 
quadrigemina, optic thalamus; these filaments converge to form a main 
trunk, which winds around the crus cerebri, in front of the pons Varolii. 
Distribution. The nerve then passes forward, and enters the orbit 
through the sphenoidal fissure, where it divides into a superior branch, 
distributed to the superior rectus and levatorpalpebrce muscles; an inferior 
branch sending branches to the internal and inferior recti, and the inferior 
oblique muscles; filaments also pass into the ciliary or ophthalmic ganglion ; 
from this ganglion the ciliary nerves arise which enter the eyeball, and 
are distributed to the circular fibres of the iris and the ciliary muscle. The 
3d Pair. Motor Oculi Communis. 80 
HUMAN PHYSIOLOGY. 
3d nerve also receives filaments from the cavernous plexus of the sympa- 
thetic and from the 5th nerve. 
Properties. Irritation of the root of the nerve produces contraction 
of the pupil, internal strabismus, muscular movements of eye, but no pain. 
Division of the nerve is followed by ptosis (falling of the upper eyelid), 
external strabismus, due to the unopposed action of the external rectus 
muscle; dilatation of the pupil and persistent accommodation of the eye 
for long distances, from paralysis of the circular fibres of the iris and ciliary 
muscle; and inability to rotate the eye, slight protrusion and double 
vision, the images being on the same plane. 
Function. Governs movements of the eyeball by animating all the 
muscles except the external rectus and superior oblique, the movements of 
the iris, elevates the upper lid, influences the accommodation of the eye 
for distances. Can be called into action by (1) voluntary stimuli, (2) by 
reflex action through irritation of the optic nerve. 
4th Pair. Patheticus. 
Apparent Origin. From the superior peduncles of the cerebellum. 
Deep Origin. By fibres terminating in the corpora quadrigemina, 
lenticular nucleus, valve of Vieussens, and in the substance of the cerebellar 
peduncles; some filaments pass over the median line and decussate with 
fibres of the opposite side. 
Distribution. The nerve enters the orbital cavity through the sphe- 
noidal fissure, and is distributed to the sziperior oblique muscle; in its 
course receives filaments from the ophthalmic branch of the 5th pair and 
the sympathetic. 
Properties. When the nerve is irritated muscular movements are pro- 
duced in the superior oblique muscle, and the pupil of the eye is turned 
downward and outward. Division or paralysis of the nerve renders the 
eyeball immovable as far as rotation is concerned, and produces double 
vision. 
Function. Governs the movements of the eyeball produced by the 
action of the superior oblique muscles. 
6th Pair.* Abducens. Motor Oculi Externus. 
Apparent Origin. From the groove between the anterior pyramidal 
body and the pons Varolii, where it arises by two roots. 
Deep Origin. From the grey matter of the medulla oblongata. 
* The 6th nerve is considered in connection with the 3d and 4th nerves, since they 
together constitute the motor apparatus by which the ocular muscles are excited to action. CRANIAL NERVES. 
81 
Distribution. The nerve then passes into the orbit through the sphe- 
noidal fissure, and is distributed to the external rectus muscle. Receives 
filaments from the cervical portion of the sympathetic, through the carotid 
plexus and spheno-palatine ganglion. 
Properties. When irritated, the external rectus muscle is thrown into 
convulsive movements, and the eyeball is turned outward. When divided 
or paralyzed, this muscle is paralyzed, and internal strabismus is produced. 
Function. To turn the eyeball outward. 
Apparent Origin. By two roots from the side of the pons Varolii. 
Deep Origin. The deep origin of the two roots is the upper part of 
the floor and anterior wall of the 4th ventricle, by three bundles of fila- 
ments, one of which anastomoses with the auditory nerve; another passes 
to the lateral tract of the medulla; while a third, greyish in color, goes to 
the restiform bodies, and may be traced to the point of the calamus 
scriptorius. 
Filaments of origin have been traced to the “trigeminal sensory nucleus,” 
located on a level with the point of exit of the nerve, and to the posterior 
grey horns of the cord, as low down as the middle of the neck. 
Distribution. The large root of the nerve passes obliquely upward 
and forward to the ganglion of Gasser, which receives filaments of com- 
munication from the carotid plexus of the sympathetic. It then divides 
into three branches. 
1. Ophthalmic branch, which receives communicating filaments from 
the sympathetic, and sends sensitive fibres to all the motor nerves of the 
eyeball. It is distributed to the ciliary ganglion, lachrymal gland, sac and 
caruncle, conjunctiva, integument of the upper eyelid, forehead, side of 
head and nose, anterior portion of the scalp, ciliary muscle and iris. 
2. Superior maxillary branch, sends branches to the spheno-palatine 
ganglion, integument of the temple and lower eyelid, side of forehead, 
nose, cheek and upper lip, teeth of the upper jaw, and alveolar processes. 
3. Inferior maxillary branch, which, after receiving in its course fila- 
ments from the small root and from the facial, is distributed to the sub- 
maxillary ganglion, the parotid and subdingual glands, external auditory 
meatus, mucous membrane of the mouth, anterior two-thirds of the tongue 
(lingual branch), gums, arches of the palate, teeth of the lower jaw, and 
integument of the lower part of the face, and to the muscles of mastication. 
The small root passes forward beneath the ganglion of Gasser, through 
the foramen ovale, and joins the inferior maxillary division of the large 
5th Pair. Trifacial. Trigeminal. 82 
HUMAN PHYSIOLOGY. 
root, which then divides into an anterior and posterior branch, the former 
of which is distributed to the muscles of mastication, viz: temporal, 
masseter, internal and external pterygoid muscles. 
Properties. It is the most acutely sensitive nerve in the body, and 
endows all the parts to which it is distributed with general sensibility. 
Irritation of the large root, or any of its branches, will give rise to 
marked evidence of pain; the various forms of neuralgia of the head and 
face being occasioned by compression, disease, or exposure of some of its 
terminal branches. 
Division of the large root within the cranium is followed at once by a 
complete abolition of all sensibility in the head and face, but is not attended 
by any loss of motion. The integument, mucous membranes and the eye, 
may be lacerated, cut or bruised, without the animal exhibiting any 
evidence of pain. At the same time the lachrymal secretion is diminished, 
the pupil becomes contracted, the eyeball is protruded, and the sensibility 
of the tongue is abolished. 
The reflex movements of deglutition are also somewhat impaired; the 
impression of the food being unable to reach and excite the nerve centre 
in the medulla oblongata. 
Galvanization of the small root produces movements of the muscles of 
mastication; section of the root causes paralysis of these muscles, and the 
jaw is drawn to the opposite side, by the action of the opposing muscles. 
Influence upon the Special Senses. After division of the large 
root within the cranium, a disturbance in the nutrition of the special senses 
sooner or later manifests itself. 
Sight. In the course of 24 hours the eye becomes very vascular and 
inflamed, the cornea becomes opaque and ulcerates, the humors are dis- 
charged, and the eye is totally destroyed. 
Smell. The nasal mucous membrane swells up, becomes fungous, and 
is liable to bleed on the slightest irritation. The mucus is increased in 
amount, so as to obstruct the nasal passages; the sense of smell is finally 
abolished. 
Hearing. At times the hearing is impaired, from disorders of nutrition 
in the middle ear and external auditory meatus. 
Alteration in the nutrition of the special senses is not marked if the sec- 
tion is made posterior to the ganglion of Gasser, and to the anastomosing 
filaments of the sympathetic which join the nerve at this point; but if the 
ganglion be divided, these effects are very noticeable, due to the section 
of the sympathetic filaments. CRANIAL NERVES. 
83 
Function. Gives sensibility to all parts of the head and face to which 
it is distributed; through the small root endows the masticatory muscles 
with motion; through fibres from the sympathetic governs the nutrition of 
the special senses. 
7th Pair. Portio Dura. Facial Nerve. 
Apparent Origin. From the groove between the olivary and restiform 
bodies at the lateral portion of the medulla oblongata, and below the 
margin of the pons Varolii. 
Deep Origin. From a nucleus of large cells in the floor of the 4th 
ventricle, below the nucleus of origin of the 6th pair, with which it is 
connected. Some filaments are traceable to the lenticular nucleus of the 
opposite side. Some of the fibres cross the median line and decussate. It 
is intimately associated with the nerve of Wrisberg at its origin. 
Distribution. From its origin the facial nerve passes into the internal 
auditory meatus, and then, in company with the nerve of Wrisberg, enters 
the aqueduct of Fallopius. The filaments of the nerve of Wrisberg are 
supplied with a ganglion, of a reddish color, having nerve cells. These 
filaments unite with those of the root of the facial, to form a common 
trunk, which emerges at the stylo mastoid foramen. 
In the aqueduct the facial gives off the following branches, viz:— 
1. Large petrosal nerve, which passes forward to the spheno-palatine, or 
Meckel’s ganglion, and through this to the levator palati and azygos uvulae 
muscles, which receive motor influence from this source. 
2. Small petrosal nerve, passing to the otic ganglion and thence to the 
tensor-tympani muscle, endowing it with motion. 
3. Tympanic branch, giving motion to the stapedius muscle. 
4. Chorda tympani nerve, which after entering the posterior part of the 
tympanic cavity, passes forward between the malleus and incus bones, 
through the Glasserian fissure, and joins the lingual branch of the 5th 
nerve. It is then distributed to the mucous membrane of the anterior 
two-thirds of the tongue and the sub-maxillary glands. 
After emerging from the stylo-mastoid foramen, the facial nerve sends 
branches to the muscles of the ear, the occipito-frontalis, the digastric, the 
palato-glossi, and palato-pharyngei; after which it passes through the 
parotid gland and divides into the temporo-facial and cervico-facial 
branches, which are distributed to the superficial muscles of the face, viz: 
occipito-frontalis, corrugator supercilii, orbicularis palpebrarum, levator 
labii superioris et alseque nasi, buccinator, levator anguli oris, orbicularis 
oris, zygomatici, depressor anguli oris, platysma myoides, etc. 84 
HUMAN PHYSIOLOGY. 
Properties. Undoubtedly a motor nerve at its origin, but in its course 
receives sensitive filaments from the 5th pair and the pneumogastric. 
Irritation of the nerve, after its emergence from the stylo-mastoid fora- 
men, produces convulsive movements in all the superficial muscles of the 
face. Division of the nerve at this point causes paralysis of these muscles 
on the side of the section, constituting facial paralysis ; the phenomena of 
which are, a relaxed and immobile condition of the same side of the face; 
the eyelids remain open, from paralysis of the orbicularis palpebrarum ; 
the act of winking is abolished; the angle of the mouth droops, and saliva 
constantly drains away; the face is drawn over to the sound side; the face 
becomes distorted upon talking or laughing; mastication is interfered with, 
the food accumulating between the gums and cheek, from paralysis of the 
buccinator muscle; fluids escape from the mouth in drinking; articulation 
is impaired, the labial sounds being imperfectly pronounced. 
Properties of the branches given off in the aqueduct of Fallopius. The 
Large petrosal, when irritated, throws the levator palati and azygos uvulae 
muscles into contraction. Paralysis of this nerve, from deep-seated lesions, 
produces a deviation of the uvula to the sound side, a drooping of the 
palate, and an inability to elevate it. 
The Small petrosal influences hearing by animating the tensor tympani 
muscle; when paralyzed, there occurs partial deafness and an increased 
sensibility to sonorous impressions. 
The Tympanic branch animates the stapedius muscle, and influences 
audition. 
The Chorda tympani influences the circulation and the secretion of 
saliva, in the sub-maxillary glands, and governs the sense of taste in the 
anterior two-thirds of the tongue. Galvanization of the chorda tympani 
dilates the blood vessels, increases the quantity and rapidity of the stream 
of blood, and increases the secretion of saliva. Division of the nerve is 
followed by contraction of the vessels, an arrestation of the secretion, and 
a diminution of the sense of taste, on the same side. 
Function. The facial is the nerve of expression, and co-ordinates the 
muscles employed to delineate the various emotions, influences the sense 
of taste, deglutition, movements of the uvula and soft palate, the tension of 
the membrana tympani, and the secretions of the sub-maxillary and parotid 
glands. Indirectly influences smell, hearing and vision. 
8th Pair, Portio Mollis, Auditory Nerve. 
Apparent Origin. From the upper and lateral portion of the medulla 
oblongata, just below the margin of the pons Varolii. CRANIAL NERVES. 
85 
Deep Origin. By two roots frorn the floor of the 4th ventricle, each 
root consisting of a number of grey filaments, some of which decussate in 
the median line; the external root has a gangliform enlargement contain- 
ing fusiform nerve cells. 
Distribution. The two roots wind around the restiform bodies and 
enter the internal auditory meatus, and divide into an anterior branch 
distributed to the cochlea, and a posterior branch distributed to the vesti- 
bule and semicircular canals. 
Properties. They are soft in consistence, greyish in color, consisting 
of axis cylinders with a medullary sheath only; they are not sensible to 
ordinary impressions, but convey the impression of sound. 
Function. Governs the sense of hearing. Receives and conducts to 
the brain the impressions of sound, which give rise to the sensations of 
hearing. 
Apparent Origin. Partly from the medulla oblongata and the inferior 
peduncles of the cerebellum. 
Deep Origin. From the lower portion of the grey substance in the 
floor of the 4th ventricle. 
This nerve has two ganglia; the jugular ganglion includes only a por- 
tion of the root filaments; the ganglion of Andersch includes all the fibres 
of the trunk. 
Distribution. The trunk of the nerve passes downward and forward, 
receiving near the ganglion of Andersch fibres from the facial and pneumo- 
gastric nerves. It divides into two large branches, one of which is 
distributed to the base of the tongue, the other to the pharynx. In its 
course it sends filaments to the otic ganglion; a tympanic branch which 
gives sensibility to the mucous membrane of the fenestra rotunda, fenestra 
ovalis, and Eustachian tube; lingual branches to the base of the tongue; 
palatal branches to the soft palate, uvula and tonsils; pharyngeal branches 
to the mucous membrane of the pharynx. 
Properties. Irritation of the roots at their origin calls forth evidences 
of pain; it is, therefore, a sensory nerve, but its sensibility is not so acute 
as that of the tri-facial. Irritation of the trunk after its exit from the 
cranium produces contraction of the muscles of the palate and pharynx, 
due to the presence of anastomosing motor fibres. 
Division of the nerve abolishes sensibility in the structures to which it 
is distributed, and impairs the sense of taste in the posterior third of the 
tongue (see Sense of Taste). 
9th Pair. Glosso-pharyngeal. 86 
HUMAN PHYSIOLOGY. 
Function. Governs sensibility#of pharynx, presides partly over the 
sense of taste, and controls reflex movements of deglutition and' vomiting. 
Apparent Origin. From the lateral sideof the medulla oblongata, just 
behind the olivary body. 
Deep Origin. In the grey nuclei in the lower half of the floor of the 
4th ventricle, and in the substance of the restiform body. Some filaments 
are traced along the restiform tract, toward the cerebellum, and others to 
the median line of the floor of the 4th ventricle, where many of them 
decussate. 
This nerve has two ganglia; one in the jugular foramen, called the gan- 
glion of the root, find another outside of the cranial cavity on the trunk, 
the ganglion of the trunk. 
Distribution. The filaments from the root unite to form a single trunk, 
which leaves the cavity of the cranium* through the jugular foramen, in 
company with the spinal accessory and glosso-pharyngeal. It soon receives 
an anastomotic branch from the spinal accessory, and afterward branches 
from the facial, the hypoglossal and the anterior branches of the two upper 
cervical nerves. , 
As the nerve passes down the neck it sends off the following main 
branches:— 
1. Pharyngeal nerves, which assist in forming the pharyngeal plexus, 
which is distributed to the mucous membrane and muscles of the pharynx, 
2. Superior laryngeal nerve, which enters the larynx through the thyro- 
hyoid membrane, and is distributed to the mucous membrane lining the 
interior of the larynx, and to the crico thyroid muscle and the inferior 
constrictor of the pharynx. The “ depressor nerve” found in the rabbit, 
is formed by the union of two branches, one from the superior laryngeal, 
the other from the main trunk; it passes downward to be distributed to 
the heart. 
3. Inferior laryngeal, which sends its ultimate branches to all the in- 
trinsic muscles of the larynx except the crico-thyroid, and to the inferior 
constrictor of the pharynx. 
4. Cardiac branches, given off from the nerve throughout its course, 
which unite with the sympathetic fibres to form the cardiac plexus, to be 
distributed to the heart. 
5. Pulmonary branches, which form a plexus of nerves and are dis- 
tributed to the bronchi and their ultimate terminations, the lobules and air 
cells. 
10th Pair. Pneumogastric. Par Vagum. CRANIAL NERVES. 
87 
From the right pneumogastric nerve branches are distributed to the 
mucous membrane and muscular coats of the stomach and intestines, to 
the liver, spleen, kidneys, and supra-renal capsules. 
Properties. At its origin the pneumogastric nerve is sensory, as shown 
by direct irritation or galvanization, though its sensibility is not very 
marked In its course exhibits motor properties, from anastomosis with 
motor nerves. 
The Pharyngeal branches assist in giving sensibility to the mucous mem- 
brane of the pharynx, and influence reflex phenomena of deglutition, 
through motor fibres which they contain, derived from the spinal accessory. 
The Superior laryngeal nerve endows the upper portion of the larynx 
with sensibility ; protects it from the entrance of foreign bodies ; by con- 
ducting impressions to the medulla, excites the reflex movements of deglu- 
tition and respiration; through the motor filaments it contains produces 
contraction of the crico-thyroid muscle. 
Division of the “ Depressor nervef and galvanization of the central 
end, retards and even arrests the pulsations of the heart, and by depressing 
the vaso-motor centre diminishes the pressure of blood in the large vessels, 
by causing dilatation of the intestinal vessels through the splanchnic 
nerves. 
The Inferior laryngeal contains, for the most part, motor fibres from 
the spinal accessory. When irritated, produces movement in the laryn- 
geal muscles. When divided, is followed by paralysis of these muscles, 
except the crico-thyroid, impairment of phonation, and an embarrassment 
of the respiratory movements of the larynx, and finally death, from suffoca- 
tion. 
The Cardiac branches, through filaments derived from the spinal acces- 
sory, exert a direct inhibitory action upon the heart. Division of the 
pneumogastrics in the neck increases the frequency of the heart’s action. 
Galvanization of the peripheral ends diminishes the heart’s pulsation, and, 
if sufficiently powerful, paralyzes it in disastole. 
The Pulmonary branches give sensibility to the bronchial mucous mem- 
brane, and govern the movements of respiration. Division of both 
pneumogastrics in the neck diminishes the frequency of the respiratory 
movements, falling as low as 4 to 6 per minute; death usually occurs in 
from 5 to 8 days. Feeble galvanization of the central ends of the divided 
nerves accelerates respiration; powerful galvanization retards, and may 
even arrest, the respiratory movements. 
The Gastric branches give sensibility to the mucous coat, and through 
sympathetic filaments, which join the pneumogastrics high up in the neck, 88 
HUMAN PHYSIOLOGY. 
give motion to the muscular coat of the stomach. They influence the 
secretion of gastric juice, aid the process of digestion and absorption from 
the stomach. 
The Hepatic branches, probably through anastomosing sympathetic fila- 
ments, influence the secretion of bile, and the glycogenic function of the 
liver; division of the pneumogastrics in the neck produces congestion of 
the liver, diminishes the density of the bile, and arrests the glycogenic 
function; galvanization of the central ends exaggerates the glycogenic 
function, and makes the animal diabetic. 
The Intestinal branches give sensibility and motion to the small 
intestines, and when divided, purgatives generally fail to produce purga- 
tion. 
Function. A great sensitive nerve which, through anastomotic fila- 
ments from motor sources, influences deglutition, the action of the heart, 
the circulatory and respiratory systems, voice, the secretions of the stomach, 
intestines, and various glandular organs. 
Apparent Origin. By two sets of filaments :— 
1. A bulbar or medullary set, four or five in number, from the lateral or 
motor tract of the lower half of the medulla oblongata, below the origin of 
the pneumogastric. 
2. A spinal set, from 6 to 8 in number, from the lateral portion of the 
spinal cord, between the anterior and posterior roots of the upper four or 
five cervical nerves. 
Deep Origin. The medullary portion arises in a nucleus in the lower 
half of the floor of the 4th ventricle, common to the pneumogastric and 
glosso-pharyngeal nerves. The spinal portion has its origin in an elon- 
gated nucleus lying along the external surface of the anterior cornua of 
the spinal cord, extending down to the 5th cervical vertebra. 
Distribution. From this origin the fibres unite to form a main trunk, 
which enters the cranial cavity through the foramen magnum, where it is 
at times joined by fibres from the posterior roots of the two upper cervical 
nerves, and sends filaments to the ganglion of the root of the pneumo- 
gastric. After emerging from the cranial cavity through the jugular fora- 
men, it sends a branch to the pneumogastric, and receives others in return, 
and also from the 2d, 3d and 4th cervical nerves. It divides into two 
branches: (1) An internal or anastomotic branch, made up of filaments 
coming principally from the medulla oblongata, and is distributed to the 
muscles of the pharynx through the pharyngeal nerves coming from the 
nth Pair. Spinal Accessory. CRANIAL NERVES. 
89 
pneumogastric ; to all the muscles of the larynx, except the crico-thyroid, 
through the inferior laryngeal nerve; to the heart, by filaments which 
reach it through the pneumogastric nerve. (2) An external branch, which 
is distributed to the sterno-cleido-mastoid and trapezius muscles; these 
muscles also receiving filaments from the cervical nerves. 
Properties. At its origin it is a purely motor nerve, but in its course 
exhibits some sensibility from anastomosing fibres. 
Destruction of the medullary root, by tearing it from its attachment by 
means of forceps, impairs the action of the muscles of deglutition, and 
destroys the power of producing vocal sounds by paralysis of the laryngeal 
muscles, without, however, interfering with the respiratory movements of 
the larynx; these being controlled by other motor nerves. The normal 
rate of movement of the heart is also impaired by destruction of the medul- 
lary root. 
Irritation of the external branch throws the trapezius and sterno-mastoid 
muscles into convulsive movements, though section of the nerve does not 
produce complete paralysis, as they are also supplied with motor influence 
from the cervical nerves. The sterno-mastoid and trapezius muscles per- 
form movements antagonistic to those of respiration, fixing the head, neck 
and upper part of the thorax, and delaying the expiratory movement 
during the acts of pushing, pulling, straining, etc., and in the production 
of a prolonged vocal sound, as in singing. When the external branch 
alone is divided, in animals, they experience shortness of breath during 
exercise, from a want of coordination of the muscles of the limbs and res- 
piration; and while they can make a vocal sound, it cannot be prolonged. 
Function. Governs phonation by its influence upon the vocal move- 
ments of the glottis; influences the movements of deglutition, inhibits the 
action of the heart and controls certain respiratory movements associated 
with sustained or prolonged muscular efforts and phonation. 
12th Pair. Hypoglossal or Sublingual. 
Apparent Origin. By two groups of filaments from the medulla ob- 
longata, in the grooves between the olivary body and the anterior pyramid. 
Deep Origin. From the hypoglossal nucleus situated deeply in the sub- 
stance of the medulla, on a level with the lowest portion of the floor of the 
4th ventricle; some decussating filaments have been traced to a higher 
encephalic centre. 
Distribution. The trunk formed by the union of the root filaments 
passes out of the cranial cavity through the anterior condyloid foramen, 
occasionally receiving a filament from the lateral and posterior portion of 90 
HUMAN PHYSIOLOGY. 
the medulla oblongata. After emerging from the cranium, it sends fila- 
ments to the sympathetic and pneumogastric; it anastomoses with the 
lingual branch of the 5th pair, and receives and sends filaments to the 
upper cervical nerves. The nerve is finally distributed to the sterno-hyoid, 
sterno thyroid, omo hyoid, thyro-hyoid, stylo-glossi, hyo-glossi, genio- 
hyoid, genio-hyo-glossi, and the intrinsic muscles of the tongue. 
Properties. A purely motor nerve at its origin, but derives sensibility 
outside of the cranial cavity, from anastomosis with the cervical, pneumo- 
gastric and 5th nerves. 
Irritation of the nerve gives rise to convulsive movements of the tongue 
and slight evidences of sensibility. 
Division of the nerve abolishes all movements of the tongue, and inter- 
feres considerably with the act of deglutition. 
When the hypoglossal nerve is involved in hemiplegia, the tip of the 
tongue is directed to the paralyzed side when the tongue is protruded ; due 
to the unopposed action of the genio-hyo-glossus on the sound side. 
Articulation is considerably impaired in paralysis of this nerve; great 
difficulty being experienced in the pronunciation of the consonantal sounds. 
Mastication is performed with difficulty, from inability to retain the food 
between the teeth until it is completely triturated. 
Function. Governs all the movements of the tongue and influences 
the functions of mastication, deglutition and articulate language. 
CEREBRO-SPINAL AXIS. 
The Cerebro-Spinal Axis consists of the spinal cord, medulla oblon- 
gata, pons Varolii, cerebellum and cerebrum, exclusive of the spinal and 
cranial nerves. It is contained within the cavities of the cranium and 
spinal column, and surrounded by three membranes, the dura mater, 
arachnoid and pia mater, which protect it from injury and supply it with 
blood vessels. 
The Brain and Spinal Cord are composed of both white fibres and 
collections of grey cells, and are therefore to be regarded as conductors of 
impressions and motor impulses, as well as generators of nerve force. 
MEMBRANES. 
The Dura Mater, the most external of the three, is a tough membrane, 
composed of white fibrous tissue, arranged in bundles, which interlace in 
every direction. In the cranial cavity it lines the inner surface of the SPINAL CORD. 
91 
bones, and is attached to the edge of the foramen magnum; sends 
processes inward, forming the falx cerebri, falx cerebelli, and tentorium 
cerebelli, supporting and protecting parts of the brain. In the spinal canal 
it loosely invests the cord, and is separated from the walls of the canal by 
areolar tissue. 
The Arachnoid, the middle membrane, is a delicate serous structure 
which envelopes the brain and cord, forming the visceral layer, and is 
then reflected to the inner surface of the dura mater, forming the parietal 
layer. Between the two layers there is a small quantity of fluid which 
prevents friction by lubricating the two surfaces. 
The Pia Mater, the most internal of the three, composed of areolar 
tissue and blood vessels, covers the entire surface of the brain and cord, to 
which it is closely adherent, dipping down between the convolutions and 
fissures. It is exceedingly vascular, sending small blood vessels some 
distance into the brain and cord. 
The Cerebro-Spinal Fluid occupies the sub-arachnoid space, and the 
general ventricular cavity of the brain, which communicate by an opening, 
the foramen of Magendie, in the pia mater, at the lower portion of the 4th 
ventricle. This fluid is clear, transparent, alkaline, possesses a salt taste 
and a low specific gravity; it is composed largely of water, traces of 
albumen, glucose and mineral salts. It is secreted by the pia mater; the 
quantity is estimated from 2 to 4 fluid oz. 
The function of the cerebro-spinal fluid is to protect the brain and cord, 
by preventing concussion from without; by being easily displaced into the 
spinal canal, prevents undue pressure and insufficiency of blood to the 
brain. 
SPINAL CORD. 
The Spinal Cord varies from 16 to 18 inches in length; is half an inch 
in thickness, weighs oz., and extends from the atlas to the 2d lumbar 
vertebra, terminating in the filurn terminate. It is cylindrical in shape, 
and presents an enlargement in the lower cervical and lower dorsal 
regions, corresponding to the origin of the nerves which are distributed to 
the upper and lower extremities. The cord is divided into two lateral 
halves by the anterior and posterior fissures. It is composed of both white 
or fibrous and grey or vesicular matter, the former occupying the exterior 
of the cord, the latter the interior, where it is arranged in the form of two 
crescents, one in each lateral half, united together by the central mass, the 
grey commissure; the white matter being united in front by the white 
commissure. 92 
HUMAN PHYSIOLOGY. 
Structure of the White Matter. The white matter surrounding each 
lateral half of the cord is made up of nerve fibres, some of which are 
continuations of the nerves which enter the cord, while others are derived 
from different sources. It is subdivided into: (i) An Anterior column, 
comprising that portion between the anterior roots and the anterior fissure, 
which is again subdivided into two parts : (a) an inner portion, bordering 
the anterior median fissure, the direct pyramidal tract, or column of 
Tiirck, containing motor fibres which do not decussate, and which extends 
as far down as the middle of the dorsal region; (b) an outer portion, sur- 
rounding the anterior cornua, known as the anterior root zone, composed 
of short longitudinal fibres which serve to connect together different seg- 
ments of the spinal cord. (2) A Lateral column, the portion between the 
anterior and posterior roots, which is divisible into (a) the crossed pyra- 
midal tract, occupying the posterior portion of the lateral column, and 
containing all those fibres of the motor tract which have decussated at the 
medulla oblongata; it is composed of longitudinally running fibres which 
are connected with the multipolar nerve cells of the anterior cornua; (3) the 
direct cerebellar tract, situated upon the surface of the lateral column, 
consisting of longitudinal fibres which terminate in the cerebellum ; it first 
appears in the lumbar region, and increases as it passes upward; (<r) the 
anterior tract, lying just posterior to the anterior cornua. (3) A Pos- 
terior column, the portion included between the posterior roots and the 
posterior fissure, also divisible into two portions, (a) an inner portion, the 
postero-internal column, or the column of Goll, bordering the posterior 
median fissure, and (b) an external portion, the postero-external column, 
the column of Burdach, lying just behind the posterior roots. They are 
composed of long and short commissural fibres which connect together 
different segments of the spinal cord. 
Structure of the Grey Matter. The grey matter, arranged in the 
form of two crescents, presents an anterior and posterior horn. It is made 
up of a delicate network of fine nerve fibres (axis cylinders), supported by 
a connective tissue framework of nucleated nerve cells, which in the ante- 
rior horns are large and multipolar, and connected with the anterior roots 
of spinal nerves; in the posterior horns the nerve cells are smaller, and 
situated along the inner margin, and in the caput cornu. Small cells are 
also found in the posterior vesicular columns, and in the intermediary 
lateral tract. 93 
COURSE OF THE ANTERIOR AND POSTERIOR ROOTS. 
SPINAL CORD. 
The Anterior Roots pass through the anterior columns, horizontally, 
in straight and distinct bundles, and enter the anterior cornuae, where they 
diverge in four directions, (i) Many become connected with the pro- 
longations of the multipolar nerve cells. (2) Others leave the grey 
matter, pass through the anterior white commissure, and enter the anterior 
columns of the opposite side. (3) A considerable number enter the lateral 
columns of the same side, through which they pass to the medulla oblon- 
gata, where they decussate and finally terminate in the corpus striatum of 
the opposite side. (4) Others traverse the grey matter horizontally, and 
come into relation with the posterior roots. 
The Posterior Roots enter the posterior horns of the grey matter (1) 
through the substantia gelatinosa, (2) to the inner side; of the former, 
some bend upward and downward, and become connected with the ante- 
rior cornuse; others pass through the posterior commissure to the opposite 
side; of the latter, fibres pass into the grey matter, to the posterior vesicu- 
lar columns, passing obliquely through the posterior white columns upward 
and downward for some distance, and enter the grey matter at different 
heights. 
Decussation of Motor and Sensory Fibres. The Motor fibres, 
which conduct volitional impulses from the brain outward to the anterior 
cornuse, arise in the motor centres of the cerebrum ; they then pass down- 
ward through the corona radiata, the internal capsule, the inferior portions 
of the crura cerebri, the pons Varolii, to the medulla oblongata, where the 
motor tract of each side divides into two portions, viz: 1. The larger, 
containing 91 to 97 per cent, of the fibres, which decussates at the lower 
border of the medulla and passes down in the lateral column of the opposite 
side, and constitutes the crossed pyramidal tract. 2. The smaller, con- 
taining 3 to 9 per cent, of the fibres, does not decussate, but passes down 
the anteHor column of the same side, and constitutes the direct pyramidal 
tract, or the column of Tiirck. Some of the motor fibres of these two 
tracts, after entering the anterior cornuse of the grey matter, become con- 
nected with the large multipolar nerve cells, while others pass directly into 
the anterior roots. Through this decussation each half of the brain governs 
the muscular movements of the opposite side of the body. 
The Sensory fibres, which convey the impressions made upon the peri- 
phery to the cord and brain, pass into the cord through the posterior roots 
of spinal nerves; they then diverge and enter the grey matter at different 
levels, and at once decussate, passing to the opposite side of the grey 94 
HUMAN PHYSIOLOGY. 
matter. The sensory tract passes upward, through the cord, the medulla, 
pons Varolii, the superior portion of the crura cerebri, the posterior third 
of the internal capsule, to the sensory perceptive centre, located in the 
hippocampus major and unciate convolution (Ferrier). Through this 
decussation each half of the brain governs the sensibility of the opposite 
half of the body. 
Properties of the Spinal Cord. Irritation applied directly to the 
antero-lateral white columns produces muscular movements but no pain; 
they are, therefore, excitable but insensible. 
The surface of the posterior columns is very sensitive to direct irritation, 
especially near the origin of the posterior roots; less so toward the pos- 
terior median fissure. The sensibility is due, however, not to its own 
proper fibres, but to the fibres of the posterior roots which traverse it. 
Division of the antero-lateral columns abolishes all power of voluntary 
movement in the lower extremities. 
Division of the posterior columns impairs the power of muscular co- 
ordination, such as is witnessed in locomotor ataxia. 
The grey matter is probably both insensible and inexcitable under the 
influence of direct stimulation. 
A transverse section of one lateral half of the cord produces:—’ 
(1) On the same side, paralysis of voluntary motion and a relative or 
absolute elevation of temperature and an increased flow of blood in the 
paralyzed parts; hypersesthesia for the sense of contact, tickling, pain and 
temperature. 
(2) On the opposite side, complete ansesthesia as regards contact, pain, 
tickling and temperature, in the parts corresponding to those which are 
paralyzed in the opposite side. Complete preservation of voluntary power 
and of the muscular sense. 
A vertical section through the middle of the grey matter results in the 
loss of sensation on both sides of the body below the section, but no loss 
of voluntary power. 
FUNCTIONS OF THE SPINAL CORD. 
i. As a Conductor. The Lateral columns, particularly the posterior 
portions, the “ pyramidal tracts,” and the columns of Tiirck, are the 
channels through which pass the voluntary motor impulses from the brain 
to the large multipolar nerve cells in the anterior cornuae of grey matter, 
and through them become connected with the anterior roots which transmit 
the motor stimuli to the muscles. FUNCTIONS OF THE SPINAL CORD. 
95 
The Anterior columns, especially the portion surrounding the anterior 
cornuDs, the “ anterior radicular zones,” are composed of short longitudinal 
commissural fibres, which serve to connect together different segments of 
the spinal cord, a condition required for the coordination of muscular 
movements. 
The Posterior columns are composed of short and long commissural 
fibres which connect together different segments of the cord. They are 
insensible to direct irritation, but aid in the coordination of muscular move- 
ments in walking, standing, running, etc. Degeneration of the posterior 
columns gives rise to the lack of muscular codrdination observed in loco- 
motor ataxia. 
The Grey matter, and especially that portion immediately surrounding 
the central canal, transmits the sensory nerve fibres from the posterior roots 
up to the brain. Decussation of the sensory fibres takes place throughout 
the whole length of the grey matter. 
The Multipolar cells of the anterior cornuce are connected with the gen- 
eration and transmission of motor impulses outward; are centres for reflex 
movements; are the trophic centres for the motor nerves and muscular 
fibres to which they are distributed. The anterior roots give passage to 
the vaso-constrictor and vaso-dilator fibres which exert an influence upon 
the calibre of the blood vessels. Complete destruction of the anterior 
horns is followed by a paralysis of motion, degeneration of the anterior 
roots, atrophy of muscles and bones and an abolition of reflex movements. 
2. As an Independent Nerve Centre. 
The spinal cord, by virtue of its containing ganglionic nerve matter, is 
capable of transforming impressions made upon the centripetal nerves into 
motor impulses, which are reflected outward through centrifugal nerves to 
muscles, producing movements. These reflex movements taking place 
through the grey matter, are independent of sensation and volition. 
The mechanism involved in every reflex act is a sentient surface, a 
sensory nerve, a nerve centre, a motor nerve and muscle. 
The reflex excitability of the cord may be— 
(i) Increased by disease of the lateral columns, the administration of 
strychnia, and in frogs, by a separation of the cord from the brain, the latter 
apparently exerting an inhibitory influence over the former and depressing 
its reflex activity. 
2. Inhibited by destructive lesions of the cord, e. g., locomotor otaxia, 
atrophy of the anterior cornune, the administration of various drugs, and, in 
the frog, by irritation of certain regions of the brain. When the cerebrum 96 
HUMAN PHYSIOLOGY. 
alone is removed and the optic lobes stimulated, the time elapsing between 
the application of an irritant to a sensory surface and the resulting move- 
ment will be considerably prolonged. The optic lobes (Setchenow’s centre) 
apparently generating impulses which, descending the cord, retard its 
reflex movements. 
All movements taking place through the nervous system are of this reflex 
character, and may be divided into excito-motor, sensori-motor and ideo- 
motor. 
Classification of Reflex Movements. (Kiiss.) They may be divided 
into four groups, according to the route through which the centripetal and 
centrifugal impulses pass. 
1. Those normal reflex acts, e. g., deglutition, coughing, sneezing, walk- 
ing, etc., pathological reflex acts, e. g., tetanus, vomiting, epilepsy, which 
take place both centripetally and centrifugally, through spinal nerves. 
2. Reflex acts which take place in a centripetal direction through a 
cerebro-spinal sensory nerve, and in a centrifugal direction through a sym- 
pathetic motor nerve, usually a vaso-motor nerve, e. g., the normal reflex 
acts, which give rise to most of the secretions, pallor and blushing of the 
skin, certain movements of the iris, certain modifications in the beat of the 
heart; the pathological, which, on account of the difficulty in explaining 
their production, are termed metastatic, e. g., ophthalmia, coryza, orchitis, 
which depend on a reflex hypersemia; amaurosis, paralysis, paraplegia, 
etc., due to a reflex anaemia. 
3. Reflex movements, in which the centripetal impulse .passes through a 
sympathetic nerve, and the centrifugal through a cerebro-spinal nerve; 
most of these phenomena are pathological, e.g., convulsions from intestinal 
irritation produced by the presence of worms, eclampsia, hysteria, etc. 
4. Reflex actions, in which both the centripetal and centrifugal impulses 
pass through filaments of the sympathetic nervous system, e.g., those ob- 
scure reflex actions which preside over the secretions of the intestinal fluids, 
which unite the phenomena of the generative organs, the dilatation of the 
pupils from intestinal irritation (worms), and many pathological phenomena. 
Laws of Reflex Action. (Pfliiger.) 
1. Law of Unilaterality. If a feeble irritation be applied to one or 
more sensory nerves, movement takes place usually on one side only, and 
that upon the same side as the irritation. 
2. Law of Symmetry. If the irritation becomes sufficiently intense, 
motor reaction is manifested, in addition, in corresponding muscles of the 
opposite side of the body. FUNCTIONS OF THE SPINAL CORD. 
97 
3- Law of Intensity. Reflex movements are usually more intense on 
the side of the irritation ; at times the movements of the opposite side equal 
them in intensity, but they are usually less pronounced. 
4. Law of Radiation. If the excitation still continues to increase, it is 
propagated upward, and motor reaction takes place through centrifugal 
nerves coming from segments of the cord higher up. 
5. Law of Generalization. When the irritation becomes very intense, 
it is propagated to the medulla oblongata; motor reaction then becomes 
general, and is propagated up and down the cord, so that all the muscles 
of the body are thrown into action, the medulla oblongata acting as a focus 
whence radiate all reflex movements. 
Special Centres in the Spinal Cord. 
Genito-spinal centre. In the lower portion of the spinal cord are 
located the centres which control the sphincter muscles of the rectum and 
bladder, the erection of the penis, the emission of the semen, the action of 
the uterus during parturition, etc. 
Cilio-spinal centre. Situated in the spinal cord between the 6th 
cervical and 2d dorsal nerves; stimulation of the cord in this situation 
produces a dilatation of both pupils through filaments of the sympathetic, 
which take their origin from this region of the cord. 
Throughout the spinal cord are situated numerous centres which preside 
over the following reflexes, viz 
The patellar tendon reflex takes place through the segments from which 
arise the 2d, 3d and 4th lumbar nerves; the cremasteric reflex through the 
segment from which arise the 1st and 2d lumbar nerves; the abdominal 
reflex through the segments between the 8th and 12th dorsal nerves ; the 
epigastric reflex through the segments from which arise the 4th, 5th and 
6th dorsal nerves. 
Paralysis from Disease of the Spinal Cord. 
Seat of lesion. If it be in the lower part of the sacral canal, there is 
paralysis of the compressor urethrae, accelerator urinae, and sphincter ani 
muscles; no paralysis of the muscles of the leg. 
At the upper limit of the sacral region. Paralysis of the muscles of the 
bladder, rectum and anus; loss of sensation and motion in the muscles of 
the legs, except those supplied by the anterior crural and obturator, viz : 
psoas iliacus, Sartorius, pectineus, adductor longus, magnus and brevis, 
obturator, vastus externus and interims, etc. 
At the upper limit of the lumbar region. Sensation and motion para- 
lyzed in both legs; loss of power over the rectum and bladder; paralysis 98 
HUMAN PHYSIOLOGY. 
of the muscular walls of the abdomen interfering with expiratory move- 
ments. 
At the lower portion of the cervical region. Paralysis of the legs, etc., 
as above; in addition, paralysis of all the intercostal muscles and conse- 
quent interference with inspiratory movements; paralysis of muscles of 
the upper extremities, except those of the shoulders. 
Above the middle of the cervical region. In addition to the preceding, 
difficulty in deglutition and vocalization, contraction of the pupils, paraly- 
sis of the diaphragm, scalene muscles, intercostals, and many of the ac- 
cessory respiratory muscles; death resulting immediately, from arrest of 
respiratory movements. 
Anterior half of spinal cord. Paraplegia developing symmetrically. 
Posterior half of spinal cord. Characteristic symptoms of locomotor 
ataxia or tabes dorsalis. 
In the grey substance in the vicinity of the central canal and anterior 
horns. If the lesion be acute, symptoms characteristic of acute spinal 
paralysis manifest themselves; if chronic, symptoms characteristic of pro- 
gressive muscular atrophy. 
The Medulla Oblongata is the expanded portion of the upper part of 
the spinal cord. It is pyramidal in form and measures one and a half 
inches in length, three-quarters of an inch in breadth, half an inch in 
thickness, and is divided into two lateral halves by the anterior and pos- 
terior median fissures, which are continuous with those of the cord. Each 
half is again subdivided by minor grooves, into four columns, viz : anterior 
pyramid, lateral tract and olivary body, restiform body and posterior 
pyramid. 
1. The anterior pyramid is composed partly of fibres continuous with 
those of the anterior column of the spinal cord; but mainly of fibres 
derived from the lateral tract of the opposite side, by decussation. The 
united fibres then pass upward through the pons Varolii and crura cerebri, 
and for the most part terminate in the corpus striatum and cerebrum. 
2. The lateral tract is continuous with the lateral columns of the cord ; 
its fibres in passing upward take three directions, viz : an external bundle 
joins the restiform body, and passes into the cerebellum; an internal 
bundle decussates at the median line and joins the opposite anterior pyra- 
mid ; a middle bundle ascends beneath the olivary body, behind the pons, 
to the cerebrum, as the fasciculus teres. 
MEDULLA OBLONGATA. MEDULLA OBLONGATA. 
99 
The olivary body of each side is an oval mass, situated between the 
anterior pyramid and restiform body; it is composed of white matter exter- 
nally and grey matter internally, forming the corpus dentatum. 
3. The restiform body continues with the posterior column of the cord, 
also receives fibres from the lateral column. As the restiform bodies pass 
upward they diverge and form a space, the 4th ventricle, the floor of which 
is formed by grey matter, and then turn backward and enter the cerebellum. 
4. The posterior pyramid is a narrow, white cord bordering the posterior 
median fissure; it is continued upward, in connection with the fasciculus 
teres, to the cerebrum. 
The Grey Matter of the medulla is continuous with that of the cord. 
It is arranged with much less regularity, becoming blended with the white 
matter of the different columns, with the exception of the anterior. By 
the separation of the posterior columns, the transverse commissure is 
exposed, forming part of the floor of the 4th ventricle; special collections 
of grey matter are found in the posterior portions of the medulla, connected 
with the roots of origin of different cranial nerves. 
Properties and Functions. The medulla is excitable anteriorly, 
and sensitive posteriorly to direct irritation. It serves (1) as a conductor 
of sensitive impressions upward from the cord, through the grey matter to 
the cerebrum; (2) as a conductor of voluntary impulses from the brain to 
the spinal cord and nerves, through its anterior pyramids; (3) as a con- 
ductor of coordinating impulses from the cerebellum, through the restiform 
bodies to the spinal cord. 
As an Independent Reflex Centre. The medulla oblongata contains 
special collections of grey matter, which constitute independent nerve centres 
which preside over different functions, some of which are as follows, viz:— 
1. A centre which controls the movements of mastication, through affer- 
ent and efferent nerves. (See page 22.) 
2. A centre reflecting impressions which influence the secretion of saliva. 
(See page 23.) 
3. A centre for deglutition, whence are derived motor stimuli exciting to 
action and coordinating the muscles of the palate, pharynx and oesophagus, 
necessary for the swallowing of the food. 
NERVOUS CIRCLE OF DEGLUTITION. (2d and 3d Stages.) 
Excitor 
or 
Centripetal 
Nerves. 
Palatal branch of 5th pair. 
Pharyngeal branches of the glosso-pharyngeal. 
Superior laryngeal branches of the pneumogastric. 
GEsophageal branches of the pneumogastric. 100 
HUMAN PHYSIOLOGY. 
Pharyngeal branches of the pneumogastric, derived 
from the spinal accessory. 
Hypoglossal and branches of the cervical plexus. 
Inferior or recurrent laryngeal. 
Motor filaments of the 3d division of the 5th pair. 
Portio dura. 
Motor 
or 
Centrifugal 
Nerves. 
4. A centre which coordinates the muscles concerned in the act of 
vomiting. 
5. A Speech centre, coordinating the various muscles necessary for the 
accomplishment of articulation through the hypoglossal, facial nerves and 
the 3d division of the 5th pair. 
6. A centre for the harmonization of muscles concerned in expression, 
reflecting its impulses through the facial nerve. 
7. A Cardiac centre, which exerts (1) an accelerating influence over the 
heart’s pulsations through accelerating nerve fibres emerging from the cer- 
vical portion of the cord, entering the inferior cervical ganglion, and thence 
passing to the heart; (2) an inhibitory or retarding influence upon the 
action of the heart, through fibres of the spinal accessory nerve running in 
the trunk of the pneumogastric. 
8. A Vaso-motor centre, which by alternately contracting and dilating the 
blood vessels through nerves distributed in their walls, regulates the quantity 
of blood distributed to an organ or tissue, and thus influences nutrition, secre- 
tion and calorification. The vaso-motor centre is situated in the medulla 
oblongata and pons Varolii, between the corpora quadrigemina and the 
calamus scriptorius. The vaso-motor fibres having their origin in this 
centre descend through the interior of the cord, emerge through the anterior 
roots of spinal nerves, enter the ganglia of the sympathetic, and thence 
pass to the walls of the blood vessels, and maintain the arterial tonus ; 
they may be divided into two classes, viz: vaso-dilators, e. g., chorda 
tympani, and vaso-constrictors, e. g., sympathetic fibres. 
Division of the cord at the lower border of the medulla is followed by 
a dilatation of the entire vascular system and a marked fall of the blood 
pressure. Galvanic stimulation of the divided surface of the cord is fol- 
lowed by a contraction of the blood vessels and a rise in the blood pressure. 
9. A Diabetic centre, irritation of which causes an increase in the amount 
of urine secreted, and the appearance of a considerable quantity of sugar. 
10. A Respiratory centre, situated near the origin of the pneumogastric 
nerves, presides over the movements of respiration and its modifications, 
laughing, sighing, sobbing, sneezing, etc. It may be excited rejlexly by 
the presence of carbonic acid in the lungs irritating the terminal pneumo- PONS VAROLII. 
101 
gastric filaments; or automatically, according to the character of the blood 
circulating through it; an excess of carbonic acid or a diminution of 
oxygen increasing the number of respiratory movements; a reverse con- 
dition diminishing the respiratory movements. 
11. A Spasm centre, stimulation of which gives rise to convulsive phe- 
nomena. 
Excitor 
or 
Centripetal 
Nerves. 
NERVOUS CIRCLE OF RESPIRATION (ENTIRELY REFLEX). 
Pulmonary branches of the pneumogastric. 
Superior laryngeal. 
Trifacial, or 5th pair. 
Nerves of general sensibility. 
Sympathetic nerve. 
Motor 
or 
Centrifugal 
Nerves. 
Phrenic, distributed to the diaphragm. 
Intercostals, distributed to the intercostal muscles. 
Facial nerve, or portio dura, to the facial muscles. 
External branch of spinal accessory, to the trapezius 
and sterno-cleido-mastoid muscles. 
PONS VAROLII. 
The Pons Varolii unites together the cerebrum above, the cerebellum 
behind, and the medulla oblongata below. It consists of transverse and 
longitudinal fibres, amidst which are irregularly scattered collections of 
grey or vesicular nervous matter. 
The transverse fibres unite the two lateral halves of the cerebellum. 
The longitudinalfibres are continuous (i) with the anterior pyramids of 
the medulla oblongata, which, interlacing with the deep layers of the 
transverse fibres, ascend to the crura cerebri, forming their superficial or 
fasciculated portions; (2) with fibres derived from the olivary fasciculus, 
some of which pass to the tubercula quadrigemina, while others, uniting 
with fibres from the lateral and posterior columns of the medulla, 
in the deep or posterior portions of the crura cerebri. 
Properties and Functions. The superficial portion is insensible and 
inexcitable to direct irritation ; the deeper portions appear to be excitable, 
consisting of descending motor fibres; the posterior portions are sensible 
but inexcitable to irritation. 
Transmits motor impulses and sensory impressions from and to the 
cerebrum. 
The grey ganglionic matter consists of centres which convert impres- 102 
HUMAN PHYSIOLOGY. 
sions into conscious sensations, and originate motor impulses, these taking 
place independent of any intellectual process; they are the seat of instinct- 
ive reflex acts; the centres which assist in the co-ordination of the auto- 
matic movements of station and progression. 
CRURA CEREBRI. 
The Crura Cerebri are largely composed of the longitudinal fibres of 
the pons (anterior pyramids, fasciculi teretes); after emerging from the 
pons they increase in size, and become separated into two portions by a 
layer of dark grey matter, the locus niger. 
The superficial portion, the crusta, composed of the anterior pyramids, 
constitutes the motor tract, which terminates, for the most part, in the 
corpus striatum, but to some extent, also, in the cerebrum; the deep por- 
tion, made up of the fasciculi teretes and posterior pyramids and accessory 
fibres from the cerebellum, constitute the sensory tract (the tegmentum), 
which terminates in the optic thalamus and cerebrum. 
Function. The crura are conductors of motor impulses and sensory 
impressions; the grey matter, the locus niger, assists in the coordination 
of the complicated movements of the eyeball and iris, through the motor 
oculi communis nerve. They also assist in the harmonization of general 
muscular movements; section of one crus giving rise to peculiar move- 
ments of rotation and somersaults forward and backward. 
CORPORA QUADRIGEMINA. 
The Corpora Quadrigemina are four small, rounded eminences, two 
on each side of the median line, situated immediately behind the third 
ventricle, and beneath the posterior border of the corpus callosum. 
The anterior tubercles are oblong from before backward, and larger 
than the posterior, which are hemispherical in shape; they are greyish in 
color, but consist of white matter externally and grey matter internally. 
Both the anterior and posterior tubercles are connected with the optic 
thalami by commissural bands named the anterior and posterior brackia, 
respectively. They receive fibres from the olivary fasciculus and fibres from 
the cerebellum, which pass upward to enter the optic thalami. 
The corpora geniculata are situated, one on the inner side and one on 
the outer side of each optic tract, behind and beneath the optic thalamus, 
and from their position are named the corpora geniculata interna and 
externa ; they give origin to fibres of the optic nerve. CORPORA STRIATA AND OPTIC THALAMI. 
103 
Functions. The Tubercula quadrigemina are the physical centres of 
sight, translating the luminous impressions into visual sensations. Destruc- 
tion of these tubercles is immediately followed by a loss of the sense of 
sight; moreover, their action in vision is crossed, owing to the decussation 
of the optic tracts, so that if the tubercle of the right side be destroyed by 
disease or extirpated, in a pigeon, the sight is lost in the eye of the oppo- 
site side, and the iris loses its mobility. 
The tubercula quadrigemina as nerve centres preside over the reflex 
movements which cause a dilation or contraction of the iris; irritation of 
the tubercles causing contraction, destruction causing dilatation. Removal 
of the tubercles on one side produces a temporary loss of power of the 
opposite side of the body, and a tendency to move around an axis is 
manifested, as after a section of one crus cerebri, which, however, may be 
due to giddiness and loss of sight. 
They also assist in the coordination of the complex movements of the 
eye, and regulate the movements of the iris during the movements of 
accommodation for distance. 
CORPORA STRIATA AND OPTIC THALAMI. 
The Corpora Striata are two large ovoid collections of grey matter, 
situated at the base of the cerebrum, the larger portions of which are 
imbedded in the white matter, the smaller portions projecting into the 
anterior part of the lateral ventricle. Each striated body is divided, by a 
narrow band of white matter, into two portions, viz :— 
1. The Caudate nucleus, the intraventricular portion, which is conical 
in shape, having its apex directed backward, as a narrow, tail-like process. 
2. The Lenticular nucleus, imbedded in the white matter, and for the 
most part external to the ventricle; on the outer side of the lenticular 
nucleus is found a narrow band of white matter, the external capsule ; 
and between it and the convolutions of the island of Reil, a thin band of 
grey matter, the claustrum ; the corpora striata are greyish in color, and 
when divided present transverse striations, from the intermingling of white 
fibre and grey cells. 
The Optic Thalami are two oblong masses situated in the ventricles 
posterior to the corpora striata, and resting upon the posterior portion of 
the crura cerebri. The internal surface projecting into the lateral ven- 
tricles is white, but the interior is greyish, from a commingling of both 
white fibres and grey cells. Separating the lenticular nucleus from the 
caudate nucleus and the optic thalamus is a band of white tissue, the 
internal capsule. 104 
HUMAN PHYSIOLOGY. 
The Internal capsule is a narrow, bent tract of white matter, and is, for 
the most part, an expansion of the motor tract of the crura cerebri. It 
consists of two segments, an anterior, situated between the caudate 
nucleus and the anterior surface of the lenticular nucleus, and a posterior, 
situated between the optic thalamus and the posterior surface of the len- 
ticular nucleus. These two segments unite at an obtuse angle, which is 
directed towards the median line. Pathological observation has shown 
that the nerve fibres of the direct and crossed pyramidal tracts can be 
traced upward through the anterior two-thirds of the posterior segment, 
into the centrum ovale, where, for the most part, they are lost; a portion, 
however, remaining united, ascend higher and terminate in the paracentral 
lobule, the superior extremity of the ascending frontal and parietal convo- 
lutions. The sensory tract can be traced upward, through the posterior 
third, into the cerebrum, where they probably terminate in the hippo- 
campus major and unciate convolution. 
Functions. The Corpora striata are the centres in which terminate 
some of the fibres of the superficial or motor tract of the crura cerebri; 
others pass upward through the internal capsule, to be distributed to the 
cerebrum. It might be inferred, from their anatomical relations, that they 
are motor centres. Irritation by a weak galvanic current produces mus- 
cular movements of the opposite side of the body; destruction of their 
substance by a hemorrhage, as in apoplexy, is followed by a paralysis of 
motion of the opposite side of the body, but there is no loss of sensation. 
When the hemorrhagic destruction involves the fibres of the anterior two- 
thirds of the posterior segment of the internal capsule, and thus separates 
them from their trophic centres in the cortical motor region, a descending 
degeneration is established, which involves the direct pyramidal tract of 
the same side and the crossed pyramidal tract of the opposite side. 
Destruction of the posterior one-third of the posterior segment of the 
internal capsule is followed by a loss of sensation on the opposite side of 
the body, and a loss of the senses of smell and vision on the same 
side (Charcot). The precise function of the corpora striata is unknown, 
but they are in some way connected with motion. 
The Optic thalami receive the fibres of the tegmentum, the posterior 
portion of the crura cerebri. They are insensible and inexcitable to direct 
irritation. Removal of one optic thalamus, or destruction of its substance 
by disease or hemorrhage, is followed by a loss of sensibility of the opposite 
side of the body, but there is no loss of motion; their precise function is 
also unknown, but in some way connected with sensation. In both cases 
their action is crossed. CEREBELLUM. 
105 
CEREBELLUM. 
The Cerebellum is situated in the inferior fosste of the occipital bone, 
beneath the posterior lobes of the cerebrum. It attains its maximum 
weight, which is about 5 oz., between the twenty-fifth and fortieth years; 
the proportion between the cerebellum and cerebrum being 1 to 8£. 
It is composed of two lateral hemispheres and a central elongated lobe, 
the vermifor?n process; the two hemispheres are connected with each 
other by the fibres of the middle peduncle forming the superficial portion 
of the pons Varolii. It is brought into connection with the medtilla 
oblongata and spinal cord, through the prolongation of the restiform bodies; 
with the cerebrum, by fibres passing upward beneath the corpora quadri- 
gemina and the optic thalami, and then form part of the diverging 
cerebral fibres. 
Structure. It is composed of both white and grey matter, the former 
being internal, the latter external, and convoluted, for economy of space. 
The IVhite matter consists of a central stem, in the interior of which is 
a dentated capsule of grey matter, the corpus dentatum. From the external 
surface of the stem of white matter processes are given off, forming the 
lamina:, which are covered with grey matter. 
The Grey matter is convoluted and covers externally the laminated pro- 
cesses; a vertical section through the grey matter reveals the following 
structures: — 
1. A delicate connective tissue layer, just beneath the pia mater, contain- 
ing rounded corpuscles, and branching fibres passing toward the external 
surface. 
2. The cells of Purkinje, forming a layer of large, nucleated, branched 
nerve cells sending off processes to the external layer. 
3. A granular layer of small, but numerous corpuscles. 
4. Nerve fibre layer, formed by a portion of the white matter. 
Properties and Functions. Irritation of the cerebellum is not fol- 
lowed by any evidences either of pain or convulsive movements; it is, 
therefore, insensible and inexcitable. 
Co-ordination of Movements. Removal of the superficial portions 
of the cerebellum in pigeons produces feebleness and want of harmony 
in the muscular movements; as successive slices are removed, the move- 
ments become more irregular, and the pigeon becomes restless; when 
the last portions are removed, all power of flying, walking, standing, etc., 
is entirely gone, and the equilibrium cannot be maintained, the power of 106 
HUMAN PHYSIOLOGY. 
coordinating muscular movements being entirely gone. The same results 
have been obtained by operating on all classes of animals. 
The following symptoms were noticed by Wagner, after removing the 
whole or a large part of the cerebellum. I. A tendency on the part of 
the animal to throw itself on one side, and to extend the legs as far as 
possible. 2. Torsion of the head on the neck. 3. Trembling of the 
muscles of the body, which was general. 4. Vomiting and occasionally 
liquid evacuations. 
Forced Movements. Division of one crura cerebelli causes the animal 
to fall on one side and roll rapidly on its longitudinal axis. According to 
Schiff, if the peduncle be divided from behind, the animal falls on the 
same side as the injury; if the section be made in front, the animal turns 
to the opposite side. 
Disease of the cerebellum partially corroborates the results of experi- 
ments ; in many cases symptoms of unsteadiness of gait, from a want of 
coordination, have been noticed. 
Comparative anatomy reveals a remarkable correspondence between 
the development of the cerebellum and the complexity of muscular actions. 
It attains a much greater development, relatively to the rest of the brain, 
in those animals whose movements are very complex and varied in char- 
acter, such as the kangaroo, shark and swallow. 
The cerebellum may possibly exert some influence over the sexual func- 
tion, but physiological and pathological facts are opposed to the idea of 
its being the seat of the sexual instinct. It appears to be simply a centre 
for the coordination and equilibration of muscular movements. 
The Cerebrum is the largest portion of the encephalic mass, constitut- 
ing about four-fifths of its weight; the average weight in the adult male 
is from 48 to 50 oz., or about 3 pounds, while in the adult female it is 
about 5 oz. less. After the age of 40 the weight of the cerebrum gradually 
diminishes at the rate of one ounce every ten years. In idiots the brain 
weight is often below the normal, at times not amounting to more than 20 
ounces. 
The Blood Supply to the cerebrum is unusually large, considering its 
comparative bulk; nearly one-fifth of the entire volume of blood being 
distributed to it by the carotid and vertebral arteries. These vessels anas- 
tomose so freely, and are so arranged within the cavity of the cranium, that 
an obstruction in one vessel will not interfere with the regular supply of 
CEREBRUM. CEREBRUM. 
107 
blood to the parts to which its branches are distributed. A diminished 
amount, or complete cessation, of the supply of blood is at once followed 
by a suspension of its functional activity. 
The cerebrum is connected with the pons Varolii and medulla oblongata 
through the crura cerebri, and with the cerebellum, through the superior 
peduncles. It is divided into two lateral halves, or hemispheres, by the 
longitudinal fissure running from before backward in the median line; 
each hemisphere is composed of both white and grey matter, the former 
being internal, the latter external; it covers the surfaces of the hemisphere 
which are infolded, forming convolutions, for economy of space. 
Fissures. 
1. The Fissure of Sylvius is one of the most important; it is the first to 
appear in the development of the foetal brain, being visible at about the 
third month; in the adult it is quite deep and well marked, running from 
the under surface of the brain upward, outward and backward, and forms 
a boundary between the frontal and temporo-sphenoidal lobes. 
2. The Fissure of Rolando is second in importance, and runs from a 
point on the convexity near the median line transversely outward and 
downward toward the fissure of Sylvius, but does not enter it. It sepa- 
rates the frontal from the parietal lobe. 
3. The Parietal fissure, arising a short distance behind the fissure of 
Rolando, upon the convexity of the hemisphere, runs downward and 
backward to its posterior extremity. 
Secondary fissures of importance are found in different lobes of the 
cerebrum, separating the various convolutions. In the anterior lobe are 
found the pre-central, superior frontal and inferior frontal fissures; in the 
occipital lobe, are found the parieto-occipital and the calcarine fissures. 
Convolutions. Frontal Lobe. 
The Ascending frontal convolution, situated in front of the fissure of 
Rolando, runs downward and forward; it is continuous above with the 
anterior frontal, and below with the inferior frontal convolution. 
The Superior frontal convolution is bounded internally by the longitu- 
dinal fissure, and externally by the superior frontal fissure; it is connected 
with the superior end of the frontal convolution, and runs downward and 
forward to the anterior extremity of the frontal lobe, where it turns back- 
ward, and rests upon the orbital plate of the frontal bone. 
The Middle frontal convolution, the largest of the three, runs from 
behind forward, along the sides of the lobe, to its anterior part; it is 
bounded above by the superior and below by the inferior frontal fissures. 108 
HUMAN PHYSIOLOGY. 
The Inferior frontal convolution winds around the ascending branch of 
the fissure of Sylvius, in the anterior and inferior portion of the cerebrum. 
Parietal Lobe. The Ascending parietal convolution is situated just 
behind the fissure of Rolando, running downward and forward; above, it 
becomes continuous with the upper parietal convolution, and below, winds 
around to be united with the ascending frontal. 
The Upper parietal convolution is situated between the parietal and 
longitudinal fissures. 
The Supra-marginal convolution winds around the superior extremity 
of the fissure of Sylvius. 
The Angular convolution, a continuation of the preceding, follows the 
parietal fissure to its posterior extremity, and then makes a sharp angle 
downward and forward. 
Temporo-sphenoidal Lobe. Contains three well marked convolutions, 
the superior, middle and inferior, separated by well defined fissures, and 
continuous posteriorly with the convolutions of the parietal lobe. 
The Occipital Lobe lies behind the parieto-occipital fissure, and contains 
the superior, middle and inferior convolutions, not well marked. 
The Central Lobe or Island of Reil, situated at the bifurcation of the 
fissure of Sylvius, is a triangular-shaped cluster of six convolutions, the 
gyri operti, which are connected with those of the frontal, parietal, and 
temporo-sphenoidal lobes. 
Structure. The Grey matter of the cerebrum, about one-eighth of an 
inch thick, is composed of five layers of nerve cells: (x) a superficial layer, 
containing few small multipolar ganglion cells; (2) small ganglion cells, 
pyramidal in shape; (3) a layer of large pyramidal ganglion cells with 
processes running off superiorly and laterally; (4) the granular formation 
containing nerve cells; (5) spindle shaped and branching nerve cells of 
moderate size. 
The White Matter consists of three distinct sets of fibres— 
1. The diverging or peduncular fibres are mainly derived from the 
columns of the cord and medulla oblongata; passing upward through the 
crura cerebri, they receive accessory fibres from the olivary fasciculus, 
corpora quadrigemina and cerebellum. Some of the fibres terminate in 
the optic thalami and corpora striata, while others radiate into the anterior, 
middle and posterior lobes of the cerebrum. 
2. The transverse commissural fibres connect together the two hemi- 
spheres, through the corpus callosum and anterior and posterior commis- 
sures. CEREBRUM. 
109 
3- The longitudinal commissural fibres connect together different parts 
of the same hemisphere. 
Functions. The cerebral hemispheres are the centres of the nervous 
system through which are manifested all the phenomena of the mind; 
they are the centres in which impressions are registered, and reproduced 
subsequently as ideas; they are the seat of intelligence, reason and will. 
However important a centre the cerebrum may be, for the exhibition of 
this highest form of nervous action, it is not directly essential for the con- 
tinuance of life; for it does not exert any control over those automatic 
reflex acts, such as respiration, circulation, etc., which regulate the func- 
tions of organic life. 
From the study of comparative anatomy, pathology, vivisection, etc., 
evidence has been obtained which throws some light upon the physiology 
of the cerebral hemispheres. 
1. Comparative Anatomy shows that there is a general connection be- 
tween the size of the brain, its texture, the depth and number of convolu- 
tions, and the exhibition of mental power. Throughout the entire animal 
series, the increase in intelligence goes hand in hand with an increase in 
the development of the brain. In man there is an enormous increase in 
size over that of the highest animals, the anthropoids. The most cultivated 
races of men have the greatest cranial capacity; that of the educated 
European being about 116 cubic inches, that of the Australian being about 
60 cubic inches, a difference of 56 cubic inches. Men distinguished for 
great mental power usually have large and well developed brains; that of 
Cuvier weighed 64 oz.; that of Abercrombie 63 oz.; the average being 
about 48 to 50 oz.; not only the size, but above all, the texture of the 
brain, must be taken into consideration. 
2. Pathology. Any severe injury or disease disorganizing the hemi- 
spheres is at once attended by a disturbance, or entire suspension of mental 
activity. A blow on the head producing concussion, or undue pressure 
from cerebral hemorrhage destroys consciousness; physical and chemical 
alterations in the grey matter have been shown to coexist with insanity, 
loss of memory, speech, etc. Congenital defects of organization from im- 
perfect development are usually accompanied by a corresponding deficiency 
of intellectual power and the higher instincts. Under these circumstances 
no great advance in mental development can be possible, and the intelli- 
gence remains at a low grade. In congenital idiocy not only is the brain 
of small size, but it is wanting in proper chemical composition; phosphorus, 
a characteristic ingredient of the nervous tissue, being largely diminished 
in amount. 110 
HUMAN PHYSIOLOGY. 
3. Experimentation upon the lower animals by removing the cerebral 
hemispheres is attended by results similar to those observed in disease and 
injury. Removal of the cerebrum in pigeons produces complete abolition 
of intelligence, and destroys the capability of performing spontaneous 
movements. The pigeon remains in a condition of profound stupor, which 
is not accompanied, however, by a loss of sensation, or the power of pro- 
ducing reflex or instinctive movements. The pigeon can be temporarily 
aroused by pinching the feet, loud noises, light placed before the eyes, etc., 
but soon relapses into a state of quietude, being unable to remember im- 
pressions and connect them with any train of ideas; the faculties of 
memory, reason and judgment being completely abolished. 
LOCALIZATION OF FUNCTIONS. 
The Faculty of articulate language, by which the individual associates 
ideas and words, comprises two distinct faculties, viz : i. The power of 
recalling particular words; 2. The coordination of muscles necessary for 
their articulation. 
Aphasia is a condition in which the power of expressing ideas in words 
is completely lost. Pathological observation has shown that this condition 
is frequently associated with disease of the 3d frontal convolution of the 
left side, and also the convolutions of the island of Reil, parts nourished by 
the middle cerebral artery. It usually co-exists with right hemiplegia ; at 
times aphasia results from disease of corresponding structures of the 
right side. The faculty of articulate language may be located in the 
3d frontal convolution and the island of Reil, usually on the left side of 
the brain. 
Motor Centres. The grey matter covering the cerebral hemispheres 
is both insensible and inexcitable to ordinary mechanical and chemical 
stimuli; but when a galvanic current of low intensity is applied to par- 
ticular regions of the cerebrum of a monkey, in which the general 
arrangement of the convolutions approximates that of man, definite co- 
ordinate movements occur on the opposite side of the body, e. g., rotation, 
flexion and extension of the limbs, and movements of the facial muscles. 
The regions in which the rnotor centres are located are the convolutions 
around the fissure of Rolando, especially the ascending frontal and the 
ascending parietal. Destruction of the grey matter of these convolutions 
is followed by a paralysis of motion on the opposite side of the body; 
destruction of circumscribed areas in these convolutions, causes paralysis 
of the groups of muscles excited to action by electrical stimulation of such 
areas. SYMPATHETIC NERVOUS SYSTEM. 
111 
The antero-frontal and occipital lobes are not excitable to electrical 
stimulation. 
Special Centres. The superior and middle frontal convolutions 
appear to be connected with the intellectual faculties; ablation of these 
convolutions causes a marked impairment of the intelligence and of the 
faculty of attentive observation, without impairing either sensation or motion. 
The Visual centre is located in the angular convolution. If this centre 
be destroyed, blindness of the opposite eye results, which is, however, only 
temporary if the opposite angular convolution be intact; destruction of 
both causes a complete and permanent loss of visual perceptions. 
The Auditory and Taste centres are located in the superior and inferior 
temporo-sphenoidal convolutions respectively; destruction of these regions 
abolishes the sense of hearing and taste. The sense of smell is situated in 
the uncinate convolution or cornu ammonis. 
Systemic sensations are probably located in the occipital lobes; their 
ablation is followed by a state of great depression, loss of appetite, and a 
refusal to take food. 
The centre for sensory impressions is located in the posterior portion of 
the cerebrum; destruction of the posterior portion of the internal capsule 
causes loss of sensation on the opposite side of body. 
SYMPATHETIC NERVOUS SYSTEM. 
The Sympathetic Nervous System consists of a chain of ganglia 
connected together by longitudinal nerve filaments, situated on each side 
of the spinal column, running from above downward. The two gangli- 
onic cords are connected together in the interior of the cranium by the 
ganglion of Ribes, on the anterior communicating artery, and terminate in 
the ganglion impar, situated at the tip of the coccyx. 
The chain of ganglia is divided into groups and named according to the 
localities in which they are found, viz: cranial, four in number; cervical, 
three; thoracic, twelve; lumbar, five ; sacral, five; coccygeal, one. Each 
ganglion consists of a collection of vesicular nervous matter, among which 
are found tubular and gelatinous nerve fibres. The ganglia are reinforced 
by motor and sensory fibres from the cerebro-spinal nervous system. 
The Ganglia are distinct nerve fibres, from which branches are dis- 
tributed to glands, arteries, muscles, and to the cerebral and spinal nerves; 
many pass, also, to the visceral ganglia, e. g., cardiac, semilunar, pelvic, 
etc. 112 
HUMAN PHYSIOLOGY. 
Cephalic Ganglia. 
1. The Ophthalmic or Ciliary ganglion is situated in the orbital cavity 
posterior to the eyeball; it is of small size, and of a reddish grey color; 
receives filaments of communication from the motor oculi, ophthalmic 
branch of the 5th pair, and the carotid plexus. Its filaments of distribu- 
tion are the ciliary nerves which pass to the iris and ciliary muscle. 
Function. It is the centre through which the reflex acts take place by 
which the pupil is contracted or dilated; controls the movement of 
accommodation for vision at different distances. 
2. The Spheno-palatine, or Meckel’s ganglion, triangular in shape, is 
situated in the spheno-maxillary fossa; receives filaments from the facial 
(Vidian nerve), and the superior maxillary branch of the 5th nerve. Its 
filaments of distribution pass to the gums, the soft palate, levator palati, 
and azygos uvulae muscles. 
3. The Otic, or Arnold’s ganglion, is of small size, oval in shape, and 
situated beneath the foramen ovale; receives a motor filament from the 
facial and sensory filaments from the glosso-pharyngeal and 5th nerve; 
sends filaments to the mucous membrane of the tympanic cavity and to the 
tensor tympani muscle. 
4. The Submaxillary ganglion, situated in the sub-maxillary gland, 
receives motor filaments from the chorda tympani and sensory filaments 
from the lingual branch of the 5th nerve. Regulates to some extent the 
secretion of saliva. 
Cervical Ganglia. 
The Superior cervical ganglion is fusiform in shape, of a greyish-red 
color, and situated opposite the 2d and 3d cervical vertebrae; it sends 
branches to form the carotid and cavernous plexuses which follow the 
course of the carotid arteries to their distribution; also sends branches 
to join the glosso-pharyngeal and pneumogastric, to form the pharyngeal 
plexus. 
The Middle cervical ganglion, the smallest of the three, is occasionally 
wanting; it is situated opposite the 5th cervical vertebra; sends branches 
to the superior and inferior cervical ganglion, and to the thyroid artery. 
The Inferior cervical ganglion, irregular in form, is situated opposite the 
last cervical vertebra; it is frequently fused with the first thoracic ganglion. 
The superior, middle and inferior cardiac nerves, arising from these 
cervical ganglia, pass downward and forward to form the deep and super- 
ficial cardiac plexuses located at the bifurcation of the trachea, from which 
branches are distributed to the heart, coronary arteries, etc. SYMPATHETIC NERVOUS SYSTEM. 
113 
The Thoracic Ganglia are usually twelve in number, placed against 
the heads of the ribs behind the pleura; they are small in size and grey in 
color; they communicate with the cerebro-spinal nerves by two filaments, 
one of which is white, the other grey. 
The great splanchnic nerve is formed by the union of branches from the 
sixth, seventh, eighth and ninth ganglia; it passes through the diaphragm 
to the semi-lunar ganglion. 
The lesser splanchnic nerve is formed by the union of filaments from the 
tenth and eleventh ganglia, and is distributed to the coeliac plexus. 
The renal splanchnic nerve arises from the last thoracic ganglion and 
terminates in the renal plexus. 
The semi-lunar ganglia, the largest of the sympathetic, are situated by 
the side of the coeliac axis; they send radiating branches to form the solar 
plexus; from the various plexuses, nerves follow the gastric, splenic, 
hepatic, renal, etc., arteries, into the different abdominal viscera. 
The Lumbar Ganglia, four in number, are placed upon the bodies of 
the vertebra; they give off branches which unite to form the aortic lumbar 
plexus and the hypogastric plexus, and follow the blood vessels to their 
terminations. 
The Sacral and Coccygeal Ganglia send filaments of distribution to 
all the blood vessels of the pelvic viscera. 
Properties and Functions. The sympathetic nerve possesses both 
sensibility and the power of exciting motion, but these properties are much 
less decided than in the cerebro-spinal system. Irritation of the ganglia 
does not produce any evidence of pain until some time has elapsed. If 
caustic soda be applied to the semi-lunar ganglia, or a galvanic current be 
passed through the splanchnic nerves, no instantaneous effect is noticed, as 
in the case of the cerebro-spinal nerves ; but in the course of a few seconds 
a slow, progressive contraction of the muscular coat of the intestines is 
established, which continues for some time after the irritation is removed. 
Division of the sympathetic nerve in the neck is followed by a vascular 
congestion of the parts above the section on the corresponding side, attended 
by an increase in the temperature; not only is there an increase in the 
amount of blood, but the rapidity of the blood current is very much 
hastened, and the blood in the veins becomes of a brighter color. Gal- 
vanization of the upper end of the divided nerve causes all of the preced- 
ing phenomena to disappear; the congestion decreases, the temperature 
falls, and the venous blood becomes dark again. 
The sympathetic exerts a similar influence upon the circulation of the 114 
HUMAN PHYSIOLOGY. 
limbs and the glandular organs; destruction of the first thoracic ganglion 
and division of the nerves forming the lumbar and sacral plexuses is 
followed by a dilatation of the vessels, an increased rapidity of the circu- 
lation, and an elevation of temperature in the anterior and posterior 
limbs; galvanization of the peripheral ends of these nerves causes all of 
these phenomena to disappear. Division of the splanchnic nerve causes 
a dilatation of the blood vessel of the intestine. 
These phenomena of the sympathetic nerve system are dependent upon 
the presence of vaso-motor nerves which, under normal circumstances, 
exert a tonic influence upon the blood vessels. These nerves, derived 
from the cerebro-spinal system, the medulla oblongata, leave the spinal 
cord by the rami communicantes, enter the sympathetic ganglia, and 
finally terminate in the muscular wall of the blood vessels. 
Sleep is a periodical condition of the nervous system, in which there is 
a partial or complete cessation of the activities of the higher nerve centres. 
The cause of sleep is a diminution in the quantity of blood, occasioned by 
a contraction of the smaller arteries under the influence of the vaso-motor 
nerves. 
During the waking state the brain undergoes a physiological waste as a 
result of the exercise of its functions; after.a certain length of time its 
activities become enfeebled, and a condition of repose ensues, during which 
a regeneration of its substance takes place. 
When the brain becomes enfeebled there is a diminished molecular 
activity and an accumulation of waste products; under these circumstances 
it ceases to dominate the medulla oblongata and the spinal cord. These 
centres then act more vigorously, and diminish the calibre of the cerebral 
blood vessels through the action of the vaso-motor nerves, producing a con- 
dition of physiological anaemia and sleep; during this state waste products 
are removed, force is stored up, nutrition is restored, and waking finally 
occurs. 
THE SENSE OF TOUCH. 
The Sense of Touch is a modification of general sensibility, and 
located in the skin, which is especially adapted for this purpose, on account 
of the number of nerves and papillary elevations it possesses. The struc- 
tures of the skin and the modes of terminations of the sensory nerves have 
already been considered. 
The Tactile Sensibility varies in acuteness in different portions of the 
body; being most marked in those regions in which the tactile corpuscles THE SENSE OF TOUCH. 
115 
are most abundant, e. g., the palmar surface of the third phalanges of the 
fingers and thumb. 
The relative sensibility of different portions of the body has been ascer- 
tained by means of a pair of compasses, the points of which are guarded 
by cork, and then determining how closely they could be brought together, 
and yet be felt at two distinct points. The following are some of the 
measurements:— 
Point of tongue of a line. 
Palmar surface of third phalanx I line. 
Red surface of lips 2 lines. 
Palmar surface of metacarpus 3 “ 
Tip of the nose 3 “ 
Part of lips covered by skin....4 4 “ 
Palm of hand 5 “ 
Lower part of forehead 10 “ 
Back of hand 14 “ 
Dorsum of foot 18 “ 
Middle of the thigh 30 “ 
The sense of touch communicates to the mind the idea of resistance 
only, and the varying degrees of resistance offered to the sensory nerves 
enables us to estimate, with the aid of the muscular sense, the qualities of 
hardness and softness of external objects. The idea of space or exten- 
sion is obtained when the sensory surface or the external object changes 
its place in regard to the other; the character of the surface, its rough- 
ness or smoothness, is estimated by the impressions made upon the tactile 
papillae. 
Appreciation of Temperature. The general surface of the body is more 
or less sensitive to differences of temperature, though this sensation is 
separate from that of touch ; whether there are nerves especially adapted 
for the conduction of this sensation has not been fully determined. Under 
pathological conditions, however, the sense of touch may be abolished, 
while the appreciation of changes in temperature may remain normal. 
The cutaneous surface varies in its sensibility to temperature in different 
parts of the body, and depends, to some extent, upon the thickness of the 
skin, exposure, habit, etc.; the inner surface of the elbow is more sensi- 
tive to changes in temperature than the outer portion of the arm; the 
left hand is more sensitive than the right; the mucous membrane less so 
than the skin. 
Excessive heat or cold has the same effect upon the sensibility ; the 
temperatures most readily appreciated are those between 50° F., and 1150 F. 116 
HUMAN PHYSIOLOGY. 
The sensations of pain and tickling appear to be conducted to the brain, 
also, by nerves different from those of touch; in abnormal conditions the 
appreciation of pain may be entirely lost, while touch remains unim- 
paired. 
THE SENSE OF TASTE. 
The Sense of Taste is localized mainly in the mucous membrane 
covering the superior surface of the tongue. 
The Tongue is situated in the floor of the mouth ; its base is directed 
backward, and connected with the hyoid bone, by numerous muscles, with 
the epiglottis and soft palate ; its apex is directed forward against the pos- 
terior surface of the teeth. 
The substance of the tongue is made up of intrinsic muscular fibres, 
the linguales ; it is attached to surrounding parts, and its various move- 
ments performed by the extrinsic muscles, e. g., stylo-glossus, genio-hyo- 
glossus, etc. 
The mucous membrane covering the tongue is continuous with that 
lining the commencement of the alimentary canal, and is furnished with 
vascular and nervous papillae. 
The papillce are analogous in their structure to those of the skin, and 
are distributed over the dorsum of the tongue, giving to it its characteristic 
roughness. 
There are three principal varieties :— 
1. The filiform papillce are most numerous, and cover the anterior two- 
thirds of the tongue; they are conical or filiform in shape, often pro- 
longed into filamentous tufts, of a whitish color, and covered by horny 
epithelium. 
2. The fungiform papillce are found chiefly at the tip and sides of the 
tongue; they are larger than the preceding, and may be recognized by 
their deep red color. 
3. The circumvallate papillce are rounded eminences, from 8 to 10 in 
number, situated at the base of the tongue, where they form a V-shaped 
figure. They are quite large, and consist of a central projection of 
mucous membrane, surrounded by a wall, or circumvallation, from which 
they derive their name. 
The Taste Beakers, supposed to be the true organs of taste, are flask- 
like bodies, ovoid in form, about the of an inch in length, situated in 
the epithelial covering of the mucous membrane, on the circumvallate 
papilla;. They consist of a number of fusiform, narrow cells, and curved THE SENSE OF SMELL. 
117 
so as to form the walls of this flask-like body; in the interior are elongated 
cells, with large, clear nuclei, the taste cells. 
Nerves of Taste. The chorda tympani nerve, a branch of the facial, 
after leaving the cavity of the tympanum, joins the 3d division of the 5th 
nerve between the two pterygoid muscles, and then passes forward in the 
lingual branches, to be distributed to the mucous membrane of the anterior 
two-thirds of the tongue. Division or disease of this nerve is followed by 
a loss of taste in the part to which it is distributed. 
The glosso-pharyngeal enters the tongue at the posterior border of the 
hyo-glossus muscle, and is distributed to the mucous membrane of the base 
and sides of the tongue, fauces, etc. 
The lingual branch of the trifacial nerve endows the tongue with 
general sensibility; the hypoglossal endows it with motion. 
The nerves of taste in the superficial layer of the mucous membrane form 
a fine plexus from which branches pass to the epithelium and penetrate it; 
others enter the taste beakers, and are directly connected with the taste cells. 
The seat of the sense of taste has been shown by experiment to be the 
whole of the mucous membrane over the dorsum of the tongue, soft pal- 
ate, fauces, and upper part of the pharynx. 
The Sense of Taste enables us to distinguish the savor of substances 
introduced into the mouth, which is different from tactile sensibility. The 
sapid quality of substances appreciated by the tongue are designated as 
bitter, sweet, alkaline, sour, salt, etc. 
The Essential Conditions for the production of the impressions of 
taste are (1) a state of solubility of the food; (2) a free secretion of the 
saliva, and (3) active movements on the part of the tongue, exerting 
pressure against the roof of the mouth, gums, etc., thus aiding the solution 
of various articles and their osmosis into the lingual papillae. Sapid sub- 
stances, when in a state of solution, pass into the interior of the taste 
beakers and come into contact, through the medium of the taste cells, 
with the terminal filaments of the gustatory nerves. 
THE SENSE OF SMELL. 
The Sense of Smell is located in the mucous membrane lining the 
upper part of the nasal cavity, in which the olfactory nerves are distributed. 
The Nasal Fossae are two cavities, irregular in shape, separated by 
the vomer, the perpendicular plate of the ethmoid bone, and the triangular 
cartilage. They open anteriorly and posteriorly by the anterior and pos- 118 
HUMAN PHYSIOLOGY. 
terior nares, the latter communicating with the pharynx. They are lined 
by mucous membrane, of which the only portion capable of receiving 
odorous impressions is the part lining the upper one-third of the fossae. 
The Olfactory Nerves, arising by three roots from the posterior and 
inferior surface of the anterior lobes, pass forward to the cribriform plate of 
the ethmoid bone, where they each expand into an oblong body, the olfactory 
bulb. From its under surface from 15 to 20 filaments pass downward 
through the foramina, to be distributed to the olfactory mucous membrane, 
where they terminate in long, delicate, spindle-shaped cells, the olfactory 
cells, situated between the ordinary epithelial cells. 
The olfactory bulbs are the centres in which odorous impressions are 
perceived as sensations; destruction of these bulbs being attended by an 
abolition of the sense of smell. 
In animals which possess an acute sense of smell, there is a correspond- 
ing increase in the development of the olfactory bulbs. 
The Essential Conditions for the sense of smell are, (1) a special 
nerve centre capable of receiving impressions and transforming them into 
odorous sensations. (2) Emanations from bodies which are in a gaseous 
or vaporous condition. (3) The odorous emanations must be drawn 
freely through the nasal fossse; if the odor be very faint, a peculiar inspira- 
tory movement is made, by which the air is forcibly brought into contact 
with the olfactory filaments. The secretions of the nasal fossse probably 
dissolve the odorous particles. 
Various substances, as ammonia, horseradish, etc., excite the sensibility 
of the mucous membrane, which must be distinguished from the perception 
of true odors. 
THE SENSE OF SIGHT. 
The Eyeball. The eyeball, or organ of vision, is situated within the 
orbital cavity, and loosely held in position by the fibrous capsule of Tenon. 
It rests upon a cushion of fat, which never disappears, except in cases of 
extreme starvation; it is protected from injury by the bony orbital walls, 
and is so situated as to permit an extensive range of vision. 
Blood vessels and Nerves. The structures of the eyeball are sup- 
plied with blood by the ciliary arteries, which pierce the posterior surface 
around the optic nerve. 
The Ciliary or Ophthalmic ganglion, about the size of a pin’s head, 
situated in the posterior portion of the orbital cavity, receives filaments of 
communication from the trifacial or 5th nerve, the motor oculi or 3d nerve, THE SENSE OF SIGHT. 
119 
and the sympathetic. From its anterior portion are given off the ciliary 
nerves, which enter the ball posteriorly and are distributed to the structures 
of which it is composed. 
Structure. The form of the eyeball is that of a sphere; it is about 
one inch in the transverse diameter, and a little longer in the antero-posterior 
diameter, on account of its having the segment of a smaller sphere inserted 
into the anterior surface. It is composed of 3 coats; in its interior is con- 
tained the refracting apparatus.] 
The Sclerotic and Cornea together form the external coat of the eye; 
the former covering the posterior |, the latter covering the anterior A. 
The sclerotic is a dense, opaque, fibrous membrane, varying in thickness 
from the to the of an inch; it is composed of connective tissue and is 
slightly vascular. Posteriorly it is continuous with the sheath of the optic 
nerve, and is pierced by that nerve, as well as by the ciliary vessels and 
nerves; anteriorly its fibres become quite pale, and after passing into the 
cornea, transparent. It is a protective covering, and gives attachment to 
the tendons of the muscles by which the eyeball is moved. 
The Cornea is a non-vascular, transparent membrane, composed for the 
most part of connective tissue in which are contained stellate corpuscles filled 
with a clear fluid. It is covered anteriorly by the basement membrane of 
the conjunctiva, upon which rests several layers of epithelial cells; pos- 
teriorly it is lined by the membrane of Descemet, which is reflected on to 
the anterior surface of the iris. 
The Choroid, the Iris, the Ciliary Muscle and Ciliary Processes, 
together constitute the middle coat of the eye. 
The Choroid coat, about the of an inch in thickness, is both a vas- 
cular and pigmentary membrane; it is of a dark brown color externally, 
and of a deep black internally. 
The outer portion is made up of a rich network of vessels, the branches 
of the ciliary arteries and veins; the inner portion, the pigmentary flayer, 
is a delicate membrane lined by hexagonal cells, containing black pigment. 
The Function of the choroid is mainly to absorb the rays of light which 
pass through the retina, and thus prevent them from interfering with the 
distinctness of vision by being again reflected upon the retina. 
The Iris is a circular, muscular diaphragm, placed in the anterior por- 
tion of the eye, and perforated a little to the nasal side of the centre by a 
circular opening, the pupil; it is attached by its periphery to the point of 
junction of the sclerotic and cornea. It is composed of a connective tissue 
stroma, blood vessels and non-striated muscular fibres, circular and radiat- 120 
HUMAN PHYSIOLOGY. 
ing. The circular fibres surround the margin of the pupil like a sphincter, 
and are controlled by the 3d pair of nerves; the radiating fibres (dilators 
of the pupil) radiate from the centre toward its circumference, and are 
controlled by the sympathetic system of nerves. 
The Ciliary muscle is a greyish circular band, consisting of unstriped 
muscular fibres, about one-eighth of an inch long, running from before 
backward; beneath the radiating fibres are small bands of circular fibres 
running around the eye. It arises from the line of junction of the sclerotic, 
cornea and iris; passing backward it is attached to the outer surface of 
the choroid; it is the principal agent in accommodation, and innervated by 
the 3d pair of nerves. 
The Retina forms the internal coat of the eye; in the fresh state it is a 
delicate, transparent membrane, but soon becomes opaque and a pinkish 
tint; it extends forward almost to the ciliary processes, where it terminates 
in the ora serrata. In the posterior portion of the retina, at a point cor- 
responding to the axis of vision, is a rounded, elevated, yellow spot, the 
limbus luteus, having a central depression, the fovea centralis ; about 
of an inch to the inner side is the point of entrance of the optic nerve, 
where it spreads out to assist in the formation of the retina. The arteria 
centralis retina pierces the optic nerve near the sclerotic, runs forward in 
its substance and is distributed in the retina as far forward as the ciliary 
processes. 
The Retina consists of nine distinct layers, from within outward, sup- 
ported by connective tissue. 1. Membrana limitans interna. 2. Fibres 
of optic nerve. 3. Layers of ganglionic corpuscles. 4. Molecular layer. 
5. Internal granular layer. 6. Molecular layer. 7. External granular 
layer. 8. Membrana limitans externa. 9. Layer of rods and cones. 
In the Fovea centralis, at the point of most distinct vision, all of the layers 
disappear except the layer of rods and cones, which become somewhat 
longer and more slender. 
The Aqueous humor is a clear fluid, alkaline in reaction, occupying the 
anterior chamber of the eye; this chamber is bounded in front by the 
cornea, posteriorly by the iris. 
The Vitreous humor forms about four-fifths of the entire ball. It sup- 
ports the retina, and is excavated anteriorly for the reception of the lens; 
it is transparent, of a jelly-like consistence, and surrounded by a structure- 
less, transparent membrane, the hyaloid membrane. 
The Crystalline lens is situated immediately behind the pupil, in the 
concavity of the vitreous humor. It is inclosed in a highly elastic, trans- 
parent membrane, the capsule. The lens is a transparent, doubly-convex THE SENSE OF SIGHT. 
121 
body, >/j of an inch transversely, of an inch antero-posteriorly; it is 
held in position by the suspensory ligament, formed by a splitting of the 
hyaloid tunic, the external layer of which passes in front of the lens, the 
internal layer behind it. 
Vision. The eye may be regarded as a camera obscura, in which 
images of external objects are thrown upon a screen, the retina, by means 
of a double convex lens. 
The Essential Conditions for proper vision are: I. Certain refract- 
ing media, e. g., cornea, aqueous humor, and crystalline lens, by which 
the rays of light are so disposed as to form an image. 2. A diaphragm, 
the iris, which, by alternately contracting and dilating, increases or dimin- 
ishes the amount of light entering the eye. 3. A sensitive surface, to 
receive the image and transmit the luminous impressions through the optic 
nerve to the brain. 4. A contractile structure, the ciliary muscle, which 
can so manipulate the lens as to enable external objects to be seen at near 
or far distances. 
The Refracting Apparatus, by which parallel rays of light are brought 
to a focus on the retina, consists mainly of the crystalline lens, though 
aided by the cornea and aqueous humor. A ray of light passing through 
the pupil is refracted and concentrated by the lens at a given point pos- 
terior to it. For the correct perception of images of external objects, the 
rays of light must be accurately focused on the retina; in order that this 
may be accomplished, the lens must have a certain density and a proper 
curvature of its surfaces. When the lens is too convex, its refracting 
power is greatly increased, the rays of light are brought to a focus in front 
of the retina, and the visual perception becomes dim and confused. When 
it is too flat, the rays are not focused at all, and the resulting perception is 
the same. 
The Crystalline lens, therefore, produces a distinct perception of the 
outline and form of external objects. 
Action of the Iris. The iris, consisting of contracting and dilating 
fibres, transmits and regulates the quantity of light passing through its 
central aperture, the pupil, which is necessary for distinct vision. 
If the light be too intense or excessive, the circular fibres contract under 
the stimulus of the 3d pair of nerves, and the aperture is diminished in size; 
if the quantity of light be insufficient, the dilating fibres contract under the 
stimulus of the sympathetic, and the pupillary aperture is increased in size. 
The Retina, which is formed partly by the expansion of the optic 
nerve, and partly by new nervous structures, is the membrane which 122 
HUMAN PHYSIOLOGY. 
receives the impressions of light. Its posterior surface, which is in con- 
tact with the choroid, and especially the layer of rods and cones, is the 
sensitive portion, in which the rays of light produce their effects. 
The point of most distinct vision is in the macula lutea, and especially 
in its central depression, the fovea, which corresponds to the central axis 
of the eye; it is situated about of an inch to the outside of the 
entrance of the optic nerve. It is at this point that images of external 
objects are seen most distinctly, while all around it the perceptions are 
more or less obscure; at the macula all the layers disappear except the 
layer of rods and cones. 
Blind Spot. At the point of entrance of the optic nerve is a region in 
which the rays of light make no impression, owing to the absence of the 
proper retinal elements; the fibres of the optic nerve being insensible to 
the action of light. 
The course which a ray of light takes is as follows: After passing 
through the cornea, lens, and vitreous humor and the layers of the retina, 
it is finally arrested by the pigmentary layer of the choroid ; here it excites 
in the layer of rods and cones some physical or chemical change, which 
is then transmitted to the fibres of the optic nerve, and thence to the brain, 
where it is perceived as a sensation of light. 
The Accommodation of the eye to vision for different distances is 
accomplished by a change in the convexities of the lens, caused by the 
action of the ciliary muscle. When the eye is accommodated for vision at 
far distances, the structures are in a passive condition and the lens is flat- 
tened ; when it is adjusted for vision at short distances, the convexities of 
the lens are increased. 
When the Ciliary muscle contracts and draws the choroid coat forward, 
the suspensory ligament is relaxed and the lens becomes more convex, in 
virtue of its own elasticity. 
Optical Defects. Astigmatistn is a condition of the eye which pre- 
vents vertical and horizontal lines from being focused at the same time, 
and is due to a greater curvature of the eye in one direction than another. 
Spherical aberration is a condition in which there is an indistinctness 
of an image from the unequal refraction of the rays of light passing 
through the circumference and the centre of the lens; it is corrected 
mainly by the iris, which cuts off the marginal rays, and only transmits 
those passing through the centre. 
Chromatic aberration, in which the image is surrounded by a colored 
margin, from the decomposition of the rays of light into their elementary THE SENSE OF SIGHT. 
123 
parts, is corrected by the different refractive powers of the transparent 
media in front of the retina. 
Myopia, or short-sightedness, is caused by an abnormal increase in the 
antero-posterior diameter of the eyeball; the lens being too far removed 
from the retina, forms the image in front of it, and the perception becomes 
dim and blurred. Concave glasses correct this defect, by preventing the 
rays from converging too soon. 
Hypermetropic, or long-sightedness, is caused by a shortening of the 
antero-posterior diameter; the lens consequently focuses the rays of light 
behind the retina. Convex glasses correct this defect, by converging the 
rays of light more anteriorly. 
Presbyopia is a loss of the power of accommodation of the eye to near 
objects, and usually occurs between the ages of 40 and 60; it is remedied 
by the use of a convex eye-glass. 
Accessory Structures. The muscles which move the eyeball are 
six in number; the superior and inferior recti, the external and internal 
recti, the superior and inferior oblique muscles. The four recti muscles, 
arising from the apex of the orbit, pass forward and are inserted into the 
sides of the sclerotic coat; the superior and inferior muscles rotate the 
eye around a horizontal axis; the external and internal rotate it around 
a vertical axis. 
The Superior oblique muscle, having the same origin, passes forward to 
the inner and upper angle of the orbital cavity, where its tendon passes 
through a cartilaginous pulley; it is then reflected backward and inserted 
into the sclerotic just behind the transverse diameter. Its function is to 
rotate the eyeball in such a manner as to direct the pupil downward and 
outward. 
The Inferior obliqtie muscle arises at the inner angle of the orbit and 
then passes outward and backward to be inserted into the sclerotic. Its 
function is to rotate the eyeball and direct the pupil upward and outward. 
By the associated action of all these muscles, the eyeball is capable of 
performing all the varied and complex movements necessary for distinct 
vision. 
The Eyelids, bordered with short, stiff hairs, shade the eye and protect 
it from injury. On the posterior surface, just beneath the conjunctiva, are 
the Meibomian glands, which secrete an oily fluid; it covers the edge of 
the lids and prevents the tears from flowing over the cheek. 
The Lachrymal Glands are ovoid in shape and situated at the upper 
and outer part of the orbital cavity ; they open by from six to eight ducts 
at the outer portion of the upper lids. 124 
HUMAN PHYSIOLOGY. 
The Tears, secreted by the lachrymal glands, are distributed over the 
cornea by the lids during the act of winking, and keep it moist and free 
from dust. The excess of tears passes into the lachrymal ducts, which 
begin by two minute orifices, one on each lid, at the inner canthus. They 
conduct the tears into the nasal duct, and so into the nose. 
THE SENSE OF HEARING. 
The Organ of Hearing is situated in the petrous portion of the tem- 
poral bone, and is divided into three portions, viz: the external ear, the 
middle ear and the internal ear. 
The External Ear consists of two portions, the pinna or auricle, and 
the external auditory canal. The former, consisting of cartilage, which is 
irregularly folded and covered by integument, is united to the side of the head 
by ligaments and muscles ; the latter, partly cartilaginous and partly bony, 
is about one and a quarter inches in length ; it runs downward and forward 
from the concha to the middle ear, and is lined by a reflection of the gene- 
ral integument, in which is lodged a number of glands, which secrete the 
cerumen. 
The function of the external ear is to collect the waves of sound coming 
from all directions and to transmit them to the membrana tympani. 
The Middle Ear or Tympanum is an irregularly shaped cavity, 
narrow from side to side, but long in its vertical and antero-posterior 
diameters. 
It is separated from the external ear by the membrana ty?npani, and 
from the internal ear by a second membrana tympani; it communicates 
posteriorly with the mastoid cells, anteriorly with the pharynx, through 
the Eustachian tube. It is lined by mucous membrane, and contains three 
small bones, forming a connected chain running across its cavity. 
The Membrana tympani is a thin, delicate, translucent membrane, cir- 
cular in shape and measuring about two-fifths of an inch in diameter; it is 
received into a delicate ring of bone, which in the adult becomes consoli- 
dated with the temporal bone; it is concave externally and situated ob- 
liquely, inclining at an angle of 45 degrees. 
The membrane consists of three layers; the outer is formed by a reflec- 
tion of the integument lining the external auditory canal; the middle is 
composed of fibrous tissue, and the internal of mucous membrane. 
The Function of the membrana tympani is to receive and transmit the 
waves of sound to the chain of bones; it is capable of being made tense THF. SENSE OF HEARING. 
125 
and lax by the action of the tensor tympani and laxator tympani muscles, 
so as to vibrate in unison with the waves of sound in the external auditory 
meatus. When the membrane is relaxed, its vibrations have a greater 
amplitude, and it appreciates sounds of a low pitch. When it is made 
tense it vibrates less forcibly and appreciates sounds of a high pitch. 
The Chain of bones is formed by the malleus, incus and stapes, united 
together by ligaments. The malleus consists of a head, neck and handle, 
of which the latter is attached to the inner surface of the membrana tym- 
pani. The incus, or anvil bone, articulates with the head of the malleus 
by a capsular joint, and with the stapes by the end of its long process. 
The stapes resembles a stirrup in shape ; it articulates externally with the 
long process of the incus, and internally its oval base is applied to the 
edges of the foramen ovale. 
The Function of the chain of bones is to transmit the waves of sound 
across the tympanum to the internal ear; being surrounded by air, and 
acting as a solid rod, they prevent the vibrations from losing but little in 
intensity. 
The Tensor tympani muscle arises mainly from the cartilaginous part 
of the Eustachian tube ; it then passes backward into the tympanic cavity, 
where it bends at a right angle around a process of bone, and is inserted 
into the root of the handle of the malleus. Its function is to draw the 
handle of the malleus internally, and thus increase the tension of the 
membrana tympani, so as to make it capable of vibrating with sounds of 
greater or less intensity; at the same time it tightens the joints of the 
chain of bones, so that they may the better conduct waves of sound to the 
internal ear, with but a slight loss of intensity. 
The Laxator tympani muscle, arising from the spinous process of the 
sphenoid bone, passes backward through the Glasserian fissure, into the 
.tympanic cavity, and is inserted into the neck of the malleus. Its function 
is to draw the handle of the malleus outward, and so relax the membrana 
tympani, and enables it to receive waves of sound of greater amplitude 
than when it is tense. 
The Stapedius muscle, emerging from the cavity of the pyramid of bone 
projecting from the posterior wall of the tympanum, is inserted into the 
head of the stapes bone. Its function is to draw the stapes backward, 
preventing too great movement of the bone, and at the same time relaxing 
the membrana tympani. 
The Eustachian tube, by means of which the middle ear communicates 
with the pharynx, is partly bony and partly cartilaginous in its structure. 
It is about one and a half inches in length; commencing at its opening in 126 
HUMAN PHYSIOLOGY. 
the pharynx, it passes upward and outward to the spine of the sphenoid 
bone, where it is slightly contracted; it then gradually dilates as it passes 
backward into th'e tympanic cavity. It is lined by mucous membrane, 
which is continued into the middle ear and into the mastoid cells. 
The Eustachian tube permits the passage of air from the pharynx into 
the middle ear; in this way the pressure of the air within and without the 
membrana tympani is equalized, which is one of the essential conditions 
for the reception of sonorous vibrations. 
By closing the mouth and nose, and blowing out the cheeks, air can be 
forced into the middle ear, producing undue pressure, and bulging out of the 
membrana tympani; by making an effort at swallowing, with the mouth 
and nose closed, the air in the tympanum can be rarefied and the tympanic 
membrane will be pressed in. In both such cases the acuteness of hearing 
is very much diminished. 
The pharyngeal orifice of the Eustachian tube is opened by the action of 
certain of the muscles of deglutition, viz: the levator palati, tensor palati, 
and at times the palato-pharyngei muscles. 
The Internal Ear, or Labyrinth, is located in the petrous portion of 
the temporal bone, and consists of an osseous and membranous portion. 
The Osseous Labyrinth is divisible into three parts, viz: the vestibule, 
the semi-circular canals, and the cochlea. 
The Vestibtile is a small, triangular cavity, which communicates with 
the middle ear by the foramen ovale; in the natural condition it is closed 
by the base of the stapes bone. The filaments of the auditory nerve enter 
the vestibule through small foramina in the inner wall, at the fovea hemi- 
spherica. 
The Semi-circular canals are three in number; the superior vertical, 
the inferior vertical and the horizontal, each of which opens into the cavity 
of the vestibule, by two openings, with the exception of the two vertical,* 
which at one extremity open by a common orifice. 
The Cochlea forms the anterior part of the internal ear. It is a gradu- 
ally tapering canal, about one and a half inches in length, which winds 
spirally around a central axis, the modiolus, two and a half times. The 
interior of the cochlea is partly divided into two passages by a thin plate of 
bone, the lamina osseous spiralis, which projects from the central axis two- 
thirds across the canal. These passages are termed the scala vestibuli and 
the scala tympani, from their communication with the vestibule and tym- 
panum. The scala tympani communicates with the middle ear through 
the foramen rotundum, which, in the natural condition, is closed by the THE SENSE OF HEARING. 
127 
second membrana tympani; superiorly they are united by an opening, the 
helicotrema. 
The whole interior of the labyrinth, the vestibule, the semi-circular 
canals, and the scala of the cochlea, contains a clear, limpid fluid, the 
peri-lymph, secreted by the periosteum lining the osseous walls. 
The Membranous Labyrinth corresponds to the osseous labyrinth 
with respect to form, though somewhat smaller in size. 
The Vestibular portion consists of two small sacs, the utricle and saccule. 
The Semi-circular canals communicate with the utricle in the same 
manner as the bony canals communicate with the vestibule. The saccule 
communicates with the membranous cochlea by the canalis reuniens. In 
the interior of the utricle and saccule, at the entrance of the auditory 
nerve, are small masses of carbonate of lime crystals, constituting the 
otoliths. Their function is unknown. 
The Membranous cochlea is a closed tube, commencing by a blind 
extremity at the first turn of the cochlea, and terminating at its apex by a 
blind extremity also. It is situated between the edge of the osseous lamina 
spiralis and the outer wall of the bony cochlea, and follows it in its turns 
around the modiolus. 
A transverse section of the cochlea shows that it is divided into two 
portions by the osseous lamina and the basilar membrane : I. The scala 
vestibuli, bounded by the periosteum and membrane of Reissner. 2. The 
scala tympani, occupying the inferior portion, and bounded above by the 
septum, composed of the osseous lamina and the membrana basilaris. 
The true membranous canal is situated between the membrane of Reiss- 
ner and the basilar membrane. It is triangular in shape, but is partly 
divided into a triangular portion and a quadrilateral portion by the tectorial 
membrane. 
The Organ of Corti is situated in the quadrilateral portion of the canal, 
and consists of pillars or rods, of the consistence of cartilage. They are 
arranged in two rows; one internal, the other external; these rods rest 
upon the basilar membrane; their bases are separated from each other, but 
their upper extremities are united, forming an arcade. In the internal row 
it is estimated there are about 3500, and in the external row about 5200 of 
these rods. 
On the inner side of the internal row is a single layer of elongated hair 
cells; on the outer surface of the external row are three such layers of 
hair cells. Nothing definite is known as to their function. 
The Endolymph occupies the interior of the utricle, saccule, membranous 128 
HUMAN PHYSIOLOGY. 
canals, and bathes the structures in the interior of the membranous cochlea, 
throughout its entire extent. 
The Auditory Nerve at the bottom of the internal auditory meatus 
divides into (i) a vestibular branch, which is distributed to the utricle and 
semi-circular canals; (2) a cochlear branch, which passes into the central 
axis at its base, and ascends to its apex; as it ascends, fibres are given off, 
which pass between the plates of the osseous lamina, to be ultimately con- 
nected with the organ of Corti. 
The Function of the semi-circular canals appears to be to assist in main- 
taining the equilibrium of the body; destruction of the vertical canal is 
followed by an oscillation of the head upward and downward; destruc- 
tion of the horizontal canal is followed by oscillations from left to right. 
When the canals are injured on both sides, the animal loses the power of 
maintaining equilibrium upon making muscular movements. 
Function of the Cochlea. It is regarded as possessing the power of 
appreciating the quality of pitch and the shades of different musical tones. 
The elements of the organ of Corti are analogous, in some respects, to 
a musical instrument, and are supposed, by Helmholtz, to be tuned so as 
to vibrate in unison with the different tones conveyed to the internal ear. 
Summary. The waves of sound are gathered together by the pinna 
and external auditory meatus, and conveyed to the membrana tympani. 
This membrane, made tense or lax by the action of the tensor tympani 
and laxator tympani muscles, is enabled to receive sound waves of either 
a high or low pitch. The vibrations are conducted across the middle ear 
by the chain of bones to the foramen ovale, and by the column of air of 
the tympanum to the foramen rotundum, which is closed by the second 
membrana tympani; the pressure of the air in the tympanum being regu- 
lated by the Eustachian tube. 
The internal ear finally receives the vibrations which excite vibrations 
successively in the perilymph, the walls of the membranous labyrinth, the 
endolymph, and, lastly, the terminal filaments of the auditory nerve, by 
which they are conveyed to the brain. 
VOICE AND SPEECH 
The Larynx is the organ of voice. Speech is a modification of voice, 
and is produced by the teeth and the muscles of the lips and tongue, 
coordinated in their action by stimuli derived from the cerebrum. 
The Structures entering into the formation of the larynx are mainly 
the thyroid, cricoid and arytenoid cartilages; they are so situated and VOICE AND SPEECH. 
129 
united by means of ligaments and muscles as to form a firm cartilaginous 
box. The Larynx is covered externally by fibrous tissue and lined inter- 
nally with mucous membrane. 
The Vocal Cords are four ligamentous bands, running antero-posteri- 
orly across the upper portion of the larynx, and are divided into the two 
superior or false vocal cords, and the two inferior or true vocal cords; 
they are attached anteriorly to the receding angle of the thyroid cartilages 
and posteriorly to the anterior part of the base of the arytenoid cartilages. 
The space between the true vocal cords is the rima glottidis. 
The Muscles which have a direct action upon the movements of the 
vocal cords are nine in number, and take their names from their points of 
origin and insertion, viz : the two crico thyroid, two thyro-arytenoid, two 
posterior crico-arytenoid, two lateral crico-arytenoid, and one arytenoid 
muscles. 
The crico thyroid muscles, by their contraction, render the vocal cords 
more tense by drawing down the anterior portion of the thyroid cartilage 
and approximating it to the cricoid, and at the same time tilting the 
posterior portion of the cricoid and arytenoid cartilages backward. 
The thyro-arytenoid, by their contraction, relax the vocal cords by draw- 
ing the arytenoid cartilage forward and the thyroid backward. 
The posterior crico-arytenoid muscles, by their contraction rotate the 
arytenoid cartilages outward and thus separate the vocal cords and enlarge 
the aperture of the glottis. They principally aid the respiratory move- 
ments during inspiration. 
The lateral crico-arytenoid muscles are antagonistic to the former, and 
by their contraction rotate the arytenoid cartilages so as to approximate 
the vocal cords and constrict the glottis. 
The aiytenoid muscle assists in the closure of the aperture of the glottis. 
The itiferior laryngeal nerve animates all the muscles of the larynx, 
with the exception of the crico thyroid. 
Movements of the Vocal Cords. During respiration the move- 
ments of the vocal cords differ from those occurring during the production 
of voice. 
At each inspiration, the true vocal cords are widely separated, and the 
aperture of the glottis is enlarged by the action of the crico-arytenoid 
muscles, which rotate outward the anterior angle of the base of the aryte- 
noid cartilages; at each expiration the larynx becomes passive; the 
elasticity of the vocal cords returns them to their original position, and the 
air is forced out by the elasticity of the lungs and the walls of the thorax. 130 
HUMAN PHYSIOLOGY. 
Phonation. As soon as phonation is about to be accomplished a marked 
change in the glottis is noticed with the aid of the laryngoscope. The 
true vocal cords suddenly become approximated and are made parallel, 
giving to the glottis the appearance of a narrow slit, the edges of which 
are capable of vibrating accurately and rapidly; at the same time their 
tension is much increased. 
With the vocal cords thus prepared, the expiratory muscles force the 
column of air into the lungs and trachea through the glottis, throwing the 
edges of the cords into vibration. 
The pitch of sounds depends upon the extent to which the vocal cords 
are made tense and the length of the aperture through which the air 
passes. In the production of sounds of a high pitch the tension of the 
vocal cords becomes very marked, and the glottis diminishes in length. 
When grave sounds, having a low pitch, are emitted from the larynx, the 
vocal cords are less tense and their vibrations are large and loose. 
The quality of voice depends upon the length, size and thickness of the 
cords, and the size, form and construction of the trachea, larynx and the 
resonant cavities of the pharynx, nose and mouth. 
The compass of the voice comprehends from two to three octaves. The 
range is different in the two sexes; the lowest note of the male being about 
one octave lower than the lowest note of the female; while the highest 
note of the male is an octave less than the highest of the female. 
The varieties of voices, e. g., bass, baritone, tenor, contralto, mezzo 
soprano and soprano, are due to the length of the vocal cords; being 
longer when the voice has a low pitch, and shorter when it has a high pitch. 
Speech is the faculty of expressing ideas by means of combination of 
sounds, in obedience to the dictates of the cerebrum. 
Articulate sounds may be divided into vowels and consonants. The 
vowel sounds, a, e, i, o, u, are produced in the larynx by the vocal cords. 
The consonantal sounds are produced in the air passages above the larynx 
by an interruption of the current of air by the lips, tongue and teeth ; the 
consonants may be divided into : (i) mutes, b, d, k,p, t, c, g; (2) dentals, 
d, j,s, t, z ; (3) nasals, m, n, ng; (4) labials, b,p,f, v, m; (5) gutturals, 
k, g, c, and g hard; (6) liquids, /, m, n, r. GENERATIVE ORGANS OF THE FEMALE. 
131 
REPRODUCTION. 
Reproduction is the function by which the species is preserved, and is 
accomplished by the organs of generation in the two sexes. 
GENERATIVE ORGANS OF THE FEMALE. 
The Generative Organs of the Female consist of the ovaries, Fal- 
lopian tubes, uterus and vagina. 
The Ovaries are two small, ovoid, flattened bodies, measuring one 
inch and a half in length and three-quarters of an inch in width; they are 
situated in the cavity of the pelvis, and imbedded in the posterior layer of 
the broad ligament; attached to the uterus by a round ligament, and to 
the extremities of the Fallopian tubes by the fimbriae. The ovary consists 
of an external membrane of fibrous tissue, the cortical portion, in which 
are imbedded the Graafian vesicles, and an internal portion, the stroma, 
containing blood vessels. 
The Graafian Vesicles are exceedingly numerous, but situated only 
in the cortical portion. Although the ovary contains the vesicles from 
the period of birth, it is only at the period of puberty that they attain their 
full development. From this time onward to the catamenial period, there 
is a constant growth and maturation of the Graafian vesicles. They consist 
of an external investment, composed of fibrous tissue and blood vessels, in 
the interior of which is a layer of cells, forming the membrana granulosa; 
at its lower portion there is an accumulation of cells, the proligerous disc, 
in which the ovum is contained. The cavity of the vesicle contains a 
slightly-yellowish, alkaline, albuminous fluid. 
The Ovum is a globular body, measuring about the of an inch in 
diameter; it consists of an external investing membrane, the vitelline 
membrane, a central granular substance, the vitellus, or yelk, a nucleus, 
the germinal vesicle, in the interior of which is imbedded the nucleolus, 
or germinal spot. 
The Fallopian Tubes are about four inches in length, and extend 
outward from the upper angles of the uterus, between the folds of the 
broad ligaments, and terminate in a fringed extremity, which is attached 
by one of the fringes to the ovary. They consist of three coats: (i) the 
external, or peritoneal, (2) middle, or muscular, the fibres of which are 
arranged in a circular or logitudinal direction, (3) internal, or mucous, 132 
HUMAN PHYSIOLOGY. 
covered with ciliated epithelial cells, which are always waving from the 
ovary toward the uterus. 
The Uterus is pyriform in shape, and may be divided into a body 
and neck; it measures about three inches in length and two inches in 
breadth in the unimpregnated state. At the lower extremity of the neck 
is the os externum; at the junction of the neck with the body is a constric- 
tion, the os internum. The cavity of the uterus is triangular in shape, the 
walls of which are almost in contact. 
The walls of the uterus are made up of several layers of non-striated 
muscular fibres, covered externally by peritoneum, and lined internally by 
mucous membrane, containing numerous tubular glands, and covered by 
ciliated epithelial cells. 
The Vagina is a membranous canal, from five to six inches in length, 
situated between the rectum and bladder. It extends obliquely upward 
from the surface, almost to the brim of the pelvis, and embraces at its 
upper extremity the neck of the uterus. 
Discharge of the Ovum. As the Graafian vesicle matures, it in- 
creases in size, from an augmentation of its liquid contents, and approaches 
the surface of the ovary, where it forms a projection, measuring from one- 
fourth to one-half an inch in size. The maturation of the vesicle occurs 
periodically, about every twenty eight days, and is attended by the phe- 
nomena of menstruation. During this period of active congestion of the 
reproductive organs the Graafian vesicle ruptures, the ovum and liquid 
contents escape, and are caught by the fimbriated extremity of the Fallo- 
pian tube, which has adapted itself to the posterior surface of the ovary. 
The passage of the ovum through the Fallopian tube into the uterus occu- 
pies from ten to fourteen days, and is accomplished by muscular contraction 
and the action of the ciliated epithelium. 
Menstruation is a periodical discharge of blood from the mucous 
membrane of the uterus, due to a fatty degeneration of the small blood 
vessels. Under the pressure of an increased amount of blood in the repro- 
ductive organs, attending the process of ovulation, the blood vessels 
rupture, and a hemorrhage takes place into the uterine cavity; thence it 
passes into the vagina, where it is kept in a fluid condition from admixture 
with the vaginal mucus. Menstruation lasts from five to six days, and the 
amount of blood discharged averages about five ounces. 
Corpus Luteum. For some time anterior to the rupture of a Graa- 
fian vesicle, it increases in size and becomes vascular; its walls become 
thickened, from the deposition of a reddish-yellow, glutinous substance, a 
product of cell growth from the proper coat of the follicle and the membrana GENERATIVE ORGANS OF THE FEMALE. 
133 
granulosa. After the ovum escapes, there is usually a small effusion of 
blood into the cavity of the follicle, which soon coagulates, loses its coloring 
matter, and acquires the characteristics of fibrin, but it takes no part in the 
formation of the corpus luteum. The walls of the follicle become convo- 
luted, vascular, and undergo hypertrophy, until they occupy the whole of 
the follicular cavity. At its period of fullest development, the corpus 
luteum measures three-fourths of an inch in length and one-half inch in 
depth. In a few weeks the mass loses its red color, and becomes yellow, 
constituting the corpus luteum or yellow body. It then begins to retract, 
and becomes pale; and at the end of two months nothing remains but a 
small cicatrix upon the surface of the ovary. Such are the changes in the 
follicle, if the ovum has not been impregnated. 
The corpus luteum, after impregnation has taken place, undergoes a much 
slower development, becomes larger, and continues during the entire 
period of gestation. The differences between the corpus luteum of the 
unimpregnated and pregnant condition is expressed in the following table 
by Dalton:— 
Corpus Luteum of Menstruation. 
Corpus Luteum of Pregnancy. 
At the end of 
three weeks. 
Three-quarters of an inch in diameter; central clot 
reddish ; convoluted wall pale. 
One month. 
Smaller; convoluted 
wall bright yellow; clot 
still reddish. 
Larger; convoluted wall 
bright yellow; clot still red- 
dish. 
Seven-eighths of an inch 
in diameter; convoluted wall 
bright yellow; clot perfectly 
decolorized. 
Seven-eighths of an inch 
in diameter; clot pale and 
fibrinous; convoluted wall 
dull yellow. 
Still as large as at the end 
of second month; clot fib- 
brinous; _ convoluted wall 
paler. 
Half an inch in diameter; 
central clot converted into a 
radiating cicatrix; external 
wall tolerably thick and 
convoluted, but without any 
bright yellow color. 
Two months. 
Reduced to the condi- 
tion of an insignificant 
cicatrix. 
Four months. 
Absent or unnotice- 
able. 
Six months. 
Absent. 
Nine months. 
Absent. 134 
HUMAN PHYSIOLOGY. 
GENERATIVE ORGANS OF THE MALE. 
The Generative Organs of the Male consist of the testicles, vasa 
deferentia, vesiculae seminales and penis. 
The Testicles, the essential organs of reproduction in the male, are 
two oblong glands, about an inch and a half in length, compressed from 
side to side, and situated in the cavity of the scrotum. 
The proper coat of the testicle, the tunica albuginea, is a white, fibrous 
structure, about the 0f an inch in thickness; after enveloping the testicle, 
it is reflected into its interior at the posterior border, and forms a vertical 
process, the mediastinum testis, from which septa are given off, dividing the 
testicle in lobules. 
The substance of the testicle is made up of the seminiferous tubules, 
which exist to the number of 840; they are exceedingly convoluted, and 
when unraveled, are about 30 inches in length. As they pass toward the 
apices of the lobules they become less convoluted and terminate in from 20 
to 30 straight ducts, the vasa recta, which pass upward through the medias- 
tinum and constitute the rete testis. At the upper part of the mediastinum 
the tubules unite to form from 9 to 30 small ducts, the vasa efferentia, which 
become convoluted, and form the globus major of the epididynnis; the 
continuation of the tubes downward behind the testicle and a second con- 
volution constitutes the body and globus minor. 
The seminal tubule consists of a basement membrane lined by granular 
nucleated epithelium. 
The Vas Deferens, the excretory duct of the testicle, is about two 
feet in length, and may be traced upward from the epididymis to the under 
surface of the base of the bladder, where it unites with the duct of the vesi- 
cula seminalis, to form the ejaculatory duct. 
The Vesiculae Seminales are two lobulated, pyriform bodies, about 
two inches in length, situated on the under surface of the bladder. 
They have an external fibrous coat, a middle muscular coat, and an in- 
ternal mucous coat, covered by epithelium, which secretes a mucous fluid. 
The vesiculae seminales serve as reservoirs, in which the seminal fluid is 
temporarily stored up. 
The Ejaculatory Duct, about of an inch in length, opens into the 
urethra and is formed by the union of the vasa deferentia and the ducts of 
the vesiculae seminales. 
The Prostate Gland surrounds the posterior extremity of the urethra, 
and opens into it by from twenty to thirty openings, the orifices of the pros- DEVELOPMENT OF ACCESSORY STRUCTURES. 
135 
tatic tubules. The gland secretes a fluid which forms part of the semen, 
and assists in maintaining the vitality of the spermatozoa. 
Semen is a complex fluid, made up of the secretions from the testicles, 
the vesiculse seminales, the prostatic and urethral glands. It is greyish- 
white in color, mucilaginous in consistence, of a characteristic odor, and 
somewhat heavier than water. From half a drachm to a drachm is 
ejaculated at each orgasm. 
The Spermatozoa are peculiar anatomical elements, developed within 
the seminal tubules, and possess the power of spontaneous movement. 
The spermatozoa consist of a conoidal head and a long filamentous tail, 
which is in continuous and active motion; as long as they remain in the 
vas deferens they are quiescent, but when free to move in the fluid of the 
vesiculae seminales, become very active. 
Origin. The spermatozoa appear at the age of puberty, and are then 
constantly formed until an advanced age. They are developed from the 
nuclei of large, round cells, contained in the interior of the seminal 
tubules, as many as fifteen to twenty developing in a single cell. 
When the spermatozoa are introduced into the vagina, they pass readily 
into the uterus and through the Fallopian tubes toward the ovaries, where 
they remain and retain their vitality for a period of from 8 to io days. 
Fecundation is the union of the spermatozoa with the ovum during its 
passage toward the uterus, and usually takes place in the Fallopian tube, 
just outside of the womb. After floating around the ovum in an active 
manner, they penetrate the vitelline membrane, pass into the interior of the 
vitellus, where they lose their vitality, and along with the germinal vesicle 
entirely disappear. 
DEVELOPMENT OF ACCESSORY STRUCTURES. 
Segmentation of the Vitellus. After the disappearance of the 
spermatozoa and the germinal vesicle there remains a transparent, granular, 
albuminous substance, in the centre of which a new nucleus soon appears; 
this constitutes the parent cell, and is the first stage in the development of 
the new being. 
Following this, the vitellus undergoes segmentation; a constriction 
appears on the opposite sides of the vitellus, which gradually deepens, 
until the yelk is divided into two segments, each of which has a distinct 
nucleus and nucleolus; these two segments undergo a further division into 
four, the four into eight, the eight into sixteen, and so on, until the entire 136 
HUMAN PHYSIOLOGY. 
vitelius is divided into a great number of cells, each of which contains a 
nucleus and nucleolus. 
The peripheral cells of this “ mulberry mass ” then arrange themselves 
so as to form a membrane, and as they are subjected to mutual pressure, 
assume a polyhedral shape, which gives to the membrane a mosaic appear- 
ance. The central part of the vitelius becomes filled with a clear fluid. 
A secondary membrane shortly appears within the first, and the two 
together constitute the external and internal blastodermic membranes. 
Germinal Area. At about this period there is an accumulation of 
cells at a certain spot upon the surface of the blastodermic membranes, 
which marks the position of the future embryo. This spot, at first circular, 
soon becomes elongated, and forms the primitive trace, around which is a 
clear space, the area pellucida, which is itself surrounded by a darker 
region, the area opaca. 
The primitive trace soon disappears, and the area pellucida becomes 
guitar-shaped; a new groove, the medullary groove, is now formed, which 
develops from before backward, and.becomes the neural canal. 
Blastodermic Membranes. The embryo, at this period, consists of 
three layers, viz: the external and internal blastodermic membranes, and 
a middle membrane formed by a genesis of cells from their internal sur- 
faces. These layers are known as the epiblast, mesoblast and hypoblast. 
The Epiblast gives rise to the central nervous system, the epidermis of 
the skin and its appendages, and the primitive kidneys. 
The Mesoblast gives rise to the dermis, muscles, bones, nerves, blood 
vessels, sympathetic nervous system, connective tissue, the urinary and 
reproductive apparatus and the walls of the alimentary canal. 
The Hypoblast gives rise to the epithelial lining of the alimentary canal 
and its glandular appendages, the liver and pancreas, and the epithelium 
of the respiratory tract. 
Dorsal Laminae. As development advances, the true medullary groove 
deepens, and there arise two longitudinal elevations of the epiblast, the 
dorsal lamina, one on either side of the groove, which grow up, arch 
over and unite so as to form a closed tube, the primitive central nervous 
system. 
The Chorda Dorsalis is a cylindrical rod running almost throughout 
the entire length of the embryo. It is formed by an aggregation of meso- 
blasdc cells, and situated immediately beneath the medullary groove. 
Primitive Vertebrae. On either side of the neural canal the cells of 
the mesoblast undergo a longitudinal thickening, which develops and DEVELOPMENT OF ACCESSORY STRUCTURES. 
137 
extends around the neural canal and the chorda dorsalis, and forms the 
arches and bodies of the vertebrae. They become divided transversely 
into four-sided segments. 
The Mesoblast now separates into two layers; the external, joining with 
the epiblast, forms the somatopleure; the internal, joining with the hypo- 
blast, forms the splanchnopleure ; the space between them constituting the 
pleuro-peritcmeal cavity. 
Visceral Laminae. The walls of the pleuro-peritoneal cavity are 
formed by a downward prolongation of the somatopleure (the visceral 
lamina;),.which, as they extend around in front, pinch off a portion of the 
yelk sac (formed by the splanchnopleure), which becomes the primitive 
alimentary canal; the lower portion, remaining outside of the body cavity, 
forms the umbilical vesicle, which after a time disappears. 
Formation of Fcetal Membranes. The Amnion appears shortly 
after the embryo begins to develop, and is formed by folds of the epiblast 
and external layer of the mesoblast, rising up in front and behind, and on 
each side; these amniotic folds gradually extend over the back of the 
embryo to a certain point, where they coalesce, and enclose a cavity, the 
amniotic cavity. The membranous partition between the folds disappears, 
and the outer layer recedes and becomes blended with the vitelline mem- 
brane, constituting the chorion, the external covering of the embryo. 
The Allantois. As the amnion develops, there grows out from the 
posterior portion of the alimentary canal a pouch, or diverticulum, the 
allantois, which carries blood vessels derived from the intestinal circula- 
tion. As it gradually enlarges, it becomes more vascular, and inserts 
itself between the two layers of the amnion, coming into intimate contact 
with the external layer. Finally, from increased growth, it completely 
surrounds the embryo, and its edges become fused together. 
In the bird, the allantois is a respiratory organ, absorbing oxygen and 
exhaling carbonic acid; it also absorbs nutritious matter from the interior 
of the egg. 
Amniotic fluid. The amnion, when first formed, is in close contact 
with the surface of the ovum; but it soon enlarges, and becomes filled 
with a clear, transparent fluid, containing albumen, glucose, fatty matters, 
urea and inorganic salts. It increases in amount up to the latter period of 
gestation, when it amounts to about two pints. In the space between the 
amnion and allantois is a gelatinous material, which is encroached upon, 
and finally disappears as the amnion and allantois come in contact, at 
about the fifth month. 138 
HUMAN PHYSIOLOGY. 
The Chorion, the external investment of the embryo, is formed by a 
fusion of the original vitelline membrane, the external layer of the amnion, 
and the allantois. The external surface now becomes covered with villous 
processes, which increase in number and size by the continual budding 
and growth of club-shaped processes from the main stem, and give to the 
chorion a shaggy appearance. They consist of a homogeneous granular 
matter, and are penetrated by branches of the blood vessels derived from 
the aorta. 
The presence of villous processes in the uterine cavity is proof positive 
of the previous existence of a foetus. They are characteristic of the 
chorion, and are found under no other circumstances. 
At about the end of the second month the villosities begin to atrophy 
and disappear from the surface of the chorion, with the exception of those 
situated at the points of entrance of the foetal blood vessels, which occupy 
about one-third of its surface, where they continue to grow longer, become 
more vascular, and ultimately assist in the formation of the placenta; the 
remaining two-thirds of the surface loses its villi and blood vessels, and 
becomes a simple membrane. 
The Umbilical Cord connects the foetus with that portion of the 
chorion which forms the foetal side of the placenta. It is a process of the 
allantois, and contains two arteries and a vein, which have a more or less 
spiral direction. It appears at the end of the first month, and gradually 
increases in length, until at the end of gestation it measures about 20 
inches. The cord is also surrounded by a process of the amnion. 
Development of the Decidual Membrane. The interior of the 
uterus is lined by a thin, delicate mucous membrane, in which are im- 
bedded immense numbers of tubules, terminating in blind extremities, the 
uterine tubules. At each period of menstruation the mucous membrane 
becomes thickened and vascular, which condition, however, disappears 
after the usual menstrual discharge. When the ovum becomes fecundated, 
the mucous membrane takes on an increased growth, becomes more hyper- 
trophied and vascular, sends up little processes, or elevations from its sur- 
face, and constitutes the decidua vera. 
As the ovum passes from the Fallopian tube into the interior of the 
uterus, the primitive vitelline membrane, covered with villosities, becomes 
entangled with the processes of the mucous membrane. A portion of the 
decidua vera then grows up on all sides, and encloses the ovum, forming 
the decidua reflexa, while the villous processes of the chorion insert them- 
selves into the uterine tubules, and in the mucous membrane between them. DEVELOPMENT OF ACCESSORY STRUCTURES. 
139 
As development advances the decidua reflexa increases in size, and at 
about the end of the fourth month comes in contact with the decidua vera, 
with which it is ultimately fused. 
The Placenta. Of all the embryonic structures, the placenta is the 
most important. It begins to be formed towards the end of the second 
month, and then increases in size until the end of gestation, when it assumes 
an oval or rounded shape, and measures from 7 to 9 inches in length, 6 to 8 
inches in breadth, and weighs from 15 to 20 ounces. It is most frequently 
situated at the upper and posterior part of the inner surface of the uterus. 
The placenta consists of two portions, a foetal and a maternal. 
The Foetal portion is formed by the villi of the chorion, which, by devel- 
oping, rapidly increase in size and number. They become branched and 
penetrate the uterine tubules, which enlarge and receive their many rami- 
fications. The capillary blood vessels in the interior of the villi also en- 
large and freely anastomose with each other. 
The Maternal portion is formed from that part of the hypertrophied and 
vascular decidual membrane between the ovum and the uterus, the decidua 
serotina. As the placenta increases in size, the maternal blood vessels 
around the tubules become more and more numerous, and gradually fuse 
together, forming great lakes, which constitute sinuses in the walls of the 
uterus. 
As the latter period of gestation approaches, the villi extend deeper into 
the decidua, while the sinuses in the maternal portion become larger and 
extend further into the chorion. Finally, from excessive development of 
the blood vessels, the structures between them disappear, and as their walls 
come in contact, they fuse together, so that, ultimately, the maternal and 
foetal blood are only separated by a thin layer of a homogeneous substance. 
When fully formed, the placenta consists principally of blood vessels inter- 
lacing in every direction. The blood of the mother passes from the ute- 
rine vessels into the lakes surrounding the villi; the blood from the child 
flows from the umbilical arteries into the interior of the villi; but there is 
not at any time an intermingling of blood, the two being separated by a 
delicate membrane formed by a fusion of the walls of the blood vessels 
and the walls of the villi and uterine sinuses. 
The function of the placenta is that of a respiratory organ, permitting 
the oxygen of the maternal blood to pass by osmosis through the delicate 
placental membrane into the blood of the foetus; at the same time permit- 
ting the carbonic acid and other waste products, the result of nutritive 
changes in the fcetus, to pass into the maternal blood, and so to be carried 
to the various eliminating organs. 140 
HUMAN PHYSIOLOGY. 
Through the placenta also passes all the nutritious materials of the 
maternal blood which are essential for the development of the embryo. 
At about the middle of gestation there develops beneath the decidual 
membrane a new mucous membrane, destined to perform the functions of 
the old when it is extruded from the womb, along with the other embryonic 
structures, during parturition. 
DEVELOPMENT OF THE EMBRYO. 
Nervous System. The cerebro-spinal axis is formed within the 
medullary canal by the development of cells from its inner surfaces, which 
as they increase fill up the canal, and there remains only the central canal 
of the cord. The external surface gives rise to the dura mater and pia 
mater. The neural canal thus formed is a tubular membrane; it termi- 
nates posteriorly in an oval dilatation, and anteriorly in a bulbous extremity, 
which soon becomes partially contracted, and forms the anterior, middle 
and posterior cerebral vesicles, from which are ultimately developed the 
cerebrum, the corpora quadrigemina, and medulla oblongata, respectively. 
The anterior vesicle soon subdivides into two secondary vesicles, the 
larger of which becomes the hemispheres, the smaller, the optic thalami; 
the posterior vesicle also divides into two; the anterior becoming the 
cerebellum, the posterior, the pons Varolii and medulla oblongata. 
About the seventh week the straight chain of cerebral vesicles becomes 
curved from behind forward and forms three prominent angles. As devel- 
opment advances, the relative size of the encephalic masses changes. The 
cerebrum developing more rapidly than the posterior portion of the brain, 
soon grows backward and arches over the optic thalami and the tubercula 
quadrigemina; the cerebellum overlaps the medulla oblongata. 
The surface of the cerebral hemispheres is at first smooth, but at about the 
fourth month begins to be marked by the future fissures and convolutions. 
The Eye is formed from a little bud projecting from the side of the 
anterior vesicle. It is at first hollow but becomes lined with nervous 
matter, forming the optic nerve and retina ; the remainder of the cavity is 
occupied by the vitreous body. The anterior portion of the pouch becomes 
invaginated and receives the crystalline lens, which is a product of the 
epiblast, as is also the cornea. The iris appears as a circular membrane 
without a central aperture, about the seventh week; the eyelids are formed 
between the second and third months. 
The Internal Ear is developed from the auditory vesicle, budding 
from the third cerebral vesicle; the membranous vestibule appears first, DEVELOPMENT OF THE EMBRYO. 
141 
and from it diverticula are given off, which become the semi-circular canals 
and cochlea. 
The cavity of the tympanum, the Eustachian tube, and the external 
auditory canal are the remains of the first branchial cleft; the cavity of this 
cleft being subdivided into the tympanum and external auditory meatus by 
the membrana tympani. 
The Skeleton. The chorda dorsalis, the primitive part of the verte- 
bral column, is a cartilaginous rod situated beneath the medullary groove. 
It is a temporary structure, and disappears as the true bony vertebra; 
develop. On either side are the quadrate masses of the mesoblast, the 
primitive vertebrae, which send processes upward and around the medul- 
lary groove, and downward and around the chorda dorsalis, forming in 
these situations the arches and bodies of the future vertebrae. 
More externally the outer layer of the mesoblast and epiblast arch 
downward and forward, forming the ventral laminae, in which develop 
the muscles and bones of the abdominal walls. 
The true cranium is an anterior development of the vertebral column, 
and consists of the occipital, parietal and frontal segments, which corres- 
pond to the three cerebral vesicles. The base of the cranium consists, at 
this period, of a cartilaginous rod on either side of the anterior extremity 
of the chorda dorsalis, in which three centres of ossification appear, the 
bast-occipital, the basi-sphenoidal, and the pre-sphenoidal. They ultimately 
develop into the basilar process of the occipital bone and the body of the 
sphenoid. 
The entire skeleton is at first either membranous or cartilaginous. At 
the beginning of the second month centres of ossification appear in the 
jaws and clavicle; as development advances, the ossific points in all the 
future bones extend, until ossification is completed. 
The limbs develop from four little buds projecting from the sides of the 
embryo, which, as they increase in length, separate into the thigh, leg and 
foot, and the arm, forearm and hand ; the extremities of the limbs undergo 
subdivision, to form the fingers and toes. 
Face and Visceral Arches. In the facial and cervical regions the 
visceral laminae send up three processes, the visceral arches, separated by 
clefts, the visceral clefts. 
The first, or the mandibular arches, unite in the median line to form 
the lower jaw, and superiorly form the malleus. A process jutting from 
its base grows forward, unites with the fronto-nasal process growing from 
above, and forms the upper jaw. When the superior maxillary processes 
fail to unite, there results the cleft palate deformity; if the integument also 142 
HUMAN PHYSIOLOGY. 
fails to unite, there results the hare-lip deformity. The space above the 
mandibular arch becomes the mouth. 
The second arch develops the incus and stapes bones, the styloid process 
and ligament, and the lesser cornu of the hyoid bone. The cleft between 
the first and second arches partially closes up, but there remains an open- 
ing at the side which becomes the Eustachian tube, tympanic cavity, and 
external auditory meatus. 
The third arch develops the body and greater cornu of the hyoid bone. 
Alimentary Canal and its Appendages. The alimentary canal is 
formed by a pinching off of the yelk sac by the visceral plates as they 
grow downward and forward. It consists of three distinct portions, the 
fore gut, the hind gut, and the central part, which communicates for some 
time with the yelk sac. It is at first a straight tube, closed at both 
extremities, lying just beneath the vertebral column. The canal gradu- 
ally increases in length, and becomes more or less convoluted; at its 
anterior portion two pouches appear, which become the cardiac and 
pyloric extremities of the stomach. At about the seventh week the 
inferior extremity of the intestine is brought into communication with the 
exterior, by an opening, the anus. Anteriorly the mouth and pharynx are 
formed by an involution of epiblast, which deepens until it communicates 
with the fore gut. 
The Liver appears as a slight protrusion from the sides of the alimen- 
tary canal, about the end of the first month ; it grows very rapidly, attains 
a large size, and almost fills up the abdominal cavity. The hepatic cells 
are derived from the intestinal epithelium, the vessels and connective 
tissue from the mesoblast. 
The Pancreas is formed by the hypoblastic membrane. It originates in 
two small ducts budding from the duodenum, which divide and subdivide, 
and develop the glandular structure. 
The Lungs are developed from the anterior part of the oesophagus. At 
first a small bud appears, which, as it lengthens, divides into two branches; 
secondaiy and tertiary processes are given off these, which form the bron- 
chial tubes and air cells. The lungs originally extended into the abdomi- 
nal cavity, but became confined to the thorax by the development of the 
diaphragm. 
The Bladder is formed by a dilatation of that portion of the allantois 
remaining within the abdominal cavity. It is at first pear shaped, and 
communicates with the intestine, but later becomes separated, and opens 
exteriorly by the urethra. It is attached to the abdominal walls by a 
rounded cord, the urachus, the remains of a portion of the allantois. DEVELOPMENT OF THE EMBRYO. 
143 
Genito-Urinary Apparatus. The Wolffian bodies appear about the 
thirtieth day, as long hollow tubes running along each side of the primi- 
tive vertebral column. They are temporary structures, and are sometimes 
called the primordial kidneys. The Wolffian bodies consist of tubules 
which run transversely and are lined with epithelium; internally they 
become invaginated to receive tufts of blood vessels; externally they open 
into a common excretory duct, the duct of the Wolffian body, which unites 
with the duct of the opposite body, and empties into the intestinal canal 
at a point opposite the allantois. On the outer side of the Wolffian body 
there appears another duct, the duct of Muller, which also opens into the 
intestine. 
Behind the Wolffian bodies are developed the structures which become 
either the ovaries or testicles. In the development of the female, the 
Wolffian bodies and their ducts disappear; the extremities of the Mullerian 
ducts dilate and form the fimbriated extremity of the Fallopian tubes, while 
the lower portions coalesce to form the body of the uterus and vagina, 
which now separate themselves from the intestine. 
In the development of the male, the Mullerian ducts atrophy, and 
the ducts of the Wolffian body ultimately form the epididymis and vas 
deferens. About the seventh month the testicles begin to descend, 
and by the ninth month have passed through the abdominal ring into 
the scrotum. 
The Kidneys are developed out of the Wolffian bodies. They consist of 
little pyramidal lobules, composed of tubules which open at the apex into 
the pelvis. As they pass outward they become convoluted and cup-shaped 
at their extremities, receive a tuft of blood vessels, and form the Mal- 
pighian bodies. 
The ureters are developed from the kidneys, and pass downward to be 
connected with the bladder. 
The Circulatory Apparatus assumes three different forms at different 
periods of life, all having reference to the manner in which the embryo 
receives nutritious matter and is freed of waste products. 
The Vitelline circulation appears first and absorbs nutritious material 
from the vitellus. It is formed by blood vessels which emerge from the 
body and ramify over a portion of the vitelline membrane, constituting the 
area vasculosa. The heart, lying in the median line, gives off two arches 
which unite to form the abdominal aorta, from which two large arteries 
are given off, passing into the vascular area; the venous blood is returned 
by veins which enter the heart. These vessels are known as the omphalo- 
mesenteric arteries and veins. The vitelline circulation is of short dura- 144 
HUMAN PHYSIOLOGY. 
tion in the mammals, as the supply of nutritious matter in the vitellus soon 
becomes exhausted. 
The Placental circulation becomes established when the blood vessels 
in the allantois enter the villous processes of the chorion and come into 
close relationship with the maternal blood vessels. This circulation lasts 
during the whole of intra-uterine life, but gives way at birth to the adult 
circulation, the change being made possible by the development of the 
circulatory apparatus. 
The Heart appears as a mass of cells coming off from the anterior por- 
tion of the intestine; its central part liquefies, and pulsations soon begin. 
The heart is at first tubular, receiving posteriorly the venous trunks and 
giving off anteriorly the arterial trunks. It soon becomes twisted upon 
itself, so that the two extremities lie upon the same plane. 
The heart now consists of a single auricle and a single ventricle. A 
septum growing from the apex of the ventricle divides it into two cavities, 
a right and a left. The auricles also become partly separated by a septum 
which is perforated by the foramen ovale. The arterial trunk becomes 
separated by a partition, into two canals, which become, ultimately, the 
aorta and pulmonary artery. The auricles are separated from the ventri- 
cles by incomplete septa, through which the blood passes into the ventricles. 
Arteries. The aorta arises from the cephalic extremity of the heart and 
divides into two branches which ascend, one on each side of the intestine, 
and unite posteriorly to form the main aorta; posteriorly to these first 
aortic arches four others are developed, so that there are five altogether 
running along the visceral arches. The two anterior soon disappear. The 
third arch becomes the internal carotid and the external carotid; a part 
of the fourth arch, on the right side, becomes the subclavian artery, and 
the remainder atrophies and disappears, but on the left side it enlarges 
and becomes the permanent aorta; the fifth arch becomes the pulmonary 
artery on the left side. The communication between the pulmonary artery 
and the aorta, the ductus arteriosus, disappears at an early period. 
Veins. The venous system appears first as two short, transverse veins, 
the canals of Cuvier, formed by the union of the vertebral veins and the 
cardinal veins, which empty into the auricle. The inferior vena cava is 
formed as the kidneys develop, by the union of the renal veins, which, in 
a short time, receive branches from the lower extremities. The sub- 
clavian veins join the jugular as the upper extremities develop. The heart 
descends in the thorax, and the canals of Cuvier become oblique; they 
shortly communicate by a transverse duct, which ultimately becomes the 
left innominate vein. The left canal of Cuvier atrophies and becomes a DEVELOPMENT OF THE EMBRYO. 
145 
fibrous cord. A transverse branch now appears, which carries the blood 
from the left cardinal vein into the right, and becomes the vena azygos 
minor; the right cardinal vein becomes the vena azygos major. 
Circulation of Blood in the Foetus. The blood returning from the 
placenta, after having received oxygen, and been freed from carbonic acid, 
is carried by the umbilical vein to the under surface of the liver; here a 
portion of it passes through the ductus venosus into the ascending vena 
cava, while the remainder flows through the liver, and passes into the vena 
cava by the hepatic veins. When the blood is emptied into the right 
auricle, it is directed by the Eustachian valve, through the foramen ovale, 
into the left auricle, thence into the left ventricle, and so into the aorta to 
all parts of the system. The venous blood returning from the head and 
upper extremities is emptied, by the superior vena cava, into the right 
auricle, from which it passes into the right ventricle, and thence into the 
pulmonary artery. Owing to the condition of the lung, only a small por- 
tion flows through the pulmonary capillaries, the greater part passing 
through the ductus arteriosus, which opens into the aorta at a point below 
the origin of the carotid and subclavian arteries. The mixed blood now 
passes down the aorta to supply the lower extremities, but a portion of 
it is directed, by the hypogastric arteries, to the placenta, to be again 
oxygenated. 
At birth, the placental circulation gives way to the circulation of the 
adult. As soon as the child begins to breathe, the lungs expand, blood 
flows freely through the pulmonary capillaries, and the ductus arteriosus 
begins to contract. The foramen ovale closes about the tenth day. The 
umbilical vein, the ductus venosus, and the hypogastric arteries become 
impervious in several days, and ultimately form rounded cords. TABLE OF PHYSIOLOGICAL CONSTANTS. 
Mean height of male, 5 feet inches; of female, 5 feet 2 inches. 
“ weight “ “ 145 pounds; of female, 121 pounds. 
Number of chemical elements in the human body ; from 16 to 18. 
“ “ proximate principles in the human body; about 100. 
Amount of water in the body weighing 145 pounds; 108 pounds. 
“ “ solids in the body weighing 145 pounds; 36 pounds. 
“ “ food required daily; 16 ounces meat, 19 ounces of bread, 
2,% ounces of fat, 52 ounces of water. 
Amount of saliva secreted in 24 hours; about 3*4 lbs. 
Function of saliva; converts starch into glucose. 
Active principle of saliva; ptyalin. 
Amount of gastric juice secreted in 24 hours; from 8 to 14 lbs. 
Functions of gastric juice; converts albumen into albuminose. 
Active principles of gastric juice ; pepsin and hydrochloric acid. 
Duration of digestion ; from 3 to 5 hours. 
Amount of intestinal juice secreted in 24 hours; about 1 lb. 
Function of intestinal juice ; converts starch into glucose. 
Amount of pancreatic juice secreted in 24 hours; about \]/z lbs. 
Active principles of pancreatic juice; pancreatin and trypsin. 
Functions: 
• 1. Emulsifies fats. 
2. Converts albumen into albuminose. 
. 3. “ starch into glucose. 
Amount of bile poured into the intestines daily; about lbs. 
1. Assists in the emulsification of fats. 
2. Stimulates the peristaltic movements. 
3. Prevents putrefactive changes in the food. 
4. Promotes the absorption of the fat. 
Functions: 
Amount of blood in the body; from 16 to 18 lbs. 
Size of red corpuscles; of an inch. 
“ “ white corpuscles; an inch- 
Shape of red corpuscles; circular biconcave disks. 
“ “ white corpuscles ; globular. 
147 148 
TABLE OF PHYSIOLOGICAL CONSTANTS. 
Motor nerve to tongue ; hypoglossal or 12th pair. 
“ “ “ laryngeal muscles; spinal accessory or nth pair. 
Sensory nerve of the face; trifacial or 5th pair. 
“ “ “ “ pharynx; glosso-pharyngeal or 9th pair. 
“ “ “ “ lungs, stomach, etc,; pneumogastric or 10th pair. 
Length of spinal cord; 16 to 18 inches, weight, ozs. 
Point of decussation of motor fibres; at the medulla oblongata. 
“ “ “ “ sensory fibres; throughout the spinal cord. 
Function of antero-lateral columns of spinal cord; transmit motor 
impulses from the brain to the muscles. - 
Functions of the posterior columns; assist in the coordination of 
muscular movements. 
Functions of the medulla oblongata ; controls the functions of insaliva- 
tion, mastication, deglutition, respiration, circulation, etc. 
Functions of the corpora quadrigemina; physical centres for sight. 
“ “ “ corpora striata; centres for motion. 
“ “ “ optic thalami; centres for sensation. 
“ “ “ cerebellum; centre for the coordination of muscular 
movements. 
Function of the cerebrum ; centre for intelligence, reason and will. 
Centre for articulate language; 3d frontal convolution on left side of 
cerebrum. 
Number of coats to the eye; three; 1st, cornea and sclerotic; 2d, choroid ; 
3d, retina. 
Function of iris; regulates the amount of light entering the eye. 
“ “ crystalline lens ; refracts the rays of light so as to form an 
image on the retina. 
Function of retina; receives the impressions of light. 
“ “ membrana tympani; receives and transmits waves of sound 
to internal ear. 
Function of Eustachian tube ; regulates the passage of air into and from 
the middle ear. 
Function of semi-circular canals; assist in maintaining the equipoise 
of the body. 
Function of the cochlea; appreciates the shades and combinations of 
musical tones. 
Size of human ovum; of an inch in diameter. 
“ “ spermatozoa, twists of an inch in length. 
Function of the placenta; acts as a respiratory and digestive organ for 
the foetus. 
Duration of pregnancy; 280 days. TABLE OF PILYSIOLOGICAL CONSTANTS. 
149 
Number of red corpuscles in a cubic millimetre of blood (the cubic 
of an inch); 5,000,000. 
Function of red corpuscles; to carry oxygen from the lungs to the tissues. 
Frequency of the heart’s pulsations per minute; 72, on the average. 
Velocity of the blood movement in the arteries; about 16 inches per 
second. 
Length of time required for the blood to make an entire circuit of the 
vascular system; about 20 seconds. 
Amount of air passing in and out of the lungs at each respiratory act; 
from 20 to 30 cubic inches. 
Amount of air that can be taken into the lungs on a forced inspiration; 
110 cubic inches. 
Amount of reserve air in the lungs after an ordinary expiration; 100 
cubic inches. 
Amount of residual air always remaining in the lungs; about 100 cubic 
inches. 
Vital capacity of the lungs; 230 cubic inches. 
Entire volume of air passing in and out of the lungs in 24 hours; about 
400 cubic feet. 
Composition of the air; nitrogen, 79.19, oxygen, 20.81, per 100 parts. 
Amount of oxygen absorbed in 24 hours; 18 cubic feet. 
Amount of carbonic acid exhaled in 24 hours; 14 cubic feet. 
Temperature of the human body at the surface; F. 
Amount of urine excreted daily; from 40 to 50 ozs. 
“ “ urea “ “ 512 grains. 
Specific gravity of urine; from 1.010 to 1.015. 
Number of spinal nerves; 31 pairs. 
“ “ roots of origin; two; 1st, anterior, motor; 2d, posterior, 
sensory. 
Rate of transmission of nerve force; about 100 feet per second. 
Number of cranial nerves ; 12 pairs. 
' 1. Olfactory, or 1st pair. 
2. Optic, or 2d pair. 
3. Auditory, or 8th pair. 
4. Chorda tympani for anterior % of tongue. 
5. Branches of glosso-pharyngeal or 8th pair, 
for posterior of tongue. 
Nerves of special sense. 
Motor nerves to eyeball and accessory structures; motor oculi, or 3d 
pair ; pathetic, or 4th pair; abducens, or 6th pair. 
Motor nerve to facial muscles; portio dura, facial or 7th pair. TABLE SHOWING RELATION OF WEIGHTS AND 
MEASURES OF THE METRIC SYSTEM TO APPROX- 
IMATE WEIGHTS AND MEASURES OF THE U. S. 
One Myriametre = 10,000 metres = 32800. feet. 
One Kilometre = 1,000 “ = 3280. “ 
One Hectometre = 100 “ = 328.0 “ 
One Decametre = 10 “ = 32.80 “ 
MEASURES OF LENGTH. 
One Metre 
r the ten millionth part of a ' 
quarter of the Meridian of 
[ the Earth j 
— 39-368 inches. 
One Decimetre 
= the tenth part of one metre = 3.936 “ 
One Centimetre 
the one hundredth part of 
one metre 
= -393 ( f ) “ 
One Millimetre 
the one thousandth part of 
one metre 
= -°39 (2V) “ 
OneMyriagramme= 10,000 grammes = pounds Troy. 
One Kilogramme = 1,000 “ = “ “ 
One Hectogramme = ioo “ = ounces “ 
One Decagramme = 10 “ = drachms “ 
WEIGHTS. 
One Gramme = 
f the weight of a cubic centi-' 
\ metre of water at 40 C. 
I5-434 grains. 
One Centigramme = 
One Decigramme = the tenth part of one gramme = 1.543 (ij£) “ 
' the hundredth part of one 1 
gramme J 
•154(34) “ 
One Milligramme = 
r the thousandth part of one 
k gramme 
•OI5 ( A) “ 
MEASURES OF CAPACITY. 
One Myrialitre 
10 cubic Metres or the' 
measure of 10 Milliers of 
water 
2600. gallons. 
One Kilolitre 
1 cubic Metre or the meas-' 
ure of I Millier of water 
260. “ 
One Hectolitre 
100 cubic Decimetres or 
the measure of 1 Quintal 
of water 
26. “ 
10 cubic Decimetres or' 
the measure of 1 Myria- 
gramme of water 
One Decalitre 
1 cubic Decimetre or the 
measure of 1 Kilogramme 
of water 
2.6 “ 
One Litre 
2.1 pints. 
One Decilitre 
100 cubic Centimetres or 
the measure of 1 Hecto- 
gramme of water 
3.3 ounces. 
One Centilitre 
10 cubic Centimetres or' 
the measure of x Deca- 
gramme of water 
1 cubic Centimetre or the 
2.7 drachms. 
One Millilitre 
measure of 1 gramme of 
water 
16.2 minims. 
150 INDEX. 
PAGE 
A BDUCENS NERVE 80 
Aberration, chromatic 122 
spherical 122 
Absorption 28 
by the lacteals 30 
by the blood vessels 31 
of oxygen in respiration 48 
Accommodation of the eye 122 
Adipose tissue, uses of in the body 12 
Adult circulation, establishment of at 
birth. 143 
Air, atmospheric, composition of. 48 
amount exchanged in respira- 
tion 47 
changes in during respiration.. 
Albumen, uses of in the body 12 
Albuminoid substances 19 
Alcohol, action of. 20 
Alimentary principles, classification 
of. 18 
albuminous principles 19 
saccharine principles 19 
oleaginous principles 19 
inorganic principles 19 
Alimentary canal, development of. 142 
Allantois, development and function 
of. 137 
Amnion, formation of. 137 
Animal heat 50 
Anterior columns of spinal cord 92 
Area, germinal 136 
Arteries, properties of. 41 
Asphyxia 49 
Astigmatism 122 
Axis, cerebro-spinal 90 
cylinder of nerves 71 
27 
Bladder, urinary 59 
Blastodermic membranes 136 
Blood 32 
composition of plasma 32 
coagulation of. 36 
coloring matter of. 34 
changes in, during respiration. 49 
circulation of. 37 
rapidity' of flow in arteries 42 
rapidity of flow in capillaries... 43 
pathological conditions of. 37 
corpuscles 33 
origin of. 35 
pressure 41 
Burdach, column of.. 92 
PAGE 
PANALS OF CUVIER 144 
Capillary blood vessels 43 
Capsule, internal 104 
external 103 
Caudate nucleus 103 
Cells, structure of. 14 
■ -■— manifestations of life by 15 
of anterior horns of grey mat- 
ter 92 
Centre for articulate language no 
Cerebrum 106 
fissures and convolutions 107 
functions of 109 
localization of functions no 
motor area of no 
special centres of in 
Cerebellum 105 
forced movements of...... jo6 
Cerebral vesicles of embryo 140 
Chemical composition of human 
body 10 
elements, proximate quantity 
of in body 14 
Chorda dorsalis 136 
tympani nerve, course and 
function of. 83,84 
Chorion 138 
Chyle 31 
Ciliary muscle 120 
Circulation of blood 37 
Claustrum 103 
Cochlea 126 
Columns of spinal cord 92 
Corium 67 
Corpora Wolffiana 143 
quadrigemina 102 
Corpus luteum 132 
striatum 103 
Corti, organ of 104 
Cranial nerves 77 
Crura cerebri 102 
Crystalline lens 120 
■T)ECIDUAL MEMBRANE 138 
Decussation of motor and sen- 
sory fibres 93 
Deglutition 23 
nervous circle of 
Development of accessory structures 
of embryo 135 
Digestion 21 
Ductus arteriosus 145 
venosus 145 
151 152 
INDEX, 
T7 AR 124 
Electrotonus 76 
Embryo, development of. 140 
Endolymph 127 
Epidermis 67 
Epididymis 134 
Epiglottis 24 
Eustachian tube 125 
Excretion 58 
Eye 118 
refracting apparatus of. 121 
blind spot of. 122 
paralysis, symptoms of... 84 
Fallopian tubes 131 
Faeces 28 
Fat, uses of in the body 12 
Female organs of generation 131 
Fissures and convolutions of brain 107 
Food 17 
percentage composition of. 20 
daily amount required 21 
albuminous principles of 19 
saccharine principles of. 19 
oleaginous principles of. 19 
inorganic principles of 19 
Fovea centralis 122 
Galvanic currents, ef- 
fect on nerves. 76 
Ganglia 71 
ophthalmic 112 
Gasserian 81 
spheno-palatine 112 
otic 112 
sub-maxillary.... 112 
semi-lunar T13 
Gases of the intestine 28 
condition of, in blood 49 
Gastric juice 24 
action of. 25 
Generation, male organs of 134 
female organs of. 131 
Globules of the blood 33 
of the lymph 30 
Glomeruli of the kidneys 59 
Glosso-pharyngeal nerve 85 
Glottis, respiratory movements of. 46 
Glycogen 66 
Glycogenic function of liver 66 
Goll, column of. 92 
Graafian follicles 131 
Grey matter of nervous system. 70 
"LJ AIR 68 
-*■ * Haemoglobin 34 
Hearing, sense of. 124 
Heart 37 
valves of, 38 
sounds of. 39 
influence of pneumogastric 
nerve upon 41 
ganglia of. 40 
force exerted by left ventricle...' 39 
PAGE 
Heart, work done by 40 
course of blood through 38 
influence of nervous system 3b 
upon 40 
Hyaloid membrane 120 
Hypermetropia 126 
Hypoglossal nerve 89 
TNCUS BONE 125 
Ingesta and egesta, comparison 
of in 24 hours 21 
Insalivation 22 
nervous circle of. 23 
Inspiration, movements of thorax in.. 46 
Internal capsule 104 
results of injury to 104 
Intestinal juice 26 
Iris 119 
action of. 121 
Island of Reil 108 
excretion of urine by 62 
T ABYRINTH OF INTERNAL 
ear 126 
function of cochlea 128 
function of semicircular canals 128 
Language, articulate, centre for no 
Larynx 128 
Lateral columns of spinal cord 92 
Laws of muscular contraction 77 
Laxator tympani muscle 125 
Lens, crystalline 120 
Lime phosphate 19 
Liver 63 
secretion of bile by 65 
glycogenic function of. 66 
elaboration of blood 65 
cells 63 
Localization of functions in cerebrum no 
Lungs 45 
changes in blood while passing 
through 49 
Lymph 30 
Lymphatic glands 29 
Lymphatic vessels, origin and course 
of. 29 
1WTAMMARY GLANDS 54 
Malleus bone 125 
Mastication 22 
nervous circle of. 22 
muscles of. 22 
Medulla oblongata 98 
properties and functions of. 99 
Membrana basilaris 127 
Membrana tympani 124 
Menstruation 132 
Middle ear 124 
Milk 55 
Motor centres of cerebrum no 
Muscles, properties of. 75 
PAGE 
Myopia 123 INDEX. 
153 
TSJERVE, OLFACTORY 78 
optic 78 
motor oculi 79 
pathetic 80 
trigeminal 8r 
abducens 80 
facial 83 
auditory 84 
glosso-pharyngeal 85 
pneumogastric 86 
spinal accessory 88 
hypoglossal 89 
• cells, structure of. 70 
fibres, terminations of. 73 
force, rate of transmission of... 77 
roots, function of anterior and 
posterior 72 
Nerves, centrifugal and centripetal.... 74 
cranial 77 
decussation of motor and sen- 
sory 93 
vaso-motor 100 
properties and functions of 74 
spinal 72 
Nervous system 70 
white and grey matter of. 70, 71 
cerebro-spinal 70 
sympathetic 70 
Nucleus caudatus 103 
ienticularis 103 
QLFACTORY NERVES 78 
Ophthalmic ganglion 118 
Optic nerves 78 
thalamus 103 
function of. 104 
Organs of Corti 127 
Otic ganglion 11 
Ovaries 131 
Ovum 131 
discharge of from the ovary.... 132 
Oxygen, absorption of by haemoglobin 49 
pACINIAN CORPUSCLES 73 
Patheticus nerve 80 
Peptones 25 
Perilymph 127 
Perspiration 69 
Petrosal nerves, large and small 83, 84 
Phonation 130 
Physiology, definition of 9 
Placenta, formation and function of... 139 
Pneumogastric nerve 86 
Pons varolii iox 
Portal vein 64 
Posterior columns of spinal cord 92 
functions of. 95 
Prehension 21 
Presbyopia 126 
Pressure of blood in arteries 41 
Proximate principles 11 
inorganic 11 
organic, non-nitrogenized 11 
organic, nitrogenized 12 
of waste 14 
PAGE 
Proximate quantity of chemical ele- 
ments in body 14 
Ptyalin 23 
Pulse 42 
Pyramidal tracts 92 
DED CORPUSCLES OF 
blood 34 
Reflex movements of spinal cord 96 
action, laws of. 96 
Reproduction 131 
Respiration 44 
movements of 46 
nervous mechanism of. 47 
types of. 47 
nervous circle of 101 
Retina 120 
OALIVA 22 
Sebaceous glands. 68 
Secretion 52 
Semi-circular canals 127 
Semen 133 
Sight, sense of. 118 
Skin 67 
-relative sensibility of. 115 
appendages of. 68 
Smell, sense of. 117 
Sounds of heart 39 
Spermatozoa 135 
Spheno-palatine ganglion 142 
Spinal accessory nerve 88 
Spinal cord 91 
membranes of. 90 
structure of white matter 92 
structure of grey matter 92 
properties of. 94 
function of as a conductor 94 
as an independent centre 95 
decussation of motor and sen- 
sory fibres 93 
reflex action of. 96 
special centres of. 97 
paralysis, from disease of. 99 
nerves, origin of. 93 
course of anterior and posterior 
roots of. 93 
Spleen 57 
Stapes bone 125 
Starvation, phenomena of. 17 
Stomach 74 
Structural composition of the body.... 14 
Submaxillary ganglion 112 
Sugar, uses of in the body 12 
Supra-renal capsules 57 
Sudoriparous glands 68 
Sympathetic nervous system m 
properties and functions of. 113 
npASTE, SENSE OF 116 
Teeth 22 
Tensor tympani muscle 125 
Testicles 134 
Thoracic duct 29 
Thorax, enlargement of in inspiration 46 
PACK 154 
INDEX. 
Tissues, classification of. 16 
Tongue 116 
motor nerve of. 117 
sensory nerve of. 117 
Touch, sense of. 114 
Tiirck column 92 
UMBILICAL CORD 138 
Urea 62 
Uric acid 62 
Urine 60 
composition of. 61 
average quantity of constitu- 
ents secreted daily 61 
Urination, nervous mechanism of.. ... 60 
Uterus 132 
PAGE 
yAPOR, WATERY, OF 
• breath 49 
Vascular glands . 56 
system, development of. 144 
Vaso-motor nerves, origin of. 100 
Veins 43 
Vesiculse seminales 134 
Vision, psychical centre for in 
physical centre for 103 
Vital capacity of lungs 48 
Vocal cords 129 
Voice 128 
TX7ATER, AMOUNT OF IN 
®v body 14 
Wolffian bodies 143 
PAGE CATALOGUE No. 7. 
A CATALOGUE 
OF 
Books for Students; 
INCLUDING A FULL LIST OF 
The ? Quiz- Compends ? 
AND MANY OF 
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Students’ Manuals and Text-Books 
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No. 1. ANATOMY. (Illustrated.) 
THIRD REVISED EDITION. 
A Compend of Human Anatomy. By Samuel O. L. 
Potter, m.a., m.d., U. S. Army. With 63 Illustrations. 
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Nos. 2 and 3. PRACTICE. 
A Compend of the Practice of Medicine, especially 
adapted to the use of Students. By Dan’l E. Hughes, 
m.d., Demonstrator of Clinical Medicine in Jefferson 
Medical College, Philadelphia. In two parts. 
Part I.—Continued, Eruptive, and Periodical Fevers, 
Diseases of the Stomach, Intestines, Peritoneum, Biliary 
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Hall, Professor of Practice, St. Louis College of Physicians and 
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A Compend of Human Physiology, adapted to the use 
of Students. By Albert P. Brubaker, m.d., De- 
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No. 5. OBSTETRICS. 
A Compend of Obstetrics. For Physicians and Students. 
By Henry G. Landis, m.d., Professor of Obstetrics 
and Diseases of Women, in Starling Medical College, 
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A Compend on Materia Medica and Therapeutics, with 
especial reference to the Physiological Actions of 
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A Compend of Chemistry. By G. Mason Ward, m.d., 
Demonstrator of Chemistry in Jefferson Medical Col- 
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various Analytical Tables. 
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No. 8. VISCERAL ANATOMY. 
A Compend of Visceral Anatomy. By Samuel O. L. 
Potter, m.a., m.d., U. S. Army. With 40 Illustrations. 
*** This is the only Compend that contains full descriptions of the 
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A Compend of Surgery; including Fractures, Wounds, 
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A Compend of Organic Chemistry, including Medical 
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Ptomaines. Animal Chemistry. Nutrition and Assimilation. 
Food, Water and Air. Urinary Analysis. Index. 
The Essentials of Pathology. 
BY D. TOD GILLIAM, M.D., 
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A POCKET-BOOK OF 
PHYSICAL DIAGNOSIS 
OF THE 
Diseases of ihe Heart and Lungs. 
A MANUAL FOR STUDENTS AND PHYSICIANS. 
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INDEX OF DISEASES; 
WITH TREATMENT AND FORMULAE. 
By THOS. HAWKES TANNER, M.D. 
REVISED AND ENLARGED BY DR. BROADBENT. 
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RICHTER’S CHEMISTRY, 
A TEXT-BOOK of INORGANIC CHEMISTRY for STUDENTS. 
By PROF. VICTOR von RICHTER, 
University of Breslau, 
Authorized Translation from the Third German Edition, 
By EDGAR F. SMITH, M.A., Ph.D., 
Professor of Chemistry in Wittenberg College, Springfield, Ohio; 
formerly in the Laboratories of the University of Pennsyl- 
vania; Member of the Chemical Society of Berlin. 
12mo. 89 Wood-cuts and Col. Lithographic Plate of Spectra. $2.00 
In the chemical text-books of the present day, one of the striking 
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those experienced in teaching the subject know only too well the 
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and their intimate relation clearly shown. From careful observa- 
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scriptions of the various inorganic substances are full, and embody 
the results of the latest discoveries. 
In preparation, “ORGANIC CHEMISTRY,” By the same 
author. Translated. BYFORD, DISEASES OF WOMEN. 
NEW REVISED EDITION. 
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DAY ON CHILDREN. Second Edition. 
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By Morell Mackenzie, m.d., Senior Physician to the 
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300 CAREFULLY PRINTED ILLUSTRATIONS. 
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Boston. 
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the University Medical College.”—Prof. Lewis A. Stimpson, 
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ology.”— Prof. L. B. how, Dartmouth Med. College, Hanover, 
N. H. 
RINDFLEISCH. 
THE ELEMENTS OF PATHOLOGY. 
TRANSLATED BY WM. H. MERCUR, M.D. 
REVISED AND EDITED BY PROF. JAS. TYSON, 
Of the University of Pennsylvania. 
OCTAVO. CLOTH. NEARLY READY. 
*** It is the object of Prof. Rindfleisch to present in 
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of Pathology A large number of the general processes 
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tial to the practical physician, are plainly presented. 
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tion of the author, his thorough familiarity with, and his 
method of treating the subject, make this most recent work 
peculiarly useful to the student, as well as to the prac- 
ticing physician who wishes to brush up his pathology. Richters Inorganic Chemistry. 
JUST PUBLISHED. 
A Text-Book for Students, in which the Theory and Facts of the Science of 
Chemistry are brought together and their intimate relations clearly shown. 
A TEXT-BOOK OF INORGANIC CHEMISTRY. By Prof. Victor 
von Richter, University of Breslau. Authorized Translation from the 
Third German Edition, by Edgar F. Smith, m.a., ph.d., Member of the 
Chemical Society of Berlin, Prof, of Chemistry, Wittenberg College, 
formerly in the Laboratories of the University of Pennsylvania. 89 
wood-cuts and colored plate of Spectra. i2mo. 424 pages. 
FROM THE THIRD EDITION. 
Price, Cloth, $2.00. 
RECOMMENDATIONS. 
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lator as Prof. Smith. 
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of students, is in this book very clearly explained, and the explanations are so well distributed 
through the book that students are brought easily from the simplest to the most difficult 
problems. 
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John Marshall, M.D., Nat. Sc.D. (Tubingen), Demonstrator of Chemistry in the Univer- 
sity of Pennsylvania, Medical Department. 
&gpTn Press, ORGANIC CHEMISTRY, by the same Author and Translator. 
MARSHALL & SMITH’S 
CHEMICAL ANALYSIS of URINE. 
ILLUSTRATED. 
As none of the existing books on Urine Analysis deal sufficiently with the chemi- 
cal side of the subject, this little handbook has been prepared to fill the gap 
THE CHEMICAL ANALYSIS OF THE URINE. Based in part on 
Casselmann’s Analyse des Harns. By John Marshall, m.d., 
Demonstrator of Chemistry, Medical Department, University of Pennsyl- 
vania, and Edgar F. Smith, ph.d., Professor of Chemistry, Wittenberg 
College. Illustrated, i2mo. 
Price, Cloth, $1.00. 
RECOMMENDATIONS. 
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trustworthy methods of detection of the chief normal as well as the abnormal constituents of 
the urine; and the accompaning calculations add greatly to its value as a handy reference 
book.”—Prof. Sam’ l P. Sadtler, Professor of General and Organic Chemistry, University 
of Pennsyhiania, and Prof, of Chemistry, Philadelphia College of Pharmacy. 
“ The illustrations are well done, and in point of clearness of expression and accuracy of 
statement, the book leaves little to be desired.”—N. Y. Medical Journal. 
P. BLAKI8TON, SON & CO., Medical Publishers and Booksellers, 
1012 WALNUT STREET, PHILADELPHIA. BIDDLE’S 
Materia Medica. 
NINTH REVISED EDITION. 
fContaini all Changsa in the New Pharmacopoeia.) 
Recommended as a Text-book at Yale College, University of Michigan, 
College of Physicians and Surgeons, Baltimore, Baltimore Medical 
College, Louisville Medical College, and a number of other 
Colleges throughout the United States. 
BIDDLE’S MATERIA MEDICA. For the Use of Students 
and Physicians. By the late Prof. John B. Biddle, m.d., 
Professor of Materia Medica in Jefferson Medical College, 
Philadelphia. The Ninth Edition, thoroughly revised, and 
in many parts rewritten, by his son, Clement Biddle, m.d., 
Assistant Surgeon, U. S. Navy, assisted by Henry Morris, 
m.d. Containing all the additions and changes made in the 
last revision of the United States Pharmacopceia. Octavo. 
Ready. 
Bound, in Cloth. Price $4.00; Leather, $4.75. 
.RECOMMENDATIONS. 
“ It will be found a useful handbook by students, especially, who may be 
under the instruction of its able and accomplished author.”—American Med- 
ical Journal. 
“ In short, it is just the work for a student, embracing as it does what will 
be discussed in a course of lectures on materia medica.”—Cincinnati Medical 
News. 
“ In truth, the work is well adapted to the wants of students.”—The Clinic. 
“ Nothing has escaped the writer’s scan. All the new remedies against 
disease are duly and judiciously noted. Students will certainly appreciate its 
shapely form, grace of manner, and general multum in parvo style.”—Ameri- 
can Practitioner. 
“ Biddle’s ‘ Materia Medica ’ is well known to the profession, being a stand- 
ard text-book in several leading colleges.”—New York Medical Journal. 
“ It contains, in a condensed form, all that is valuable in materia medica, 
and furnishes the medical student with a complete manual on this subject.”— 
Canada Lancet. 
“ The necessity for a new edition of this work in so short a time is the best 
proof of the value in which it is held by the profession.”—Medical and Surg- 
ical Reporter., 
“ The standard ‘ Materia Medica’ with a large number of medical students 
is Biddle’s.”—Buffalo Medical and Surgical Journal. 
“The larger works usually recommended as text-books in our medical 
schools are too voluminous for convenient use. This work will be found to 
contain in a condensed form all that is most valuable, and will supply students 
with a reliable guide.”—Chicago Medical Journal. 
This Ninth Edition contains all the additions and changes in the U. S. 
Pharmacopceia, Sixth Revision. 
P. BLAKHS TON, SON & OO., Publishers and Booksellers, 
1012 WALNUT STREET, PHILADELPHIA. MEIGS AND PEPPER 
Diseases of Children. 
Recommended at thirty-five of the principal Medical Colleges in the United 
States, including Bellevue Hospital, New York, University of 
Pennsylvania, and Long Island College Hospital. 
SEVENTH REVISED EDITION. 
A PRACTICAL TREATISE ON THE DISEASES OF 
CHILDREN. By J. Forsyth Meigs, m.d., one of the 
Physicians to the Pennsylvania Hospital, Consulting Physician 
to the Children’s Hospital, etc., and William Pepper, m.d., 
Professor of Clinical Medicine, University of Pennsylvania, 
Provost and ex-officio President of the Faculty, Physician to 
the Philadelphia Hospital, Fellow of the College of Physi- 
cians, etc. The Seventh revised and improved edition. In 
one volume, of over 1000 royal octavo pages. 
Price, in Cloth, $6.00; Leather, $7.00 
The rapid sale of six large editions of Drs. Meigs and Pepper’s work on 
Children, and the demand for the new edition now ready, is sufficient evidence 
of its great popularity. The large practice, of many years’ standing, of the 
authors imparts to it a value unequaled, probably, by any other book on the 
subject now before the profession. 
The whole work has been again subjected to an entire and thorough 
revision. Some articles have been rewritten; many additions made; and great 
care observed by the authors that it should be most effectually brought up to 
the light, pathological and therapeutical, of the present day. 
The publishers have very many favorable notices of the previous editions, 
received from numerous sources, foreign and domestic. They append a few 
from leading journals, which will give a general idea of the value placed upon 
it, both as a text book for the student and a work of reference for the General 
Practitioner. 
JBBCOMMENDATIONS. 
“ It is the most complete work upon the subject in our language. It contains at once the 
results of personal and the experience of others ; its quotations from the most recent authori- 
ties, both at home and abroad, are ample, and we think the authors deserve congratulations 
for having produced a book unequaled for the use of the student, and indispensable as a 
work of reference for the practitioner.”—American Medical Journal. 
“ But as a scientific guide in the diagnosis and treatment of the diseases of children, we 
do not hesitate to say that we have seldom met with a text-book so complete, so just, and so 
readable, as the one before us, which in its new form cannot fail to make friends wherever it 
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appreciated.”—American Journal of Obstetrics. 
" It is only three years since we had the pleasure of recommending the Fifth Edition of 
this excellent work. With the recent additions, it may safely be pronounced one of the best 
and most comprehensive works on diseases of children of which the American practitioner 
can avail himself, for study or reference.”—New York Medical Journal. 
P. BLAKISTON, SON &, CO., Publishers and Booksellers 
1012 WALNUT STREET, PHILADELPHIA